JPH0695020B2 - Distance detector - Google Patents

Description

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

FIG. 8 is a block diagram of a conventional general semiconductor position detector, and FIG. 9 is a block diagram of a general distance detecting device using the semiconductor position detector of FIG. As shown in FIG. 9, the distance detecting device has a light source 1, a light projecting lens 2, a light receiving lens 3 and a semiconductor position detector 4, and the distance to the DUT 5 is measured by the light on the semiconductor position detector 4. It is calculated from the point position SP. Therefore, first, the semiconductor position detector 4
The configuration and operation of will be described.

In FIG. 8, the semiconductor position detector 4 is an N ⁺ type semiconductor layer 41.
And a high-resistance N-type semiconductor layer 42 and a P-type semiconductor layer 43 having a uniform resistivity are sequentially laminated. The N-type semiconductor layer 42 and the P-type semiconductor layer 43 form a photodiode, and the N ⁺ -type semiconductor layer 41 is provided with a common electrode 44 for applying a reverse bias voltage to the photodiode. In addition, a pair of electrodes is provided on both ends of the P-type semiconductor layer 43.
45,46 are provided. When a predetermined voltage is applied to the common electrode 44 of the semiconductor position detector 4 and light is incident as a light spot at the position SP in FIG. 8, the P-type semiconductor layer 43 and the N below the position SP are formed. An electron-hole pair is generated at the PN junction with the type semiconductor layer 42, whereby a photocurrent I ₀ proportional to the incident energy of the light spot flows from the common electrode 44 toward the P type semiconductor layer 43.

By the way, the distance between the electrodes 45 and 46 is c, the resistance of the P-type semiconductor layer 43 between them is R _c , the distance between the light spot incident position SP and the electrode 46 is x, and the P-type semiconductor between them is If the resistance of the layer 43 is R _x , the photocurrent I ₀ is divided by the resistance of the P-type semiconductor layer 43 at the light spot incident position SP.
That is, the current I _A to electrode 45 and the current I to electrode 46
_B is a P-type semiconductor layer 43 between the electrode 45 and the light spot incident position SP.
(R _c −R _x ) and the resistance R _x of the P-type semiconductor device 43 between the electrode 46 and the light spot incident position SP are divided in inverse proportion to each other, and I _A = I ₀ [R _{x / R c] I B =} I 0 · [(R c -R x) / R c] ... to become like (1).

As described above, since the resistivity of the P-type semiconductor layer 43 is evenly distributed, the resistances R _x and R _c are proportional to the distances x and c with the same proportional constant. Therefore, the equation (1) is expressed as I _A = I ₀ · x / c I _B = I ₀ · [(c−x) / c] (2) As can be seen from the above formula (2),
Obtaining the currents I _A and I _B from the electrodes 45 and 46 and performing a predetermined analog calculation process in a predetermined calculation circuit (not shown) to obtain the distance x from the electrode 46 to the light spot incident position SP. You can

Next, the configuration and operation of the conventional distance detecting device will be described with reference to FIG.

In the figure, the distance detection device includes a light source 1 that outputs light for irradiating an object to be measured 5, a light projecting lens 2 that condenses the light output from the light source 1 onto the object to be measured 5, and an object to be measured. A light-receiving lens 3 for condensing the light reflected at 5, and a light-receiving lens 3
The reflected light condensed by the light enters as a light spot, and is composed of the above-mentioned semiconductor position detector 4 which detects the light spot incident position SP. Here, the light source 1 is composed of a light emitting diode or a semiconductor laser. Also, the light receiving lens 3
Are spaced apart from the light projecting lens 2 by a base line length B, and the semiconductor position detector 4 is spaced apart from the light receiving lens 3 by a focal length f. In addition,
It is assumed that the optical axis A of the light receiving lens 3 is not aligned with the electrode 46 of the semiconductor position detector 4 and is spaced from the electrode 46 by a distance x ₀ .

In the distance detecting device of FIG. 9, the DUT 5 is located at a distance L from the light projecting lens 2, and the light spot from the light receiving lens 3 is at the position SP of the semiconductor position detector 4 (electrode 46). ) To a distance x)),
Based on FIG. 9, the distance x is calculated as x−x ₀ = x ₁ = f · B / L (3) with respect to the distance L to the DUT 5. Therefore, the currents I _A and I in the above equation (2)
_Since the distance x is obtained by performing a predetermined analog calculation process on _B , it is possible to detect the distance L to the object to be measured 5 by using the equation (3).

[Problems to be solved by the invention]

By the way, in the conventional distance detection device, the analog calculation process for obtaining the distance L is performed by a predetermined analog divider (not shown), and the difference between the current I _A and the current I _B and the current I _A and the current I _B. It was done by dividing it with the sum of I _B. That is, the currents I _A and I _B are divided by the calculation processing of (I _A −I _B ) / (I _A + I _B ) = 1−2x / c (4) You can ask. Therefore, clearing the distance x from the above equation (3) and _{(4), (I A -I B) /} (I A + I B) = 1-2x 0 / c-2f · B (c · L) Since the relationship of (5) is obtained, the calculated current value (I _A −I _B ) / (I _A +
It is found that I _B ) is inversely proportional to the distance L to the object to be measured 5, and thus the distance L can be indirectly obtained.

Therefore, in the conventional distance detection device, the calculated current value (I _A −
_{I B) / (I A +} I B) can not be detected directly on the distance L by the analog arithmetic value from the current calculated value (I _A -I _B)
Since the inverse proportional relationship between / (I _A + I _B ) and the distance L as shown in the equation (5) must be prepared in advance as a conversion table, the cost required for a device such as a memory is increased. Further, based on this conversion table, the microprocessor current calculated value of the device visceral _{(I A -I B) / (} I A + I B)
Since the distance L corresponding to is detected by software processing, the processing speed until the distance L is detected becomes slow, and it is applied to the application such as a visual sensor of an industrial robot where a high speed response is desired. There was a limit.

Therefore, it is an object of the present invention to provide a distance detection device that has a simple structure and can detect the distance to an object to be measured at high speed and easily.

〔means〕

The present invention is a semiconductor position detector configured by providing a pair of electrodes at both ends of a semiconductor layer on which a light source for making light incident on a DUT and a reflected light from the DUT are incident as light spots, and a reflected light Is provided with a calculation means for dividing the photocurrent flowing through the semiconductor layer when the light is incident as light and the current extracted from one of the pair of electrodes, and is directly proportional to the distance from the division result to the DUT. Therefore, in the distance detection device that can directly detect the distance from the division result to the DUT, the semiconductor position detector has a fixed or semi-fixed resistance connected to one of the pair of electrodes. The split ratio of the photocurrent flowing through the pair of currents can be set by a fixed or semi-fixed resistor.

[Action]

According to the configuration of the present invention, when the reflected light from the DUT is incident as a light spot, a photocurrent appears in the semiconductor position detector,
This current is divided according to the distance between the pair of electrodes and the light spot incident position, and is extracted from the pair of electrodes. Therefore, the calculation means divides the total photocurrent and the current taken out from one of the pair of electrodes, and operates from this result to quickly derive the distance to the object to be measured. If a fixed or semi-fixed resistor is connected to one of the pair of electrodes, the detectable distance range (distance measuring range) can be set arbitrarily.

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

FIG. 1 is a basic configuration diagram of a distance detecting device according to an embodiment of the present invention. As shown in the figure, the distance detecting device includes a light source 1, a light projecting lens 2 that collects the emitted light flux, and a light receiving lens 3 that is arranged at a distance of a baseline length B from the light projecting lens 2.
And a semiconductor position detector 4 that receives light from the light receiving lens 3.
And a calculation circuit 20 which receives a photocurrent from the semiconductor position detector 4 and performs a calculation described later. And
The arithmetic circuit 20 includes I / V converters 21A and 21B that convert the divided currents I _A and I _B into voltage signals V _B and V _B , an adder 22 that adds the voltage signals V _A and V _B , and a voltage It has an analog divider 23 that divides the sum V _A + V _B of the signal V _A and the voltage signal.

According to the above configuration, the output of the arithmetic circuit 20 (V _A + V _B ) / V _A
Is (I _A + proportional to I _B / I _A, and _{(I A + I B) /} I A is c in FIG. 1 as described later, f, b, a distance to a numerical value proportional constant determined by L _F L Is equal to, the distance L to the DUT 5 is
Can be easily obtained. Therefore, from the principle of distance detection, the configuration and operation of the distance detection device of FIG. 1 according to the present invention will be sequentially described in detail.

In the distance detection device, it is important that the distance measuring range can be set arbitrarily. For example, in the case of application to a traveling path of an automatic guided vehicle or an assisting device (Japanese Patent Publication No. Sho 60-81609), it is necessary to set the distance measuring range to the far side.
On the other hand, when it is applied to the position detection of the processing part in a laser processing machine or the like, it is necessary to set the distance measuring range close to the object to be measured and to detect the distance with high resolution. .

FIG. 2 is a diagram showing the distance detecting optical system when the distance measuring range is set from L _N to L _F. The luminous flux emitted from the light source 1 is condensed by the light projecting lens 2 and the object to be measured 5 is irradiated. DUT 5
The reflected light from is collected by the light-receiving lens 3 which is arranged at a distance of the base line length B from the light-projecting lens 2. The semiconductor position detector 4 is arranged at a condensing position (light spot position) at a distance f from the light receiving lens 3.

Here, the closest distance and the farthest distance within the distance measuring range are L _N and L _F , respectively, and the distance to the DUT 5 is L. In addition, the semiconductor position detector 4 from the optical axis of the light receiving lens 3
Let x _F be the distance to one end of the light receiving part, and let x be the distance from the position of the light spot SP at which the reflected light from the DUT 5 is condensed by the light receiving lens 3 to the optical axis of the light receiving lens 3. , Light spot
Assuming that the distance from the position of SP to one end of the light receiving portion of the semiconductor position detector 4 is x ₁ and the length of the light receiving portion of the semiconductor position detector 4 (interval between a pair of electrodes) is c, The relational expression holds.

FIG. 3 is a diagram in which a resistance R _xF is added to one electrode of the semiconductor position detector 4. The distance from the electrode 46 to the light spot incident position SP is x ₁ , the resistance of the P-type semiconductor layer in this portion is R _x1 , the length of the light receiving portion of the semiconductor position detector 4 is c, and this resistance is R _c And the current generated at the light spot incident position is I ₀ . Further, when R _xF of the additional resistance is made to correspond to x _F shown in FIG. 2, this value has the relation of the following equation (10).

When the currents drawn from the electrodes 45 and 46 are I _A and I _B , respectively, the values can be obtained from the following equations (11) and (12).

Therefore, in the analog division section of the arithmetic circuit 20 in FIG.
When the operation of the expression (3) is executed, it becomes the following expression (13).

Here, since x = x ₁ + x _F from the equation (8), by substituting this into the equation (13), the following equation (14) can be obtained.

Since all of the parentheses on the right side of the equation (14) are constants, it can be seen that the output of the analog division section is proportional to the distance L to the DUT 5.

As described above in detail, if the value of the additional resistance R _xF shown in the equation (10) is determined for an arbitrary measurement range, (14)
It can be seen that the output value of the analog division unit represented by the equation is proportional to the distance L to the DUT 5.

FIG. 4 is a diagram showing a basic configuration of an analog arithmetic circuit for executing the arithmetic operation of the equation (14). First, reflected light from an object to be measured (not shown) enters the semiconductor position detector 4. For the required measurement range, set the base line length B shown in FIG. 2 and the distance f from the light receiving lens 3 to the semiconductor position detector 4, and add the additional resistance from the relational expression shown by the equation (10).
_Calculate the value of R _{x F.} This additional resistance R _xF causes the current I _A and
If the division ratio of I _B is changed, the output of the analog division section shown in equation (14) becomes an output proportional to the distance within the measurement range.

In FIG. 4, the currents I _A and I _B taken out from the semiconductor position detector 4 are subjected to current-voltage conversion and amplification by the operational amplifiers U ₁ and U ₂ to obtain voltage values V _A and V _B.
Then, the sum of the signal voltage values (V _A + V _B ) is obtained by the operational amplifier U _3.
And the operational amplifier U ₄ inverts the signal voltage V _A. Next, when (V _A + V _B ) / V _A is executed by the analog divider 23,
The output value is equivalent to the operation result of (I _A + I _B ) / I _A ,
It can be set to a value proportional to the distance L.

FIG. 5 is a block diagram of a specific example of the arithmetic circuit used for the arithmetic processing of the present invention. Light source 1 'is constituted by using light emitting diodes or semiconductor lasers, when the input pulse signal phi ₃ to the base of the transistor TR ₂ light sources 1' pulse point lamp in synchronization therewith. Therefore, when the emitted light flux is condensed on the object to be measured by the light projecting lens, the reflected light from the object to be measured is condensed on the semiconductor position detector 4 by the light receiving lens. One of the pair of electrodes provided in the semiconductor position detector 4 is connected to the ground via the additional resistance R _xF .

When the light condensed by the light-receiving lens is incident on the semiconductor position detector 4, photoelectric current is generated in the light spot position, among the current divided by the P-type semiconductor layer, I _B flows through the additional resistor R _xF . The other current I _A is current-voltage converted by the resistor R ₁ .
The converted signal voltage V _A is capacitively coupled by the capacitor C ₁ , and only the AC component when the light source 1 ′ is pulsed is transmitted and is non-inverted and amplified by the operational amplifier U ₁ . Since the common electrode 44 of the semiconductor position detector 4 is connected to V _cc (positive power supply) through the resistor R _2, the photocurrent current resistor R ₂ - is voltage conversion. The signal voltage (−V _A −V _B ) after this conversion is input to the operational amplifier U ₂ via the capacitor C ₂ . The operational amplifier U ₂ is designed to perform inverting amplification, and this output is V _A +
Become V _B.

It should be noted that U _{3 to} U ₆ in the figure are sample hold circuits, in which only signal components are extracted. This is because, in general, not only the reflected light from the light source 1 ', but also ambient light such as sunlight or indoor illumination light is incident on the semiconductor position detector 4. That is, in the semiconductor position detector 4, this ambient light is also photoelectrically converted, and the superimposed current is taken out. Therefore, in order to extract only the signal component from this, a pair of sample hold circuits and a differential operational amplifier are used.

FIG. 6 is a diagram showing signal waveforms of the arithmetic circuit. The sample hold circuits U ₃ and U ₅ in FIG. ₅ perform sampling with the pulse signal φ ₁ shown in FIG. That is, at the timing of this signal φ ₁ , the voltage value immediately before the light source 1 ′ shown in FIG.
It will be stored in U ₃ and U ₄ . On the other hand, the sample and hold circuits U ₅ and U ₆ execute sampling with the pulse signal φ ₂ . As is clear from FIG. 6, this signal is phi ₂ timing and the light source 1 'is pulsed point lights, therefore the voltage level at the time of standing up or V _A or V _A + V _B will be held. Therefore, the sample-hold circuits U ₃ and U _{4 are connected} by the differential operational amplifiers U ₇ and U _8.
Alternatively, take the difference between the outputs of U ₅ and U ₆ . In this way, the signal voltage V _A or V _A + V _B can be extracted. When the calculation of (V _A + V _B ) / V _A is executed by the analog divider 23, this output value becomes equivalent to the calculation value of (I _A + I _B ) / I _A , and an analog output proportional to the distance L is obtained. Obtainable.

In the circuit shown in FIG. 5, the operational amplifier U ₉ is used for comparing the levels of the reference voltage V _ref and the signal voltage V _A and controlling the drive current of the light source 1 ′. That is, V _A <V _ref
At this time, the base potential of the transistor Tr ₁ is raised, the driving current flowing through the light source 1'becomes large, and the light emission output becomes large. Therefore, by adding the operational amplifier U ₉ and the transistor Tr ₁ , the value V _A on the denominator side of the analog divider 23 can always maintain a constant voltage level during measurement, and the calculation accuracy can be improved.

FIG. 7 shows the arithmetic output of the present invention and the conventional arithmetic output.
In the vicinity of the closest distance of 200 mm, the output deviates from a straight line because the spot light condensed by the light receiving lens is slightly deviated from the light receiving part of the semiconductor position detector, but at other distances it is almost linear. It has become.

The present invention is not limited to the above embodiments, but various modifications can be made.

For example, the specific configuration of the arithmetic circuit can be various circuit configurations. Moreover, the size of the light receiving part of the semiconductor position detector is appropriately set and shown in FIG. 5 on the same silicon substrate.
By forming the R _1, R ₂ and _{R xF, R c, R 1} , can be the temperature characteristics of R ₂ and R _xF same, stable splitting ratio of the signal current I _A and I _B to a temperature change Becomes possible.

〔The invention's effect〕

As described above in detail, according to the present invention, the photocurrent flowing through the semiconductor position detector and the current flowing through 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 the division result, and the distance to the object to be measured can be detected at high speed. Further, if a fixed resistance or a semi-fixed resistance is added to one of the pair of electrodes, it becomes possible to directly obtain the distance with respect to an arbitrarily set distance measuring range.

[Brief description of drawings]

FIG. 1 is a block diagram of a distance detecting device according to an embodiment of the present invention, and FIG. 2 illustrates a light spot position on a semiconductor position detector when a distance measuring range is set from L _N to L _F. 3 and FIG. 3 are additional resistances R _xF and x _F for explaining the arithmetic processing of the present invention.
FIG. 4 is a basic configuration diagram of a circuit for executing the operation of the present invention, FIG. 5 is a block diagram of a specific example of the arithmetic circuit used in the embodiment of the present invention, and FIG. Is a signal waveform diagram of an arithmetic circuit, FIG. 7 is a diagram for comparing distance measurement characteristics, FIG. 8 is a configuration diagram of a conventional semiconductor position detector, and FIG. 9 is a configuration diagram of an example of a conventional distance detection device. Is. 1, 1 '... light source, 2 ... light projecting lens, 3 ... light receiving lens, 4 ...
Semiconductor position detector, 5 ... DUT, 20 ... Arithmetic circuit, 23 ...
Analog divider, 41 ... N ⁺ type semiconductor layer, 42 ... N type semiconductor layer, 43 ... P type semiconductor layer, 44 ... Common electrode, 45, 46 ... Pair of electrodes.

Claims (3)

[Claims] 1. A light source for making light incident on an object to be measured, and a semiconductor position detector comprising a pair of electrodes at both ends of a semiconductor layer on which reflected light from the object to be incident is incident as a light spot. A calculation means for dividing a photocurrent flowing through the semiconductor layer and a current extracted from one of the pair of electrodes when the reflected light is incident as a light spot, and the division result is the measured object. In the distance detection device that is directly proportional to the distance to the object to be measured from the division result, the semiconductor position detector is one of the pair of electrodes. A distance detection device, comprising a fixed or semi-fixed resistor connected to, and a division ratio of a photocurrent flowing through the pair of electrodes can be set by the fixed or semi-fixed resistor. 2. The distance detecting device according to claim 1, wherein the arithmetic means divides the sum of currents extracted from both of the pair of electrodes as the photocurrent. 3. The semiconductor position detector has a common electrode serving as a counter electrode of the pair of electrodes, and the arithmetic means divides a current extracted from the common electrode as the photocurrent. The distance detection device according to claim 1.