JPH0342608B2 - - 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 apparent output of a light-receiving element circuit from zero or a very small value by simple means without having the drawbacks of the conventional example described above, so that the output of a comparison circuit can be easily distinguished. The object of the present invention is to provide a distance measuring device that determines the distance measuring state when a 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 = 16KH ₂ , and the following
2 is a time forming circuit (time t=
25ms), 3 is an AND gate, 4 is a transistor,
5 is an inverter, 6 is a transistor, 7 is a constant current circuit, 8 is a capacitor, 9 is a buffer circuit, 1
0, 11, and 12 are transistors forming a constant current circuit; 13 is an infrared light emitting diode (hereinafter referred to as
IRD), 14 and 15 are respectively IRD13
A silicon photodiode (hereinafter referred to as a photodiode) as a light-receiving element is arranged adjacent to the base line length direction so as to receive the light projected from the object and reflected by the distance measurement target.
16 and 17 are husband AC amplifier circuits, 18 and 19 are band filter circuits (center frequency o=16KHz, hereinafter referred to as BPF), 20 and 21 are detection circuits, 22 and 23 are smoothing circuits, 24 and 25 are DC amplifier circuits, 26 are comparator circuits, 27 and 28
29 is a constant current circuit and a resistor that provides a reference voltage Vr to the inverting input terminal (-) of the comparator circuit 26;
is an AND gate, 30 is an analog switch, 31
is an inverter, 32 is a capacitor, 33 is a buffer circuit, 34 is a comparator circuit (the comparator circuit is hereinafter commonly referred to as CMP), 3
5 and 36 are non-inverting input terminals (+) of CMP34
a constant current circuit and a potentiometer that provide a displacement voltage corresponding to the amount of movement of the photographing lens from one extreme position to the other extreme position in the movable range;
7 is an R/S type flip-flop circuit (hereinafter referred to as
FF), 38 is an AND gate, 39 is a transistor, and 40 is an electromagnet for stopping the movement of the operating member (lens settling) of the photographic lens. Next, in FIG. 2, 41 is a lens setting ring, which is arranged rotatably around the optical axis.
In addition, the spring 42 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 41a and a ratchet tooth 41b. .
Reference numeral 43 denotes a lens-driving release electromagnet, which is composed of an iron core 43a, a coil 43b, and a permanent magnet 43c. Reference numeral 44 designates an iron piece lever for the release, which is pivotally connected to the shaft 45 and given left rotation by a spring 46, and includes a hook 44a that can be engaged with the stepped portion 41a of the lens setting ring 41, and an iron core of the electromagnet 43. An iron piece 44b opposite to 43a is formed. 47 is a pin, iron piece lever 44
The amount of left rotation is limited. Reference numeral 48 denotes a locking iron piece lever pivotally mounted on a shaft 49 and given dextrorotation by a spring 50, and a hook 48a capable of engaging with the ratchet teeth 41b of the lens setting ring 41;
Electromagnet 40, which is the same as in FIG.
An iron piece 48b facing the is formed. Note that the potentiometer 36 in FIG.
As shown in FIG. 2, the lens setting ring 41
The brush 36a is supported by a resistor 36c and a conductor 36d formed on a substrate 36b. 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 37 is released. Then, the OSC1 operates to generate a clock pulse with a period of 62.5Ms, and the output of the time forming circuit 2 is inverted to the "H" level for a time period 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. On the other hand, while the output of the time forming circuit 2 is inverted to the "H" level for a time of 25 ms, the output of the inverter 5 is inverted to the "L" level and the transistor 6 is cut off. When the constant current is I and the capacitance of the capacitor 8 is C, the voltage V at the output terminal a of the buffer circuit 9 is given by the relational expression V=(1/C)I・t. It rises as shown in A. As a result, the collector-emitter current (i ₁ ) flowing through the transistor 10 gradually increases, and the collector-emitter current (i ₂ ) of the transistor 12 also increases in proportion to the current (i ₁ ). become. Therefore, in response to the conduction and cutoff of the transistor 4, the current (i ₂ ) of the transistor 12 increases intermittently as shown by the circles, and the IRD 13 is pulsed and its light emitted. The amount increases monotonically from a small amount of light to a large amount of light. The light projected by the lighting of the IRD 13 is reflected from the distance measurement target and received by the SPDs 14 and 15, and as a result, the received light output at points c and c' is superimposed on the DC component due to natural light, as shown in ○c. Occur. Also, d and after the AC amplifier circuits 16 and 17
The output at point d' appears amplified as shown in ○D. Furthermore, the outputs at points e and e' after BPF18 and 19 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 20 and 21 are as shown in ◯, and after passing through the smoothing circuits 22 and 23, the output waveforms of the DC amplifier circuits 24 and 25
The output voltages Vg and Vg' at the subsequent points g and g' gradually rise from the predetermined values, as shown in ◯. 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 on the SPD 14 as shown in (a ₁ ) and (a ₂ ). , it is very narrow to SPD15, so g
The output voltage Vg at the point is sufficiently higher than the output voltage Vg' at the point g', and the potentials at the points g and g' increase while maintaining this relationship. Also, at this stage, the AND gate 29 is closed and the output of the inverter 31 is at the "H" level, so the analog switch 30 is open and the capacitor 32 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 26 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 29 is opened and its output is inverted to the "H" level, and the FF 37 is set to invert and hold the output Q to the "H" level, and the output of the inverter 31 is inverted to the "L" level and the analog switch 30 is inverted. 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 32.
Vg′ (V ₁ ) is stored. Further, the voltage V ₁ is amplified by the buffer circuit 33 and applied to the inverting input terminal (-) of the CMP 34 . Note that in the CMP 34, since the potentiometer 36 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 38 opens the gate and makes the transistor 39 conductive, the electromagnet 40 is excited and holds the iron piece lever 48 by attraction. Then, after the end of the previous time t, the coil 43b of the electromagnet 43 is turned on by a circuit operation (not shown).
When pulsed in a direction to cancel the magnetic force of the permanent magnet 43c, the iron piece lever 44 is rotated to the left by the tension of the spring 46, and the hook 44a is removed from the stepped portion 41a of the lens setting ring 41. As a result, the ring 41 begins to rotate to the right due to the tension of the spring 42,
The photographing lens is displaced from the infinity position to the close distance position, and the brush 36a is slid on the resistor 36c and the conductor 36d, thereby displacing the potentiometer 36 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 34 drops to the potential at the inverting input terminal (-), the output of the CMP 34 is inverted to the "L" level and the AND gate 38 is closed. the result,
Since the transistor 39 is cut off and the electromagnet 40 is demagnetized, the iron lever 48 rotates clockwise due to the tension of the spring 50, and the hook 48a meshes with one of the ratchet teeth 41b, stopping the lens setting ring 41 from rotating clockwise. The photographing lens is then fixed at a predetermined position. In addition, if the object to be measured is located a little further away, for example, as shown in (b ₁ ) and (b ₂ ), the voltage corresponding to the above-mentioned memory voltage V ₁ becomes the voltage V ₂
Changes to Furthermore, if _the object to be _measured is located further away, the reflected light spot 2), what corresponds to the above-mentioned storage voltage V ₁ changes to voltage V ₃ . Furthermore, if the object to be measured is located at a very far distance, the reflected light spot X' will be wider toward the SPD 15, as shown by the chain line in (c ₁ ) and (c ₂ ). , due to the extremely long distance, the output voltage Vg does not reach the reference voltage Vr within the previous time t (this may also happen when the distance measurement target has a low reflectance), and the output of the CMP26 becomes "L". '' level, and 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 29 cannot be inverted to the ``H'' level. Therefore, the FF 37 is not set and the output Q is kept at the "L" level, keeping the AND gate 38 closed. As a result, the electromagnet 40 is not excited from the initial state and does not attract the iron piece lever 48, so the lens setting 4
1 rotates to the right and the first tooth of the ratchet tooth 41b opposes the hook 48a, the iron piece lever 48 immediately rotates to the right, and the hook 48a moves to the right side of the ratchet tooth 41b.
, the right rotation of the lens setting ring 41 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 by using the output voltage of the buffer circuit 33 as an input and the states of the NAND gates 57 and 58 as outputs. ) 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 buffer circuit 33 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 buffer circuit 33 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 is "H" level, and the output of NAND gate 57 is "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 "H" 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 buffer circuit 33 is
The A/D converter circuit 71 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 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 using a simple configuration that monotonically increases the amount of light emitted by the light emitting element from a small amount of light to a large amount of light without performing logarithmic compression of the output of the light receiving element or automatic gain adjustment of the amplifier 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. 1... Clock pulse generation circuit, 2... Time forming circuit, 9 and 33... Buffer circuit, 13...
Infrared light emitting diode, 14 and 15...Silicon photodiode, 16 and 17...AC amplifier circuit, 18 and 19...Band filter circuit, 20
and 21...detection circuit, 22 and 23...smoothing circuit, 24 and 25...DC amplifier circuit, 36 and 5
5... Potentiometer, 40... Electromagnet, X and X'... Reflected light spot, 41 and 67... Lens setting, 66 and 78... Motor, 7
1... 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 amount of light emitted by the light emitting element is monotonically increased from a small amount of light to a large amount of light within a certain period of time, and when the output of the one light receiving element circuit reaches a certain set value, the state of the output of the other light receiving element circuit is changed. The voltage value 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 comparator circuit is The electric potential of the other input terminal of the circuit is swept from one extreme value to the other extreme value, and when the electric potentials of both input terminals match, the driving of the photographic lens is stopped. distance measuring device. 2. Claims characterized in that when the output of one of the light-receiving element circuits 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 distance measuring device according to item 1. 3. In a triangular distance measuring device in which light emitted from a light emitting element is projected towards a distance measurement target and the reflected light is received by two adjacently arranged light receiving elements, the amount of light emitted by the light emitting element is is monotonically increased from a small light amount to a large light amount within a certain period of time, and when the output of the one light receiving element circuit reaches a certain set value, the state of the output of the other light receiving element circuit is stored as a voltage value. A voltage is applied to one input terminal of the window comparator circuit, and a potential corresponding to a position in the movable range of the photographing lens is applied to the other input terminal of the window comparator circuit, and the input terminal is connected between the output terminals of the comparator circuit. The photographing lens is driven by a servo motor that rotates in accordance with the direction of voltage imbalance, 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. A distance measuring device characterized in that the driving of the photographing lens is stopped by stopping the photographing lens. 4. Claims characterized in that when the output of one of the light-receiving element circuits 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 distance 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 amount of light emitted from the light emitting element is is monotonically increased from a small amount of light to a large amount of light within a certain period of time, and when the output of the one light receiving element circuit reaches a certain set value, the voltage value of the output state of the other light receiving element circuit is converted to a digital value. After that, 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 amount by an encoder, and the digital amount is A distance measuring device, characterized in that the driving of the photographing lens is stopped when the distance measuring device matches a digital value. 6. Claims characterized in that when the output of one of the light-receiving element circuits 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 distance measuring device according to item 5.