JPH027A - Range-finding device for camera - Google Patents

Abstract

PURPOSE:To accomplish focusing operation on a main object independent of the intensity of reflected light by connecting first and second comparators provided with high and low reference voltages to respective photodetectors and obtaining first and second range-finding signals from the group of the comparators. CONSTITUTION:The first and the second comparators 31a-35a and 31b-35b provided with the high reference voltages V1a-V5a, the low reference voltages V1b-V5b are connected to the photodetectors S1-S5 which receive reflected light from an object. Signals A1a-A5a and A1b-A5b which respond to the intensity of the reflected light of the object are outputted from the groups of the comparators. Either lens setting position is selected depending on whether or not difference between first and second lens setting positions which are obtained in response to the first and second range-finding signals satisfies a specified condition. Therefore, focusing on the main object can be performed with high probability even if there is a level difference in the intensity of the reflected light.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an active type distance measuring device used in a camera.

[Conventional technology]

Active type distance measuring devices, which are often used in recent compact cameras, project a light beam for distance measurement toward the subject, and use a light receiving sensor to receive the reflected light from the subject. There is. The light-receiving sensor has multiple tiny light-receiving elements arranged in the baseline length direction, and by electrically identifying which of the light-receiving elements the reflected light from the subject has entered, it can measure the distance to the subject. You can get the distance signal.

In such distance measuring devices, when strong reflected light from a subject with high reflectivity or a close-range subject enters a specific light receiving element, adjacent light receiving elements also receive a certain percentage of light due to effects such as crosstalk. Photoelectric output may appear.

Therefore, even if a photoelectric output appears on the photodetector,
It is not possible to determine whether this photoelectric output is due to light incident normally on the light receiving element from the subject or due to the effects of the aforementioned crosstalk, etc., which may deteriorate the accuracy of distance measurement.

That is, as shown in FIG. 12(A), when a high-intensity reflected light pattern 40 from the subject is incident on the light receiving element S4 among the light receiving elements 31 to 56 arranged in the base line length direction, this original reflection is The light pattern 40 is often accompanied by eight concentric rows 41, and adjacent light receiving elements S3.
A photoelectric output also appears at S5, as shown in FIG. 4(B). Moreover, even if the halo 41 is small,
When strong reflected light from a subject enters the light receiving element S4, the adjacent light receiving elements S3. S
5, a certain ratio of photoelectric output often appears. In such a case, if there is one comparator connected to each of the light-receiving elements 33 to 55 and its reference voltage is , then a high-level signal ( H signal) is output from each comparator, and it is erroneously detected that the reflected light from the subject is also incident on the light receiving elements S3 and S35.

On the other hand, when the reference voltage of the comparator is set to VN, the intensity of the reflected light from the subject is weak (and only the photoelectric output of the level shown by the dashed-dotted line can be obtained from the light receiving element S4 where this reflected light is incident). Sometimes, it becomes impossible to detect the incidence of reflected light from any of the comparators.

Considering these points, in the distance measuring device described in Japanese Patent Application Laid-Open No. 5-29112, when photoelectric outputs appear from a plurality of light receiving elements, the reference voltage of the comparator connected to each of the light receiving elements is set to By changing the maximum level as a reference, the generation of false signals due to the influence of crosstalk etc. is avoided.

[Problem that the invention seeks to solve]

However, in the distance measuring device described in the above-mentioned publication, the circuit configuration after the light receiving element is complicated, resulting in a large cost burden. In addition, if the main subject with average reflectance, such as a human being, is located at a close distance, and there is a secondary background object with high reflectance at a far distance, The disadvantage is that distance measurement is performed using the same method, resulting in poor focus on the main subject.

[Purpose of the invention]

The present invention has been made in order to solve the above-mentioned difficulties of the conventional technology. The purpose is to provide a distance measuring device for a camera.

[Means for solving problems]

In order to achieve the above object, the present invention includes two comparators each having two types of high and low reference voltages applied to each of the light receiving elements arranged in the base line length direction to receive the reflected light from the subject. Detecting a first ranging signal based on a combination of inverted signals from a comparator connected to a high reference voltage and a second ranging signal based on a combination of inverted signals from a comparator provided with a low reference voltage; 1st
When the lens set position corresponding to the distance measurement signal is farther than the lens set position corresponding to the second distance measurement signal by a predetermined value or more, the lens set position is determined by the second distance measurement signal. .

Also, the lens set position corresponding to the first distance measurement signal is the second distance measurement signal.
When the lens set position corresponding to the distance measurement signal is farther than the lens set position by less than a predetermined value, it is also an effective means to determine the lens set position based on the first distance measurement signal.

[Effect]

According to the above, the second distance measurement signal obtained via the comparator to which a low reference voltage is applied also contains information due to strong reflected light from the subject, whereas The first distance measurement signal obtained through the comparator often does not include information due to weak reflected light from the subject, and therefore the first distance measurement signal is not included in the first distance measurement signal. The second ranging signals may not match. In such a case, the second lens set position corresponding to the first ranging signal and the second lens set position corresponding to the second ranging signal are evaluated to determine the lens set position. In other words, when the second lens set position is farther than the second lens set position by a certain value or more, the first distance measurement information includes information from a background object with high reflectance. The lens set position is determined based on the second distance measurement signal corresponding to the short distance side where the probability that the main subject is located is high and the depth of focus is shallow.

Furthermore, when the second lens set position is further away from the second lens set position by less than a predetermined value,
The second ranging signal may be determined to be affected by crosstalk, and the lens set position may be determined based on the first ranging signal.

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

〔Example〕

FIG. 2 schematically shows an active type ranging system, in which a light projecting section 2 includes a discharge tube 3 that emits near-infrared light. discharge tube 3
4. A slit plate that shapes the light from the 4. It consists of a light projecting lens 5. Further, the light receiving section 7 includes a light receiving lens 8. It is composed of a light receiving sensor 9. The optical axes 5a and 8a of the light projecting lens 5 and the light receiving lens 8 are connected to the photographing lens 10.
are parallel to the optical axis 10a and separated by the base line length. As will be described in detail later, the light receiving sensor 9 is formed by arranging small horizontally long rectangular light receiving elements 31 to 56 in the baseline length direction.

When a slit light is emitted from the light projector 2 toward the subject, a portion of the light is reflected by the close subject 12, and the reflected light 12a enters the light receiving element S3 through the light receiving lens 8. Furthermore, when a part of the slit light is reflected from the middle-distance object 13 or the long-distance object 14, the reflected light 1
3a and 14a are each light receiving elements S2. People start shooting at Sl. Therefore, among the light receiving sensors 9,
The object distance can be determined by detecting which light-receiving element the reflected light from the object is incident on. In addition, when a slit light is used as the light beam for distance measurement in this way, the light beam for distance measurement can be irradiated even when the main subject is removed from the center of the shooting screen.
This eliminates the need for troublesome operations such as aiming during distance measurement and reframing after distance measurement, but
Distance measurement can also be performed by projecting a spot light instead of a slit light.

Figure 3 shows an optical system that adds an infrared light emitting diode 15 (hereinafter referred to as I RED 15) to the above-mentioned distance measuring system, and uses the same light receiving sensor 9, but further improves the distance measuring function at short distances. This shows the system. I RED l
The light projection optical axis 15a of No. 5 is tilted toward the light receiving sensor 9 by an angle θ with respect to the optical axis 5a of the light projection lens 5, and emits a light beam in a spot pattern toward the subject. According to this, it becomes possible for the light receiving sensor 9 to receive reflected light from a subject at a closer distance than the close range that can be detected by the slit light from the light projecting section 2.

FIG. 4 shows the correspondence of the set position of the photographic lens 10 with respect to the subject distance range, N, to NI.

represents the set position in the normal range determined when measuring the distance with the slit light from the light projector 2, and n, ~ n5 are -1RED
It represents the set position of the macro area determined when distance measurement is performed using the spotlight from No. 15.

These set positions n I-n sa N 1 to N 1
6 is the subject distance l, ~j! Is is set as the optimum focusing distance, but if the diameter of the circle of confusion that is considered to be in focus is, for example, 0.025 mm, then when the depth of field of the photographic lens 10 is taken into account, approximately! It is possible to continuously focus on a subject distance range from , to infinity.

Discharge tube for distance measurement described above 3. Light receiving sensor 9゜1 RE
D l 5 is used with the circuit shown in FIG. The discharge tube 3 for distance measurement is operated and controlled by a strobe drive circuit 18 together with the discharge tube 17 for illuminating the object during photographing, and the I RED 15 is drive-controlled by an IRED drive circuit 19. The light receiving element Sl-36 constituting the light receiving sensor 9 is connected to a signal processing circuit 20, and the photoelectric output from each of the light receiving elements S1 and 36 is converted into a signal by the signal processing circuit 20. An AF control circuit 21 is connected to the signal processing circuit 20 , and the AF Illll circuit 21 converts the signal output from the signal processing circuit 20 into ranging data and inputs it to the microcomputer 22 . Note that, as will be described in detail later, the AF control circuit 21 controls the discharge tubes 3. A signal for lighting the IRED 15 is output.

The microcomputer 22 includes the strobe drive circuit 18. In addition to the AF control circuit 21, the program shutter 23
A shutter drive circuit 24 for controlling opening and closing of the shutter drive circuit 24. A photometric circuit 25 for measuring subject brightness, a motor control circuit 27 for driving a motor 26, and an AF table 28 that associates the set position of the photographing lens 10 with each distance measurement data input from the AF control circuit 21 are connected. .

The signal processing circuit 20 has a circuit configuration as shown in FIG. 1, and each photocurrent signal from the light receiving elements 51 to 56 is converted into a voltage signal by a first-stage operational amplifier to which a reference voltage V3g is applied. be done. This voltage signal also includes a DC component, that is, a photoelectric signal caused by external light such as sunlight, but since a capacitor for cutting low frequency components is connected to the output terminal of each first-stage operational amplifier, the reference voltage Only signal components that do not include DC components are input to the operational amplifier at the next stage of V3g. The photoelectric output amplified by the next-stage operational amplifier at a constant amplification factor is
Two comparators 31a, 31b, 32a, 32b, . . . are provided for each light receiving element Sl-35.
, 35a and 35b, and the photoelectric output from the light receiving element S6 is input to the comparator 36a.

A comparator 31a to which the same photoelectric output is input.

31b, 32a, 32b, ---, 35a, 35b are each supplied with a reference voltage V ma by a voltage divider 38.
n Vmh is given. The level of this reference voltage is set to V->V-b, so the photoelectric output output from each photodetector and amplified to a certain ratio by the first and second stage operational amplifiers is based on two types of high and low standards. Voltage V
It is compared with file Vmk. Then, the photoelectric output is the reference voltage V am or the reference voltage V. When it is above, a high level signal (H signal), reference voltage Vam or V. If it is below, the low level signal (L signal) of each comparator 31a, 31b, 32a, 32b, --...
Appears at the output ends of 35a and 35b. In this way, the photoelectric output from each light-receiving element is adjusted to two different reference voltages, high and low, V□ and vo.
By comparing with a comparator given, 2
Valued two-series signal output A0. .

Aab can be obtained. That is, the reference voltage vI1. explained in FIG. The reference voltage corresponding to vL is applied to each comparator 31a, 31b, 32a, 32b1.
..., 35a, 35b as V, lI, Vl. This makes it possible to select and use one of the signal outputs A, .

Note that in this embodiment, this reference voltage V. .

vo is a light receiving element S that receives reflected light from a distant subject.
v, >vs, >v, so that the l side is low and the light receiving element S6 side, which receives reflected light from a close object, is high.
, lI>--> Via, also vsh>vah>...>
It is set like vo. This was determined in consideration of the fact that the intensity of reflected light from a distant object is generally lower than that from a close object. According to this, even if the amplification factors of the first and second stage operational amplifiers are kept constant, it is possible to obtain a good detection function for reflected light from a subject with an average reflectance such as human skin. I can do it.

The comparators 31a, 31b, 32a, 32b, .
..., signal output A of I (signal or L signal) appearing at the output terminal of 36a 111. AHI, Az@, ...
-A& is input to the AF control circuit 21. The AF control circuit 21 is configured as shown in FIG. 6, and has signal outputs A,...
Amb-t, D-flip-flop circuits FF, ..., FF0 (hereinafter referred to as
It is input to the clock terminal of FF□, FF, etc. via an AND gate.

This AF control circuit 21 includes the above-mentioned FF, ..., FFob.
In addition, there is a reset pulse generating circuit 43 which outputs a reset pulse after a certain period of time after applying the power supply ■Cc. A counter 45 that counts clock pulses supplied from the microcomputer 22. A shift register 48 and the like receives signals from a decoder 46°FF, . We are prepared.

FIG. 7 shows the circuit configuration of the strobe drive circuit 18. This strobe drive circuit 18 includes a distance measuring discharge tube 3,
It controls the operation of both the discharge tube 17 for photographing and the discharge tube 17 for illuminating the subject with auxiliary illumination light during photographing. Capacitor C1, Cz
is for supplying luminous energy to each of the discharge tubes 17.3, and is charged via the booster circuit 49. A switch device ff50 is connected in series to one capacitor C. This switch device 50 is turned on when an H signal is input from the microcomputer 22 to the terminal T&, and turned off when an L signal is input. Note that when the semiconductor switch shown in FIG. 8 is used as the switch device 50, when charging the capacitor C, H is applied to the terminal
It becomes unnecessary to keep giving signals. Further, each terminal T, , T, , T3 . provided in the strobe drive circuit 18 is provided.
T.

8TS are respectively an oscillation start signal input terminal of the booster circuit 46, an oscillation prohibition signal input terminal, a charging completion signal sending terminal of the capacitor C2, a light emission trigger signal input terminal of the photographing discharge tube 17, and a light emission trigger of the distance measuring discharge tube 3. Used as a signal input terminal.

The operation of the distance measuring device configured as described above is as follows. For example, when the power switch is turned on by opening the lens force bar, the booster circuit 49 shown in FIG. 7 is activated and the capacitor C2°Cz is charged. The preparation for photographing is completed by inputting the charge completion signal of the capacitor C2 to the microcomputer 22.

When the power switch of the distance measuring device is turned on at the beginning of the pressing operation of the shutter button (not shown), the AF control circuit 21
Power supply VCC is applied to. ■This power supply. After waiting for the stability of the AND gate 44, a reset pulse is output from the reset pulse generating circuit 43 shown in FIG.
The FF for opening/closing control is reset, an H signal appears at the Q terminal, and the AND gate 44 is opened. Further, at the same time, the counter 45 is reset.

After a delay of 100m5ec from turning on the power switch of the distance measuring device, the microcomputer 22 starts the AP control circuit 2.
Outputs a clock pulse to 1.

During this 100m5ec delay, each comparator 31a, 31b, 32a of the signal processing circuit 20.

The reference voltages □ and vo applied to 32b, . . . , 35a, 35b, 36a are stabilized, etc.

A clock pulse from the microcomputer 22 is supplied to a counter 45 through an AND gate 44. A decoder 46 is connected to the counter 45.
controls the distance measurement sequence in accordance with the clock pulse count value of the counter 45.

The decoder 46 is an FF□ for latching the signal outputs A□ and Ao from the signal processing circuit 20.

A reset pulse 51g4 is output to FF-b. Thereafter, the decoder 46 outputs the first trigger signal to the IRED drive circuit 19. As a result, the I RED 15 lights up for a predetermined period of time, projects near-infrared light onto the subject, and distance measurement in the macro range is started. After a predetermined period of time after the first trigger signal is output, the decoder 46 outputs a read pulse 51g5 having a pulse width of about the same time. This read pulse is input to one terminal of an AND gate connected to each clock terminal of FF, . . . , FFeb.

A signal processing circuit 18 is connected to the other terminal of the AND gate.
comparators 31a, 31b, respectively.

Since the output ends of 32a, 32b, --, 35a, 35b, and 36a are connected, while the read pulse is at H level, the binary signal output A of L signal or H signal is output.
1111. A@> is supplied to FF, , FF, . When the subject exists within the macro range, H
Since a signal will appear, the FF corresponding to this is set.

Note that when the reflected light from the subject is strong, the comparators 31a and 32 to which the higher reference voltage V□ is applied
The output terminals of a, ++, and 36a also contain H signals.

After the read pulse is output - after a certain period of time has elapsed, rONloF of the shift register 48 is output from the decoder 46.
An H signal is output to the FJ terminal by 51g2. Further, this H signal causes the AND gate 55 to be in an open state. Therefore, the clock pulse inputted to the rCK (clock) terminal of the shift register 48 via the AND gate 44 also passes through the AND gate 55 and is supplied to the microcomputer 22 as a ranging clock pulse.

When a clock pulse is supplied to the rCK terminal with an H signal input to the rON10FF J terminal of the shift register 48, this clock pulse is sent to the shift register 4.
Acts as a shift pulse to sequentially move the data stored in each of the 8 bit positions to the next bit position. Then, from the shift register 48 that stored the Q terminal output from FF, , FF, for each bit position,
Signal output A 6 B and signal output A. are transferred to the microcomputer 22 as ranging data maintaining the bit position arrangement in the shift register 48, that is, signal output A. Among them, A4. Only H signal and F
F.

If only is set, the microcomputer,
22, the first ranging data of roooiooJ is transferred.

Note that when the H signal Sigl from the decoder 46 is input to the D8 terminal of the shift register 48, the shift register 4
8 are comparators 31a and 32a.

..., signal output A from 36a. That is, FF.

In place of the data from comparators 31b, 32b,
..., signal output A11b from 35b, that is, F
F. Ingest data from. For example, signal output A. Among them, Aah and /ksb are H signals,
When F F 4b, F, and F sh are set, the second distance measurement data of ro and ootlJ are transferred.

The first and second distance measurement data transferred in this way include a flag D7 for identifying whether it is macro range range measurement data or normal range range measurement data, and a signal output A□.
A flag D8 is also added to identify which category of Ao the data belongs to. - After a predetermined number of shift pulses are thus input to the shift register 48, - an H signal Si indicating completion of distance measurement in the macro range is sent from the decoder 46 to the input terminal of the Nant gate 56.
g6 is supplied. Since the H signal from the OR gate 52 is applied to the other side of the Nant gate 56, when the H signal is output from the decoder 46, the L signal appears at the output terminal of the Nant gate 56. This L signal is the AND gate 5
When an H signal - is inputted to the set terminal of FF via the 7° inverter 58, FFo is set and the AND gate 44 is closed. As a result, the clock pulse is cut off, the counter 45 also stops counting, and the distance measurement sequence in the macro area is completed.

When the distance measurement data is obtained by distance measurement in the macro range, the microcomputer 22 determines the second lens set position from the first distance measurement data obtained by the signal output A11b, as shown in the flowchart of FIG. ,, also signal output A. The second lens set position is determined from the second distance measurement data obtained by.

For example, if the first distance measurement data is "roooloo", "n2" in FIG. 4 is determined as the second lens set position, and if the second distance measurement data is [00011J],
"n,"- is determined as the second lens set position, giving priority to the short distance side.

Note that during distance measurement in the macro range, the subject is irradiated with a spot-shaped light beam, so the light receiving element St-3
The reflected light does not enter three of the 6 light receiving elements, but the reflected light enters up to two light receiving elements at most. Therefore, by prioritizing the photoelectric output from the light receiving element on the short distance side, the first. From the second distance measurement data, simply select the first distance measurement data. The second lens set positions can be associated.

Thus, the first. Once the second lens set position is determined,
Based on these lens set positions nz J and -n+ J, the microcomputer 22 determines which lens set position is suitable as the final lens set position. When making this judgment, a high reference voltage V am
Comparators 31a, 32a, 33a, − are given
- the lens set position corresponding to the distance measurement data obtained through n, the lens corresponding to the distance measurement data obtained through the comparators 31b, 32b, 33b, etc. to which a low reference voltage vfib is applied. When the set position is nb, (i) nb≦n, -2J→nb (il) nb -na I J →naGiD
ns ””nb J →nlI (nb)Gv
) rnt, >n, J → error handling (V)
The final lens set position is determined by the condition n a = l J → nb.

The above condition (i) means that the reflected light from the background is ignored and priority is given to the lens set position nb on the short distance side where the depth of focus is shallow and the probability that the main subject is located is high.
In addition, condition (ii) is determined to include the influence of low reflection light that tends to appear adjacent to strong reflection light from the subject, that is, the influence of ri 1:# stoke, and that the lens set position n1 This means that priority is given to set position n.

In addition, condition Gv) is a state that cannot occur theoretically,
In this case, a processing sequence is executed to process the error, such as displaying an error in the finder or automatically re-measuring the distance. Furthermore, in the case of the condition that the lens set position nm corresponds to a close distance), the lens set position nb determined based on low reflected light from the subject is determined as the final lens set position.

Therefore, as mentioned above, the first. The second distance measurement data are "roooloo" and "r00011", respectively, so that the first... The second lens set position is nz J, n+ respectively.
J, the final lens set position is determined as "nt" according to condition (ii).

By the way, as a result of distance measurement in the macro range, the signal output A
, @, When none of Afib contains an H signal and none of FF, , FF, and b are set, the OR gate 52 does not output an H signal, so the output of the Nant gate 56 is H. It becomes a signal and FF0 is not set. In this case, distance measurement is continued in the normal range.

During distance measurement in the normal range, a 11 signal is supplied from the microcomputer 22 to the terminal T2 of the strobe drive circuit 18, and the operation of the booster circuit 49 is prohibited.

After that, the reset pulse 51g4 from the decoder 46
As a result, each of FF, . As a result, the electric charge stored in the capacitor C2 causes the discharge tube 3 to emit light. After the second trigger signal is output, the counter 45
When clock pulses for a certain period of time are counted by the decoder 46, a read pulse 51g5 with a predetermined pulse width is output, and the signal outputs A□ and Ao are
ゎ,, latched to FFab.

After distance measurement in the normal range is thus performed, the U signal Sig2 is output from the decoder 46 to the rON10FFJ terminal of the shift register 48. This 11 signal causes the clock pulse to pass through the AND gate 55 and be supplied to the microcomputer 22 as a ranging clock pulse.

As in the case of distance measurement in the macro range, the ro of the shift register 48
By inputting an H signal to the bloFF terminal and supplying a clock pulse to the rCKJ terminal, the shift register 4
8, the first distance measurement data by the signal output Afi,
Signal output A. The second distance measurement data is transferred to the microcomputer 22.

After a predetermined number of shift pulses are input to the shift register 48 in this way, the decoder 46 outputs the AND gate 5.
A signal 51g7 indicating that the distance measurement sequence is completed is supplied to the input terminal of 7. As a result, an L signal appears at the output terminal of the AND gate 57, which is passed through the inverter 58 and turned into an FF as an H signal'. is input to the set terminal of Then, by setting the FF, the AND gate 44 is closed, and the ranging sequence is completed.

By measuring distance in the normal range, for example, ro as the first distance measurement data.
lloooJ (FF!a, FF3M set II
), ro 1110J (F F
t-, FF sh, FF 4- are set)
Once obtained, the microcomputer 22 compares the AF table 28 and determines the first .
Determine the second lens set position. As shown in the AF table 2B of FIG. 1θ, when determining the lens set position in the normal range, the subject brightness information (EV value) detected by the photometry circuit 25 is also referred to.

Now, if it is rEVlj+, the first distance measurement data is the light receiving element S2. Since this means that the reflected light has entered S3, the second
"N7" is obtained as the lens set position. moreover,
Regarding the second distance measurement data, when light is incident on three or more light receiving elements, two on the short distance side, that is, S3. S4
Since the signal given by is given priority, NsJ is obtained as the second lens position.

The first in the normal range. 2nd distance measuring lens set position Nil J
-Nh J is obtained, as in the case of determining the lens set position in the macro area, (i) Nb≦N m
2 J→Nh (ii) Nb = Na −I J→N.

6ω N a = N h J → N-(Nb )6
Intimidation r p4 b > N * J → error handling (
v) The final lens set position is determined according to the condition N m = l J →Nh. In the above case, since the second lens set position is two or more steps closer to the second lens set position,
The final lens set position will be determined as "N5".

Of course, by increasing the data in the AF table 28, the lens set position can be determined not only by prioritizing only the two light receiving elements on the short distance side as described above, but also by considering the output from other light receiving elements. It can also be done.

As a result of distance measurement in the normal range, if the first distance measurement data is rooooootJ, that is, only F F is set, the final lens set position is rH.
, 1. This is because when the first ranging data in the normal range is "roooool", it should originally be detected by any of the light receiving elements during ranging in the macro range. In such a state, the comparator 31 assumes that the reflected light intensity is high during distance measurement in the macro range.
b.

This is likely to occur when the reference voltage vllb of 32b, . . . , 36b is increased. In other words, if the reference voltage Va & is set high in order to reliably discriminate the photoelectric outputs from adjacent light receiving elements, the farthest detection end in the macro area tends to move toward the short distance side, so the above processing is This is effective in resolving such inconveniences.

When the lens set position in the macro range or normal range is determined as described above, the number of drive pulses corresponding to this lens set position is output from the microcomputer 22 to the motor drive circuit 27, and the photographing lens 10 is moved. be done. When the movement of the photographic lens 10 is completed, the shutter button is automatically unlocked and photographing can be performed. Then, by further pressing the shutter button, an actuation signal is sent from the microcomputer 22 to the shutter drive circuit 24, and the program shutter 23 opens and closes at an aperture corresponding to the EV value to take a picture.

Incidentally, the aforementioned AF table 28 also stores control data for the built-in strobe 17 that provides auxiliary illumination to the subject, that is, light emission timing data for the built-in strobe 17, as indicated by a broken line. When the lens set position is determined by the data surrounded by the broken line in the AF table 28, the microcomputer 22 controls the shutter drive circuit 24 until the aperture diameter of the program shutter 23 reaches the aperture diameter memorized in the AF table 28. When the actuation pulse is output to , the microcomputer 22 outputs a trigger pulse to the terminal T4 of the strobe drive circuit 18. As a result, the discharge tube 17 emits light when the program shutter 23 has an aperture diameter corresponding to the subject distance.

In addition, when distance measurement data is obtained by performing distance measurement in the macro range, as shown in the flowchart in Figure 11, distance measurement is completed simply by emitting light from the IRED 15, and the capacitor C2 is charged. The charge is conserved as is. In this case, an L signal is output from the microcomputer 22 to the terminal T6 of the strobe drive circuit 18, so that the switch device 50 connected in series to the capacitor C is turned off. Therefore, when photographing in the macro range when the subject is low and strobe photography is performed, the trigger signal input to the terminal T4 of the strobe drive circuit 18 causes the discharge tube 17 to emit light due to the charge in the capacitor C2, which is stored in the capacitor C2. The generated charge is preserved as is.

In this case, the capacitance of the capacitor C2 is smaller than that of the capacitor C2, and the amount of light emitted from the discharge tube 17 is also smaller.
By correspondingly increasing the opening diameter of the program shutter 23, the timing of light emission from the discharge tube 17 can be determined accurately. Of course, when distance measurement data is obtained by normal distance measurement, terminal T,
Since the [■ signal is applied and the switch device 50 is turned on, the discharge tube 17 is discharged by the capacitor C, and normal strobe photography is performed.

In the embodiments described above, since a spot-shaped light beam is projected by I RED l 5 during distance measurement in the macro range, the lens set position is made to correspond to each light receiving element. In consideration of the fact that the depth of field becomes shallow, the final lens set position may be determined in consideration of subject brightness information, as in the AF table 28 described above.

〔Effect of the invention〕

As described above, according to the present invention, two types of high and low reference voltages are applied to each of the light receiving elements that receive reflected light from the subject. Connect the second comparator and
．． By combining the inverted signals from the second comparator group, the first. A second ranging signal is obtained, and a first ranging signal is obtained corresponding to the second ranging signal. The lens set position is selected depending on whether the difference between the second lens set positions satisfies a predetermined condition. Therefore, even if there is a level difference in the intensity of reflected light incident on the light receiving element depending on the type of subject, it is possible to focus on the main subject with high probability.

Furthermore, even when the reflected light from the subject is accompanied by a halo, or when the intensity of the reflected light is so strong that crosstalk causes photoelectric output to appear on multiple photodetectors, it is possible to accurately capture images without being affected by false signals. Distance measurement can be performed.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. FIG. 2 is a schematic diagram showing an example of a distance measuring system in a normal range used in the present invention. FIG. 3 is a schematic diagram of the distance measuring optical system of the present invention including a macro range. FIG. 4 is an explanatory diagram of the lens set position. FIG. 5 is a block diagram schematically showing the circuit configuration of the distance measuring device of the present invention. FIG. 6 is a circuit diagram showing the configuration of the AF control circuit. FIG. 7 is a circuit diagram showing the configuration of a strobe drive circuit. FIG. 8 is a circuit diagram showing an example of a switch device used in a strobe drive circuit. FIG. 9 is a flowchart showing processing during distance measurement. FIG. 10 is a conceptual diagram showing an example of an AF table. FIG. 11 is a flowchart showing processing during strobe photography. FIGS. 12(A) and 12(B) are explanatory diagrams showing a light incident pattern on a light receiving element and a photoelectric output from the light receiving element, respectively. 2... Light projecting section 3... Discharge tube (for distance measurement) 7... Light receiving section 9... Light receiving sensor Sl-36... Light receiving element lO... Photographing lens 15... I RED 17... Discharge tube (for photography) 31a, 31b, ++, 36a -- Comparator 38.
・Voltage divider FF, FF, &...D-flip-flop circuit. ((((M

Claims (2)

[Claims] (1) In a camera distance measuring device in which light reflected by a subject out of the luminous flux projected from a light projecting means is received by a plurality of light receiving elements arranged in the baseline length direction, each of the light from the plurality of light receiving elements is The photoelectric output of is inputted to a first comparator to which a high reference voltage is applied and a second comparator to which a low reference voltage is applied, and a first distance measurement is performed by combining the inverted signals from the first comparator group. signal and a second distance measurement signal that is a combination of the inverted signal from the second comparator group, and the lens set position corresponding to the first distance measurement signal is higher than the lens set position corresponding to the second distance measurement signal. 1. A distance measuring device for a camera, characterized in that when the distance is more than a predetermined value, the lens set position is determined based on a second distance measuring signal. (2) When the lens set position based on the first distance measurement signal is farther than the lens set position based on the second distance measurement signal by less than a predetermined value, the lens set position is determined based on the first distance measurement signal. A distance measuring device for a camera according to claim 1, characterized in that: