JPH0694449A - Distance measuring sensor - Google Patents

Abstract

PURPOSE:To lessen the consumption of electric energy by installing an oscillator which oscillates pulses for driving a light emitting element in a controlling circuit and generating various kinds of timing signals necessary for measuring distance. CONSTITUTION:As a light emitting element, LED 1 is driven to emit light by pulses in a driving circuit 9 and the light emitting timing by the circuit 9 is controlled by a controlling circuit 11. Also, the signal from PSD 5 as a light receiving element is received by a signal processing circuit 8 and processed there. The circuit 9 and the circuit 8 are built in a bipolar process circuit 22. The circuit in which electricity flows constantly is only a CMOS process circuit 33 and electric power is controlled to run in the circuit 22, which consumes a large quantity of current, only at the time of measuring the distance by the controlling circuit 11. That is, for example, in the case where distance measurement is carried out every 50ms, electricity is supplied to the circuit 22 only for several milliseconds in 50ms by timing signals from timing signal generating means 31 of the oscillator 13 and, therefore, the consumption of electricity is lowered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring sensor using a PSD or the like.

[0002]

2. Description of the Related Art PSD (Positi) as a light receiving element
on Sensitive Photodefecto
r = semiconductor position detecting element) is a photodiode (PD)
Is an optical spot position detection sensor to which is applied.

In this PSD, the balance of the signal currents I ₁ and I ₂ extracted changes depending on the position of the incident optical spot. FIG. 2 shows a principle of detection of a distance measuring sensor using PSD.

As shown in FIG. 2, the infrared light emitting diode 1
The light emitted from the (LED) is reflected by the detection object (for example, a person) 3 via the lens 2 and enters the PSD 5 via the lens 4. The position where the reflected light M enters the PSD 5 (the spot position of the light) changes depending on the distance D between the person 3 and the sensor, and when the detected object 3 becomes far (the D becomes longer), the reflected light M1 becomes As shown by the broken line in 2, the spot position of the light incident on the PSD 5 also changes.
When the spot position of the light incident on the PSD 5 changes, the signal current I ₁ extracted from both ends of the PSD 5 correspondingly changes.
And the balance of I ₂ changes.

By detecting the balance between the signal currents I ₁ and I ₂ by the signal processing circuit, the distance between the detection object 3 and the sensor can be detected, and it can be used as a distance measuring sensor using the PSD 5. it can.

FIG. 3 shows a control circuit diagram of a conventional distance measuring sensor using a PSD. In FIG. 3, 8 is a signal processing circuit unit, 9 is an LED drive circuit unit, 11 is a control circuit unit, and these are constituted by a one-chip bipolar IC 12.

Here, the control circuit section 11 includes an oscillator 13 to generate pulses for driving LEDs and various necessary control signals.

Further, the bipolar IC 12 is turned on / off by a control input Vin in order to reduce current consumption.
Was under control.

Further, in FIG. 3, reference numeral 14 is a register for power supply, and a CMOS circuit which is easy to increase the density and consumes less power is used.

Here, the operating principle of the PSD will be described with reference to FIG. PSD5, as shown in FIG.
The silicon chip is composed of three layers, a p ⁻ layer on the front surface, an n ⁺ layer on the back surface, and an i layer in the middle, and when the surface of the PSD 5 is irradiated with a light spot φ, the electric charge (carrier) generated is resistance. The layer (p ⁻ layer) is divided in inverse proportion to the incident position of light and the distance to the extraction electrodes A and B, and is extracted as currents I ₁ and I ₂ from the respective electrodes A and B.

Now, as shown in FIG. 4A, the photocurrent I ₀ ,
The distance from the midpoint of the electrodes A and B to the light incident point P is x,
The resistance value from the incident position P point to the electrode A is R ₀₁ , the resistance value from the incident position P point to the electrode B is R ₀₂ , the distance between the electrodes A and B is L, and the resistance value between the electrodes A and B is R. _T , electrodes A and B
Let I ₁ and I ₂ be the currents extracted from
The currents I ₁ and I ₂ are represented by the following equations (1) and (2).

[0012]

[Equation 1]

Since the distribution of the specific resistance R _i of the surface resistance layer (p ⁻ layer) is uniform as shown in FIG. 4B, the resistance R ₀₁ ,
R ₀₂ is proportional to the distance from the incident point P to the electrodes A and B, and is represented by the following equation.

[0014]

[Equation 2]

Substituting this into the equations (1) and (2), the currents I ₁ and I ₂ extracted from the electrodes A and B are given by the following equations.

[0016]

[Equation 3]

Here, when the ratio of the sum and the difference of the currents I ₁ and I ₂ is taken, the following equation is obtained.

[0018]

[Equation 4]

As described above, when the PSD is used as the light receiving element, the position information can be directly obtained as an output.

An example of the signal processing circuit section 8 for processing the signal currents I ₁ and I ₂ of the PSD 5 is shown in FIG. In FIG. 5, R _{1 to} R ₇ are resistors, and P _{1 to} P ₅ are amplifiers. P
The signal currents I ₁ and I ₂ of SD5 are supplied to the current-voltage conversion circuit unit 8
At a, it is converted into voltages V ₀₁ and V ₀₂ . V ₀₁ is V
₀₁ = R ₁ × I ₁ , V ₀₂ becomes V ₀₂ = R ₁ × I ₂ . Next, the subtraction of _{V 02} and _{V 01} at subtraction circuit portion _8b, to obtain an output voltage _{V OA} corresponding to I 2 -I _1. V
_0A is represented by the following equation.

[0021]

[Equation 5]

Further, in the adding circuit section 8c, V ₀₁ and V
Add ₀₂ . In FIG. 5, V ₀₃ is represented by the following equation.

[0023]

[Equation 6]

Then, the output V _OB corresponding to I ₁ + I ₂
Can be obtained. V _0B is represented by the following equation.

[0025]

[Equation 7]

By calculating the _VOA and _VOB with a microcomputer or the like, _VOA / _VOB is obtained. V _0A
/ V _0B is expressed by the following equation.

[0027]

[Equation 8]

Therefore, (I ₂ −I ₁ ) / (I ₁ + I
₂ ) corresponds to the position of the light incident on the PSD 5, as described above, and by (I ₂ −I ₁ ) / (I ₁ + I ₂ ),
The spot position of the light incident on the PSD 5 can be known.

When the spot position of the light incident on the PSD 5 is known, the distance between the sensor and the detection object 3 is known as described above.

In this way, the signal current I _{1 of the} PSD _{5 is}
By processing and I ₂ in the signal processing circuit unit 8, the distance between the sensor and the detected object 3 can be detected.

An example of another signal processing circuit section 8 of the PSD 5 is shown in FIG. In the circuit of FIG. 6, 15 is a logarithmic conversion circuit section, 16 is a differential amplification circuit section, 17 and 18 are log diodes, and their outputs V ₀₁ and V ₀₂ are represented by the following equations. Note that k is the Boltzmann constant, T is the absolute temperature (°
K) and q are electron charge amounts.

[0032]

[Equation 9]

Then, the output V ₀ from the amplifier circuit section 16
Is expressed by the following equation.

[0034]

[Equation 10]

With this circuit, an output corresponding to log (I ₁ / I ₂ ) can be obtained. I ₁ / I ₂ is PS
It corresponds to the spot position of the light incident on D, and log
From (I ₁ / I ₂ ), the spot position of the light incident on the PSD can be known. When the spot position of the light incident on the PSD 5 is known, the distance between the sensor and the detection object 3 can be detected as described above.

At the control input Vin in FIG. 3, the bipolar IC 12 is powered on from the time Da when it falls from High to Low, and the distance measuring operation is started.

At this time, the oscillator 13 of the control circuit unit 11
Generates a pulse for driving an LED and various necessary control signals.

Such a distance measurement result is A / D-converted and then output as serial data in synchronization with an external control signal like Db, and when the power is turned off next time D
Continue operation until c.

[0039]

In the conventional distance measuring sensor, as shown in FIG. 3, since the control input Vin is generated externally, a control signal generating circuit such as a microcomputer is required externally. Therefore, the entire system using the distance measuring sensor is increased in size and the current consumption is increased accordingly.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a distance measuring sensor that does not require an external control signal generating circuit and can achieve low power consumption.

[0041]

As shown in FIG. 1, the means for solving the problems according to the first aspect of the present invention applies light from the light emitting element 1 to the detection object 3 and reflects the light reflected by the detection object 3 into the light receiving element 5.
In the distance measuring sensor for measuring the distance from the output cost of the pair of currents I ₁ and I _{2 which} varies depending on the incident spot position of the light receiving element 5 to the detection object 3, the light emitting element 1
A drive circuit section 9 for driving the light-receiving element, a signal processing circuit section 8 for receiving a signal from the light-receiving element 3, and a control circuit section 11 for controlling these are provided, and the control circuit section 11 drives the light-emitting element. An oscillator 13 that oscillates a pulse for use in a laser is provided, and the oscillator 13 is provided with a timing signal generating means 31 that generates various timing signals necessary for distance measurement.

According to a second aspect of the present invention, in the means for solving the problems, the drive circuit section 9 and the signal processing circuit section 8 according to the first aspect are:
The control circuit unit 11 and the oscillator 13 according to claim 1 incorporated in the bipolar process circuit 22 are incorporated in the CMOS process circuit 33, and the control circuit unit 11 is configured to determine whether or not it is during distance measurement. And a switching means 28 for switching ON the power source of the bipolar process circuit 22 only when the determination means 27 determines that the distance measurement is being performed.

The problem solving means according to claim 3 of the present invention is a bipolar process circuit 22 and a CMO according to claim 2.
The S process circuit 33 is a single bi-CMOS integrated circuit 3
It is integrated in 5.

[0044]

In the problem solving means according to the above-mentioned claim 1, the oscillator 13 provided in the control circuit section 11 produces various timings required for distance measurement, and the drive circuit section 9 and the signal processing circuit section 8 are generated based on the timings. Control. Therefore, when considering the external circuit without the need for a control signal from the outside,
The system becomes simpler than before.

In the second aspect, only the CMOS process circuit 33 including the control circuit section 11 and the oscillator 13 is always powered on, and the bipolar process circuit 22 having a large current consumption is powered on only during distance measurement. Is controlled by the control circuit unit 11 of the CMOS process circuit 33.
Therefore, the current consumption of the system is reduced.

According to the third aspect, each of the circuit parts 8, 9 and 11 can be integrated into one chip, and the distance measuring sensor can be downsized.

[0047]

1 is a control block diagram of a distance measuring sensor according to an embodiment of the present invention, and FIG. 2 is a principle diagram of a general distance measuring sensor. As shown in FIGS. 1 and 2, the distance measuring sensor detects light from an LED 1 as a light emitting element through a lens 2 to detect an object 3
The light reflected by the detection object 3 is received by the PSD 5 as a light receiving element through the lens 4, and the detection object is detected from the output cost of the pair of currents I ₁ and I _{2 which} varies depending on the incident spot position on the PSD 5. The distance up to 3 is measured.

The internal structure of the LED 1 is the same as that of the conventional example shown in FIG. The LED 1
Is driven by the drive circuit section 9 to emit light from the panel. The light emission timing of the drive circuit unit 9 is controlled by the control circuit unit 11 described later.

The signal from the PSD 3 is as shown in FIG.
The signal processing circuit unit 8 receives and processes the signal. The signal processing circuit section 8 receives the signal of the PSD 3 and, after the arithmetic processing, performs an A / D conversion means 2 for producing a digital output corresponding to the distance.
1 is provided.

The drive circuit section 9 and the signal processing circuit section 8
Are incorporated in the bipolar process circuit 22.
Here, the bipolar process circuit 22 is a method of a semiconductor integrated circuit, and basically has a function that occurs at a junction surface (pn junction surface) of a p-type semiconductor and an n-type semiconductor, and is a MOS-I.
It is faster than C. The bipolar process circuit 22
Is turned on by the control circuit section 11 described later only during distance measurement.
To be done.

The drive circuit section 9 and the signal processing circuit section 8
Are controlled by the control circuit unit 11.

The control circuit section 11 has a storage means 26 for storing the digital data after A / D conversion in the signal processing circuit section 8 and a determination means 27 for determining whether or not the distance is being measured. The power source of the bipolar process circuit 22 is turned on only when the determination means 27 determines that the distance measurement is being performed.
A switching means 28 for N switching and an oscillator 13 for oscillating the pulse for driving the LED are provided. The oscillator 13 is provided with a timing signal generating means 31 for generating various timing signals necessary for distance measurement.
That is, for example, if the distance measurement is performed once at a pitch of 50 ms, the timing signal generating means 31 transmits the distance measurement timing every cycle of the 50 ms pitch.

The control circuit section 11 including the oscillator 13 (hereinafter referred to as the control circuit section 11 etc.) is incorporated in the CMOS process circuit 33. Here, the CMOS process circuit 33 is a system of a semiconductor integrated circuit, which basically uses the function of a field effect transistor (FET) using three elements of metal, oxide, and semiconductor, and has a lower speed than a bipolar IC. However, it has characteristics that it is easy to increase the density and consumes very little power.

The bipolar process circuit 22 and the CMOS process circuit 33 are composed of a single bi-CMOS.
It is integrated in the integrated circuit 35 (IC).

In FIG. 1, reference numeral 14 is a register circuit, which is connected to a power supply Vcc and supplies power to the signal processing circuit section 8, drive circuit section 9 and PSD 5. The register circuit 14 is integrated in the bipolar process circuit 22 like the signal processing circuit unit 8 and the driving circuit unit 9.

In the distance measuring sensor having the above-described structure, the power is always turned on in the CMOS including the control circuit section 11 and the like.
With the process circuit 33 alone, the bipolar process circuit 22 with a large current consumption is controlled so that the power is turned on only during distance measurement.
It is controlled by the control circuit unit 11 of the S process circuit 33. That is, for example, when distance measurement is performed once every 50 ms, the timing signal from the timing signal generating means 31 of the oscillator 13 supplies power to the bipolar process circuit 22 for only a few milliseconds within 50 ms.
Therefore, the current consumption of the system is reduced.

Further, the timing signal generating means 31 of the oscillator 13 of the CMOS process circuit 33 produces various timings required for distance measurement, and does not require external control signals. Therefore, considering the external circuit, the system becomes simpler than the conventional one.

The present invention is not limited to the above embodiments, and it goes without saying that many modifications and changes can be made to the above embodiments within the scope of the present invention.

For example, in the above embodiment, the distance measuring timing is set to 5 by the internal timing signal generating means 31, for example.
Although the distance measurement is controlled to be performed once at the 0 ms pitch, the distance measurement may be performed only for a predetermined time by external signal input. Even in this case, only the CMOS process circuit 33 is always turned on, and the bipolar process circuit 22 is turned on only during distance measurement.
Controlled by.

[0060]

As is apparent from the above description, according to claim 1 of the present invention, the control circuit section for controlling the drive circuit section and the signal processing circuit section is provided with the oscillator for oscillating the pulse for driving the light emitting element, Since the oscillator is provided with the timing signal generating means, various timings required for distance measurement can be created inside the distance measurement sensor, and no external control signal is required. Therefore, considering the external circuit, the system becomes simpler than the conventional one.

According to the present invention, the drive circuit unit and the signal processing circuit unit are incorporated in the bipolar process circuit, the control circuit unit and the oscillator are incorporated in the CMOS process circuit, and the control circuit unit determines whether or not the distance is being measured. Since the determination means for performing the distance measurement and the switching means for switching on the power source of the bipolar process circuit only when it is determined that the distance measurement is being performed are provided, the power source is always on because the CMOS including the control circuit section and the like is used. The bipolar process circuit, which consumes a large amount of current only with the process circuit, is controlled by the control circuit section of the CMOS process circuit so that the power is turned on only during distance measurement. Therefore, the current consumption of the system is reduced.

According to the third aspect, since the bipolar process circuit and the CMOS process circuit are integrated in a single bi-CMOS integrated circuit, it is possible to realize space saving by one-chip implementation and enable high-density mounting. It has an excellent effect.

[Brief description of drawings]

FIG. 1 is a control block diagram of a distance measuring sensor according to an embodiment of the present invention.

[Fig. 2] Detection principle diagram of a general distance measuring sensor

FIG. 3 is a control block diagram of a conventional distance measuring sensor.

FIG. 4A is a principle diagram of the operation of the light receiving element, and FIG. 4B is a distribution diagram of the specific resistance of the surface resistance layer.

FIG. 5 is a diagram showing an example of a conventional signal processing circuit for a signal current of a light receiving element.

FIG. 6 is a diagram showing another example of the conventional signal processing circuit for the signal current of the light receiving element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 light emitting element 3 detected object 5 light receiving element 8 signal processing circuit section 9 drive circuit section 11 control circuit section 13 oscillator 22 bipolar process circuit 27 judging means 28 switching means 31 timing signal generating means 33 CMOS process circuit 35 CMOS integrated circuit I ₁ , I ₂ signal current

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[Procedure amendment]

[Submission date] October 15, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

Further, in FIG. 3, reference numeral 14 is a power supply source.
A Gyure data densification easy and low power consumption CMOS circuit has been used.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0041

[Correction method] Change

[Correction content]

[0041]

As shown in FIG. 1, the means for solving the problems according to the first aspect of the present invention applies light from the light emitting element 1 to the detection object 3 and reflects the light reflected by the detection object 3 into the light receiving element 5.
In the distance measuring sensor for measuring the distance to the detection object 3 from the output ratio of the pair of currents I ₁ and I _{2 which} varies depending on the incident spot position of the light receiving element 5, the light emitting element 1
A drive circuit section 9 for driving the light-receiving element, a signal processing circuit section 8 for receiving a signal from the light-receiving element 3, and a control circuit section 11 for controlling these are provided, and the control circuit section 11 drives the light-emitting element. An oscillator 13 that oscillates a pulse for use in a laser is provided, and the oscillator 13 is provided with a timing signal generating means 31 that generates various timing signals necessary for distance measurement.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0042

[Correction method] Change

[Correction content]

[0042] The driving circuit 9 and the signal processing circuit unit 8 is incorporated into a bipolar process circuit 22, the control circuit 11 and the oscillator 13, CMOS
The control circuit unit 11 is incorporated in the process circuit 33 and
And a judging means 27 for judging whether or not the distance is being measured,
Switching means 28 is provided for switching ON the power source of the bipolar process circuit 22 only when the determination means 27 determines that the distance measurement is being performed .

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0043

[Correction method] Change

[Correction content]

The problem solving means according to claim 2 of the present invention is
Bipolar process circuit 22 and CM according to claim 1.
The OS process circuit 33 is integrated in a single bi-CMOS integrated circuit 35.

[Procedure correction 6]

[Document name to be amended] Statement

[Name of item to be corrected] 0045

[Correction method] Change

[Correction content]

Further, the always powered, only CMOS process circuit 33 consisting of the control circuit unit 11 and the oscillator 13, a large bipolar process circuit 22 of the current consumption, CMOS process so that the power supply only when the distance measuring enters It is controlled by the control circuit unit 11 of the circuit 33. Therefore, the current consumption of the system is reduced.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0046

[Correction method] Change

[Correction content]

According to the second aspect , each of the circuit parts 8, 9 and 11 can be integrated into one chip, and the distance measuring sensor can be downsized.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0047

[Correction method] Change

[Correction content]

[0047]

1 is a control block diagram of a distance measuring sensor according to an embodiment of the present invention, and FIG. 2 is a principle diagram of a general distance measuring sensor. As shown in FIGS. 1 and 2, the distance measuring sensor detects light from an LED 1 as a light emitting element through a lens 2 to detect an object 3
The light reflected by the detection object 3 is received by the PSD 5 as a light receiving element through the lens 4, and the detection object is detected from the output ratio of the pair of currents I ₁ and I _{2 which} varies depending on the incident spot position on the PSD 5. The distance up to 3 is measured.

[Procedure Amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0048

[Correction method] Change

[Correction content]

The internal structure of the PSD 5 is the same as that of the conventional example shown in FIG. The LED
1, as shown in FIG. 1, the drive circuit 9 is Nitepa pulse emission driving. The light emission timing of the drive circuit unit 9 is controlled by the control circuit unit 11 described later.

[Procedure Amendment 10]

[Document name to be amended] Statement

[Correction target item name] 0049

[Correction method] Change

[Correction content]

The signal from the PSD 5 is received and processed by the signal processing circuit unit 8 as shown in FIG. The signal processing circuit unit 8 receives the signal of the PSD 5 and performs arithmetic processing,
It is provided with an A / D conversion means 21 for making a digital output corresponding to the distance.

[Procedure Amendment 11]

[Document name to be amended] Statement

[Correction target item name] 0055

[Correction method] Change

[Correction content]

[0055] In FIG. 1, 14 is a Les Gyure capacitor circuit, is connected to the power supply Vcc, and supplies power to the signal processing circuit unit 8, the driving circuit 9 and the PSD 5. The <br/> Les Gyure capacitor circuit 14 is integrated in the same way bipolar process circuit 22 and the signal processing circuit unit 8 and the drive circuit 9.

[Procedure Amendment 12]

[Document name to be amended] Statement

[Correction target item name] 0061

[Correction method] Change

[Correction content]

[0061] Further, the driving circuit unit and the signal processing circuit section incorporated in the bipolar process circuit, incorporating a control circuit unit and an oscillator in CMOS process circuit, the control circuit unit, and a determining means for determining whether the distance measurement Since there is provided switching means for switching ON the power source of the bipolar process circuit only when it is determined that it is during distance measurement,
The CM always consists of a control circuit, etc.
The bipolar process circuit, which consumes a large amount of current only with the OS process circuit, is controlled by the control circuit unit of the CMOS process circuit so that the power is turned on only during distance measurement. Therefore, the current consumption of the system is reduced.

[Procedure Amendment 13]

[Document name to be amended] Statement

[Correction target item name] 0062

[Correction method] Change

[Correction content]

According to claim 2 , the bipolar process circuit and the CMOS process circuit are combined into a single bi-CMOS.
Since it is integrated in an integrated circuit, there is an excellent effect that space saving can be realized by one chip and high density mounting is possible.

Claims (3)

[Claims] 1. A detection object is irradiated with light from a light emitting element, the light reflected by the detection object is received by a light receiving element, and the output cost of a pair of currents that fluctuates depending on the incident spot position of the light receiving element to the detection object. In the distance measuring sensor for measuring the distance, a drive circuit section for driving the light emitting element, a signal processing circuit section for receiving a signal from the light receiving element, and a control circuit section for controlling these are provided. The circuit unit is provided with an oscillator that oscillates a pulse for driving the light emitting element,
The optical distance sensor, wherein the oscillator is provided with a timing signal generating means for generating various timing signals necessary for distance measurement. 2. The drive circuit unit and the signal processing circuit unit according to claim 1 are incorporated in a bipolar process circuit, and the control circuit unit and the oscillator according to claim 1 are incorporated in a CMOS process circuit. Further, there is provided a judging means for judging whether or not the distance is being measured, and a switching means for switching ON the power source of the bipolar process circuit only when the judging means judges that the distance is being measured. Optical distance measuring sensor characterized by. 3. An optical distance measuring sensor, wherein the bipolar process circuit and the CMOS process circuit according to claim 2 are integrated in a single bi-CMOS integrated circuit.