JPH09211306A - Range-finding system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely measure the distance to an object by setting the sensitivity of a photodetector so that it becomes high when luminance is higher than the prescribed luminance and it becomes low when it is lower than the prescribed luminance. SOLUTION: The sensitivity of a line sensor is switched according to the luminance of an object. Besides, not only the luminance but also the type of a light source is detected so that the sensitivity is switched to the sensitivity suitable for the characteristic of the light source. For example, the sensitivity of the line sensor is switched by arranging plural storage parts whose capacity is different as the electric charge storage parts 33b and storing electric charge in one of the storage parts in response to an instruction from a sensor sensitivity decision means 102. That means, when the sensitivity is set to be low, storage time is prolonged by storing the electric charge in the storage part whose capacity is large. On the contrary, when the sensitivity is set to be high, the electric charge is switched to be stored in the storage part whose capacity is small.

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 to a measuring object based on a positional relationship between a pair of images formed on a pair of light receiving element arrays.

[0002]

2. Description of the Related Art In a camera having an automatic focus adjustment function, light from a subject is guided to a pair of light receiving element arrays to form two images, and two images are formed from the positional relationship between the two images. It is known that the distance is detected and the focus of the photographing lens is adjusted based on the detection result. Specifically, a distance measuring optical system guides light from a subject to a pair of line sensors composed of a photoelectric conversion element array to form an image, and the accumulated charge of the photoelectric conversion elements is transferred between the two line sensors for each pixel. Then, a correlation calculation is performed to obtain the distance (distance) between the two subject images. The distance between the two subject images is
It is determined depending on geometric conditions such as the distance between the distance measuring optical system and the line sensor and the distance to the subject. Conversely, when the distance between the two subject images is obtained, the distance to the subject is calculated. be able to. The focus of the subject can be automatically adjusted by controlling the drive of the motor that adjusts the focus of the taking lens according to the distance to the subject calculated in this way.

In a conventional camera equipped with such a distance detecting device, the sensitivity of the line sensor is switched according to the brightness of the subject. That is, when the brightness is low, the sensitivity is increased to increase the integration time, and when the brightness is high, the sensitivity is decreased to decrease the integration time. The sensitivity is switched by providing a charge storage section having a different capacitance and selectively switching them.

[0004]

However, as the type of line sensor, a type in which the charge accumulation time until the predetermined charge amount is reached is detected for each light receiving element and the detected time data is used as the image data of the subject If the line sensor is used, there will be no variation if the light source is only the ambient light component, but for pulsating flow light such as fluorescent lamps, a certain amount of charge will accumulate if the measurement start time is different. The time it takes to be done will differ. Not only the accumulation time is different, but also the ratio of the accumulation time of each pixel is changed, so that the waveform of the image data obtained at each measurement is different and the calculated distance is also different. In other words, even if the same subject is measured, the data will vary from measurement to measurement, and if the data includes variation, the calculated subject distance will also include variation, making accurate distance measurement difficult. The problem arises. Referring to FIG. 12, in the first measurement, the pixel px1 is the time t1 and the pixel px2 is the time t1.
Only t2 is accumulated, and time is t in the second measurement.
Only 1'and t2 'are stored. At this time, the ratio of accumulation time t1:
t2 and t1 ': t2' are different.

As described above, when the line sensor of the type that uses the accumulation time of each light receiving element as image data is used, the distance measurement under the light source including the pulsating flow component varies and the accurate object distance is obtained. There was a problem that could not be detected.

The present invention has been made to solve the above problems, and provides a distance measuring system capable of accurately measuring a subject distance even in a situation where a pulsating light component is included as a light source. With the goal.

[0007]

In order to achieve the above object, a distance measuring system of the present invention comprises a pair of optical systems for forming a subject image, and a pair of optical systems for arranging the optical systems on substantially the respective image forming planes. A pair of light receiving element rows having a plurality of light receiving sensitivities, a calculation means for calculating the distance to the subject from the output signals from the light receiving element rows, a luminance measuring means for measuring the luminance of the subject, and the luminance measuring means. A sensitivity setting means for setting the sensitivity of the light receiving element array from the output; and a control means for controlling the sensitivity to be set high when the subject brightness is higher than a predetermined brightness and low when the brightness is lower than the predetermined brightness. Is characterized by. According to this configuration, the sensitivity of the light receiving element is switched according to the brightness of the subject detected by the brightness measuring means, and the sensitivity is set to a low sensitivity if the brightness is higher than a predetermined brightness and a high sensitivity if the brightness is darker than a predetermined brightness.

The charge storage time is changed by such sensitivity switching, but the storage time is
When it is set to a short time, it is set to be at most half a cycle or less to one cycle of the pulsating flow light, or set to be at least one cycle at a short time when set to a long time.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An external view of an autofocus camera to which a distance measuring system according to an embodiment of the present invention is applied is shown in FIG. 1, and a schematic configuration thereof is shown in FIG. Camera body 1 is left and right
A distance measuring IC (hereinafter referred to as AFIC) 3 having a pair of line sensors 31 and 32, and a distance measuring IC including a pair of left and right lenses 21 and 22 for focusing light from a subject on the line sensors 31 and 32, respectively. The optical system 2 is provided with an arithmetic and control unit 4 for distance measurement, which is composed of a microprocessor and is connected to the AFIC 3, a taking lens 5, and a lens driving unit 6 for changing the focal position of the taking lens 5. Line sensor 3
Reference numerals 1 and 32 each include a plurality of photoelectric conversion elements arranged 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 control device 4.

Further, the distance measurement calculation control device 4 is connected to a light emission auxiliary device 10 which emits auxiliary light for distance measurement, and two switches S1 and S2 which are interlocked with the shutter release button 11. 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 to the second stage. When the switch S1 is closed, the distance measurement calculation control device 4
Instructs the AFIC 3 to start photoelectric conversion by the line sensors 31 and 32, and the distance measuring operation is started. When the switch S2 is closed, the distance measurement calculation control device 4 instructs the exposure control device 8 to open and close the shutter 9 to control the exposure of the film 7.

Further, the line sensors 31 and 32 are designed so that the sensitivities thereof can be switched, and the following constitutions are provided for that purpose. A sensor sensitivity determining unit 102 that determines the sensitivity of the line sensors 31 and 32 is connected to the distance measuring IC 3 in which the line sensors 31 and 32 are formed, and the sensor sensitivity determining unit 102 further receives light for photometry. The device 100 and the light source determining means 101 are connected.

The distance measurement calculation control device 4 instructs the AFIC 3 to stop the photoelectric conversion after causing the AFIC 3 to perform the photoelectric conversion for a predetermined period. Then, 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 control device 4 calculates the distance to the subject by performing a correlation calculation that compares the potentials of the pixels between the left and right line sensors, and shoots through the lens drive device 6 according to the calculated distance. The lens 5 is driven. A series of processes of photoelectric conversion, distance measurement calculation, and lens driving are repeatedly performed while the switch S1 is closed, that is, while the release button is half pressed. As a result, the photographing lens 5
Indicates that the subject is always in focus regardless of the movement of the subject. When the release button is pressed halfway and the switch S2 is closed, the shutter 9 is opened for a predetermined time by the exposure control device and the subject light is imaged on the film 7, whereby a clear image of the subject is formed. Recorded in 7.

FIG. 3 shows the AFIC 3 and the distance measurement calculation control device 4.
Is shown. In the figure, solid arrows represent the flow of data to be processed, and dotted arrows represent the flow of control signals. A
The FIC 3 includes two counters 34 and 35 corresponding to the pair of line sensors 31 and 32, and counters 34 and 35.
A clock 36 for providing a clock signal is provided. The photoelectric conversion elements 33 constituting the pair of line sensors 31 and 32 each include a light receiving portion 33a, a storage portion 33b, and a latch portion 33c. The light receiving unit 33a converts the received light into an electric charge and outputs the electric charge to the storage unit 33b.
Accumulates the electric charge given from the light receiving portion 33a as a potential. The latch unit 33c causes each of the storage units 33b to output a latch signal when the potential of each storage unit 33b rises and reaches a predetermined value or when an instruction is received from the distance measurement calculation control device 4. Correspondingly provided. Such a photoelectric conversion element 33 is a pair of left and right line sensors 31, 3
128 are arrayed in 2 each.

The distance measurement calculation control device 4 includes a timer 41 and a line sensor 3 which start timing by closing the switch S1.
An integration start instruction circuit 42 for generating an integration start signal INT for instructing the start of photoelectric conversion and charge accumulation by 1, 32, and an integration end signal TRM for instructing the end of photoelectric conversion and charge accumulation.
Is provided with an integration end instruction circuit 43.

The line sensors 31 and 32 are connected so that a control signal from the sensor sensitivity determining means 102 is input, and the sensor sensitivity is determined by the AE photometric device 1.
00 and data from the light source determining means 101.

When the shutter release button is half-depressed and the switch S1 is closed, the timer 41 starts the time counting operation and gives the integration start instruction circuit 42 a signal for instructing signal generation. The integration start instruction circuit 42 gives an integration start signal INT to the pair of line sensors 31 and 32 by the signal from the timer 41. This integration start signal INT
Is also given to the counters 34 and 35, and the counters 34 and 3 are
5 starts timing based on the clock signal from the clock 36. Then, the timer 41 gives a signal to the integration end instruction circuit 43 to notify that the predetermined time TE has elapsed when the predetermined time TE has elapsed from the start of time counting.

In response to the integration start signal INT, the storage sections 33b of all the photoelectric conversion elements 33 perform initialization to discharge the accumulated charges and set the potential to 0, and the light receiving section 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 unit 33a and the charge storage by the storage unit 33b are continued even after the latch signal is output from the latch unit 33c.

When a predetermined time TE has elapsed after the start of integration,
Based on the signal from the timer 41, the integration end instruction circuit 43 sends the integration end signal TRM to all the photoelectric conversion elements 3.
3 given. By this integration end signal TRM, the light receiving unit 33a of each photoelectric conversion element 33 stops photoelectric conversion, and the storage unit 33b holds the accumulated charges. Further, the latch unit 33c outputs the latch signal when it is not outputting the latch signal after being given the integration start signal INT. Therefore, each photoelectric conversion element 33 outputs the latch signal either when the charge accumulation reaches a predetermined amount or when the integration is completed.

Latch signals from all photoelectric conversion elements 33 of one line sensor 31 are input to the counter 34, and latch signals from all photoelectric conversion elements 33 of the other line sensor 32 are input to the counter 35. These counters 34 and 35 start timing at the same time as the integration starts by the integration start signal INT, and can measure the elapsed time from the start of the integration when the latch signal is input.

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 line sensor 31 on the left side in FIG. 3 is sequentially converted into a digital value by the AD converter 61, and the converted values VL1 to VL128 of 128 pixels are stored in the RAM 63. Similarly, the output potential from each photoelectric conversion element 33 of the right line sensor 32 is also sequentially converted into a digital value by the AD converter 62, and the converted values VR1 to VR128 of 128 pixels are RA.
It is stored in M64.

The difference conversion circuit 65 reads the pixel value of the RAM 63 and takes the difference every 4 pixels (ALj = VLj + 4−
VLj, j = 1, 2, ..., 124), and their difference values AL1 to AL124
Is stored in the RAM 67. The difference conversion circuit 66 is also R
The pixel value of AM64 is taken every four pixels (ARj = VRj
+ 4−VRj, j = 1,2, ..., 124), difference values AR1 to AR124
Are stored in the RAM 68. Obtaining the difference value in this way is called a filter process, and this process removes the sensitivity difference between the left and right line sensors 31 and 32 and improves the reliability of the correlation calculation.

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

[0024]

[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, and when the contrast value C is a predetermined value C0 or more, it is determined that distance measurement is possible, and when the contrast value C is less than the predetermined value C0, the contrast is insufficient. Since the reliability is low even if the correlation calculation is performed, it is determined that distance measurement is impossible.

When it is determined that the distance measurement is impossible, the distance measurement availability determination circuit 70 gives the signal RST for instructing the timer 41 to restart, and causes the line sensors 31 and 32 to perform photoelectric conversion and charge accumulation again. At this time, the distance measurement availability determination circuit 70 sends a signal to the auxiliary light device 10 to emit auxiliary light to illuminate the subject. When the images of the left and right line sensors 31 and 32 do not have sufficient contrast because the entire subject is dark due to insufficient light quantity, distance measurement can be performed by illuminating the subject with auxiliary light for distance measurement in this way. Become.

When it is determined that the distance measurement is possible, the distance measurement availability determination circuit 70 instructs 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 stored in 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.

[0028]

[Equation 2]

Here, the pixels AL3 to AL1 of the RAM 67 are
22 in 3 blocks of 40 pixels each (AL3 to AL4
2), (AL43 to AL82), (AL83 to AL122), and the comparison is performed while shifting each pixel by one pixel from the RAM 68. That is, for each of the above three blocks, pixels (AR1 to AR40) to (A
R85-AR124) is being compared. Eighty-five values are calculated for each block, and the calculated values H (1,1) to H (3,
The 255 values of 85) are given to the object distance calculation circuit 72.

The subject distance calculation circuit 72 finds H (m1, k1) having the smallest value among H (1,1) to H (3,85) given from the correlation calculation circuit 71. M1 and k1 found here
Shows that the m1th block of the three blocks of the RAM 67 and the 40th pixel portion of the RAM 68 starting from the k1st pixel are the best match. Next, interpolation processing is performed using this H (m1, k1), H (m1, k1-1), and H (m1, k1 + 1) to obtain the best match H0 (m1, k0). Value k0
Is calculated. Then, considering 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) of the m1th block is considered.
-37), that is, the value of 3, 43 or 83 and the value of k0 is used to calculate the interval between the parts of the images of the line sensors 31 and 32 that best match each other. 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 taking lens 5 corresponding to the given subject distance, and sets the taking lens 5 at the calculated focal position. In this way, automatic focus adjustment is performed.

Next, switching of the sensitivity of the line sensor will be described. Sensitivity switching is configured to switch according to the brightness of the brightness of the subject. Further, not only the brightness but also the light source at that time is detected and the sensitivity is switched to a sensitivity suitable for the characteristics of the light source. . The brightness of the subject can be detected by an output from the AE photometric device shown in FIG. Further, as shown in FIG. 4, the output from the light receiving portion 33a of the line sensor 31 is input to the sensor light amount detection means 104, and the output is given to the sensor sensitivity determination means 102 so that the brightness of the subject is detected. Good. As yet another example,
As shown in FIG. 5, by arranging the light receiving element 103 having a shape substantially equal to the length of the line sensor 31 in the vicinity where the light receiving portions 33a of the line sensor 31 are arranged, and inputting the output thereof to the sensor sensitivity determining means. The brightness of the subject may be detected. In consideration of the fact that the light source contains a pulsating light component such as a fluorescent light, the average value of a plurality of measurements is adopted as the photometric value.

In the above examples of the brightness detecting means, since the detecting means already provided is also used for detecting the brightness, it is not necessary to newly provide a dedicated detecting means. In the configuration that uses the output of the light receiving unit of the line sensor, since the same data as the data for distance measurement can be used, it is possible to accurately measure the luminance of the subject that is the measurement target. In the configuration in which the monitor light-receiving element provided near the distance-measuring light-receiving unit is used for luminance detection, the luminance detection area and the distance-measuring sensor detection area are substantially equal, so the deviation of the detection area is minimized. Can be suppressed.

Next, the structure for switching the sensitivity in the line sensor will be described. 6 and 7 show only one of the line sensor and the sensor sensitivity determining means in the block diagram shown in FIG. The first embodiment shown in FIG. 6 has a configuration in which a plurality of storage units having different capacities are provided as the charge storage unit 33b, and charges are stored in any one of the storage units according to an instruction from the sensor sensitivity determining unit 102. By accumulating, the sensitivity of the line sensor can be switched. For example, when the sensitivity is set to be low, the accumulation time is lengthened by accumulating charges in the accumulation unit 112 having a large capacity.
On the contrary, when the sensitivity is set high, the storage unit 11 having a small capacity is used.
Switch to accumulate charge in 1. That is, when the sensitivity is low, the time until a predetermined amount of charge is accumulated becomes long, and when the sensitivity is high, the time becomes shorter. With this configuration, since there is no switching of the light receiving elements, there is an effect that a detection error such as a variation in sensitivity due to switching of the light receiving elements or a change in the squint position of the subject due to the sensitivity does not occur.

An example of each circuit when the storage section is switched will be described with reference to FIGS. 8A and 8B.
FIG. 8A shows a circuit when the sensitivity is set low, the switch T5 is temporarily in a conductive state at the start of charge accumulation, and the charges generated by the light reception by the light receiving element 115 are stored in the light receiving element 115. It is stored in the internal capacity. Then, as the charge is accumulated, the potential of the negative input terminal of the comparator 116 rises and is compared with the positive input terminal voltage Vref of the comparator 116 to detect that the accumulated charge has reached a predetermined amount. . Here, the electric charge is stored by the potential difference Vref.

FIG. 8B shows a circuit when the sensitivity is set to high. When the charge accumulation is started, the switch T1 becomes conductive, and the initial potential at the negative input terminal b of the comparator 123 becomes Vref-V0 (where V0 <Vref).
Then, the charges generated in the light receiving element 121 are accumulated in the internal capacitance thereof, and the potential at the point b rises accordingly. Comparing the potential at the point b with the predetermined potential Vref by the comparator 123 determines the completion timing of charge accumulation.

As another embodiment, FIG. 7 shows a configuration in which a plurality of light receiving portions having different light receiving areas are provided as the light receiving portion 33a so that the sensitivity can be switched.
When the sensitivity is set low, the light receiving section 15 has a small light receiving area.
Light is received at 1, and when the sensitivity is set to high, the light receiving portion 152 having a large light receiving area receives light. When the light receiving area is small, it takes a long time to reach a predetermined amount of the electric charges accumulated in the accumulating portion, and when the light receiving area is large, a large amount of electric charges are obtained, so the time is short. With this configuration, there is no variation in the capacitance between pixels as compared with the case where the capacitance of the storage unit is switched, and it is possible to accurately detect a waveform corresponding to the brightness of the subject.

As yet another embodiment, the light receiving portion 33a
An amplifier circuit is provided between the storage unit 33b and the storage unit 33b, and the sensitivity of the sensor is switched by switching the amplification factor of the amplifier circuit. When the sensitivity is set low, the amount of charge sent to the storage unit is reduced by decreasing the amplification factor and the integration time is lengthened. Conversely, when the sensitivity is set high, the amplification factor is increased. .

In any of the above sensitivity switching examples, the configuration is made so as to eliminate the influence of the pulsating light, so that the charge accumulation time is less than a half cycle of the pulsating light or more than one cycle at any luminance. Is configured. Therefore, the fluctuation of the accumulation time due to the pulsating light can be minimized.

Next, the sensitivity switching control of the line sensor will be described. The flowchart shown in FIG. 9 is for the case where the line sensor can be switched between two types of sensitivity, high sensitivity and low sensitivity. This flowchart is executed when a distance measuring operation is instructed. First, step # 11
At, the brightness of the subject is measured. Here, in consideration of the fact that the light source contains the pulsating light component, the measurement is performed a plurality of times and the average value is adopted as the luminance. Then, it is determined whether or not the measured subject brightness is less than a predetermined value (step # 13). When it is determined that the subject brightness is less than the predetermined value, the sensitivity of the line sensor is set to low sensitivity and integration is performed (step # 15). With the low sensitivity, the accumulation time becomes sufficiently longer than the period of the pulsating light, so that the influence of the pulsating light can be eliminated. On the other hand, when it is determined that the subject brightness is equal to or higher than the predetermined value, the sensitivity of the line sensor is set to high sensitivity and integration is performed (step # 17). With high sensitivity, the accumulation time becomes sufficiently short with respect to the period of the pulsating light, so that the influence of the pulsating light can be eliminated. Then, the distance to the subject is calculated from the data obtained by the integration with low sensitivity or high sensitivity (step # 19), and this distance measuring sequence is ended. After that, if the photographing lens is moved according to the calculation result, a focused state can be obtained for the measured subject.

In the above example, the line sensor whose sensitivity can be switched in two steps is shown as an example, but a sensor which can switch the sensitivity in three steps or more may be used. In that case, depending on the brightness of the subject, the higher the brightness, the higher the sensitivity, and the darker the brightness, the lower the sensitivity.

Next, an example will be described with reference to FIG. 10 in which, in addition to the case classification shown in FIG. 9 above, an extremely low brightness and an extremely high brightness are detected to switch the sensitivity. To do. Here, control is performed such that high sensitivity is set when the brightness is extremely low, and low sensitivity is set when the brightness is extremely high. The relationship among the first to third predetermined values K1, K2, and K3 that appears here is K1 <K2 <K3. First, the brightness of the subject is measured (step # 3
1) Next, it is determined whether or not the measured brightness is less than the first predetermined value K1. If it is less than the predetermined value, it is determined that the brightness is extremely low, the brightness is set to high brightness to accumulate charges (step # 35), and the distance is calculated from the obtained data (step # 47). This is because there is a problem that if the charge is stored with low sensitivity for a subject having extremely low brightness, the integration time becomes too long and the release time lag becomes long, so the sensitivity is made high. When it is determined in step # 33 that the brightness is equal to or higher than the predetermined value K1, it is determined in step # 37 whether the brightness is less than the second predetermined value K2. When it is determined that the value is less than the predetermined value K2, the sensitivity is set to low and integration is performed in step # 39. If the brightness is not less than the predetermined value K2, the process proceeds to step # 41, and it is determined whether the brightness is less than the third predetermined value K3. If it is less than the predetermined value K3, high sensitivity is set and integration is performed in step # 43. In step # 43,
If it is determined that the brightness is not less than the predetermined value, step # 4
In step 5, low sensitivity is set and integration is performed. This is because the brightness is determined to be extremely high and the sensitivity is set low.

At high brightness, step # 17 in FIG. 9 or
Although the high sensitivity is set and the accumulation time is shortened as in step # 43 of FIG. 10, here, when the brightness is extremely high, the sensitivity is set low as in step # 45. When the sensitivity is set to be extremely high at an extremely high brightness, a predetermined amount of charge is stored in many pixels, so that the storage time becomes the same and accurate waveform data cannot be obtained. Therefore, by setting the sensitivity to low when the brightness is extremely high, the time until the predetermined amount of charge is accumulated becomes longer, and the charge accumulation time according to the brightness in each pixel is obtained and accurate waveform data is obtained. . Although the time is longer than the accumulation time at high sensitivity, it is sufficiently shorter than the period of the pulsating light, so the adverse effect of the pulsating light can be eliminated and overflow can be prevented. .

When the brightness is low, the sensitivity is set to be low as in steps # 15 and # 39 so that the accumulation time becomes long. However, here, when the brightness is extremely low, like step # 35. High sensitivity is set. When the sensitivity is set to be extremely low at extremely low brightness, the accumulation time becomes long, which causes a problem that the time from the distance measurement to the actual photographing becomes long. Therefore, when the brightness is extremely low, the sensitivity is set to be high, but the accumulation time is shortened, but since the time is sufficiently longer than the period of the pulsating light, the influence of the pulsating light can be eliminated. Furthermore, the time lag can be shortened by shortening the accumulation time.

Next, the control for switching the sensitivity depending on the type of light source will be described with reference to FIG.
First, in step # 51, the type of light source is determined. In this embodiment, it is detected whether it is a fluorescent lamp.
This is because, as a method of detection, for example, the luminance measurement is performed a plurality of times using a photometric element for AE, and if the output includes a variation of a predetermined amount or more, the light source includes pulsating light. It is determined that it is a fluorescent lamp. Next, in step # 53, the brightness of the subject is measured. Then, in step # 55, it is determined whether or not the light source is a fluorescent lamp. If it is not a fluorescent lamp, if the subject brightness is brighter than a predetermined brightness, the sensitivity is set to low sensitivity, and if not, the sensitivity is set to high sensitivity and integration is performed (steps # 57, 5).
9, 61). When it is determined that the light source is a fluorescent lamp,
If the subject brightness is brighter than the specified brightness, set to high sensitivity,
Otherwise, the sensitivity is set low and integration is performed (steps # 63, 65, 67). Then, the subject distance is calculated based on the integrated data obtained with the respective sensitivities (step # 69). In this way, if the light source is only ambient light, the sensitivity is set in the same manner as in the past, and if a light source containing pulsating light such as a fluorescent lamp is included, the sensitivity is set in reverse, The distance can be measured accurately according to the type.

[0046]

As described above, according to the distance measuring system of the present invention, when the brightness is higher than the predetermined brightness, the sensitivity is high.
Since the sensitivity of the light receiving element is set to be low when the brightness is lower than a predetermined level, even if the light source contains a pulsating light component, the charge accumulation is sufficiently shorter or longer than the pulsating current cycle. Since it takes time, it is possible to eliminate the measurement variation caused by the pulsating flow even if the light source includes the pulsating flow component, and it is possible to accurately measure the object distance.
The sensitivity is set so that the charge accumulation time is a half cycle at a short time with respect to the cycle of the pulsating light at any brightness, or a cycle of at least one cycle at a long time. Even if the sensitivity of the light receiving element can be switched in three steps or more, if the sensitivity is set higher as the brightness becomes higher and the sensitivity is set lower as the brightness becomes lower, the sensitivity can be switched more finely according to the brightness. Can measure distance. Further, by providing a means for detecting the type of the light source, it is possible to detect whether or not the pulsating flow light is included in the light source, so that accurate distance measurement can be performed regardless of the type of the light source.

As the brightness measuring means, a photometric light receiving element,
Since it can also be used as a distance measuring light receiving unit, a monitor light receiving element provided in the vicinity of the distance measuring light receiving element, and the like, it is not necessary to newly provide a dedicated detecting element. When the light-receiving unit for distance measurement is used, the same data as the data for distance measurement is used, so that the luminance of the distance measurement target can be measured extremely accurately.
Even when the monitor light receiving element is used, since the light from the substantially same region as the distance measuring light receiving unit is received, the luminance of the distance measuring object can be accurately measured.

[Brief description of drawings]

FIG. 1 is an external view of an autofocus camera to which a distance measuring system according to an embodiment of the present invention is applied.

FIG. 2 is a schematic configuration diagram of an autofocus camera to which a distance measuring system according to one embodiment of the present invention is applied.

FIG. 3 is a configuration diagram showing details of a distance measurement IC and a distance measurement calculation control device.

4 is a configuration diagram of another embodiment of the configuration shown in FIG.

5 is a block diagram of another embodiment of the configuration shown in FIG.

FIG. 6 is an explanatory diagram of a configuration for switching the sensitivity of the line sensor.

FIG. 7 is an explanatory diagram of a configuration for switching the sensitivity of the line sensor.

FIG. 8 is a circuit diagram in the configuration of FIG.

FIG. 9 is a flowchart showing a distance measuring sequence of the first embodiment in the distance measuring system.

FIG. 10 is a flowchart showing a distance measuring sequence of the second embodiment in the distance measuring system.

FIG. 11 is a flowchart showing a distance measuring sequence of a third embodiment of the distance measuring system.

FIG. 12 is an explanatory diagram of a problem to be solved by the present invention.

[Explanation of symbols]

2 Optical system 3 Distance measuring IC 4 Distance measurement calculation control device (calculation means) 21, 22 Lens 31, 32 Line sensor (light receiving element array) 100 AE photometry device (luminance measurement means) 101 Light source determination means (light source detection means) ) 102 sensor sensitivity determining means (sensitivity setting means, control means) 103 monitor light receiving element 104 sensor light receiving amount detecting means

Claims (7)

[Claims] 1. A pair of optical systems for forming an image of a subject, a pair of light receiving element arrays arranged on substantially respective image forming planes of the optical system and having a plurality of light receiving sensitivities, An arithmetic means for calculating the distance to the subject from the output signal, a luminance measuring means for measuring the luminance of the subject, a sensitivity setting means for setting the sensitivity of the light receiving element array from the output of the luminance measuring means, and a subject luminance A distance measuring system comprising: a control unit that controls the sensitivity to be set higher when the brightness is higher than a predetermined brightness and to be low when the brightness is lower than the predetermined brightness. 2. The measurement according to claim 1, wherein the control unit sets sensitivity such that the higher the subject brightness is, the higher the sensitivity is, and the lower the subject brightness is, the lower the sensitivity is. Distance system. 3. The distance measuring system according to claim 1, further comprising light source detection means for detecting the type of the light source, and determining the sensitivity of the light receiving element from the subject brightness and the type of the light source. 4. The distance measuring system according to claim 1, wherein the brightness measuring unit is a photometric light receiving element. 5. The distance measuring system according to claim 1, wherein the brightness measuring unit is at least one of the pair of light receiving element arrays. 6. The distance measuring system according to claim 1, wherein the brightness measuring unit is a light receiving element provided near the light receiving element array. 7. The distance measuring system according to claim 1, wherein the light receiving sensitivity of the light receiving element array is set such that the charge accumulation time is equal to or shorter than a half cycle of a predetermined cycle or equal to or longer than one cycle. .