JPH03102211A - Projecting-type distance measuring apparatus - Google Patents

Abstract

PURPOSE:To process irregular photo-electric converting outputs by constituting an attenuating means by a light shielding member moving in front of a photodetecting element, and selecting the distance to an object to be photographed on the basis of the position of said attenuating means. CONSTITUTION:A light projected from a light emitting element 1 is condensed by a projecting lens 2, and the light beam 3 is directed to an object 8 to be photographed. The light 4 reflected from the object 8 forms a light spot on a point of a photodetecting element 6 through a light receiving lens 5. A light shielding plate 7 moves from the right to left with a certain correlation kept with the distance to the object 8. When the light shielding plate 7 traverses the optical axis 4, the reflecting light from the object 8 is obstructed and does not reach the element 6, so that the photoelectric output of the element 6 is attenuated. Further, when the light shielding plate 7 completely passes the optical axis 4, the output is returned to the original level. The distance to the object 8 is measured at a point where a negative peak is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a distance measuring device suitable for small cameras and the like.

[Prior Art] Various optical projection type distance measuring devices that utilize the principle of triangular distance have been proposed.

Among these, the distance measuring device (Japanese Patent Application No. 124268/1982) already proposed by the applicant is a device that changes the photoelectric output of the light receiving element by scanning a light shielding plate over the surface of a single light receiving element. This is a system that detects and measures distance.

Hereinafter, this will be referred to as a light shielding plate scanning type distance measuring device.

[Problems to be Solved] No processing circuit suitable for a light-shielding plate scanning distance measuring device has been proposed. In particular, no circuit measures were taken to deal with irregular photoelectric conversion outputs.

SUMMARY OF THE INVENTION An object of the present invention is to provide a processing circuit suitable for a light-shielding plate scanning distance measuring device, and also to provide a circuit that is capable of processing irregular photoelectric conversion outputs.

[Example] Embodiments will be described below with reference to the accompanying drawings.

FIG. 1 is a diagram showing the principle of a light-shielding plate scanning type light projection type distance measuring device.

1 is a light emitting element, 2 is a light projection lens, and 3 is a light projection axis. 4
indicates the reflected optical axis from the subject 8, 5 is the light receiving lens, and 6 is the light receiving lens.
is a light receiving element. 7 is a light shielding plate that scans the surface of the light receiving element. 9 is a camera body incorporating the above distance measuring device.

To explain the operation, the light emitted from the light emitting element 1 is condensed by the light projecting lens and hits the subject 8 as a light beam, and the reflected light is focused by the light receiving lens 5 on one point on the light receiving element 6 as a light spot. Image.

On the other hand, the light shielding plate 7 scans from right to left in the figure in a certain correlation with the distance to the subject. When the light-shielding plate 7 crosses the optical axis 4, the reflected light from the subject is blocked and does not strike the light-receiving element 6, and the photoelectric output of the light-receiving element 6 is attenuated.

When the light shielding plate 7 passes the optical axis 4, the output increases to the original level again.

This relationship is shown in FIG. 2, where the point 1p that has a negative peak is the distance to the subject. The farther the subject is, the more
The position of the light spot formed on the light receiving element 6 in the figure is shifted to the left.

FIG. 3 is an example of a mechanism of a distance measuring device that is incorporated into a camera together with the control circuit of the present invention.

In the figure, 11 is a release lever, and a spring 12
is forced upward by. 17 is a scanning plate;
There is a light shielding plate 17a that scans the surface of the light receiving element 16. Further, the scanning plate 17 is urged rightward by a spring 18, but is locked by a locking member 13 and a spring 14. 19 is a gear, and 20 is an ankle, which controls the traveling speed of the scanning plate. 21 is a control lever, which is given a clockwise rotational habit by a spring 22;
It engages with the bin 17c on the scanning plate 17 and rotates. Reference numeral 23 is an electromagnet, 24 is an iron piece, and a spring 25 acts in a direction that separates the electromagnet. A spring 26 biases the shutter forward lever in the right direction. Reference numeral 30 denotes a stepped cam for determining the amount of extension of the objective lens, and is given a counterclockwise rotational habit by a spring 32. Reference numeral 33 is a contact piece, which selects a resistor 36 according to the extension of the objective lens, and is used as distance information for flashmatic and the like.

Figure 4! This is one embodiment of the control circuit in the distance measuring device of the present invention.

In the figure, PD is a light receiving element, and the first stage intensifier A
1 converts the short circuit current into voltage. R1 is a feedback resistor. C1 is an AC coupling capacitor, and A2 is a second-stage amplifier for AC amplification. C2 and R3 are feedback capacitors and resistors. D1 is a detection diode, R6 and C3 are an integrating resistor and capacitor, R5
is the discharge resistance. A3 is a voltage follower, A4 is an integral output DC amplifier, R7 is an input resistor, and R8 is a feedback resistor. SH is a sample and hold circuit, A5 forms a differential amplifier, and the input resistors are R10 and Rll. CPI is a comparator, the integral output is input to the non-inverting input, and the capacitor C6 and resistor R1 are input to the inverting input.
7 is connected, and a diode D3 is connected between the inputs to form a clamp circuit. The output of the converter CPI is connected to the transistor Tri. R13,
C5 is a resistor and capacitor for the second integration circuit. A
6 is an inverting amplifier, the output of which is connected to the non-inverting input of coverator CP2.

PSD is a positive slope detection circuit, and its output and the output of the comparator CP2 enter an OR circuit OR, which is further connected to a flip-flop FF. Tr2 is a transistor for the ranging electromagnet Mg$ilIn. CP3
is a converter, the first integral output is input to the non-inverting input, and the inverting input is connected to a bleeder consisting of resistors R19 and R20. ANDI and AND2 are AND gates, NV is an inverter, and S2 is a switch that is turned on when the scanning plate is close to the point where scanning is completed. Tr3 is a transistor for controlling the warning LED, and Tr4 is a transistor for controlling the electronic buzzer B. OSC is an oscillator.

TME is a timer circuit, which is triggered by the shutter release switch S3 and controls the operation of the IRED drive circuit DRV. I RED is an infrared light emitting diode for light projection, and is pulse driven by transistor Tr5. S1
is the power switch.

Next, the operations shown in FIGS. 3 and 4 will be explained.

The operating waveforms of each part of the circuit are shown in FIG.

When the release lever 11 is pressed down, the power switch S1
power is supplied to each part of the circuit, the light receiving circuit is put into operation, and the light emitting IRED is pulse-driven by constant periodic pulses from the driving circuit DRV. When the release lever 11 is further pushed down, the scanning plate 1 is moved by the locking member 13.
7 is released, and the scanning plate 17 starts scanning at a constant speed in the direction of the arrow in the figure by the governors 19 and 20. FIG. 5 SCP shows the operation of the scanning plate 17, where n is the close range. When the light-shielding plate 17a scans the light-receiving element 16 and begins to block the light spot on the light-receiving element, the waveform of the output (2) of the AC amplifier A2 changes in amplitude as shown in FIG. This AC signal is detected by diode D1, R6 and C3
When integrated by , the waveform amplified by amplifier A4 is ■
It becomes a dip waveform as shown in . Furthermore, the waveform passed through the sample-and-hold circuit SH becomes step-like as shown in (■).

When the waveforms of ■ and ■ are input to the operational amplifier A5, an output of ■ is obtained. Here, the clamp circuit is CP1, D3, C6, R
17, but the inverted input waveform of CPI is ◎
As shown, the circuit has a fall delay with respect to the dip waveform shown in (2) above. When ■≧O, the transistor Tr1 is turned on to clamp the output of the operational amplifier A5. This is a light spot with a light shielding plate 17.
This prevents malfunction by suppressing minute changes in the integral output (2) due to disturbances etc. when a is not applied. Integrate the output ■ with resistor R13 and capacitor C5,
The output amplified by the inverting amplifier A6 is @. The output of the inverting amplifier A6 is connected to the non-inverting input of the converter CP2, and the inverting input of the converter CP2 is connected to the G
It is at the nd level. Assuming that the offset voltage of the non-inverting input and the inverting input is V, the output is inverted when the non-inverting input exceeds the Gnd level by V, and its waveform is shown by ■. The output of the above-mentioned comparator CP2 and the output of the positive slope detection circuit PSD described later are input to the OR circuit OR, and when the output of the comparator CP2 is inverted, the OR circuit OR
The next stage flip-flop FF is set via the FF, the output 0 is inverted, and the transistor Tr2 is turned off. Therefore, the electromagnet Mg for the distance is cut off. That is, as the light shielding plate 17a scans the light receiving element 16, the integrated output dips as shown in ■, and at its peak point, the electromagnet M
g is turned off. The position of the scanning plate 17 at the time when the electromagnet Mg is turned off corresponds to the distance to the subject. Fourth
The control lever 21 in the figure has started rotating clockwise following the movement of the scanning plate l7. When the electromagnet Mg (23) is turned off, the hook of the iron piece 24 is moved to the control lever 2.
1 and stops the rotation of the control lever 21. By further pushing down the release lever 11, the shutter front running member 28, which has been unlocked by the locking lever 26, travels, first rotating the step cam 30 counterclockwise by a mechanism not shown. The rotation angle of the step cam is controlled by the step cam stopper part 2lb of the control lever 2l, and therefore the amount of extension of the objective lens is automatically determined.

After this, the shutter opens and closes. As the objective lens extends, the contact piece 33 also rotates, and a resistance value corresponding to the distance to the subject is selected and used as information for flashmatic or out-of-linkage warning. The switch S2 is a switch that is turned on when the scanning plate finishes scanning from a short distance to a long distance, and is used to generate a timing signal for an out-of-coupling warning, which will be described later, and as an off signal for the infrared light emitting diode IRED. The switch S3 is turned on by the operation of the shutter advance member 28, and is used as a trigger signal for the timer circuit TME. The purpose of the timer circuit TMH is to control the release lever.
Even if you press 11 quickly, the I
This is to keep the ED on, in this case switch S2
is no longer needed to turn off IRED.

It is also possible to turn off the IRED by turning off the electromagnet Mg.

Next, FIG. 6 and the warning circuit will be explained. 6th
In the figure, the same numbers as in FIG. 3 indicate members having the same functions.

In this embodiment, the light receiving element 16 has a dead zone 16a at its center, and is mounted on a scanning plate 17. By scanning the scanning plate 17, the third
Since the photoelectric output changes appear in exactly the same way as in the embodiment shown in the figure, it can be controlled by the circuit shown in FIG. Also, the lever 33 that always works in the direction of returning the release lever 11 is supported by the spring 3.
4, and when you release your finger from the release lever 11, the release lever 11 and the scanning plate 17 always return to their original states. In this mechanism, the scanning plate 17 is connected to the release lever 1.
1 is pressed down, the electromagnet 23 is turned off at the peak of the dip in the integral waveform, as in the previous embodiment, and the phase of the control lever 21 is determined. Further, the integral output shown in FIG. 1 is input to the non-inverting input of the comparator CP3 in FIG. 4, and the partial pressures of the bleeders R19 and R20 are input to the inverting input. Further, the output of the converter, the output of the flip-flop FF, and the inverted signal of the switch S2 are input to the AND gate AND1. That is, when the scanning plate 17 finishes traveling and the switch S2 is turned on, the off signal of the electromagnet 23 has not yet been obtained.
If the first integral output is sufficiently high, the AND gate AND1 is opened, and the next AND circuit AND2 operates the drive circuits Tr3 and Tr4 together with the oscillator OSC output. The flashing of the LED or the intermittent sound of the electronic buzzer B warns that the distance measuring device is not working properly or that the distance is extremely close. The photographer can then take his finger off the release lever 11 and redo the distance measurement. Here, the iron piece lever 24 of the electromagnet 23 is reset by a known method (not shown).

Next, the positive slope detection circuit will be explained with reference to FIG.

As shown in FIG. 7(a), the light receiving element 16 and the light shielding plate 17
Assume that the a1 light spot 35 is slightly deviated from the ideal state. This is a problem that may occur due to installation errors during production. As shown in (c) of the same figure, the scanning plate 17
When (SCP) runs, the integral output does not dip and becomes a monotonically increasing signal. Even in this case, as an example of a circuit for turning off the electromagnet Mg, a circuit as shown in FIG. 3(b) is formed. A capacitor C7, a charging resistor S25, and a switching transistor Tr6 are configured to be activated by the output of the comparator CP4 to the non-inverting input of the comparator CP4, and the first integral output is input to the inverting input of the comparator CP4. do. This circuit is capable of sending an activation signal to the next-stage OR gate OR to turn off the electromagnet 23 when the first integral output begins to increase. Since the dip peak detection signal is also input to the OR circuit OR, the OR gate OR is normally activated at the earlier timing of the output of the comparator CP2 or the output of the positive slope detection circuit PSD in FIG. It opens and the flip-flop FF operates.

FIG. 8 shows another embodiment of the jl distance electromagnet Mg control circuit.

As shown in FIG. 3(c), the scanning plate sc. If the intensity of the reflected light from the subject fluctuates as shown in ■ for some reason before p scans, in the conventional method, the electromagnet Mg turns off at point a, resulting in a malfunction, but (C) As shown in the Mg waveform of
) 1 distance is possible. In the same figure (a), the electromagnet 23
The iron piece 24A is of a sliding type, and the locking portion 17d prevents the lock lever 24B from operating until the scanning plate 17 starts traveling. Therefore, after the scanning plate 17 starts traveling, the ratchet of the control lever 21 is locked by the locking lever 24.
It can be stopped by B. The entrance route is in the same figure (b)
This is achieved by inserting a one-shot multi-by-break OST at the next stage of the OR circuit OR, as shown in FIG.

The bright period when the electromagnet 23 is off is determined by the values of the capacitor C8 and the resistor R27.

Note that the distance display can be easily implemented by providing a display member corresponding to the rotation angle of the control lever 21. In principle, part 2 lb of the step cam stopper should be made visible from inside the finder.

Furthermore, if the scanning plate 17 is configured to stop running when the electromagnet 23 is turned off, the display member can also be provided by providing a member that interlocks with the scanning plate 17.

[Effects] According to the present invention, the attenuation output of the photoelectric conversion element can be adjusted appropriately in a light-shielding plate scanning type light projection type/1111 distance measuring device (including a light projection type distance measuring device in which a dead zone is provided in the light receiving element). Because it can detect accurately, it is possible to accurately determine the distance to the subject. In addition to the peak detection circuit that detects the peak of the integral signal, a level change detection circuit that detects level changes of the integral signal is provided, and when the integral signal does not have a peak, the signal detected by the level change detection circuit is used. Therefore, it is possible to obtain an accurate range even for irregular photoelectric conversion outputs.

[Brief explanation of drawings]

Fig. 1 is a diagram for explaining the principle of a light-shielding plate scanning type light projection type distance measuring device, and Fig. 2 is a photoelectric output waveform diagram of the same distance measuring device.
FIG. 3 shows an example of a mechanism constituting the distance measuring device, and FIG. 4 shows an example of a control circuit for the distance measuring device. Fig. 5 is a diagram showing the output waveforms of each part to explain the operation of the control circuit in Fig. 4, Fig. 6 is an example of another side of the range finder, and Fig. 7 is an example of the positive tilt detection circuit. FIG. 8 is a diagram illustrating another side of the distance measuring device, an example of a drive circuit for a ranging electromagnet, and a diagram illustrating its operation. AI, A2-A6...Amplifier CP1-CP3...Voltage converter SH...
・・・・Sample hold circuit PSD・・・・Positive slope detection circuit OSC・・・Oscillator PD・・・Photodetector IRED・・・Infrared light emitting diode TME・・・・
... Timer circuit DRV ... IRED drive circuit B ... Buzzer 1 ... Light emitting element 6 ... Light receiving element 7 ... Light shielding Plate 17...Scanning plate 21...Control lever 23...Electromagnet 30...Step cam S1...Power switch 33...・・Touch piece 35・・・・・・Light spot or more

Claims (3)

[Claims] (1) A light projector that projects light emitted by a light emitting element onto a subject; a drive circuit that causes the light emitting element to emit light in a pulsed manner; and a light receiving element that photoelectrically converts the reflected light of the light emitting element that is reflected by the subject. , attenuation means that moves in correlation with the distance to the subject and attenuates the photoelectric conversion output of the light receiving element when it intersects the optical path of the reflected light; and an integrated signal that integrates the signal photoelectrically converted by the light receiving element. a peak detection circuit that detects a peak of the integrated signal that changes with attenuation of the photoelectric conversion output; a level change detection circuit that detects a level change of the integrated signal; When a peak occurs, the distance to the subject is selected based on the position of the attenuation means when the peak is detected by the peak detection circuit, and when a level change is detected by the level change detection circuit when the integrated signal does not produce a peak. and distance selection means for selecting a distance to a subject based on the position of the attenuation means. (2) The projecting distance measuring device according to claim 1, wherein the attenuation means is constituted by a light shielding member that moves in front of the light receiving element. (3) The projecting distance measuring device according to claim 1, wherein the attenuation means is constituted by a dead zone provided in the light receiving element.