JPH0642964A - Displacement sensor - Google Patents

Abstract

PURPOSE:To obtain a displacement sensor wherein a distance can be found accurately by inputting a signal at an optimum level to an operation means. CONSTITUTION:A light-projecting element 11 forms a lot-like optical pattern on the surface of an object 3. Reflected light on the surface of the object 3 is incident on a position sensor 21 composed of a PSD through a photodetection optical system 22. After the output signal of the position sensor 21 has been amplified by amplification circuits 24a, 24b, it is input to a judgment part 25 and a distance up to the object 3 can be found. The judgment part 25 regulates the level of the output signal of a drive part 14 and the amplification degree of the amplification circuits 24a, 24b so that the level of an input signal can be kept nearly within a prescribed range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement sensor for optically measuring a distance to an object by using a triangulation method.

[0002]

2. Description of the Related Art Conventionally, as a displacement sensor which can measure a distance to an object in a non-contact manner, a sensor which optically measures a distance based on a triangulation method has been put to practical use because of its relatively simple structure. ing. Generally, in this type of displacement sensor, as shown in FIG. 7, a light beam is emitted from the light projecting means 1 onto the object 3 to form a light projection spot, which is a point-like light pattern, on the surface of the object 3. The reflected light of the light beam emitted from the light projecting means 1 on the surface of the object 3 is detected by the light receiving means 2. In the light receiving means 2, the incident light is passed through the light receiving optical system 22 to be converged so that the PS
A light receiving spot as an image of the light emitting spot is formed on the light receiving surface of the position sensor 21 such as D, and a pair of position signals I ₁ and I ₂ capable of specifying the position of the light receiving spot are output. That is, since the position sensor 21 generates a pair of position signals I ₁ and I ₂ which are current signals whose ratio is determined according to the position of the light receiving spot, the position sensor 21 detects the light receiving spot based on the relationship between the two position signals I ₁ and I ₂ . If the position is detected, the object 3
The distance to can be calculated based on the triangulation method.

A more specific description will be given. The light projecting means 1 is
A light emitting element 11 such as a semiconductor laser is provided, and the light output from the light emitting element 11 is passed through a light projecting optical system 12 to form a light beam. Further, the light emitting element 11 is the driving unit 1.
Driven by a modulation signal of a predetermined frequency from the modulation signal generation unit 13 through 4, the modulation signal generation unit 13 generates a modulation signal for modulating the energization current to the light emitting element 11.

On the other hand, the pair of position signals I ₁ and I ₂ output from the position sensor 21 are converted into voltage signals through the current-voltage conversion circuits 23a and 23b, respectively. The respective voltage signals are amplified respectively through amplification circuits 24a and 24b which are amplification means, and then input to the judgment section 25 which is calculation means as distance measurement signals V ₁ and V ₂ and output signals corresponding to the distance to the object 3. Z is generated.

By the way, P used as the position sensor 21
SD is a light receiving element having a pin structure and having output electrodes at both ends in the longitudinal direction, and a current source is connected to the n layer. When the light-receiving spot is irradiated on the light-receiving surface of the p-layer, a current flows through the insulating layer, whereby the p-layer, which is a high resistance layer, is divided according to the irradiation position of the light-receiving spot, and the current I supplied from the current source is The position signals I ₁ and I ₂ , which are current signals, are taken out from the respective output electrodes by being divided so as to correspond to the division ratio of the p layer. That is, the position signals I ₁ and I ₂ output from each output electrode have the total resistance between the output electrodes as Zs, and the distance between the output electrode that outputs the position signal I ₁ and the light receiving spot and the position signal If the ratio of the distance between the output electrode that outputs I ₂ and the light receiving spot is Z ₁ : Z ₂ , then I ₁ = (Z ₂ / Zs) · I (1) I ₂ = (Z ₁ / Zs) · I (2) On the other hand, as shown in FIG. 8, when the light receiving spot is located at the center of the light receiving surface of the position sensor 21, the distance from the center of the projection optical system 12 to the object 3 is Rc, and the distance to the object 3 is Suppose that it has become smaller by Δr. At this time, the position of the light receiving spot moves downward by Δx in FIG. If the effective length of the light-receiving surface of the position sensor 21 is 2L, then Z ₁ : Z ₂ = (L + Δx) :( L−Δx) (3) Therefore, the formulas (1), (2) and (3) From the formula, the following formula is obtained.

I ₁ / I ₂ = (L−Δx) / (L + Δx) ∴Δx = − {(I ₁ −I ₂ ) / (I ₁ + I ₂ )} · L (4) Further, the center of the light receiving optical system 22 and the position sensor 21
Is f, and the angle formed by the straight line connecting the point at the position of distance Rc on the optical axis of the projection optical system 12 and the center of the position sensor 21 with the optical axis of the projection optical system 12 is θ, We have the following relationship:

(Rc-Δr) / cos θ: f / cos θ = Δr · tan θ: Δx Δx = f · tan θ · Δr / (Rc-Δr) = a · Δr / (b-Δr) ∴Δr = b · Δx / (a + Δx) (5) where a = f · tan θ and b = Rc. That is,
If Δx is obtained, the displacement distance Δ of the object 3 is calculated by the equation (5).
It is possible to obtain r.

On the other hand, the position signals I ₁ and I ₂ are amplified by the amplifier circuit 24.
Since the distance measurement signals V ₁ and V ₂ obtained through a and 24b are proportional to the signal values of the position signals I ₁ and I ₂ , the conversion ratio of the current-voltage conversion and the amplification of each amplifier circuit 24a and 24b. If the coefficients for the position signals I ₁ and I ₂ including degrees are set as A ′ · A and A, the following equation is obtained. V ₁ = A ′ · A · I ₁ (6) V ₂ = A · I ₂ (7) Further, according to the formulas (6) and (7), the position signals I ₁ and I are calculated from the formula (4).
By eliminating ₂ , we can obtain Δx = − {(V ₁ / A ′) − V ₂ ) / (V ₁ / A ′) + V ₂ )} · L (8) Therefore, the equation (8) is substituted into the equation (5) and modified. Then, the following equation is obtained.

Δr = {B · V ₁ / (κ · V ₁ + V ₂ )} + C (9) where κ = {(a−L) / (a + L)} (1 /
A ′), B = {2abL / (a + L) ² } (1 /
A ′) and C = −bL / (a + L). At the time of the calculation in the judging section 25, the equation (9) is corrected. At the time of the correction, the scale of the actual measurement value of the distance and the scale of the output signal Z are matched (the actual measurement dimension is (When the value of output signal Z changes by 1 when it changes by 1)
The equation (9) is multiplied by the constant D, and the constant E is added to the equation (9) so that the measured value of the distance matches the output signal Z. That is, equation (9) is transformed as follows.

Z = D · Δr + E = D [{B · V ₁ / (κ · V ₁ + V ₂ )} + C] + E = g · V ₁ / (κ · V ₁ + V ₂ ) + offset (10) g = D · B and offset = D · C + E. After all, when actually measuring the distance to the object 3, three correction parameters κ, g, of of the distance measurement signals V ₁ and V ₂ are measured.
Determine fset. Equation (10) is V ₁ / (κ · V ₁ +
V ₂ ) is a linear expression, and the correction parameter g, which is the slope of the linear expression, is a coefficient for matching the unit size of the distance of the object 3 with the unit of the signal value of the output signal Z, and the intercept of the linear expression. The correction parameter offset, which is, is an offset value for matching the measured distance to the object 3 with the signal value of the output signal Z. Further, the correction parameter κ is a coefficient for correcting an error due to factors such as an aberration of the light receiving optical system 22, an error in position, an error in amplification degree of the amplifier circuits 24a and 24b, and the like.

The above-mentioned three correction parameters κ, g, of
fset is measured before the distance is calculated by the determination unit 25.
It is determined by comparing the measured value of the distance with the signal value of the output signal Z. Correction parameters κ, g, offs
Since there are three et, if the distance to the object 3 is set in three steps and the simultaneous ternary equations obtained based on the measured values of each distance and the obtained ranging signals V ₁ and V ₂ are solved. The correction parameters κ, g, offset can be determined.

By the way, the objects 3 whose distance is to be measured include those having a glossy surface such as metal and those having a black surface, and the diffuse reflectance differs greatly depending on the type of the object 3. Therefore, the amount of received light that enters the position sensor 21 changes significantly depending on the type of the object 3. That is, the current-voltage conversion circuits 23a, 23
b, a large dynamic range is required for the amplifier circuits 24a and 24b, the determination unit 25, and the like. However, if the design is made so as to secure a sufficient dynamic range, the manufacturing cost will be extremely high, and therefore the dynamic range is currently kept at a practical level.

Therefore, the amplification degrees of the amplifier circuits 24a and 24b are set in a plurality of steps so that the input dynamic range of the judging section 25 can be suppressed and the distance measuring signals V ₁ and V ₂ of optimum levels can be input. It is conceivable to provide an amplification degree adjusting means that can do this.

[0014]

By the way, when adjusting the amplification factors of the amplifier circuits 24a and 24b as described above, it is necessary to determine the above-mentioned correction parameters κ, g and offset for each of the settable amplification factors. Will be required. That is, as is clear from the derivation process of the equation (10) including the correction parameters κ, g and offset, the correction parameters κ and g are 2
Including the amplification ratio A'of the individual amplifier circuits 24a and 24b,
Since the value of the correction parameter offset is affected by the correction parameters κ and g, all the correction parameters κ, g and of
It can be seen that fset changes according to the amplification ratio A'of the amplifier circuits 24a and 24b. Further, since all the correction parameters κ, g, and offset are related to the optical characteristics (that is, including a and b defined by the equation (5)), they are affected by the optical characteristics. . That is, if the amplification degree of the amplifier circuits 24a and 24b is adjusted, the amplification degree ratio A '
Since there is a possibility that the correction parameter κ,
It is necessary to determine g and offset.

However, if an object 3 having a standard diffuse reflectance is used and the correction parameters κ, g, and offset for each amplification degree are to be obtained by measuring the distance, depending on the set amplification degree. There arises a problem that the correction parameters κ, g, and offset cannot be accurately obtained. For example, correction parameters κ, g, offset
When the amplification factor is set to be smaller than the optimum amplification factor for obtaining the distance, there is a problem that the level difference between the distance measurement signals V ₁ and V ₂ and noise becomes small and the distance cannot be accurately obtained. Occurs. On the contrary, when the amplification degree is set to be larger than the optimum amplification degree, the amplification circuit 24
The outputs of a and 24b are saturated and the correction parameters κ, g, of
There is a problem that fset cannot be obtained accurately.

In order to solve such a problem, the standard object 3 used for obtaining the correction parameters κ, g, and offset is changed according to the amplification degree of the amplifier circuits 24a and 24b, or a plurality of types having different transmittances are used. It is conceivable to adjust the received light amount of the position sensor 21 according to the amplification degree by using the neutral density filter 15 of FIG. However, when the standard object 3 is replaced, the distance to the object 3 may be displaced, and the reference distance may vary depending on the amplification degree. Further, even when the neutral density filter 15 is replaced, the reflection of light is changed. The refraction and the refraction substantially change the distance to the object 3, and the reference distance varies. Therefore, the correction parameters κ, g, and offset cannot be accurately obtained, and even the same object 3 may have a disadvantage that the measurement value changes only by changing the amplification degree. Further, if the standard object 3 or the neutral density filter 15 is replaced, there is a problem that it takes time to determine the correction parameters κ, g, and offset.

Further, when measuring the distance to the object 3, if the output level of the light beam of the light projecting means 1 is set so as to match the object 3 having a large diffuse reflectance,
Since the amount of light received by the position sensor 21 becomes very small when the distance is obtained for the object 3 having a very small diffuse reflectance, even if the amplification degree of the amplifier circuits 24a and 24b is adjusted, the inside of the amplifier circuits 24a and 24b is adjusted. There is a problem that the difference between the noise level and the signal level cannot be made sufficiently large, and as a result, the correction parameters κ, g, and offset cannot be accurately obtained.

An object of the present invention is to solve the above problems and to provide a displacement sensor capable of accurately obtaining a distance by inputting a signal of an optimum level to a computing means. Is.

[0019]

According to a first aspect of the invention, in order to achieve the above object, a light projecting means for irradiating a surface of an object with a light projecting spot, which is a point-like light pattern, and a light projecting means. A pair of output levels that change the output level ratio according to the position of the light receiving spot formed as an image of the light emitting spot by receiving the reflected light of the light emitted to the object and the total output level changes according to the received light amount. In a displacement sensor equipped with a light receiving unit for outputting a position signal, an amplifying unit for amplifying each position signal, and a calculating unit for calculating a distance to an object based on the output of the amplifying unit, the amplification degree of the amplifying unit is The amplification degree adjusting means for adjusting and the intensity adjusting means for adjusting the irradiation intensity of the projected spot are provided.

According to a second aspect of the present invention, the calculating means obtains the distance to the object by performing a correction calculation applying a predetermined correction parameter to the signal value of the output of the amplifying means, and the calculating means A parameter setting unit that determines the correction parameter using the measured distance value and the calculated value by the calculation unit is provided, and the amplification degree adjustment unit and the intensity adjustment unit can set the amplification degree and the irradiation intensity in a plurality of steps, respectively. The correction parameter setting means sets the product in two stages with a plurality of combinations in which the product of the amplification degree and the irradiation intensity is constant using a standard object, and outputs the signal of the output of the amplification means for each combination. The value is obtained, and the signal value of the output of the amplifying means for the combination of the amplification degree and the irradiation intensity not measured based on the obtained signal value of the output of the amplifying means is estimated, and Than is obtaining the correction parameters in the measurement of the distance by adjusting the amplification degree and the irradiation intensity and constant Zui.

According to another aspect of the present invention, the calculating means obtains the distance to the object by performing a correction operation applying a predetermined correction parameter to the signal value of the output of the amplifying means, and the calculating means A parameter setting unit that determines the correction parameter using the measured distance value and the calculated value by the calculation unit is provided, and the amplification degree adjustment unit and the intensity adjustment unit can set the amplification degree and the irradiation intensity in a plurality of steps, respectively. The correction parameter setting means sets the product in two stages with a plurality of combinations in which the product of the amplification degree and the irradiation intensity is constant using a standard object, and outputs the signal of the output of the amplification means for each combination. The value is obtained, and the signal value of the output of the amplifying means for the combination of the amplification degree and the irradiation intensity not measured based on the obtained signal value of the output of the amplifying means is estimated, and Than is obtaining the correction parameters when the amplification degree is constant to measure the distance by adjusting the irradiation intensity Zui.

[0022]

According to the first aspect of the present invention, the amplification degree adjusting means for adjusting the amplification degree of the amplification means and the intensity adjusting means for adjusting the irradiation intensity of the projected spot are provided. When the diffuse reflectance is large compared to an object and the amount of light received by the light receiving means is too large, it is dealt with by reducing the amplification degree by the amplification degree adjusting means or reducing the irradiation intensity of the projected spot by the intensity adjusting means. It will be possible. On the contrary, when the diffuse reflectance is small compared to the standard object and the amount of light received by the light receiving means is too small, the amplification degree is increased by the amplification degree adjusting means, or the irradiation intensity of the projection spot is adjusted by the intensity adjusting means. It becomes possible to cope by raising it. In particular, when the amount of received light is small, the output signal from the light receiving means may not be identified due to internal noise of the amplification means.
By increasing the irradiation intensity of the light projection spot by the intensity adjusting means, the amount of light received by the light receiving means can be increased, so that it is possible to prevent the internal noise of the amplification means and the position signal from the light receiving means from becoming indistinguishable. It is possible to obtain the distance accurately. Further, since the irradiation intensity of the projected light spot and the amplification degree are adjusted to cope with the difference in the diffuse reflectance of the object, the adjustment range of the amplification degree can be reduced as compared with the case where only the amplification degree is adjusted to correspond. Therefore, the dynamic range of the amplification means can be reduced, and the design of the amplification means can be facilitated.

Further, when obtaining the correction coefficient, it is not necessary to replace the standard object or the neutral density filter, so that the correction coefficient can be obtained accurately without any substantial change in conditions. In particular, if the correction coefficient for each amplification factor is determined while keeping the product of the irradiation intensity of the projection spot and the amplification factor constant, each amplification factor can be set using only one standard object. The signal level input to the calculating means can be kept constant, and the correction coefficient for each amplification degree can be obtained more accurately. here,
Since the correction coefficient corrects an error caused by the light receiving optical system and the amplifying means, it does not change depending on the irradiation intensity of the projected spot. Moreover, it does not take time and effort to replace the object or the neutral density filter.

According to the second and third aspects, when setting the correction parameter for correcting the measured value of the distance to the object, the irradiation intensity and the amplification degree which cannot be measured by the standard object are set. The correction parameter corresponding to the combination is set on the basis of the signal value estimated from the signal value of the output of the amplifying means in the measurable combination, and the irradiation intensity and the amplification degree can be set only by using a standard object. It becomes possible to set the correction parameter for the combination. Here, the correction parameter based on the estimated signal value is a correction parameter when the irradiation intensity is constant and the amplification degree is adjusted to measure the distance, and the correction parameter when the amplification degree is constant and the irradiation intensity is adjusted to measure the distance. The correction parameter at that time can be set.

[0025]

【Example】

(Embodiment 1) The basic construction of this embodiment is similar to that shown in FIG. 7, but as shown in FIG. 1, the drive unit 14 is capable of adjusting the energy supplied to the light emitting element 11. Is different. That is, as shown in FIG. 2, the driving unit 14 includes an operational amplifier OP ₁ , resistors R ₀ , R ₁ , ..., Rn that determine the amplification degree of the driving unit 14, and an operational amplifier OP 1.
A resistor R ₁ , connected between the output terminal of ₁ and the inverting input terminal ,.
, Rn so as to set the amplification degree of the drive unit 14, the switch elements S ₁ , ..., Sn are connected in series to the resistors R ₁ ,. Here, when the resistance value of the resistor R ₀ is R,
The resistance R ₁ is R, the resistances R ₂ , ..., Rn are R / α, respectively.
-It is set to be (n-1). However, α is a natural number constant. Further, the switch elements S ₁ , ..., S
An analog switch or the like is used for n. Therefore, if the amplitude of the modulation signal input to the driving unit 14 is P, a signal having the amplitude of P is input to the light emitting element 11 when the switch element S ₁ is on, and the switch element S ₁
When i (i = 2, ..., N) is on, P / α
The signal having the amplitude of (i-1) is input to the light emitting element 11. In this way, the drive unit 14 functions as strength adjusting means.

On the other hand, the amplifier circuits 24a and 24b are, as shown in FIG. 3, the operational amplifier OP ₂ and the amplifier circuits 24a and 24b.
Resistances r ₀ , r ₁ , ..., Rj that determine the amplification factor of 4b
, And resistances r ₁ , ..., Rj connected between the output terminal and the inverting input terminal of the operational amplifier OP ₂ , each resistance r ₁ , so as to set the amplification degree of the amplifier circuits 24a, 24b. .., rj are respectively connected in series with switch elements T ₁ , ..., Tj. Here, when the resistance value of the resistance r ₁ is r, the resistances r ₂ ,.
Are respectively set to be r.alpha..multidot. (J-1). However, α is a natural number constant. Also, the resistance r ₀
The resistance value of is set to r / A. However, A is a constant. An analog switch or the like is used for the switch elements T ₁ , ..., Tj. Therefore, when the switch element T ₁ is on, the amplification degrees of the amplifier circuits 24a and 24b are A, and when the switch element Ti (i = 2, ..., j) is on, the amplifier circuits 24a and 24b are The amplification degree is A · α · (i−1). That is, the amplifier circuits 24a and 24b function as amplification degree adjusting means. Here, the switch elements S ₁ , ..., Sn of the drive section 14 and the switch elements T ₁ ,. Further, generally, n = j is set.

First, the case of obtaining the correction parameters κ, g and offset will be described. At this time, the determination unit 25
Switching element S ₁ of the driver 14, ..., and Sn, an amplifier circuit 24a, the switch elements 24b T _1, ..., selects an index is the same for the Tj. That is, if the switch element S ₁ is on, the switch element T ₁ is on. With this selection, the product of the output amplitude of the drive unit 14 and the amplification degree of the amplifier circuits 24a and 24b is {P /
α · (i−1)} × A · α · (i−1) = P · A, which is constant regardless of the amplification degree. Therefore, if the standard object 3 is placed at the reference position (the position where the light receiving spot is formed at the center of the light receiving surface of the position sensor 11) in order to obtain the correction parameters κ, g, and offset, the amplification degree is switched. Also, since the output levels of the amplifier circuits 24a and 24b do not change, data for each amplification degree can be obtained under substantially constant conditions. Similarly, by changing the position of the object 3 and obtaining data for each amplification degree, and obtaining data at three locations, the correction parameters κ, g, and offset for each amplification degree can be determined.

When the distance of the object 3 is measured after the correction parameters κ, g, and offset are determined, the object 3 to be measured most often is the standard object 3, and the modulation signal generating section 13 of the standard object 3 is used. The amplitude P of the modulated signal output from the device and the basic amplification degree A of the amplifier circuits 24a and 24b are adjusted. When the diffuse reflectance of the object 3 to be actually measured is larger than that of the standard object 3, the signal level input to the determination unit 25 is high, and therefore the determination unit 25 increases the level of the input signal by a predetermined level. When this is detected, the switch elements S ₁ , ..., Sn of the drive unit 14 are sequentially switched so as to reduce the amplitude of the input signal to the light emitting element 11. At this time, the amplification degrees of the amplifier circuits 24a and 24b are set to the minimum. That is, the output level of the drive unit 14 is reduced for the object 3 having a large diffuse reflectance,
This is achieved by reducing the irradiation intensity of the projected spot. On the other hand, for the object 3 having a diffuse reflectance smaller than that of the standard object 3, the switch elements T ₁ , so that the amplification degrees of the amplifier circuits 24 a, 24 b are increased based on the level of the input signal to the determination unit 25. .., Tj are sequentially switched. At this time, the output level of the drive unit 14 is set to the maximum.

As described above, with respect to the object 3 having a large diffuse reflectance, the amplification degree of the amplification circuits 24a and 24b is minimized to reduce the irradiation intensity of the light projection spot, thereby amplifying the amplification circuits 24a and 24b. The output of 24b is prevented from being saturated, and for the object 3 having a small diffuse reflectance, the irradiation intensity of the projection spot is maximized and the amplification circuits 24a, 24a
Since the influence of noise is prevented by increasing the amplification factor of b, it is possible to always input the signal of the optimum level to the determination unit 25 and accurately measure the distance. Of.

(Second Embodiment) In the first embodiment, the product of the output amplitude of the drive unit 14 and the amplification degree of the amplifier circuits 24a and 24b is
Although an example in which the correction parameters κ, g, and offset are set under the condition of P · A is shown, the product of the combination of the output amplitude of the driving unit 14 and the amplification degree of the amplifier circuits 24a and 24b is P · A.
There are also combinations other than the case. That is, the combination of the output amplitude of the drive unit 14 and the amplification degree of the amplifier circuits 24a and 24b is as shown in Table 1. However, in Table 1, the product of the amplitude P _j and the amplification degree A _k is represented by Q _m . However,
j and k are integers, and when the value of j increases by 1, the amplitude P
_It is assumed that _j becomes 1 / α times, and the amplification degree A _k becomes α times as the value of k increases by one. In addition, m = k−j.

[0031]

[Table 1]

Here, the amplification circuit 24a,
Assuming that the maximum value of the product in the range in which the output of 24b is not saturated is Q ₀ , for the combination where the products are Q ₁ , Q ₂ , Q ₃ , and Q ₄ , the correction parameter κ,
g and offset cannot be set. That is, it is desirable that the setting conditions of the correction parameters κ, g, and offset are matched with the actual measurement conditions. However, for the standard object 3, the output amplitude of the drive unit 14 and the amplification circuits 24a and 24a, 24a.
Since some combinations of b and the amplification degree are inconvenient to set, it may not be possible to set desirable correction parameters κ, g, and offset with such combinations.

In the present embodiment, combinations that cannot be combined are estimated from the measurement results of the range that can be combined. In the present embodiment, as shown in FIG. 4, the ranging signals V ₁ and V ₂ output from the amplifier circuits 24a and 24b are converted into digital signals by the A / D converters 26a and 26b, and corrected by the judging unit 25. In the parameter setting means for setting the parameters κ, g and offset,
By performing the operation as follows using ranging signals V _1, V ₂ of the digital values, and estimates the value of the ranging signals V _1, V ₂ of the combination can not be set, estimated ranging signal V ₁ ，
The correction parameters κ, g, and offset are obtained using V ₂ . Here, at the time of measurement, as shown in FIG.
Control only the amplification degree of the amplifier circuits 24a and 24b,
The output amplitude of the drive unit 14 is not controlled. That is, the control is performed within the range of one horizontal line in Table 1.

In setting the correction parameters κ, g and offset, first, the amplification circuit 24a,
An amplitude P _j which output is obtained the maximum product Q ₀ in a range that does not saturate and 24b and the combination of the amplification factor A _k, the product Q ₀ as one step smaller product Q _-1 is obtained than the product Q _{0 Distance-} measuring signals V _1jk and V _2jk are respectively _obtained for the combination of the obtained amplitude P _j and the amplification degree A _{k, in} which only the amplitude P _j for each amplification degree A _{k is} lowered by one step.
In Table 1, combinations of j = k and j within a range of j ≧ 2
_Distance measurement signals V _1jk and V _2jk are obtained for the combination of −k = 1. The range-finding signals in the combination where the product becomes Q ₀ are (V ₁₁₁ , V ₂₁₁ ), (V ₁₂₂ ,
V ₂₂₂ ), ..., (V _1nn , V _2nn ), and the distance measurement signals in the combination where the product becomes Q ₋₁ are (V ₁₂₁ , V ₂₂₁ ),
(V ₁₃₂ , V ₂₃₂ ), ..., (V _{1 (n + 1) n} , V _{2 (n + 1) n} )
When it is, the ranging signal (V _1LL at which the product is to Q _0, V
_2LL) and ranging signal at which the product is to _{Q -1 (V 1 (L +} 1) L, V
_{2 (L + 1) L} ) is obtained by the measurement result in which the amplitude is changed to P _L and P _{L + 1} and the amplification A _L is fixed, and the amplification is A _{L + 1} . Even if there are amplitudes P _L and P _{L + 1}
It can be considered that the distance measurement signal changes at the same rate when changed to and. That is, it is estimated that the following equation holds for the distance measurement signals (V _{1L (L + 1)} , V _{2L (L + 1)} ) whose product becomes Q ₁ .

V _{1L (L + 1)} = V _{1 (L + 1) (L + 1)} · (V _1LL / V _{1 (L + 1) L} ) V _{2L (L + 1)} = V _{2 (L + 1) (L + 1) ·} (V 2LL / V 2 (L + 1) L) in the same manner, the product is Q ₂ ranging signal _{(V 1L (L + 2)} , V
_{2L (L + 2)} ), the following equation holds. V _{1L (L + 2)} = V _{1 (L + 2) (L + 2)}・ (V _{1L (L + 1)} / V _{1 (L + 2) (L + 1)} ) = V _{1 (L + 2 ) (L + 2)}・ (V _{1 (L + 1) (L + 1)} / V _{1 (L + 2) (L + 1)} ) ・ (V _1LL / V _{1 (L + 1) L} ) V _{2L (L + 2)} = V2 _{(L + 2) (L + 2)}・ ( _{V2L (L + 1)} / V2 _{(L + 2) (L + 1)} ) = V2 _{(L + 2) ( L + 2)}・ (V _{2 (L + 1) (L + 1)} / V _{2 (L + 2) (L + 1)} ) ・ (V _2LL / V _{2 (L + 1) L} ) If applied, it is estimated that the following _equation 1 is established for the ranging signals (V _1jk , V _2jk ) where the product of the amplitude P _j and the amplification degree A _k has an arbitrary value.

[0036]

[Equation 1]

If _{Equation 1} is used, it is possible to estimate the signal value of the ranging signal (V _1jk , V _2jk ) in the _unmeasurable range using the ranging signal (V _1jk , V _2jk ) in the measurable range. , Using the estimated signal value, the correction parameters κ, g,
The offset can be obtained. Regarding the range where the product of the amplitude P _j and the amplification degree A _k is smaller than Q ₀ , it is said that the correction parameters κ, g and offset are _obtained by using the actually measured distance measurement signals (V _1jk , V _2jk ). There is no end.
Since the correction parameters κ, g, and offset are obtained by the method as described above, the number of steps for setting the amplitude P _{j and} the number of steps for setting the amplification factor A _k do not necessarily have to be the same.

As described above, the correction parameters κ, g,
After the offset is determined, the output amplitude of the drive unit 14 is fixed as shown in FIG. 5, only the amplification degree of the amplifier circuits 24a and 24b is adjusted, and the correction means in the determination unit 25 uses the correction parameters κ, g, and The offset is used to correct the measured distance. (Embodiment 3) In this embodiment, as shown in FIG. 6, the amplification degree A _k of the amplifier circuits 24a and 24b is not controlled during measurement, but only the amplitude P _j of the drive unit 14 is controlled. _Then , the distance measurement signals (V _1jk , V _2jk ) in the range where the distance measurement signals (V _1jk , V _2jk ) for obtaining the correction parameters κ, g, offset cannot be directly obtained are measured distance measurement signals (V _1jk , An example of estimation from V _2jk ) will be described.

That is, the correction parameters κ, g, offset
When setting, first, the maximum product Q of the object 3 in a range in which the outputs of the amplifier circuits 24a and 24b are not saturated is set.
A combination of an amplitude P _j and an amplification degree A _k that gives ₀ ,
The product Q so that a product Q ₋₁ that is one step smaller than the product Q ₀ is obtained
_For the combination of the amplitude P _j and the amplification degree A _k for which ₀ is obtained, only the amplification degree A _k for each amplitude P _{j is} lowered by one step, and the ranging signals V _1jk and V _2jk are respectively _obtained.
Ask for. That is, when the correction parameters κ, g, and offset are set, in the second embodiment, the distance measurement signals V _1jk and V _2jk when the amplitude P _j is changed with respect to the one-step amplification degree A _k are obtained. Then, the amplification degree A for one-step amplitude P _j
The difference is that the distance measurement signals V _1jk and V _2jk are obtained when _k is changed. Here, in this embodiment, the amplitude P _j is set to increase as the value of j increases, and conversely, the amplification degree A _k is set to decrease as the value of k increases. That is, the relationship is opposite to that of the second embodiment.

Here, the range-finding signals in the combination where the product is Q ₀ are (V ₁₁₁ , V ₂₁₁ ), (V ₁₂₂ ,
V ₂₂₂ ), ..., (V _1nn , V _2nn ), and the distance measurement signals in the combination where the product is Q ₋₁ are (V ₁₁₂ , V ₂₁₂ ),
(V ₁₂₃ , V ₂₂₃ ), ..., (V _{1 (n-1) n} , V _{2 (n-1) n} )
When it is, the ranging signal (V _1LL at which the product is to Q _0, V
_2LL) and ranging signal at which the product is to _{Q -1 (V 1L (L +} 1), V
_{2L (L + 1)} ) means that the amplitude is fixed at P _L and the amplification is at A _L and A
_{This is} obtained by changing the measurement result to _{L + 1} and the amplification degree is A _L and A _{L + 1} even when the amplitude is P _{L + 1.}
It can be considered that the distance measurement signal changes at the same ratio when changed to and. That is, it is estimated that the following equation holds for the distance measurement signals (V _{1 (L + 1) L} , V _{2 (L + 1) L} ) whose product becomes Q ₁ .

V _{1 (L + 1) L} = V _{1 (L + 1) (L + 1)} · (V _1LL / V _{1L (L + 1)} ) V _{2 (L + 1) L} = V _{2 (L +1) (L + 1) } (V _2LL / V _{2L (L + 1)} ) Therefore, in the same manner as the second embodiment, the distance measurement in which the product of the amplitude P _j and the amplification degree A _k becomes an arbitrary value. Signal (V _1jk ,
It is estimated that the following _equation 2 holds for V _2jk ).

[0042]

[Equation 2]

By using the _{equation 2} , the estimated values of the distance measurement signals V _1jk and V _{2jk in} the _unmeasurable range can be obtained, and the correction parameters κ, g and offset can be set based on these estimated values. is there. Other configurations are similar to those of the second embodiment.

[0044]

As described above, the present invention is provided with the amplification degree adjusting means for adjusting the amplification degree of the amplification means and the intensity adjusting means for adjusting the irradiation intensity of the projected spot.
For example, when the diffuse reflectance is large compared to the standard object and the amount of light received by the light receiving means is too large, the amplification degree is adjusted by the amplification degree adjusting means, or the irradiation intensity of the projection spot is reduced by the intensity adjusting means. By doing so, it becomes possible to respond. On the contrary, when the diffuse reflectance is small compared to the standard object and the amount of light received by the light receiving means is too small, the amplification degree is increased by the amplification degree adjusting means, or the irradiation intensity of the projection spot is adjusted by the intensity adjusting means. It becomes possible to cope by raising it.
As a result, the input signal level to the arithmetic means can be maintained at the optimum level, and there is an advantage that the distance can be accurately measured.

Further, when obtaining the correction coefficient, it is not necessary to replace the standard object or the neutral density filter, so that there is an advantage that the correction coefficient can be accurately obtained without substantially changing the conditions. Moreover, it does not take time and effort to replace the object or the neutral density filter. Furthermore, when setting the correction parameter that corrects the measured value of the distance to the object,
The correction parameter corresponding to the combination of the irradiation intensity and the amplification degree, which cannot be measured with a standard object,
When setting based on the signal value estimated from the signal value of the output of the amplifying means in a measurable combination, the correction parameters for all combinations of the irradiation intensity and the amplification degree can be set only by using a standard object. It has the advantage that it can be set. As the correction parameter based on the estimated signal value, there are a correction parameter when the irradiation intensity is fixed and the amplification degree is adjusted to measure the distance, and a correction parameter when the amplification degree is fixed and the irradiation intensity is adjusted to measure the distance. It is possible to set each of the correction parameters and.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a first embodiment.

FIG. 2 is a circuit diagram of a drive unit used in the first embodiment.

FIG. 3 is a circuit diagram of an amplifier circuit used in the first embodiment.

FIG. 4 is a block circuit diagram showing a state at the time of setting a correction parameter in the second and third embodiments.

FIG. 5 is a block circuit diagram showing a state at the time of measuring a distance to an object in the second embodiment.

FIG. 6 is a block circuit diagram showing a state at the time of measuring a distance to an object in the third embodiment.

FIG. 7 is a block circuit diagram showing a conventional example.

FIG. 8 is an explanatory diagram showing the operation principle of the displacement sensor according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light emitting means 2 Light receiving means 11 Light emitting element 12 Light emitting optical system 13 Modulation signal generating section 14 Driving section 21 Position sensor 22 Light receiving optical system 23a Current-voltage converting circuit 23b Current-voltage converting circuit 24a Amplifying circuit 24b Amplifying circuit 25 Judgment section

Claims (3)

[Claims] 1. A light projecting means for irradiating a surface of an object with a light projecting spot which is a dot-like light pattern, and a reflected light of the light projected onto the object from the light projecting means is received to form an image of the light projecting spot. A light receiving means for outputting a pair of position signals in which the ratio of the output levels changes according to the position of the received light spot and the sum of the output levels changes according to the amount of received light; and an amplifying means for amplifying each position signal. A displacement sensor including a calculation unit that calculates a distance to an object based on the output of the amplification unit, and an amplification degree adjustment unit that adjusts the amplification degree of the amplification unit and an intensity adjustment that adjusts the irradiation intensity of the projection spot. Displacement sensor comprising means. 2. The calculation means includes a correction means for obtaining a distance to an object by performing a correction calculation in which a predetermined correction parameter is applied to a signal value output from the amplification means, and an actually measured value of the distance to the object. And a parameter setting means for determining a correction parameter using the calculated value by the calculating means, the amplification degree adjusting means and the intensity adjusting means are configured so that the amplification degree and the irradiation intensity can be set in a plurality of stages, respectively. The correction parameter setting means uses a standard object to set the product in two stages for a plurality of combinations in which the product of the amplification degree and the irradiation intensity is constant, obtains the signal value of the output of the amplification means for each combination, and obtains it. Based on the signal value of the output of the amplifying means, the signal value of the output of the amplifying means for the combination of the amplification degree and the irradiation intensity that has not been measured is estimated, and the irradiation intensity is determined based on the estimation result. The displacement sensor according to claim 1, wherein a correction parameter for measuring the distance by adjusting the amplification degree is determined. 3. The correction means for calculating the distance to the object by performing a correction calculation applying a predetermined correction parameter to the signal value of the output of the amplification means, and the measured value of the distance to the object. And a parameter setting means for determining a correction parameter using the calculated value by the calculating means, the amplification degree adjusting means and the intensity adjusting means are configured so that the amplification degree and the irradiation intensity can be set in a plurality of stages, respectively. The correction parameter setting means uses a standard object to set the product in two stages for a plurality of combinations in which the product of the amplification degree and the irradiation intensity is constant, obtains the signal value of the output of the amplification means for each combination, and obtains it. The signal value of the output of the amplifying means for the combination of the amplification degree and the irradiation intensity that has not been measured based on the signal value of the amplifying means is estimated, and the amplification degree is fixed based on the estimation result. 2. The displacement sensor according to claim 1, wherein a correction parameter for measuring the distance by adjusting the irradiation intensity is obtained.