JPH0473762B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field to which the Invention Pertains] The present invention is a photoelectric distance measuring device, which is incorporated into an optical instrument such as a camera, and measures the distance to an object such as a copy using a photoelectric sensor and an electronic circuit. The present invention relates to a device for measuring by a combination device.

[Prior art and its problems]

This type of device has been known for a long time, but
In particular, in recent years, the measuring device has been developed as a purely electronic device that has no moving parts at all.
49884 New devices such as those disclosed by others have appeared,
It is attracting attention as a compact, inexpensive, and highly accurate distance measuring device.

The principle of this type of device is shown in FIGS. 1 and 2. In Figure 1, an object 1 whose distance d is to be measured
The light emitted by, for example, the reflected light of sunlight, is transmitted through a pair of small lenses 2, 3 with a short focal length f, which are installed in the optical instrument with a base distance b between them.
The light enters through two optical paths 4 and 5 that are spatially different from each other. The object 1 has a luminous intensity distribution shown by two chevrons in the figure, and images 7 and 8 of the object having such a luminous intensity distribution are formed on a common focal plane 6 by the small lenses 2 and 3. be done. In this figure, to make the explanation easier to understand, the center of the object 1, and therefore the center 1C of its luminous intensity distribution, is the small lens 2.
The center 7C of the image 7 on the focal plane 6 formed by the small lens 2 is located at the position 70, and the position 70 of the image center remains unchanged even if the distance d to the object 1 changes. Of course it doesn't change. On the other hand, when the distance d to the object 1 is infinite, the center 8C of the image 8 formed by the small lens 3 is at a position 80 on the focal plane 6 directly facing the lens 3, as is easily seen; As the distance d becomes smaller, the image shifts to the left in the figure, and when the positional relationship shown in the figure exists, the image center 8C is located at a position 81 on the focal plane 6 at a distance x from the original position 80.

Now, on the focal plane 6, there are small lenses 2,
Photosensor arrays 10 and 11 are provided at positions that receive images 7 and 8 of object 1 from image sensor 3. These photosensor arrays 10, 11 generally consist of mutually different numbers m, n of photovoltaic elements or photosensitive resistive elements, each element in the array having a function related to the amount of light it receives, e.g. It emits an electrical signal proportional to , as shown in Figure 2a and b. If we can now measure the distance x of the forward deviation by some means, we can determine the distance d to the object 1 using the formula d=b·f/x based on the principle of simple triangulation.

Now, since the signals output by each element in the optical sensor arrays 10 and 11 have analog values as shown in FIG. It has a pattern of Although this analog value may be used as is to obtain the aforementioned deviation distance x, it is usually quantized into a digital value in order to simplify the electronic circuit and improve accuracy. The simplest quantization method is to convert the analog value to an appropriate threshold voltage Vt and
An analog value larger than the threshold value Vt is set as "1" and an analog value smaller than the threshold value Vt is set as "0" and converted into a 1-bit digital value as shown in c and d of the same figure. Next, by comparing the digital value distributions as shown in FIG. It can be measured as a value expressed as The distribution of digital values represented by the chain line in d of the same figure is
The distance d to object 1 is infinite, so the amount of deviation x
corresponds to 0, and it can be seen from this that measuring the distance d ultimately results in finding the distance x on the optical sensor array shown in d of the same figure expressed in terms of the number of elements.

In the example of FIG. 1, if the optical axis of the not-illustrated viewfinder that selects the object 1 for which the distance d is to be determined coincides with the optical axis of the small lens 2, that is, if the small lens 2 is attached to the object 1 as described above. Although the case where they face each other has been described, in general, the optical axes of the viewfinder and the small lens do not coincide with each other. If the viewfinder is now located between the two small lenses 2 and 3, the images 7 and 8 on both optical sensor arrays 10 and 11
are shifted to the right and left by distances x ₁ and x ₂ , respectively, from the original position when object 1 is at infinity. However, even in this case, x=x ₁ + x ₂
By doing so, the distance d to the object 1 can be found using the exact same relational expression as mentioned above, so that measuring the distance d comes down to finding the amount of shift x between the images on both sensor arrays. There is no change.

FIG. 3 is a block diagram showing an example of an electronic circuit for measuring the above-mentioned deviation amount x expressed in the number of optical sensor elements. Normally, the entire electronic circuit shown including the optical sensor array section is It is integrated on one semiconductor chip. The photosensor array unit 100 shown by the dashed line in FIG. 3 includes a left photosensor array 100L and a right photosensor array 100R, and the image formed by the small lens described above is The photoelectric output signals are sent to the left analog-to-digital converter (hereinafter referred to as ADC) 300L and the right ADC 30 in the quantization circuit 200.
0R and 0R, respectively, as shown by the arrows in the figure. In this signal transmission, the output signals of each photosensor element may be sent serially to the ADC, or may be sent in parallel. In these ADCs 300L and 300R, the analog signal from each photosensor element is converted into a digital value of 1 bit or a desired number of bits, and then stored in the attached registers 400L and 400R, respectively.
Send it to memorize it. These registers may be, for example, shift registers, which have the same number of stages as the photosensor arrays 100L, 100R and whose quantization is performed in the same order as the light intensity distribution in the image entering the photosensor array. When the output of the above-mentioned ADC in which the digital value stored is multi-bit, the above-mentioned shift register is constructed by, for example, as many binary shift registers arranged in parallel as there are signal bits. At this stage, the distribution of digital values is shifted by the number of shift register stages corresponding to the shift amount x between the left and right images received by the optical sensor arrays 100L and 100R, and is stored in both shift registers 400L and 400R.

A distance detection circuit 500 is provided to find the number of stages of deviation in the digital value distribution in the shift register corresponding to the above-mentioned deviation amount x. Initially, the digital values stored in both the left and right registers 400L and 400R are sent to the comparison circuit 600, and it is checked for each stage of the shift register whether or not the digital values stored in the left and right registers match. The comparison result storage circuit 700 stores the number of times that the values match. If there is a deviation in the distribution of the digital values stored in both registers, the value of the above-mentioned number of coincidences stored in the comparison result storage circuit 700 will naturally be small. Next, both registers 400L,
After the digital storage value in one of the registers 400R is shifted by one stage relative to the other, the comparator circuit 600 checks whether the digital values in both registers match or differ for each stage in the same manner as described above. When the number of matches is greater than the previous number of matches stored in the comparison result storage circuit 700, the number of matches stored in the comparison result storage circuit 700 is rewritten to a new number of matches, and the distance signal calculation circuit 800 A pulse is sent to the counter inside, causing it to add one to its stored value, which was initially reset to zero. Thereafter, in the same manner, the digital values in both registers 800L and 800R are shifted by one stage by one step and compared by the control pulse CP from the central control circuit 900, but the comparison results are stored in the storage circuit 700. If the new number of matches is smaller than the previous number of matches, the memory value of the number of matches is not updated, and the distance signal calculation circuit 80
It is not added to counters that are 0. After the above-mentioned comparison is made a predetermined number of times in this way, the count value remaining in the counter in the distance signal calculation circuit most closely represents the distribution of the digital values originally stored in both registers. This indicates the number of stages of deviation necessary for good matching, and the number xn of optical sensors corresponding to the desired deviation amount x can be found.

The distance signal calculation circuit 800 calculates the amount of deviation x or the distance d to be finally determined based on the optical sensor converted deviation number xn based on a predetermined formula, and calculates the amount of deviation x or the distance d to be finally determined based on the distance signal readout pulse from the central control circuit 900. A distance signal is sent out, and the central control circuit 900 sends out this distance signal to the outside in response to a call from an external device.

The distance measuring device constructed as described above, which is a purely electronic type with no moving parts, is gaining popularity due to its small size, low cost, and high accuracy in distance measurement, but when you actually see the device in operation, However, it was found that there were various problems.

One of these is when the brightness of the object whose distance is to be measured is low, for example, when it takes a negative EV value, and
In this case, since the amount of light entering the optical sensor arrays 10, 11 in FIG. 1 or the same arrays 100L, 100R in FIG. The threshold value Vt when quantizing the signal shown in Figure 2 is not reached or is only at the very limit, so the results of distance measurements using such quantized digital signal values are not sufficiently reliable. That's true. This problem can be solved by using an optical signal accumulation type sensor as the optical sensor, but since it takes time to accumulate the signal, it is difficult to measure the distance, as in the case of a video camera where the field of view of the camera is moved while capturing images. If it takes a long time to measure, it will become completely unapplicable if the measurement becomes meaningless. Therefore, if an image is taken while keeping the distance measurement time within the required limit, the image will be taken under incorrect focusing conditions based on the incorrect distance measurement result, resulting in blurring of the shot image.

On the other hand, even if the object is sufficiently bright, if there is almost no contrast between light and dark within the object, it will be difficult to measure distance even from the measurement principle described above, and if there is no contrast at all, the measurement will fail. It becomes possible. In such a case, no matter what threshold value is used to quantize the output signal of the optical sensor, a pattern of digital signal values necessary for distance measurement cannot be obtained.

On the other hand, even when the object is very bright, errors may occur in the distance measurement results. The difference between light and dark in the camera's field of view is generally very large, and the brightness in bright areas is often 10 degrees greater than the brightness in dark areas, so it is necessary to vary the threshold during quantization over such a wide range. It is difficult. Even when an object is very bright and there is a contrast between light and dark inside it,
Most of the information exceeds the threshold for quantization, and it becomes impossible to obtain any information on the contrast between light and dark, or the information becomes extremely small. In either case, the digital output from the ADC 300 in Figure 3 will have insufficient pattern information of "0" and "1", and no matter how accurately the digital circuit operates, the distance measurement results obtained will be It becomes uncertain. Attempts have been made to increase the amount of light and dark pattern information by converting the output of the ADC into not only 1-bit information but also multi-bit information, but such methods are not possible when the properties of the target object are unsuitable as mentioned above. Not necessarily valid.

In addition, if two or more objects at different distances enter the field of view of the optical sensor array, or if the object has a regular light and dark pattern, such as a striped or checkered pattern, the digital circuit will connect the left and right optical sensors. It faithfully searches for the point where the pattern information from the array matches the most and outputs distance measurement data.
A case may occur in which a plurality of distance measurement results exist, and it becomes impossible to determine which measurement data should be regarded as the correct result.

[Purpose of the invention]

In view of the above-mentioned points, the present invention provides an image of an object to be distance-measured formed via two spatially different optical paths, which are each formed by a plurality of optical sensors.
Two video signal streams are generated that represent the light intensity distribution within the image received by a pair of optical sensor arrays, and the two video signal streams are successively compared while being shifted from each other in a quantized state to generate both video signal streams. When measuring the distance to an object based on the amount of shift when the maximum match occurs, when the characteristics of the object to be measured are unsuitable for distance measurement and sufficient measurement data cannot be obtained,
It is an object of the present invention to provide a photoelectric distance measuring device that can prevent erroneous measurement results from being used by detecting from each video signal of a video signal sequence for distance measurement.

[Key points of the invention]

In order to achieve the above object based on the drawbacks of the prior art described above, the present invention organizes the problems of the prior art and takes countermeasures against them. The first is that the optical properties of the target object, such as being very dark or having no contrast, are inherently unsuitable for distance measurement, and therefore distance measurement is virtually impossible. There are cases. In such a case, even if distance measurement is impossible, it is necessary to at least notify the optical instrument or equipment that uses the distance measurement results. In order to detect such a situation, the present invention particularly utilizes video signal sequences emitted by a pair of optical sensor arrays that receive images of objects. The video signal sequence used for this detection may be the signal itself emitted by the optical sensor, or may be a signal after quantizing the signal. In order to detect that measurement is virtually impossible from such a signal sequence, it is advantageous to focus on the maximum video signal value and minimum signal value in the signal sequence rather than taking the average value of the signal sequence. .
If the maximum video signal value in both signal trains does not reach the required predetermined value in one or both of the signal trains, measurement is essentially impossible, so it is determined that measurement is not possible from the maximum video signal value. It can be detected, and conversely, it is possible to avoid the risk of determining that measurement is not possible when measurement is possible. By taking the difference between the maximum value and the minimum value of the video signal for one or both of the signal sequences, it is possible to detect that the contrast of the light intensity of the object is too low to make distance measurement possible. Furthermore, although it is possible to easily find such maximum and minimum values by using digitalized video signal values, it is possible to easily find the maximum and minimum values by using digitalized video signal values, but it is possible to easily find the maximum and minimum values by using digitalized video signal values. It is advantageous to work in converted form. The maximum and minimum values of the pulse width can be found using a simple OR gate or AND gate. Furthermore, it is advantageous to make this pulse width especially inversely proportional so that it decreases with increasing video signal.
As a result, even if there is a variation of several orders of magnitude in the light intensity distribution of the image, such variation can be contained within a relatively small pulse width range, and moreover, the above-mentioned logic gate can suppress the variation within a short period of time. This is because the length of the pulse applied to the pulse can be accurately determined. A first means in the present invention detects that the above-mentioned measurement is substantially impossible and generates a first signal.

Next, according to an embodiment of the present invention, there is provided a second means for detecting that there are a plurality of shift amounts that make the two video signal sequences match each other to the maximum, and emitting a second signal to that effect. This second method deals with cases where even if the first method described above cannot detect the object, multiple distance measurement results occur due to the optical properties of the target object, and therefore the results are incorrect. This is a confirmed case. In this case, just because the results are uncertain does not mean that they are not immediately available. Depending on the purpose of using distance measurement, it is often sufficient to select a result suitable for the purpose from among a plurality of distance measurement results, for example, the shortest distance among the results. Therefore, in the present invention, a second signal indicating that a plurality of measurement results exist is issued separately from the above-mentioned first signal. Optical instruments and users who use the distance measurement results can also know multiple measurement results along with this second signal, so they can select the most suitable result from the multiple measurement results based on the second signal. can be selected and used. It is advantageous to use a shift register to detect the existence of a plurality of measurement results. Since the degree of coincidence between two video signal streams is measured for various amounts of shift, a shift register with the same number of stages as the amount of shift used to test the degree of coincidence is provided, and the shift register is set to correspond to the amount of shift for which the maximum match is obtained. A logical value, for example "1", indicating that maximum matching has been obtained can be stored in the stage with the number. The presence of a plurality of maximum matches can be detected by sending a read pulse to this shift register and calculating the number of logic values successively output from the end of the shift register. Furthermore, it is advantageous in this case to detect whether a plurality of maximally coincident displacement amounts, ie, a plurality of measurement results, are present successively for subsequent tampering amounts or discontinuously for mutually spaced displacement amounts. Optical instruments and users can select and use the result that best matches their purpose from multiple measurement results based on the signal indicating the existence of multiple measurement results and the signal indicating whether the distribution is continuous or discontinuous. can.

As described above, by emitting the second signal indicating that there are multiple measurement results separately from the first signal indicating that measurement is virtually impossible, there is no chance of distance measurement using only one type of signal. Even in cases where measurement results are lost, the chances of the measurement results being used can be increased.

[Embodiments of the invention]

In explaining the embodiments of the present invention in detail below,
First, the main points of the digital circuit according to the present invention for calculating distance measurement data will be explained with reference to FIG.

FIG. 4 shows the portion after the register 400 in FIG. 3, which in this embodiment is configured as a shift register through which digital values pass, rather than a register for storing digital values.
The shift register 410 in the figure corresponds to the register 400L on the left side of FIG. Digitized image data of an object from the ADC 300L in FIG. 3 is serially input to the first stage 411 and stored in the same order as the arrangement of the photosensors in the photosensor array 100L. The video data stored in the shift register 410 is sequentially shifted to the left in the figure by the control pulse CP issued by the central control circuit 900, and the stages from stage 41m to stage 41n (assuming n>m)
, the digital values in the stage are output in parallel as shown. As can be easily seen, such parallel outputs will be n-m+1. On the other hand, the other shipto register 420 corresponds to the register 400R on the right side of FIG. Digitized object image data from the ADC 300R in FIG. 3 is serially input to the first stage 421 and stored in the same order as the arrangement of the photosensors in the photosensor array 100R. The video data stored in this shift register 420 is sequentially shifted to the left in the diagram by control pulses CP issued by the central control circuit 900. The output from this shift register 420 is serially output only from the final stage 42m.

Stage 41m of the shift register 410 described above
n-m+1 parallel output data from ~41n and the final stage 42 of shift register 420
The serial output data from m is the comparison circuit group 6.
00, where they are compared with each other simultaneously and in parallel. This comparison circuit group 600 consists of n-m+1 comparison circuits 60m to 60n, and further includes a fifth
As shown in the figure, each of the comparison circuits 60m to 60n consists of an exclusive NOR gate 610, an OR gate 620, and a counter 630, respectively. For example, the exclusive NOR gate 610 of the comparison circuit 60i (i=m to n) receives data I1 from the stage 41i (i=m to n) of the shift register 410 and data I2 from the stage 42m of the shift register 420. The output “1” is output only when both data match. This output passes through an OR gate 620 to a counter 630.
Take one step forward. The above operation is shown in Figure 3.
Digitized video data from the ADCs 300L and 300R are sent to shift registers 410, respectively.
and 420 , the central control circuit 900
The stage 411 is controlled by the control pulse CP emitted from the
and 421 video data are stage 41m and 4
2m, and the counter 630 of each comparator circuit 60m to 60n contains both input data I1 and I2 to the exclusive NOR circuit.
The number of times the numbers match is stored as a count value.
As can be easily seen, the comparison circuit 60m compares the image data received by the optical sensor arrays 100L and 100R in FIG. A matching circuit when comparing left and right video data with zero deviation is stored. Similarly, the comparison circuit 60
The counter 630 in the comparison circuit to the left of m is the number of matches when the left and right video data are compared with a deviation of 1, and the counter 630 in the last comparison circuit 60n is the number of matches when the left and right video data are compared with a deviation of 1. - The number of times of matching when compared after being shifted by m optical sensors is stored. As a result of the above, the comparison circuit 60m to 60m
Each of the counters 630 up to n stores the number of times n-m+1 pieces of data match, which are obtained by comparing the left and right video data by shifting them by 0 to n-m.

As described above, the left and right video data are
Since a comparison result with a shift of -m has been obtained, next the number of shifts for which the maximum number of matches is stored in the comparison results is found. Therefore, the timing control circuit 9 in FIG. 4, which corresponds to the central control circuit 900 in FIG.
The read clock pulse P62 from 10 is simultaneously input to the OR gate 620 of each comparator circuit 60m-60n as shown in FIG. Of course, each counter 630 has a sufficient number of stages to store the maximum number of matches of the comparison results described above, and the stored contents have not reached the point where the final stage overflows.
The readout clock pulses P62 that have passed through the OR gate 620 are successively incremented all at once, and the count value overflows from the counter 630 that has stored the maximum number of matches, and a carry output is output from the carry output terminal of the counter shown in FIG. C is emitted.
The carrier output C from the counter 630 of each comparison circuit 60m to 60n is the comparison result storage circuit 7 of FIG.
The signals are input in parallel to stages 70m to 70n of the nm+1 stage shift register 700 in FIG. 4 corresponding to 00 and stored. In addition, each counter 630
The output C from the counter 630 is also input in parallel to the OR gate 650 as shown in the figure, and the OR gate 650 opens the gate when a carry output is generated from any one of the counters 630 and outputs the timing control circuit 91.
Notify 0 of this fact. Timing control circuit 91
0 immediately stops issuing the read clock pulse P62 when it learns that this carry output has been issued. As a result, each counter 63
Since the increment of 0 stops and no further carry output is generated, only the stage corresponding to the counter 630 which had stored the maximum number of matches in the shift register 700 stores the carry output, for example "1". becomes. Of course, if there are two or more counters 630 that store the maximum number of matches,
Correspondingly, a plurality of stages in the shift register 700 will store the logical value "1".

In this embodiment, the distance signal calculation circuit 800 is configured as a simple counter, and is configured as a count clock pulse P8 from a timing control circuit 910.
0, and the read shift pulse P70 applied to the shift register 700 synchronized with the pulse P80 causes even one logic value 1 to be changed from the stage 70m of the shift register 700.
progress immediately stops when is output. As a result, the counter 800 stores the number of deviations indicating the maximum match between the left and right video data.
This stored value is read by the central control circuit 900 in FIG. 3, by the timing control circuit 910 in this embodiment, and outputted to the outside as a distance signal.
However, as can be seen from the above explanation, even if the shift register 700 stores the logical value "1" indicating maximum coincidence in a plurality of stages, the minimum number of deviations among them is output as a distance signal. This will result in

In the circuit for calculating the distance signal as described above, the distance signal may become uncertain due to various reasons as described above. Embodiments of the present invention will be described in detail below for each factor that makes the distance signal uncertain. In the following examples, the first main that outputs the first signal indicating that distance measurement is virtually impossible is shown in FIGS. 6 and 11, and the first signal is used as DA, DB, Expressed as DC and DD. Further, the second means for outputting a second signal indicating that there is a plurality of shift amounts for maximally matching both video signal sequences is connected to the first means.
2, and the second signals are represented by DE, DF and DG.

FIG. 6 shows a circuit for detecting the uncertainty in the distance signal that occurs immediately after the power to the distance measuring device of the present invention is turned on. capacitor 9
53, and the potential V at the connection point between the resistor 952 and the capacitor 953 increases as shown by V in FIG. The potential V is the inverter 9 used as a threshold element.
54, and the output of inverter 954
As shown in _FIG .
After becoming larger than the threshold value Vth of 4, it remains "0". Furthermore, since the signal _S1 is input to the one shot circuit 955 which outputs a pulse at the falling edge of the input, the output _S2 of the one shot circuit 955 is as shown in FIG. Since the output S ₂ is further input to the set terminal S of the flip-flop 956, the output DA of the flip-flop 956 indicates that the output potential V of the integrator circuit is equal to the threshold voltage of the inverter 954.
It becomes “1” when it reaches Vth. The aforementioned distance measuring circuit is activated by the signal _S2 and starts measuring operation, and when the measuring operation is completed, a CLR signal whose waveform is shown in FIG. 7 is sent from the timing control circuit 910 to the reset terminal R of the flip-flop 956. Then, the output DA of the flip-flop 956 becomes "0". That is, flip-flop 956
The fact that the output DA is "1" indicates that although the distance measuring circuit is performing a measuring operation, the measurement result is unreliable.

Next, an embodiment of the present invention will be described for a case where distance measurement is practically impossible due to the optical conditions of the object. FIG. 8 shows one optical sensor and ADC 300 in the optical sensor array 100 of FIG.
This is a specific circuit of an embodiment of the present invention corresponding to one of the conversion elements, and in this example, the optical sensor is shown as a photodiode 110. In the figure, a photodiode 110 converts the intensity of incident light L into the intensity of photocurrent i. The photocurrent i charges the capacitor 120 and the output voltage of the capacitor 120
As shown in FIG. 9, VC increases with a slope corresponding to the magnitude of photocurrent i. capacitor voltage VC
is input to the inverter 150 used as a threshold element, and the output Q of the inverter 150 is sent to the discharge transistor 130 from the timing control circuit 910 as a reset pulse P10 whose waveform is shown in FIG. When the capacitor voltage VC reaches the threshold value Vth of the inverter 150, it becomes "0". The width tm of this pulse of the output Q of the inverter 150 becomes a signal representing the light intensity L (tm is approximately inversely proportional to L). In other words, the optical sensor circuit shown in FIG. 8 starts measuring the light intensity upon receiving the reset pulse P10, and outputs a pulse Q having a pulse width tm representing the light intensity. Of course, the output from the optical sensor is input to a signal converter 300 as shown in FIG. 3 and converted into digital values as video data.

Now, FIG. 10 and FIG. 11 are circuits for detecting a malfunction in the output Q of such a photosensor, and FIG. 101L~10
Similarly, n photosensors 101R to 10nR forming the right photosensor array 100R are shown. In response to the above-mentioned reset pulse P10, these optical sensors start measuring the light intensity all at once, and output a pulse Q having a pulse width representing each light intensity. These pulse outputs Q are input to left inverter groups 961L to 96mL and right inverter groups 961R to 96nR, respectively. Further left inverter 961
The output of L~96mL is the left AND gate 97.
It is input in parallel to AL and the left OR gate 970L, and similarly to the right inverter 961R~9
The output of 6nR is input in parallel to the right AND gate 97AR and the right OR gate 97OR. As you can easily see, the left AND gate 9
The output AL of 7AL is from the left optical sensor group 101L.
The output pulse Q from 10 mL has the inverted waveform of the longest pulse width, and the output OL of the left OR gate 97OL has the inverted waveform of the shortest pulse width. Similarly, the right AND gate 97
The output AR of the AR is from the right optical sensor group 101R to
This is the inverted waveform of the longest pulse width among the output pulses Q from 10nR, and the output of the right OR gate 97OR is the inverted waveform of the shortest pulse width.

The outputs AL, AR of these AND gates and the outputs OL, OR of the OR gates are input to the circuit of FIG. 11 as shown. In the circuit shown in FIG. 11, the signals OL and OR are ORed by an OR gate 981 and input to a timer 982. From the above description, the optical sensor arrays 100L and 100R
The time from the start of operation by the reset pulse P10 until the output of the OR gate 981 becomes "1" is the time for the optical sensors 101L to 10mL, 101
It is easily understood that the response time is the same as the shortest response time of R to 10nR, that is, the time tm until the output Q is output. timer 982,
If the timekeeping operation is started by the reset pulse P10 mentioned above and stopped by the output of the OR gate 981, the shortest pulse width mentioned above can be achieved.
When tm exceeds a predetermined value, timer 982 issues an output DB. Now, since the pulse width tm is almost inversely proportional to the light intensity in the optical sensor circuit shown in FIG. This means that the light intensity is weaker than a predetermined light intensity. On the other hand, the signals AL and AR are input to a NAND gate 983. Similarly to the above, the time when the output of this NAND gate 983 is "1" is determined by the optical sensors 101L to 10mL, 101.
It is the same as the one with the longest response time among the outputs Q from R to 10nR. Furthermore, since the output of this NAND gate 983 and the output of the aforementioned OR gate 981 are ANDed by an AND gate 984, the time during which the output of this AND gate 984 is "1" is the optical sensor 101L to 10mL, 101R.
It is equal to the difference between the longest response time and the shortest response time among the outputs Q from ~10nR. In other words, the duration of the output of the AND gate 984 (the time during which the output is "1") indicates the difference between the strongest and weakest light intensities, which means the contrast of the image of the object. . Therefore,
The output of this AND gate 984 is input to the timer 985 whose time counting contents have been cleared by the above-mentioned reset pulse P10, and the timer 985 is caused to perform a timing operation while the output of the AND gate 984 is "1". When the duration of the output of the AND gate 984 is less than a predetermined value, that is, when the contrast in the image of the object is less than a predetermined value and the distance measurement operation is difficult, the timer 985 is caused to generate an output signal DC.

The circuit shown in the lower part of FIG. 11 is for detecting a case where there is an extreme difference in the light intensity of two objects that fall within the field of view of the optical sensor array. As shown, the signal OR is inverted by a inverter 986 and ANDed with the signal AL by an AND gate 987. The signal AL becomes "0" by the reset pulse P10, and the left optical sensors 101L to 1
It returns to "1" only when the one with the longest response time among the 0 mL responds, that is, when all of the left photosensors respond, and the inverted signal of the signal OR is set to "1" by the reset pulse P10. 1”,
When the one with the shortest response time among the right photosensors 101R to 10nR responds, that is, if any one of the right photosensors responds, it becomes "0", so the AND gate 987 The output signal is output from the left optical sensor 101L to 10.
This means that none of the right photosensors 101R to 10nR responded even though all of the mL responded. That is, the output of the AND gate 987 is the left photosensor array 100L.
The light intensity of the image of the object received by is extremely stronger than the light intensity received by the right photosensor array 100R,
This means that distance measurement operation is virtually impossible.
Similarly, as shown, the signal AR and the inverter 988
The AND gate 989 that takes an AND with the inverted signal of the signal OL outputs an output because the light intensity received by the right photosensor array 100R is extremely stronger than the light intensity received by the left photosensor array 100L. This means that distance measurement is virtually impossible. Note that when the AND gate 987 or 989 outputs an output, the OR gate 990 opens and sets the flip-flop 991, which had been reset by the reset pulse P10, to output the signal DD. The output of such a signal DD occurs not only when there is an extreme difference in the light intensity of two objects in the field of view of the optical sensor array as described above, but also when there is severe contamination in the optical system of one of the optical sensor arrays. It is also useful for detecting cases where the optical system is accidentally covered.

Next, FIG. 12 shows a circuit for detecting that a logical value indicating the maximum coincidence of left and right images is stored in a plurality of stages of the shift register 700 in the distance measuring circuit system of FIG. 4 described above. . In such a case, it means that there are multiple conclusions that the distance measurement circuit has calculated as the correct distance, and it is naturally impossible to select which one is the true one within the distance measurement circuit, but the distance measurement result It is necessary to make a selection based on some kind of separate judgment on the part of the optical instrument or the user, such as adjusting the focus of the camera using . However, the fact that there are multiple measurement results requires that the optical equipment receiving the distance signal and the user be at least informed of the fact that there are multiple measurement results. That is, it is clearly insufficient to output only the longest distance among a plurality of measurement results, or conversely the shortest distance, as a measurement result.

The circuit shown in FIG. 12 is designed to not only detect the existence of a plurality of measurement results, but also to detect the condition of their distribution. 700 in the figure is the shift register shown in FIG. 4, and the memory contents therein are read from the right side by the read shift pulse P70, and the shift register 700 is shown in FIG. 4 as the aforementioned distance signal calculation circuit. It is output to counter 800. The flip-flop 1001 in the figure receives the output from the shift register 700, and is set when the logic value "1" stored in a certain stage is output. When the output from the next shift register 700 becomes a logical value “0”,
AND gate 10 between this inverted output from inverter 1002 and the output of flip-flop 1001
03 is satisfied, its output becomes "1", and the next flip-flop 1004 is set. Thereafter, when the output of the shift register 700 becomes "1" again, the AND condition of the AND gate 1005 is satisfied, and the next flip-flop 1006 is set by the output "1". From the above, the fact that the output of the last flip-flop 1006 becomes "1" means that a plurality of "1"s are stored in the shift register 700 and "0"s exist between them, that is, a plurality of distance measurements. It means that the result exists, and that it exists discontinuously. In the above description, it is assumed that flip-flops 1001, 1004 and 1006 have all been reset before receiving the output signal from the shift register.

Furthermore, the counter 1007 in FIG. 12 is a binary counter that counts how many "1"s are stored in the shift register 700, that is, how many distance measurement results there are. When the count value reaches 2, the output terminal Q1 becomes "1" and flip-flop 1008 is set. Furthermore, when the count value reaches 4, the output terminal Q2 of the next stage becomes "1", and the flip-flop 1009 is set. The output of this flip-flop 1009 is a signal DG, which means that there are four or more distance measurement results. Also, the AND gate 1010 in the figure is the inverter 10 of the flip-flop 1006 described above.
11 and the flip-flop 100
8 and the inverted signal of the signal DG by the inverter 1012, the output signal DE of the AND gate 1010 is output when the distance measurement results are 2 or more (output of flip-flop 1008) or less than 4 (output of flip-flop 1009). (inverted output),
This also means that the distance measurement results are continuous (inverted output of flip-flop 1006). Similarly, the AND gate 1013 is connected to the flip-flop 1
Since the output of 006, the output of flip-flop 1008, and the inverted output of flip-flop 1009 are ANDed, the output DF has two or more distance measurement results but less than four distance measurement results, and the distance measurement results are discontinuous ( (output of flip-flop 1006).

Information indicating the existence of a plurality of distance measurement results as described above can be used in various ways. For example, when distance measurement results are used for focusing a camera, if there are four or more measurement results, the measurement results are considered completely unreliable, and the camera's shutter operation is prohibited using the signal DG, and the camera's viewfinder is The fact that the distance measurement is uncertain can be displayed by known means to notify the user. If there are two or more distance measurement results but less than four, that is, two or three, it is possible to decide which of the signals to use for automatic focusing based on the properties of the optical instrument. For example, if there are two measurement results and they are consecutive, focus on the closest distance, and if there are three measurement results and they are consecutive, focus on the center distance of the three. can do. In addition, if two measurement results are discontinuous, the distance can be adjusted to the closest distance between the two measurement results. In any case, such selection may vary depending on the optical characteristics of the optical instrument that uses the distance measurement results and the purpose of use of the user, and can be easily determined in advance according to the characteristics and purpose. It should be noted that the method of outputting signal information when a plurality of distance measurement results exist does not need to be limited to the above-mentioned embodiments, and can be appropriately selected and configured by those skilled in the art within the scope of the present invention. Of course.

〔Effect of the invention〕

According to the present invention as described above, each video signal in a video signal train for distance measurement is converted into a pulse signal whose starting point is synchronized and has a pulse width that decreases in accordance with an increase in the light intensity. a converting means; a gate means for inputting a plurality of pulse signals converted by the converting means; and detecting and outputting a pulse signal with the shortest width or a pulse signal with the longest width among the pulse signals; and a detection output of the gate means. and an impossibility detection means for detecting a state in which distance measurement is substantially impossible based on and emitting a first signal indicating this, and converting the video signal into a pulse signal with a pulse width corresponding to the light intensity. This makes it possible to easily detect the strongest or weakest light intensity using a gate means, and based on the detection output, it can be determined that distance measurement is virtually impossible with respect to the light intensity or contrast of the object. Since the failure detection means is used to detect the distance, it is possible to easily and reliably detect cases where the characteristics of the object to be measured are unsuitable for distance measurement and sufficient measurement data cannot be obtained from each video signal of the video signal sequence for distance measurement. Detection can be made to more reliably prevent erroneous measurement results from being used.

[Brief explanation of drawings]

Figures 1 to 3 all show conventional techniques, of which Figure 1 is an explanatory diagram of the principle of a photoelectric distance measuring device, and Figure 2 is an explanatory diagram of the principle of a photoelectric distance measuring device.
This figure is an explanatory diagram of a method for quantizing analog signals from an optical sensor array, and FIG. 3 is a block diagram showing the overall configuration of a photoelectric distance measuring device. Figures 4 to 12
All the figures show embodiments of the present invention, of which Figure 4 is a block diagram showing the main part of the distance measuring circuit of the photoelectric distance measuring device according to the present invention, and Figure 5 is a comparison circuit 60m to 60n in Figure 4. 6 is a circuit diagram showing a specific circuit for emitting the first signal DA immediately after the power is turned on as the first means, and FIG. 7 is a circuit diagram for explaining the operation of the circuit shown in FIG. 6. waveform diagram for,
FIG. 8 shows a specific circuit example of one optical sensor (one of the optical sensors 101L to 10mL and 101R to 10nR shown in FIG. 10) in the optical sensor array as part of the first means. The circuit diagram, Fig. 9 is a waveform diagram for explaining the operation of the circuit shown in Fig. 8, and Fig. 10 is a detection state in which distance measurement due to the image of the object as the first means is virtually impossible. FIG. 11 is a circuit diagram of a specific circuit for detecting the first signal DB, DC and
FIG. 12 is a circuit diagram showing an example of a specific circuit that emits DD, which detects the existence of multiple distance measurement results as a second means and generates second signals DE, DF and
FIG. 3 is a circuit diagram of a specific circuit example that emits DG. In the figure, 100L, 100R... optical sensor array, 101L ~ 10mL, 101R ~ 10nR
...Light sensor, 300, 300L, 300R...
Analog-digital converter for quantizing video signals, 400L, 400R, 410, 420...Shift register as a register for storing quantized video signal strings, 600...Comparison for comparing two video signal strings Circuit group, 60m to 60n...Comparison circuit, 610...Exclusive NOR gate for detecting coincidence of video signals, 630...Counter for storing the number of coincidences of video signals in two video signal sequences, 700...2 Shift register 97AL that stores the shift amount for maximally matching video signal sequences;
97AR...AND gate that detects the maximum value in the video signal, 97OL, 97OR...OR gate that detects the minimum value in the video signal, 1006...Indicates that there are multiple measurement results and they occur discontinuously. Flip-flop for storing, 1007...Counter for counting multiple measurement results, DA,
DB, DC, DD...first signal, DE, DF, DG...
...the second signal.

Claims (1)

[Scope of Claims] 1. An image of an object to be distance-measured formed via two spatially different optical paths is received by a pair of optical sensor arrays each consisting of a plurality of optical sensors, and an image within the image is received. Create two video signal streams representing the light intensity distribution of a converting means for converting each video signal in the video signal train into a pulse signal whose starting point is synchronized and whose pulse width decreases in accordance with an increase in the light intensity; gate means for inputting a plurality of pulse signals converted by the means and detecting and outputting a pulse signal with the shortest width or a pulse signal with the longest width among the pulse signals; and a distance measurement based on the detection output of the gate means. A photoelectric distance measuring device comprising: impossibility detection means for detecting a substantially impossible condition and emitting a first signal indicating the fact. 2. In what is stated in claim 1,
The gate means detects the shortest width pulse signal of the video signal in each video signal train for each of the two video signal trains, and the failure detection means detects the shortest width pulse signal in either of the two video signal examples. A photoelectric distance measuring device characterized in that it emits a first signal when the width of the pulse signal is equal to or greater than a predetermined value. 3 In what is stated in claim 1,
The gate means detects the shortest width pulse signal of the video signal in each of the two video signal trains, and the failure detection means detects the shortest width pulse signal in one of the video signal trains. A photoelectric distance measuring device characterized in that the first signal is emitted when the widths of all the signals are equal to or greater than a predetermined value. 4 In what is stated in claim 1,
The gate means detects the shortest width pulse signal and the longest width pulse signal of the video signals in the two video signal streams, and the failure detection means detects the shortest width pulse signal and the longest width pulse signal. A photoelectric distance measuring device, characterized in that it emits a first signal when a difference in signal width is less than or equal to a predetermined value. 5 In what is stated in claim 1,
The gate means detects the shortest width pulse signal and the longest width pulse signal of the video signals in the video signal trains for each of the two video signal trains, and the failure detection means detects one of the video signal trains. A photoelectric distance measuring device, characterized in that the first signal is emitted when the difference in width between the shortest width pulse signal and the longest width pulse signal is less than or equal to a predetermined value. 6 In what is stated in claim 1,
The gate means detects a pulse signal with the shortest width and a pulse signal with the longest width of the video signal in the video signal train for each of the two video signal trains, and the failure detection means detects the pulse signal with the shortest width and the pulse signal with the longest width of the video signal in the video signal train. A photoelectric type characterized in that the first signal is emitted when the width of the longest pulse signal of the signal is shorter than the width of the shortest pulse signal of the video signal in the other video signal train. Distance measuring device. 7. In any one of claims 1 to 6, the gating means detects the pulse signal with the shortest width using an OR gate, and detects the pulse signal with the longest width using an AND gate. A photoelectric distance measuring device characterized by: