JPS62153705A - Range finder - Google Patents

Abstract

PURPOSE:To shorten the time required in range finding, by investigating the change of a monitor signal to allow an illumination means to emit light only at the time of the charge accumulation of a charge accumulation type light receiving element when an object is dark. CONSTITUTION:The light from an object transmitted through a lens is received by a charge accumulation type light receiving element 1 and a monitor light receiving element 3 and range finding is performed in a range finding means 2 on the basis of the output signal of the light receiving element 1. A monitor signal changing in the inclination corresponding to the light receiving element 3 is formed on the basis of the output signal of the light receiving element 3 by a monitor signal forming means 4 and the change of the monitor signal is investigated by a monitor signal monitor means 5 to judge whether the object is dark. When the object is dark, a control means 6 allows an illumination means 7 to emit light only at the time of the charge accumulation of the light receiving element 1 on the basis of the output signal of the monitor signal monitor means 5 to illuminate the object. By this method, the time required in range finding can be shortened and the consumption of a power source can be reduced.

Description

[Detailed description of the invention] (Technical field) The present invention relates to a distance measuring device used in cameras and the like.

(Prior art) Distance measuring devices using a charge accumulation type light receiving element for illuminating a subject are disclosed in JP-A-57-105710, JP-A-60-46513, and JP-A-60-4651-4. It is known from public notices, etc.

However, in the method described in Japanese Patent Application Laid-Open No. 57-105710, it takes time to take out the output of the light receiving element in order to illuminate the subject, and the distance measurement time becomes long. Also, JP-A-6
In the systems described in Japanese Patent Application Laid-open No. 0-46513 and Japanese Patent Application Laid-open No. 60-46514, distance measurement is performed once when determining whether or not to illuminate the subject, so distance measurement also takes time.

(Objective) It is an object of the present invention to provide a distance measuring device capable of improving the above-mentioned drawbacks and shortening the time required for distance measuring.

(Structure) As shown in FIG.
Distance measuring means 2, monitor light receiving element 3. It has a monitor signal forming means 4, a monitor signal monitoring means 5, a control means 6, and an illumination means 7. The light from the object transmitted through the lens is received by the light receiving elements 1 and 3, and distance measurement is performed by the distance measuring means 2 based on the output signal of the light receiving element 1. Based on the output signal of the light-receiving element 3, a monitor signal forming means 4 generates a monitor signal whose slope changes according to the amount of light received by the light-receiving element 3, and a monitor signal monitoring means 5 examines changes in the monitor signal to make the subject dark. It is determined whether When the subject is dark, the control means 6 causes the illumination means 7 to emit light only when the charge is accumulated in the light receiving element 1, to illuminate the subject based on the output signal of the monitor signal monitoring means 5.

Next, examples of the present invention will be described.

FIG. 2 shows an embodiment of an automatic focus adjustment device to which the present invention is applied. In this embodiment, the photographing lens 11 in the camera is
The light from the object that has passed through the charge-coupled device 12 is imaged by the optical system on the charge-coupled device 12, and the drive circuit 13 drives the charge-coupled device 12. The charge-coupled device 12 has an internal configuration as shown in FIG. 3, and includes photodiode arrays A and B arranged in a row in the left-right direction and a monitor photodiode 14. Photodiode array A, B
The light of the photographing lens 11 is divided into two parts by the axis, a right part A and a left part B, and a monitor photodiode 14 is provided on one side thereof. Figure 4 shows this charge-coupled device 12.
In the timing chart, when the reset pulse φR of the drive circuit 13 is at a high level, the field effect transistor 16 is turned on, the capacitor 18 is charged by the power supply VDD, and the storage electrode 20 is reset. When the reset pulse φR becomes a low level, a photocurrent corresponding to the luminance distribution of the subject image flows through the photodiode arrays A and B, and charges are accumulated in the storage electrode 20. At the same time, a photocurrent flows through the monitor photodiode 14 according to the luminance distribution of the subject image, and the potential of the capacitor 18 decreases due to this photocurrent. The potential of this capacitor 18 is output to the drive circuit 13 via a buffer amplifier 21. When a transfer pulse is manually applied from the drive circuit 13, the shift gate 23 opens and the charge stored in the storage electrode 20 is transferred to the analog shift register 24, and the pulse φ1. φ2
The field effect transistor 25. Video signal VOUT sequentially via capacitor 26 and buffer amplifier 27
is output as

The drive circuit 13 is a buffer amplifier in the charge-coupled device 12.
It includes a circuit as shown in FIG. 5 for processing the output signal VAGC of the l@ device 21. The signal VAGC is passed through a buffer amplifier 28 to a comparator 29 with a resistor 30.31.
It is compared with a comparison voltage Vs of a comparison power supply consisting of. The φT generation circuit 32 receives the output signal of the comparator 29 manually, and
When the output signal of the buffer amplifier 28 becomes equal to the specific lx pressure Vs, a transfer pulse φT is output to the charge coupled device 12. The output signal of the buffer amplifier 28 is still output to the operational multiplier 3.
3. Differential circuit 36 which also includes a capacitor 34 and a resistor 35
When the reset pulse φR is at a high level, the analog switch 37 is turned on and the differentiating circuit 36 is reset.

As shown in FIG. 6, the output signal VA of the buffer amplifier 21
GC is the light received by the monitor photodiode 14.

The monitor signal is a monitor signal that decreases at a slope (rate) proportional to the brightness of the subject to be photographed, and is differentiated by a differentiating circuit 36 to detect the slope and the brightness of the subject to be photographed.

As shown in FIG. 2, in the charge-coupled device 12, the video signal VOUT from the buffer amplifier 27
0 and converted into a digital signal by an analog/digital converter 51, which is input to a microcombinator (hereinafter referred to as CPU) 43 via an interface 52. The output signal of the differentiating circuit 36 and the output signal of the buffer amplifier 21 in the drive circuit 13 are converted into digital signals by the analog/digital converter 51 via the multiplexer 53 and input to the CPU 43 via the interface 52.

Before taking in the video signal from the charge-coupled device 12, the CPU 43 adjusts the gain of the variable magnification amplifier 50 via the multiplexer 54 according to the output signal of the buffer amplifier 21 when the transfer pulse φT is output. Coupling element 12
The defocus amount of the photographing lens 11 is calculated by taking in the video signal which has been amplified by the variable multiplier 50 at a magnification according to the brightness of the subject. Also, the photographic lens 11
The focal length and set position of are input from the detection circuits 55 and 56 to the CPU 43 via the multiplexer 53, analog/digital converter 51, and interface 52,
Pulses from encoder 57 and signals from switches 58 to 60 are input to CPU 43. The encoder 57 constitutes a rotation detector that detects the rotation of the photographing/zooming motor 61, and the switches 58 to 60 are manually operated switches, and the switch 58 is in a manual mode with automatic focus adjustment. Set whether to perform the process or in automatic mode.

The switch 59 is a power switch consisting of a release switch that is turned on when the release button is pressed, and the switch 60 is a switch for setting an adjustment mode. The manual distance setting circuit 62 is a circuit that generates a signal to manually rotate the motor 61, and when the automatic mode is set with the switch 58, the CPU 43 causes the motor drive circuit 63 to rotate the motor 61 based on the calculated defocus amount. When the manual mode is set by the switch 58, the output signal from the manual distance setting circuit 62 causes the motor drive circuit 63 to rotate the motor 61. Also CPU43
Immediately after the charge-coupled device 12 starts integrating (charge accumulation), the output signal of the differentiating circuit 36 is compared with a predetermined value, and if it is smaller than the predetermined value, it is determined that the subject is dark, and the charge-coupled device 12
The projector 64 is turned on only when the charge is accumulated to emit auxiliary light onto the subject. Further, the CPU 43 causes the display device 65 to display in-focus, front focus, rear focus, and distance measurement not possible, and uses the open F value of the photographing lens 11 from the F value circuit 66 to calculate the defocus amount.

FIG. 7 shows the processing flow of the CPU 43.

The CPU 43 starts when the switch 59 is turned on, resets each part to the initial state in step S1, and proceeds to step S1.
In step 2, a release prohibition signal is output to the sequence control section of the camera to prohibit release. Next, in step S3, the signal from the switch 60 is checked, and if the switch 60 is on, the adjustment mode is entered. This mode is set during assembly or service. If the switch 60 is off, the process proceeds to step S4, where the number viφ, the integration flag, and the low brightness flag are reset, and the charge-coupled device 5 is initialized. Next, in step S5, a reset pulse φR is output to the driver 13.

In step S6, the reset pulse φR is turned off to allow the charge-coupled device 12 to perform integration, and at the same time, the timer is started. Next, in step S7, the low brightness flag is checked, and since it has been reset, the process advances to step S8, where the driver 1
3. Define the slope of the monitor signal VAGC by measuring the output signal of the differentiating circuit 36 in step S.3.
In step 9, the output signal of the differentiating circuit 36 is compared with a predetermined value to determine whether the brightness of the subject is low (
(Is it dark?) or not. If the subject is not of low brightness, the process proceeds to the next step SIO, but if the subject is of low brightness, the low brightness flag is set in step Sll, the floodlight 64 is turned on in step S12, and then step SIO is performed.
Proceed to. In step SIO, the output signal of the comparator 47 is determined to be 74W by determining whether or not the output signal has become zero.
It is determined whether or not the integration of the T-coupled element 12 is completed, and even if the output signal of the parenthesis comparator 47 does not become zero, when the timer times up, it is determined that the integration of the charge-coupled element 12 is completed.

If the integration of the charge-coupled device 12 is not completed, step S
6 and repeat steps S6 to S10, but if the object is of low brightness and the projector 64 is turned on, the process jumps from step S7 to step SIO. After that, when the integration of the charge-coupled device 5 is completed, step S13
, the driver 13 outputs the transfer pulse φT to the charge-coupled device 5, the random access memory (RAM) is cleared in step S14, and the analog/digital converter 51 outputs the video signal from the charge-coupled device 5 in step S15. Start analog/digital conversion. Next, in step S16, the low brightness flag is checked, and if it is not set, the process proceeds to step 818, but if the low brightness flag is set, the projector 64 is turned off in step S17 upon completion of charge accumulation in the charge-coupled device 5. Step S18
Proceed to. In step S18, the output signal of the buffer amplifier 21 when the transfer pulse is output is measured, and in step S18, the output signal of the buffer amplifier 21 is measured.
At step 19, it is determined from the signal whether or not the subject image is of low brightness. If the subject image is not of low brightness, the process proceeds to step S21, but if the subject image is of low brightness, the gain of the variable magnification amplifier 50 is set to a large value according to the output signal of the buffer amplifier 21 when the transfer pulse φT is output. After making the change, the process proceeds to step S21. In step S21, the video signal from the charge-coupled device 5 is converted into a digital signal by the analog/digital converter 51, and in step S22, it is stored in the RAM.In step S23, the lens information from the detection circuits 55 and 56 is captured. Take in Siφ and Fφ and set the number Nr to 20.

Next, in step 824, the focal length Fφ of the photographing lens 1 is set to 7.
It is determined whether the focal length Fφ is 75 fins or less, the process proceeds to step S25, the number of distance measurements after the switch 59 is turned on is counted, and it is determined whether this is the first time. If distance measurement is being performed for the first time, the lens 110 setting position Siφ is set to 11 and the number Nr is set to 32 in step 826. This number Nr is determined by fixing each image on the photodiode arrays A and B, which are divided vertically into two by the optical axis of the lens 11 in the charge-coupled device 12, while fixing the comparison range (■) of one of them to a value corresponding to Siφ, and This is the number of photodiodes within ■ in the comparison range when comparing while moving the comparison range ■ to determine how much the image interval has changed from when it was focused. range.

The amount of change in the image interval is determined by calculating the number of photodiode pitches (an integer) using integer part calculation, and calculating the number of photodiode pitches (fraction) less than 1 photodiode pitch using fractional part calculation. Next, in step S27, the integer part is calculated and the photodiode array A is processed.

The maximum value viφ of the number of photodiodes within the matching range is determined by comparing each image in a certain range (Nr) on B, and the amount of change (integer) Mα) in the image interval is determined, and step S
At step 28, it is determined whether the maximum value viφ is 4 or less. If the maximum value viφ is 4 or less, it is determined that distance measurement is not possible, and the display device 65 displays this fact.

If the maximum value viφ is not 4 or less, a fractional calculation is performed in step S29 to obtain a fractional portion Cφφφ of the image interval change amount.

In the second and subsequent distance measurements, the process proceeds from step S25 to step S30, where the lens set position Siφ is set to 11, the integer part M(1) of the image interval change amount is set to 11, and the integer part calculation is performed. Proceed to S29.

Next, in step S31, it is determined whether the number Nφ of video signals from the charge-coupled device 12 that has a large contrast and can be used for data comparison in the fractional part calculation is 2 or less, and if the number Nφ is 2 or less, determines that distance measurement is not possible, and causes the display device 65 to display this fact. If the number Nφ is not 2 or less, in step S32, the amount of deviation Df1 of the image on the charge coupled device 12 from the in-focus position is calculated as Dh = ((Siφ−M(1)) x 64− Cφ
φφ) x Kd, and in step S33, the defocus amount Df2 of the lens 11 is calculated as Df2 = A2 / (Dfl At) + A3
Find it using the following calculation. Next, in step S34, the defocus is measured, and it is determined whether the absolute value of f2 has reached the desired value φ・pφhJ≠＼, and the absolute value of the defocus amount has reached the desired value φ・
If it is less than Fφ, it is determined that the lens 11 is at the in-focus position, and the release is enabled by canceling the release prohibition signal to the sequence control section.

If the absolute value of the defocus amount is not less than the predetermined value φ-Fφ, in step S35, it is determined from the sign of the defocus amount whether or not the motor 61 should be rotated in the normal direction in order to move the lens 11 to the in-focus position. If the motor 61 should be rotated in the normal direction, it is determined in step S36 whether the lens 11 is at an infinite position. The motor 61 rotates in the normal direction to move the lens 11 farther away, and rotates in the reverse direction to move the lens 11 closer, so if the lens 11 is at the infinite position, it is determined in step S37 that distance measurement is not possible and a message to that effect is displayed. Device 6
5, and the motor 61 is stopped in step 838. If the lens 11 is not at the infinity position in step S36, the process advances to step S39 to start a timer, and in step S40 the motor 61 is rotated forward, and in step S41
The pulses from the encoder/coder 57 are counted. Next, in steps 342 to S44, it is determined whether the timer has timed up, whether the lens 11 has reached the infinity position, the pulse count value from the encoder 57, and the defocus f.
It is determined whether the absolute value IDf2-NPI of the difference from fi Df2 has become equal to or less than a predetermined value φ. The timer has timed up, lens 1 has reached the infinity position,
If none of the three conditions of 1Df2-NPI4 raccoon φ is satisfied, the process returns to step S40 to continue normal rotation of the motor 61, and if any one of the three conditions is satisfied, the motor 61 is rotated in step S45. 61 is stopped, and in step S46 it is determined whether the number of times the motor 61 has been driven has reached four times. When the number of times the motor 61 is driven reaches four times, it is determined that distance measurement is not possible, and the display device 6 displays a message to that effect.
If not, the process returns to step 84.

If it is determined in step S35 that the motor 61 should be reversed, it is determined in step S47 whether or not the lens 11 is in the closest position, and if the lens 11 is not in the closest position, a timer is started in step 848. Let me step S
49, the motor 61 is reversed. Next, in step S50, pulses from the encoder 57 are counted, and in step 3
Whether or not the timer has timed up in steps 51 to S53;
Whether the lens 11 has reached the close position, 1Df2-NP
I,! It is determined whether NPφ has been reached. The timer has timed up, the lens 11 has reached the closest position, l Df2-NP l,! If none of the three conditions of becoming a raccoon dog φ is satisfied, step S49
The IC returns to continue the reverse rotation of the motor 61, but if any of the three conditions is met, the process advances to step S54 and the motor 61 is stopped. Next, in step S55, the lens 1
It is determined whether or not the drive circuit No. 1 has reached four times. If the number of times the lens 11 has been driven reaches four, it is determined that distance measurement is not possible, and this fact is displayed on the display device 65; otherwise, the process returns to step S4.

If the lens 1 is at a close position in step S47, it is determined in step S56 whether the defocus amount Df2 is less than or equal to a predetermined value. If the defocus amount is less than a predetermined value, the macro mode is displayed on the display device 65 in step S57.
and stops the motor 61 in step S58.
If the defocus amount is not below the predetermined value, step S
In step S59, the display device 65 displays that distance measurement is not possible, and in step S60, the motor 61 is stopped.

If the focal length Fφ of the lens 11 is not 75n or less in step S24, the process advances to step S61, where only integer part calculations (fractional part calculations are not performed) are counted, and it is determined whether there is one or more. do.

If the number of integer part operations is one or more, step S
64 and Siφ=11. Set Nr=32 and step S
63 performs integer part operations, but the number of integer part operations only is 1.
If there are no times, in step S62, the number of times of fractional calculation is counted and it is determined whether the number has reached one. If the fractional part calculation does not reach one time, the integer part calculation is performed in step S63. In this case, Siφ is taken in from the detection circuit 56, and the comparison range ■ is set accordingly.

Next, the process proceeds to step S65, where it is determined whether or not the maximum value v1φ of the number of matches in the data comparison in the fraction part calculation is less than or equal to 4. If the maximum value v1φ is less than or equal to 4, the display device 6
5 to display that distance measurement is not possible. If the maximum value viφ is not 4 or less, in step 866 Ns = Siφ−M
α), and it is determined in step S67 whether Nl is less than or equal to a predetermined value, and if N1 is less than or equal to the predetermined value, step 36
8 and Siφ=11, M(1)=Siφ−NIK
After setting, fractional part calculation is performed in step S69. Next, in step S70, it is determined whether the number of data Nφ that can be used for data comparison in the fractional calculation is 2 or less, and if Nφ2, the display device 65 displays that distance measurement is not possible, and if Nφ≦2, then Proceeding to step S71, the image shift amount Df1 is calculated by the following calculation: Dfl=(N, x 64 - Cφφφ)XKd. Further, if Nl is not equal to or less than a predetermined value in step S67, Cφφφ is set to O in step S72 and the process proceeds to step S71, and if the number of fraction operations reaches one in step S62, Siφ=11 is determined in step S873.
, M(1)=11, and the process proceeds to step S69.

Steps S74-5101 are steps 333-S6 above.
Same as 0.

FIG. 8 shows part of a drive circuit in another embodiment of an automatic focus adjustment device to which the present invention is applied.

In this embodiment, in the above embodiment, the output signal of the buffer amplifier 28 in the driver 13 is compared with the comparison voltage Vc1 of the comparison power supply consisting of the resistors 68 and 69 in the comparator 67, and the output signal of the buffer amplifier 28 is compared with the comparison voltage VCI. When the voltage is high, the output of the comparator 67 becomes high level.

The output of the comparator 67 is input to the NAND circuit 70 together with the check pulse from the CPU 43, and when both of these are at high level, the output of the NAND circuit 70 becomes low level. The RS flip-flop 71 is reset by the reset pulse φR, and is set by the falling edge of the output of the NAND circuit 70.

The CPU 43 performs the ninth step instead of the above steps 86 to S12.
Steps 8102 to 5111 as shown in the figure are executed.

That is, from step s5, proceed to step 5102 and perform step 1.
The 0 mS timer is set, and in step 5103, the reset pulse φR is turned off to start integration of the charge coupled device 12. Next, in step 5104, the comparator 29
It is determined whether the integration of the charge-coupled device 12 has been completed by determining whether the output signal of the charge-coupled device 12 has become low level, and if the integration of the charge-coupled device 12 has not been completed, the process advances to step 5105 and the monitor flag is set. Check AGCFL. If the monitor flag AGCFL is not set, the process advances to step 5106 and the 10m5 timer is checked. 1
If the 0m5 timer has not timed up, proceed to step 5.
Returning to step 104, when 10m5 times out, the monitor flag AGCFL is set in step 5107 to check the NAND circuit 7o and output a pulse. Next, in step 51n8, the lOOmS timer is set, and in step 5109, the output signal of the flip-flop 71 is checked. When the subject is bright, as shown in FIG. 10(b), the output of the buffer amplifier 28 has a large slope and becomes lower than the comparison voltage VCI when the check pulse is output, and the output signal of the flip-flop 71 becomes a low level. Then, the process returns to step 5104. If the subject is dark, use No. 10.
As shown in Figure (a), the output signal of the buffer amplifier 28 has a small slope, and when the check pulse is output, the comparison voltage vc
1, and the output signal of the flip-flop 71 becomes high level, so the process proceeds to step 8110, sets the low brightness flag and turns on the light projector 64, and then returns to step 5104. Next, the monitor flag AGCFL is set, and the process advances from step 8105 to step 5111.
Check the 00m5 timer. If the 100m5 timer does not time up, the process returns to step 5104, and when the charge coupled device 12 completes the integration or the 100m5 timer times out, the process proceeds to step S13.

(Effects) As described above, according to the present invention, the output signal of the monitor light-receiving element is used in a distance measuring device that receives light from a subject that has passed through a lens with a charge storage type light-receiving element and measures distance using the output signal. A monitor signal is created that changes according to the inclination of the light-receiving element of this monitor light-receiving element, and changes in this monitor signal are checked immediately after the charge storage type light-receiving element starts accumulating charges to determine the brightness of the subject. When it is dark, the illumination means emits light only when the charge accumulation type light-receiving element accumulates charge, so that the time required for distance measurement can be shortened and power consumption can be reduced. Furthermore, since the brightness of the subject is checked using a monitor light-receiving element, it can be checked accurately. Furthermore, since illumination is performed immediately if the subject is dark, the negative effects of noise are reduced.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a block diagram showing an embodiment of an automatic focusing device to which the present invention is applied, and FIG. 3 is a block diagram showing the configuration of a charge-coupled device in the same embodiment. A circuit diagram, FIG. 4 is a timing chart of the same charge-coupled device, FIG. 5 is a circuit diagram showing a part of the drive circuit in the above embodiment, FIG. 6 is a timing chart of the same drive circuit,
FIG. 7 is a flowchart showing the processing flow of the CPU in the above embodiment, FIG. 8 is a circuit diagram showing a part of the drive circuit in another embodiment of the automatic focusing device to which the present invention is applied, and FIG. 9 is the same. FIG. 10 is a flowchart showing part of the processing flow of the CPU in the embodiment, and FIG. 10 is a timing chart of the same embodiment. DESCRIPTION OF SYMBOLS 1... Charge storage type light receiving element, 2... Distance measuring means, 3...
...Monitor light receiving element, 4.Monitor signal forming means, 5.Monitor signal monitoring means, 6.Control means,
7...Lighting means. 1st page 3 ■ ``I) D 5th mouth 6th Sea fc Masu 9 Chobon'v, 1 time (a) ) [Yes] 8g turn) 'fJ10田(α)(4) φ, 7-川--open--9 cut procedure amendment (jf creation March 31, 1986

Claims (1)

[Claims] an illumination means for illuminating a subject; a charge accumulation type light receiving element for receiving light from the subject that has passed through the lens; a distance measuring means for measuring a distance based on an output signal of the light receiving element; a monitor light-receiving element that receives light from a subject; a monitor signal forming means for generating a monitor signal whose slope changes according to the amount of light received by the monitor light-receiving element based on the output signal of the monitor light-receiving element; and the charge storage device. monitor signal monitoring means for determining whether the subject is dark by checking changes in the monitor signal from the monitor signal forming means immediately after the start of charge accumulation in the type light receiving element; and when the subject is dark based on the output signal of the monitor signal monitoring means and control means for causing the illumination means to emit light only when charge is accumulated in the charge storage type light receiving element.