JPH04204011A - Distance detecting apparatus - Google Patents

Abstract

PURPOSE:To improve the accuracy with a simple constitution when the distance is measured by casting a pulse light to an object to be measured, detecting the spot of the reflecting light, integrating the spot for a predetermined time, and outputting pulse-like distance data having the pulse width proportional to an inverse number of the distance. CONSTITUTION:A spot of the reflecting light is received by a PSD 1. Current outputs I1, I2 are output from both ends of the PSD 1, which are amplified by current amplifying circuits 2, 3 thereby to obtain amplified currents I1a, I2a. Since the sum of the voltages between an anode and a cathode of each diode Q1, Q2 is equal to the voltage between an anode and a cathode of a diode Q3 and the voltage between a base and an emitter of a transistor Q4, a collector current I4 of the transistor Q4 indicates a value obtained by multiplying the ratio of the outputs I1, I2 with a constant current I0 of a constant current source 7. The collector current I4 is integrated in an integrating circuit of a comparator 10, a constant power source 11 or the like, so that the distance data corresponding to the current I4 and proportional to an inverse number of the distance can be obtained. In other words, the current ratio is obtained by a single transistor Q4, thereby preventing measuring errors due to the variations of elements.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a distance detection device, and more specifically, the present invention relates to a distance detection device, and more specifically, a distance detection device provided at a position where a reflected light spot of pulsed light irradiated from a light source to a distance measurement object is formed. continuously detecting the position of the incident light spot according to the distance of the distance measurement target based on the parallax with the light source in the direction of the position change due to the change in the distance,
The present invention relates to a distance detection device using a semiconductor optical position detector that obtains first and second current outputs having a mutual current ratio according to a detected position.

[Conventional technology]

2. Description of the Related Art As a distance measuring method for autofocus (automatic focus adjustment) in so-called compact cameras, there is a method that employs a double image matching method using a passive method that uses external light.

However, in this passive double image matching method, the use of a movable mirror to change the relative position of one image with respect to the other is an essential element, and the use of a movable mirror makes it difficult to maintain durability. Since the distance measurement is based on the contrast information of the subject (distance measurement target) due to the double image matching method, it is highly subject dependent, making it difficult to measure the distance of a subject with low contrast or in dark conditions. There were problems such as poor ranging ability.

Further, the system having such a movable part has the drawback that adjustment is complicated and requires a lot of effort.

On the other hand, the active triangulation method in which light is emitted from the ranging device itself improves the above-mentioned subject dependence, but Items that have movable parts cannot avoid the aforementioned problems such as low durability and complicated adjustment.

On the other hand, in a method that uses an active triangulation method and has no moving parts, light such as infrared light projected from a light emitting part is reflected by the distance measurement target, and this reflected light is transmitted to multiple points. There is a system in which the distance to the object to be measured is determined based on which light-receiving element of the light-receiving unit, which is made up of several light-receiving elements, receives the light.

In the case of this method, there are no moving parts and there are almost no problems in terms of durability, adjustment, etc.

However, in this case, since the light receiving section is quantized, there is a fatal problem that the distance resolution is limited by the number of light receiving elements.

Furthermore, as a type of active method, there is an ultrasonic method in which ultrasonic waves are emitted, waves reflected by a distance measurement object are received, and the distance to the distance measurement object is measured from the time required from sending the waves to receiving the waves.

In this case, the distance is measured using purely electrical processing, so the processing is easy, but it requires a high transmission power, which requires a large power supply, and the power supply used in compact cameras, etc. It is difficult to transmit effective ultrasound waves.

In addition, in order to prevent ultrasonic waves from being transmitted to objects that are not the object of distance measurement and reducing distance measurement accuracy, it is necessary to improve the directivity. area must be increased.

This becomes a big problem when applied to compact cameras and the like.

On the other hand, the following distance detection device is known as one that does not require much power, is easy to adjust, has good durability, and can provide high distance resolution.

As shown in FIG. 2, this distance detection device irradiates a distance measurement object 13 with pulsed light emitted from an LED 12 as a pulse light emitter through a projection lens L1.
3 is configured to pass through the light receiving lens L2 and form an incident image on the PSDI, and this PsDl outputs two outputs from both ends of the PSD depending on the incident position of the reflected light spot. Electrician 0. Output I2. Then, the distance between the light emitting lens L1 and the light receiving lens L2, that is, the base line length S, the light receiving lens L2 and the PSDI
Let f be the distance from the projection lens L1 to the distance measurement target 13, fl be the distance from the reflected light spot on the PSD to the position corresponding to infinity.

holds true.

Since the position of the light spot focused on PSDI corresponds to the ratio of the two current ratios □j I2 output from PSDl, these two current ratios □j I2
Information on the distance Q from to the object to be measured (hereinafter referred to as "object distance to be measured") can be obtained.

Here, the distance to be measured Q and the current output of PSD -, , I,
When looking for the relationship with the ratio L/L, if the total length of PSD is a unit length (that is, -), ■, Ω・□=f−S ・・・・・・・・・(2) I , +
I.

From, ■work/■2 = (1+ −) f −S ・・・・・・
... (3) However, x=1. /I2, and it is known that there is a relationship of y=(1/x)+.

When measuring distance with a distance detection device based on this principle, there is no problem if the distance is measured in a pitch-dark place, but when taking general photographs, pulsed light from a pulsed light emitter is used. Since there is stationary light with a much higher amount of light than that, it becomes impossible to extract the reflected light spot of the pulsed light.

Therefore, in this case, the first current output of PSDI, the second current output
The current ratio crab 2 is received by the first and second detection circuits, the influence of the steady light is removed, and the fluctuations in the photocurrent due only to the reflected light spot of the pulsed light are extracted by logarithmic conversion, respectively. The difference is taken by a difference detection circuit, and the first PSDI,
The present applicant has disclosed various attempts, such as Japanese Patent Laid-Open No. 58-95210, to output a distance detection signal corresponding to the current ratio I, /I, of the second current output I, , I. We have already proposed what was proposed.

FIG. 5 is a circuit diagram showing a conventional example of a distance detection device that logarithmically compresses the first and second current outputs of the PSD and detects the difference between the two to obtain distance measurement information, as described above. be.

In this FIG. 5, 1 is a PSD, and as described above, the first and second PSDs are 2 current specific force I0. I2 is output from both ends.

The first part of this PSDI. The second current ratios 1 and 2 are amplified by current amplification circuits 2 and 3, respectively, and the amplified current outputs Ia and I2a from these current amplification circuits 2 and 3 are respectively amplified by current amplification circuits 2 and 3.
is output.

The current specific powers 11a and I, a of these current amplifier circuits 2 and 3 are logarithmically compressed by diodes Qll and Q12, respectively, and then constitute a difference detection circuit via buffers 4 and 5 and resistors R1 and R2, respectively. The signal is input to the non-inverting input terminal and the inverting input terminal of the operational amplifier 6, and the deviation between the two is amplified to obtain an output V out serving as ranging information from the output terminal of the operational amplifier 6.

Now, in this Figure 5, I, a: current output of current amplifier circuit 2, I2a: current output of current amplifier circuit 3, k: Boltzmann's constant, T: absolute temperature, q: charge of electron, then the calculation The output V out of the amplifier 6 is q
11a.

Note that R4 in FIG. 5 is a feedback resistor, and R3 is a compensation resistor.

FIG. 6 is a block diagram showing a second conventional example of a distance detection device.

In the case of this FIG. 6, as in the case of FIG. 5, the first . The second current outputs ■ and l I2 are amplified by current amplification circuits 2 and 3, respectively.
The amplified current outputs I, a, I, a are output from.

The output terminals of the current amplification circuits 2 and 3 are grounded through logarithmic compression diodes Qll and Q13, respectively, and a common load 12. Therefore, the output terminals of the current amplification circuits 2 and 3 are are logarithmically compressed by diodes Qll and Q13, respectively, and further passed through voltage followers (buffers) 14 and 15 to transistors Q12b and Q
14 bases are supplied.

The collector of transistor Q12b is connected to power supply Vcc, and the collector of transistor Q14 is connected to capacitor C.
1 to the power supply Vcc, and further connected to the switch SW
A constant current is supplied from a constant current source 11 via the comparator 1, and the comparator 10 is connected to an inverting input terminal of the comparator 10.

The emitters of both transistors Q12b and Q14 are commonly connected and grounded via a constant current source 7, and this constant current source 7 and transistor Qi2b.

Q14 constitutes a differential circuit.

Further, a switch SW2 is connected between the inverting input terminal and the output terminal of the comparator 10, and a reference voltage Vref is applied to the non-inverting input terminal of the comparator 10.

These comparators 10 and switch SWI.

An integrating circuit is constituted by SW2, capacitor C1, and constant current source 11.

This comparator 10 has a capacitor C1 at the 1-inverting input terminal.
The voltage Vc1 corresponding to the charging voltage of and the reference voltage V ref
This is a comparison of the following.

In this FIG. 6, the current output I of the current amplifier circuits 2 and 3
, a and I2a are logarithmically compressed by diodes Qll and Q13, respectively, and then passed through buffers 14 and 15 to transistor Q12b.

It is input to the base of Q14, and the difference is input to the base of transistor Q14.
14 collector current appears as 4.

This collector current is obtained by converting the PSDI output into a current.

now, I, a: current output of current amplifier circuit 2, I2a: current output of current amplifier circuit 3, Io: current of constant current source 7, Then, the collector current of transistor Q14 is becomes.

This collector electrician. is integrated in the next-stage integration circuit.

That is, the reference voltage V ref is applied to the non-inverting input terminal of the comparator 10, the switch SWI is turned off, and the switch SW2 is turned on.

In this state, the potential V at the inverting input terminal of the comparator 10
c1, i.e. the charging voltage of capacitor C1, is equal to the reference voltage V ref and therefore comparator 10
The output voltage V out of is at a low level, that is, V r
It is ef.

In this state, at the same time as the switch SW2 is turned off, a light emitting diode (hereinafter referred to as rLEDJ) (not shown) is caused to emit light for a predetermined period of time, and the pulsed light passes through the projection lens and illuminates the object to be measured.

This pulsed light is reflected from the distance measurement target to become a reflected light spot, passes through a light receiving lens, and is imaged on the PSDl, and during the light reception period of this reflected light spot (that is, the LED
), the current output ratio of PSDl changes, and accordingly, the collector current of transistor Q14,
increases, and as a result, the charging voltage of the capacitor C1 decreases.

Therefore, the voltage ■c at the inverting input terminal of the comparator 10
1 decreases to below the reference voltage V ref at the non-inverting input terminal, and the output voltage Vout of the comparator 10 becomes inverted (high level).

Next, after the LED stops emitting light, the potential at the inverting input terminal of the comparator 10 maintains the lowest potential at the end of light emission of the LED for a predetermined period, and the output voltage Vo of the comparator 10
ut remains at a high level.

After this holding period has passed, when switch SW2 is left off and switch SWI is turned on, the current of constant current source 11 flows to the collector of transistor Q14, and the charging potential of capacitor C1 starts to rise due to power supply Vcc. death,
When the voltage vc1 at the inverting input terminal of the comparator 10 becomes equal to the reference voltage V ref at the non-inverting input terminal, the output of the comparator 10, the voltage V out, becomes a low level. At the same time, the switch SW1 is turned off.

In this way, the LED emits light at the same time as the switch SW2 is turned off, and from the time when the light emission starts, the output voltage V out of the comparator 1o becomes a high potential until the potentials of the inverting input terminal and the non-inverting input terminal of the comparator 10 become equal. During this period, while the output voltage of the comparator 10 is at a high potential, the magnitude of the collector current of the transistor Q14 is converted into a pulse width, and therefore the collector current of the transistor Q14 is double integrated and digital This allows you to obtain standardized distance measurement information.

[Problem to be solved by the invention]

Incidentally, when driving a photographing lens associated with distance measurement of a camera, etc., information from a distance detection device is converted into a digital value, and a motor is driven by a pulse output to perform a focusing operation.

However, in the case of the distance detection device shown in FIG.
Distance information corresponding to the SDI current outputs I, , I2 is a linear analog output. Therefore, in order to drive the focusing lens using this distance information, an A/D converter is required to convert the distance information into a digital signal, making the circuit configuration complicated and expensive.

On the other hand, in the case of the distance detecting device shown in FIG. 6, an integrating circuit mainly composed of the comparator 10 has an A/D conversion function that integrates the collector current of the transistor Q14 and digitizes it. Therefore, the output voltage V out of the comparator 10 can be directly applied to drive the motor as distance measurement information.

However, in the case of the conventional example shown in FIG.
12b and Q14 constitute a differential circuit, and variations tend to occur in both transistors Q12b and Q14, and if there is an input offset, an error based on the input offset voltage will occur, making accurate distance measurement impossible. There's a problem.

The present invention has been made in view of the above-mentioned circumstances, and its first purpose is to provide a simple circuit configuration that can be manufactured at low cost, has an A/D conversion function, and is capable of eliminating the need for variations in elements. It is an object of the present invention to provide a distance detection device that prevents errors and has high distance measurement accuracy.

In addition to the above objects, a second object of the present invention is to provide a distance detection device that can be manufactured at a lower cost with a simple circuit configuration.

[Means to solve the problem]

In order to achieve the above first object, the invention of claim 1 has the following features:
Provided at a position where a reflected light spot of pulsed light irradiated from a light source to a distance measurement target is imaged, the position of the incident light spot is changed in accordance with the distance of the distance measurement target based on the parallax with the light source, and the distance is changed. A semiconductor optical position detector that continuously detects the direction of position change and obtains first and second current outputs having a mutual electric current ratio according to the detected position, and a logarithm of the current flowing from the first constant current source. a first diode that compresses the first current output logarithmically; a second diode that logarithmically compresses the first current output and has a cathode to which the anode-cathode voltage of the first diode is applied; and a second diode that compresses the first current output logarithmically; a third diode to be compressed; and the first current output and the second current output by inputting the first current output to the base and applying the voltage between the anode and cathode of the third diode to the emitter. a transistor that outputs a collector current having a value obtained by multiplying the current of the first constant current source by the current of the first constant current source; After a predetermined period of time has elapsed after the irradiation has stopped, a current from the second constant current source flows into the collector, and when the potential of the collector reaches the reference potential, the integral operation is stopped and the current is adjusted to correspond to the collector current and of the distance. The apparatus is characterized by comprising an integrating circuit that outputs pulse-shaped ranging information having a pulse width proportional to a reciprocal number.

In addition, in order to achieve the second object, the invention of claim 2 is provided at a position where a reflected light spot of the pulsed light irradiated from the light source onto the distance measuring object is formed, and the parallax with the light source is The position of the incident light spot according to the distance of the distance measurement target is continuously detected in the direction of position change due to the change in the distance, and the first beam spot has a mutual current ratio according to the detected position.
and a semiconductor optical position detector that obtains a second current output, and a first transistor that logarithmically compresses the current flowing from the first constant current source.

a second transistor to which the first current output is applied and a base-emitter voltage of the first transistor applied to the base; and a third transistor that logarithmically compresses the second current output.

By applying the first current output to the base and applying the base-emitter voltage of the third transistor to the emitter, the ratio between the first current output and the second current output increases. a fourth transistor that outputs a collector current having a value multiplied by the current of the first constant current source;

Integration of the collector current is started simultaneously with the irradiation of the pulsed light to the distance measurement target, and after a predetermined period of time has elapsed after the irradiation of the pulsed light has stopped, the current from the second constant current source is caused to flow into the collector. and an integrating circuit that stops the integrating operation when the potential reaches the reference potential and outputs pulsed ranging information having a pulse width corresponding to the collector current and proportional to the reciprocal of the distance. This is what I did.

[For production]

The semiconductor optical position detector of the distance detection device configured as described above receives the reflection of the pulsed light emitted from the light source and the light spot reflected from the distance measurement target, and measures the distance based on the parallax with the light source. The first. Second
Outputs current output.

The first current output is logarithmically compressed with a second diode and applied to the base of the transistor.

Further, the first diode logarithmically compresses the current from the first constant current source and applies the resulting anode-cathode voltage to the cathode of the second diode.

The third diode logarithmically compresses the second current output,
The anode-cathode voltage is applied to the emitter of the transistor. As a result, the sum of the voltages between the anode and cathode of the first and second diodes, the voltage between the anode and cathode of the third diode, and the sum of the voltage between the base and emitter of the transistor become equal, and the voltage between the base and emitter of the transistor becomes equal. , the vector current becomes a value obtained by multiplying the ratio of the first current output and the second current output by the current of the first constant current source.

This collector current is irradiated with pulsed light to the distance measurement target, and at the same time as the reflected light spot is received, integration is started by the integrating circuit, and the collector current changes depending on the receiving position of the reflected light spot, and the pulsed light is irradiated. When the current from the second constant current source flows to the collector of the transistor after a predetermined period of time after the stop and the collector potential of the transistor becomes equal to the reference voltage, the integrating circuit stops the integrating operation and responds to the collector current and the distance. Pulsed ranging information having a pulse width proportional to the reciprocal is output.

Further, the semiconductor optical position detector in the distance detecting device according to the invention of claim 2 similarly detects the position of the incident light spot corresponding to the distance of the object to be measured based on the parallax with the light source in the direction of the position change due to the change in distance. The first one detects continuously and has a mutual current ratio according to the detection position. A second current output is output.

A first current output is applied to the emitter of the second transistor and the base of the fourth transistor.

The current output is logarithmically compressed with the third transistor.

Further, the first transistor logarithmically compresses the current from the first constant current source and applies the base-emitter voltage to the base of the second transistor, and the third transistor logarithmically compresses the current from the first constant current source and applies the base-emitter voltage to the base of the second transistor. A voltage is applied to the emitter of the fourth transistor.

As a result, the sum of the base-emitter voltages of the first and second transistors becomes equal to the sum of the base-emitter voltages of the third and fourth transistors, and the collector current of the fourth transistor is equal to the sum of the base-emitter voltages of the third and fourth transistors. The value is obtained by multiplying the ratio between the current output of the current output and the second current output by the current of the first constant current source.

The integration of this collector current is started by an integrating circuit at the same time that the reflected light spot is received, and the collector current changes depending on the receiving position of the reflected light spot, and a second constant value is reached after a predetermined time after the pulsed light irradiation stops. When the current from the current source flows to the collector of the fourth transistor and the collector potential of the fourth transistor becomes equal to the reference voltage, the integrating circuit stops the integrating operation, and the voltage increases in proportion to the collector current and to the reciprocal of the distance. outputs pulse-shaped ranging information having a pulse width of .

〔Example〕

Embodiments of the present invention will be specifically described below with reference to the accompanying drawings.

FIG. 1 is a circuit diagram showing the overall configuration of an embodiment of a distance detection device according to the present invention.

In FIG. 1, the same parts as in FIGS. 5 and 6 will be described with the same reference numerals, but prior to explaining the embodiment of FIG. I will start by describing the detection principle.

In FIG. 2, pulsed light emitted from an LED 12 as a pulsed light emitter is irradiated onto a distance measurement object 13 through a light projecting lens L1, and a reflected light spot reflected from the distance measurement object 13 passes through a light receiving lens L2 and then reaches the PSDI. The beam is incident on the beam and is imaged.

As already mentioned, the relationship between the position and distance of this reflected light spot is as follows: Q: Distance from the center of the light emitting lens 1 to the distance measurement target 13, S: Distance between the light emitting lens L1 and the light receiving lens L2 ( baseline length).

f: Distance from the center of light receiving lens 2 to PSDI, d: Distance from the center of PSD 1 to the light receiving position of the reflected light spot. Then, -f d=□...・(7) becomes.

In such a relationship, when the reflected light spot from the distance measurement target 13 is received by PSDI, current outputs -, , I are output from both ends of PsDl, and this current output -, , I
, becomes .

Two such current outputs I2,1. are the first
As shown in the figure, the current is input to current amplification circuits 2 and 3 and amplified there.

An anode of a diode Q2 and a base of a transistor Q4 are connected to the output terminal of the current amplification circuit 2, and the current outputs I and a of the current amplification circuit 2 are respectively input thereto.

The output end of the current amplification circuit 3 is grounded via the diode Q3 and connected to the non-inverting input end of the buffer 15, and the anode of the diode Q3 and the input end of the buffer 15 are connected to the A current ratio crab 2a is added.

Further, a current is supplied from the first constant current source 7 from the anode of the diode Q1 to the ground. The anode of the diode Q1 is connected to the non-inverting input terminal of the buffer 14. The inverting input and output of buffer 14 are connected together, and the output of this buffer is connected to the cathode of diode Q2.

On the other hand, the inverting input terminal and the output terminal of the buffer 15 are directly connected, and the output terminal of the buffer 15 is connected to the transistor Q
It is connected to the emitter of 4.

In addition, the collector of transistor Q4 is connected to capacitor C1.
It is connected to the power supply Vcc via. A constant current flows into this collector from the second constant current source 11 via the switch S'WI.

In addition, the collector of transistor Q4 is connected to comparator 1
The inverting input terminal of the comparator 10 is connected, and a predetermined reference voltage V ref is applied to the non-inverting input terminal of the comparator 10 . A switch SW2 is connected between the inverting input terminal and the output terminal of the comparator 10.

These comparator 10, capacitor C1, switches SWI, SW2, constant current source 11, etc. constitute an integrating circuit that integrates the collector current of transistor Q4.
Pulse-shaped digitized ranging information having a pulse width corresponding to the collector current is obtained, and the integrating circuit also serves as an A/D conversion mechanism.

Next, the operation of the embodiment shown in FIG. 1 will be explained.

By receiving the reflected light spot on PSDI, P
Current output I0. from both ends of SDI. When I2 is output,
These two current outputs I, I2 are amplified by current amplification circuits 2 and 3, respectively, so that current output I >at I2
a is output.

The current output I,a is applied to the anode of diode Q2 for logarithmic compression and is applied to the base of transistor Q4.

Further, the current output I2a is logarithmically compressed by the diode Q3 and is applied to the non-inverting input terminal of the buffer 15.

Furthermore, the current factor of the first constant current source 7. is logarithmically compressed by the first diode Q1, and the anode-cathode voltage V F s of this diode Q1 is applied to the anode of the diode Q2 via the buffer 14.

Similarly, the voltage vF between the anode and cathode of the third diode Q3 is applied to the emitter of the transistor Q4 via the buffer 15.

Here, VFl: Base-emitter voltage of the first diode Q1, S: Reverse saturation current of each diode, vF2: Second
The anode-cathode voltage of the diode Q2, VF: the anode-cathode voltage of the third diode Q3, Vr: the base-emitter voltage of the transistor Q4, 4: the collector current of the transistor Q4, then q Is.

Here, Vt, +VF2=VF3+VF, -(14
), so from equations (10) to (13) above, it becomes. Therefore, since 1. a=k1. ．． 1. If a=kIz, 5 from the above equations (8), (9) and (15), we get Q.

By integrating the obtained collector current I4 of the transistor Q4 in the next stage integration circuit, pulse-shaped ranging information having a pulse width corresponding to the collector current I4 is obtained.

Next, the operation of this integrating circuit will be described using the time chart shown in FIG.

As shown in FIG. 3(a), the switch SW1 is initially turned off, and as shown in FIG. 3(b), the switch SW1 is turned off.
2 is turned on, and a reference voltage V ref is applied to the non-inverting input terminal of the comparator 10. The inverting input terminal of the comparator 10 is connected to the collector of the transistor Q4, and a voltage Vcm corresponding to the charging voltage of the capacitor C1 is applied thereto.

As long as the voltage V c 1 at the inverting input terminal of the comparator 10 is equal to or higher than the reference voltage Vref at the non-inverting input terminal of the comparator 10, as shown in FIG. 3(d).

The output voltage Vout of the comparator 10 is shown in FIG. 3(e).
As shown, it is at L level.

Next, at the same time as the switch SW2 is turned off, the LED 12 shown in FIG. 2 is caused to emit light in a pulsed manner as shown in FIG. 3(C). As a result, the mutual current ratio of PSDI changes, the charge of the capacitor C1 flows to the collector of the transistor Q4, and the voltage Vcm at the inverting input terminal of the comparator 10 increases with the light emission time of the LED 12, as shown in FIG. 3(d). It starts to decrease gradually.

If the voltage Vc1 at the inverting input terminal becomes even slightly lower than the reference voltage Vref at the non-inverting input terminal, the comparator 10
The output voltage Vout changes to H level.

Next, as described above, as the light emission time of the LED 12 passes, the voltage vc1 at the inverting input terminal of the comparator 10 gradually decreases, and when the LED 12 stops emitting light, the voltage vc at the inverting input terminal of the comparator 10 decreases. stop,
The voltage vc1 when the LED 12 stops emitting light is held.

Next, as shown in FIG. 3(a), when the switch SWI is turned on, the current of the second constant current source 11 flows through the switch SWI to the collector of the transistor Q4, and the capacitor C1 starts to be charged. Therefore, the voltage Vc1 at the inverting input terminal of the comparator 1o gradually increases as shown in FIG. 3(d).

When the voltage Vc at the inverting input terminal of the comparator 10 becomes equal to the reference voltage V ref at the non-inverting input terminal of the comparator 10, the comparator 10
The output voltage V out decreases from H level to L level (reference voltage Vref). At the same time, switch S
Turn off WI.

In this way, the output voltage Vout of the comparator 1o
is output as pulsed ranging information having a pulse width corresponding to the collector current of transistor Q4.

That is, the output voltage V out of the comparator 1o is
The collector current I4 of the transistor Q4 is integrated, and the A/D
This is converted distance measurement information.

Thus, according to this embodiment, diodes Q1 and Q
The sum of the voltages between the anode and cathode of 2 is the diode Q
Since it is equal to the sum of the anode-cathode voltage of transistor Q3 and the base-emitter voltage of transistor Q4, the collector current of transistor Q4 is equal to the ratio of the two current ratios, and the constant current source 7. Electrician. It is the value multiplied by

Therefore, by integrating this, distance measurement information that corresponds to the collector current and is proportional to the reciprocal of the distance can be obtained, so the current ratio can be obtained with one transistor Q4, and the measurement due to element variations can be obtained. Distance errors can be prevented.

Next, a second embodiment of the invention will be described.

FIG. 4 is a circuit diagram showing the configuration of this second embodiment. In the embodiment of FIG. 4, in place of the diodes Q1 to Q3 in FIG. 1, transistors Q1a=Q
3a is used, and the buffer 14 is omitted.

That is, the emitter of this transistor Qla is grounded, and the collector and base are commonly connected and used as a diode.

, the collector of this first transistor Qla is connected to the base of the second transistor Q2a. The emitter of this second transistor Q2a and the transistor Q4
The current output I,a of the current amplification circuit 2 is supplied to the base of the transistor Q2a, and the collector of the transistor Q2a is grounded.

Further, the base and collector of the transistor Q3a are commonly connected and grounded, and the transistor Q3a
is also used as a diode, and the current output I2a of the current amplifier circuit 3 is applied to the emitter, and logarithmic compression is performed by this transistor Q3a.

The rest of the configuration is exactly the same as that in Figure 1.
In FIG. 4, parts that are the same as those in FIG. 1 are designated by the same reference numerals, and repeated explanation of the configuration will be omitted.

In FIG. 4, as in the case of FIG. 1, the transistor Q la =Q 3a and the base of Q4 are
Find the emitter voltage VF~vF4.

vF, : Voltage between base and emitter of first transistor Qla, Vy, : Voltage between base and emitter of second transistor Q2a, vF, : Voltage between base and emitter of third transistor Q3a, vF4: Voltage between base and emitter of transistor Q4 Base-emitter voltage, Is: Reverse saturation current of an NPN transistor.

Is: Reverse saturation current of PNP transistor, Io
: Current flowing from the first constant current source 7; ■: Collector current of the fourth transistor Q4; l52 q l52 q Is□.

Here, V Fl + V F2 = V F3 + V F4
Therefore, from equations (17)2 to (2o) above, q
Is q l52q I S
2q I s yo, therefore, . Therefore, 11a=k Io, I, a=k
If L, then 2 Ω is obtained from the above equations (8), (9), and (21).

The collector power supply I4 of the fourth transistor Q4 obtained in this way is connected to an integrating circuit consisting of a comparator 10, a capacitor C1, switches SWI and SW2, and a second constant current source 11 in exactly the same way as in the case of FIG. If we perform the integration,
Pulse-like distance measurement information having a pulse width corresponding to the collector current 1 as shown in FIG. 3(e) is obtained from the output terminal of the comparator 10 as the output voltage Vout.

Thus, according to the embodiment of FIG. 4, the two current outputs 11. I2 respectively current amplifier circuit 2.3
One current output 11a after being amplified by the transistor Q
In addition to 2a and transistor Q4.

The other current output 12a is logarithmically compressed by the transistor Q3a, and the constant current function of the first constant current source 7 is performed. The transistor Ql
Logarithmically compress with a.

1st. Since the sum of the base-emitter voltages of the second transistors Qla and Q2a is equal to the sum of the base-emitter voltages of the third transistor Q3a and the base-emitter voltage of the fourth transistor Q4, the transistor The collector current I4 of Q4 is the current output I,a and I2
The ratio of a and the current from constant current source 7. This value is multiplied by , and is integrated by an integrating circuit. Therefore, by combining PNP and NPN transistors, a measurement that corresponds to the collector current of transistor Q4 and is proportional to the reciprocal of the distance can be made with a relatively simple configuration. Distance information can be obtained, and the collector current can be obtained with a single transistor stage, which has the advantage of reducing the influence of variations in elements and improving the accuracy of distance measurement.

In particular, in the case of the second embodiment, one buffer can be omitted, so the configuration can be simplified and costs can be reduced accordingly.

That is, in the case of the first embodiment shown in FIG. 1, two buffers 14 and 15 are used, but even in the simplest circuit configuration, the internal configuration of these buffers is as shown in FIG. 7. , five transistors Q15 to Q19 are required,
The cost will increase accordingly. Therefore, the second embodiment is more cost-effective than the first embodiment.

Note that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention.

〔Effect of the invention〕

As described above in detail, according to the invention of claim 1, it is possible to provide a distance detection device with a relatively simple configuration and high distance measurement accuracy, which is less affected by variations in elements.

Moreover, according to the invention of claim 2, compared to the invention of claim 1, it is possible to provide a distance detection device that has a simpler configuration and can be manufactured at a lower cost.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of a first embodiment of the distance detection device according to the present invention, FIG. 2 is a diagram explaining the principle of PSD used in the embodiment of FIG. 1, and FIG. ) to (e) are time charts for explaining the operation of the integrating circuit of the embodiment shown in FIG. 1. FIG. 4 is a circuit diagram showing the configuration of a second embodiment of the distance detection device of the present invention, FIGS. 5 and 6 are circuit diagrams showing the configuration of a conventional distance detection device, and FIG. FIG. 2 is a circuit diagram showing an example of the internal configuration of a buffer used in the distance detection device. 1...PSD, 2.3...Current amplifier circuit, 7.11...1st. Second constant current source, 10...
...Comparator, 12...LED, 13...
・Distance measurement target 14.15...Buffer, CI...Condenser, Ll...Light emitter lens, L2...Light receiving lens, Q1~Q3... ...First to third diodes, Ql
a = Q3a', Q4-1st to 3rd. Fourth transistor, SWI, SW2...switch. Mouth L; Gorge 2nd m 3rd cause

Claims (2)

[Claims] (1) Provided at a position where a reflected light spot of pulsed light irradiated from a light source onto the distance measurement target is imaged, and the position of the incident light spot is determined according to the distance of the distance measurement target based on the parallax with the light source. A first circuit that continuously detects the direction of position change due to a change in distance and has a mutual current ratio according to the detected position.
and a semiconductor optical position detector that obtains a second current output; a first diode that logarithmically compresses the current flowing from the first constant current source; and a first diode that logarithmically compresses the current flowing from the first constant current source; a second diode to which the anode-cathode voltage of the diode is applied; a third diode for logarithmically compressing the second current output; A transistor that outputs a collector current having a value obtained by multiplying the ratio of the first current output and the second current output by the current of the first constant current source by applying the voltage between the anode and cathode of the diode No. 3. and, simultaneously with the irradiation of the pulsed light to the distance measurement target, the integration of the collector current is started, and after a predetermined period of time has elapsed after the irradiation of the pulsed light has stopped, the current from the second constant current source is caused to flow into the collector. an integrating circuit that stops the integrating operation when the potential of the collector reaches a reference potential and outputs pulsed ranging information having a pulse width that corresponds to the collector current and is proportional to the reciprocal of the distance. A distance detection device characterized by: (2) Provided at a position where the reflected light spot of the pulsed light irradiated from the light source to the distance measurement target is imaged, and the position of the incident light spot is determined according to the distance of the distance measurement target based on the parallax with the light source. A first circuit that continuously detects the direction of position change due to a change in distance and has a mutual current ratio according to the detected position.
and a semiconductor optical position detector that obtains a second current output; a first transistor that logarithmically compresses the current flowing from the first constant current source; a second transistor to which a voltage between the base and emitter of the transistor is applied; a third transistor to logarithmically compress the second current output; and a third transistor to which the first current output is applied to the base and the emitter of the second transistor. By applying one voltage between the base and emitter of the transistor No. 3, a collector current of a value obtained by multiplying the ratio of the first current output and the second current output by the current of the first constant current source is generated. A fourth transistor outputs a current from a second constant current source that starts integrating the collector current at the same time as the pulsed light is irradiated to the distance measurement target, and after a predetermined time elapses after the irradiation of the pulsed light stops. An integrating circuit that flows into the collector and stops the integrating operation when the potential of the collector reaches the reference potential and outputs pulse-shaped distance measurement information that corresponds to the collector current and has a pulse width proportional to the reciprocal of the distance. A distance detection device comprising: and.