JPH0198913A - Photodetection sensor for range finding - Google Patents

Abstract

PURPOSE:To obtain the sensor which is free from variation of reflected light with the distance of a subject, cross talk, etc. by adjusting the width of photodetectors arrayed in a base length direction in the same direction and setting a photoelectric output at the time of photodetection above a constant level when reflected light arrives from a distance measurement area that each photodetector faces. CONSTITUTION:A subject distance area as an object of distance measurement is divided into distance measurement areas and the photodetectors S1-S6 are arrayed in the direction of the base length L corresponding to them to constitute a photodetection sensor 9. Then the width of the elements S1-S6 in the direction of the base length L is so set that when reflected light beams from subjects at the farthest positions and closest positions in the corresponding areas are incident, the same photoelectric outputs are obtained. Therefore, wherever a subject is in a distance measurement area corresponding to a photodetector on which reflected light is incident, a photoelectric output is obtained which is larger than a constant output larger than the photoelectric outputs from subjects at the farthest position and closest position in the area. This is converted into a binary signal to eliminate the superposition of a false signal under the influence of crosstalk, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a light receiving sensor used in an active type distance measuring device.

[Conventional technology]

Active type distance measuring devices, which are often used in recent compact cameras, project a light beam for distance measurement toward the subject, and a light receiving sensor receives the reflected light from the subject. There is. The light-receiving sensor has multiple tiny light-receiving elements arranged in the baseline length direction, and it electrically identifies which of the light-receiving elements the reflected light from the subject is incident on, and measures the distance corresponding to the subject distance. I'm trying to get a signal.

In the distance measuring device described in Japanese Patent Publication No. 55-33005, a plurality of light-receiving elements are arranged in the base line length direction, and a constant reference potential is applied to each light-receiving element. A ranging signal is obtained by detecting whether reflected light is incident on the light receiving element.

Furthermore, in the distance measuring device described in JP-A-54-119267, it is possible to not only identify which of the light-receiving elements arrayed as described above has received the reflected light from the subject, but also identify the two adjacent light-receiving elements. When reflected light is incident across one or three light receiving elements, it is devised so that a distance measurement signal corresponding to an intermediate subject distance when it is incident on each light receiving element can be detected.

Furthermore, in the distance measuring device described in Japanese Patent Application Laid-Open No. 56-29112, when photoelectric outputs appear from a plurality of light receiving elements,
By changing the reference voltage of the comparator connected to each of the light-receiving elements based on the maximum level of photoelectric output, generation of false signals due to crosstalk and the like is avoided.

[Problem that the invention seeks to solve]

However, in the distance measuring device disclosed in Japanese Patent Publication No. 55-33005, if the reference potential is determined according to the light receiving element on the far side that receives weak reflected light from a distant object, the light receiving element on the near side When strong reflected light enters an element, false signals are generated not only from a specific light-receiving element but also from adjacent light-receiving elements due to effects such as crosstalk.
The disadvantage is that it is easy to mismeasure the distance.

In addition, in the distance measuring device disclosed in Japanese Patent Application Laid-Open No. 54-119267, when the reflected light from the subject enters two adjacent light receiving elements, a light receiving signal "1" is output from each of the two light receiving elements. We must make sure that it is done. Therefore, the center light receiving element among the three light receiving elements lined up is
In addition to the case where the reflected light is incident on only one of them, the situation where the reflected light is incident on both sides of the light receiving elements is also included.
The light receiving signal “I” is transmitted from the light receiving element over a certain distance range.
6 However, since the intensity of the incident light usually changes at the upper and lower limits of the distance range, in reality, simply arranging multiple light receiving elements is not sufficient. Distance measurement function cannot be obtained.

Furthermore, the distance measuring device disclosed in Japanese Patent Application Laid-Open No. 56-29112 has the drawback that the configuration of the signal processing circuit used in connection with the light receiving sensor is complicated, resulting in high cost.

[Purpose of the invention]

The present invention has been made to solve the problems of the prior art as described above, and is not affected by changes in reflected light intensity due to distance from a subject or crosstalk, etc. It is an object of the present invention to provide a light receiving sensor for distance measurement without complicating a processing circuit.

[Means for solving problems]

In order to achieve the above object, the present invention configures a light receiving sensor that receives reflected light from a subject and outputs a distance measurement signal corresponding to the light receiving position. Distance measurement-4~ A light-receiving sensor is constructed by dividing into areas, and arranging a plurality of light-receiving elements in the baseline length direction so as to correspond to these distance-measuring areas, and determining the width of each of these light-receiving elements in the baseline length direction. When the reflected light from the object at the farthest position in the corresponding distance measurement area is incident, and when the reflected light from the object at the shortest position in the corresponding distance measurement area is incident, the photoelectric output level is the same. The width is set so that the output can be obtained.

[Effect]

According to the above configuration, when reflected light from a subject enters a specific light-receiving element, no matter what distance position the subject is in the distance-measuring area corresponding to that light-receiving element, the shortest position in the distance-measuring area Alternatively, since a photoelectric output larger than the photoelectric output when the subject is at the farthest position can be obtained, a photoelectric output at a certain output level or higher can be reliably obtained regardless of the subject distance.

An embodiment of the present invention will be described below with reference to the drawings.

〔Example〕

In FIG. 2, which schematically shows a distance measuring optical system using the light receiving sensor of the present invention, a light projecting section 2 includes a discharge tube 3 that emits near-infrared light. A slit plate 4 that shapes the light from the discharge tube 3 into a slit shape. It consists of a light projecting lens 5. In addition, the light receiving section 7 is
Light receiving lens 8. It is composed of a light receiving sensor 9.

The optical axes 5a and 8a of the light projecting lens 5 and the light receiving lens 8 are parallel to the optical axis 10a of the photographing lens 10, and are separated by the base line length. The light receiving sensor 9 includes small horizontally rectangular light receiving elements 81 to S, as will be described in detail later.
6 are arranged in the direction of the base line length.

When a slit light is emitted from the light projector 2 toward the subject, a portion of the light is reflected by the close subject 12, and the reflected light 12a enters the light receiving element S3 through the light receiving lens 8. Furthermore, when a part of the slit light is reflected from the middle-distance object 13 or the long-distance object 14, the reflected light 1
Each of 3a and 14a is a light receiving element 32. It comes to be incident on SL. Therefore, the distance to the subject can be determined by detecting which light receiving element of the light receiving sensor 9 receives the reflected light from the subject. Note that when a slit light is used as the light beam for distance measurement in this way, the light beam for distance measurement will be irradiated even when the main subject is off the center of the shooting screen, so that it will be possible to This eliminates the need for troublesome operations such as aiming operations and reframing after distance measurement, but distance measurement can also be performed by projecting spot light instead of slit light.

Figure 3 shows the distance range from close range to infinity.
This shows the position where the photographing lens 10 can be set, and the photographing lens 10 is 0.855 m.

Ten positions are set with the optimum focusing positions being 0.935m, 1.05m...5.86m. Here, if the diameter of the permissible circle of confusion is set to 0.025 mm, even if the set position of the photographic lens 10 is 0.855 m, the distance range from 0.807 to 0°893 m will be the focusing range. I can see it = 7-.

When the set position of the photographic lens 10 is set in this way, the distance measurement areas R1 to R6 shared by the light receiving elements 5l-36 are
is as shown in the table below.

As is clear from the above table, the ranging areas R1 to R5 partially overlap. Therefore, reflected light from objects located at a distance of, for example, 1.5 m from the overlapping objects enters both of the light receiving elements S2 and S3. A photoelectric output will be obtained from S3. Note that the light-receiving element S6 is used for short-range warning, and when a photoelectric output appears only in this light-receiving element S6, this is used as a warning signal.

As shown in FIG. 4, the light receiving sensor 9 is connected to a signal processing circuit 15 for use. The signal processing circuit 15 is
For example, the circuit configuration is as shown in FIG. 5, and each photocurrent signal from the light receiving elements S1 to S6 is converted into a voltage signal by an operational amplifier in the first stage. This voltage signal also includes a DC component, that is, a photoelectric signal caused by external light such as sunlight, but since a capacitor for cutting low frequency components is connected to the output terminal of each operational amplifier in the first stage, it is possible to Only the high frequency components of the photoelectric signal are input to the operational amplifier. The photoelectric outputs each amplified at a constant amplification factor by the next-stage operational amplifier are supplied to signal input terminals of comparators 17a to 17f, respectively.

The reference voltage input terminals of the comparators 17a to 17f are provided with reference voltages Vr+ to Vr6 obtained by the voltage divider 8.
is applied. These reference voltages Vr+ to ■r6 are determined by ■rI×vr2<
...〈It is decided to be vr6. As a result, when reflected light from a subject enters any of the light receiving elements 81 to S6, the corresponding comparators 17a to 1
A signal output "1" appears at the output end of 7f, and a signal output "o" appears at the output end where no reflected light is incident.

By the way, as described above, the light receiving elements 31 to S5 each receive reflected light from a subject within the ranging areas R1 to R5 having a certain width, and the comparator 1 responds to this.
It is necessary to obtain a photoelectric output that causes the output terminals of 7a to 17f to output a signal output of "1". Therefore, the width DI-D5 of the light receiving elements 31 to S5 in the base line length direction is determined as shown in FIG. In FIG. 1, the right end of the light receiving element S1 is the farthest position of the ranging area R1.
, 27 meters away from the subject. The detection level of the photoelectric output at this time is set as a level at which the second-stage operational amplifier output of the signal processing circuit 15 is two to three times larger than the noise level.

After determining the right end of the light-receiving element S1 in this way, move the subject to the nearest position of the distance measurement area R1, 2.19 m,
The left end of the light receiving element S1 is determined at a point where a photoelectric output equal to the initial detection level can be obtained, and thereby the width D1
Determine. For example, after determining the right end position of the light receiving element S1 and moving the test subject to a position of 4.27 m, the mask covering the front surface of the light receiving element S1 is opened in the baseline length direction, and the detection level is This corresponds to the amount of movement of the mask when the photoelectric output is obtained. Of course, instead of performing such a simulation, it is also possible to determine the width D1 by computer analysis.

After determining the width D1 of the light receiving element S1 in this manner, the right end of the next light receiving element S2 is brought close to the left end of the light receiving element S1, and the subject is placed at the farthest position of the ranging area R2, that is, at a position of 2.86 m. After measuring the detection level of the photoelectric output at that time, the subject is moved to the nearest position 1. in the distance measurement area R2.
46 m, and determine the closest end of the light receiving element S2 at the point where the photoelectric output at that time matches the measured detection level. As a result, the width D2 of the light receiving element S2 is determined, and the width D3 of each of the light receiving elements S3 to S5 is determined in the same manner.
~ Decide on D5. Note that it is also possible to provide an appropriate gap at each boundary without bringing the light receiving elements 81 to S5 into close contact with each other.

Binarized signal outputs A1 to A6 appearing at the output terminals of the comparators 17a to 11f are supplied to an AF control circuit 20. FIG. 6 shows an example of the AF control circuit 20. This AF control circuit 20 is activated, for example, by pressing the shutter button halfway. Power ■. When C is applied, a reset pulse is output from the reset pulse generation circuit 23 after waiting for the stabilization of the power supply VCC, which resets the RS flip-flop circuit FFO that controls the opening and closing of the AND gate 24, and outputs a signal to the ζ terminal. "1" appears,
AND gate 24 is opened.

The microcomputer 22 in FIG. 4 outputs a clock pulse to the AF control circuit 20 after a delay of 100 m5ec from the input of the shirt button half-press signal. This clock pulse is supplied to counter 25 through AND gate 24 .

A decoder 26 is connected to the counter 25.
6 controls the distance measurement sequence in accordance with the clock pulse count value of the counter 25. The decoder 26 includes one D flip-flop circuit DFF1 to DFF for latching the signal output AI-A6 from the signal processing circuit 15.
6 (hereinafter simply referred to as DFFI to DFF6)
, and reset the shift register 28. After that, A
F) Output the trigger pulse to the strobe control circuit 29.

The strobe control circuit 29 is constructed as shown in FIG. 8, and the discharge tube 3 emits light when the AF trigger pulse is supplied to the terminal T. After the AF trigger pulse is output, when the counter 25 counts the clock pulses for a predetermined period of time until the strobe light from the discharge tube 3 reaches its peak, a predetermined clock pulse that takes into account the variation in the rise time of the strobe light is counted. A read pulse with a time width is output from the decoder 26. This read pulse is input to one of the AND gates G1 to G6 connected to the clock terminals of DFF1 to DFF6. Therefore, while the AND gates G1 to G6 are opened by the read pulse, if there is a signal value "1" among the signal outputs A1 to A6 from the signal processing circuit 15, the corresponding one of DFF1 to DFF6 is detected. will be set.

Among DFFI to DFF6, a signal "1" appears at the Q terminal of the one set by the signal value "1" among the signal outputs A1 to A6, and this is input to the shift register 28.
It is stored in a predetermined bit location. Therefore, for example, the signal values of signal outputs A1 to A6 are "ra", "ro", and "rl".
, ro”.

rIJ, rQ", the shift register 28
The distance measurement data of ``roololo'' is stored in . After outputting the read pulse, the decoder 26
outputs a shift pulse to the shift register 28. As a result, the distance measurement data stored in the shift pulse 28 is sequentially transferred to the microcomputer 22.

After outputting a predetermined number of shift pulses to the shift register 28, the decoder 26 outputs a ranging completion signal. This ranging completion signal is supplied to the set terminal of the FFO via the inverter 29, thereby putting the FFO in the set state. As a result, the output from the FFO terminal becomes "0", the AND gate 24 is closed, and the distance measurement sequence is completed.

The microcomputer 22 compares the distance measurement data input from the AF control circuit 20 with the AF element table 0 to determine the set position of the photographic lens 10. AF child table 0
is constructed as shown in FIG. 7, and includes light receiving elements 31 to S6.
In addition to the light reception pattern, that is, the distance measurement data described above, the set position of the photographing lens 100 is determined in consideration of the object brightness data (EV value) detected by the photometry circuit 31. This is to accommodate the fact that the maximum aperture diameter of the program shutter changes depending on the EV value, so that the depth of field can be utilized to the maximum extent. Note that N, , N in the AF child table 0 in FIG.

,...,N,. The lens set positions represented by are 0, 855m, 0.935m, etc. shown in Figure 3.

This corresponds to the lens set position where the optimum focusing position is 5.86 m.

When the lens set position is determined in this manner, the microcomputer 22 outputs a number of drive pulses corresponding to the lens set position to the motor drive circuit 32. As a result, the stepping motor 33 rotates by a predetermined amount, and the photographing lens 1
0 is moved to the determined lens set position.

The AF element table 0 also stores control data for a built-in strobe 35 that provides auxiliary illumination to a low-brightness subject, that is, light emission timing data for the built-in strobe 35, as shown enclosed by a broken line. And the lens set position is A
In the case determined by the data surrounded by the broken line in the AF element table 0, when the program shutter reaches the aperture diameter stored in the AF element table 0 due to the operation of the shutter drive circuit 36, the microcomputer 22 performs strobe control. A light emission trigger signal is output to the circuit 37, and the built-in strobe 35 is operated to emit light. Note that FIG. 8 shows an example of the strobe control circuit 29, where terminal T is a charging inhibit signal input terminal, terminal T2 is a charging start signal input terminal, and terminal T3 is an A terminal.
The charging completion signal output terminal of the F discharge tube 3 and the terminal T4 are the light emission trigger signal input terminals of the built-in strobe 35, and are connected to the microcomputer 22, respectively. Further, the terminal T is used as an input terminal for the AF trigger pulse outputted from the AF control circuit 20.

〔Effect of the invention〕

As explained above, in the distance measuring light receiving sensor of the present invention, the width in the baseline length direction of the plurality of light receiving elements arranged in the baseline length direction is adjusted, and the distance measurement area that each light receiving element looks into is adjusted. If it is the reflected light of In addition, there is no need to complicate the signal processing circuit for binarization.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the outline of the configuration of a light receiving sensor using the present invention and the correlation of photoelectric output. FIG. 2 is a schematic diagram of a distance measuring optical system using the present invention. FIG. 3 is an explanatory diagram showing the relationship between the set position of the photographic lens and the distance measurement area. FIG. 4 is a block diagram showing the circuit configuration of the distance measuring device. FIG. 5 is a circuit diagram showing an example of the signal processing circuit used in FIG. 4. FIG. 6 is a circuit diagram showing an example of the AF control circuit used in FIG. 4. FIG. 7 is a conceptual diagram of an AF element table that determines the lens set position. FIG. 8 is a circuit diagram showing an example of the strobe control circuit used in FIG. 4. 2... Light projecting unit 7... Light receiving unit 9... Light receiving sensors S1 to S6... Light receiving elements R1 to R6... Ranging area 10... Photographing lens 15... Signal processing circuit 20... AF control Circuit 30...AF child table

Claims (3)

[Claims] (1) A light projector that projects a beam of light toward the subject, and a light receiving sensor that is placed apart from the light projector by a certain baseline length and that receives the light that is reflected by the subject out of the light beam that is projected onto the subject. In the distance measuring device, the distance measuring range is divided into a plurality of distance measuring areas, and the light receiving sensor is configured by arranging a plurality of light receiving elements corresponding to the distance measuring areas in the baseline length direction, and The width of each light-receiving element in the baseline length direction is determined by measuring the width of the light reflected from the subject at the farthest position in the distance measurement area corresponding to that light-receiving element, and when the light is reflected from the subject at the shortest position in the distance measurement area. A light-receiving sensor for distance measurement, characterized in that the width is set such that a photoelectric output of approximately the same output level can be obtained when light is incident. (2) The light receiving sensor for distance measurement according to claim 1, wherein each of the distance measurement areas partially overlaps with an adjacent distance measurement area. (3) The distance-measuring light-receiving sensor according to claim 2, wherein the width of each of the light-receiving elements in the base line length direction is determined based on a long-distance side.