JPH0690029B2 - Distance detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a distance detection device that detects the distance of an object to be measured from the position of a light spot incident on a semiconductor position detector.

[Conventional technology]

Conventionally, there is known a distance detection device that detects a distance of an object to be measured from a position of a light spot incident on the semiconductor position detector using the semiconductor position detector.

FIG. 4 is a block diagram of a general semiconductor position detector, and FIG. 5 is a block diagram of a general distance detecting device using the semiconductor position detector of FIG.

In FIG. 4, a general semiconductor position detector 25 is formed by sequentially laminating an N ⁺ type semiconductor layer 27, a high resistance N type semiconductor layer 28, and a p type semiconductor layer 29 having a uniform resistivity. Has been done. The N-type semiconductor layer 28 and the p-type semiconductor layer 29 form a photodiode, and the N ⁺ -type semiconductor layer 27 is a common electrode for applying a reverse bias voltage to the photodiode.
30 are provided. A pair of electrodes 31, 32 are provided on both ends of the p-type semiconductor layer 29.

If a predetermined voltage is applied to the common electrode 30 of this semiconductor position detector 25 and a light spot enters at the position SP, the position SP
An electron-hole pair is generated at the pn junction between the p-type semiconductor layer 29 and the N-type semiconductor layer 28 below the p-type semiconductor layer 28, which causes a photocurrent I ₀ proportional to the incident energy of the light spot from the common electrode 30 to the p-type. Semiconductor layer
Flow toward 29.

By the way, the distance between the electrodes 31 and 32 is c, the resistance of the p-type semiconductor layer 29 between them is R _C , the distance between the light spot incident position SP and the electrode 32 is x, and the p-type semiconductor between them is If the resistance of the layer 29 is R _X , the photocurrent I ₀ is divided by the resistance of the p-type semiconductor layer 29 at the light spot incident position SP. That is, the current I _A to the electrode 31 and the current I _B to the electrode 32 are respectively the p-type semiconductor layer 29 between the electrode 31 and the light spot incident position SP.
Resistance (R _C -R _X ), p between the electrode 32 and the light spot incident position SP
Is divided in inverse proportion to the resistance R _X type semiconductor layer _{29, I A = I 0 ·} [R X / R C] I B = I 0 · [(R C -R X / R C] ... (1) become that way.

As described above, since the resistivity of the p-type semiconductor layer 29 is evenly distributed, the resistances R _X and R _C are proportional to the distances x and c with the same proportional constant.

Thus, equation _{(1), I A = I 0 · x} / c I B = I 0 · [(c-x) / c] is expressed as ... (2).

As can be seen from the equation (2), the currents I _A and I _B are extracted from the electrodes 31 and 32, and predetermined analog calculation processing is performed in a predetermined calculation circuit (not shown), so that the light spot incident position from the electrode 32 is detected. The distance x to the SP can be obtained.

Further, referring to FIG. 5, a general distance detecting device is a light source 22 that outputs light to be incident on the object to be measured 21, and a projector that condenses the light output from the light source 22 onto the object to be measured 21. The light lens 23, the light receiving lens 24 that collects the light reflected by the DUT 21, and the reflected light that is collected by the light receiving lens 24 enters as a light point, and the light point incident position SP is detected. And the semiconductor position detector 25.

The light source 22 is composed of a light emitting diode or a semiconductor laser. Further, the light receiving lens 24 is arranged with a gap of the base line length B from the light projecting lens 23, and the semiconductor position detector 25 is arranged with a gap of a focal length f from the light receiving lens 24. There is. The optical axis A of the light receiving lens is not aligned with the electrode 32 of the semiconductor position detector 25 and is spaced from the electrode 32 by a distance X ₀ .

In the distance detecting device of FIG. 5, the object to be measured 21 is located at a distance L from the light projecting lens 23, and at this time, the light spot from the light receiving lens is located at the position SP of the semiconductor position detector 25, that is, Assuming that the light enters from the electrode 32 at the distance x, the distance x is based on FIG.
, X−x ₀ = x ₁ = f · B / L (3)

Therefore, from the distance x obtained by subjecting the currents I _A and I _B of the equation (2) to predetermined analog arithmetic processing and the equation (3),
21 distances L can be detected.

By the way, in the conventional distance detecting device, the analog calculation process is performed by a predetermined analog divider (not shown).
I _A, the difference between the current I _B, the current I _A, were made by performing a division of the sum of the current I _B. That is, the distance x is obtained by performing the arithmetic processing of the division of the currents I _A and I _B as (I _A −I _B ) / (I _A + I _B ) = 1−2x / c (4) Was there.

If the distance x is eliminated from the equations (3) and (4), (I _A −I _B ) / (I _A + I _B ) = 1−2x ₀ / c−2f · B / c · L (5) Is obtained, the calculated current value (I _A −I _B ) / (I _A +
I _B) is inversely proportional to the distance L of the object to be measured 21.

Therefore, in the conventional distance detection device, the calculated current value (I _A −
Direct distance L from I _B ) / (I _A + I _B ) by analog calculation
Cannot be detected, and the calculated current value (I _A −I _B ) / (I _A
+ I _B ) and the distance L are prepared in advance as an inverse proportional relationship as shown in the equation (5), and based on this conversion table, the microprocessor built into the device calculates the current calculation value (I _A
The distance L corresponding to −I _B ) / (I _A + I _B ) was detected by software processing.

[Problems to be solved by the invention]

As described above, in the conventional distance detection device, the analog divider calculates the current calculated value (I _A −I _B ) / (I _A + I _B ) based on the currents I _A and I _B taken from the semiconductor position detector 25. Since the distance L of the object to be measured 21 is inversely proportional to the calculated current value (I _A −I _B ) / (I _A + I _B ), the distance L is calculated.
Could not be directly detected as an analog output of the calculated current value. For this reason, since a conversion table that defines the inverse proportional relationship must be separately prepared in, for example, a memory, the cost of the device increases, and based on this conversion table, a current calculation value (I _A − Since I _B ) / (I _A + I _B ) had to be detected, the processing speed until the distance L was detected became slow, and it was applied to applications where high-speed response is desired, such as the visual sensor of an industrial robot. There was a limit to it.

It is an object of the present invention to provide a distance detection device having a high-speed response characteristic that can directly detect the distance of an object to be measured as an analog output from a calculated current value.

[Means for solving problems]

The present invention comprises a light source for making light incident on an object to be measured, a semiconductor position detector on which light reflected from the object to be measured is incident as a light spot, and an arithmetic circuit. When the above-mentioned conventional technique is used, a photocurrent flowing through the semiconductor position detector is divided by a current extracted from one of a pair of electrodes of the semiconductor position detector. To improve the problem of.

[Action]

In the present invention, the light reflected from the object to be measured is incident on the semiconductor position detector as a light spot. In the semiconductor position detector,
When a light spot is incident, a photocurrent flows, and this photocurrent is divided according to the distance between the pair of electrodes and the light spot incident position and is extracted from each electrode as a pair of currents. The arithmetic circuit divides the photocurrent and the current drawn from one of the pair of electrodes of the semiconductor position detecting element. The photocurrent can be obtained as the sum of a pair of currents, or can be directly taken out from the common electrode. By the way, since the above division result is proportional to the distance to the object to be measured, the arithmetic circuit can directly output the distance to the object to be measured from the division result. As a result, the distance to the object to be measured can be detected at high speed.

〔Example〕

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

FIG. 1 is a block diagram of an arithmetic circuit used in the distance detecting device of the present invention.

The entire structure of the distance detecting device of the present invention is similar to that shown in FIG. 5, and the structure of the semiconductor position detector used in the distance detecting device of the present invention is shown in FIG. Since these are the same as those described above, detailed description thereof will be omitted. However, in this embodiment, the optical axis A of the light receiving lens 24 and the electrode 32 in FIG. 5 are aligned as shown in FIG.

The calculation circuit 1 shown in FIG. 1 has a current calculation value (I _A + I _B ) / I _A for the currents I _A and I _B extracted from the semiconductor position detector 25.
For calculating.

In FIG. 1, the electrodes 31 and 32 of the semiconductor position detector 25 are connected to the inverting terminals of the operational amplifiers 2 and 3, respectively.
The non-inverting terminals of the operational amplifiers 2 and 3 are grounded, and the operational amplifiers 2 and 3 have the currents I _A and I _A extracted from the electrodes 31 and 32, respectively.
It is for converting I _B into a predetermined voltage value determined by the resistance R _f .

The output terminal of the operational amplifier 2 is connected to the inverting terminal of the operational amplifier 4 via the resistor R _{2 and} to the inverting terminal of the operational amplifier 5 via the resistor R ₃ . Also, the operational amplifier 3
Is connected to the inverting terminal of the operational amplifier 4 via the resistor R ₁ .

The operational amplifier 4 adds the output voltage of the operational amplifier 2 and the output voltage of the operational amplifier 3, and adds the added output voltage to the resistance.
The output voltage is converted into an output voltage determined by the ratio of R ₁ and R ₂ to the resistance R ₄ . Further, the operational amplifier 5 converts the output voltage of the operational amplifier 2 into an output voltage determined by the ratio of the resistance R ₃ and the resistance R _5, and outputs the output voltage. Operational amplifier 4,
The output terminals of the operational amplifier 5 are connected to the analog divider 6, respectively.

The analog divider 6 divides the output voltage of the operational amplifier 4 and the output voltage of the operational amplifier 5 to obtain a calculated current value (I _A
+ I _B ) / I _A is calculated.

The operation of the distance detecting device having such a configuration will be described below.

A reverse bias voltage is applied to the common electrode 30 of the semiconductor detector 25 shown in FIG. 1, and the light reflected from the DUT 21 is condensed by the light receiving lens 24 as shown in FIG. It is incident on the position SP of 25. In this embodiment, since the optical axis A of the light receiving lens 24 is aligned with the electrode 32 of the semiconductor position detector 25, the distance between the light spot incident position SP and the electrode 32 is x ₁ .

When the light spot from the object to be measured 21 enters the light spot incident position SP,
The currents I _A and I _B divided by the distance between the light spot incident position SP and the electrodes 31 and 32 are extracted from the electrodes 31 and 32, respectively. In this way, the electrodes 31 and 32 each function as a signal extraction electrode, and the one electrode 32 serves as a reference for measuring the distance x ₁ to the light spot incident position SP.

The currents I _A and I _B are input to the operational amplifiers 2 and 3, respectively. The operational amplifiers 2 and 3 respectively convert the currents I _A and I _B into voltages determined by the resistance R _f . That is, the output voltage of the operational amplifiers 2 and 3
V _A and V _B are respectively V _A = −I _A · R _f V _B = −I _B · R _f (6)

The output voltages V _A and V _B of the operational amplifiers 2 and 3 are applied to the inverting terminal of the operational amplifier 4 via resistors R ₂ and R ₁ , respectively, while the voltage of the non-inverting terminal of the operational amplifier 4 is “0” V. Therefore, the output voltage V ₀₁ of the operational amplifier 4 is V ₀₁ =-(V _A / R ₂ + V _B / R ₁ ) ・ R ₄ = I _A / R ₂ + I _B / R ₁ ) ・ R _f・ R ₄ ... (7)

On the other hand, the output voltage V _A of the operational amplifier 2 is applied to the inverting terminal of the operational amplifier 5 through the resistor R ₃ , while the voltage of the non-inverting terminal of the operational amplifier 5 is “0” V. output voltage V ₀₂ of becomes _{V 02 = -V a · R 5} / R 3 = I a · R f · R 5 / R 3 ...... (8).

In the analog divider 6, the output voltage V from the operational amplifiers 4 and 5
Divides ₀₁ and V ₀₂ and outputs the calculated current value from terminal OUT. Assuming that the resistors R ₁ , R ₂ and R ₃ are the same and the resistors R ₄ and R ₅ are the same, the calculated current value from the equations (7) and (8) is calculated as the calculated current value = V ₀₁ / It is calculated as V ₀₂ = (I _A + I _B ) / I _A (9).

By the way, the current I _A and the current I _B are I _A = I ₀ · x ₁ / c I _B = I ₀ · [(c−x ₁ ) / c in the semiconductor position detector 25 according to the above-mentioned equation (2). ] …… (10) is taken out. Where I ₀ is photocurrent, c is electrodes 31, 32
Is the distance between. Further, x ₁ is the distance from the optical axis A of the light receiving lens 24 to the light spot incident position SP, but since the optical axis A of the light receiving lens 24 and the electrode 32 are aligned in this embodiment, the distance is
x ₁ is the distance between the light spot incident position SP and the electrode 32.

From the equations (9), (10) and (3), the calculated current value (I _A + I _B ) / I _A in the analog divider 6 is (I _A + I _B ) / I _A = c · L / It will be output as f · B (11).

(11) As is apparent from the equation, the current calculated value from the analog divider 6 of the present embodiment _{(I A + I B) /} I A is proportional to the distance L of the object to be measured 21.

FIG. 3 shows the calculated current value (I _A + I _B ) / I _A in this embodiment.
7 is a diagram showing a relationship between the distance L of the object to be measured 21 and FIG. In FIG. 3, the shortest distance Ln indicates the limit of the distance L of the object to be measured 21 that can be detected by the distance detecting device. The light spot that re-approaches and is condensed by the light receiving lens 24 enters the position of the electrode 31 of the semiconductor position detector 25. At this time, the current I _A becomes the photocurrent I ₀ , the current I _B becomes “0”, and the shortest distance Ln becomes Ln = f · B / c (12). Also, in FIG. 3, the gradient of the graph GH is
It is the proportional constant c / (f · B) in the equation (11).

Calculated current (I _A + I _B ) / I _A and distance L are proportional constants c / f ・
Since it is proportional to B, the distance L of the object to be measured can be directly obtained as the output of the analog divider 6 by giving the proportional constant c / f · B in the analog divider 6 by a resistor or the like. It will be possible.

As described above, according to the present embodiment, in the analog divider 6, the calculated current value (I _A +) proportional to the distance L of the DUT 21 is calculated.
The distance L can be obtained directly from the terminal OUT by calculating I _B ) / I _A and giving the proportional constant c / f · B by a resistor or the like, so that it is not necessary to perform software processing by the microprocessor, The distance of the measurement object 21 can be detected at high speed.

In the above embodiment, the photocurrent I _0, that is, (I _A + I _B ).
Was calculated as the sum of the pair of currents drawn from the pair of electrodes, but may be taken directly from the common electrode 30. In this case, the operational amplifier 3 and the operational amplifier 4 in FIG.
Is unnecessary, and the photocurrent I ₀ from the common electrode 30 is
Since it suffices to convert it to V ₀₁ and directly input it to the analog divider 6, the arithmetic circuit can be further downsized.

〔The invention's effect〕

As described above, according to the present invention, the photocurrent flowing in the semiconductor position detector and the current drawn from one of the pair of electrodes of the semiconductor position detector are divided. Therefore, the distance to the object to be measured can be directly obtained from this division result, and the distance to the object to be measured can be detected at high speed.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an arithmetic circuit used in a distance detecting device of the present invention, and FIG. 2 is a diagram for explaining a positional relationship between an optical axis of a light receiving lens of the present invention and an electrode of a semiconductor position detector. Three
FIG. 4 is a diagram showing the relationship between the calculated current value and the distance obtained by the distance detecting device of the present invention, FIG. 4 is a configuration diagram of a general semiconductor position detector, and FIG. 5 is a configuration of a general distance detecting device. It is a figure. 1 ... Operation circuit, 2, 3, 4, 5 ... Operation amplifier, 6 ... Analog divider, 21 ... DUT, 22 ... Light source, 25 ... Semiconductor position detector, 30 ... Common Electrodes, 31,32 ... Electrodes, SP ...
… Light spot incident position, I ₀ …… Photocurrent, I _A , I _B …… Current, x ₁ …
… Distance, L …… Distance of object to be measured, A …… Optical axis

Claims (3)

[Claims] 1. A light source for making light incident on an object to be measured, a semiconductor position detector on which light reflected from the object to be incident enters as a light spot, and an arithmetic circuit. A pair of first and second signal extraction electrodes are provided, and the first signal extraction electrode serves as a reference for measuring the distance to the light spot incident position, and the arithmetic circuit is configured to detect the light spot. The photocurrent flowing through the semiconductor position detector when incident is divided by the current extracted from the second signal extraction electrode of the semiconductor position detector, and the result of the division is the distance to the object to be measured. By being directly proportional,
A distance detecting device capable of directly detecting the distance to the object to be measured from the division result. 2. The distance according to claim 1, wherein the photocurrent is calculated as a sum of a pair of currents extracted from a pair of signal extraction electrodes of the semiconductor position detector. Detection device. 3. The distance detecting device according to claim 1, wherein the photocurrent is taken out from a common electrode of the semiconductor position detector.