JPS60214321A - Automatic focus adjusting device - Google Patents

Abstract

PURPOSE:To prevent malfunction due to noise and to make an accurate and stable focus adjustment with small power consumption by shortening the longest time of one measurement period when the movement of an optical system to an infinite distance end is detected. CONSTITUTION:When a lens barrel moves to the infinite distance end and a switch 3Q is turned on, AND gates 85 and 88 are closed and AND gates 86 and 87 are opened. Then, the output Q1 of a counter 12 and the output Qh of a counter 15 are used instead of normal outputs Qn and Qm. Therefore, the longest integral time is short when the switch 3Q is on and an integration and a light emission stop period becomes long. Consequently, such malfunction that flip-flops 91 and 92 are triggered with a noise component and the lens barrel moves is prevented and the occurrence probability of malfunction per unit time is lowered because of the prolongation of the integration and light emission stop period. Simultaneously, energy saving effect is improved more in an area close to the limit of distance measurement as a result of the shortening of the measurement time and the extension of the light emission stop.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to an automatic focusing device, and more specifically, the present invention relates to an automatic focusing device, and more specifically, detects the amount of shift in the focal position of an optical system as a difference between output signals of two systems of light receiving means. The present invention relates to an automatic focusing device that moves an optical system in response to a positional shift of the focal point, and stops moving the optical system when the difference between the signals L, X, and the above signals is within a predetermined focusing range.

[Prior Art] In recent years, the automation of operations in various photographic devices has progressed rapidly, and in particular, various systems have been proposed for automatic focus adjustment devices. A system as shown in FIG. 1 is known as one of the conventional active automatic focusing mechanisms.

In FIG. 1, the reference numeral LO denotes a photographing lens barrel of a camera, which is moved by a driving means such as a motor along an optical axis o-o'4. Two lenses L1 and L2 are arranged on both sides of the lens barrel LO, and a light source I, a photodiode DA, and a photodiode DB are provided at the rear of these lenses, respectively. The photodiodes DA and DB are moved in a direction substantially perpendicular to the optical axis 0-0' in conjunction with the movement of the lens barrel LO.

In the above configuration, automatic focus adjustment is performed as follows.

Light from a light source I is irradiated onto a subject Z on the optical axis o-o' via a lens Ll, and its reflected light is guided onto two photodiodes DA and DB via a lens L2.

Since the light from the light source I is emitted at a constant irradiation angle, the position of the reflected light from the subject Z in the direction perpendicular to the optical axis 〇-〇'' at the photodiode position changes depending on the distance to the subject Z. Therefore, If the interlocking of the lens barrel LO and the two photodiodes is adjusted so that when the lens barrel LO focuses on the subject, an equal amount of reflected light will return onto the two photodiodes DA and DB. Focus adjustment can be performed automatically by checking the outputs of the photodiodes DA and DB.

With the conventional active automatic focusing mechanism described above, if the subject is far away or if there is a light source in front of the camera that disturbs the signal light from the light source, the S/N ratio of the amount of reflected light detected by the photodiode will decrease. This has the disadvantage that the focus gets worse and normal focus adjustment cannot be performed.

If the signal-to-noise ratio is poor, the lens barrel may move due to ambient light even though the focus has been established and the camera or subject has not changed position, causing the lens barrel to move out of focus or change the size of the image. Sometimes it was unsightly.

Furthermore, many of the conventional automatic focusing devices as described above are configured to measure the amount of light received by a photodiode using an integral method. FIG. 2 shows changes in the integral value over time when the amount of received light is measured using the integral method. In such a device, the integral value is reset every measurement period formed when the integral value of one photodiode reaches a predetermined value, and the same measurement cycle is repeated one after another. During this measurement operation, the light source is constantly emitting light as shown in the figure. Keeping the light source emitting light all the time in this way leads to an increase in power consumption, and in portable devices such as cameras, the power supply section inevitably becomes large, which is very disadvantageous.

[Purpose] The present invention has been made in view of the above points, and it is possible to perform automatic focus adjustment reliably even when there is ambient light or when the subject is relatively far away, and the power consumption of the light emitting unit is low. The purpose of the present invention is to provide an automatic focus adjustment device that can be used in various ways.

[Example] Hereinafter, the present invention will be described in detail based on the example shown in the drawings. However, among the configurations described below, the lens barrel LO of the camera and the photodiodes DA and DB for detecting reflected light
The interlocking mechanism has the same structure as that shown in the conventional example shown in FIG.

FIG. 3 shows the circuit configuration of the automatic focusing device of the present invention, and in the figure, reference symbols DA and DB indicate photodiodes arranged in parallel for detecting reflected light. The outputs of photodiodes DA and DB are amplified by amplifiers IA and IB, respectively, and sent to filters 2A and 2B, respectively.

On the other hand, the light source I is driven by the oscillation frequency of the reference oscillator 13 via the light emission control section 14 including a driver. This frequency is selected to be different from the frequency of the commercial power supply that turns on indoor light sources to prevent disturbances.

Therefore, the filters 2A and 2B are set to pass only the signal in the emission frequency range of the light source I. The outputs of the filters 2A, 2B are input to integrators 4A, 4B via electronically controlled switches 3A, 3B, respectively.

The integrators 4A and 4B are constituted by an integrating circuit using a known operational amplifier or the like, and their integrating capacitors can be reset by switches 4C14D, respectively.

Output voltage VA of integrator 4A is input to child terminals of comparators 5AH and 5AL. Further, the output voltage VB of the integrator 4B is input to the ten terminals of the comparators 5BH and 5BL.

- One terminal of the brave comparator is supplied with a threshold voltage obtained by dividing the power supply voltage by resistors R1 to R5 connected in series. Comparators 5AH and 5BH are supplied with voltage VH at the connection point of resistors R1 and R2 as a threshold voltage. Comparators 5AL and 5BL have a voltage VL at the connection point of resistors R2 to R3 or resistors R3 to R4.
, VL' is supplied. This selection is made by switch 3C as described later. These voltages VH, VL, and VL' are determined according to the required focusing accuracy as described later. Ru.

The output of the comparator 5AH15BH is connected to the input of the OR game) 61. The output of the OR gate 61 is input to the OR gate 62, and the flip-flop 91
．． 92 is triggered. or gate 62
The output Qn of the counter 12 is input to the other input.

The output of the OR gate 62 is a mono multi-by-break MMI
It is designed to trigger. That is, when either of the comparators 5AH15BH becomes high level, a high level pulse is output from the OR gate 61.62, and this pulse triggers the mono multivibrator MMI and the flip-flop 91.92.

The output of mono multivibrator MMI is inverter 71
, a delay circuit DLI consisting of a similar mono-multivibrator, etc., and an OR gate 63. The inverter 71 and the mono-multivibrator MMI are located in the block 20 indicated by the broken line, and entry and exit from the block 2o are performed through three connection points A to C shown in the figure.

The output of the inverter 71 controls the switches 3A, 3B and the light emission control section 14. switch 3A
, 3B are opened by a low level input, and the light emission control section stops the light emission of the light source I by the same low level input.

The outputs of comparators 5AL and 5BL are applied to data inputs of flip-flops 91 and 92, respectively. The outputs of these flip-flops 91, 92 are connected to the motor control circuit 10.

The motor control circuit 10 moves the motor 11 that drives the lens barrel LO in two different directions in response to the high level outputs of the flip-flops 91 and 92. This direction of rotation is aligned in advance in a direction in which the amounts of light input to the photodiodes DA and DB are equal, depending on the amount of light input to the photodiodes DA and DB.

Further, the re-outputs of the flip-flops 91 and 92 are connected to a two-manual AND gate 81, and the output of the AND gate 81 is connected to the control input of the switch 3C. Switch 3C is always connected to the left side of the figure, and the
) 81 is at a high level, it is switched to the terminal on the right side of the figure.

On the other hand, the output of the OR gate 63 is connected to the reset terminal of the counter 12. This counter 12 is configured to increment when the output of the reference oscillator 13 falls, and a clock pulse output from the reference oscillator 13 is connected to one input terminal of an AND gate 84. The output of this AND gate 84 is connected to the remaining inputs of the OR gate 63. The output of the counter 12 is connected to the other input of the AND gate 84.

The output Qn of the counter 12 is a flip-flop 91.92
and is connected to the remaining inputs of the OR gate 62.

Next, the operation of the above configuration will be explained in detail.

The photodiodes DA and DB output according to the amount of light received, and of this output signal, only the emission frequency component of the light source I is extracted by filters 2A and 2B, respectively, and sent to an integrator 4A via normally closed switches 3A and 3B. , sent to 4B. As shown in FIG. 4, the output voltage of each integrator increases from the start of measurement according to the amount of received light.

Here, a case will be considered in which the output voltages of the integrators 4A and 4B increase as indicated by symbols VA and VB' according to time t.

In this case, since the amount of light received on the photodiode DA side is large,
First, at time T, the integrated voltage VA is applied to the comparator 5AH.
reaches the threshold value VH. This causes comparator 5
AH is inverted, a high level is output from the OR gate 61, and the flip-flops 91 and 92 are triggered. At this time, the data input of the flip-flop 91 is at a high level because the voltage VA has already exceeded the threshold value VL of the comparator 5AL as shown in FIG. Further, the data input of the flip-flop 92 is at a low level since the voltage VB' has not yet reached the voltage VL at this point.

Therefore, depending on the trigger of each flip-flop, the flip-flop 91 goes high level, and the flip-flop 92 goes high level.
outputs low level.

As a result, the motor control circuit 10 is connected to the photodiode DB.
The motor 11 is driven to move the lens barrel and each photodiode so that the amount of light received is increased. Even when the amount of received light is reversed, the lens barrel is moved in the opposite direction by the same operation.

Further, at the same time as the flip-flops 91 and 92 are triggered, the mono multivibrator MMI is also triggered by the output of the OR gate 62. A pulse having a length determined by the connected resistor R5 and capacitor C1 is output from the mono-multivibrator MMI. This output pulse disconnects the integrators 4A and 4B via the inverter 71, and after the delay time set in the delay circuit DLI has passed, D
Switch 4C14D is closed via LI to short-circuit the integrating capacitor of each integrator and initialize the integral value. Also, due to the same pulse, the counter 12 also outputs the OR gate 6.
3.

The output of mono multivibrator MMI is inverter 71
is inverted and input to the light emission control section 14. Therefore, light emission from the light source I is stopped while the output of the mono-multivibrator MMI is at a high level. When the mono-multivibrator MMI outputs a low level after the time determined by the resistor R5 and the capacitor C1 has elapsed, the light source I starts emitting light again, and a new measurement is started. That is, after the measurement is completed, the measurement is stopped by the output pulse width of the mono-multivibrator MMI, and during this period, the light emission from the light source I is also stopped.

The counter 12 is used to set the longest integration time, and is sufficient if it has not yet been reset when a certain number of clock pulses of the reference oscillator 13 are counted after the rest period ends and the reset is released as described above. Assuming that the measurement light amount cannot be received, a short pulse is generated and the OR gate 62
A pulse is given to trigger the mono-multivibrator MMI, and the same reset operation as above and the light emission stop of the light source are performed. At the same time, it resets its own count value via the AND gate 84 in synchronization with the clock pulse.

As described above, each time the measurement period by the photodiode ends, the measurement and the light emission operation of the light source I are stopped for the time set in the mono-multivibrator MMI, so power consumption is reduced by the length of this pause period. be able to. Therefore, it is possible to make the power supply unit smaller than before or to extend the life of the battery of the power supply.

On the other hand, when each integral value increases with signs VA and VB, both comparators 5AL and 5BL have already been inverted when voltage VA reaches voltage VH, so the outputs of flip-flops 91 and 92 are both Become a high level. As a result, the motor control circuit 10 and the motor 11 are stopped, and the movement of the lens barrel is stopped. Therefore, when the output integral value of either photodiode DA or DB reaches the voltage VH and the other integral value is equal to or higher than the voltage VL, it is determined that the image is in focus.

At this time, if the subject is far away, the reflectance of the subject is poor, or there is a light source that disturbs the signal light, the signal-to-noise ratio of the signal input to the photodiode will deteriorate, and the integrated voltage will change. The amount of error included becomes larger. There may also be a case where one of the integrated values becomes equal to or less than the threshold voltage VL, as in the case of symbol VB' in FIG. 4, even though a focused state is formed. In such a case, conventionally it would be determined that the focus was out of focus and the lens barrel would be moved, resulting in cameras such as video cameras or single-lens reflex cameras being out of focus or having a large image even though they were once in focus. It was very unsightly as the color changed.

However, in the present invention, the flip-flop 91.9
2 are both set, both inputs of the AND gate 81 become high level, so the switch 3C is switched to the right side in FIG. 3, and the lower threshold of the comparators 5AL and 5BL is changed to an even lower VL'. be done. In other words, the criteria for the in-focus state are expanded. Therefore, in the present invention, once the object is in focus, it is possible to maintain the in-focus state without causing the lens barrel to move due to noise even when there is ambient light or when the subject is far away. Of course, if one of the integral values becomes smaller than VL'' when the flip-flop is triggered, as indicated by the symbol VB'' in Fig. 4, the lens barrel is moved by the same operation as described above, and at this time, the AND gate Since the output of 81 becomes low level, switch 3C is connected to the left side in FIG.

As described above, when focusing, the criteria for determining focus is expanded, malfunctions due to noise can be prevented, accurate automatic focus adjustment can be performed, and stability against disturbances can be ensured. In the above, a measurement circuit in which the integral value increases is illustrated for ease of explanation, but in a measurement circuit in which the integral value is output as a negative voltage, the higher threshold value should be changed. It's okay. In addition, the criteria for determining focus is not limited to two types.
A larger number of values may be selected depending on the amount of light received by the photodiode.

Furthermore, in the above, the measurement is terminated when the integral value reaches a predetermined value, and then the light emission and measurement are suspended for a certain period of time, but more preferably the time interval between the integration start points of the preceding and following integration periods. It is preferable to configure the system so that it is controlled at a constant level.

Specifically, block 20 in FIG. 3 is replaced by block 2 in FIG.
By replacing it with 0', the above operation can be realized.

Block 20' in FIG. 5 has connection points A-D;
These connection points are connected to connection points A-C in FIG. 3, respectively. A clock output from the reference oscillator 13 is input to the connection point. Here is a mono multi vibrator MM
I has been replaced with SR flip-flop 93,
The reset is performed by the output Qm of the counter 15. At the same time, this output Qm resets its own count value. Therefore, the SR flip-flop 93 is cleared at regular intervals, and the light source I, which had been turned off, is turned on again.

FIG. 6 illustrates an integral operation when using the configuration of FIG. 5. Here, t wax is the maximum integration time determined by the counter 12, and tl is the maximum integration time determined by the counter 12.
This is the time determined by the count value of 5.

As shown in the figure, by setting tl > tmax, measurements can be made at regular intervals, and t
The light emitter can be stopped by 1-t wax. When the subject is close, or when strong reflected light can be obtained due to good reflectance of the subject, the measurement can be completed in a shorter time, allowing for a longer time for the light emitter to be stopped, resulting in an energy saving effect. It increases. Furthermore, since the measurement operation is performed at regular intervals, an average focusing operation can be performed.

In other words, in the circuit of FIG. 6, the pause time is determined according to the amount of received light, and as described above, a higher energy saving effect and a stable focus adjustment operation can be obtained.

Furthermore, different embodiments of the present invention are shown in FIG. 7 and below.

show.

Conventional devices had the disadvantage that the motor that moves the lens barrel was driven by noise when the subject was far away and a sufficient amount of reflected light could not be obtained, but the circuit shown in Figure 7 improves this disadvantage. It is something to do. In the circuit diagram of FIG. 7, the same members as those in FIG. 3 are given the same reference numerals, and detailed explanation thereof will be omitted. Further, illustrations of the light receiving circuit and the threshold control circuit are also omitted here.

The circuit of FIG. 7 differs from that of FIG. 3 in that the control system for the motor 11 is shown in more detail and that blocks 21 and 22' shown in broken lines are added. Light emission stop control is performed by a flip-flop 93 and counter 15 similar to those shown in FIG.

The motor control circuit 10 in the figure is controlled via AND gates 82 and 83. The non-inverted output of flip-flop 91 and the inverted output of flip-flop 92 are input to AND gate 82 , and the inverted output of clip-flop 91 is input to AND gate 83 . And furthermore, one of the input terminals of each ant game) 82.83 is a resistor R.
It can be controlled to O potential by 5, R6 and switches 3P and 3Q.

In this circuit, both flip-flops 91 and 92 are set, that is, when a focus judgment is made, one of the input terminals of each AND gate 82 and 83 is set to low level, and the motor control circuit lO Rotation of motor 11 is stopped. The motor 11 is rotated in that direction only when only one of the flip-flops is set. Therefore, the motor 11 is driven and controlled by the exclusive OR of the two flip-flops.

The switches 3P and 3Q described above are respectively attached to the closest end and the infinitely far end of the lens barrel, and are used to detect movement of the lens barrel to the corresponding positions. When the lens barrel reaches the end of the moving range from closest to infinity, switches 3P to 3Q are pressed.
is closed, stopping further movement of the lens barrel.

The pull-up side of the switch 3Q installed at the infinite end is the AND gate 85 of the block 21, the inverter 73,
and is input to AND gate 88 of block 22.

The output Qn of the counter 12 is connected to the remaining inputs of the AND gate 85 of the block 21.

The output of inverter 73 is connected to one input of AND gate 86 and also to AND gate 87 of block 22.
has been entered. The output Ql of the counter 12 is connected to the remaining inputs of the AND gate 86. Here, it is assumed that the output Ql is an output with a smaller number of measurements than Qn. The logical OR output from the OR gate 64 of the AND gates 85 and 86 resets the counter 12 and flip-flops 91 and 92 through the AND gate 84 and OR gate 63, and sets the flip-flop 93 through the OR gate 62, as in FIG. It is supposed to be done.

On the other hand, the block 22 has a similar structure, and the two outputs Qm and Qh of the counter 15 are selected via the inverter 73 by operating the switch 3Q. Here, the output Qh with the longer measurement time is selected by turning on the switch 3Q.

However, it is assumed that Qm>Qn.

In the above configuration, when the lens barrel moves to the infinite end and switch 3Q is turned on, AND gates 85.88 close and AND gates 86.87 open. As a result, the output Ql of the counter 12 and the output Qh of the counter 15 are used instead of the normal outputs Qn and Qm, respectively.

Therefore, while the lens barrel is at the infinite end and the switch 3Q is on, the maximum integration time is short, and the integration and light emitter stop periods are lengthened. This prevents malfunctions in which the flip-flops 91 and 92 are triggered by noise components and moves the lens barrel, and the probability of occurrence of malfunctions per unit time is reduced by extending the integration and light emitting body stop periods. At the same time, by shortening the measurement period and extending the length of time the light emitter stops, it is possible to further enhance the energy saving effect in areas close to the distance measurement limit.

As described above, reliable and stable focus adjustment can be achieved with lower power consumption.

The embodiment of FIG. 7 counts the length of the measurement pause period 15.
Although it is determined by the gates 65, 87, and 88, the present invention can be similarly implemented in a configuration in which the measurement pause period is determined by a mono-multi-by-break as shown in FIG. , FIG. 8 shows an embodiment constructed in this manner. , In FIG. 7, the length of the measurement pause period is determined by the monomultivibrator MMI as in the case of FIG. 3, but the time constant of this circuit is determined by the resistors R7, R8 and the capacitor CI.
Determined by. A connection point between resistors R7 and R8 can be connected to a power supply voltage via a switch 3D. This switch 3D is controlled by the terminal voltage of switch 3Q. Since the other configurations are the same as those in FIG. 7, their explanation will be omitted.

According to the above configuration, when the optical system moves to the infinity end,
Switch 3Q is closed, which opens switch 3D. As a result, until then, resistor R8 and capacitor CI
The pulse width of the mono-multivibrator MMI, which was previously determined, is now determined by the resistors R7+R8 and the capacitor C1, and a longer pulse is output.

In this way, the measurement pause period is lengthened by moving the optical system to the infinite end. Further, at this time, the maximum integration time specified by the counter 12 is shortened in the same manner as in FIG. 7, and the same effect as described above can be obtained.

[Effect] As is clear from the above description, according to the present invention, the amount of deviation in the focal position of the optical system is measured as the difference between the output signals of the two systems of light receiving means, and the amount of deviation in the focal position of the optical system is In an automatic focusing device that moves the optical system according to the signal and stops moving the optical system when the difference in the signals is within a predetermined focusing range, a detection means attached to the infinite end of the optical system detects the optical system. Since the camera adopts a configuration in which the maximum time of one measurement period is shortened when movement toward the infinite end is detected, malfunctions due to noise in areas near the distance measurement limit on the infinity side can be prevented. It is possible to provide an excellent automatic focus adjustment device that can perform accurate and stable focus adjustment with low power consumption.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the principle of an active type automatic focusing device, FIG. 2 is a diagram explaining the operation of a conventional automatic focusing device, and FIG. 3 is a diagram showing the configuration of an automatic focusing circuit of the present invention. 4 is a diagram explaining the operation of the circuit in FIG. 3, FIG. 5 is a circuit diagram showing a partial modification of FIG. 3, and FIG. 6 is an operation in the circuit in FIG. 5. FIG. 7 is a circuit diagram showing a further different embodiment of the present invention, and FIG. 8 is a circuit diagram showing a further different embodiment of the present invention. IA, IB...Amplifier 2A, 2B...Filter 3
A, 3B, 3P, 3Q...Switch 4A, 4B...
Integrator 5AH55BH15AL, 5BL...Comparator 1
0...Motor control circuit 11...Motor 12.15
...Counter 13...Reference oscillator 14...Light emission control unit 61-65...OR gates 81-86...
AND gates 91 to 93...Flip-flop■...Light source DA, DB...Photodiode MM
I...Mono multi-vibrator patent applicant Kowa Co., Ltd. Figure 1 Figure 2 Procedural amendment (automatic) June 12, 1980 To the Commissioner of the Japan Patent Office 1, Indication of the case 1982 Patent Application No. 70991 2, Name of the invention Automatic focus adjustment device 3, Relationship with the case of the person making the amendment Patent applicant name Kowa Co., Ltd. 4, agent Telephone: 03 (268) 2481 (Iri 5, Contents of the amendment to the drawings to be amended 1) Specification No. ``Hikaru Genko no'' in the 7th line of page 3 is changed to ``Hikaru Genko''
Correct. 2) In the 9th line of page 4, ``due to ambient light'' is corrected to ``due to ambient light, etc.''. 3) rRl-R5J on page 7, line 3 of rR1 to R4
” is corrected. 4) Correct "as described later" from line 9 to line 1θ of the same page to "as described later." 5) In the 6th line of the same page, replace “determined.” with “determined.”
Correct. 6) Correct "R5" in the 5th line of page 12 to "R9". 7) "Figure 6" on page 18, line 8 of the same page is corrected to "Figure 5." 8) Correct r22'J in the 5th line of page 19 to "22". 9) Correct "Figure 6" in the 6th line of the same page to "Figure 5." 10) Correct "Counter 12," on the 8th line of page 21 to "Reset counter 12." 11) Correct "integration" in line 10 of page 22 to "reduction of longest integration time". 12) Change “Count” from line 6 to line 19 of the same page to “
Correct to "counter". 13) On page 23, line 4, "Figure 7" is corrected to "Figure 8." 14) "r81-86" on page 25, line 17 of the same page as r81
~88''. 15) In the figure, correct Figure 3 as shown in the attached sheet.

Claims (3)

[Claims] (1) The amount of deviation in the focal position of the optical system is measured as the difference between the output signals of the two systems of light receiving means, and the optical system is moved according to the measured deviation in the focal position. In an automatic focusing device that stops moving the optical system when it is within the focusing range, one measurement period occurs when movement of the optical system to the infinite end is detected by the detection means attached to the infinite end of the optical system. An automatic focus adjustment device characterized in that the maximum time of . (2) The automatic focus adjustment device according to claim 1, wherein a measurement pause period for each measurement period is extended by detecting movement of the optical system toward an infinity end. (3) The automatic focus adjustment device according to claim 1 or 2, further comprising means for controlling the time interval between the starting points of the measurement period to be always constant.