JPH067052B2 - Two-division type semiconductor position detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to incidence of reflected light by a semiconductor position detector arranged in a direction away from a light source in the direction of an object to be measured and a certain distance away from the light source projecting the light. The present invention relates to an improved two-divided semiconductor position detector used in an active distance detecting device or the like that measures a distance to an object to be measured by detecting a position.

(Prior Art) FIG. 6 is a schematic diagram showing an optical system of a typical active distance detecting device.

The luminous flux emitted from the light source 1 is condensed on the surface 5 of the object to be measured by the light projecting lens 2.

The reflected light from the surface 5 is focused on the semiconductor position detector 4 by the light receiving lens 3 which is arranged at a fixed base line distance.

The base line length is B, the distance to the object to be measured is L, the distance (image forming distance) between the light receiving lens 3 and the light detecting element 4 is f, and the distance from the optical axis of the light receiving lens 3 to the focusing position on the light detecting element 4 is When the distance (movement amount of spot light) is x, the relationship shown in the equation (1) is established.

x = (f · B) / L (1) When the two sides of the equation (1) are differentiated by the distance L, the following equation (2) is obtained.

dx / dL = −f · B / L ² (2) From equation (2), the movement change amount (dx / dL) of the spot light on the semiconductor position detector 4 is the reciprocal of the distance to the object to be measured. It is proportional to the square.

In the conventional general distance detecting device shown in FIG. 6, the semiconductor position detector 4 is a one-dimensional semiconductor position detector (for example, S2153-02 of Hamamatsu Photonics KK).
Is used.

FIG. 7 is a sectional structure showing such a semiconductor position detector.

The surface of the high resistance semiconductor (silicon substrate) is formed by a uniform resistance layer, and a pair of electrodes for signal extraction is provided at both ends of this layer.

The surface layer forms a PN junction and exhibits a photoelectric effect.

In the figure, the distance between the electrode 6 (A) and the electrode 7 (B) is C, the resistance between them is Rc, the distance from the electrode 6 (A) to the light incident position is x, and the resistance to that point is Rx. And

The photo-generated charges generated at the light incident position reach the P-type resistance layer 8 as a photocurrent proportional to the incident energy of light, and are divided so as to be inversely proportional to the resistance value to each electrode.
It is taken out from the electric distances 6 (A) and 7 (B).

Let the photocurrent generated by the incident light be I ₀ , and the electrode 6
The currents drawn in (A) and 7 (B) are changed to IA, IB.
Then, equation (3) is obtained.

IA = I ₀ · [(Rc-Rx) / Rc], IB = I ₀ · (Rx / Rc) (3) Since the P-type resistance layer is uniform and the length and the resistance value are proportional, (3) The formula can be rewritten as formula (4).

IA = I _O [(C−x) / C], IB = I _O · x / C (4) When the current value is calculated by the equation (4), the following equation (5) is obtained.

(IA-IB) / (IA + IB) = 1-2x / C (5) From the equation (5), it can be understood that the light incident position can be known from the values of IA and IB regardless of the intensity of the incident light. .

If this is graphed, the graph of FIG. 8 is obtained.

The calculated current value (IA-IB) / (IA + IB) changes with respect to the movement amount x of the spot light on the straight line connecting the coordinate values (0, + 1), (C / 2,0), (C, -1). To do.

Substituting equation (1) into equation (5) yields equation (6).

(IA-IB) / (IA + IB) = 1- (2f · B) / (C · L) (6) Further, when both sides of the formula (6) are differentiated by the distance L, the formula (7) is obtained.

d [(IA-IB) / (IA + IB)] / dL = 2f · B / (C · L ² ) ... (7) From equation (7), the amount of change in the calculated current value (IA-IB) / (IA + IB) Is
It can be seen that it is proportional to the square of the reciprocal of the distance L as in the case of the equation (2).

(Problems to be Solved by the Invention) As described above, the amount of change in the calculated current value of the conventional semiconductor position detector is proportional to the square of the reciprocal of the distance.

Therefore, in order to obtain an output value proportional to the distance by using this semiconductor position detector in a distance detecting device, it is necessary to create a linear correction table using a computer or the like and convert the output value.

When a distance detecting device is used as a visual sensor of an industrial robot, it is an indispensable condition that its output value is in proportion to the distance.

The configuration of the distance detecting device is complicated and expensive, and the distance detecting device having a high-speed response cannot be realized due to the software.

An object of the present invention is to divide a resistive layer on the surface of a semiconductor position detector so that a signal current having distance information proportional to the amount of change in the distance to the object to be measured can be taken out. To provide a detector.

(Means for Solving the Problems) In order to achieve the above-mentioned object, a two-divided semiconductor position detector according to the present invention is a triangulation method for detecting the incident position of reflected light from a measured object of projected light. In a one-dimensional semiconductor position detector used in a distance detecting device, a light receiving surface of the semiconductor position detector is insulated and separated along a curve, an electrode is provided on each light receiving surface, and reflected light is received by each of the separated light receiving surfaces. Incident on the surface,
By generating a generated current corresponding to the incident area from both electrodes, a signal current having distance information proportional to the measured object distance is taken out.

The two-divided semiconductor position detector is provided with an N ⁺ layer forming a common terminal on the back side of a silicon substrate, a rectangular P layer serving as a light receiving surface is insulated and separated by a separation layer on the front side, and a signal current is taken out to each P layer. In the configuration in which the electrodes for use are arranged, the relationship of H (x) + W (x) + I = WW (x) = ax / (x + b) can be established at a position x from the side of the light receiving surface on the light source side. it can.

Where W is the width of the semiconductor position detector, I is the length of the separation layer in the width direction, H (x) is the length of the light receiving surface on the light source side in the width direction,
W (x) is the length in the width direction of the light receiving surface on the other side, and a and b are constants.

The constants a and b can be defined by the following equation.

a = Lf (W−I) / (Lf−Ln) b = (f · B) / Lf where Ln is the short distance side distance measurement limit, Lf is the long distance side distance measurement limit, B is the base line length, and f is It is the distance (imaging distance) between the light receiving lens and the detector.

(Example) The present invention will be described in more detail with reference to the drawings.

FIG. 1 is a plan view showing a first embodiment of a two-divided semiconductor position detector according to the present invention.

FIG. 2 is a sectional structural view of the two-divided semiconductor position detector.

The P layers 15 and 16 divided by the separation layer 14 formed on the silicon substrate 22 are light receiving surfaces, and are connected to the current extraction electrodes 12 (A) and 13 (B), respectively.

Further, an N ⁺ layer 23 is formed on the back side, and a common electrode 24 is formed on the N ⁺ layer 23.
Are connected.

The distance measuring range of the distance detecting device is changed from Ln (short distance side) to Lf.
(Long distance side)

This semiconductor position detector is combined with the above-described optical system shown in FIG.

The left electrode 12 (A) of the two-divided semiconductor position detector is located on the light source 1 side in FIG.

The spot light position where the reflected light flux from the object to be measured at the distance Lf is condensed by the light receiving lens is shown in FIG. 1 as the spot light position of the left electrode 12 (A), Ln of the two-division semiconductor position detector. It is set near the right electrode 13 (B).

When the base line length of the optical system is B and the distance from the light receiving lens to the light receiving surface of the two-division type semiconductor position detector for distance measurement is f, the linear spot light position x at the distance Lx is expressed by the following formula (8). It is represented by.

x = f · B · [(1 / Lx) − (1 / Lf)] (8) Further, the effective length C of the light receiving surface is given by the formula (9).

C = f.B. [(1 / Ln)-(1 / Lf)] (9) In FIG. 1, of the P layers divided by the separation layer 14, the P layer 15 is generated by incident light. The generated photocurrent is the electrode 12 (A), and the photocurrent from the P layer 16 is the electrode B.
It is taken out from (13).

It is assumed that the hatched portion in the figure is irradiated with the reflected light flux from the distance Lx in the form of narrow slit light.

The total photocurrent generated at this time is the photocurrent extracted from the I ₀ electrode 12 (A) and the electrode 13 (B), respectively.
And IB, the width of the P layer 15 in contact with the electrode 12 (A) is H (x), and the width of the P layer 16 in contact with the electrode 13 (B) is W (x).

Here, when the width of the slit light is sufficiently small, the extracted photocurrents IA and IB can be approximated by the following equations (10) and (11).

IA = H (x) · I ₀ /[H(x)+W(x)]...(1
0) IB = W (x) · I ₀ / [H (x) + W (x)] …… (1
1) The following relationship holds between H (x) and W (x).

H (x) + I + W (x) = W where: W is the total width of the semiconductor position detector: I is the width of the separation layer 14 in the width direction, and the calculated current value is given by equation (12), regardless of the incident light intensity. The irradiation position is obtained.

(IA-IB) / (IA + IB) = [H (x) -W (x)] / [H (x) + W (x)] ... (12) In the figure, the irradiation position of the distance Lf to the irradiation position of the distance Lx To the width of the P layer, W (x) and H (x)
When Eq. (13) and (14) below are satisfied, the calculated current value has a linear relationship with the measured object distance.

W (x) = ^{[L 2 f / (Lf-Ln} ) ] - [x / (Lf · x + f · B) ] · (W-I) ...... ( 13) (13) further generally W to represent (X) is W (x) = a
/ (X + b).

However, a, b: constants H (x) = W-I-W (x) (14) For the formula (13) given by the general formula, the setting condition of the optical system is f · B = Lf. When set, Eq. (13) is transformed into Eq. (15) below.

W (x) = [Lf / (Lf-Ln)]-[x / (x + 1)]-(W-I) (15) Here, substituting in equations (8) and (14) yields equation (16). And (1
Equation (7) is obtained.

W (x) = (W−I) · [(Lf−Lx) / (Lf−Ln)] ... (16) H (x) = (W−I) · [(Lx−Ln) / (Lf−Ln) )] (17) Substituting Eqs. (16) and (17) into Eq. (12) yields Eq. (18).

(IA-IB) / (IA + IB) = 1- [2. (Lf-Lx) / (Lf-Ln)] (18) That is, the widths W (x) and H (x) of the P layer are expressed by the equation (13). When the condition of expression (14) is satisfied, the calculated current value linearly changes with respect to the measured distance Lx between the distance measuring ranges Ln and Lf according to expression (18).

FIG. 3 shows still another embodiment of the two-divided semiconductor position detector according to the present invention.

P layers 28 and 29 divided by separation layer 27 are connected to electrodes 25 and 26 via contact holes 30 and 31, respectively.

In the structure shown in FIG. 1, if the length of the slit light irradiating the light receiving surface is shorter than the width W, approximation cannot be made under the conditions of the expressions (13) and (14).

In this embodiment, the width of the basic constituent elements is narrowed, and a plurality of the constituent elements are arranged in a plane to form a pattern as shown in FIG. 3 so that the slit light can be used even if its length is shorter than W. It is a thing.

In the embodiment shown in FIG. 3, the reference measured distance is Lref, and the range is set to Lref ± 0.5 Lref.

As a result, Lf = 1.5 Lref, Ln = 0.5 Lref,
Lf-Ln = Lref and the setting condition of the optical system is fB =
If Lf = 1.5Lref is selected, equations (13) and (14) become equations (19) and (20).

W (x) = (W−I) · [1.5x / (x + 1)] ... (1
9) H (x) = (W−I) · [(1-0.5x) / (x + 1)] (20) In equation (19) and equation (20), the variable x is changed from 0 to the effective light-receiving surface length. Calculate up to C and draw.

FIG. 4 is a circuit diagram showing an embodiment of an arithmetic circuit of a rangefinder using a two-divided semiconductor position detector according to the present invention.

In this embodiment, the output of the two-divided semiconductor position detector 32 is current-voltage converted by an AC coupling method via a capacitor and then obtained from a pair of output terminals (electrodes A and B) of the two-divided semiconductor position detector. The calculation corresponding to the difference (IA-IB) and the sum (IA + IB) of the generated photocurrents is executed.

A signal extraction circuit (a detailed circuit example is shown by enclosing it in a broken line on the lower side) by the light source 1 shown in FIG. 1 (the light source 3 in FIG. 4).
The states when 4) is lit and when it is not lit are held by the two sample hold circuits, and the difference is output by the operational amplifier.

With this circuit, only the signal component can be extracted.

This signal component is calculated by the analog divider 33 and output.

The relationship between this output value and the measured distance Lx is shown in FIG.

In the circuit of FIG. 4, the sum of photocurrent values (IA + IB) is constantly monitored, and the light emission intensity of the light source 34 is controlled so that this value becomes constant, whereby the arithmetic circuit of FIG. 4 operates in a stable state. Can be made.

(Effect of the Invention) As described in detail above, the two-divided semiconductor position detector according to the present invention is used in a distance detection device of the triangulation method for detecting the incident position of the reflected light from the measured object of the projected light. In the one-dimensional semiconductor position detecting device, the resistance layer connected to the electrode on the light source side of the distance detecting device of the semiconductor position detector and the resistance layer connected to the electrode on the side opposite to the light source are insulated along a curve. Separated, the reflected light is made incident on each of the separated resistance layers, and the generated current corresponding to the incident area is taken out from both electrodes, so that the signal current having distance information proportional to the amount of change in the measured object distance. Is configured to take out.

Therefore, the calculated current value obtained from the semiconductor position detector can be linearly related to the measured distance.

Therefore, it is possible to realize an inexpensive, small-sized and lightweight distance detecting device as compared with a distance detecting device which needs to be linearly corrected by adding a conventional computer. Furthermore, since the calculated current value can be obtained only with a simple analog calculation circuit, it is possible to realize a distance detection device with high-speed response that cannot be realized via a computer.

[Brief description of drawings]

FIG. 1 is a plan view showing a first embodiment of a two-divided semiconductor position detector according to the present invention. FIG. 2 is a sectional structural view of the two-divided semiconductor position detector. FIG. 3 is a plan view showing a second embodiment of the two-divided semiconductor position detector. FIG. 4 is a circuit diagram showing an embodiment of an analog arithmetic circuit for processing the output of the two-divided semiconductor position detector. FIG. 5 is a graph showing the relationship between the measured distance and the calculated current value of the two-divided semiconductor position detector according to the present invention. FIG. 6 is a graph showing an optical system of a distance detecting device by a conventional triangulation method. FIG. 7 is a sectional structural view of a conventional semiconductor position detector. FIG. 8 is a graph of incident light position and current calculation value by the conventional semiconductor position detector. 1 ... Light source 2 ... Emitter lens 3 ... Receiving lens 4 ... Semiconductor position detector 5 ... Object to be measured 6 ... Electrode (A) 7 ... Electrode (B) 8 ………… P-type resistance layer 9 ………… N ⁺ layer 10 ………… Common electrode 11 ………… High resistance layer (i layer) 12 ………… Electrode (A) 13 ………… Electrode (B) 14 …… ... Separation layer 15 ... P layer in contact with electrode (A) 16 ... P layer in contact with electrode (B) 25 ... Electrode (A) 26 ... ... Electrode (B) 27 ... ... Separation Layer 28: P layer connected to the electrode (A) 29: P layer connected to the electrode (B) 30: Contact hole of the electrode (A) 31: Contact hole of the electrode (B) 32 ……… 2-division semiconductor position detector 33 ……… Analog divider

Claims (3)

[Claims] 1. A triangulation distance detecting device for detecting an incident position of reflected light from a measured object of projected light.
In a three-dimensional semiconductor position detector, the light-receiving surface of the semiconductor position detector is insulated and separated along a curve, electrodes are provided on each light-receiving surface, and reflected light is incident on each of the separated light-receiving surfaces, and the incident area A two-divided semiconductor position detector characterized in that a corresponding generated current is taken out from both electrodes to take out a signal current having distance information proportional to the object distance to be measured. 2. The two-divided semiconductor position detector is provided with an N ⁺ layer forming a common terminal on the back side of a silicon substrate, and a rectangular P layer serving as a light-receiving surface is insulated and separated by a separation layer on the front side.
The two-divided semiconductor according to claim 1, wherein the following relationship is established at a position x from a side of the light receiving surface on the light source side in a configuration in which a signal current extracting electrode is arranged in each P layer. Position detector. Note H (x) + W (x) + I = W W (x) = ax / (x + b) where W: width of semiconductor position detector I: length of separation layer in width direction H (x): light reception on light source side Length in the width direction of the surface W (x): Length in the width direction of the light receiving surface on the other side a, b: Constant 3. The two-divided semiconductor position detector according to claim 2, wherein the constants a and b are given by the following expressions. Note a = Lf (W-1) / (Lf-Ln) b = (f · B) / Lf Ln: Short-distance side distance measurement limit Lf: Long-distance side distance measurement limit B: Base line length f: Light receiving lens and detection Distance between vessels (imaging distance)