JPH0342607B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a distance measuring device used in a camera, etc., which projects light emitted from a light emitting element toward a distance measuring object, and transmits the reflected light between two adjacently arranged distance measuring devices. This invention relates to an improvement of a triangular distance measuring device that receives light with a light receiving element. Conventionally, as a distance measuring device using the method described above,
This has been proposed in Japanese Patent Publication No. 54-39731, Japanese Patent Application Laid-Open No. 57-104809, etc. In general, when measuring distance by receiving light reflected from a distance measurement target by a light emitting element using a light receiving element,
The intensity of the reflected light varies by a factor of 1,000 or more depending on the reflectance of the object to be measured, the distance, etc. Therefore, the amplifier circuit that amplifies the output of the light receiving element needs to have a dynamic range of 60 dB or more. Possible ways to widen the dynamic range include logarithmic compression of the light receiving element output and automatic gain adjustment of the amplifier circuit, but in the former case, when the amount of light received is large and the output difference between the light receiving elements is small, the S/N In the latter case, a feedback system is required, which increases unstable factors such as oscillation. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to gradually increase the output of a light-receiving element from an apparently zero or minute value by a simple means without having the drawbacks of the conventional example, and to set the comparison circuit to a certain setting that is easy to distinguish. The object of the present invention is to provide a distance measuring device that determines the distance measuring state when a value is reached, and sets the photographing lens at a predetermined position. Embodiments of the present invention will be described below based on the drawings. First, in Figure 1, 1 is a clock pulse generation circuit (oscillation frequency o = 16KHz, hereinafter referred to as OSC).
2 is a time forming circuit (time t=
25ms), 3 is an AND gate, 4 is a transistor,
Reference numeral 5 denotes an infrared light emitting diode (hereinafter referred to as IRD) as a light emitting element that projects a spot light to the distance measurement target, and 6 and 7 respectively indicate a base line so as to receive the light projected from the IRD 5 and reflected by the distance measurement target. Silicon photodiodes (hereinafter referred to as SPD) as light receiving elements arranged adjacent to each other in the longitudinal direction, 8
and 9 are AC amplifier circuits, respectively, 10 and 11 are AC amplifier circuits equipped with gain (amplification factor) adjustment input terminals 10a and 11a, respectively, and 12 and 13 are band filter circuits (center frequency o = 16 KHz, hereinafter referred to as BPF). ), 14 and 15 are detection circuits, 16 and 17 are smoothing circuits, 18 and 19 respectively.
are respectively DC amplifier circuits, 20 is an inverter, 21 is a transistor, 22 is a constant current circuit, 23 is a capacitor, 24 is a current amplifier circuit, 25 is a comparator circuit, 26 and 27 are inverting input terminals (-) of the comparator circuit 25 28 is an AND gate, 29 is an analog switch, 30 is an inverter, 31 is a capacitor, 32 is a current amplification circuit, and 33 is a comparator circuit (the comparator circuit is commonly referred to as
CMP), 34 and 35 are constant current circuits that apply a displacement voltage corresponding to the amount of movement from one extreme position to the other extreme position in the movable range of the photographing lens to the non-inverting input terminal (+) of the CMP 33; A potentiometer, 36 is an RS type flip-flop circuit (hereinafter referred to as FF), 37 is an AND gate, 38 is a transistor, and 30 is an electromagnet for stopping the movement of the operating member (lens settling) of the photographic lens. Next, in FIG. 2, 40 is a lens setting ring, which is arranged rotatably around the optical axis.
In addition, the spring 41 imparts dextrorotation, and the right rotation displaces the photographing lens from an infinity position to a close distance position, and also forms a stepped portion 40a and a ratchet tooth 40b. .
Reference numeral 42 denotes a lens-driving release electromagnet, which is composed of an iron core 42a, a coil 42b, and a permanent magnet 42c. Reference numeral 43 designates an iron piece lever for the release which is pivotally connected to the shaft 44 and given left-handed rotation by a spring 45, and includes a hook 43a that can be engaged with the stepped portion 40a of the lens setting ring 40 and an iron core of the electromagnet 42. An iron piece 43b opposite to 42a is formed. 46 is a pin, iron piece lever 43
The amount of left rotation is limited. Reference numeral 47 designates a locking iron piece lever pivotally mounted on a shaft 48 and given dextrorotation by a spring 49, and a hook 47a capable of engaging with the ratchet teeth 40b of the lens setting ring 40;
Electromagnet 39, which is the same as in FIG.
An iron piece 47b is formed opposite to the iron piece 47b. Note that the potentiometer 35 in FIG.
As shown in FIG. 2, the lens setting ring 40
The brush 35a is supported by a resistor 35c and a conductor 35d formed on a substrate 35b. Therefore, the operations shown in FIGS. 1 and 2 will be explained together with FIG. 3. When a power switch (not shown) is closed at the start of the operation, power is supplied to each part of the circuit and the reset of the FF 36 is released. Then, OSC1 operates and a clock pulse with a period of 62.5 μs is generated, and the time forming circuit 2
The output is inverted to the "H" level for a time of t=25ms. Therefore, the clock pulse passes through the AND gate 3 for that period of time, and the transistor 4 repeats conduction and cutoff in response to the clock pulse, and as a result, the IRD 5 lights up in pulses. By lighting up the IRD 5, the projected light is reflected from the distance measurement target and is received by the SPDs 6 and 7.
As a result, the light reception outputs at points a and a' are generated superimposed on the direct current component due to natural light, as shown in ◯b. Further, the outputs at points b and b' after the AC amplifier circuits 8 and 9 are amplified and appear as shown in the circle. On the other hand, while the output of the time forming circuit 2 is inverted to the "H" level for 25 ms, the inverter 20
Since the output of is inverted to the "L" level and the transistor 21 is cut off, the capacitor 23 is charged with a constant current by the constant current circuit 22, and the constant current is transferred to I,
Assuming that the capacitance of the capacitor 23 is C, the voltage V at the output terminal c of the current amplifier circuit 24 increases as shown by ◯ C according to the relational expression: V=(1/C)I·t. That is, in the AC amplifier circuits 10 and 11, the potentials of the gain adjustment input terminals 10a and 11a, respectively, gradually rise from a low level, and the amplification factor is swept from zero or from a low amplification factor to a high amplification factor, and d and d' The output at the point looks like the waveform shown by ○. Also, the outputs at points e and e' after BPF12 and 13 are the center frequency o and the oscillation frequency o of OSC1.
and are set to the same value, as shown in ○ho,
It appears as if the waveform of ○D has been amplified. Furthermore, the output waveforms at points f and f' after the detection circuits 14 and 15 are as follows:
The output voltages Vg and Vg' at points g and g' after passing through the smoothing circuits 16 and 17 and the DC amplifier circuits 18 and 19 gradually rise from the predetermined values, as shown in ○f. . As shown in Fig. 3, when the object to be measured is located at a short distance, the reflected light spot X is sufficiently wide at SPD6 and extremely narrow at SPD7, as shown at a1 and a2. Therefore, the output voltage Vg at point g is sufficiently higher than the output voltage Vg' at point g', and the potentials at points g and g' rise while maintaining this relationship. Also, at this stage, the AND gate 28 is closed and the output of the inverter 30 is at the "H" level, so the analog switch 29 is open and the capacitor 31 is charged by the output voltage Vg' at point g'. Go. Then, when the output voltage Vg at point g reaches the reference voltage Vr, the output of the CMP 25 is inverted to "H" level, and as a result, the AND gate to which the "L" level signal was applied for the previous time t 28 is opened and its output is inverted to the "H" level, and the FF 36 is set to invert and hold the output Q to the "L" level, and the output of the inverter 30 is inverted to the "L" level and the analog switch 29 is turned on. close it. Therefore, the output voltage at point g' when the output voltage Vg at point g reaches the reference voltage Vr is stored in the capacitor 31.
Vg' (V1) is stored. Moreover, the voltage V1 is
It is amplified by the current amplification circuit 32 and applied to the inverting input terminal (-) of the CMP 33 . Note that in the CMP 33, since the potentiometer 35 that applies an input voltage to the non-inverting input terminal (+) is located on the high potential side in the initial state, the initial output state is set at the "H" level. Therefore, since the AND gate 37 opens the gate and makes the transistor 38 conductive, the electromagnet 39 is energized and holds the iron piece lever 47 by attraction. Then, after the previous holding period t ends, the coil 42b of the electromagnet 42 is turned on by a circuit operation (not shown).
When pulsed in a direction to cancel the magnetic force of the permanent magnet 42c, the iron piece lever 43 is rotated to the left by the tension of the spring 45, and the hook 43a is removed from the stepped portion 40a of the lens setting ring 40. As a result, the ring 40 begins to rotate to the right due to the tension of the spring 41.
The photographing lens is displaced from the infinity position to the close distance position, and the brush 35a is slid on the resistor 35c and the conductor 35d, thereby displacing the potentiometer 35 from the high potential side to the low potential side. move it. Then, when the potential at the non-inverting input terminal (+) of the CMP 33 drops to the potential at the inverting input terminal (-), the output of the CMP 33 is inverted to the "L" level and the AND gate 37 is closed. the result,
Since the transistor 38 is cut off and the electromagnet 39 is demagnetized, the iron lever 47 rotates clockwise due to the tension of the spring 49, and the hook 47a engages with one of the ratchet teeth 40b, stopping the lens setting ring 40 from rotating clockwise. The photographing lens is fixed in a predetermined position. In addition, if the object to be measured is located at a slightly farther position, the voltage V1 corresponds to the above-mentioned storage voltage V1, and the voltage V1 is as shown in b1 and b2, for example.
Changes to 2. Furthermore, if the object to be measured is located further away, it will become as shown by the solid line at C1 and C2 (when the reflected light spot X is approximately equally divided between SPDs 6 and 7), and the above storage voltage V1
The voltage corresponding to V3 changes to voltage V3. Furthermore, if the object to be measured is located at a very far distance, the reflected light spot , the output voltage Vg does not reach the reference voltage Vr within the previous time t (this may also happen if the distance measurement target has a small reflectance),
The output of CMP25 remains at "L" level,
When the time t ends and the output of the time forming circuit 2 returns to the "L" level, the output of the AND gate 28 cannot be inverted to the "H" level.
Therefore, FF36 is not set and the output Q is "L".
This level is maintained, and the AND gate 37 is kept closed. As a result, the electromagnet 39 is not electromagnetized from the initial state and does not attract the iron piece lever 47, so the lens setting 4
0 rotates to the right and the first tooth of the ratchet tooth 40b opposes the hook 47a, the iron lever 47 immediately rotates to the right and the hook 47a moves to the right and the first tooth of the ratchet tooth 40b faces the hook 47a.
, the right rotation of the lens setting ring 40 is stopped, and the photographing lens is fixed at the infinity position. Next, another embodiment will be described with reference to FIGS. 4 and 5. Note that the same elements as in the previous embodiment are given the same reference numerals. 51, 52 are CMP, 53, 54 and 55 are constant current circuits, resistors and potentiometers, 56, 57
and 58 is a NAND gate (in addition, the above elements and
A window comparator circuit is constructed in such a manner that the output voltage of the current amplifying circuit 32 is input and the states of the NAND gates 57 and 58 are output. ) 59 is an AND gate, 60 is an OR gate, 61 is an inverter, 62 to 65 are transistors, and 66 is a motor. A lens setting ring 67 is rotatably arranged around the optical axis, and forms a partial gear 67a. A pinion 68 is fixed to the rotating shaft of a motor 66, which is the same as that shown in FIG. An intermediate gear 69 meshes with the pinion 68 and the partial gear 67a of the lens setting ring 67. Note that the potentiometer 55 in FIG.
As shown in FIG. 5, the lens setting ring 67
The brush 55a is supported by a resistor 55c and a conductor 55d formed on a substrate 55b. As mentioned above, the output voltage of the current amplification circuit 32 is
Apart from extreme distances, the distance is set to increase as the distance to be measured becomes near, medium, and far. Since it is a window comparator circuit, the output voltage (Vx) of the current amplifier circuit 32 is
Voltage (Vy) of non-inverting input terminal (+) of CMP51
If it is higher than , the output of CMP51 is "L" level and the output of CMP52 is "H" level, so the output of NAND gate 56 becomes "H" level, and the output of NAND gate 57 becomes "H" level.
The output of the NAND gate 58 becomes "L" level. On the other hand, if the output voltage Vx is lower than the voltage (Vz) of the inverting input terminal (-) of the CMP52, the CMP
Since the output of the CMP 51 is at the "H" level and the output of the CMP 52 is at the "L" level, the subsequent output states will have a reverse relationship to that described above. In any of the above cases, since there is a difference between the two inputs of the motor drive circuit, the motor 66 rotates in corresponding directions to drive the lens setting ring 67. Furthermore, when the output voltage Vx is placed in the relationship Vy>Vx>Vz, the outputs of the CMPs 51 and 52 are both at the "H" level and the output of the NAND gate 56 is at the "L" level. 57
and 58 are both at the "L" level, and since both inputs of the motor drive circuit are at the same potential at this time, the motor 66 does not rotate. That is, by operating the potentiometer 55 in conjunction with the movement of the lens setting ring 67 driven by the rotation of the motor 66, the voltages Vy and Vz are changed with respect to the output voltage Vx at that time, and Vy
The relative position of >Vx>Vz is detected and the photographing lens is fixed at a predetermined position. Furthermore, as mentioned above, FF36 is not set,
When the output Q remains at the "L" level, the output of the AND gate 59 is at the "L" level, and the OR gate 60
The output of Vx is held at “H” level, and the output voltage Vx
is the same as when Note that at this time, the operation to detect the state of Vy>Vx>Vz becomes irrelevant, and the current that drives the photographic lens toward the far distance side continues to flow through the motor 66, so a limiter is provided. It is preferable to leave it there. Next, another embodiment will be described with reference to FIG. Note that the same elements as in the previous embodiment are given the same reference numerals. 71 is, for example, a 4-bit A/D converter circuit, 72 to 75 are AND gates, and 76 is, for example, a 4-bit A/D converter circuit.
BIT magnitude comparator circuit, 77
is a motor drive circuit, 78 is a motor that drives lens setting by its rotation, and 79 is a motor 7.
For example, it is a 4-bit encoder that digitizes the amount of rotation of 8. The analog amount of the output voltage of the current amplification circuit 32 is
The A/D converter circuit 1 uses four output terminals to convert "L", "L", "L", "L" to "H", "H".
”,
It is encoded as one of the 16 levels of digital quantity from "H" to "H", and the 16 levels are, for example, divided into 16 from the extremely far distance position to the close distance position. Therefore, the output of the A/D converter circuit 71 is
The signals are input to a magnitude comparator circuit 76 through AND gates 72-75. The lens setting is driven by rotating the motor 78 by the motor drive circuit 77. As a result, the photographing lens is displaced from the infinity position to the close distance position. When the output of an encoder 79 that converts the amount of rotation of the motor 78 into a digital amount matches the input of the comparator circuit 76, the motor 78 is stopped and the photographing lens is fixed at a predetermined position. Also, as mentioned above, FF36 is not set,
When the output Q remains at the "L" level, the outputs of the AND gates 72 to 75 are both held at the "L" level, which is the same as the extreme distance state described above, so the photographing lens is at the infinity position. It is fixed at In each of the embodiments, if the FF 36 is not set and a long-distance state is set, an alarm can also be issued at the same time. As described above, the present invention achieves stable operation with a simple configuration that sweeps the amplification factor of the amplifier circuit from a low amplification factor to a high amplification factor without performing logarithmic compression of the light receiving element output or automatic gain adjustment of the amplification circuit. It is possible to determine the distance measurement state and set the photographing lens at a predetermined position.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram showing an example of the driving mechanism of the photographing lens corresponding to FIG. 1, and FIG. An explanatory diagram showing the relationship between the state and the output voltage, Fig. 4 is a partial circuit diagram showing another embodiment of the present invention, and Fig. 5 shows an example of the driving mechanism of the photographing lens corresponding to Fig. 4. The explanatory diagram, FIG. 6, is a partial circuit diagram showing still another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Clock pulse generation circuit, 2... Time forming circuit, 5... Infrared light emitting diode, 6 and 7... Silicon photodiode, 8, 9, 10 and 11... AC amplifier circuit, 10a and 11a... Gain adjustment input terminal, 12 and 13... Band filter circuit, 14 and 15...detection circuit, 16 and 17...smoothing circuit, 1
8 and 19... DC amplifier circuit, 24 and 32... Current amplifier circuit, 35 and 55... Potentiometer, 3
9...Electromagnet, X and X'...Reflected light spot, 40
and 67...lens settling, 66 and 78...
Motor, 71... A/D converter circuit, 76... Magnitude comparator circuit, 77... Motor drive circuit, 79... Encoder.

Claims (1)

[Scope of Claims] 1. In a triangular distance measuring device in which light emitted from a light emitting element is projected toward a distance measuring object, and the reflected light is received by two adjacently arranged light receiving elements, The amplification factor of the amplifier circuit that amplifies the output of the photodetector is swept from a low amplification factor to a high amplification factor within a certain period of time, and when the amplified output of one photodetector reaches a certain set value, the amplification factor of the other photodetector is The state of the output of the light-receiving element is stored as a voltage source and applied to one input terminal of the comparator circuit, and then the photographing lens is driven from one extreme position of the movable range to the other extreme position. In conjunction with the operation, the potential of the other input terminal of the comparator circuit is swept from one extreme value to the other extreme value, and when the potentials of both input terminals match, the driving of the photographing lens is stopped. A distance measuring device characterized by: 2. A patent claim characterized in that when the amplified output of one of the light receiving elements does not reach a certain set value within a certain period of time, the photographing lens is prioritized and stopped at the extreme position on the far side. The range measuring device according to item 1. 3. In a triangular distance measuring device in which light emitted from a light emitting element is projected toward a distance measuring target and the reflected light is received by two adjacently arranged light receiving elements, the output of each of the light receiving elements is The amplification factor of the amplification circuit that amplifies is swept from a low amplification factor to a high amplification factor within a certain period of time, and when the amplified output of one photodetector reaches a certain set value, the output of the other photodetector is The state is memorized as a voltage value and applied to one input terminal of the window comparator circuit, and
A servo that applies a potential corresponding to a position in the movable range of the photographic lens to the other input terminal of the window comparator circuit, and that is connected between the output terminals of the comparator circuit and rotates in accordance with the direction of the unbalanced input voltage. The photographic lens is driven by a motor, and when the potentials of both input terminals match within a predetermined threshold having a certain width, the rotation of the servo motor is stopped to stop driving the photographic lens. A distance measuring device characterized by: 4. A patent claim characterized in that when the amplified output of one of the light receiving elements does not reach a certain set value within a certain period of time, the photographing lens is prioritized and stopped at the extreme position on the far side. The range measuring device according to item 3. 5. In a triangular distance measuring device in which light emitted from a light-emitting element is projected toward a distance measurement target and the reflected light is received by two adjacently arranged light-receiving elements, the output of each of the light-receiving elements is The amplification factor of the amplification circuit that amplifies is swept from a low amplification factor to a high amplification factor within a certain period of time, and when the amplified output of one photodetector reaches a certain set value, the output of the other photodetector is The voltage value of the state is converted into a digital value and stored, and then the photographing lens is driven from one extreme position of the movable range to the other extreme position, and the step amount of the drive is converted into a digital value by an encoder. 2. A distance measuring device, characterized in that when the converted digital value matches the stored digital value, driving of the photographing lens is stopped. 6. A patent claim characterized in that when the amplified output of one of the light receiving elements does not reach a certain set value within a certain period of time, the photographing lens is prioritized and stopped at the extreme position on the far side. The range measuring device according to item 5.