JPS59228209A - Automatic focus detector - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an automatic focus detection device that automatically detects the focus of an imaging optical system.

The applicant repeatedly detects the focusing state of an imaging optical system in order to form an image of the object on a predetermined focal plane (for example, a film plane) according to the distance of the object, and the imaging optical system As an improvement of the automatic focus detection device that determines the in-focus state, after the imaging optical system is in the focused state, the range (dead zone region) that is considered to be in the focused state is expanded, and the imaging optical system is in the in-focus state. Despite this, in an application filed on the same date as the present application, we proposed a method to stabilize the operation of the above-mentioned device by preventing erroneous detection of an out-of-focus state due to the influence of noise, etc. ing.

However, widening the dead zone region stabilizes the operation of the apparatus, but at the same time reduces the accuracy of focus detection. In other words, when the out-of-focus state actually occurs, rather than due to the influence of noise etc., it would have been detected as out-of-focus quickly if the dead zone area was originally narrow, but it becomes out of focus due to the widening of the dead zone area as described above. If the in-focus state cannot be detected, even if the in-focus state can be detected, there will be a delay in operation, which is a serious problem for automatic focus detection devices for devices such as cameras, where a momentary photo opportunity is critical.

The present invention was developed in view of the following circumstances. After the dead zone area is widened when the in-focus state is reached, the dead zone area is narrowed again when the in-focus state is detected multiple times in succession. The present invention aims to provide an automatic focus detection device that achieves both stabilization of operation and maintenance of accuracy. The gist of the system is that in order to detect the focus of the imaging optical system, it has a first focus detection system with a narrow focusing range and a second focus detection system with a wide focusing range; When the focus state is determined by the focus detection system, the next focus detection is performed by the second focus detection system, and when the focus state is determined multiple times in succession by the second focus detection system. This is an automatic focus detection device characterized in that the next focus detection is performed by a first focus detection system.

Embodiments of the present invention will be described below with reference to the drawings.

Figure 1 shows an automatic focus detection device (hereinafter referred to as AF rack device)
This diagram schematically shows the overall configuration of the . In the figure, 1 is the imaging lens group involved in focusing operation in the photographing lens as an imaging optical system, and 2 is the imaging surface of the image sensor, and here the imaging surface of the imaging tube is shown. , an imaging plane of a solid-state sensor, or a film plane. Reference numeral 3 denotes a light projecting element for projecting a light beam onto the field of view (generally the area to be measured), and is composed of a laser diode, an infrared light emitting diode, or the like. Reference numeral 4 denotes a light projecting lens, which forms a light spot image of the light projecting element 3 on a subject 5 (generally an object to be measured). Reference numeral 6 denotes a light-receiving element, which can output an output divided into two light-sensitive areas 6A and 6B, where area 6A is on the light-emitting element 3 side and area 6B is on the light-emitting element 3 side.
is arranged so that it is on the opposite side. The light receiving element 6 is composed of, for example, a two-area PTN photodiode or a charge-coupled device. PL is a visible light cut filter that allows as much light as possible from the infrared light emitting diode 3 to pass through.
This is to suppress external light components.

Reference numeral 7 denotes a light-receiving lens, which forms a projected light spot image on the subject 5 onto the light-receiving element 6 . Reference numeral 8 denotes a motor for driving the photographing optical system, which drives the lens group 1 and the light emitting element 3 via a cam or the like.
and the light receiving element 6. Reference numeral 9 denotes an automatic focus detection circuit (hereinafter referred to as an AP circuit) which moves the motor 7 in accordance with the direction of the light receiving element to move the lens group 1 to the in-focus position.

Next, to explain the operation of the apparatus shown in Fig. 1, when the subject 5 is at a distance l from the image forming plane, the reflected light of the projected spot image P is reflected on the optical sensor as shown in Fig. 2 (a). , two areas 6
Suppose that the same amount of light is received as A and 6B. In this case, in the light receiving element 6, the difference 7-VB between the integral value VA of the output from the area 6A and the integral value VB of the output from the area 6B becomes 0. In terms of the optical path, the light emitted from the light projecting element 3 passes through the entire optical path, hits the subject, is diffusely reflected, and further passes through the optical path to form an image on the light receiving element 6. Therefore, assume that the lens group 1 is at the in-focus position at this time and the subject 5 has moved to a distance of 11. Then, as a matter of course, the focus position of lens group 1 shifts to the rear, resulting in a rear bin state. On the other hand, assuming that the light projecting element 5 and the light receiving element 6 remain in the same position, the light path hits the subject from bl and is diffusely reflected, passing through light paths a and f and reaching the light receiving element 6.
However, as shown in FIG. 2 (1), the image formation position is largely shifted toward the region 6B, and the above-mentioned VA-VB does not become 0.

Therefore, this amount of shift is calculated as the amount of movement of the subject 5, that is, Jt −1
, the lens group 1 is moved to the in-focus position. That is, the AF' circuit 9 rotates the motor 8 in the forward or reverse direction according to the sign of VA-VB (including its magnitude in some cases), and in turn rotates the light emitting element 3, the light receiving element 6, and the lens group 1 with the cam. VA-7B=Q, that is, when the projected spot image reaches the intermediate position between areas 6A and 6B on the light-receiving element 6, the image of the object at a distance of 4 will be moved in conjunction with the imaging plane 2.
to form a sharp image at the top. As a result, the light projecting element 3 moves to the 3' position, the light receiving element 6 moves the boundary line between the areas 5A and 5B to the 6' position, and the lens group 1 moves to the 1' position. In this case, the projection optical path S1,
The reflected optical paths are indicated by a and F. On the other hand, subject 5 is 4. When the lens group 1 and the like move to the position shown in FIG.

The projection optical path in this case is indicated by C1 and the reflected optical path at.

3 to 6 show other embodiments of an automatic focus detection device that performs distance measurement based on the same principle as the device shown in FIG. It's different. Hereinafter, the same members as those in the apparatus shown in FIG. 1 will be given the same numbers and will be briefly described.

FIG. 6 shows a type of so-called half-TTL distance measurement in which a light spot image is projected from a light projecting element through a photographing lens, and the light is received by a light receiving element provided outside the camera. Reference numeral 10 is a half mirror having a reflective surface 10a configured as a cold mirror, and power is distributed between the lens group 1 of the photographing lens, which moves particularly for focus adjustment, and the imaging plane 2. 4' is a light projecting lens, and 3 is a light projecting element. It is desirable that the light projecting element 3 is arranged at a position optically conjugate with the image forming surface 2. The movement of the photographing lens 1 is performed in mechanical interlock with the light receiving element 6.

FIG. 4 shows a so-called TTL distance measuring type automatic focus detection device in which both light is projected from a light projecting element and light is received by a light receiving element through a photographing lens. 10' is a half mirror placed at the same position as 10 in FIG. The projected light spot image is configured to pass near the outer periphery of the pupil of the photographing lens 1. 7' is a light-receiving lens; 6 is a light-receiving element disposed at a position optically conjugate with the imaging surface 2 of the photographic lens 1; the light beam is near the outer periphery of the knee of the photographic lens 1;
It is configured to pass through a position separated from the projected light beam.

Note that the light projecting element 3 and the light receiving element 6 are fixedly installed and are not mechanically interlocked with the photographic lens.

FIG. 5 is a modification of FIG. 4, in which the projected light flux is aligned with the photographing optical axis.

Figure 6 shows an automatic focus detection device that uses the same light projecting system as in Figure 3 and uses the image pickup element 13 provided on the focal plane as a light receiving element for adjusting five focal points and for imaging. It is. The image signal received by the image sensor 13 is divided by the distribution circuit 11 into the fiAF circuit 7 and the image sensor 12 .

FIG. 7 shows the photosensitive surface of the image sensor 13 of the device shown in FIG.
The signals from the two zones B are sent to the AP via the distribution circuit 11.
'Send to circuit 7. Further, in the case of the one shown in FIG. 7, it is necessary to devise a method to allow infrared light to pass through the image pickup element 15 during distance measurement, and to remove the infrared light during image capture.

By the way, among the above embodiments, in the type shown in Fig. ii, the light emitting lens 4 and the light receiving lens 7 are located outside the photographing lens 1, so it is possible to increase the size of the light emitting/light receiving lens 4.7. Although it has advantages in terms of reach and distance, it has the disadvantage that it cannot be assembled as a whole in a compact manner. On the other hand, the type shown in FIG. 3 has advantages and disadvantages opposite to those of the type shown in FIG. Furthermore, since there is no need for mechanical interlocking between the imaging lens 1 and the projection/reception system, which requires precision, there is also the advantage that the structure is simple. The type shown in FIG. 3 has properties intermediate between those of FIGS. 1 and 4.

The type shown in Figure 4 has a shorter baseline length of the light emitting/receiving system than the one shown in Figure 3, which is disadvantageous in terms of distance measurement accuracy, but the second
Like the one shown in the figure, it has the advantage that the projected light beam remains at the center of the finder even when out of focus. Incidentally, in all of the above-mentioned types, the light spot image formed on the subject 5 by the light projecting element 3 is formed on the optical axis of the photographing lens when in focus. In other words, the distance measurement zone of any of the above devices is
The center of the viewfinder is an automatic focus detection device with no balaxix.

Also, in the device shown in FIG. 6, the light receiving aperture of the light receiving element 13 is approximately equal to the F number of the photographing lens, compared to other types of devices.

Generally, the area of the light-receiving aperture can be increased, which is advantageous in terms of reach distance. Furthermore, in the apparatus shown in FIG.
The signal from is distributed to the AP circuit 9 and the imaging circuit 12,
Since it is practical to distribute this information in a time-division manner, this type of system is suitable for systems such as still video cameras that complete distance measurement prior to photographing.

Next, the configuration of the electric circuit in the above device will be explained based on FIG. 8. As described above, the reflected light projected spot image received by 6B in each region 6 of the light receiving element 6 is supplied as photoelectrically converted optical information to the amplifier circuits IG1a and 101bVC, where it is sufficiently amplified. At this time, the amplifiers 101a and 101b
has sufficient amplification for the modulation frequency of the infrared light that becomes the projected spot image, and has frequency characteristics that minimizes the amplification for the frequency of modulated light from unnecessary sunlight or commercial power. circuit is preferred. The output of this amplifier is applied to synchronous detection circuits 102a and 102b for synchronous detection. At this time, the synchronization signal has the same frequency as the light emission drive signal of the light projecting element 3, and maintains a constant phase relationship. The output of this synchronous detection circuit is integrated by an integrating circuit 103a, 1031), and increases moment by moment at an increasing rate proportional to the signal intensity of the reflected light spot image. The integrated voltages vA and vB obtained independently from the integrating circuits 103a and 103'o through the above signal processing are processed and determined by the arithmetic circuit described below and converted into several bits of digital information.

That is, the integrated voltage vA+vB becomes a difference signal VA-VB by the subtracter 104 on the one hand, and becomes a sum signal VA+VB by the adder 105 on the other hand. The difference signal YA-VB is applied to an absolute value circuit 106 to obtain blVA-Vnl. This value 1vperson-VBl is compared with a comparison value VD in a comparator 107 serving as a comparison means, and the magnitude relationship thereof is output. -10,000, the sum signal vA + VB is a comparison value v in comparators 108 and 109 as level detection means, respectively.
It is compared with T, +*vH, and the respective magnitude relationships are output. Further, in the comparator 110, the integrated voltages VA and VB are directly compared in terms of magnitude. 4 obtained from the above
digital information, i.e., comparators 107, 108, 1
The outputs of 09 and 110 are sent to the order control circuit 1 as a determining means.
11 to determine the operation of the entire system.

Reference numeral 112 denotes a light emission drive circuit, which supplies current to the light projecting element 3 in synchronization with a synchronization signal from the control circuit 111, and controls the light emission of the light projecting element 20.

A motor drive circuit 113 controls the rotational direction and rotational speed of the photographing optical system drive motor 8 based on signals from the control circuit 111.

FIG. 9 shows a further embodiment of the circuit configuration shown in FIG. 8.

FIG. 9 shows the part (A) of the circuit in FIG.
2a, 202m)? This gives it bypass characteristics. In the energy of the infrared light actually projected from the light projecting element 3, the external light component can have a significantly larger value than the energy returning to the light receiving element 6. The visible light cut filter FL and this circuit have a relatively effective effect of suppressing external light components, and depending on the settings, can be put to practical use under most subject conditions. Furthermore, condensation f203a.

Direct current components such as sunlight are mostly cut off by 203b. AC amplifiers 201 and 204b sufficiently amplify components near the modulation frequency and then supply the signals to the next-stage synchronous detection circuit.

The synchronous detection circuit 102a, 102b inverters 205a, 205b and analog switches 206 & 2 shown in FIG.
06b and 207a, 207b,
Analog switches 206a, 206b, 207a, 20
7b f Switching by synchronization signal 5YIJC,
This is achieved by alternately selecting a non-inverted signal and an inverted signal.

Further, as another embodiment, there is a method (not shown) in which a four-phenomenal analog multiplier is used to obtain the product of the input signal and the alternating current component of the synchronization signal 5YNO.

The synchronously detected signal is supplied as a direct current (pulsating current) component to the next stage integration circuits 103a and 103b.

This integrating circuit 103a, 1031) is an operational amplifier 208a.

20[), resistors 209&, 209b, :Z7dayf 210a, 210b. Then, a current proportional to the synchronous detection output voltage flows through the synchronous detection circuit 1.
02, 1021) from resistors 209a and 209b, respectively.
through the capacitors 210a and 210b,
It is accumulated and becomes an integrated voltage, which is applied to operational amplifiers 208 & 20.
81). The voltage of each vA*
It is vB. In addition, 211a and 211b are capacitors 21
This analog switch is used to initialize the charges accumulated in the capacitors 2101L and 210b, and clears the charges accumulated in the capacitors 2101L and 210b by the CLR signal from the control circuit 111 in preparation for the next accumulation.

FIG. 10 shows the integration voltage vA v vB to l VA −
4B + and compare it with the comparison voltage vDf.
This shows part (B) of the circuit shown in the figure. Integrating circuit 10
The integrated voltages VA and VB output from 3a and 103b are applied to the operational amplifier 212 and the resistors 216 to 21 with the same resistance value R.
6 is subtracted by the subtraction circuit 104 composed of
Added to 6. The absolute value circuit 106 is an operational amplifier 217
, diodes 218 and 219, and a resistor 220 with a resistance value of 2R.
~222, and a resistor 223 with a resistance value R. Depending on the configuration of the operational amplifier 217, diodes 218, 219, and resistors 220, 221, the diode 2190 canode has a high impedance when a negative input is applied, and a potential that is 11 times the input voltage when a positive input is applied. As a result, a voltage of 10.5 l VA -VB l is applied to the negative input of the converter 7 (lator 224). By applying a voltage of -0.5 VD to this positive input, l VA -VB l is applied. A comparison of VDs is made.

Let this comparison value be DD.

Also, FIG. 11 shows the (O) part of the circuit in FIG. 8, where * vAlvB is added by the resistors 225 and 226 of resistance value R, and o, s (VA-141) is added to the converter 227.22B. is added to the positive input of Each con/
0.5 vL and 0.5 vH are added to the negative input of the filter, and (VA+VB) : VLI (
VA+VB): Comparison of vu is performed and the comparison value L
Outputs L and HH.

Furthermore, FIG. 12 shows the circuit (D) portion of FIG. 8, where VA and vB are directly compared by a converter 229, and a comparison value AB is output.

FIG. 12 shows another embodiment for obtaining the comparison value DD from vA e vB. VhvVB is controller 7 (rater 10.
It is added to the positive input of 231. It is also applied to the negative input via resistors 252 and 235 with resistance value R. Also, constant current sources 234 and 235 are connected to the negative input, and as a result, VB+i R, Vmu+1
A voltage of R is applied. However, 1 is the current value of 254.255, and the output of comparators 230 and 251 is the OR circuit 23.
6 to obtain the output DD. Output DD is VA-
VB') i R= 7D or VB-"F4') i
No true logic when R = 7D, IVA-4ml〉v
Represents the logic of D.

FIG. 14 shows a part of the order control circuit 111 implemented in hardware. Clock C is the sequence control circuit 11
1, and becomes the source of the synchronization signal BYNO for the light emission modulation of the light projecting element 40 and the synchronization detection circuits 102a and 102b. 236 is an n counter, and the period of this output ON determines the distance measurement period and the maximum integration time. Flip 70 knobs 237 and 238 are connected to signals DD and HH, respectively.
It is set by the signal On, and is reset every distance measurement cycle by the signal On. The outputs DDQ, HHQ, of each of the flip-flops 257, 258 are integral abort signals, o
It is input to the flip-flop 240 via the it circuit 239 and held at the cycle of the signal Ou. flip flora 12
400 inverted output enabled becomes infinite signal FAR. Signal FAR
and DDQ are connected to flip-flop 2 via OR circuit 241.
42 to output the motor rotation signal MO. This flip-flop 242 is also reset by the heat-containing signal EHQ signal, prohibits the output of the motor rotation signal MO at the time of one focus, and stops the motor 8. The signal AB is updated in the flip-flop 243 by a signal DDQ representing out-of-focus to become ABQ. Here, the previous bin, ie, v4), is true logic at vBO. Signal ABQ
.

and signal FAR are passed through OR circuit 244 to become signal FN representing the rotational direction of the motor. The final motor drive signals FF (towards infinity) and NN (towards near field) are obtained from the output of an AND circuit 245 which inputs the signal FN and the signal MO, or from the signal IFN via the NO'r circuit 246. The selection is made by the output of an AND circuit 247 which receives the output and the signal MO as inputs.

The synchronization signal BYNO consists of the signal DDQ, the signal H'HQ, and the power (
When both are pseudo-logic, the signal is input to the AND circuit 249 via the OR circuit 259 and the NOT circuit 248, thereby being input to the AND circuit 249. It is output in synchronization with the output OLK of clock C. The integration initialization signal OLR output from the OR@ path 250 becomes true logic from the time when the end of integration is determined based on the output of the OR circuit 239 input to the OR circuit 250 and the ON signal until the start of the next integration. .

FIG. 15 shows waveforms observed as each signal in FIG. 14 (7) when the state changes from front bin to rear bin to focus to infinity.

In the previous bin, DD rises first, and AB is at a high level at this time. With Yupin, j5DD Chikaradama stands up first, but A
B is a low novel. When in focus, HH rises. At infinite time, the maximum integration time is reached before any rise occurs.

FIG. 16 shows a part of the apparatus in which a microcomputer is used as the sequence control circuit 111 and controlled by software. This figure also shows examples of the light emitting element 30, the light emitting drive circuit 112, and the motor drive circuit 116. 251 is a microcomputer (for example, it has an internal structure as shown in FIG. 17), and input terminals receive the aforementioned signals DD and AB.

LL and HH are input, and the aforementioned signals 5YNO, CLR, FIF, and IN are also output from the output terminal. Further, it is easy to add a signal LOW for controlling the rotational speed of the motor.

The current flowing through the light emitting element 2 is the transistor 252.25.
5 via the signal 8YN (switched by 3).

The current flowing through the motor 8 is switched by the signal FF and the signal BIN via the transistors 254 to 257, and flows in the forward or reverse direction.

The circuit configuration including the transistors 258, 259 and the diode 260 is a voltage control circuit, and the voltage applied to the shimo motor is switched in two stages in response to a LOW signal. 261,
262 are the proximity switch and the infinite switch, respectively.
It closes when the photographic optical system hits the close end or infinity end, preventing it from being driven beyond its limit.

FIG. 18 shows electrical signal waveforms at various parts of the circuit shown in FIG.

The synchronous signal 5YNO is the synchronous detection circuit 102a.

102b, it is also used for current driving of the light projecting element 3, and a light-emitting RED is obtained. light receiving element 6a,
The electrical signal obtained from 6b is obtained in the form of a superimposition of the reflected light component of the projected infrared light and the external light component of the sun or artificial light, and has a waveform like the signal spa. This signal is sent to an amplifier ID1a with high-pass characteristics.

The signal Amp is obtained by multiplying by 101bK. When you start emitting light and release the OLR signal at the same time as #de,
The outputs of the synchronous detection circuits 102a and 102b are integrated,
An integrated waveform like a signal generator nt appears at the output of the integrating circuits 103a and 105b. This integral waveform increase rate is proportional to the amount of emitted light component of the emitted infrared light. Even for very weak inputs, a large 8N ratio can be obtained by integrating a sufficient number of times (time).

Next, the operation of this apparatus will be explained based on FIG. 8 and according to the flowchart numbers shown in FIGS. 19 to 23. Here, it is assumed that a microcomputer (hereinafter referred to as microcomputer) 251 is used as the control circuit 111.

■ When the AF operation switch (not shown) is closed, the control circuit 1
11 starts operating.

(2) First, it is determined whether the 5INS input terminal of the control circuit 111 is at a high level. When the 5INS input terminal is at a high level, the system operates in the adjustment mode shown in FIG. 22, and distance measurement is not performed. In the adjustment mode, the infrared light emitting diode 3 ON -01PF and the output of the light receiving element 6 are set to T. Time-integrated, zero-cost offset adjustment amplifier circuit 10
1a, 101b.

Synchronous detection circuits 102a, 102b, integration circuit 103a
, 105b or an adjustment mechanism (not shown), the positional relationship of the infrared light emitting diode 3 or the light emitting lens 4, the light receiving element 6, the light receiving lens 7, etc. is adjusted. Therefore, when the 8KNS tip terminal of the normal control circuit 111 is in the low level state 4D and the All' operation switch is closed, the device first operates in the following normal ranging mode.

■ When entering the normal distance measurement mode, first reset the ω flag as a prohibition means. The contents of the ω flag will be described later. Furthermore, as the memory for the (2) flag, memory M(1) in the RAM area of the microcomputer 251 is used.

(2) After this, the control circuit 111 starts the distance measuring operation.

That is, the control circuit 111 first controls the light emission drive circuit 112 and the synchronous detection circuits 102a and 102b using the synchronous signal BYNO.
The integration circuits 105a, 105 are driven in synchronization with the
Release the clear state of b. As a result, the light projecting element 3 projects a light spot image of infrared light toward the subject in synchronization with the synchronization signal EIYN (!), and the reflected light is detected by the light receiving element 6. two photosensitive areas 6
Electric signals corresponding to the amount of received light are output from A and 6B according to the light receiving position of the reflected light projection spot image, and this is amplified by amplifiers 101a and 101b and synchronously detected by synchronous detection circuits 102a and 102b. The optical information obtained in this way is then transmitted to the integrating circuit 103a.
, 103b, and the outputs thereof become integrated voltages VA and VB.

As mentioned above, these integrated voltages VA and VB are shown below.
The control circuit 111 is arithmetic-processed into the four digital information of
is input. That is, the digital output from the comparator 107 which is added to the absolute value circuit 106 by the subtracter 104 as a difference signal (mu-VB) and compares the magnitude relationship between the absolute value 1vmu-vBl and the comparison value VD. , DD ■ A digital output from the comparator 108 that compares the magnitude relationship between the sum signal VA+vB from the adder 105 and the comparison value vL, LL ■ The sum signal VA+vB from the adder 105 and the comparison value "I"
Digital output from the comparator 109 that compared the magnitude relationship with H ('VH > VL), HE ■Comparator 110 that compared the magnitude relationship between the signals VA and vB
On the other hand, in the control circuit 111, the time detection means in the microcomputer measures the integration time of the signal in the integration circuits 105a and 103'b, that is, the projection time of the light projecting element. t, the maximum integration time To (for example, 28 me
The magnitude relationship with ea ) is compared. When these pieces of information are given, the control circuit 111 determines whether the signal satisfies 1.mu.VB I≧VD, Vmu+vB≧v11, or extended t≧TO. When any one of these three conditions is met, the control circuit 111
determines that distance measurement is complete. FIG. 24 shows the states of the reflected light projected spot image P and the integral signals VA and VB when in focus, and as shown in FIG. Since the photosensitive area 6A and the photosensitive area 6B of the photosensitive element 6 are formed at an intermediate position, the photosensitive area 6A of the photosensitive element 6
, 6B provide outputs of approximately equal large values. For this reason, the values of the integral signals VA and VB rapidly increase while remaining substantially equal, as shown in FIG. 24 (2). Therefore, as shown in FIG. 24, the signal VA+'VB increases rapidly with time t, while the signal
As shown in Figure 24 (■), there is almost no increase. Therefore, the comparison value v
If + VD, Vm + vB for maximum integration time TO
≧vn, l ”11.-VB l < VD cut
It is determined that the object is in focus. On the other hand, Fig. 25 shows the reflected light spot image and the state of the integral signals VA and vB when out of focus.When the lens group 1 is in the front bin or rear focus state, the reflected light spot image P is shown.
As shown in FIG. 25 (2), since the output signal is biased towards either the photosensitive area 6A or 6B of the light receiving element 6, the output signal from the photosensitive area 6A or 6B of the light receiving element 6 generally has a larger value. Therefore, as shown in FIG. 25 (2), one of the integral signals vA and VB increases rapidly with time t, but the other integral value does not increase at all. Therefore, the 25th
As shown in Figures ■ and ■, until the signal VA+vB becomes larger than the comparison value vH, and until the integration time t reaches the maximum integration time TO, the signal I VA-VB l is l VA-VB
1≧VD.

Therefore, 1VAVBl≧VD force detection, vA+VB<v
If H and t (To, it is determined that the front focus or rear focus is on. Figure 26 shows the reflected light spot image P when the subject 5 is far away or the reflectance of the subject 5 is extremely low. In this case, the reflected light projection spot image P is not formed on the light receiving element 6, or even if it is formed, the amount of received light is extremely weak. Therefore, the output signals of the photosensitive regions 6A and 6B of the light receiving element 6 both have small values, and as shown in FIG.

For this reason, the integration time t becomes the maximum integration time To, and the signal VA+VB+l VA-VBl are both shown in FIG.
B l ≧VD (!: Ha is not true. Therefore, t≧To
r VA+VB < VHI VA VB 1<VD
If so, it is determined that the subject 5 is far away or in a state where distance measurement is difficult.

Above] Like, v people + VB ≧ VB or 17 people - ■ Bl ≧
By setting VD or t≧To as the condition for determining distance measurement completion, when the value of the integral signal VA + VB reaches a level that allows distance measurement, automatic focus detection operation can be started immediately, and charge is not wasted. Consumption is prevented. In particular, as will be described later, in this device, if distance measurement is completed within the maximum integration time To, in order to keep the time of one distance measurement cycle constant, the microcontroller will change the time until the maximum integration time T is reached. Since the next distance measurement cycle is started in order to perform distance measurement again after the To time has passed, there is no wasted charge consumption from the completion of distance measurement until 10 hours have elapsed. Extremely effective.

FIG. 26 specifically shows the contents of ■ as a subroutine. A step-by-step explanation will be given below.

(2) The light projecting element 6 and other distance measuring circuits start operating as described above.

@ Release the clear state of integrating circuits f03a and 103b.

θ The light projecting element 30 emits light.

■ Thereafter, by stopping the synchronizing signal 5YN (3), the multi-light driving circuit 112 is stopped, and therefore the light emitting element 6 stops emitting light.Also, at the same time, the synchronous detection circuits 102a, 102
The drive of b is also stopped.

(2) Determine whether distance measurement has been completed according to the distance measurement completion determination conditions described above.

θ When the above-mentioned distance measurement completion conditions are not met, the light emitting element 6 emits light again and the distance measurement is repeated.

■ When the distance measurement completion conditions are met, the signals DD, AB,
LID, HH (i.e. comparator 107.108.109゜1
10) is the memory M (output of 10) in the RAM area of the microcomputer
0). Thereafter, by stopping the synchronization signal 13YNo), the light emitting drive circuit 112 is stopped, and therefore the light emitting element 6 stops emitting light. At the same time, the synchronous detection circuit 10
2a and 102b' are also stopped.

(2) Then, the control circuit 111 (CLEAR output is set to a high level), the integration circuit 105a.

103b is brought into a clear state to prepare for the next distance measurement operation.

After performing the above series of controls, an automatic focus detection operation (based on the 4-bit data stored in the memo 9M(0)) and movement to another distance measurement mode to be described later are performed. The subroutine shown in FIG. 23 is also used in other distance measurement modes, which will be described later, by changing the condition for determining the completion of distance measurement in step (2).

Returning again to FIG. 19, when Vm+VB≧vH is detected, it is determined that the lens is in focus, as described above.

(2) When the focus is determined, the control circuit 111 supplies a stop signal (FF:IN:O) to the motor drive circuit 113 to stop the motor 8.

■ After the integration time t reaches the maximum integration time To,
A transition is made to a normal focus distance measurement mode suitable for normal focus, which will be described later, and distance measurement is performed again.

(2) On the other hand, if "A+VB≧■H" is not true, it means that the lens is out of focus or the value of the integral signal VAs■B is small, and it is determined here whether this is the case.

When IVAVBl≧VD, distance measurement is completed at t≧To, so as mentioned above, in this case, the integral signal ■A
Since the level of TVB is low, distance measurement suitable for the low level integrated signals vA and VB is performed. Transition to low level distance measurement mode, which will be described later.

(2) When 1vMo-vB1≧VD, it is determined that the lens group 1 is in an out-of-focus state, and then it is determined whether the focus is from the front or the rear. (2) When M>VB, it is determined that it is necessary to drive the motor 8 to move the lens group 1 to the nearest side with the rear focus.

[Phase] Next, the speed at which the motor 8 should be driven is determined. In this embodiment, the motor speed is controlled in two steps, and by switching the speed to a low speed when approaching the in-focus state from the out-of-focus state, the lens group 1 overruns the in-focus position. This prevents this from happening and makes it stop smoothly. The motor speed may be changed to any number of speeds as required. Here, the level of the comparison value vL is used as a determination criterion to determine whether the focus is close to the in-focus state or is significantly out of focus. When out of focus, the signal VA + VB is VA + VB2 vl o time u
Low speed, 7 people - 4 - When VB < vL, as a general rule, high speed. This situation is shown in FIGS. 25 and 27, with FIG. 25 showing the high speed and FIG. 27 showing the low speed.

As can be seen from FIGS. 25 and 27, the closer the focused state is, the closer the reflected light projection spot image P approaches the intermediate position between the photosensitive areas 6A and 6B of the light receiving element 6, so that the integral signals vA and VB The difference in levels will become smaller. Therefore lens #+1
The closer t is to the in-focus position, the longer the time t until A-VB +≧VD becomes.
The value of B increases. Therefore, the degree of out-of-focus can be determined by the magnitudes of 'V and +VB.

The speed control of the motor 8 and the reflected light spot image P described above
Figure 28 ■ shows the relationship of the positions on the light receiving element 6.
■It is. This increases the amount of light received in the photosensitive areas tsA and 6B when the reflected projected image P moves from the position Pl (rear focus) to the position P5 (front focus) via P2 (coupling bin). I understand. The part in the middle of Figure 28 is represented by O) within the low speed range. The value of KO is set to an appropriate value depending on conditions such as the speed of the motor and the inertia of the system. This will help.

Here, in this device, the completion of distance measurement is determined when the focus is out of focus.VA-VBl:VD==constant voltage VD.

At the time of 5. , -=vL, speed control is performed. In the embodiment of the present application, ■L=■L', but other values may be set.

Now, return to the flowchart of FIG. 19 again.

After being out of focus and determined to be in focus, ■mu+■addition≧
■Perform L judgment.

■ When Vm+vB≧vIJ, the control circuit 111 outputs a signal to drive the motor 8 at low speed as described above.
Lens group 1 is controlled to the close-range side.

(After the time elapses until t==To is reached, return to step (2)) Distance measurement is performed again in the normal distance measurement mode.

■ On the other hand, in Fig. 19■, when Vm+VB<vL, the motor 8 should be rotated at high speed as mentioned earlier, but here it should be further driven to the close side at this high speed. It is determined whether or not the judgment has been made n2 times continuously while the side distance mode is repeated n2 times. When the number of times is n2 or less, the mode changes to ■, and the motor 8 is driven at low speed toward the closest side.

(2) When it is determined that the motor 8 should be driven toward the closest position at high speed two or more times in a row, the motor 8 is thereafter driven toward the closest side at high speed. On the other hand, if the judgment to drive toward the closest position at high speed is not made n2 times in a row, and for example, a judgment such as focusing is made in the middle, the judgment to drive to the close side at high speed is again made n2 times in a row. The motor 8 will not reach high speed until then.

As mentioned above, the reason for controlling the speed of the motor 8 is to make sure that the motor 8 moves at a low speed when starting, which improves the feel at the time of starting and also reduces noise in the integral signal vA + VB. In particular, this is to reduce the hunting behavior of lens #1.

Regarding the operation of [phase] to [phase], [phase] to ■ and motor 8
Since the operations are exactly the same except that the driving direction is reversed, the explanation will be omitted.

Next, the normal focus distance measurement mode will be explained.

■ When it is determined that the in-focus state is achieved in (2), and the integration time t reaches the maximum integration time To, distance measurement is performed again in the normal focus distance measurement mode suitable for distance measurement from the in-focus state. It will be done. This is because the distance of the subject may generally change moment by moment even after focusing, so distance measurement is re-measured at fixed intervals (maximum integration time To in this case) and lens group 1
This is because it is necessary to check whether the camera is in focus. In the normal focus distance measurement mode, the conditions for determining the focus state to complete the distance measurement are from V+VB≧■H in the normal distance measurement mode to VA+VB≧'VL.
(VL<VH). The reason why the condition for determining completion of distance measurement is changed from Vm+vB≧vH to Vm+vB≧■L is to widen the range in which it is determined that the focus state is reached.

Finally, the so-called dead zone, which is the range in which it cannot be determined that the lens is out of focus, is widened to make it difficult for the lens group 1 to move from the position where it was previously determined to be in focus. For example, by setting vXJ2%V, as shown in FIG.
It is difficult to determine that l≧VD, and it is difficult to get out of focus. Therefore, it is possible to reduce malfunctions caused by noise superimposed on the integral signal VmuyvB. In addition, by lowering the comparison value, it is possible to shorten the integration time and the time during which the light emitting element 3 emits light, and in a device like this device where one distance measurement cycle takes a fixed time, the power consumption can be reduced. Needless to say, it is advantageous in terms of consumption.

The other conditions for determining completion of distance measurement are the same as in the normal distance measurement mode, and subsequent operations proceed in the same manner as in the normal distance measurement mode.

In other words, the control circuit 111 starts distance measurement, and when one of the three conditions of 1vmu-VB l≧VD, Vmu+vB≧vL, or t≧To is satisfied, the control circuit 111 completes the distance measurement and Comparison signals DD, AB, LL, Ha are memo IJM
(0) is stored again.

■ Note here ■! Based on the data stored in j M (0), 1v person-vB 1≧VD,
Determine whether the image is out of focus. 1■Mu-Vnl
If it is determined that ≧VD, there is no focus, and distance measurement is performed again in the normal distance measurement mode.

■ When 1vmu-VB1≧VD is not the case, a sufficient signal cannot be obtained because the object is in focus or the object is far away or the reflectance of the object is low, and the integral signal depends on whether Vmu+VB≧vL. The level state of V, , VB is determined, and based on that state, it is determined whether or not focus is achieved. Vmu+v
When B≧vL, distance measurement is completed at t≧l1lo, and since the integral signals Vm and VB are extremely low, it is determined that the object is far away or the reflectance of the object is low. Switch to level distance measurement mode and perform distance measurement again.

[Phase] On the other hand, when Vm+vB≧vL, it is determined that the camera is in focus, and then it counts up to the maximum integration time To in the same way as described in (2).

■ Next, it is determined how many times the normal focus distance measurement mode has been turned on and off. When the number of repetitions is n (ng), the camera returns to the normal focus distance measurement mode, and remains in the normal focus distance measurement mode until n: reaches no or changes to another distance measurement mode with [Phase] or ■. Perform distance measurement. Switch the normal focus distance measurement mode n9 times, and when n = = : ng, return to the normal distance measurement mode again, and the next distance measurement will be in the normal distance measurement mode, and the Rima 9 regular dead zone will be used. Distance is done.

As described above, by returning the dead zone to its normal state every (nl)th time, it is possible to prevent a decrease in distance measurement accuracy. As mentioned in (2) above, widening the dead zone increases stability, but this also causes a reduction in distance measurement accuracy as a reaction. Therefore, n (by returning to normal distance measurement mode each time)
In-focus and out-of-focus judgments are made using a regular dead zone to compensate for the decrease in distance measurement accuracy. Therefore, by doing this, it is possible to achieve both stabilization during focusing and distance measurement accuracy. In addition, n
It is necessary to set o and vL to appropriate values for the above purpose.

Next, the operation in the low level ranging mode will be described based on FIG.

[Phase] As mentioned above, in the normal distance measurement mode or normal focused distance measurement mode, both the integral signals 7 and VB are determined to be at low levels, or the integral signal is determined to be low in the ω time distance measurement mode described later. When it is determined that the levels of the signals VA and VB have risen to a certain level and distance measurement is possible, distance measurement is performed in the low level distance measurement mode, which is suitable for distance measurement when the level of the integral signals 7 and B is low. will be carried out. In the low level ranging mode, when the integral signal VAy■B is obtained in the same manner as in the normal ranging mode, completion of ranging is determined based on V+vB≧vH or t≧T. Note that, unlike in the normal distance measurement mode, VA-VB≧vH is excluded as a condition for determining completion of distance measurement. This is because in the low level distance measurement mode, the level of the signal detected on the light receiving probe 6 is low because the subject 5 is far away or the reflectance of the subject 5 is low. The 13/'N of the signals VA and VB is not very good, and for example, the magnitude relationship between the levels of the integral signals VA and vB tends to be opposite to the original values.91 This is to prevent erroneous distance measurement from occurring. . In other words, if signals from the near direction and infinity direction are output repeatedly, if these are detected as they are, out-of-focus signals from different directions will be output alternately, which may result in unstable operation. be. Figure 31 shows an example of such an integral signal with bad s and Ai.
Since the VA signal and the VB multiplied signal are alternately exchanged, as shown in Figure 30, <(I) point 1 VA-VB l ≧VD, VB>VA. In this case, it is determined that the front pin state is present, and the control circuit 111 outputs multiple control signals to drive the motor 8 in an infinite direction. Also, by chance (probabilistically) (■), VB > vA, but (summer)' shows ＜+vmu'VB l <
If it is VD, distance measurement is not determined at point (1) (n) o point te vA>V: et l vA-v
Bl > VD (D judgment will be made. This will result in outputting an out-of-focus signal to the motor 8 in the direction completely opposite to the above case. In order to reduce the instability as described above as much as possible. In the distance measurement mode at low level, 1vAVBl≧VD is used as the criterion for completion of distance measurement.
If it is not determined, the integration is continued until t2Tfi, and then lVA-vB l≧VD is determined. By switching between a plurality of modes in this manner, it is possible to achieve both the advantages of the normal ranging mode (power saving, etc.) and the stability of the low level ranging mode.

[Phase] Returning to the flowchart of the low level distance measurement mode in Fig. 20, when the distance measurement is completed at @, the next time the distance measurement is completed is ■A-
4-It is determined whether or not VB≧V is satisfied. When vA-1-vB≧vH, signal vA.

This means that V is sufficiently large, and it is determined that there is no need to perform distance measurement in the low-level distance measurement mode, and the mode returns to the normal distance measurement mode. Fig. 32 shows signals vA, signal VB, and signal VA- when returning from low level mode to normal ranging mode.
1-VB, indicating the state of the signal l VA-Vnl. O
When K is indicated, the distance measurement is not completed even if it becomes VD, and the distance measurement is continued. ■ As shown in <
t<To.

When the condition of Vm+VB≧1 is satisfied, distance measurement is completed and the mode returns to the normal distance measurement mode.

When OVA+VB≧- does not hold, it means that distance measurement was completed under the condition of t=To. Subsequently, the level of Vm+vB is determined, and it is determined whether it should be determined to be infinite or whether it is within a range measurable area within a finite distance. V+V
When B≧VL (vL<vH), the integral signals VA, VB
Since the level of is extremely low, it is determined that the object is in an infinite state, and subsequent distance measurement is performed in the infinite time distance measurement mode, which will be described later. FIG. 32 is a diagram showing the state of the signal ■Ay vBs signal ■A+VB when entering the infinite distance measurement mode. As a result of distance measurement at t=:To-i, VA + VB < VL means that the integral signal VA,
Since the values of VB are both extremely low, it can be determined that the object is in an infinite state, and when I Vh −VB
l (7) Even if the value HWAVE 1≧VD or 1 VBI<VD, this is ignored. Note that even when the object is not far away and the reflectance of the object is low, the light-receiving element 6 cannot receive sufficient reflected light, so this situation also occurs in this case. In systems that measure distance, it is very difficult to distinguish whether an object is far away or has low reflectance. Therefore, in order to drive the motor 8 in the infinite direction, the control circuit 111 receives multiple control signals (FF=i
, NN = Q) to the motor drive circuit 116. Naturally, if another distance measurement signal is obtained before the photographing lens 1 reaches the edge, the motor drive circuit 113
A stop or reverse signal is applied to.

■ 7 people, 4- When vB≧■L, the vA+VB signal after the tsum TO time integration is vL≦VA+VB (When Vi, next 1■mu-VB determines whether l≧VD or not, and l When VA -4B l <VD, in principle, it is determined that the focus is at a low level.As shown in Fig. 33, <IV
When A-Vn I≧VD, it is determined that the lens is out of focus at a low level, and as a general rule, the motor is rotated at a low speed in the focusing direction.

[Phase] Now, as mentioned above, when 1■mm+VBI≦VD, the control circuit 111 outputs the simulator stop signal as low level focusing, but as an exception, the flag = 1
This stop signal is not output when . (2) The flag is set to 1 when shifting to the ω time distance measurement mode, and is reset to 0 in the normal distance measurement mode as described above.

(2) When the flag is set to 1, the control circuit 111 outputs the same control signal as the previous time to the motor drive circuit 113. If the flag in low level distance measurement mode is set to 1, it is only when the transition is made from ω mode to low level distance measurement mode, and the low level distance measurement level is set from ω mode to low level distance measurement mode. When shifting to the mode, a signal to drive the motor in the infinite direction is output as will be described later. Therefore, when the ω flag=1, the motor 8 continues to move the lens group 1 in the infinity direction even if it is determined that focusing is at a low level.

The reason for creating this exception for ω flag = 1 is that when focusing on a subject that is far away or has a reflectance that causes a low-level focus signal to be output, the focus may deviate greatly from the in-focus state to the close side. It has been experimentally confirmed that when distance measurement is started from a position where the focus signal is still in the out-of-focus state, a focus signal is output due to the influence of leakage current of the light-receiving element 6. For this reason, if the motor 8 is stopped with such a false focus signal, it will stop in a state where it is largely out of focus.

For this purpose, 72 signals are used to identify false focusing signals, and if the flag = 1 as described above, the control circuit 111 continues distance measurement in the low level distance measurement mode while outputting the infinite direction signal. It is said that

[Phase] When the ω flag = 00, the control circuit 111 outputs a regular simulation stop signal, and the motor 8 stops.

[Phase] On the other hand, in [Phase] l VA −VB I≧
When it is vD, it is determined that it is out of focus at a low level. At this time, after it is determined that the lens is out of focus at a low level, it is determined whether or not VA>VB.

■ When VA ) VB, the control circuit 1 remains in the rear bin state.
11, it is determined that it is necessary to drive the motor 8 in order to move the lens group 1 to the nearest side. In the low level ranging mode, the motor rotates at a low speed in principle. The reason is that in the ranging mode at low level, the integral signal V,
, VB are both small, φ is low, and a sufficiently reliable direction signal cannot be obtained, so this is to reduce unstable operation of the lens group 1 such as hunting.

[Stock] Next, it is determined whether or not the bin state after out-of-focus at a low level has been determined n4 times in a row. When a constant direction signal is obtained n4 times in a row, the signal vA,
It is determined that the S/N of VB has become sufficiently high, and the mode returns to normal distance measurement mode. In this way, power is saved in normal distance measurement mode (distance measurement is completed when IVA-VBI≧VD and rests until To)
This makes it possible to achieve both the stability of the distance measurement mode at low level (determination is made after integration up to To).

[Phase] Return to [Phase] again. When vA>VB is not reached, press ■F2.
A determination is made as to whether G=1.

(2) When the flag = 1, the motor 8 is rotated at high speed to move the lens group 1 to the close side.

The reason for the high speed here is that, as with low-level focusing, the motor 8 temporarily slows down near the false focus signal even though it is out of focus due to a false focus signal. This is to prevent

[Phase] On the other hand, when the ■ flag=00, the speed of the motor 7 is driven at a low speed according to the principle described above.

(2) Next, for the same reason as (2), if the direction signal is outputted five times or more in a row, normal distance measurement is resumed, and if not, distance measurement is performed again in the low level distance measurement mode.

■ On the other hand, when the in-focus state is determined at a low level in [phase] and a signal is output to stop the rotation of the motor 8,
When the level is low, the camera shifts to focus distance measurement mode and distance measurement is performed again. In focus distance measurement mode, the condition for determining distance measurement completion is VA + V.
B ≧vL (VB,, <VH) or t≧T, (T
I ('['oFor example, T1 = 1.76 m sec
) Judgment condition for completion of distance measurement in the distance measurement mode when the door is lowered: ■Different from A+VB≧VH or t≧To. This is the second
Similarly to the normal focus distance measurement mode explained in Figure 0, T1 is changed to T1.
If it is made shorter than o, the dead zone will be widened as shown in Fig. 35, and the lens group 1 will be stably stopped at the position determined to be in focus, and the power consumption will be reduced. be. Especially in the low level focusing state, the signal ■A
, Since the VB level is low (S/N is poor), stabilizing the in-focus state by widening the dead zone is extremely effective. In addition, ■A-1-vB≧vL (VL<VH). This is to enable focus determination even in the normal distance measurement mode in accordance with the maximum integration time T1.

[Phase] When distance measurement is completed, first, it is determined whether ■A+VB≧■L. When vA+VB≧VL, the integrated signal is above the predetermined level even though the integration time has become shorter, so it is determined that the signal has become sufficiently large that distance measurement can be performed in normal distance measurement mode, and normal distance measurement is performed. Return to mode and perform distance measurement.

■ VA +VB≧Vs, TE fx 1 VA”B
Determine whether l ≧VD. IVA-VB
When l≧VD, it is determined that the signal has become sufficiently large, similar to [phase], and the mode returns to normal distance measurement mode.

@VA + VB < VLkal VA-VB
When I<VD, it is determined that the camera is in focus and counts until it reaches t==To.

■ Determine whether or not the distance measurement in the focus distance measurement mode at low level has been repeated n3 times, and if it is n5 times, return to the distance measurement mode at low level, and if it is less than n5 times, it is set to low level. Change the focus/distance mode. Is this a low level every n5th time as in the case of normal focus distance measurement mode? glj (return to distance mode), and set the distance measurement completion judgment condition to vA+VB≧■R or t
≧T.

By doing so, the dead zone is returned to its original state and a decrease in distance measurement accuracy is prevented. As described above, by changing the distance measurement mode from the low-level focus distance measurement mode to the low-level distance measurement mode, it is possible to simultaneously ensure focusing stability, power saving, and maintenance of accuracy at low levels. becomes possible.

Next, the ω wait mode will be explained with reference to FIG.

When shifting to the ω time distance measurement mode, the 19th
This is a case where it is determined that VA+■B<vL in the [phase] of the figure. That is, as explained in the flowcharts of FIGS. 19 and 20, when the distance measurement integrated signals ■A and VB are both extremely low, it is determined that ω is present, and the distance measurement when the subject 5 is in an infinite state is determined. Enter the appropriate time and distance measurement mode.

(2) In the 0 o'clock distance measurement mode, it has already been determined that there are an infinite number of ω objects 5, so first the motor 8 is driven at high speed in the direction of infinity.

(2) Subsequently, the ω flag is set to 1 to indicate that an infinite signal has been generated. As explained above with reference to the flowcharts of FIGS. 19 and 20, the ω flag is used to distinguish false focus signals, and is reset to 0 in the normal distance measurement mode.

@Next, n6 is set to use M(6) from the RAM area in the microcomputer as a counter for counting a predetermined number of times n6.

@ In the 0 o'clock distance measurement mode, it is determined that the distance measurement is complete if ≧- or t=T2. Here, the reason why IVA-VBI≧VD, which is one of the conditions for determining completion of distance measurement in normal distance measurement mode, is not satisfied is that the integral signal V is not satisfied in the 0 time distance measurement mode as well as in the low level distance measurement mode. , VB are both extremely low values, so the 1mm-VB IO value is unreliable. Furthermore, in the 0 o'clock distance measurement mode, the maximum distance measurement time T
2 (T2<TO, for example, T2=19.3m5ec), the maximum integration time can be shortened even in the distance measurement mode at low level, as will be described later.
If B>vXJ, then Vm, and if vA-4-VB<VL, then Vm if vA-4-VB<VL.

In order to determine that the direction is infinite regardless of the magnitude relationship of VB, V person + vB happiness V1. This is to prevent the completely opposite direction from being determined due to the influence of noise superimposed on the signals V and VB, thereby preventing noise from occurring. In this apparatus, the same effect is obtained by changing the integral time Tot-T2 instead of changing the value of <VL, as shown in FIG.

[Yes] Vm+vB;z When vH, it is determined that distance measurement is possible in the normal distance measurement mode, and distance measurement is performed in the normal distance measurement mode.

When Om+VB≧- does not hold, distance measurement is completed at t=:T2, so TO-T2 time is counted.

@ Determine whether V+VB≧vL. V+
When vB≧vLO, distance measurement should be performed in the low level distance measurement mode as described in FIG. 20, so the system returns to the low level distance measurement mode and enters the next distance measurement cycle.

■ After the 0 o'clock distance measurement mode starts, n6
Determine whether times have elapsed. If it has not reached the n6th time, it returns to @ again and distance measurement is performed at the longest integration time T2.

That is, this means that the maximum integration time is T2 (T2 <
To ), but as described below <TscTs<T
2<To) should not be changed.

The reason for this is that, as mentioned above, the signal is small because the object is actually far away or the reflectance is low, so it is okay to judge it as infinity. The second reason is that the object is at a distance that can be measured, but because the size of the object is finite, the distance of the object and the current position of the distance measurement system are significantly different. When the spot image P or the light-receiving element 6 is separated from the subject 5, it is initially driven in the infinity direction by infinity determination,
When the reflected light projection spot image P begins to form correctly on the light receiving element 6, distance measurement becomes possible, and the lens is driven to the in-focus position depending on the magnitude relationship of the V and VB multiplied signals.

In such a case, the maximum integration time is T, (T, <'r2
If it is set to (To), the dead zone will widen, and the response will be delayed, resulting in a delay in proper control of the motor 8, resulting in an overrun of the in-focus position. In order to eliminate such defects, the maximum integration time is set for n6 times in order to distinguish between a true infinite state and a short-term infinite state during the focusing process, as described above. The distance measurement is performed without changing T3 to T2 (T2<To). Note that as long as distance measurement is being performed in the ω time distance measurement mode, a signal for driving the motor 8 in the infinite direction is always outputted to the control circuit 111. However, when the lens 1 reaches the infinite end, the infinity switch 262 turns ON and the motor 8 is stopped.

[Phase] Maximum integration time T5 (Ts
<T2 (for example, T5 ==1.76 m 8eQ ).

The completion of distance measurement is determined when VB≧VL or t≧T5. This is done by setting the maximum integration time to T3 (T3<T2) in the same manner as the low-level focus distance measurement mode described above, thereby widening the dead zone and achieving both stability and power saving.

■ If vM+vB≧vX, the maximum integration time T! l
Even though (T3 < T2) is shortened, the comparison value vT
Since the signal vA y vB has reached J, it is determined that the signal vA y vB is large enough to enable distance measurement even in the normal distance measurement mode, and the mode returns to the normal distance measurement mode.

[Phase] When Vm+VB<vL, the distance measurement result is integral signal 7
Man.

Since the VB level is still extremely low, it is determined that the subject 5 is again in an infinite state, and the To-Ts waiting time is counted.

■ Next, at the maximum integration time T5, it is determined whether or not distance measurement has been performed n7 times, and if n7 times have not been reached, the [
Return to Stocks.

(2) When the n7th distance measurement is completed, next, the maximum integration time is set to T2 and distance measurement is performed once again.

Here, the reason why the integration time is returned to T2 every predetermined number of times (n7) is to prevent a decrease in distance measurement accuracy, as in the above-mentioned low level focus distance measurement mode. In addition, at @, M(15) is used to measure the distance n6 times in a row with the maximum integration time T2.
= n6, but here it is only once, so M (6)
= 1.

In the above, we will mainly explain the 5 distance measurement modes: 10 Normal distance measurement mode 2 Normal focus distance measurement mode & Low level distance measurement mode 4, Low level focus distance measurement mode 5, oo distance measurement mode A detailed explanation has been provided based on the flowcharts shown in FIGS. 19 to 21. As is clear from this explanation, the automatic focus detection device according to the present invention achieves highly reliable and stable operation by appropriately switching the distance measurement modes 1 to 5 above to perform distance measurement. Gained, also,
This makes it possible to achieve both power savings.

In the above embodiment, in-focus/out-of-focus is determined based on the integral signal (1) indicating the light receiving position of the projected spot image P.

Although the absolute value of the difference in VB is determined from the magnitude relationship of IVA-VBI, it goes without saying that this may also be determined from a ratio such as vA/VB. That is, the present invention can be applied to any signal as long as the magnitude relationship of the signal vAlvB is clear. Further, instead of determining the signal level from vA-1-VB as in the above embodiment, the signal level may be determined from either vA or VB. That is, the signals Vmu, VB
The present invention can be applied to any device whose level state can be known. Furthermore, it goes without saying that the present invention 8A can be applied even if the light receiving element has three or more photosensitive areas.

As explained above, the present invention includes a first focus detection system having a narrow focusing range and a second focus detection system having a wide focusing range in order to detect the focus of the imaging optical system. When the focus state is determined by the second focus detection system, the next focus detection is performed by the second focus detection system, and when the focus state is determined multiple times in succession by the second focus detection system. Since the next focus detection is performed by the first focus detection system, the operation of the automatic focus detection device can be stabilized and accuracy can be maintained, which is extremely effective.

[Brief explanation of drawings]

1 to 7 are schematic diagrams showing the optical system of the automatic focus detection device according to the present invention, FIGS. 8 to 18 are explanatory diagrams of the electric circuit of the automatic focus detection device according to the present invention, and FIG. 19 23 are operation flowcharts of the automatic focus detection device according to the present invention, and FIGS. 24 to 35 are supplementary explanatory diagrams of the operation flowcharts shown in FIGS. 19 to 23. 1...Photographing lens 2...Planned focal plane 6...Light emitter 4...Light emitter lens 5--Subject 6...Light receiver 7...Light receiver lens 8...Motor 9 ... AP circuit Figure 5 Figure '7 S YNC 2 Otsu 7 -66- 2nd? Figure 2B■ 25th Goods Figure 29■ /a t

Claims (1)

[Claims] (1) In order to detect the focus of the imaging optical system, it has a first focus detection system with a narrow focusing range and a second focus detection system with a wide focusing range, and the first focus detection system When the focus state is determined, the next focus detection is performed by the second focus detection system, and when the focus state is determined multiple times in succession by the second focus detection system, the next focus detection is performed. An automatic focus detection device characterized in that the detection is performed by a first focus detection system. (2) An automatic focus detection device according to claim (1), wherein the automatic focus detection device R is controlled by a microcomputer.