JPH0613968B2 - Semiconductor position detector - Google Patents

Description

TECHNICAL FIELD The present invention relates to a semiconductor position detector that receives light from an object to be measured as a light spot and detects the position of this light spot.

[Conventional technology]

Conventionally, there is known an active distance detection device that projects light from a light source onto an object to be measured, receives reflected light from a semiconductor position detector provided at a position separated from the light source by a certain distance, and detects the distance to the object to be measured. Has been.

FIG. 4 is an explanatory diagram of an optical system of such a distance detecting device.
As shown in the figure, the light from the light source 1 such as a light emitting diode (LED) is irradiated onto the DUT 3 via the condenser lens 2. The reflected light from the DUT 3 is condensed by the light receiving lens 4 and is incident on the light receiving portion (not shown) of the semiconductor position detector 5 as a light spot. Here, the baseline length is set to B, and the measured object 3
Is L, the distance between the light receiving lens 4 and the semiconductor position detector 5 (image forming distance) is f, and the light point position on the semiconductor position detector 5 from the optical axis of the light receiving lens 4 (concentration center position) S
When the distance to P (the amount of movement of the spot light) is x, the following (1) is established.

x = (f · B) / L ...
(1) Therefore, if the values of x, f, and B are known in FIG. 4, the distance L to the DUT 3 can be obtained.

FIG. 5 is a detailed sectional configuration diagram of the one-dimensional semiconductor position detector 5 shown in FIG. As shown, the high resistance intrinsic (i
A p-type resistance layer 52 in which p-type impurities are uniformly diffused is formed on the surface side of a (type) silicon substrate 51 to form a light receiving portion as a pn junction diode. In addition, on the back surface side of the silicon substrate 51, n ⁺ which is a high concentration of n-type impurities diffused
A mold conductive layer 53 is formed, and an electrode 54 is in ohmic contact with this. A pair of signal extraction electrodes 55a and 55b are arranged at both ends of the p-type resistance layer (light receiving portion) 52 on the front surface side, and the currents I _A and I _B are taken out from there.

Now, it is assumed that the light from the DUT 3 is incident on the position SP on the p-type resistance layer 52 as a light spot, and the position SP is separated from the electrode 55a by the distance x. Also, the electrodes 55a, 5
5b is C, the resistance value of the p-type resistance layer 52 between them is R _C , the resistance of the p-type resistance layer 52 between the position SP and the electrode 55a is R _x , When the generated photocurrent is I _O , the following equations hold for the currents I _A and I _B.

In _{I A = I O · (R} C -R x) / R C I B = I O · R x / R C ... (2) where the resistance value of the p-type resistive layer 52 from proportional to its length, The above equation (2) becomes the following equation (3).

I _A = I _O · (C−x) / C I _B = I _O · x / C (3) Therefore, from the above formula (3), (I _A −I _B ) / (I _A + I _B ) = 1-2x / C ...
(4) is obtained, the current I can be obtained regardless of the intensity of incident light.
_A, it is possible to calculate the incident position SP of the light from the value of I _B.

FIG. 6 is a diagram showing a distance detecting optical system when the distance measuring range is set from L _N to L _F. The luminous flux of the light source 1 is condensed by the condensing lens 2 to irradiate the DUT 3. The reflected light from the DUT 3 is condensed by the light receiving lens 4 which is arranged at a distance of the base line length B from the condensing lens 2. The semiconductor position detector 5 is arranged at a light collecting position (light spot position) at a distance f from the light receiving lens 4.

Here, the closest distance (limit on the short distance side) and the farthest distance (limit on the long distance side) in the distance measuring range are L _N and L _F , respectively, and the distance to the DUT 3 is L. The distance a distance from the optical axis of the light receiving lens 4 to the one end of the light receiving portion of the semiconductor position detector 5 and x _F, to the other end x
_{Let N} be the distance from the light spot position SP at which the reflected light from the DUT 3 is condensed by the light receiving lens 4 to the optical axis of the light receiving lens 4, and let x be the semiconductor position detector 5 from the light spot position SP.
When the distance to _one end of the light receiving portion of is x ₁ and the length of the light receiving portion of the semiconductor position detector 5 (interval between a pair of electrodes) is C, the following relational expressions hold.

x _N = C + x _F = f · B / L _N (6) Therefore, the following equation (7) can be obtained from the above equations (5) and (6).

Further, in FIG. 6, a relational expression of x ₁ = x−x _F = f · B (1 / L−1 / L _F ) ... (8) is also obtained.

Next, the position resolution of the semiconductor position detector 5 is Δx and the distance L is
The distance resolutions at _N and L _F are ΔL _N and Δ, respectively.
And L _F, the relationship between _{L N} and _{L F L F / L N =} m
When expressed by (9), the following relational expression is obtained.

_{Δx + x N = f · B} / (L N -ΔL N) ... (11) Δx + x F = f · B / (m · L N -ΔL F) ... (12) (11) formula and from (12), the distance The resolutions ΔL _N and ΔL _F are as shown in equations (13) and (14), respectively.

_{ΔL N = Δ x · ▲ L} 2 N ▼ / (Δ x · L N + f · B) ... (13) ΔL F = m 2 · Δ x · ▲ L 2 N ▼ / (m · Δx · L N + f · B)
(14) When the ratios of the equations (13) and (14) are taken, the following (1
Equation 5) is obtained.

ΔL _F / ΔL _N = m ² · (Δx · L _N + f · B) / (m · Δx · L _N + f · B)
(15) In the equation (15), when the condition of m · Δx · L _N << f · B is satisfied, this can be approximated to the following equation (16).

ΔL _F / ΔL _N ≈m ² (16) From the equation (16), it can be seen that the distance resolution ΔL _F on the far distance side is significantly deteriorated when m shown in the above equation (9) is large.

In other words, if the range from the shortest measurable distance to the farthest measurable distance is increased, the resolution at such a long distance decreases. For this reason, for example, a position detection device that is expected to have high resolution on the short distance side, such as position detection in the processing section of a laser processing machine, can be used on the long distance side such as position detection in running an automated guided vehicle. When applied to a device that requires a high resolution, there is a drawback that the desired resolution cannot be obtained.

Therefore, according to the present invention, the ratio of the far and near limit distances (L _F / L _N =
It is an object of the present invention to provide a semiconductor position detector applicable to a distance detecting device having a wide distance measuring range and capable of obtaining high distance resolution on the long distance side even if m) is increased.

[Means for solving problems]

The semiconductor position detector according to the present invention, when the light from the object to be measured is incident as a light spot on the light receiving portion formed on the surface side of the high-resistance semiconductor substrate containing one conductivity type impurity, A semiconductor position detector that detects the position of the light spot in the light receiving part based on the photocurrent taken out from the signal extraction electrodes arranged at both ends of the part, and the light receiving part is configured as follows. Characterize. That is, it includes a plurality of light receiving areas in which each pair of signal extraction electrodes is arranged at both ends, and the plurality of light receiving areas are arranged in a line so that one and the other of each pair of signal extraction electrodes are adjacent to each other, and The intervals between the signal extraction electrodes in the plurality of light receiving areas are successively equal to each other. Further, the light receiving section is characterized in that in addition to the above-mentioned light receiving area, one auxiliary light receiving area is provided outside both ends thereof, and each auxiliary light receiving area has one signal extraction electrode.

[Action]

According to the configuration of the present invention, the light from the object to be measured on the far distance side and the light from the object to be measured on the near distance side are incident on different light receiving areas as light spots, and accordingly, each photocurrent is received by each light receiving area. It is output from the signal extraction electrode of the area. Further, the light that has deviated to the outside of the light receiving areas at both ends is incident on the auxiliary light receiving area and is also output from the signal extraction electrode.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail 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 perspective view of a semiconductor position detector according to an embodiment, FIG. 2 (a) is a plan view thereof, and FIG. 2 (b) is a longitudinal sectional view thereof. The characteristic of this compared with the conventional one is that the light receiving portion formed on the front surface side of the semiconductor substrate is
This means that a plurality of light receiving areas and two auxiliary light receiving areas are arranged in a row. n (n is an integer of 2 or more) light receiving areas 52 _{1 to} 52 _n and two auxiliary light receiving areas 52
₀ and 52 _{n + 1} are formed by uniformly diffusing P-type impurities on the surface side of the high-resistance silicon substrate 51.
The lengths of the light receiving areas 52 _{1 to} 52 _{n in} the longitudinal direction are sequentially increased. Then, each of the light receiving areas 52 _{1 to} 52
_n across each pair of signal extraction electrodes _55a 1 _{~55a n} was sufficiently narrow width to the, the _55b 1 _{~55b n} is arranged,
Length C of P-type resistance layer (light receiving area) between a pair of extraction electrodes
The _{1 ~C n C 2 / C 1} = C 3 / C 2 = ... n / C n-1 = D ( constant)
The relationship of (17) is established. In addition, each signal extraction electrode 55a ₁
～55A _n, the width W of _55b 1 _{~55b n} is assumed to be sufficiently narrow to the extent that can be regarded as a W _{"C 1.} On the other hand, one signal extraction electrode 55a ₀ , 55b ₀ is also provided at the outer end of each of the two auxiliary light receiving areas 52 ₀ , 52 _{n + 1} , and their widths are sufficiently narrow as in the above case. Has become.

The distance measuring range is divided into n, and L ₁ , L ₂ , L ₃ ,
Assuming that L ₄ , ... L _n , when the semiconductor position detector 5 satisfies the above equation (17), the following equation (18) holds.

_{L 1 / L 2 = L 2} / L 3 = L 3 / L 4 = ... = L n-1 / L n = D ( constant)
(18) A characteristic of the present invention is that the light receiving areas 52 _{1 to} 5 5
The auxiliary light receiving areas 52 ₀ and 52 _{n + 1} are provided outside 2 _n , which is different from Japanese Patent Application No. 62-174225 filed by the present applicant in this respect. The reason for doing this will be described below.

The size of the spot light focused on the light receiving portion of the semiconductor position detector by the light receiving lens 4 is ideally infinitely small, but in reality, it is a finite size. Therefore,
When the spot light reaches the end of the light receiving area 52 ₁ or 52 _n of the semiconductor position detector shown in FIG. 1 and FIG. 2, the signal light out of the light receiving area 52 ₁ or 52 _n is not photoelectrically converted, Only the signal light applied to this light receiving area is photoelectrically converted. As a result, the signal light current obtained from the signal extraction electrode 55b ₁ or 55a _n is reduced, operation output after running a predetermined analog division has a small amount of change its output value with respect to the distance variation Become. In other words, when the spot light comes to the end of the light receiving area 52 ₁ or 52 _n , the distance resolution deteriorates.

In order to improve this drawback, in FIG. 1, the semiconductor position detector of the present invention has an auxiliary light receiving area 5 at both outermost ends.
2 ₀ and 52 _{n + 1} is formed. The signal light applied to the auxiliary light receiving areas 52 ₀ and 52 _{n + 1} is photoelectrically converted and taken out from the signal taking-out electrodes 55b ₀ and 55a ₀ . Then, the photocurrent obtained from the signal extraction electrode 55b ₀ or 55a ₀ is added to the photocurrent obtained from the signal extraction electrode 55b ₁ or 55a _n by an adding circuit described later, and then the calculation by the analog divider is executed. It As a result, the distance resolution in this portion (far / near side) is significantly improved.

In the amplifier circuit connected to the semiconductor position detector 5, the light incident on the semiconductor position detector 5 includes ambient light (for example, sunlight) as well as signal light. In this case, it is common to use an AC coupling method using a current-voltage conversion resistor and a capacitor (see "Semiconductor Position Detector Catalog" P.14 issued by Hamamatsu Photonics KK). At this time, due to the difference in the temperature characteristics of the inter-electrode resistance R _C of the semiconductor position detector 5 and the current-voltage conversion resistance, an error occurs in the signal calculation output shown in the above equation (4). Therefore, the electrodes _55a 0 _{~55a n} on high-resistance silicon substrate 51 of the semiconductor position detector 5 shown in FIG. 1, a current close to _55b 0 _{~55b n} - voltage converting resistor (not shown) By forming the resistors and aligning the temperature characteristics of the resistors, the error in the signal calculation output can be eliminated.

FIG. 3 is a block diagram of the semiconductor position detector 5 of the present invention and a signal processing circuit dedicated thereto. In this embodiment, the light receiving portion of the semiconductor position detector 5 completely 5 divided by the isolation layer 58 _{0-58 3,} the relationship of the aforementioned equation (17) is set to the following values.

C ₂ / C ₁ = C ₃ / C ₂ = 2 (19) Along with this, the division of the distance-measuring range becomes the following numerical value from the above-mentioned formula (18).

L ₁ / L ₂ = L ₂ / L ₃ = 2 (20) Each of the light receiving areas 52 _{1 to} 52 on the semiconductor position detector 5.
₃ signal extraction electrodes 55a _{1 to} 55a ₃ and 55b _{1 to} 55
The current-voltage conversion resistor r is formed in contact with b ₃ , and the signal extraction electrodes 55 of the auxiliary light receiving areas 52 ₀ and 52 ₄ are formed.
A resistor r for current-voltage conversion is formed in contact with a ₀ and 55b ₀ . Photocurrents I ₁ , I _B1 , I _A1 , I _B2 , I _A2 , I _B3 , I _A3 and I ₃ obtained by the incidence of light
Is converted into a voltage by this current-voltage conversion resistor r,
Only AC components are AC-coupled by the capacitor C and sent to the amplifiers U _{1 to} U ₈ , and after amplification, the adder circuits U _{9 to} U ₁₃
Transferred to.

The adder circuit U ₉ calculates the sum of AC components in the photocurrents I ₁ and I _B1 obtained when light is incident on the auxiliary light receiving area 52 ₀ and the light receiving area 52 ₁ of the semiconductor position detector 5. This addition corrects the decrease in the photocurrent I _B1 when the incident spot light deviates from the light receiving area 52 ₁ toward the auxiliary light receiving area 52 ₀ . Similarly, the light current I addition circuit U ₁₃ is obtained from the auxiliary light receiving area 52 ₄ and the light receiving area 52 _3
3 , the sum of the AC components of I _A3 is calculated. By this addition,
Decrease in the photocurrent I _A3 when the incident light spot is deviated in the auxiliary light receiving area 52 ₄ side from the light receiving area 52 ₃ is corrected. On the other hand, the adder circuits U ₁₀ , U ₁₁ and U ₁₂ are provided in the light receiving area 52.
_{1, 52} 2, 52 ₃ obtained from the optical current I _B1 ~I _B3, I
The sum of the AC components of _{A1 to} I _A3 is calculated. Furthermore, the amplifier U ₃
And the output of the adder circuit U ₁₁ is given to the adder circuit U ₁₄ ,
Similarly, the outputs of the amplifiers U ₄ , U ₅ , and U ₆ and the adder circuit U ₁₀ ,
The outputs of U ₁₂ and U ₁₁ are given to adder circuits U ₁₅ , U ₁₆ and U ₁₇ , respectively.

The outputs of the adder circuits U _{10 to} U ₁₂ are given to the sample and hold circuits U _{18 to} U _20, and the signal level of the light reflected from the DUT 3 when the light source 1 is pulsed is held. . The sampling signal at this time is the symbol in FIG.
Indicated by ₂ . Sample and hold circuit U _{18 to} U
The outputs of ₂₀ are averaged by the filter circuits U _{21 to} U ₂₃ .
Then, the outputs of the filter circuits U _{21 to} U ₂₃ are output to the comparison circuit U _24.
To U ₂₆ , where the signal light reflected from the device under test 3 is received by the light receiving areas 52 _{1 to} 5 5 of the semiconductor position detector 5.
It is determined which of the light receiving areas of 2 ₃ is most strongly hit, and the result is determined by the gate signals G ₁ , G ₂ and G _3.
Is output from the AND gate.

Here, for example, when an optical signal is incident on the light receiving area 52 ₁ , the gate signal G ₁ becomes “H” (high level) and the gate signals G ₂ and G ₃ become “L” (low level). . The gate signals G ₁ , G ₂ and G ₃ turn on the signal line from the light receiving area where the signal light is most strongly incident in the gate circuit 22, and the output thereof is sent to the subtraction circuit 23 and the addition circuit 24. That is,
ON / OFF of the signal line in the gate circuit is controlled in the form of active high (ON state when the gate signal becomes “H”) as described below.

A photocurrent I _A1 obtained from the adder circuit U ₁₄ signal extraction electrodes 55a ₁ of the light receiving area 52 ₁ for position detection in the sum I _B2 + I photocurrent obtained from the light receiving area 52 ₂ for position detection
Addition with _A2 is executed. As a result, the gate signal G1
Is “H” and the center of the spot light is near the separation layer 58 ₁ , the spot light deviated from the light receiving area 52 ₁ is photoelectrically converted in the adjacent light receiving area 52 ₂ , and the signal light current I _A1 The decrease can be corrected by I _B2 + I _A2 .

Receiving area center position of the spot light from the separating layer 58 ₁ 5
When slightly moves to 2 _second direction, the gate signal G1 becomes "L", the gate signal G2 becomes "H". At this time, the signal light that has deviated from the light receiving area 52 ₂ (a decrease in the photocurrent I _B2 obtained from the signal extraction electrode 55 b ₂ ) is the sum I _{B1 of the} signal light currents that are photoelectrically converted in the adjacent light receiving area 52 _1. Corresponding to + I _A1 , therefore, by performing addition (I _B1 + I _A1 ) + I _B2 by the addition circuit U _15, it is possible to perform correction of the decrease in I _B2 . For the same reason, the addition circuits U ₁₆ and U ₁₇ can perform the correction of the reduction of the signal values of I _A2 and I _B3 , respectively. Here, if the adder circuits U ₉ and U ₁₃ and the adder circuits U _{14 to} U ₁₇ are taken out,
Since the reduction amount of the signal current is not corrected at the switching position of each of the divided distance measuring ranges, the amount of change in the arithmetic output value of the analog divider 26 with respect to the amount of change in distance becomes small and the distance resolution deteriorates. It will be.

The addition circuits U ₉ and U ₁₃ and the addition circuits U _{14 to} U ₁₇ correct the signal current, and the gate circuit 22 turns ON the signal line.
After the OFF control is performed, the subtraction circuit 23 and the addition circuit 2
4, the subtraction and addition of signals are executed and the operation output thereof is given to the signal component extracting circuit 25, where only the signal component superimposed on the disturbance light component is extracted. Here, the voltage level immediately before the light source is pulsed is recorded by the sampling signal _1, and the voltage level at the time of pulse lighting is recorded by the sampling signal ₂ . The signal component is extracted by taking the difference between the two recorded values. The output of the signal component extracting circuit 25 is given to the analog divider 26, where an arithmetic operation is executed and output in the form of an analog voltage. As a result, the gate signals G ₁ , G
The output state of ₂ and G ₃ reveals where the object to be measured exists in the distance measuring range divided into three, and the accurate distance to the object to be measured 3 can be obtained by the analog voltage output.

Although not shown in the figure, of the output values of the signal component extracting circuit 25, the signal level of I _A + I _B is monitored, and a drive circuit (not shown) on the light source 1 side is provided so that this voltage level becomes constant. Control), the analog divider 2
The calculation accuracy of 6 can be improved.

Next, the above embodiment will be described in more detail with specific numerical values.

First, the optical conditions of the distance measuring device of the embodiment are set as follows.

f = 60 [mm] B = 200 [mm] L _N3 = 750 [mm] L _F3 = L _N2 = 1500 [mm] L _F2 = L _N1 = 3000 [mm] L _F1 = 6000 [mm] L _F1 / L _N1 = 2 C1 = f · B (1 / L _N1 −1 / L _F1 ) = 2 [mm] Δx = C1 / 500 = 4 [μm] The resolution of the semiconductor position detector 5 is the signal photocurrent based on the incident light. It varies depending on the magnitude, but the sum of the general signal photocurrent _(I a ₊ I _B) is at 300 [nA], the resolution Δx is about 1/500 of the electrode spacing. Therefore, Δx = C1 / 5
00 is calculated. Substituting the above numerical values into the above equation (14), the distance resolution ΔL _F of the farthest distance is as follows.

ΔL _F ≈12 [mm] (19) On the other hand, when the conventional semiconductor position detector is used in the same optical system, the distance resolution of the farthest distance is similarly obtained as follows.

_{f · B = 12000 L N =} 750 (mm) L _F = 6000 [mm] _{L F / L N = 8 C} = f · B (1 / L N -1 / L F) = 14 [mm] [Delta] L _F = 83 [mm] (20) Then, comparing equations (19) and (20), in this embodiment, the distance resolution on the far distance side is higher than that when the conventional semiconductor position detector is used. Even with the same optical system, it is improved about 7 times. This effect can be further improved by increasing the number of divisions of the light receiving portion of the semiconductor position detector (the number of light receiving areas).

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

For example, regarding the application of the present invention to a distance detector,
It is not limited to that shown in the figure. Further, the semiconductor substrate is not limited to silicon, and may be gallium arsenide (Ga).
As) makes it possible to use even under higher temperature conditions.

〔The invention's effect〕

As described above in detail, according to the present invention, the light from the object to be measured on the far side and the light from the object to be measured on the short distance side are incident on different light receiving areas as light spots, and thus each light Since the current is output from the signal extraction electrode of each light receiving area, the ratio of the far and near limit distances (L _F / L _N =
Even if m) is increased, it is possible to obtain a semiconductor position detector applicable to a distance detection device having a wide distance measurement range that can obtain high distance resolution on the far side. Further in the present invention,
Auxiliary light-receiving areas are provided outside the light-receiving areas on both ends, and this photocurrent can be used to compensate for the decrease in the photocurrent in the light-receiving areas on both ends. There is an effect that can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a semiconductor position detector according to an embodiment of the present invention, FIG. 2 is a plan view and a vertical sectional view of the semiconductor position detector shown in FIG. 1, and FIG. FIG. 4 is a block diagram of an essential part of a distance detecting device to which the semiconductor position detector of the present invention is applied, FIG. 4 is an explanatory view of an optical system of the distance detector, FIG. 5 is a sectional view of a conventional semiconductor position detector, and FIG. The figure is an explanatory view of the optical system for distance detection when the distance measuring range is changed from L _N to L _F. DESCRIPTION OF SYMBOLS 1 ... Light source, 2 ... Condensing lens, 3 ... DUT, 4 ... Light receiving lens, 5 ... Semiconductor position detector, 22 ... Gate circuit, 23
... subtraction circuit, 24 ... addition circuit, 25 ... signal component extraction circuit, 26 ... analog divider, 51 ... silicon substrate, 52
... Light receiving part (P-type resistance layer), 52 ₀ ... Auxiliary light receiving area, 5
2 _{1 to} 52 _n ... Light receiving area, 52 _{n + 1} ... Auxiliary light receiving area, 53 ... N ^{+ type} conductive layer, 55 a, 55 a _{0 to} 55
a _n , 55b, 55b _{0 to} 55b _n ... Signal extraction electrode, U
₁ ~U 8 _{... amplifier,} U 9 ~U ₁₇ ... adder circuit, U ₁₈ ~U ₂₀
... sample and hold circuit, U ₂₁ ~U ₂₃ ... filter circuit, U ₂₄ ~U ₂₆ ... comparison circuit (comparator).

Claims (4)

[Claims] 1. A light-receiving portion formed on the front surface side of a high-resistance semiconductor substrate containing an impurity of one conductivity type, and arranged at both ends of the light-receiving portion when light from a DUT is incident as a light spot. In a semiconductor position detector for detecting the position of a light spot in the light receiving section based on a photocurrent taken out from a signal taking-out electrode provided, the light receiving section has a plurality of pairs of signal taking-out electrodes arranged at both ends. Light receiving areas, the plurality of light receiving areas are arranged in a line so that one and the other of the pair of signal extracting electrodes are adjacent to each other, and the intervals of the signal extracting electrodes of the plurality of light receiving areas are sequentially arranged. Further, the light receiving section includes at least two auxiliary light receiving areas each having at least one signal extraction electrode,
The semiconductor position detector, wherein the auxiliary light receiving area is provided outside both ends in the arrangement direction of the light receiving area. 2. The light receiving section is divided into the plurality of light receiving areas and auxiliary light receiving areas via a separation layer formed on the semiconductor substrate. Semiconductor position detector. 3. The semiconductor position detector according to claim 1, wherein the signal extraction electrode is grounded via a resistor for current / voltage conversion. 4. The semiconductor position detector according to claim 3, wherein the current / voltage conversion resistor is a diffusion resistor formed by implanting impurities into the semiconductor substrate.