JP3193481B2 - Distance measuring device - Google Patents

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,
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, a distance measuring light is projected from a camera using an infrared light emitting diode (IRED) or the like, and the light is received by a photodiode (PD) or the like to determine the incident position of the distance measuring light. Technical means to detect and determine the distance to the subject,
The so-called active autofocus technology is widely used in compact cameras and the like because of its simple configuration.

However, the distance measuring light is minute, and a dedicated IC is required to accurately separate the distance measuring light from background light such as sunlight or artificial illumination light illuminating the subject. Circuit was needed. Therefore, it has been difficult to implement the autofocus technology in a low-cost camera in terms of cost.

Incidentally, an AC amplifier circuit is often used as a means for separating the distance measuring light and the background light. That is, while much background light fluctuates at a low frequency, if the signal light is projected with a high frequency pulse, only the signal light can be easily amplified by a capacitor coupling or the like.

In general, a signal light is a minute photocurrent signal on the order of nanoamperes. Therefore, an amplification means for the signal light is required before performing an operation such as integration. In addition, since the signal light is very small even after amplification, a high resolution can be obtained by performing an integration operation also for smoothing random noise which is easily mixed into the signal light. further,
As described above, since the signal light fluctuates in an AC manner, the integration operation needs to perform synchronous integration in synchronization with the projection of the IRED. FIG. 15 shows a conventional operation using an operational amplifier fed back with a capacitor. FIG. 2 is an electric circuit diagram showing an example of a distance measuring device.

In this distance measuring device, a photocurrent signal from a light receiving means (not shown) is amplified by a light receiving amplifier 106, and an output voltage VOUT of the light receiving amplifier 106 is connected to a switch 120 and a resistor 121.
Operational amplifier 1 having feedback capacitor 122 through
23. When the switch 120 is turned on and off, synchronous integration becomes possible. The output voltage VOUT and the reference voltage V input to the other terminal of the operational amplifier 123 are output.
ref is converted into a current by a resistor 121 and flows into an integrating capacitor 122, whereby the operational amplifier 1
23, an integrated voltage is generated at the output.

On the other hand, the present applicant has proposed in Japanese Patent Application No. Hei 4-30630 a distance measuring apparatus employing an integrating circuit shown in FIG.

As shown in FIG. 1, the integrating circuit controls the emitter potential of a known current mirror circuit using PNP transistors 125 and 128 having emitter resistors 126 and 127, respectively, by a switch 130, so that an integrating capacitor 129 is provided. Synchronous integration is performed.

When this integrating circuit is connected to a light-receiving amplifier that outputs an AC voltage VOUT, the integrated current I becomes I = (Vcc- (VOUT + VBi) -0.6) / R. VBi is the light receiving amplifier 10 when there is no signal.
6 is the output voltage.

That is, the AC voltage VOUT is simply converted into a current by the resistor R. For example, if the AC voltage VOUT is 18 mV and the resistance R is 1Ω, the signal current is 18 μA
Becomes

[0011]

However, in the conventional distance measuring apparatus as shown in FIG. 15, a complicated circuit such as an operational amplifier and a dedicated reset circuit 124 for initializing the integrating capacitor 122 are provided. Need and
It costs a lot of money.

In the integrating circuit proposed in Japanese Patent Application No. 4-30630, for example, an AC voltage VOUT
= 0 and VBi = 1V and Vcc = 2V,
There is a problem that a considerable bias current of 0.4 V / 1 kΩ = 400 μA flows. If the bias of the signal light is more than 20 times, it is considered that it is difficult to separate the non-signal state and the signal input state. Therefore, in this proposal, another grounded emitter amplifier is provided between the integrator and the amplifier. And there was a problem in terms of cost.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a distance measuring apparatus having a simple configuration, a low price, and a high performance autofocus function.

[0014]

In order to achieve the above object, a first distance measuring apparatus according to the present invention measures a subject with respect to a subject.
Distance measuring light projecting means for projecting distance light, and
Received reflected signal light of distance measuring light and depended on received light quantity
Light receiving means for outputting a photocurrent signal; a differential amplifier;
An integration capacitor connected to the output of the amplifier.
Integrates a signal that depends on the photocurrent signal output from the light receiving means
Photocurrent signal integrating means to perform
To determine the distance to the subject based on the output
Calculation control means, and the photocurrent signal integration means,
Of the differential transistors that make up the differential amplifier,
Differential output to which the photocurrent signal output from the
The integration operation can be performed by controlling the base potential of the transistor.
And features. In order to achieve the above object, the present invention
The second distance measuring device emits distance measuring light to the subject
Distance measuring light projecting means, and the distance measuring light
Receives reflected signal light and generates a photocurrent signal depending on the amount of received light.
Light receiving means for outputting, a differential amplifier, and an output of the differential amplifier
And an integrating capacitor connected to the end,
Photocurrent signal that integrates the signal that depends on the photocurrent signal output
Signal integration means and the output result from the photocurrent signal integration means
Calculation control means for determining the distance to the subject based on
Wherein the photocurrent signal integrating means comprises a differential amplifier.
The common emitter potential of the differential transistors that make up the
In this case, the integration operation is performed.

[0015]

In the present invention, the distance measuring light projecting means emits the distance measuring light to the object, and the light receiving means receives the reflected signal light of the distance measuring light from the object. After outputting the photocurrent signal dependent on the amount of received light, the photocurrent signal integrating means integrates the signal dependent on the output of the photocurrent signal from the light receiving means. Then, the arithmetic control unit determines the distance to the subject based on the output result from the photocurrent signal integration unit.

[0016]

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

FIG. 1 is an electric circuit block diagram showing a 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) for projecting infrared light to a subject (not shown) under the control of a timing signal sent from a CPU 13 for controlling the entire distance measuring apparatus. And an IRED driver 5, a light projecting lens 2 for converging infrared light projected from the IRED 1 onto a subject, and a light receiving lens 2 formed in an array to receive reflected light of the infrared light from the subject. A photodiode 4 for converting the reflected light into a photocurrent signal corresponding to the amount of the reflected light;
A light receiving lens 3 for condensing reflected light from the object on the photodiode, a light receiving amplifier 6 for converting and amplifying a photocurrent signal from the photodiode 4 to a voltage, and an output of the light receiving amplifier 6 A differential amplifier circuit including differential transistors 8 and 9 for differentially amplifying a signal, an integrating capacitor 10 connected to the collector of the differential transistor 9, and a base-power supply voltage Vc of the differential transistor 9
c, a resistor 12 and a switch 1 connected between the base and ground of the differential transistor 9.
The main part is composed of a series circuit composed of a CPU 4 and a CPU 13 that controls the light emission of the IRED 1 and controls the on / off of the switch 14 and the integration of the integrating capacitor 10.

The present embodiment is characterized in that a differential amplifier circuit is connected to the output of the light receiving amplifier 6, and synchronous integration can be performed by simple control. For example,
In the integrating circuit shown in FIG. 15, it is necessary to use an analog switch as the switch 120, but in the present embodiment, the integrating operation can be performed by controlling only the ground or the open state. That is, the switch 14 may use an open drain output port of the CPU 13.

The differential transistors 8 and 9 constituting the differential amplifier circuit are PNP transistors having good pairing properties, and are connected to the power supply voltage Vcc via the resistor 7.
The base of the differential transistor 8 is connected to the output terminal of the light receiving amplifier 6, and the collector is grounded. The base of the differential transistor 9 includes the resistor 11 and the resistor 1 as described above.
2 and the collector of the differential transistor 9 is connected to the integrating capacitor 10.

When the switch 14 is turned on under the control of the CPU 13, the power supply voltage Vcc is divided by the resistors 11 and 12, and an appropriate potential is applied to the base of the differential transistor 9. When the switch 14 is turned off, it is pulled up to the resistor 11 and the base potential of the differential transistor 9 becomes "H" level.
The current supply to the power supply is cut off.

FIG. 2 is a time chart showing the relationship between the light emission of the IRED 1 and the integration state of the integration capacitor 10.

When the IRED 1 is periodically turned on and off as shown in the figure, the amplified signal of the photocurrent signal output appearing at the output terminal of the light receiving amplifier 6 becomes an AC signal having an amplitude VOUT centered on the bias point VBi. Therefore, if the integration operation by the integration capacitor 10 is performed over the entire region, the plus side and the minus side of the bias point VBi cancel each other, and the bias point VBi is eventually integrated. Therefore, it is necessary to perform integration periodically at the timing shown in the figure as described above.

By the way, in the integration circuit shown in FIG. 16, the integration voltage VINT per one integration is VINT = {Vcc- (VOUT + VBi) -0.6}. In this embodiment, since the differential amplifier circuit is employed, the integrated voltage VINT is given by the following equation.

VINT = {tINT · I0 · (exp (VOUT / VT))} / {(exp (VOUT / VT) +1) · CINT} where I0 is the current flowing through the resistor 7 and the differential transistor 9 Is adjusted by the resistors 11 and 12 to be the voltage VBi.

According to the above equation, the amplified signal voltage VOUT is the voltage V
It has nothing to do with Bi. For example, if the amplified signal voltage VOUT is 18 mV, the integrated voltage VINT becomes VINT = (2/3) · (tINT · I0 / CINT), but when there is no signal, VINT = (1/2 ) · (TINT · I0 / CINT), so that the difference appears clearly.

In the conventional integrating circuit shown in FIG. 16, the difference was about 20:21, so that it was difficult to make a distinction. However, according to the present embodiment, the bias level of the light receiving amplifier is reduced. It is possible to realize an integration circuit with high sensitivity without dependency and easy integration with a simple configuration.
A high-performance, low-cost distance measuring device can be provided.

FIG. 3 is an electric circuit diagram showing a configuration of a distance measuring apparatus according to a second embodiment of the present invention.

The second embodiment has a configuration basically similar to that of the first embodiment, and has an integration circuit similar to that of the first embodiment.

In the second embodiment, a photodiode 4 is used as a light receiving element for an autofocus signal.
The photocurrent signal from the photodiode 4 is converted into a voltage signal by the resistor 31. Since this photocurrent signal includes natural light for illuminating the subject, the output terminal of the photodiode 4 is connected to a capacitor 32 in order to separate and amplify only the signal light that fluctuates in an alternating manner.
Is connected to an input terminal of a known linear amplifier composed of a feedback resistor 33 and an inverter 34.

The output of the linear amplifier (hereinafter, referred to as a first linear amplifier) has a power supply voltage Vcc of 1 when there is no signal.
Although it is stable at a potential of / 2, when a signal is input in an alternating manner, the input voltage can be amplified up to about 40 dB by amplitude around the potential.

The circuit including the resistor 7, the differential transistors 8, 9 and the integrating capacitor 10 is an integrating circuit using a differential amplifier circuit similar to the first embodiment. The output of the amplifier by the first linear amplifier is input to one base (base of the differential transistor 8) of the differential amplifier circuit. Further, unlike the first embodiment, a second linear amplifier including an inverter 35 and a feedback resistor 36 is connected to the other base (base of the differential transistor 9) of the differential amplifier circuit.

No signal is input to the second linear amplifier, and in order to generate a potential equal to the non-input voltage of the first linear amplifier, similarly to the resistors 11 and 12 in the first embodiment. Used.

In the first embodiment, when the switch 14 is turned off, the base potential of the differential transistor 9 is pulled up by the resistor 11, the differential transistor 9 is turned off, and the current flowing to the integrating capacitor 10 is cut off. However, in the second embodiment, the open drain transistor 39 in the CPU 13 is turned on, and the inverter 3 is turned on.
5 is set to "L" level, whereby the output of the inverter 35 is set to "H" level, and the differential transistor 9
Is turned off.

When the output port 39 is opened, the same voltage as in the non-input state of the first linear amplifier is generated as described above.
9, the value of the current flowing through the integrating capacitor 10 can be changed in accordance with the difference in the base potentials, that is, according to the magnitude of the signal voltage.

Further, the integration capacitor 10 is connected to an input / output port to which an open-drain transistor 37 and a Schmitt trigger inverter 38 are connected. When the transistor 37 is turned on, initialization is performed. It has become. Further, since the inverter 38 is inverted when the integrated voltage becomes Vcc / 2, the arithmetic control unit 40 of the CPU 13 determines from the inversion timing that the integrated voltage of the integrating capacitor 10 becomes Vcc / 2.
Can be determined.

In the figure, reference numeral 1 denotes an IRED, and reference numeral 5 denotes an IRED driver circuit including NPN transistors and the like. The CPU 13 performs these drive control and the timing control of each of the above-mentioned ports and the like.
The result of distance measurement is determined from the number of integrations until c / 2.

FIG. 4 is a time chart showing the integration operation in the second embodiment.

In the second embodiment, the relative distance to the subject is determined from the difference between the number of integrations when the light emission of the IRED 1 is performed and when the light emission is not performed. Further, prior to the integration operation, the transistor 37 is turned on to initialize the integration capacitor 10.

The timing of the light emission of the IRED 1 and the timing of the integration signal are assumed to be the same as those in the first embodiment.

As shown in FIG. 4, the number of integrations is Vcc
The CPU 13 counts the number of integrations to reach / 2. Assuming that the integration number at the time of light emission of the IRED 1 is n and the integration number at the time of no light emission is n0, the potential of the base of the differential transistor 8 fluctuates with respect to VBi at the time of light emission. When the synchronous integration is performed at such timing, the current flowing into the integration capacitor 10 changes according to the magnitude of the difference voltage VOUT from VBi. In the first embodiment, since the base potential of the differential transistor 8 is higher than the base potential of the differential transistor 9, the number of signals flowing into the integrating capacitor 10 is larger than when there is no signal. Therefore, the number of times of integration until reaching the predetermined integration voltage is smaller than when there is no signal.

FIG. 5 is a flowchart showing the operation of determining the subject distance in the second embodiment.

If the distance measuring light projected by the IRED 1 is reflected and received by the photodiode 4, it is determined that the distance to the subject is relatively short. If the reflected light is not detected, the distance to the subject is determined. The subject is determined to be at a long distance.

First, the IRED 1 is caused to emit light, and the number of integrations n is counted until the integrated value of the integrating capacitor 10 by the photocurrent signal from the photodiode 4 exceeds the threshold value Vcc / 2 (steps S1 and S2). After reaching the threshold value, the number of integrations n0 is counted until the integrated value of the integration capacitor 10 exceeds the threshold value Vcc / 2 without causing the IRED 1 to emit light (steps S3 and S4). Next, the number of integrations n and n0 are compared (step S5).

Here, assuming that both the integration times n and n0 have variations due to noise or the like, the margin value α
Is compared in consideration of the above (Step S
5). If the distance to the subject is short, the number of integrations n is sufficiently smaller than the number of integrations n0. Therefore, if the number of integrations n <n0−α in step S5, it is determined that the subject is relatively short. Done (step S6),
On the other hand, when the number of integrations n> n0-α, it can be determined that the subject is relatively far away (step S7).

The CPU 13 controls the focusing operation and the like of the camera according to the result obtained in this manner.

In the present embodiment, the number of integrations is compared depending on whether or not the light emitting operation of the IRED 1 is possible. This is because if the transistor, the resistor 7 and the integrating capacitor 10 have temperature dependency,
This is because the number of integrations when no signal is input changes.
Further, it is possible to cope with a variation in the number of integrations due to a variation in the power supply voltage and a variation in the number of integrations due to variation in the differential transistors 8 and 9 and the inverters 34 and 35.

FIG. 6 is an electric circuit diagram showing a main part of a distance measuring apparatus according to a third embodiment of the present invention. Note that portions denoted by the same reference numerals as those in the first and second embodiments have the same functions and effects, and thus the description thereof will be omitted. Further, FIG. 6 shows only the integration circuit which is a main part, and other circuits are the same as those in the first and second embodiments.

The third embodiment is an embodiment for preventing variations in the characteristics of the linear amplifier. The output of the first linear amplifier (see the second embodiment) is smoothed by a resistor 42 and a capacitor 43. Thus, the base potential of the differential transistor 9 is fixed. Therefore, the same potential as the voltage VBi shown in FIG. 2 is applied to the base of the differential transistor 9. Further, in the present embodiment, the integration inhibition control is performed by setting the common emitter potential of the differential transistors 8 and 9 to “L” level by the switch 41.

According to the third embodiment, the second linear amplifier in the second embodiment is not required, and therefore, it is not necessary to consider the offset voltage between the first linear amplifier and the inverter 34.

FIG. 7 is an electric circuit diagram showing a distance measuring apparatus according to a fourth embodiment of the present invention. The portions indicated by the same reference numerals as those in the first to third embodiments have the same functions and effects, and thus the description thereof will be omitted.

This fourth embodiment is an embodiment which does not depend on the change in the reflectance of the object, and has two divided photodiodes 4a and 4b as shown in the figure, and differentially amplifies each photocurrent signal output. Integrates from the circuit.

The IRED 1, the light projecting lens 2, the light receiving lens 3 (not shown), and the two divided photodiodes 4a and 4b are arranged based on a known triangulation method shown in FIG.

That is, the infrared light projected from the IRED 1 is condensed on the subject 15 via the projection lens 2, and the reflected light from the subject 15 is separated from the projection lens 2 by a distance S. The light receiving lens 3 is
The light is condensed on the photodiodes 4a and 4b in an array arranged at a distance f from the array.

In this embodiment, the photodiode 4
Let L1 be the distance to the subject 15a when the reflected light from the subject 15 enters the boundary between the light receiving portions a and 4b. At this time, the photocurrent signal outputs of the photodiodes 4a and 4b are equal. When the photocurrent signal output from the photodiode 4b is large, it can be determined that the distance L2 to the subject 15b is longer than the distance L1.

FIG. 9 shows the photodiodes 4a and 4b.
FIG. 6 is a front view showing a state of reflected light from the subject 15 incident on the light source.

In the case of FIG. 9A, when the distance to the subject 15 is L1, FIG. 9B shows when the distance to the subject is L2, and FIG. Distance is L1
The times closer to each other are shown. As is clear from FIG. 9, by comparing (COMP) the magnitudes of the photocurrent signal outputs of the two photodiodes 4a and 4b, the distance to the subject 15 is longer than L1 regardless of the reflectivity of the subject. Can be determined.

Returning to FIG. 7, the configuration of this embodiment will be described.

The photocurrent signal outputs of the photodiodes 4a and 4b are converted into voltages by the resistors 31a and 31b, respectively, and AC-coupled by the capacitors 32a and 32b, respectively, and the first linear amplifiers (33a and 34a) and the second linear amplifiers The structure leading to (33b, 34b) is the same as in the second embodiment. The configuration of the differential amplifier circuit in the integrating circuit is the same as that of the second embodiment except that the differential transistor 8 in the second embodiment is replaced with the differential transistors 8a and 8b. In this embodiment, switches 44 and 45 are used for switching between the two photodiodes 4a and 4b.

FIG. 10 is a time chart showing the integration operation of the fourth embodiment.

When the switch 44 is turned on, the switch 45 is turned on.
Is turned off, the output of the first linear amplifier goes to "H" level, the differential transistor 8a is turned off, and the voltage comparison and integration between the differential transistor 8b and the differential transistor 9 is performed in the same manner as in the first embodiment. Is performed.

On the other hand, the switch 45 is turned on and the switch 4
4 turns off, the output of the second linear amplifier goes to "H" level, the differential transistor 8b turns off, and a voltage comparison between the differential transistor 8a and the differential transistor 9 is performed in the same manner as in the first embodiment. Integration is performed.

Assuming that the integration operation is performed while switching the switches 44 and 45 and the number of times of integration until the predetermined voltage is reached is na and nb,
These comparisons make it possible to determine the distance without depending on the reflectance of the subject.

FIG. 11 is a flowchart showing the operation of determining the distance to the subject in the fourth embodiment.

First, the IRED 1 is caused to emit light, and the integrating capacitor 10 is activated by the photocurrent signal from the photodiode 4a.
Is counted until the integral value of the integral exceeds a predetermined value (steps S1 and S2). After reaching the predetermined value, the integral value of the integrating capacitor 10 due to the photocurrent signal from the photodiode 4b is determined. The number of integrations nb is counted until the value exceeds the value (steps S3 and S4). Next, the number of integrations na and nb are compared (step S5), and when the number of integrations na <nb, it can be determined that the subject is relatively close (step S6),
On the other hand, when the number of integrations na> nb, it can be determined that the subject is relatively far away (step S7).

FIG. 12 is an electric circuit diagram showing a distance measuring apparatus according to a fifth embodiment of the present invention. In addition, the above-mentioned first to fourth
Portions indicated by the same reference numerals as those of the embodiment have the same functions and effects, and thus description thereof will be omitted.

This embodiment is an embodiment in which operational amplifiers 51 and 52 constitute an autofocus circuit without using a linear amplifier of a C-MOS inverter.

Since the input impedances of the transistors 53 and 54 can be apparently made very small by the operation of the operational amplifiers 51 and 52, in this embodiment, a well-known optical position detecting element (P
SD) 50 is used in place of the photodiode.
Further, since the integration circuit uses a circuit similar to that of the third embodiment, the description is omitted here.

According to the fifth embodiment, the transistor 5
3 changes, the potential is connected to the bases of the differential transistors 8 and 9 of the integrating circuit.
It is possible to determine the position of the optical signal incident on D50, and it is possible to obtain a better distance determination resolution than the two-divided photodiodes 4a and 4b (see FIG. 7).

FIGS. 13 and 14 are electric circuit diagrams showing distance measuring devices according to sixth and seventh embodiments of the present invention. Note that portions indicated by the same reference numerals as those in the first to fifth embodiments have the same functions and effects, and thus description thereof will be omitted.

In the sixth and seventh embodiments, the bipolar transistors 8 and 9 in the second embodiment are
In this embodiment, S-type transistors 8M and 9M are used.

Generally, the CPU is manufactured by a MOS type process, and the first and second linear amplifiers (see the second embodiment) are also constituted by C-MOS inverters. The seventh embodiment focuses on this point,
The feature is that these elements are formed on the same chip as the CPU 13.

From the principle of current amplification of the MOS transistor, the drain current IINT is given by IINT = KＫ (VOUT-VT) × (VOUT-VT). Where VT is the threshold voltage,
K is a constant determined from the gate oxide film capacity, channel width, effective channel length, and the like.

Further, if the resistors 7, 33, 36, etc. are constituted by ion implantation resistors or polysilicon resistors, the components other than the photodiode 4, the capacitors 10, 32, etc. can be constituted on the same chip as the CPU 13. .

FIG. 14 shows the seventh embodiment, but is the same as the CPU 13 except for IRED1, IRED driver 5, photodiode 4, integration capacitor 10, capacitor 32, and voltage conversion resistor 31 as external components. And is configured as a new one-chip microcomputer 63.

This newly incorporated element, for example,
P-MOS of inverters 34 and 35 and differential amplifier circuit
The ratio of the transistors 8M, 9M and the like to the entire chip area of the CPU 63 is several percent or less, and the increase in cost is small. On the other hand, the cost reduction by the element that can be omitted 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 assembly steps during manufacturing and an improvement in the reliability of the entire camera.

In each of the above embodiments, a PNP transistor and a P-MOS transistor are used. However, the present invention is not limited to this.
A type transistor may be used.

[0078]

As described above, according to the present invention, it is possible to provide a distance measuring apparatus having a simple configuration, a low price, and a high performance autofocus function.

[Brief description of the drawings]

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

FIG. 2 is a time chart showing a relationship between light emission of an IRED and an integration state of an integration capacitor in the first embodiment.

FIG. 3 is an electric circuit diagram showing a configuration of a distance measuring apparatus according to a second embodiment of the present invention.

FIG. 4 is a time chart showing an integration operation in the second embodiment.

FIG. 5 is a flowchart showing an operation of determining a subject distance in the second embodiment.

FIG. 6 is an electric circuit diagram showing a main part of a distance measuring apparatus according to a third embodiment of the present invention.

FIG. 7 is an electric circuit diagram showing a distance measuring apparatus according to a fourth embodiment of the present invention.

FIG. 8 is an explanatory diagram showing an arrangement of an IRED, a light projecting lens, a light receiving lens, and a photodiode in the fourth embodiment.

FIG. 9 is a front view showing a state of reflected light from a subject, which is incident on a photodiode in the fourth embodiment.

FIG. 10 is a time chart showing the integration operation of the fourth embodiment.

FIG. 11 is a flowchart illustrating a distance determination operation to a subject according to the fourth embodiment.

FIG. 12 is an electric circuit diagram showing a distance measuring apparatus according to a fifth embodiment of the present invention.

FIG. 13 is an electric circuit diagram showing a distance measuring apparatus according to a sixth embodiment of the present invention.

FIG. 14 is an electric circuit diagram showing a distance measuring apparatus according to a seventh embodiment of the present invention.

FIG. 15 is an electric circuit diagram showing an example of a conventional distance measuring device.

FIG. 16 is an electric circuit diagram showing another example of the conventional distance measuring apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... IRED 2 ... Light-emitting lens 3 ... Light-receiving lens 4 ... Photodiode 5 ... IRED driver 6 ... Light-receiving amplifier 7 ... Emitter resistance 8,9 ... Differential transistor 10 ... Integrating capacitor 11,12 ... Resistance 13 ... CPU 14 ... Switch

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-66811 (JP, A) JP-A-2-72770 (JP, A) JP-A-4-48208 (JP, A) JP-A-63-1988 288582 (JP, A) JP-A-5-232377 (JP, A) JP-A-5-173059 (JP, A) JP-A-6-137860 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01C 3/06 G02B 7/32 G03B 13/36

Claims (2)

(57) [Claims] 1. A distance-measuring light projecting means for projecting distance-measuring light to a subject, and a photocurrent signal dependent on the amount of received light by receiving reflected signal light of the distance-measuring light from the subject. A photocurrent signal integrating means including a differential amplifier and an integrating capacitor connected to an output terminal of the differential amplifier, and integrating a signal dependent on a photocurrent signal output from the photodetector; differential this based on the output result from the optical current signal integrating means anda calculation control means for determining the distance to the object, the optical current signal integration means, which constitute a differential amplifier
Photocurrent signal output from the light receiving means of the transistor
Controls the base potential of differential transistors that are not connected
A distance measuring device characterized by performing an integration operation by performing the above operation . 2. A distance measuring device for projecting distance measuring light to a subject.
Light projection means, and receives and receives the reflected signal light of the distance measurement light from the subject
A light receiving means for outputting a photocurrent signal depending on the amount of light; a differential amplifier;
And a photocurrent signal output from the light receiving means.
Photocurrent signal integration means for integrating the dependent signals, object scene based on the output from the optical current signal integrating means
Comprising an arithmetic control means for determining the distance to the body, and the photocurrent signal integrating means constitute a differential amplifier differential
Integration by controlling the common emitter potential of transistors
A distance measuring device that performs an operation.