JPH0968643A - Range finder system and autofocusing camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a range finder system and an autofocusing camera equipped with the system capable of surely and rapidly performing range-finding by changing integral time in accordance with the brightness of an image formed on a line sensor for range finder. SOLUTION: A photoelectric conversion element 33 constituting left and right line sensors 31 and 32 is provided with a latch part 33c for outputting a latch signal when potential rising due to charge storage reaches a specified value. The elapsed time from starting the charge storage till inputting the latch signal is measured by counters 34 and 35. The brightness of the brightest part of the image on the line sensors 31 and 32 is detected based on the time when the first latch signal is inputted in the counters 34 and 35. When the latch signal exceeds specified minimum integral time, the integration is finished at that time, and when the signal does not exceed it, the integration is finished in the minimum integral time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring system for detecting a distance from a position of a pair of images formed on a light receiving element to a distance measuring object and an autofocus camera using the distance measuring system. , Relating to the setting of the integration time of the light receiving element.

[0002]

2. Description of the Related Art Conventionally, in autofocus cameras,
The light from the subject is guided to a pair of line sensors to form two images, and the distance to the subject is detected from the difference between the image positions to adjust the focus of the photographing lens. Specifically, the optical system for distance measurement guides the light from the subject to a pair of line sensors composed of photoelectric conversion elements to form an image, and the accumulated charge of the photoelectric conversion elements for each pixel between the two line sensors. A correlation calculation for comparison is performed to detect the distance between the two subject images. The distance between the two object images is determined depending on the geometric conditions of the distance measuring system such as the distance between the distance measuring optical system and the line sensor and the distance to the object. When the distance is obtained, the distance to the subject is calculated from the geometric condition of the distance measuring system. The focus is automatically adjusted for the subject by controlling the motor that adjusts the focus position of the taking lens according to the distance to the subject calculated in this way.

In automatic focus adjustment of a single-lens reflex camera, the light that has passed through the taking lens and is incident is guided to a pair of line sensors to form a pair of subject images. Normally, the distance between these two images should match the distance when focusing,
Drives the focus adjustment motor of the taking lens. in this case,
Automatic focus adjustment will be performed directly without calculating the distance to the subject, but if necessary, the distance to the subject can be calculated from the detected subject-to-image distance and the geometric conditions of the ranging system. Done.

The applicant of the present invention has disclosed a detailed method of distance measurement calculation in Japanese Patent Laid-Open Publication No. 59-126517.

[0005]

In order to calculate the distance to the subject by the above method, it is an essential condition that the image formed on the line sensor has a certain level of brightness. If the image is uniformly dark, the reliability of the correlation calculation becomes low, and it becomes impossible to obtain the distance between the subject images. In such a case, it becomes impossible to properly focus on the subject, and thus it is necessary to set the light receiving amount of the line sensor to a certain level or more.

Therefore, conventionally, the time for performing photoelectric conversion and charge accumulation, that is, the integration time, is set to a predetermined value so that an image of an object having an average brightness becomes an image of sufficient brightness. Then, after the integration for a predetermined time is completed, the accumulated charges of all the photoelectric conversion elements are read out to the arithmetic unit to perform the correlation calculation and the contrast calculation, and at the same time, it is determined whether or not the received light amount is sufficient.

In this method, however, since the integration time is constant, it is good when the subject is brighter than average.
In the case of a dark subject, a sufficient amount of light cannot be received within the integration time, and distance measurement tends to be impossible. Also, the transfer of the photoelectric conversion element potential to the arithmetic unit, that is, the reading of the accumulated charge is always performed. For this reason, it takes a long time to determine that the light amount is insufficient, and the measures for dealing with the insufficient light amount tend to be delayed. For example, in a system in which the auxiliary light is automatically emitted when the amount of light is insufficient, the emission of the auxiliary light is delayed. In contrast, in the autofocus camera, the delay in detection of insufficient contrast causes a decrease in the followability of focus adjustment with respect to a moving subject, which causes a decrease in the function of automatic focus adjustment.

Further, when the subject is sufficiently bright, an image having a sufficient brightness for distance measurement can be obtained by integration for a time shorter than a predetermined integration time that has been set. In such a case, it is useless to continue the integration for a predetermined time, which causes a delay in the distance measuring process.

The present invention provides a distance measuring system that reliably and quickly performs distance measurement by changing the integration time according to the brightness of an image formed on a line sensor, and an autofocus equipped with the distance measuring system. The purpose is to provide a camera.

[0010]

In order to achieve the above object, in the present invention, light from a distance measuring object is guided to a pair of photoelectric conversion element arrays, and each photoelectric conversion element array is photoelectrically converted and accumulated. In a distance measurement system that performs distance measurement by comparing charge distributions, a pair of photoelectric conversion element arrays until one of the photoelectric conversion element arrays has a predetermined amount of accumulated charge. Continue photoelectric conversion of.

The accumulated charge of the photoelectric conversion element depends on the time of photoelectric conversion and the amount of received light per unit time. When the distance measurement target is dark, that is, when the photoelectric conversion element array receives a small amount of light per unit time, if photoelectric conversion is aborted within a certain period of time, the accumulated charge in all photoelectric conversion element arrays decreases. The distance cannot be measured correctly. By continuing photoelectric conversion until the accumulated charge of one of the photoelectric conversion elements reaches a predetermined amount, even if the distance measurement target is dark, the photoelectric conversion element array has sufficient charges to perform distance measurement correctly. Accumulated.

In addition, in a distance measuring system for conducting distance measurement by guiding light from a distance measuring object to a pair of photoelectric conversion element arrays and comparing distributions of electric charges photoelectrically converted and accumulated by each photoelectric conversion element array. 1st photoelectric conversion of a pair of photoelectric conversion element rows
For a predetermined time or more, and until the accumulated charge of any one photoelectric conversion element of the pair of photoelectric conversion element rows reaches a predetermined value or until a second predetermined time elapses, and thereafter for distance measurement The charge distributions of are compared.

In the distance measuring system having this structure, photoelectric conversion is performed for at least the first predetermined time. The first predetermined time is set so that distance measurement can be performed correctly when the distance measurement target has normal brightness. When the object to be measured is dark and the accumulated charge of any photoelectric conversion element has not reached the predetermined amount when the first predetermined time has elapsed, the photoelectric charge of which the accumulated charge of any one photoelectric conversion element reaches the predetermined value. Continue conversion. However, the photoelectric conversion is terminated when the second predetermined time has elapsed. When the accumulated charge of any one of the photoelectric conversion elements reaches a predetermined value, the charges are accumulated in the photoelectric conversion element array to the extent that distance measurement can be performed correctly. Further, since the photoelectric conversion is stopped in the second predetermined time, when the light from the object to be measured is extremely weak and the distance cannot be measured, the photoelectric conversion is not meaninglessly performed for a long time. Even when the photoelectric conversion is stopped in the second predetermined time, the electric charges may be accumulated in the photoelectric conversion element array to the extent that distance measurement can be correctly performed.

In the above distance measuring system, the photoelectric conversion of the pair of photoelectric conversion element arrays is performed until the accumulated charge of any one photoelectric conversion element array of the pair of photoelectric conversion element arrays reaches a predetermined value, or It continues until the second predetermined time elapses. In this configuration, the photoelectric conversion ends when a photoelectric conversion element that stores a predetermined amount of electric charge appears in both of the pair of photoelectric conversion element arrays, as well as in both of them. Therefore, both photoelectric conversion element arrays accumulate charges to the extent that distance measurement can be performed correctly, and the reliability of distance measurement is improved.

Light emitting means for emitting light toward the object to be measured,
A pair of photoelectric conversion element arrays is provided with a contrast detection unit that detects a contrast from the accumulated charges, and when the contrast detected by the contrast detection unit is lower than a predetermined value, the pair of light emitting units emit light. The photoelectric conversion of the photoelectric conversion element array may be repeated. When a sufficient amount of electric charge is not accumulated by the first photoelectric conversion, the contrast becomes insufficient and accurate distance measurement cannot be performed. In this case, since the light emitting means emits light to illuminate the object to be measured, by performing photoelectric conversion again during that time, a sufficient amount of electric charge is accumulated to perform correct distance measurement.

Further, the autofocus camera is equipped with any one of the above distance measuring systems to measure the distance to the object, and the focus of the photographing lens is automatically adjusted based on the result. In this camera, the photoelectric conversion time of the photoelectric conversion element is extended according to the darkness of the subject, so even if the subject is dark, the charge is accumulated to the extent that correct distance measurement can be performed, and focus adjustment is possible. Is done correctly.

[0017]

FIG. 1 shows the configuration of an embodiment in which the distance measuring system of the present invention is applied to an autofocus camera. The camera body 1 includes a pair of left and right line sensors 31, 3
Distance measuring IC (AFIC) 3 having 2 and line sensor 3
A distance measuring optical system 2 composed of left and right lenses 21 and 22 for respectively focusing light from a subject on the lenses 1 and 32, a distance measuring device 4 including a microprocessor and connected to an AFIC 3, a photographing lens 5, and a photographing lens. A lens driving device 6 for changing the focal position of the lens 5 is provided. Each of the line sensors 31 and 32 is configured by arranging a plurality of photoelectric conversion elements in a line.

A film 7 is supplied behind the taking lens 5, and a shutter 9 is provided between the taking lens 5 and the film 7. The shutter 9 is driven by the exposure control device 8. The lens driving device 6 and the exposure control device 8 are controlled by the distance measurement calculation device 4.

A warning device 1 which is connected to the distance measurement calculation device 4 and comprises an auxiliary light device 10 which emits auxiliary light for distance measurement and an LED which lights up when distance measurement is impossible and issues a warning to the user.
1 and two switches S1 and S2 which are interlocked with a shutter release button (not shown). The switch S1 is closed when the release button is pressed halfway, and the switch S2 is closed when the release button is further pressed. When the switch S1 is closed, the distance measurement calculation device 4 instructs the AFIC 3 to start photoelectric conversion by the line sensors 31 and 32, and starts distance measurement. When the switch S2 is closed, the distance measurement calculation device 4 instructs the exposure control device 8 to open and close the shutter 9, and photographing is performed.

The distance measuring calculation device 4 includes line sensors 31, 3
After causing the AFIC 3 to perform photoelectric conversion for a time corresponding to the received light amount of 2, the instruction to stop the photoelectric conversion is given. After that, the potentials corresponding to the accumulated charges are read from the photoelectric conversion elements of the line sensors 31 and 32. The distance measurement calculation device 4 calculates the distance to the subject by performing a correlation calculation that compares the potentials of the left and right line sensors for each pixel, and determines the taking lens 5 via the lens driving device 6 according to the calculated distance. To drive. A series of processes of photoelectric conversion, distance measurement calculation, and lens driving are constantly repeated while the switch S1 is closed, that is, while the release button is half pressed. As a result, the taking lens 5 is always in focus with respect to the subject regardless of the movement of the subject. When the release button is further pressed and the switch S2 is closed, the shutter 9 is opened by the exposure control device 8 and the subject light is emitted from the film 7.
And a clear image of the subject is recorded on the film 7.

FIG. 2 shows the configurations of the AFIC 3 and the distance measurement calculation device 4. In the figure, solid arrows represent the flow of data to be processed, and dotted arrows represent the flow of control signals. AFI
In addition to the left and right line sensors 31 and 32, the C3 is provided with two counters 34 and 35 and a clock 36 that supplies a clock signal to these. The photoelectric conversion elements 33 constituting the left and right line sensors 31, 32 are respectively a light receiving section 33a, a storage section 33b and a latch section 33c.
Consisting of The light receiving section 33a converts the received light into an electric charge and outputs it to the storage section 33b. The accumulating portion 33b accumulates the electric charge given from the light receiving portion 33a as a potential. The latch unit 33c outputs the latch signal when the potential of each storage unit 33b rises and reaches a predetermined value.
It is provided corresponding to. Such photoelectric conversion element 3
3 are arranged on the left and right line sensors 31 and 32, respectively.

The distance measuring calculation device 4 is started by closing the switch S1, the timer 41, the line sensors 31, 3
2. An integration start instruction circuit 42 for generating an integration start signal INT for instructing the start of photoelectric conversion and charge accumulation by 2 and an integration end instruction circuit 43 for generating an integration end signal TRM for instructing the end of photoelectric conversion and charge accumulation are provided. There is. The time for performing photoelectric conversion and charge accumulation, that is, the integration time TE, is not fixed to a fixed value, but is within a range from a predetermined minimum integration time TEmin to a maximum integration time TEmax depending on the amount of light received by the line sensors 31 and 32. be changed. The minimum integration time TEmin is set to a value such that a subject darker than average brightness becomes an image with sufficient brightness. The distance measurement calculation circuit 4 includes an integration time setting circuit 51 that sets the integration time, and a distance calculation unit 60 that performs various calculations for distance measurement. The configuration and operation of these will be described later.

When the shutter release button is half-depressed and the switch S1 is closed, the timer 41 starts the time counting operation and gives a signal for instructing the integration start instruction circuit 42 to generate a signal. Further, the timer 41 stores the minimum integration time TEmin and the maximum integration time TEmax, and sets the maximum integration time TEmax to the integration time TE at the same time as the start of timing. This integration time TE is switched to the minimum integration time TEmin by the signal given from the integration time setting circuit 51. The timer 41 gives a signal for instructing the integration end instruction circuit 43 to generate a signal when the integration time TE has elapsed.

The integration start instruction circuit 42 gives an integration start signal INT to the left and right line sensors 31, 32 in response to a command signal from the timer 41. The integration start signal INT is also given to the counters 34 and 35, and the counters 34 and 35
Starts timing based on the clock signal from the clock 36.

In response to the integration start signal INT, the accumulating portions 33b of all photoelectric conversion elements 33 are initialized to discharge the accumulated charges to zero the potential, and the light receiving portion 33a starts photoelectric conversion. The charges generated by the photoelectric conversion of the light receiving unit 33a are given to the storage unit 33b, and the storage unit 33b
The potential of b increases according to the amount of light received by the light receiving unit 33a. When the potential of the storage section 33b reaches a predetermined potential V0, the latch signal is output from the latch section 33c. The photoelectric conversion by the light receiving section 33a and the charge accumulation by the accumulating section 33b are continued even after the latch signal is output from the latch section 33c.

All photoelectric conversion elements 33 of the left line sensor 31
A latch signal from the photoelectric conversion elements 33 of the right line sensor 35 is input to the counter 35. These counters 34, 35
Starts timing simultaneously with the start of integration by the integration start signal INT, and when a latch signal is input, the elapsed time from the start of integration can be measured.

The counter 34 counts the number of latch signals input from the left line sensor 31, and when a predetermined number of latch signals are input, outputs the elapsed time TL1 until then to the integration time setting circuit 51. The counter 35 similarly
The number of latch signals input from the right line sensor 32 is counted, and when a predetermined number of latch signals are input, the elapsed time TR1 until then is output to the integration time setting circuit 51. In this embodiment, the counters 34 and 35 are set to output the elapsed times TL1 and TR1 when the first latch signal is input. These elapsed times TL1 and TR1 represent the time required for the accumulated charge of the brightest part of each of the left and right line sensors 31, 32, that is, the photoelectric conversion element having the largest amount of received light, to reach a predetermined amount. FIG. 4 shows the relationship between the image brightness and the elapsed time, and the relationship between the minimum integration time TEmin and the maximum integration time TEmax.

The integration time setting circuit 51 has a minimum integration time TE.
min is stored, and when the elapsed times TL1 and TR1 are given from the counters 34 and 35, each is compared with the minimum integration time TEmin. Then, the elapsed time TL1,
When one of TR1 which is given first is smaller than TEmin, an instruction signal for changing the integration time TE to the minimum integration time TEmin is given to the timer 41. As a result, the timer 41 is configured so that when the minimum integration time TEmin elapses,
The integration end instruction circuit 43 is instructed to generate the integration end signal TRM. On the other hand, the elapsed time TL1, TR
When the one which is given first out of 1 is equal to or more than TEmin, a signal for instructing the generation of the integration end signal TRM is immediately given directly to the integration end instruction circuit 43.

Upon receiving the signal from the timer 41 or the integration time setting circuit 51, the integration end instruction circuit 43 gives the integration end signal TRM to all the photoelectric conversion elements 33. By the integration end signal TRM, the light receiving unit 33a of each photoelectric conversion element 33 stops photoelectric conversion. In addition, the storage unit 33b
Outputs a potential corresponding to the accumulated charge to the distance calculation unit 60.

Integration time setting circuit 51 and timer 41
By operating as described above, the line sensor 3
1 and 32 perform photoelectric conversion and charge accumulation for at least the minimum integration time TEmin, and integration is continued until one photoelectric conversion element in the brightest part accumulates a predetermined amount of charge, and the accumulated charge reaches a predetermined amount. At that point, the integration will be terminated. When none of the photoelectric conversion elements 33 of the left and right line sensors 31, 32 has accumulated a predetermined amount of charge within the maximum integration time TEmax, no latch signal is output and the elapsed times TL1, TR1 are given to the integration time setting circuit 51. Therefore, the integration time TE of the timer 41 is not changed. Therefore, the timer 41 gives a signal for instructing the generation of the integration end signal TRM to the integration end instruction circuit 43 when the maximum integration time TEmax has elapsed, and the integration is performed for the maximum integration time TEmax.

The distance calculation unit 60 includes AD converters 61 and 6
2, RAM 63, 64, difference conversion circuits 65, 66, RA
M67, 68, a contrast calculation circuit 69, a distance measurement possibility determination circuit 70, a correlation calculation circuit 71, and a subject distance calculation circuit 72. The output potential from each photoelectric conversion element 33 of the left line sensor 31 is sequentially converted into a digital value by the AD converter 61, and the converted value of 128 pixels VL ₁ to
The VL ₁₂₈ is stored in the RAM 63. Right line sensor 3
Similarly, the output potential from the second photoelectric conversion element 33 is also sequentially converted into a digital value by the AD converter 62, and the converted VR pixel values VR _{1 to} VR ₁₂₈ are stored in the RAM ₆₄ .

The difference conversion circuit 65 reads out the pixel value of the RAM 63 and takes the difference every 4 pixels (AL _j = VL _{j + 4).}
-VL _j , j = 1,2, ..., 124), and their difference values AL _{1 to} AL ₁₂₄
Is stored in the RAM 67. The difference conversion circuit 66 is also R
The pixel value of AM64 is taken every 4 pixels (AR _j = V
R _{j + 4} −VR _j , j = 1,2, ..., 124), difference values AR _{1 to} AR
₁₂₄ is stored in the RAM 68. Obtaining the difference value in this way is called a filter process, and the sensitivity difference between the left and right line sensors 31 and 32 is removed by this process, and the reliability of the correlation calculation is improved.

The contrast calculation circuit 69 calculates the contrast value C by performing the calculation of equation (1).

[0034]

[Equation 1]

The distance measurement availability determination circuit 70 determines whether or not distance measurement is possible based on the calculated contrast value C. Specifically, the contrast value C is compared with a predetermined value C0, it is determined that distance measurement is possible when the contrast value C is a predetermined value C0 or more, and when the contrast value C is less than the predetermined value C0, Due to the shortage, it is determined that the reliability of the correlation calculation is low and the distance cannot be measured.

When it is determined that the distance cannot be measured, the distance measurement availability determination circuit 70 blinks the LED of the warning device 11 to notify the user that the contrast is insufficient and a signal for instructing the timer 41 to restart. RST is given to cause the line sensors 31 and 32 to perform photoelectric conversion and charge accumulation again. At this time, the distance measurement availability determination circuit 52 causes the auxiliary light device 10 to emit light to illuminate the subject. When the entire subject is dark and a sufficient amount of light cannot be received even if the integration is performed for the maximum integration time TEmax, distance measurement can be performed by irradiating the subject with the auxiliary light for distance measurement in this way. . Even if the auxiliary light is turned on and photoelectric conversion and charge accumulation are performed again, if the calculated contrast value C is less than the predetermined value C0, the LED of the warning device 11 is continuously turned on and the user cannot measure the distance. Then, the lens driving device 6 is controlled so that the taking lens 5 is focused at infinity.

When it is determined that the distance measurement is possible, the distance measurement availability determination circuit 70 commands the correlation calculation circuit 71 to start the correlation calculation. The correlation calculation circuit 71 calculates the equation (2) in order to obtain the correlation between the pixel values of the RAM 67 and the RAM 68. H (m, k) obtained here represents the degree of coincidence between the compared left and right images, and the smaller the value, the higher the degree of coincidence.

[0038]

[Equation 2]

Here, the pixels AL _{3 to} AL of the RAM 67 are
₁₂₂ blocks in 3 blocks of 40 pixels each (AL _{3 to} AL ₄₂ ),
Divide into (AL _{43 to} AL ₈₂ ), (AL _{83 to} AL ₁₂₂ ),
85 blocks (AR ₁ to AR ₄₀ ) to (AR ₈₅ to AR, each consisting of 40 pixels of RAM 68 and shifted by 1 pixel
₁₂₄ ). Calculated H (1,1) ~ H (3,85)
The value of 255 is given to the subject distance calculation circuit 72.

The subject distance calculating circuit 72 finds the one H (m1, k1) having the smallest value among H (1,1) to H (3,85) given from the correlation calculating circuit 71. The m1 and k1 found here are the m1th of the three blocks in the RAM 67.
And the block starting from the k1 pixel of the RAM 68 is the best match. Next, this H (m1, k1) and H (m1, k1-1), H (m1, k1 +
1) is used for interpolation processing, and the maximum matching score H0 (m1, k
The value k0 of k that is 0) is calculated. In consideration of the arrangement pitch of the photoelectric conversion elements 33 and the installation intervals of the left and right line sensors 31 and 32, the first pixel number (40 · m1−37 = 3, 43 or 83) of the m1st block and k0 From the value, the distance between the parts of the images of the line sensors 31 and 32 that best match each other is calculated. The distance to the subject is calculated from the image distance thus calculated and the geometric conditions of the distance measuring system such as the distance between the distance measuring optical system 2 and the line sensors 31 and 32.

The subject distance calculation circuit 72 outputs the calculated subject distance to the lens driving device 6. The lens driving device 6 calculates the focal position of the photographing lens 5 corresponding to the given subject distance and sets the focal position of the photographing lens 5. In this way, autofocus is performed.

The flow of the above distance measurement processing is shown in the flowchart of FIG. The distance measurement process starts when the shutter release button is pressed halfway (step # 100), and the timer 4
1 sets the maximum integration time TEmax as the integration time TE (# 105). Further, photoelectric conversion and charge accumulation are started by the integration start signal INT (# 110). After the integration is started, whether or not the potentials of the brightest parts of the left and right line sensors 31 and 32 have reached the predetermined potential V0 is constantly monitored by the outputs of the elapsed times TL1 and TR1 from the counters 34 and 35 (# 115).

When the elapsed time TL1 or TR1 is detected, the value is compared with the minimum integration time TEmin (#
120). When the elapsed time TL1 or TR1 is smaller than the minimum integration time TEmin, the integration time TE is changed to the minimum integration time TEmin (# 125), and step # 1
Return to 15. When the elapsed time TL1 or TR1 is longer than the minimum integration time TEmin, the integration is immediately terminated (#
130).

At step # 115, the elapsed time TL
When 1 and TR1 are not detected, it is determined whether the set integration time TE has elapsed (# 13).
5). If the integration time TE has not yet elapsed, the process returns to step # 115, and if it has elapsed, the integration ends.

Completion of photoelectric conversion and charge accumulation (# 140)
After that, the potential of the photoelectric conversion elements of the line sensors 31 and 32, that is, the pixel value is read out to the distance measurement calculation unit 60 (# 14).
5). Next, the contrast is calculated from the difference between the pixel values of the adjacent pixels (# 150). By comparing the calculated contrast value C with a predetermined value C0, it is determined whether or not reliable correlation calculation can be performed (# 155).

When the contrast value C is smaller than the predetermined value C0, it is determined that the reliability is low due to insufficient contrast, and it is determined whether or not auxiliary light is emitted in the charge accumulation (# 160). When the auxiliary light is not emitted, the user is warned that the contrast is insufficient (# 165), the auxiliary light is emitted (# 170), and photoelectric conversion and charge accumulation are performed again (# 105). . Step # 1
If the auxiliary light is emitted in the determination of 60, the user is warned that distance measurement is impossible (# 175), and the taking lens 5 is focused on infinity (# 180). afterwards,
# Return to step 105 to restart photoelectric conversion and charge accumulation. When the contrast value C is equal to or greater than the predetermined value C0, it is determined that the subject distance can be calculated with high reliability, and the correlation calculation of the images of the two line sensors is performed (# 185) to calculate the subject distance (# 190). , The photographing lens 5 is driven so that the subject is in focus (# 195).

Thus, the integration time is set and the distance is measured according to the brightness of the subject. When the subject is bright,
The integration is completed at the minimum integration time TEmin or a time close thereto, and distance measurement can be performed quickly. When the subject is dark, the integration time is extended according to the degree of darkness, so that distance measurement can be performed accurately and with the minimum integration time that can realize the precision. However, if the subject is too dark to measure the distance without performing integration for an extremely long time,
Considering that the subject moves, the unlimited extension of the integration time is meaningless. By providing the maximum integration time TEmax, such meaningless integration is avoided.

In this embodiment, the case where the integration is terminated when the potential of one photoelectric conversion element of the left and right line sensors 31 and 32 reaches the predetermined value V0 has been described. The integration may be continued until the potential of the element reaches the predetermined value V0. In that case, the integration time setting circuit 51 determines the elapsed time TL.
The integration time is changed based on whichever of 1 and TR1 is given later. That is, when the later elapsed time TL1 or TR1 is smaller than the minimum integration time TEmin,
An instruction signal for changing the integration time TE to the minimum integration time TEmin is given to the timer 41, and when TEmin or more, a signal for giving an instruction to generate the integration end signal TRM is immediately given to the integration end instruction circuit 43. When the integration time is set in this way, both line sensors 31 and 32 reliably receive a predetermined amount of light or more, and the reliability of the correlation calculation for distance measurement is improved, and the subject distance is more accurately measured. It becomes possible to ask.

The counters 34 and 35 are set so as to output the elapsed times TL1 and TR1 when the first latch signal is input. For example, when the 30th latch signal is input, the counters up to that time are input. Elapsed time is TL1, T
You may make it output as R1. With this setting, the integration ends when about 1/4 of all the photoelectric conversion elements reach the predetermined potential, and the range of the images on the line sensors 31 and 32 exceeds a predetermined value. It becomes bright. Further, even if one photoelectric conversion element issues a latch signal due to some cause such as noise generation, the integration is not immediately terminated, and erroneous setting of the integration time is avoided.

Furthermore, after the lapse of the minimum integration time TEmin, the integration is not immediately terminated when a photoelectric conversion element that has reached the predetermined potential V0 appears, but a predetermined period ΔTE.
Alternatively, the integration time TE may be extended (TE + ΔTE). In this case, it shall be extended within a range not exceeding the maximum integration time TEmax.

[0051]

According to the distance measuring system of the present invention, since the photoelectric conversion time of the photoelectric conversion element array is extended according to the darkness of the distance measuring object, the accuracy is always maintained regardless of whether the distance measuring object is bright or dark. The distance can be measured well. Further, when the distance measurement target is bright, the photoelectric conversion time is not unnecessarily extended, so that the distance measurement can be performed quickly.

In the distance measuring system according to the second aspect, when the distance measuring object is bright, the minimum photoelectric conversion is cut off in the first predetermined time, and the time required for distance measuring is short. In addition, since the photoelectric conversion time is extended as the target object becomes darker, even if the target object is somewhat darker, sufficient electric charge can be accumulated and the distance can be accurately measured. Further, since the photoelectric conversion is terminated in the second predetermined time, it is possible to avoid performing the photoelectric conversion for a long time without meaning when the object to be measured is extremely dark and cannot be measured. Even when the photoelectric conversion is terminated in the second predetermined time, a certain amount of charge may be accumulated in the photoelectric conversion element array and distance measurement can be performed. In this case,
Distance measurement can be performed.

In the distance measuring system according to the third aspect, photoelectric conversion is completed when both photoelectric conversion element arrays have accumulated a sufficient amount of electric charge for distance measurement, so that reliability of distance measurement is improved.

According to the distance measuring system of claim 4, when the object to be measured is dark and photoelectric conversion is cut off in the second predetermined time, resulting in insufficient contrast, the object to be measured is illuminated by the light of the light emitting means. Therefore, it is possible to accumulate sufficient charges for distance measurement in the photoelectric conversion again.
Since the distance measurement target is illuminated, the photoelectric conversion is likely to be completed again by the second predetermined time.
Therefore, even when the distance measurement target is dark or at night, distance measurement can be accurately performed in a short time.

In the autofocus camera according to claim 5,
Even for a dark subject, distance measurement can be accurately performed, and a focused image can be taken. Further, since the photoelectric conversion can be suppressed to the minimum time required for distance measurement, focus adjustment can be performed quickly, and the focus position of the taking lens can quickly follow a moving subject. Also, in the configuration in which the light emitting means is provided in the distance measuring system,
Even an extremely dark subject can be accurately measured in a short time.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an autofocus camera according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration and a signal flow of a ranging IC and a ranging calculation device.

FIG. 3 is a flowchart showing the flow of distance measurement processing.

FIG. 4 is a diagram showing the relationship between the brightness of a line sensor image and the time required for the potential of a photoelectric conversion element forming the line sensor to reach a predetermined potential.

[Explanation of symbols]

1 Auto Focus Camera Main Body 2 Distance Measuring Optical System 3 Distance Measuring IC 4 Distance Measuring Arithmetic Device 5 Photographing Lens 6 Lens Driving Device 7 Film 8 Exposure Control Device 9 Shutter 10 Auxiliary Light Unit (Light Emitting Device) 11 Warning Device 21, 22 Distance measuring lens 31 Left line sensor 32 Right line sensor 33 Photoelectric conversion element 33a Light receiving part 33b Accumulating part 33c Latch part 34, 35 Counter 36 Clock 41 Timer 42 Integration start instruction circuit 43 Integration end instruction circuit 51 Integration time setting circuit 60 Distance Calculation unit 61, 62 AD converter 63, 64 RAM 65, 66 Difference conversion circuit 67, 68 RAM 69 Contrast calculation circuit (contrast detection means) 70 Distance measurement availability determination circuit 71 Correlation calculation circuit 72 Subject distance calculation circuit S1, S2 switch , TL1, TR1 elapsed time E integration time TEmin minimum integration time (first predetermined time) TEmax maximum integration time (second predetermined time)

Claims (5)

[Claims] 1. A distance measuring system for measuring a distance by guiding light from a distance measuring object to a pair of photoelectric conversion element arrays, and comparing distributions of charges accumulated by photoelectric conversion of each photoelectric conversion element array. A distance measuring system, wherein photoelectric conversion of the pair of photoelectric conversion element rows is continued until the accumulated charge of any one photoelectric conversion element row of the pair of photoelectric conversion element rows reaches a predetermined amount. . 2. A distance measuring system for measuring a distance by guiding light from a distance measuring object to a pair of photoelectric conversion element arrays and comparing distributions of charges accumulated by photoelectric conversion of the photoelectric conversion element arrays. , The photoelectric conversion of the pair of photoelectric conversion element rows is performed for a first predetermined time or more, and the accumulated charge of any one photoelectric conversion element of the pair of photoelectric conversion element rows reaches a predetermined amount, or second The distance measuring system is characterized in that the charge distribution is continued until a predetermined time of, and then the charge distributions for distance measurement are compared. 3. The photoelectric conversion of the pair of photoelectric conversion element arrays is performed until the accumulated charge of any one photoelectric conversion element of each of the pair of photoelectric conversion element arrays reaches a predetermined amount, or the second conversion. The distance measuring system according to claim 2, wherein the distance measuring system is continued until a predetermined time of (3) elapses. 4. The contrast detected by the contrast detecting means, comprising: a light emitting means for emitting light toward an object to be distance-measured; and a contrast detecting means for detecting the contrast from the accumulated charges of the pair of photoelectric conversion element arrays. 4. The distance measuring system according to claim 2, wherein the photoelectric conversion of the pair of photoelectric conversion element rows is repeated in a state where the light emitting means emits light when is smaller than a predetermined value. . 5. The distance measuring system according to claim 1 is provided to measure the distance to an object, and the focus of the photographing lens is automatically adjusted based on the result. An autofocus camera.