JPH0588404B2 - - Google Patents

Description

[Detailed description of the invention]

[0001]

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

[0002]

2. Description of the Related Art Conventionally, various optical projection type distance measuring devices that utilize the principle of triangulation have been proposed. Among these, a distance measuring device (Japanese Patent Application No. 124268/1989) already proposed by the applicant has a light-shielding plate that scans the surface of a single light-receiving element, thereby changing the photoelectric output of the light-receiving element. This is a system that measures distance by detecting the presence of objects. Hereinafter, this will be referred to as a light shielding plate scanning type distance measuring device.

【0003】

[Problems to be Solved by the Invention] In the light-shielding plate scanning type distance measuring device, there is a problem in that the light-receiving element and the light-shielding plate must be constructed separately, making the structure complicated.

[0004] An object of the present invention is to provide a projection type distance measuring device that can measure distances with a simple configuration.

[0005]

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

[0006] FIG. 1 is a diagram showing the principle of a light-shielding plate scanning type light projection type distance measuring device.

[0007] 1 is a light emitting element, 2 is a light projection lens, and 3 is a light projection axis. 4 is the reflected optical axis from the subject 8, 5
is a light emitting lens, and 6 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 distance measuring device described above.

[0008] To explain the operation, the light emitting element 1
The light emitted from the lens is condensed by the light projecting lens, becomes a light beam, and hits the subject 8, and the reflected light is reflected by the light receiving lens 5.
As a result, an image is formed on one point on the light receiving element 6 as a light spot. On the other hand, the light shielding plate 7 is scanned from the right in the figure with a certain correlation to 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 further away the subject is, the more the position of the light spot formed on the light receiving element 6 in FIG. 1 shifts to the left.

[0009] 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.

[0010] In the figure, 11 is a release lever, which is urged upward by a spring 12. A scanning plate 17 includes a light shielding plate 17a that scans the surface of the light receiving element 16. The scanning plate 17 is urged rightward by a spring 18 and 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. Reference numeral 21 denotes a control lever, which is given the habit of rotating clockwise by a spring, and is rotated by engaging with a pin 17c on the scanning plate 17. 23 is an electromagnet, 24 is an iron piece, and spring 2 is
5 acts in the direction of separation from the electromagnet. 2
6 is a locking lever for the shutter forward travel lever 28;
Reference numeral 9 denotes a spring that biases the shutter forward travel lever 28 in the right direction. Reference numeral 30 denotes a step 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 denotes a contact piece, which selects a resistor 36 according to the extension of the objective lens, and is used as distance information for a flash automatic or the like.

[0011] FIG. 4 is an embodiment of a control circuit in a distance measuring device of the present invention.

[0012] In the same figure, PD is a light receiving element,
The first-stage amplifier A1 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, C3 are integrating resistors and capacitors, 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 R11. CP1 is a comparator, an integral output is input to the non-inverting input, a capacitor C6 and a resistor R17 are connected to the inverting input, and a diode D3 is connected between the inputs to form a clamp circuit. comparator
The output of CP1 is connected to transistor Tr1. R13 and C5 are a resistor and a capacitor for the second integrating circuit. A6 is an inverting amplifier, the output of which is connected to the non-inverting input of the coparator CP2. PSD is a positive slope detection circuit, and its output and the output of comparator CP2 enter an OR circuit OR, which is further connected to a flip-flop FF. Tr2 is a transistor for controlling the ranging 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 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 that is triggered by the shutter release switch S3.
Controls the operation of the IRED drive circuit DRV. IRED is an infrared light emitting diode for light emission, and is a transistor
Pulse driven by Tr5. S1 is a power switch.

[0013] Next, the operations in FIGS. 3 and 4 will be described. Note that FIG. 5 shows the operating waveforms of each part of the circuit.

[0014] When the release lever 11 is pushed down,
The power switch S1 is turned on, 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 drive circuit DRV. When the release lever 11 is further pushed down, the locking member 13 disengages the scanning plate 17, 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 element 17a scans the light receiving element 16 and starts shielding the light spot on the light receiving element, the amplitude of the waveform of the output A of the AC amplifier A2 changes as shown in FIG. When this AC signal is detected by diode D1 and integrated by R6 and C3, the waveform amplified by amplifier A4 becomes a dip waveform as shown in B. Furthermore, the waveform passed through the sample-and-hold circuit SH becomes step-like as shown in D. When the waveforms B and D are input to the operational amplifier A5, an output E is obtained. Here the clamp circuit
The circuit is composed of CP1, D3, C6, and R17, and the inverted input waveform of CP1 has a fall delay with respect to the dip waveform of B, as shown by C. Then, when B>C, the transistor Tr1 is turned on and clamps the output of the operational amplifier A5. This prevents malfunctions by suppressing minute changes in the integral output B due to external disturbances when the light shielding plate 17a is not in contact with the optical pot. Output E is integrated by resistor R13 and capacitor C5, and output G is amplified by inverting amplifier A6. The output of the inverting amplifier A6 is connected to the non-inverting input of the comparator CP2, and
The inverting input of this comparator CP2 is at Gnd level. If the offset voltage of the non-inverting input and the inverting input is v, then when the non-inverting input exceeds the Gnd level by v, the output is inverted and its waveform becomes H.
Indicated by The above comparator CP2 is used for the OR circuit OR.
The output of the comparator CP2 and the output of the positive slope detection circuit PSD described later are input, and when the output of the comparator CP2 is inverted, the next stage flip-flop FF is set via the OR circuit OR, and the output Q bar is inverted and the transistor Tr2 is activated. It turns off. Therefore, the ranging electromagnet Mg is cut off. That is, as the light-shielding plate 17a scans the light-receiving element 16, the integrated output dips as indicated by B, 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. 3 has started rotating clockwise following the movement of the scanning plate 17. When the electromagnet Mg23 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 stepped cam is controlled by the stepped cam stopper 21b of the control lever 21, and therefore the amount of extension of the objective lens is automatically set in accordance with the distance to the subject. After this, the shutter opens and closes. As the objective lens moves out, the contact piece 33 also rotates, and a resistance value corresponding to the object distance is selected and used as information for a flash automatic or out-of-link warning. 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 create a timing signal for the out-of-link warning described later, and as an off signal for the infrared light emitting diode IRED. Switch S
3 is turned on by the operation of the shutter forward running member 28, and is used as a trigger signal for the timer circuit TME. The purpose of the timer circuit TME is that even if the release lever 11 is pressed quickly, the timer circuit TME will not operate until the distance measurement operation is completed.
This is to keep IRED on; in this case, switch S2 is no longer necessary to turn off IRED. It is also possible to turn off IRED by turning off electromagnet Mg.

[0015] Next, FIG. 6 and the warning circuit will be explained. In FIG. 6, the same reference numerals as in FIG. 3 indicate members having the same functions.

[0016] 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 17 scans, a change in photoelectric output appears in exactly the same manner as in the embodiment shown in FIG. 3, and therefore it can be controlled by the circuit shown in FIG. In addition, the lever 33 that always works in the direction of returning the release lever 11 is supported by a spring 34.
The release lever 11 and the scanning plate 17 always return to their original states when the release lever 11 is released. In this mechanism, the scanning plate 17 follows the depression of the release lever 11 and travels, but the electromagnet 23 is turned off at the dip peak of the integral waveform as in the previous embodiment, and the control lever 11 is pressed down.
Determine the phase of 1. Also, the comparator in Figure 4
The integral output of FIG. 1 is input to the non-inverting input of CP3, and the partial pressures of the bleeders R19 and R20 are input to the inverting input. Also, and gate AND
1, the above-mentioned comparator output, flip-flop FF output, and the inverted signal of switch S2 are input. That is, when the scanning plate 17 finishes traveling and the switch S2 is turned on, if the electromagnet 23 has not yet received an off signal and the first integral output is sufficiently high, the AND gate AND1
opens, and the next AND circuit AND2 turns on the oscillator OSC.
Along with the output, drive circuits Tr3 and Tr4 are activated. A flashing LED or an intermittent sound from the electronic buzzer B warns you that the distance measuring device is not working properly or that the distance is extremely close. Therefore,
The photographer can take his finger off the release lever 11 and redo the distance measurement. Here, electromagnet 2
The iron piece lever 24 of No. 3 is reset by a known method (not shown).

[0017] Next, the positive slope detection circuit will be explained with reference to FIG.

[0018] As shown in FIG. 7a, the light receiving element 16,
Assume that the light shielding plate 17a and the light spot 35 are slightly deviated from the ideal state. This is a problem that may occur due to installation errors during production. B in c of the same figure
As shown in FIG. 2, when the scanning plate 17SCP moves, 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. 2B is formed. The non-inverting input of comparator CP4 includes a capacitor C7, a charging resistor S25, and a switching transistor.
Tr6 is configured to be activated by the output of the comparator CP4, and the first integral output is input to the inverting input of the comparator CP4. 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 normally opens at the earlier timing of the output of the comparator CP2 or the output of the positive slope detection circuit PSD in Figure 4. The flip-flop FF operates.

[0019] FIG. 8 shows another embodiment of the ranging electromagnet Mg control circuit.

[0020] As shown in Figure c, the scanning plates SC, P
If the intensity of the reflected light from the subject fluctuates as shown in B for some reason before scanning, in the conventional method, the electromagnet Mg would turn off at point a, resulting in a malfunction, but the Mg waveform at c Correct distance measurement becomes possible by immediately re-energizing the sensor and turning it off again at the peak of the normal dip signal, that is, at point b. In the figure a, the iron piece 24 of the electromagnet 23
A uses a sliding type, and a 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. As shown in Figure b, the circuit is constructed by inserting a one-shot multivibrator OST at the next stage of the OR circuit OR. The period during which the electromagnet 23 is off is determined by the values of the capacitor C8 and the resistor R27.

[0021] 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, the stopper portion 21b of the stepped cam may be made visible from inside the viewfinder.

[0022] In addition, the movement of the scanning plate 17 is controlled by the electromagnet 23.
If the display member is stopped when the scanning plate 17 is turned off, the display member can also be provided by providing a member that interlocks with the scanning plate 17.

[0023]

[Effects of the Invention] According to the present invention, since a light-receiving element in which a dead zone is provided in a part is employed, the configuration of the distance measuring device is simplified.

[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.

FIG. 2 is a photoelectric output waveform diagram in the distance measuring device.

FIG. 3 is an example of a mechanism that constitutes a distance measuring device.

FIG. 4 is an example of a control circuit of a distance measuring device.

5 is a diagram showing output waveforms of various parts for explaining the operation of the control circuit shown in FIG. 4; FIG.

FIG. 6 is an example of another mechanism of the distance measuring device.

FIG. 7 is an example of a positive slope detection circuit and an explanatory diagram of its operation.

FIG. 8 is an example of another mechanism of the distance measuring device, an example of a drive circuit for a distance measuring electromagnet, and an explanatory diagram of its operation.

[Explanation of symbols]

A1, A2 ~ A6...Amplifier CP1~CP3……Voltage comparator 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...stage cam S1...Power switch 33... contact piece 35...Light spot.

Claims (1)

[Claims] 1. Light projecting means for projecting light emitted by a light emitting element onto a target object; a driving circuit that causes the light emitting element to emit light in a pulsed manner; a light-receiving element that generates a photoelectric conversion signal by photoelectrically converting the reflected light of the light emitting element reflected by an object, and has a dead zone in a part thereof; an integrating circuit that generates an integral signal that integrates the photoelectric conversion signal; a delay circuit that generates a delayed signal that is a delayed signal; a differential circuit that generates a difference value between the integral signal and the delayed signal; and a differential circuit that generates a differential value between the integral signal and the delayed signal; a peak detection circuit that detects based on the value, and distance information corresponding to the distance to the object based on the position of the light receiving element in the movement process when the peak detection circuit detects a change in the photoelectric conversion signal. A projection type distance measuring device comprising a distance information setting means for setting.