JPH0342609B2 - - 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 reflects the reflected light between a common electrode and a pair of detectors. The present invention relates to an improvement in a triangular distance measuring device that receives light with a semiconductor optical position detecting element having an electrode. Conventionally, as a distance measuring device using the method described above,
This method has been proposed in Japanese Patent Application Laid-Open No. 177107/1983. 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 semiconductor optical position detection element from an apparently zero or minute value by simple means without having the drawbacks of the conventional example, and to make a discrimination using a comparison circuit. The object of the present invention is to provide a distance measuring device that determines the distance measuring state when a certain set 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 onto the object to be measured. 6 is a semiconductor optical position detection element, which has a semiconductor substrate 7 having a relatively large surface;
A semiconductor layer 8 of a conductivity type different from that of the substrate 7 is formed on one surface of the substrate 7 . A resistive layer 9 is formed on the semiconductor layer 8, and the resistive layer 9
A pair of electrodes (for detection) 9a and 9b are provided at both ends of the semiconductor substrate 7, and a common electrode 10 is provided on the semiconductor substrate 7. 11 and 12 are AC amplifier circuits, 13 and 1, respectively.
4 is an AC amplifier circuit equipped with gain (amplification factor) adjustment input terminals 13a and 14a, and 15 and 16 are band filter circuits (center frequency o=16KHz), respectively.
(hereinafter referred to as BPF), 17 and 18 are detection circuits, respectively, 19 and 20 are smoothing circuits, and 2
1 and 22 are DC amplifier circuits, 23 is an inverter, 24 is a transistor, 25 is a constant current circuit, 2
6 is a capacitor, 27 is a current amplification circuit, 28, 2
9 and 30 are comparator circuits (hereinafter referred to as CMP), respectively.
), 31 is a constant current circuit, 32, 33 and 34 are reference voltages Vr ₁ , Vr ₂ and Vr ₃ applied to the inverting input terminal (-) of CMP 28 and the non-inverting input terminal (+) of CMP 29, 30, respectively. Partial voltage resistance to give, 35
are AND gates, 36 and 37 are D-type flip-flop circuits, and 38 is an RS-type flip-flop circuit (flip-flop circuits are hereinafter commonly referred to as FF), which are connected as shown in the figure. . Next, the operation shown in FIG. 1 will be explained with reference to FIG. 2. 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 FFs 36, 37, and 38 are released from reset. Then, the clock pulse generating circuit 1 operates to generate a clock pulse with a period of 62.5 μs, and the output of the time forming circuit 2 is inverted to the "H" level for a time of t=25 ms. 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 this, and as a result, the IRD 5 lights up in pulses. The light projected by the lighting of the IRD 5 is reflected from the object to be measured and is received by the semiconductor optical position detection element 6. Here, when the reflected light spot X hits between the electrodes (for detection) 9a and 9b, a current I ₁ flows from the point of incidence to the electrode 9a through the resistance layer 9, a current I ₂ flows to the electrode 9b, and also to the common electrode. A current I ₃ flows into each of the terminals 10 and the following relationship holds between them. I ₃ = I ₁ + I ₂ And if the resistance of the resistance layer 9 is made uniform,
Assuming that the distance between the incident point of the reflected light spot X and the electrode 9a is 1 ₁ and the distance between the incident point and the electrode 9b is 1 ₂ , the following relationship holds: 1 ₁ ·I ₁ =1 ₂ ·I ₂ . Based on this condition, the received light output at points a and a' is:
As shown in ○A, it is generated by being superimposed on the DC component due to natural light. Further, the outputs at points b and b' after the AC amplifier circuits 11 and 12 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 23
The output of transistor 2 is inverted to "L" level, and
4 is cut off, the capacitor 26 is charged with a constant current by the constant current circuit 25. If the constant current is I and the capacitance of the capacitor 26 is C, then the voltage V at the output terminal c of the current amplification circuit 27 is V= According to the relational expression (1/C)It, it increases as shown by ◯C. That is, in the AC amplifier circuits 13 and 14, the potentials of the gain adjustment input terminals 13a and 14a, 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 is as shown in the waveform shown in ◯D. Also, the outputs at points e and e' after BPF15 and 16 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 and ' after the detection circuits 17 and 18 are as follows:
The output voltages Vg and Vg' at points g and g' after passing through the smoothing circuits 19 and 20 and the DC amplifier circuits 21 and 22 gradually rise from the predetermined values, as shown in ○g. . As shown in FIG. 2, when the object to be measured is located at a short distance, the reflected light spot Since the shift is 1 ₁ ≪ 1 ₂ , the output voltage Vg at point g becomes the output voltage at point g′
When the output voltage Vg reaches the reference voltage Vr ₁ and is sufficiently higher than Vg', the output of the CMP28 is inverted to the "H" level and remains "H" for the previous time t.
AND gate 35 to which a level signal was given
opens and its output is inverted to "H" level. On the other hand, at that point, the output voltage Vg' at point g' has not even reached the reference voltage Vr ₃ , so CMP29 and CMP30
Both outputs remain at the "H" level. Therefore, the FFs 36 and 37 whose clock is the rising signal of the output of the AND gate 35 to "H" level are as follows.
Both read "H" level signals, store "H" level signals in their respective output terminals Q ₁ and Q ₂ ,
Also, FF3 uses the rising signal as a set pulse.
8, the output terminal _Q3 is inverted to the "H" level. Furthermore, when the object to be measured is located at a medium distance position, the reflected light spot X is biased to the left with respect to the semiconductor optical position detection element 6, as shown in FIG. 2 b1 and b2, and 1 ₁ <1. ₂ , and the output voltage Vg' is between Vr ₂ < Vr ₃ due to the same operation, so FF36
Output terminal _Q1 of FF
The output terminals Q ₂ of FF 37 each store a signal at "L" level, and the output terminal Q ₃ of FF 38 is inverted to "H" level. Furthermore, if the object to be measured is located at a boundary position to a long distance, the reflected light spot Since the condition is 1 ₁ ≒ 1 ₂ , the output voltages Vg and Vg' are almost equal, and at the time of the determination, the output voltage Vg' is equal to the reference voltage.
Since it is higher than Vr ₂ , FF36 and 37
The respective output terminals _Q1 and _Q2 of the FF38 store "L" level signals, and the output terminal _Q3 of the FF38 stores "H" level signals.
Flip to level. Furthermore, when the object to be measured is located at a very far distance, the reflected light spot X' is shifted to the right side with respect to the semiconductor optical position detection element 6, as shown by the chain line at c1 and _c2 . ＞1 ₂ , but due to the extremely long distance, the output voltage Vg is the same as the previous time t.
The reference voltage Vr ₁ is not reached within the range (this may also happen if the distance measurement target has a low reflectance),
The output of CMP28 remains at "L" level,
When the time t ends, the AND gate 35 closes the gate, so the FF 38 is not set and the output terminal _Q3 remains at the "L" level. Note that at this time, the output of the AND gate 35 does not invert to the "H" level, so the FF36
and 37 do not perform a read operation. That is, as shown in the truth value chart in Figure 3, FF
It is set to distinguish near, medium and long distance based on the signal level status of output terminals Q ₁ and Q ₂ of FF 36 and 37, and further, when output terminal Q ₃ of FF 38 is at "L" level. is FF36 and 37
This is set to give priority to long-distance discrimination. Further, the reference voltage to the CMPs 29 and 30 in FIG. 1 is a fixed bias, and the output voltage Vg' and the output voltage Vg are compared in absolute value. In the embodiment of FIG. 4, the reference voltage to the CMPs 29 and 30 is given by dividing the fluctuating output voltage Vg, and therefore the output voltage Vg' is the output voltage
Comparisons are made as quantities in proportion to Vg. Note that Vb of the voltage dividing circuit is biased to, for example, the normal voltage level of the light receiving output circuit of the semiconductor optical position detection element 6 when the IRD 5 is not operating. In addition, in the circuit operation shown in FIG. 1, when the output of the CMP 28 is inverted to the "H" level, the state of the output voltage Vg' is determined, but the AND gate 35
Due to the following accumulated operation delay time, the determination may lack accuracy. On the other hand, the feature of the embodiment shown in FIG. 4 is that, as mentioned above, the output voltage Vg' is
Since the determination is made based on the ratio to Vg, the accuracy can be improved compared to the previous embodiment. Note that the number of stages of the distance measurement output mentioned above can be increased or decreased, and when determining a long distance using FF38,
It is also possible to issue a warning at the same time. In the above embodiment, the distance measurement output is obtained digitally according to the level and number of stages of the reference voltages (Vr ₂ , Vr ₃ ), but below is an example in which the distance measurement output is further divided into smaller parts. I will explain about it. First, the first one will be explained with reference to FIGS. 5 and 6. Note that the same elements as in the previous embodiment are given the same reference numerals. In FIG. 5, 41 is a comparator circuit;
2 and 43 are constant current circuits and resistors that apply a reference voltage Vr to the inverting input terminal (-) of the comparator circuit 41, 44 is an AND gate, 45 is an analog switch, 46 is an inverter, 47 is a capacitor, 4
8 is a current amplification circuit, 49 is a comparator circuit (the comparator circuit is hereinafter commonly referred to as CMP), and 50 and 51 are connected to the non-inverting input terminal (+) of CMP 49 on one side in the movable range of the photographing lens. A constant current circuit and a potentiometer that provide a displacement voltage corresponding to movement from one extreme position to the other extreme position, 52 an RS type flip-flop circuit (hereinafter referred to as FF), 53 an AND gate, 54 a transistor, 55 is an electromagnet that stops the movement of the operating member (lens setting) of the photographic lens. Next, in FIG. 6, 56 is a lens setting ring, which is arranged rotatably around the optical axis.
In addition, the spring 57 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 56a and a ratchet tooth 56b. .
Reference numeral 58 denotes a lens-driving release electromagnet, which is composed of an iron core 58a, a coil 58b, and a permanent magnet 58c. Reference numeral 59 designates an iron piece lever for the release which is pivotally connected to the shaft 60 and given left rotation by a spring 61, and includes a hook 59a that can be engaged with the stepped portion 56a of the lens setting ring 56 and an iron core of the electromagnet 58 . An iron piece 59b opposite to 58a is formed. 62 is a pin, iron piece lever 59
The amount of left rotation is limited. Reference numeral 63 designates a locking iron piece lever pivotally mounted on a shaft 64 and given dextrorotation by a spring 65, and a hook 63a capable of engaging with the ratchet teeth 56b of the lens setting ring 56;
Electromagnet 55, which is the same as in FIG.
An iron piece 63b facing the is formed. Note that the potentiometer 51 in FIG.
As shown in FIG. 6, the lens setting ring 56
The brush 51a is supported by a resistor 51c and a conductor 51d formed on a substrate 51b. Therefore, the operations shown in FIGS. 5 and 6 will be explained together with FIG. 2 (see voltages in parentheses). Similarly to the above, in the states a1 and a2 of Fig. 2,
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 44 is closed and the output of the inverter 46 is at the "H" level, so the analog switch 45 is open and the capacitor 47 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 41 is inverted to the "H" level, and as a result, the AND gate to which the "H" level signal was applied for the previous time t 44 is opened and its output is inverted to the "H" level, and the FF 52 is set to invert and hold the output Q to the "H" level, and the output of the inverter 46 is inverted to the "L" level and the analog switch 45 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 47.
Vg' and V1 are stored. Moreover, the voltage V1 is
It is amplified by the current amplification circuit 48 and applied to the inverting input terminal (-) of the CMP 49 . In addition, since the potentiometer 51 which applies an input voltage to the non-inverting input terminal (+) of the CMP 49 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 53 opens the gate and makes the transistor 54 conductive, the electromagnet 55 is energized and holds the iron piece lever 63 by attraction. Then, after the end of the previous time t, the coil 58b of the electromagnet 58 is turned on by a circuit operation (not shown).
When pulsed in a direction that cancels the magnetic force of the permanent magnet 58c, the iron piece lever 59 is rotated to the left by the tension of the spring 61, and the hook 59a is removed from the stepped portion 56a of the lens setting ring 56. As a result, the ring 56 begins to rotate to the right due to the tension of the spring 57.
The photographing lens is displaced from the infinity position to the close distance position, and the brush 51a is slid on the resistor 51c and the conductor 51d, thereby displacing the potentiometer 51 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 49 drops to the potential at the inverting input terminal (-), the output of the CMP 49 is inverted to the "L" level and the AND gate 53 is closed. the result,
Since the transistor 54 is cut off and the electromagnet 55 is demagnetized, the iron lever 63 rotates clockwise due to the tension of the spring 65, and the hook 63a engages with one of the ratchet teeth 56b, stopping the lens setting ring 56 from rotating clockwise. The photographing lens is fixed in a predetermined position. Furthermore, when the object to be measured is located a little further away, as shown in FIG. 2 b1 and b2, for example, the voltage corresponding to the above-mentioned storage voltage V1 changes to voltage V2. Furthermore, if the object to be measured is located further away, for example, as shown by the solid lines in FIG. 2 C1 and C2 (the reflected light spot case), the voltage corresponding to the above-mentioned storage voltage V1 changes to voltage V3. Furthermore, if the object to be measured is located at a very far position, the reflected light spot X' will be biased to the right with respect to the semiconductor optical position detection element 6, as shown by the chain lines in FIGS. 2C1 and C2. , due to the extremely long distance, the output voltage Vg is equal to the reference voltage Vr within the previous time t.
(This may also happen when the distance measurement target has a low reflectance), the output of the CMP 41 remains at the "L" level, and when the time t ends, the output of the time forming circuit 2 Once returned to the "L" level, the output of the AND gate 44 cannot be inverted to the "H" level. Therefore, FF52 is
It is not set and the output Q is held at the "L" level, keeping the AND gate 53 closed. As a result, since the electromagnet 55 is not excited from the initial state and does not attract the iron piece lever 63, the lens setting ring 5
6 rotates to the right and the first tooth of the ratchet tooth 56b opposes the hook 63a, the iron piece lever 63 immediately rotates to the right and the hook 63a moves to the right.
, the right rotation of the lens setting ring 56 is stopped, and the photographing lens is fixed at the infinity position. Next, another embodiment will be described with reference to FIGS. 7 and 8. Note that the same elements as in the previous embodiment are given the same reference numerals. 66, 67 are CMP, 68, 69 and 70 are constant current circuits, resistors and potentiometers, 71, 7
2 and 73 are NAND gates (note that the above elements constitute a window comparator circuit in which the output voltage of the current amplifier circuit 48 is input and the states of NAND gates 72 and 73 are output).
4 is an AND gate, 75 is an OR gate, 76 is an inverter, 77 to 80 are transistors, and 81 is a motor. A lens setting ring 82 is rotatably arranged around the optical axis, and forms a partial gear 82a. A pinion 83 is fixed to the rotating shaft of the motor 81, which is the same as that shown in FIG. 84 is an intermediate gear that meshes with the pinion 83 and the partial gear 82a of the lens setting ring 82. Note that the potentiometer 70 in FIG.
As shown in FIG. 8, the lens setting ring 82
The brush 70a is supported by a resistor 70c and a conductor 70d formed on a substrate 70b. As mentioned above, the output voltage of the current amplification circuit 48 is
Apart from extreme distances, the distance is set to increase as the distance to the target is near, medium, and far. Since it is a window comparator circuit, the output voltage Vx of the current amplifier circuit 48 is CMP
If the voltage is higher than the voltage Vy of the non-inverting input terminal (+) of CMP66, the output of CMP66 is "L" level,
Since the output of CMP67 is at "H" level, the output of NAND gate 71 is at "H" level,
The output of NAND gate 72 is at "H" level, and the output of NAND gate 73 is at "L" level. On the other hand, if the output voltage Vx is lower than the voltage Vz of the inverting input terminal (-) of the CMP67, the CMP67
Since the output of the CMP 67 is at the "H" level and the output of the CMP 67 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 81 rotates in corresponding directions to drive the lens setting ring 82. Furthermore, when the output voltage Vx is placed in the relationship Vy>Vx>Vz, the outputs of CMP66 and CMP67 both become "H" level and the output of NAND gate 71 becomes "L" level, so the NAND gate 72
and 73 both go to the "H" level, and at this time, since both inputs of the motor drive circuit are at the same potential, the motor 81 does not rotate. That is, by operating the potentiometer 70 in conjunction with the movement of the lens setting ring 82 driven by the rotation of the motor 81, 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, FF52 is not set,
When the output Q remains at the "L" level, the output of the AND gate 74 is at the "L" level, and the OR gate 75
The output of Vx is held at “H” level, and the output voltage Vx
is the same as when In addition, 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 81, 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. 86 is a 4-bit A/D converter circuit, 87 to 90 are AND gates, and 91 is a 4-bit A/D converter circuit, for example.
BIT magnitude comparator circuit, 92
93 is a motor that drives lens setting by its rotation; 94 is a motor 9;
This is, for example, a 4-bit encoder that digitizes the rotation amount of 3. The analog amount of the output voltage of the current amplification circuit 48 is
The A/D converter circuit 86 outputs signals from "L", "L", "L", "L" to "H", "H" through four output terminals.
”、
It is encoded as one of the 16 levels of digital quantities 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 86 is
It is input to the magnitude comparator circuit 91 through AND gates 87-90. The lens setting is driven by rotating the motor 93 by the motor drive circuit 92. As a result, the photographing lens is displaced from the infinity position to the close distance position. When the output of an encoder 94 that converts the amount of rotation of the motor 93 into a digital amount matches the input of the comparator circuit 91, the motor 93 is stopped and the photographing lens is fixed at a predetermined position. Also, as mentioned above, FF52 is not set,
When the output Q remains at the "L" level, the outputs of AND gates 87 to 90 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 52 is not set and a long-distance state is set, an alarm may also be issued. As described above, the present invention achieves stable operation using 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.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is an explanatory diagram showing the relationship between the state of the reflected light spot and the output voltage with respect to the light receiving element, and Fig. 3 shows an example of the distance measurement output. Diagrams of truth values, Figures 4 and 5
7 and 9 are partial circuit diagrams showing other embodiments of the present invention, and FIGS. 6 and 8 are partial circuit diagrams of the photographing lens drive mechanism corresponding to FIGS. 5 and 7, respectively. It is an explanatory diagram showing an example. DESCRIPTION OF SYMBOLS 1... Clock pulse generation circuit, 2... Time forming circuit, 5... Infrared light emitting diode, 6... Semiconductor optical position detection element, 9a, 9b... Electrode (for detection), 10... Common electrode, 11, 12 , 13 and 14...AC amplifier circuit, 13a and 14a...gain adjustment input terminal, 15 and 16...bandwidth filter circuit, 17 and 18...detection circuit, 19 and 2
0... Smoothing circuit, 21 and 22... DC amplifier circuit, 27 and 48... Current amplifier circuit, 51 and 70... Potentiometer, 55... Electromagnet, 5
6 and 82...Lens setting, 81 and 9
3...Motor, 86...A/D converter circuit,
91...Magnitude comparator circuit, 92
...Motor drive circuit, 94...Encoder, X and X'...Reflected light spot.

Claims (1)

[Claims] 1. A triangular distance measurement method in which light emitted from a light emitting element is projected toward a distance measurement target, and the reflected light is received by a semiconductor optical position detection element having a common electrode and a pair of detection electrodes. In the distance measuring device, the amplification factor of an amplifier circuit that amplifies the output between the common electrode and each detection electrode in the semiconductor optical position detection element is swept from a low amplification factor to a high amplification factor within a certain period of time, and the common electrode and the state of the amplified output between the common electrode and the other detection electrode is determined when the amplified output between the common electrode and the other detection electrode reaches a certain set value. range device. 2. The distance measuring device according to claim 1, wherein the amplified output between the common electrode and the other detection electrode is compared with a plurality of levels. 3 If the amplified output between the common electrode and one of the detection electrodes does not reach a certain set value within a certain period of time,
Claim 1 or 2, characterized in that the distance measurement output is determined as a long distance.
Distance measuring device described in section. 4. In a triangulation distance measuring device in which light emitted from a light emitting element is projected towards a distance measuring target and the reflected light is received by a semiconductor optical position detection element having a common electrode and a pair of detection electrodes, The amplification factor of the amplifier circuit that amplifies the output between the common electrode and each detection electrode in the semiconductor optical position detection element is swept from a low amplification factor to a high amplification factor within a certain period of time, and the common electrode and one detection electrode are When the amplified output between the common electrode and the other detection electrode reaches a certain set value, the amplified output between the common electrode and the other detection electrode is set as a predetermined ratio to the amplified output between the common electrode and one detection electrode. A distance measuring device characterized in that the distance measuring device makes a determination by comparing the amount of . 5. The distance measuring device according to claim 4, wherein the amplified output between the common electrode and the other detection electrode is compared with a plurality of levels. 6 If the amplified output between the common electrode and one detection electrode does not reach a certain set value within a certain period of time,
Claim 4 or 5, characterized in that the distance measurement output is determined as a long distance.
Distance measuring device described in section. 7. In a triangulation distance measuring device in which light emitted from a light emitting element is projected towards a distance measuring target and the reflected light is received by a semiconductor optical position detection element having a common electrode and a pair of detection electrodes, The amplification factor of the amplifier circuit that amplifies the output between the common electrode and each detection electrode in the semiconductor optical position detection element is swept from a low amplification factor to a high amplification factor within a certain period of time, and the common electrode and one detection electrode are When the amplified output between the common electrode and the other detection electrode reaches a certain set value, the state of the amplified output between the common electrode and the other detection electrode is stored as a voltage value 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, and in conjunction with the driving operation, the potential of the other input terminal of the comparator circuit is changed from one extreme position to the other extreme position. 1. A distance measuring device, characterized in that the distance measuring device is configured to sweep toward a position and stop driving the photographing lens when the potentials of both input terminals match. 8 If the amplified output between the common electrode and one detection electrode does not reach a certain set value within a certain period of time,
8. A distance measuring device according to claim 7, characterized in that the photographing lens is stopped at an extreme position on the long distance side with priority. 9. In a triangulation 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 a semiconductor optical position detection element having a common electrode and a pair of detection electrodes, The amplification factor of the amplifier circuit that amplifies the output between the common electrode and each detection electrode in the semiconductor optical position detection element is swept from a low amplification factor to a high amplification factor within a certain period of time, and the common electrode and one detection electrode are When the amplified output between the common electrode and the other detection electrode reaches a certain set value, the state of the amplified output between the common electrode and the other detection electrode is stored as a voltage value and applied to one input terminal of the window comparator circuit, Further, a potential corresponding to the position within the movable range of the photographing lens is applied to the other input terminal of the window comparator circuit, and the circuit is connected between the output terminals of the comparator circuit and rotates in accordance with the direction of the unbalanced input voltage. the photographing lens is driven by a servo motor, and when the potentials of both input voltages match within a predetermined threshold having a certain width, the rotation of the servo motor is stopped, and the driving of the photographing lens is stopped. A distance measuring device characterized in that the distance measuring device is configured to 10 If the amplified output between the common electrode and one of the detection electrodes does not reach a certain set value within a certain period of time, the photographic lens is prioritized and stopped at the extreme position on the far side. A distance measuring device according to claim 9. 11. In a triangulation distance measuring device in which light emitted from a light emitting element is projected towards a distance measuring target and the reflected light is received by a semiconductor optical position detection element having a common electrode and a pair of detection electrodes, Sweeping the amplification factor of an amplifier circuit that amplifies the output between the common electrode and each detection electrode in the semiconductor optical position detection element from a low amplification factor to a high amplification factor within a certain time,
When the amplified output between the common electrode and one detection electrode reaches a certain set value, the voltage value of the amplified output between the common electrode and the other detection electrode is converted into a digital value. After that, the photographing lens is driven from one extreme position to the other extreme position in the movable range, and the step amount of the drive is converted into a digital amount by an encoder, and the digital amount is the stored digital value. The distance measuring device is characterized in that the driving of the photographing lens is stopped when the distance measuring apparatus matches the above. 12 If the amplified output between the common electrode and one of the detection electrodes 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. A distance measuring device according to claim 11.