JPH03102210A - Projecting-type distance measuring apparatus - Google Patents

Abstract

PURPOSE:To prevent an erroneous operation by providing a prohibiting circuit which prohibits generation of a peak detecting signal when the variation of an integrated signal is not larger than a predetermined value. CONSTITUTION:The waveform of an output A of an alternating current amplifier A2 is changed in amplitude. An alternating signal of this amplifier A2 is detected by a diode D1, integrated by a resistance R6 and a capacitor C3, so that an output B of an amplifier A4 represents a dip waveform. An output D through a sample-and-hold circuit SH becomes a staincase waveform. The outputs B, D are input to an operational amplifier A5 to obtain an output E. A clamp circuit is comprised of a comparator CP1, a diode D3, a capacitor C6 and a resistance 17, so that an output C of the input waveform of the CP1 is delayed to fall to the dip waveform of the output B. When the output B>=output C, a transistor Tr1 is turned ON to clamp the output of the amplifier A5. Therefore, the output B is restricted to change minutely by an external disturbance or the like when a light shield is not in touch with a light spot, thereby preventing an erroneous operation.

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] Conventionally, various optical projection type distance measuring devices that utilize the principle of triangulation 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. Especially the circuit against malfunction.”
- No measures were taken.

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 takes measures against malfunctions.

[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 focused by the light emitting lens and becomes a light beam that hits the limb photographing object 8, 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, 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 Figure 2, where the point J2p has a negative peak.
is the distance to the subject. As the subject gets farther away, the position of the light spot formed on the light receiving element 6 in FIG. 1 shifts 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 pin 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.

FIG. 4 shows an 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 amplifier 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 that performs 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 converter CPI is connected to transistor Trl. 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 controlling the #j distance electromagnet Mg. CP3 is a comparator whose non-inverting input receives the first integral output, and its inverting input is connected to a bleeder consisting of resistors R19 and R20. AND1 and AND2 are AND gates, INV is an inverter, and 82 is a switch that is turned on when the scanning plate is close to the point where scanning is completed. Tr3 is warning L
The ED control transistor Tr4 is an electronic buzzer B control transistor. OSC is an oscillator. TME is a timer circuit, and the shutter release switch S3
The trigger is activated to control the operation of the IRED drive circuit DRV. IRED is an infrared light emitting diode for light projection, and is pulse driven by a transistor Tr5. S1 is a 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 governors 19 and 20 cause the scanning plate 17 to start scanning at a constant speed in the direction of the arrow in the figure. 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 manually applied to operational amplifier A5, output ■ is obtained. Here, the clamp circuit is CPI, 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 ■≧■, 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 O. The output of the inverting amplifier A6 is connected to the non-inverting input of the comparator CP2, and the inverting input of the comparator 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 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 71111 distance electromagnet Mg is cut off. That is, as the light-shielding plate 17a scans the light-receiving element 16, the integrated output dips as shown by ■, and at its peak point, the electromagnet Mg 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. The control lever 21 in FIG. 4 has started rotating clockwise following the movement of the scanning plate 17. The above electromagnet Mg (
23) is turned off, the hook of the iron piece 24 enters the ratchet portion of the control lever 21, and the rotation of the control lever 21 is stopped. 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 21, 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 object distance is selected and used as information for flashmatic or out-of-link 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. Switch S3 is the shutter front running member 28
It turns on when activated and is used as a trigger signal for the timer circuit THE. The purpose of the timer circuit TMH is to keep the IRED on until the Atj distance operation is completed even if the release lever 11 is pressed quickly.In this case, the switch S2 is not necessary to turn off the IRED. It disappears. 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. As the scanning plate 11 scans, a change in photoelectric output appears in exactly the same way as in the embodiment shown in Figure 3 of J.2.
This can be controlled by the circuit shown in FIG. Further, a lever 33 that always works in the direction of returning the release lever 11 is arranged together with a spring 34, and when the finger is released 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.
11, the electromagnet 23 is turned off at the peak of the dip in the integral waveform, and the phase of the control lever 21 is determined, as in the previous embodiment. In addition, the integral output of FIG. 1 is input to the non-inverting input of comparator CP3 of FIG. 4, and the bleeder R19, R20 is input to the inverting input
The partial pressure is done manually. Also, and gate AND1
The output of the converter, the output of the flip-flop FF, and the inverted signal of the switch S2 are input to the circuit. That is, when the scanning plate 17 finishes traveling and the switch S2 is turned on, if the off signal of the electromagnet 23 has not yet been obtained and the first integral output is sufficiently high, this AND game }AND1 opens, The next AND circuit AND2 activates the drive circuits Tr3 and Tr4 with the oscillation "10SC output.The flashing of the LED or the intermittent sound of the electronic buzzer B indicates that the /lJlj distance 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 try again to measure the distance.Here, the iron piece lever 2 of the electromagnet 23
4 is set to i4 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 connected to the non-inverting input of the comparator CP4 so as to be activated by the output of the comparator CP4, and the first integral output is connected to the inverting input of the comparator CP4 manually. 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 ranging 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
However, correct distance measurement is possible by immediately re-exciting as shown in the Mg waveform in (C) and turning off again at the peak of the normal dip signal, that is, point b. In FIG. 5A, the iron piece 24A of the electromagnet 23 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 can be stopped by the lock lever 24B. The circuit is constructed by inserting a one-shot multivibrator OST at the next stage of the OR circuit OR, as shown in FIG. 2(b). During the period when the electromagnet 23 is off, the capacitor C8 and the resistor R2
It is determined by the value of 7.

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 of the step cam stopper 2L
b can be seen from within the viewfinder.

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, a light-shielding plate scanning type light projection type distance measuring device (including a light projecting type distance measuring device in which a dead zone is provided in the light receiving element) is provided.
Since the attenuated output of the photoelectric conversion element can be detected accurately, the distance to the subject can be accurately determined. Furthermore, since a prohibition circuit is provided that prohibits generation of the peak detection signal when the amount of variation in the integral signal is below a certain level, an effective countermeasure against malfunction can be taken.

[Brief explanation of drawings]

Fig. 1 is a diagram for explaining the principle of the light shielding plate scanning type light projecting type all range device, Fig. 2 is a photoelectric output waveform diagram in the same all range device, and Fig. 3 is a diagram of the mechanism constituting the M1 range device. As an example, FIG. 4 shows an example of a control circuit of a 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 mechanism of the distance measuring device, and Fig. 7 is an example of the positive inclination detection circuit and its FIG. 8 is an example of another mechanism of the distance measuring device, an example of a drive circuit for the aPJ distance electromagnet, and a diagram illustrating its operation. A1, A2-A6...Amplifier CPI-CP3...Voltage converter SR...
・・・・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 l ... Light emitting element 6 ... Light receiving element 7 ... Light shielding plate 17... Scanning plate 1... Control lever 3... Electromagnet 0... Stage cam 1... Power switch 3...・Touch piece 5... More than a light spot

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 the peak of the integral signal that changes with attenuation of the photoelectric conversion output and generates a peak detection signal; and a position of the attenuation means when the peak detection signal is generated. A projection type distance measuring device comprising a distance selection means for selecting a distance to a subject based on the above, and a prohibition circuit for prohibiting generation of the peak detection signal when the amount of variation in the integral signal is less than a certain amount. (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.