JPH06137860A - Range measuring device - Google Patents

Abstract

PURPOSE:To provide a range measuring device which is simple in circuit constitution, low in cost, and high in performance by measuring a distance to an object to be photographed, basing on the output results from an optical current signal amplifying means. CONSTITUTION:First a switch 7a is turned on and a switch 7 is turned off to amplify an optical current signal received by a photo diode 3b in a light receiving amplifier 9. Next the switch 7a is turned off and the switch 7 is turned on to amplify the optical current signal received by the photodiode 3a in the light receiving amplifier 9. Then, an A/D converter 10 makes A/D conversion of the optical current signal at a specified timing in synchronous with the infrared light emitting action, and the converted signal is input into a CPU 11. Also it is judged basing on the converted signals and by the CPU 11 which signal value is larger among optical current signals from the photo diodes 3a and 3b. Basing on the judgment results, a relative distance to an object to be photographed 14 is measured, i.e., the distance to the object to be photographed is determined.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device, more specifically,
The present invention relates to a distance measuring device that projects distance measuring light onto a subject, receives reflected signal light of the distance measuring light from the subject, and measures the distance to the subject.

[0002]

2. Description of the Related Art Conventionally, in JP-A-59-154410, an infrared light emitting diode (IR
ED) is used to project distance measuring light, which is received by a photodiode (PD) array or the like to detect the incident position of the distance measuring light and to find the distance to the subject. Has been done. This technical means, so-called active autofocus technology, is adopted in many compact cameras because of its simple structure.

However, the distance measuring light is very small, and a dedicated IC is used to accurately separate and detect the distance measuring light from background light such as sunlight illuminating the subject or artificial illumination light. I needed a circuit. Therefore, even if the autofocus technology is mounted on a low-priced camera, it is difficult to realize the cost.

FIG. 11 shows the above-mentioned Japanese Patent Laid-Open No. 59-154410.
FIG. 3 is an electric circuit diagram showing a distance measuring device proposed by the publication. In this distance measuring device, reflected light from a subject is received by photodiodes 103a and 103b, which are a plurality of light receiving elements, and the sensor unit that receives the light is switched by switches 107a and 107b such as analog switches, and the light receiving amplifier 109 is sequentially operated. It is designed to be entered. In addition, resistance 1
Reference numerals 06a and 106b are resistors for current-voltage conversion, and capacitor 108 is a capacitor for AC coupling.

FIG. 12 shows a distance measuring device proposed in Japanese Patent Application No. 4-30630, which is a technical means obtained by further improving the technical means shown in FIG. That is, the changeover switches 107a and 107b of the sensor unit to be used are replaced with resistors 106a and 106b for voltage conversion provided between the photodiodes 103a and 103b which are the sensor units and the ground.
And between the ground. In this case, the switches 107a and 107b can be easily realized by a CPU port having an open drain configuration.
The capacitors 108a and 108b are capacitors for AC coupling.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the distance measuring device proposed by Japanese Patent No. 4410, the switches 107a and 107b have to be configured by dedicated analog switches, and the cost of these switches cannot be ignored.

Further, in the distance measuring device disclosed in Japanese Patent Application No. 4-30630, two photodiodes 103 are provided.
It was necessary to completely separate a and 103b. That is, when one of the photodiodes is opened, the electric charge generated in the photodiode may appear on the output line of the other photodiode. Therefore, there is a possibility that a monolithic separation type photodiode having excellent mass productivity and small variation in characteristics cannot be used, which is an obstacle to cost reduction.

As means for solving this problem, FIG.
It is also possible to short-circuit the resistors 106a and 106b as shown in FIG. 3 to prevent voltage conversion and prevent amplification of the photocurrent signal of the unused photodiode. However, in the technical means, as shown in FIG. 14, the capacitor 108b forms a circuit for smoothing the input signal before the input to the light receiving amplifier 109, so that the photocurrent signal of which the resistor is not short-circuited is eventually sufficient. It cannot be amplified to.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a high-performance distance measuring device having a simple circuit configuration and a low price.

[0010]

To achieve the above object, a distance measuring device according to the present invention comprises a distance measuring light projecting means for projecting distance measuring light to a subject, and A plurality of light receiving means for receiving the reflected signal light of the distance measuring light and converting it into a photocurrent signal and a photocurrent signal output from the plurality of light receiving means are selectively operated without blocking any signal output. A photocurrent signal switching means for switching to and outputting the photocurrent signal, and a photocurrent signal amplifying means for amplifying the photocurrent signal output from the light receiving means selectively switched by the photocurrent signal switching means,
An arithmetic control unit that determines the distance to the subject based on the output result from the photocurrent signal amplifying unit is provided.

[0011]

According to the present invention, the distance measuring light projecting means projects the distance measuring light on the object, and the plurality of light receiving means receives the reflected signal light of the distance measuring light from the object. And convert it into a photocurrent signal. Then, the photocurrent signal switching means outputs the photocurrent signal output from the plurality of light receiving means by selectively switching without outputting any signal output, and the photocurrent signal amplifying means outputs the photocurrent signal. The photocurrent signal output from the light receiving means selectively switched by the switching means is amplified. Then, the arithmetic control means determines the distance to the subject based on the output result from the photocurrent signal amplification means.

[0012]

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

FIG. 1 is an electric circuit block diagram showing the configuration of a distance measuring apparatus according to a first embodiment of the present invention.

In the first embodiment, a light emitting diode 1 (IRED1) and an IRED for projecting infrared light to a subject under the control of a timing signal sent from a CPU 11 which controls the whole distance measuring apparatus. A driver 2 and a reflected light of the infrared light, which is formed in an array and is received from the subject, and converts the infrared light into a photocurrent signal according to the amount of the reflected light 2
Two photodiodes (PD) 3a and 3b, diodes 5a and 5b connected in series with the photodiodes 3a and 3b and having cathodes connected to each other, and connected in parallel to the photodiodes 3a and 3b, respectively. Bias resistors 4a and 4b for applying a bias voltage to the diodes 5a and 5b, and the diodes 5a and 5b
b connected to the common cathode, and the bias resistors 4a,
A voltage conversion resistor 6 for converting a bias current from 4b into a bias voltage, and switches 7a, 7 connected between the respective anodes of the diodes 5a, 5b and the ground.
b and the photodiode 3 which is connected to the common cathode of the diodes 5a and 5b and is a pulsed signal.
a high-pass filter capacitor 8 for removing stationary components other than the photocurrent signal from the output signals from a and 3b;
Light receiving amplifier 9 for amplifying the output signal from the capacitor 8.
And the output signal from the light receiving amplifier 9 is A / D converted to C
The A / D converter 10 input to the PU 11 and the IR
It controls the projection of ED1 and also switches 7a, 7
The main part is constituted by the CPU 11 which controls the on / off of b.

The above IRED 1 and photodiode 3
a and 3b are arranged based on the principle of triangulation as shown in FIG.

That is, the infrared light projected from the IRED 1 is focused on the subject 14 through the light projecting lens 12, and the reflected light from the subject 14 is reflected by the projecting lens 12 described above.
By the light receiving lens 13 which is separated from the light receiving lens 13 by a distance S from, the light is collected by the photodiodes 3a and 3b in an array shape arranged at a distance f from the light receiving lens 13.

By the way, in this embodiment, the reflected light from the subject 14a at a relatively short distance L1 is reflected by the photodiode 3a, and the reflected light from the subject 14b at a relatively long distance L2 is reflected by the photodiode. The photodiodes 3a and 3b arrays are arranged so that light is received by 3b. Therefore, it is possible to know the relative distance to the subject 14 by determining which one of the photodiodes 3a and 3b the reflected light from the subject 14 is incident on.

In this embodiment, the photodiodes 3a, 3a
b is connected in series with diodes 5a and 5b, and the anode side of each of the diodes 5a and 5b is connected to a switch 7a,
The function of the photodiodes 3a and 3b as a light receiving sensor is switched by switching between "H" level and "L" level by turning on / off 7b. That is, the CPU
When the switch 7a is turned on and the switch 7b is turned off by the control of 11, the photocurrent signal generated by the photodiode 3a cannot flow into the voltage conversion resistor 6, and thus the light generated by the photodiode 3b is not generated. Only the current signal is amplified by the light receiving amplifier 9 and thereafter. On the contrary, the switch 7a is turned off and the switch 7b is turned on.
When is turned on, the photocurrent signal generated by the photodiode 3b cannot flow into the voltage conversion resistor 6,
Therefore, only the photocurrent signal generated by the photodiode 3a is amplified by the light receiving amplifier 9 and thereafter.

The diodes 5a and 5b are connected to the switch 7
It is provided so that the turning on of one of the switches a and 7b does not affect the signal amplification from the photodiode connected to the other switch. By the way, generally, a diode has a parasitic capacitance and the like, and when a bias current does not flow, it takes time to charge the parasitic capacitance and the like, and the response of the signal current deteriorates. In this embodiment, bias resistors 4a and 4b are provided in parallel with the photodiodes 3a and 3b.
The bias current always flows through the diodes 5a and 5b via a and 4b to solve the above-mentioned problems.

The operation of this embodiment having such a configuration will be described with reference to the time chart shown in FIG.

Under the control of the CPU 11, the switches 7a and 7
Infrared light is projected from the IRED 1 toward the subject 14 by switching on and off of b. In this embodiment, first, the switch 7a is turned on, the switch 7b is turned off, and the photocurrent signal received by the photodiode 3b is amplified by the light receiving amplifier 9, and then the switch 7a is turned off and the switch 7b is turned on. The photocurrent signal received by the diode 3a is amplified by the light receiving amplifier 9. Then, in synchronization with the infrared light projection operation, the A / D converter 10 A / D-converts the photocurrent signal at the timing shown, and the A / D-converted signal is input to the CPU 11. The CPU 11 determines which of the photocurrent signals from the photodiodes 3a and 3b is larger than the A / D converted signal, and determines the relative distance to the subject 14 based on the determination result. That is, the distance of the subject is determined.
In the case shown in FIG. 3, since more photocurrent signals are generated in the photodiode 3a, the subject 1
It can be seen that the distance to 4 is a relatively short distance.

According to the first embodiment, the photodiodes 3a and 3b are provided with the diodes 5a and 5b in series, and the photodiodes 3a and 3b, which are the sensor section, are switched, and a set of the light receiving amplifier 9 and the A / D converter. Since 10 is used, it is possible to reduce the cost by disposing a minimum number of processing circuits such as an amplifier for a photocurrent signal and an A / D converter, which requires a large cost in a discrete circuit. It will be possible. Further, bias resistors 4a and 4b are provided in parallel with the photodiodes 3a and 3b, and the diode 5 is connected via the bias resistors 4a and 4b.
Since the bias current always flows through a and 5b,
It is possible to obtain a photocurrent signal output with good response without being affected by parasitic capacitance or the like.

FIG. 4 is an electric circuit diagram showing the configuration of the distance measuring device according to the second embodiment of the present invention.

In the second embodiment, the switches for controlling grounding and open shown as the switches 7a and 7b in the configuration of the first embodiment are replaced by the open drain output port of the CPU 11. In addition, from the two-divided photodiodes 3a and 3b to the AC coupling capacitor
The circuit configuration up to this point is the same as that of the first embodiment.

The CPU 11 in this embodiment has output ports of several open drain configurations, and FET4
The output ports P1 and P2 of 0 and 41 are connected to the anodes of the diodes 5a and 5b, respectively, and have the same functions as the switches 7a and 7b in the first embodiment.

In this embodiment, the light receiving amplifier 9 is a C-MOS.
It is configured by a known linear amplifier including an inverter 9a and a feedback resistor 9b. Occurred in the voltage conversion resistor 6,
The photocurrent signal, which is an AC voltage, is set to 1 by the light receiving amplifier 9.
It is designed to be amplified about 00 times.

The NPN transistor 24 is a transistor for converting the AC voltage amplified by the light receiving amplifier 9 into a current, the bias point of which is set by the emitter resistor 25, and the grounded emitter amplifier circuit for the AC signal by the capacitor 26. As a result, the output of the light receiving amplifier 9 is amplified and converted into a collector current.

The PNP transistors 22 and 23 are composed of elements paired with each other to form a known current mirror circuit, and the emitter resistors 20 and 21 are respectively formed.
The power supply voltage Vcc is applied via the. The collector current of the transistor 24 is caused to flow to the integrating capacitor 27 at a predetermined timing described later.

Since the collector current is a current signal that fluctuates in an alternating current, if the integration is always performed, the plus side amplitude and the minus side amplitude of the signal cancel each other out and the amplitude becomes zero. Therefore, synchronous integration by timing control is required. In this embodiment, the emitter terminal of the transistor 23 of the current mirror circuit is connected to the output port P4 of the CPU 11 in order to control the emitter potential of the transistor 23.
The collector current of the transistor 24 flowing in the transistor 23 is turned on / off under the control of 11.

That is, the output port P4 is FET4
Since the open drain configuration by 3 is adopted, the FET4
When 3 is opened, the integration capacitor 27 performs integration, and when it is set to "L" level, the transistor 23 is integrated.
Is turned off, the integration can be prohibited.

The positive side of the integrating capacitor 27 is CP.
It is connected to the output port P3 of U11 to switch between ground and open, and it is possible to discharge the integrated charge by the ground. The output port P3 is an input / output port that has an open drain configuration with the FET 42 and forms an input port with the Schmitt trigger 44. Then, the integrated voltage of the integrating capacitor 27 is determined by the threshold value Vcc / 2. Therefore, it can be said that the integrating circuit formed of the current mirror circuit has the same function as that of the A / D converter 10 in the first embodiment.

The CPU 11 further includes an output port P
5 is provided and is equivalent to the first embodiment described above.
It is connected to the IRED 1 via the driver 2. The IRED1 is intermittently oscillated and emitted by a timing signal from the output port P5, and the emitter potential of the transistor 23 is controlled from the output port P4 in synchronization with this, so that the integrated voltage can be obtained by the number of times of light emission / integration. Is Vcc
It is possible for the CPU 11 to determine whether the value exceeds / 2. That is, the determination can be made by converting the analog amount of the photocurrent signal into the number of integrations that is a digital value.

Next, the integration operation in the second embodiment will be described with reference to the time chart shown in FIG.

In this embodiment, IRED1 has a duty of 5
It emits light intermittently at 0%. First, when the output port P1 is opened and the output port P2 is set to "L" level, the photocurrent signal from the photodiode 3a flows through the diode 5a and is converted into a voltage by the voltage conversion resistor 6. This signal output is amplified by the light receiving amplifier 9 via the AC coupling capacitor 8 and converted into a current by the transistor 24. Then, a current equivalent to the collector current of the transistor 24 is applied to the transistors 22 and 23.
Integrating capacitor 27
Is flowed to and integrated. The integration capacitor 27 is initialized by a reset signal from the output port P3 prior to the integration operation.

Then, the output port P2 is opened and the output port P1 is set to the "L" level to make the photodiode 3b.
The photocurrent signal from is amplified, and the integration operation is performed as described above.

On the other hand, the above IRED is output from the output port P4.
A control signal synchronized with the light emission of 1 is output, and the output voltage Vout of the light receiving amplifier 9 is integrated at the timing of this control signal. Since this integration operation is performed at the timing when the photocurrent signal, which is an AC signal, reaches a peak, the integration amount increases as the output voltage Vout increases, that is, the photocurrent signal output increases.

Therefore, the number of integrations until the integrated value of the integrating capacitor 27 (shown as integration in the figure) reaches the threshold value Vcc / 2 depends on the signal amount of the photocurrent signal output, and the larger the signal amount is, the larger the signal amount is. The number of integrations is reduced.

Now, the number of integrations based on the photocurrent signal output from the photodiodes 3a and 3b is set to na and nb, respectively.
As an example, the operation of determining the relative distance to the subject in this embodiment will be described with reference to the flowchart shown in FIG.

First, the integrated value of the integrating capacitor 27 by the photocurrent signal from the photodiode 3a is the threshold value Vc.
The number of times of integration na is counted until it exceeds c / 2 (steps S1 and S2), and after reaching the threshold value, the integration value of the integrating capacitor 27 by the photocurrent signal from the photodiode 3b is the threshold value Vcc /. The number of integration times nb is counted until it exceeds 2 (step S3, step S3).
4). Next, the integration times na and nb are compared (step S5). As described above, the photodiode that receives a large amount of reflected light from the subject has a smaller number of integrations. Therefore, when the number of integrations na <nb, it can be determined that the subject is a relatively short distance (step S
6) On the other hand, when the number of integrations na> nb, it can be determined that the subject is relatively far (step S7).

In the case shown in FIG. 5, the number of integrations na
Since <nb, it can be seen that the distance to the subject at this time is relatively short.

It goes without saying that the second embodiment can also achieve the same effects as those of the first embodiment.

In the first and second embodiments, the CPU 11 has been shown to control the integration and determination operations of the distance measuring device, but the control operation of the CPU 11 is not limited to this, and the control operation of the distance measuring operation is not limited to this. Thereafter, the focusing operation of the camera may be controlled based on the result of the distance measurement.

FIG. 7 is an electric circuit diagram showing the main part of the distance measuring apparatus according to the third embodiment of the present invention. In the figure, the portions denoted by the same reference numerals as those in the first and second embodiments have the same actions and effects, and therefore the processing circuits after the light receiving amplifier 9 are the same as those in the first and second embodiments. Since this is exactly the same as the example, the description is omitted here.

In the third embodiment, the constant current source 30 is PN.
Two PNP transistors 28a and 28b, which are connected to the collector of the P-transistor 29 and further form a current mirror circuit with the base common to the transistor 29.
, And the collectors thereof are connected to the anodes of the diodes 5a and 5b. As a result, it becomes possible to pass the bias current to the diodes 5a and 5b for separating the photocurrent signal output without affecting each other.

According to the third embodiment, the power supply voltage Vcc
Of the diodes 5a, 5b without being affected by fluctuations in
It is possible to stably supply the bias current flowing in the. Further, the bias resistors 4a and 4b provided in the first and second embodiments can be omitted.

FIG. 8 is an electric circuit diagram showing the main part of the distance measuring apparatus according to the fourth embodiment of the present invention. Note that, in the drawing, the portions denoted by the same reference numerals as those of the first and second embodiments have the same actions and effects, and thus the description thereof will be omitted here.

In the first to third embodiments, the photocurrent signal output of the photodiodes 3a and 3b was converted from current to voltage by the voltage converting resistor 6, but this fourth embodiment
The embodiment is characterized in that the photodiodes 3a and 3b amplify the photocurrent signal output in the state of the current signal.

That is, the above-described characteristics are realized by replacing the light receiving amplifier 9 section in the first to third embodiments with the operational amplifier 31. By turning on / off the switches 7a and 7b, the photocurrent signal output from the photodiodes 3a and 3b is flown into the operational amplifier 31 and the current amplifying transistor 32, and the photocurrent signal output to be amplified is switched. . The operation of the operational amplifier 31 causes the photodiode 3a or the photodiode 3 to operate.
The photocurrent signal output current from b is flown into the base of the transistor 32 with a low input impedance, and the current is amplified by the transistor 32 by an amplification factor β. The amplified photocurrent signal output is integrated by the integrating capacitor 27 via the current mirror circuit composed of the transistors 22 and 23 as in the second embodiment. The reference voltage Vref is applied to the positive input of the operational amplifier 31.

According to the fourth embodiment, the above first to third
Although the operational amplifier 31 is newly required as compared with the embodiment, it is possible to provide a distance measuring device having an excellent S / N ratio by not repeating the current-voltage conversion.

The voltage conversion resistor 6 for voltage conversion is also used.
Since the resistance is not provided, it is possible to prevent the power supply voltage Vcc from being lowered by this resistance, and the photodiodes 3a and 3b can be prevented.
The power supply voltage Vcc can be set without largely depending on the reflected light input to the. That is, it becomes possible to operate at a lower power supply voltage Vcc.

FIG. 9 is an electric circuit diagram showing the main part of the distance measuring apparatus according to the fifth embodiment of the present invention. In the figure, the portions denoted by the same reference numerals as those in the first to fourth embodiments have the same actions and effects, and therefore the processing circuits after the light receiving amplifier 9 are the same as those in the first to third embodiments. Since this is exactly the same as the example, the description is omitted here.

In the fifth embodiment, the diodes 5a and 5b in the first to fourth embodiments are respectively connected to the collector-
NPN transistors 5a 'and 5 with shorted bases
b ′, and a current mirror circuit is formed by the transistors 5a ′, 5b ′ and the transistors 40a, 40b having the same characteristics.
A collector resistor 6'is provided between the common collector of a and 40b and the power supply voltage Vcc.

In this fifth embodiment, the photodiode 3
The photocurrent signal output from a and 3b is the transistor 40
The collector resistance 6'as the collector current of a and 40b.
Therefore, it is possible to cope with a low voltage as compared with the first to third embodiments.

Further, the switching operation of the photodiodes 3a and 3b is controlled by turning on / off the switches 7a and 7b similarly to the above-mentioned embodiment, and when the switches 7a and 7b are turned on respectively, the transistor corresponding to this is turned on. Four
0a and 40 are turned off, and the photocurrent signal output from the photodiodes 3a and 3b does not flow into the collector resistor 6 '.

FIG. 10 is an electric circuit diagram showing the main part of the distance measuring apparatus according to the sixth embodiment of the present invention. Note that, in the drawing, the portions denoted by the same reference numerals as those of the first to fifth embodiments have the same actions and effects, and therefore the description thereof is omitted here.

The sixth embodiment is a one-chip microcomputer C for sequence control of the fifth embodiment.
It is characterized in that it is configured on the same chip as the PU 11 (see FIG. 1) (this makes it a CPU 11 ').

Since the CPU 11 and the CPU 11 are formed on the same chip, all of the bipolar transistors in the above embodiment are replaced with MOS transistors.

The CPU 11 'need only prepare the photodiodes 3a and 3b, the capacitor 8, the integrating capacitor, and the IRED1 and IRED driver 2 as external parts, and all the other elements and the like in the fifth embodiment are the CPU. It is configured on the same chip.

For example, in this embodiment, the bias resistor 4
a, 4b and the resistor 6'feedback resistor 9b are composed of pinch resistors or ion implantation resistors of the C-MOS process,
Further, the switches 7a and 7b, the integration capacitor reset switch 52 and the like are N-MOS type transistors, and the switch 5 for switching between short-circuiting with the power supply voltage Vcc and opening.
Reference numerals 0 and 53 are P-MOS type transistors. Further, the linear amplifier 9a is composed of a well-known C-MOS type inverter, and the output of TR of the transistor 54 composed of an N-MOS type transistor is converted into a current signal. The P-MOS transistors 22 and 23 composed of P-MOS type transistors are MOS.
Form a current mirror circuit with a transistor
When the -MOS transistor 53 is turned on, the drain current of the P-MOS transistor 23 is turned off, so that synchronous integration becomes possible.

Further, in the figure, reference numeral 51 is a CPU core portion in the CPU 11 ', which is M in accordance with a predetermined sequence.
On / off control of the OS transistors 7a, 7b, 50, 52, 53 and the like is performed.

The circuit newly added on the chip of the CPU in the sixth embodiment is extremely small compared to the ratio of the CPU itself, and the increase in cost due to this addition is small. On the other hand, the cost reduction of the parts built in the chip of the CPU is extremely large, and the total cost can be significantly reduced. Furthermore, the reduction in the number of parts leads to a reduction in the number of assembling steps at the time of manufacturing and an improvement in the reliability of the entire camera.

In each of the above-described embodiments, an example in which two photodiodes are provided as the light receiving means for receiving the reflected light of the subject is shown, but the number is not limited to two, and the reflected light of the subject is received. It is needless to say that it is possible to provide a plurality of photodiodes to be used and to set the relative distance to the subject to be determined more finely.

[0063]

As described above, according to the present invention, it is possible to provide a high-performance distance measuring device having a simple circuit structure and a low price.

[Brief description of drawings]

FIG. 1 is an electric circuit block diagram showing a configuration of a distance measuring device according to a first embodiment of the present invention.

FIG. 2 is a principle diagram of triangulation showing a relationship between an IRED and a photodiode in the first embodiment.

FIG. 3 is a time chart showing the operation of the first embodiment.

FIG. 4 is an electric circuit diagram showing a configuration of a distance measuring device according to a second embodiment of the present invention.

FIG. 5 is a time chart showing the integration operation of the second embodiment.

FIG. 6 is a flowchart showing the determination operation of the second embodiment.

FIG. 7 is an electric circuit diagram showing a configuration of a distance measuring device that is a third embodiment of the present invention.

FIG. 8 is an electric circuit diagram showing a configuration of a distance measuring device according to a fourth embodiment of the present invention.

FIG. 9 is an electric circuit diagram showing a configuration of a distance measuring device that is a fifth embodiment of the present invention.

FIG. 10 is an electric circuit diagram showing a configuration of a distance measuring device according to a sixth embodiment of the present invention.

FIG. 11 is an electric circuit diagram showing an example of a conventional distance measuring device.

FIG. 12 is an electric circuit diagram showing another example of a conventional distance measuring device.

FIG. 13 is an electric circuit diagram showing another example of a conventional distance measuring device.

FIG. 14 is an equivalent circuit diagram illustrating a problem in the distance measuring device of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... IRED 2 ... IRED driver 3a, 3b ... Photodiode 4a, 4b ... Bias resistance 5a, 5b ... Diode 6 ... Voltage conversion resistance 7a, 7b ... Switch 8 ... AC coupling capacitor 9 ... Photosensitive amplifier 10 ... A / D Converter 11 ... CPU

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[Procedure amendment]

[Submission date] December 2, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

FIG. 11 shows the above-mentioned Japanese Patent Laid-Open No. 59-154410.
Analog switch similar to the circuit proposed by the publication
It is an example of an electric circuit in which the sensor is switched by using. In this distance measuring device, reflected light from a subject is received by photodiodes 103a and 103b, which are a plurality of light receiving elements, and a sensor unit for receiving the received light is a switch 1 such as an analog switch.
07a and 107b are switched to sequentially input to the light receiving amplifier 109. The resistors 106a,
106b is a resistor for current-voltage conversion, and the capacitor 108 is a capacitor for AC coupling.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the range finder proposed by Japanese Patent No. 4410, the switches 107a and 107b must be composed of dedicated analog switches, and the cost of these switches cannot be ignored .
won.

[Procedure 3]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 10

[Correction method] Change

[Correction content]

[Figure 10]

Claims (3)

[Claims] 1. A range-finding light projecting means for projecting range-finding light to an object, and a plurality of units for receiving reflected signal light of the range-finding light from the object and converting it into a photocurrent signal. A light receiving means, a photocurrent signal switching means for selectively switching the photocurrent signal output from the plurality of light receiving means without interrupting any signal output, and selecting by the photocurrent signal switching means. Photocurrent signal amplification means for amplifying the photocurrent signal output from the light receiving means that has been switched, and calculation control means for determining the distance to the subject based on the output result from the photocurrent signal amplification means. A distance measuring device characterized in that 2. The photocurrent signal switching means comprises a bias circuit for connecting a diode in series to the light receiving means and applying a current bias to the diode, and an anode potential control means for controlling an anode potential of the diode. The distance measuring device according to claim 1, further comprising: 3. The distance measuring apparatus according to claim 1, wherein the photocurrent signal switching means is formed on the same substrate as the arithmetic control means.