JP3243300B2 - Displacement sensor - Google Patents

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 capable of measuring a distance to an object in a non-contact manner, a sensor for optically measuring 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 to the object 3 to form a light projection spot, which is a point-like light pattern, on the surface of the object 3. The light reflected from the surface of the object 3 of the light beam emitted from the light projecting means 1 is detected by the light receiving means 2. In the light receiving means 2, the incident light is converged by passing through the light receiving optical system 22, so that the PS
A light receiving spot as an image of the light projecting 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 that can specify 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 of the light receiving spot is determined 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 determined based on triangulation.

[0003] This will be described more specifically. Light emitting means 1
A light emitting element 11 such as a semiconductor laser is provided. Light output from the light emitting element 11 is passed through a light projecting optical system 12 to form a light beam. The light emitting element 11 is a driving unit 1
4, is driven by a modulation signal of a predetermined frequency from the modulation signal generation unit 13, and the modulation signal generation unit 13 generates a modulation signal for modulating a current supplied to the light emitting element 11.

On the other hand, a pair of position signals I ₁ and I ₂ output from the position sensor 21 are converted into voltage signals through current-voltage conversion circuits 23a and 23b, respectively. After each voltage signal is amplified through amplifier circuits 24a and 24b as amplifying means, it is input as distance measurement signals V ₁ and V ₂ to a determination unit 25 as an arithmetic means and output signals corresponding to the distance to the object 3. Generate Z.

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, so that the p-layer, which is a high-resistance layer, is divided according to the irradiation position of the light-receiving spot. The current is divided so as to correspond to the division ratio of the p-layer, and the position signals I ₁ and I _{2 as} current signals are taken out from the respective output electrodes. That is, the position signals I ₁ and I ₂ output from the respective output electrodes are represented by Zs, the total resistance between the output electrodes, the distance between the output electrode outputting the position signal I ₁ and the light receiving spot, and the position signal I 2. Assuming that the ratio of the distance between the output electrode outputting I ₂ and the light receiving spot is Z ₁ : Z ₂ , I ₁ = (Z ₂ / Zs) · I (1) I ₂ = (Z ₁ / Zs) · I (2) On the other hand, as shown in FIG. 8, the distance from the center of the light projecting optical system 12 to the object 3 when the light receiving spot is located at the center of the light receiving surface of the position sensor 21 is Rc, and the distance to the object 3 is It is assumed that the distance has decreased by Δr. At this time, the position of the light receiving spot moves downward by Δx in FIG. Assuming that the effective length of the light receiving surface of the position sensor 21 is ₂ L, Z ₁ : Z ₂ = (L + Δx) :( L−Δx) (3) Therefore, the expressions (1), (2) and (3) The following equation is obtained from the equation.

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
, And the angle formed by a straight line connecting the point at the distance Rc on the optical axis of the light projecting optical system 12 and the center of the position sensor 21 with the optical axis of the light projecting optical system 12 is θ. The following relationship is obtained:

(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 found, the distance Δ of the displacement of the object 3 by the equation (5)
r can be obtained.

On the other hand, the position signals I ₁ and I ₂ are supplied to the amplifying circuit 24.
Since the distance measurement signals V ₁ and V ₂ obtained through the signals 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 of the amplifier circuits 24a and 24b. If the coefficients for the position signals I ₁ and I ₂ including the degrees and the like are denoted by A ′ · A and A, respectively, the following equation is obtained. V ₁ = A ′ · A · I ₁ (6) V ₂ = A · I ₂ (7) Further, the position signals I ₁ and I are obtained from the equations (4) by the equations (6) and (7).
Eliminating ₂ gives the following equation: Δx = − {(V ₁ / A ′) − V ₂ ) / (V ₁ / A ′) + V ₂ )} · L (8) Therefore, the equation (8) is substituted into the equation (5) and transformed. 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 ′), C = −bL / (a + L). At the time of calculation by the determination unit 25, correction is performed on the equation (9). At the time of correction, the scale of the actual measured value of the distance and the scale of the output signal Z are adjusted so that the measured dimensions are (When the signal value changes by 1, the signal value of the output signal Z also changes by 1.)
The constant D is multiplied by the equation (9), and the constant E is added to the equation (9) so that the measured distance value 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 = DB, offset = DC + E. After all, when the distance to the object 3 is actually measured, three correction parameters κ, g, of of the distance measurement signals V ₁ and V ₂ are used.
What is necessary is just to determine fset. Equation (10) is expressed as V ₁ / (κ · V ₁ +
V ₂ ) is a linear expression, and a correction parameter g, which is a gradient of the linear expression, is a coefficient for matching a unit dimension of the distance of the object 3 to a unit of a signal value of the output signal Z, and an intercept of the linear expression. Is an offset value for matching the measured distance to the object 3 with the signal value of the output signal Z. The correction parameter κ is a coefficient for correcting errors due to factors such as aberrations and position errors of the light receiving optical system 22 and errors in the amplification degrees of the amplifier circuits 24a and 24b.

The above three correction parameters κ, g, of
fset is set before the measurement of the distance by the calculation in the determination unit 25.
It is determined by comparing the measured value of the distance with the signal value of the output signal Z. Where the correction parameters κ, g, offs
Since et is three, the distance to the object 3 is set in three steps, and a simultaneous ternary equation obtained based on the measured value of each distance and the obtained distance measurement signals V ₁ and V ₂ can be solved. The correction parameters κ, g, and offset can be determined.

The objects 3 whose distance is to be measured include those having a glossy surface, such as metal, and those having a black surface. Diffuse reflectance differs greatly depending on the type of the object 3. Therefore, the amount of received light incident on the position sensor 21 greatly changes depending on the type of the object 3. That is, the current-voltage conversion circuits 23a and 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 dynamic range that satisfies a sufficiently high level, the manufacturing cost becomes extremely high. Therefore, at present, the dynamic range is suppressed to a practical level.

Therefore, the amplification degree of the amplifier circuits 24a and 24b is set in a plurality of steps so that the input dynamic range of the judgment section 25 can be suppressed and the distance measuring signals V ₁ and V ₂ of the optimum level can be inputted. It is conceived to provide an amplification degree adjusting means that can perform the amplification.

[0014]

When the amplification of the amplifier circuits 24a and 24b is adjusted as described above, the above-mentioned correction parameters κ, g, and offset are determined for each settable amplification. Is required. That is, as is clear from the derivation process of equation (10) including the correction parameters κ, g, and offset, the correction parameters κ, g
Including the amplification ratios A 'of the amplifier circuits 24a and 24b,
Since the value of the correction parameter offset is affected by the correction parameters κ, g, all the correction parameters κ, g, of
It can be seen that fset changes according to the ratio A 'of the amplification degrees 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, include the a and b defined by the equation (5)), they are affected by the optical characteristics. . That is, when the amplification of the amplification circuits 24a and 24b is adjusted, the amplification ratio A '
May change, so that the correction parameter κ,
g and offset need to be determined.

However, if the correction parameters κ, g, and offset for each amplification factor are obtained by actually measuring the distance using the object 3 having the standard diffuse reflectance, depending on the amplification factor set, There is a problem that the correction parameters κ, g, and offset cannot be obtained accurately. For example, correction parameters κ, g, offset
When the amplification is set to be smaller than the optimum amplification for obtaining the distance, the level difference between the distance measurement signals V ₁ and V ₂ and the noise becomes small, and the distance cannot be obtained accurately. Occurs. Conversely, when the amplification degree is set to be larger than the optimum amplification degree, the amplification circuit 24
a, 24b are saturated and the correction parameters κ, g, of
The problem arises that fset cannot be determined 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 amount of light received by the position sensor 21 in accordance with the degree of amplification using the neutral density filter 15. However, when the standard object 3 is replaced, the distance to the object 3 is deviated, and the reference distance may vary depending on the amplification degree. As a result, the distance to the object 3 is substantially changed due to refraction or refraction, and the reference distance varies. Therefore, the correction parameters κ, g, and offset cannot be accurately obtained, and even if the same object 3 is used, a problem may occur in that the measured value changes only by changing the amplification degree. Further, when the standard object 3 and the neutral density filter 15 are replaced, there is a problem that it takes time to determine the correction parameters κ, g, and offset.

When the distance to the object 3 is measured, if the output level of the light beam of the light projecting means 1 is set to be suitable for the object 3 having a large diffuse reflectance,
When obtaining the distance for the object 3 having a very small diffuse reflectance, the amount of light received by the position sensor 21 becomes very small. Therefore, 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. The difference between the noise level and the signal level cannot be made sufficiently large, resulting in a problem that the correction parameters κ, g, and offset cannot be accurately obtained.

SUMMARY OF THE INVENTION An object of the present invention is to provide a displacement sensor capable of accurately obtaining a distance by inputting a signal of an optimum level to an arithmetic means. It is.

[0019]

According to the present invention, in order to achieve the above object, a light projecting means for irradiating a light projecting spot, which is a point-like light pattern, onto the surface of an object, and a light projecting means comprising: A pair of light-receiving parts that receive the reflected light of the light applied to the object and change the ratio of the output level according to the position of the light-receiving spot formed as an image of the light-projected spot and change the sum of the output levels according to the amount of received light adjusting light receiving means for outputting a position signal, and amplifying means for amplifying each position signal respectively, Bei example and calculating means for calculating a distance to the object based on the output of the amplifying means, the amplification degree of the amplification means The configuration provided with the amplification degree adjusting means and the intensity adjusting means for adjusting the irradiation intensity of the light projection spot is a common configuration.

According to the first aspect of the present invention, the calculating means performs a correcting calculation by applying a predetermined correction parameter to the signal value of the output of the amplifying means, and a correcting means for obtaining a distance to the object, A parameter setting unit that determines a correction parameter using an actual measured value of the distance and a calculation value of the calculation unit; and the amplification degree adjustment unit and the intensity adjustment unit can set the amplification degree and the irradiation intensity in a plurality of stages. The correction parameter setting means uses a standard object to set the product in two stages in a plurality of combinations in which the product of the amplification degree and the irradiation intensity is constant, and outputs a signal of the output of the amplification means for each combination. The value of the output of the amplifying means is estimated for the combination of the amplification degree and the irradiation intensity which are not measured based on the obtained signal value of the output of the amplifying means. 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 the second aspect of the present invention, the calculating means performs a correcting calculation by applying a predetermined correction parameter to the signal value of the output of the amplifying means, and a correcting means for obtaining a distance to the object, A parameter setting unit that determines a correction parameter using an actual measured value of the distance and a calculation value of the calculation unit; and the amplification degree adjustment unit and the intensity adjustment unit can set the amplification degree and the irradiation intensity in a plurality of stages. The correction parameter setting means uses a standard object to set the product in two stages in a plurality of combinations in which the product of the amplification degree and the irradiation intensity is constant, and outputs a signal of the output of the amplification means for each combination. The value of the output of the amplifying means is estimated for the combination of the amplification degree and the irradiation intensity which are not measured based on the obtained signal value of the output of the amplifying means. 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 and second aspects of the present invention, there are provided amplification degree adjusting means for adjusting the amplification degree of the amplification means and intensity adjustment means for adjusting the irradiation intensity of the light projection spot. 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 decreased by the amplification degree adjusting means, or the irradiation intensity of the projection spot is reduced by the intensity adjusting means. This makes it possible to respond. Conversely, 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 increased by the intensity adjusting means. By increasing it, it becomes possible to respond. In particular, if the amount of received light is small, it may not be possible to identify the output signal from the light receiving means due to the internal noise of the amplifying means.However, if the irradiation intensity of the projected spot is increased by the intensity adjusting means, the amount of light received by the light receiving means can be reduced. Since it can be increased, it is possible to avoid that the internal noise of the amplifying unit and the position signal from the light receiving unit cannot be distinguished, and the distance can be accurately obtained. In addition, since the irradiation intensity and the amplification degree of the light projecting spot are adjusted to cope with the difference in the diffuse reflectance of the object, the adjustment range of the amplification degree is reduced as compared with the case where only the amplification degree is adjusted to cope with the difference. As a result, the dynamic range of the amplifying means can be reduced, and the design of the amplifying means becomes easy.

In addition, when the correction coefficient is obtained, it is not necessary to replace the standard object or the neutral density filter, so that the correction coefficient can be obtained accurately without substantial change in conditions. In particular, if the correction coefficient for each amplification factor is determined while maintaining the relationship between the product of the irradiation intensity of the projection spot and the amplification factor to be constant, each amplification factor can be determined 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 is for correcting an error generated by the light receiving optical system and the amplifying means, it does not change depending on the irradiation intensity of the light projection spot. Moreover, there is no need to replace the object or the neutral density filter.

Further, when setting a correction parameter for correcting the measured value of the distance to the object, a correction parameter corresponding to a combination of the irradiation intensity and the amplification degree, which cannot be measured with a standard object, is measured. It is set based on the signal value estimated from the signal value of the output of the amplification means in a possible combination, and it is possible to set correction parameters for any combination of irradiation intensity and amplification degree only by using a standard object. Will be possible. Here, as a correction parameter based on the estimated signal value, a correction parameter when measuring the distance by adjusting the amplification intensity while keeping the irradiation intensity constant, and measuring the distance by adjusting the irradiation intensity while keeping the amplification intensity constant Correction parameters can be set.

[0025]

EXAMPLES (Basic Configuration) The configuration shown in FIG. 1, point basic structure is the same as the configuration shown in FIG. 7, which is adjustable to supply energy to the light emitting element 11 in the driving moving parts 14 Are different. That is, as shown in FIG.
₁ and resistors R ₀ , R ₁ ,
,..., Rn and the resistances R ₁ ,..., Rn connected between the output terminal and the inverting input terminal of the operational amplifier OP ₁ are set so that the amplification degree of the drive unit 14 is set by selecting the resistors R ₁ ,.
_1, ..., switching element S ₁ is connected in series respectively to Rn, ..., constituted by the Sn. Where the resistance R
_When the resistance value of ₀ is R, the resistance R ₁ is set to R, and the resistances R ₂ ,..., Rn are each set to R / α · (n−1). Here, α is a constant of a natural number.
An analog switch or the like is used for the switch elements S ₁ ,..., Sn. Therefore, if the amplitude of the modulation signal input to the drive unit 14 is P, the switch element S ₁
Is on, a signal having an amplitude of P is input to the light emitting element 11 and the switch element Si (i = 2,...,.
When n) is on, a signal having an amplitude of P / α · (i−1) is input to the light emitting element 11.
Thus, the drive unit 14 functions as a strength adjusting unit.

On the other hand, the amplifier circuit 24a, 24b, as shown in FIG. 3, the operational amplifier OP _2, the amplifier circuit 24a, 2
Resistance r _0, r ₁ for determining the 4b amplification of, ......, rj
When an operational amplifier resistor r ₁ connected between the output terminal and the inverting input terminal of the OP _2, ......, each resistor r ₁ so as to set the amplifier circuit 24a, 24b amplification of by selecting rj, ,..., Rj are connected in series with switch elements T ₁ ,. Here, assuming that the resistance value of the resistor r ₁ is r, the resistors r ₂ ,.
Are set to be r · α · (j−1). Here, α is a constant of a natural number. The resistance r ₀
Is set to r / A. Here, 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 is on, amplifier circuit 24a, the amplification degree of 24b becomes A, the switch elements Ti (i = 2, ......, j) is at is ON, the amplifier circuit 24a, 24b of the The amplification degree becomes A · α · (i-1). That is, the amplifier circuits 24a and 24b function as amplification degree adjusting means. .., And Tj of the amplifier circuits 24a and 24b are controlled on / off by the determination unit 25. The switching elements S ₁ ,..., Sn of the driving unit 14 and the switching elements T ₁ ,. In general, n = j is set.

First, the case where the correction parameters κ, g, and offset are obtained 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. In other words, the switch element S ₁ is if turned on, the switch element T ₁ is turned on. With this selection, the product of the output amplitude of the drive unit 14 and the amplification of the amplifier circuits 24a and 24b is ΔP /
α · (i−1)｝ × A · α · (i−1) = PA, which is constant regardless of the amplification degree. Therefore, if the standard object 3 is placed at a reference position (a position where the light receiving spot is formed at the center of the light receiving surface of the position sensor 11) to obtain the correction parameters κ, g, and offset, the amplification degree is switched. Also, the output levels of the amplifier circuits 24a and 24b do not change, and data for each amplification degree can be obtained under substantially constant conditions. Similarly, if the position of the object 3 is changed to obtain data for each amplification degree and three data points are obtained, 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 is set as the standard object 3, and the modulation signal generator 13 The amplitude P of the modulation signal output from the amplifier and the basic amplification degree A of the amplifier circuits 24a and 24b are adjusted in advance. When the diffuse reflectance of the object 3 to be actually measured is higher than that of the standard object 3, the signal level input to the determination unit 25 increases, so that 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 degree of the amplifier circuits 24a and 24b is set to the minimum. That is, for the object 3 having a large diffuse reflectance, the output level of the driving unit 14 is reduced,
This is achieved by reducing the irradiation intensity of the light projection spot. On the other hand, for the object 3 whose diffuse reflectance is smaller than that of the standard object 3, the switch elements T ₁ , ..., 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 intensity of the light projection spot is reduced while the amplification degree of the amplification circuits 24a and 24b is minimized, so that the amplification circuits 24a and 24b are reduced. For the object 3 having a small diffuse reflectance, the irradiation intensity of the light projection spot is maximized for the amplification circuit 24a,
Since the influence of noise is prevented by increasing the amplification degree of b, it is possible to always input an optimal level signal to the determination unit 25 and accurately measure the distance. It is.

(Embodiment 1) In the basic configuration described above , the correction parameters κ, g, and offset are set under the condition that the product of the output amplitude of the drive unit 14 and the amplification degree of the amplifier circuits 24a and 24b is PA. However, the combination of the output amplitude of the drive unit 14 and the amplification degree of the amplifier circuits 24a and 24b may be any combination other than the case where the product is PA. 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 shown in Table 1.
become that way. However, in Table 1, the amplitude P _j and the amplification A _k
Is represented by Q _m the product of. Here, j and k are integers, and when the value of j increases by one, the amplitude P _j becomes 1 / α times, and when the value of k increases by one, the amplification degree A _k becomes α times. Further, it is assumed that 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 in which 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 match 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
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 a combination.

In this embodiment, combinations that cannot be combined are estimated from the measurement results in the range in which the combinations can be combined. In the present embodiment, as shown in FIG. 4, the distance measurement signals V ₁ and V ₂ output from the amplifier circuits 24 a and 24 b are converted into digital signals by A / D converters 26 a and 26 b, and corrected by the determination unit 25. In the parameter setting means for setting the parameters κ, g, 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.
Only the amplification degree of the amplifier circuits 24a and 24b is controlled,
The output amplitude of the drive unit 14 is not controlled. That is, the control is performed in the range of one horizontal row in Table 1.

In setting the correction parameters κ, g, and offset, first, the amplification circuit 24 a,
The combination of the amplitude P _j and the amplification A _{k at} which the maximum product Q ₀ within the range in which the output of 24b does not saturate is obtained, and the product Q ₀ is obtained so as to obtain the product Q _-1 one step smaller than the product Q ₀ . _Distance measurement signals V _1jk and V _2jk are _obtained respectively for a combination of the obtained amplitude P _j and amplification degree A _k and only the amplitude P _j for each amplification degree A _k lowered by one stage.
In Table 1, combinations where j = k and j in the range of j ≧ 2
The distance measurement signals V _1jk and V _2jk are determined for the combination where −k = 1. The ranging 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 ranging signal in a combination in which the product is Q ₋₁ is (V ₁₂₁ , V ₂₂₁ ),
( _V132 , _V232 ), ..., (V1 _{(n + 1) n} , V2 _{(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 a 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} In some cases, the amplitudes are P _L and P _{L + 1}
It can be considered that the ranging signal changes at the same ratio when the distance is changed. That is, it is estimated that the following equation holds for the ranging signals (V _{1L (L + 1)} , V _{2L (L + 1)} ) whose products are 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)} · (V2 _{(L + 1) (L + 1)} / V2 _{(L + 2) (L + 1)} ) · ( _V2LL / V2 _{(L + 1) L} ) If applied, it is presumed that the following _equation 1 holds for the ranging signals (V _1jk , V _2jk ) in which the product of the amplitude P _j and the amplification degree A _k is an arbitrary value.

[0036]

(Equation 1)

Using _{Equation 1} , the signal values of the ranging signals (V _1jk , V _2jk ) in the _unmeasurable range can be estimated using the ranging signals (V _1jk , V _2jk ) in the measurable range. , The correction parameters κ, g,
You can find the offset. In a range where the product of the amplitude P _j and the amplification A _k is smaller than Q ₀ , the correction parameters κ, g, and offset are _obtained by using the actually measured ranging signals (V _1jk , V _2jk ). Not even.
Since the correction parameters κ, g, and offset are obtained by the method described above, the number of steps for setting the amplitude P _{j and} the number of steps for setting the amplification A _k do not necessarily have to be the same.

As described above, the correction parameters κ, g,
After the offset is determined, as shown in FIG. 5, the output amplitude of the driving unit 14 is fixed, and only the amplification degree of the amplifier circuits 24a and 24b is adjusted. The distance measured using the offset is corrected. Example 2 In this example, as shown in FIG. 6, the amplifier circuit 24a at the time of measurement, without controlling for the amplification degree A _k of 24b,
A case of controlling only the amplitude P _j of the drive unit 14, the correction parameter kappa, g, obtains the offset distance measurement signal _(V 1jk, V 2jk) ranging signal range can not be obtained directly _(V 1jk, V _2jk ) is obtained by measuring the actually measured distance signal (V
_1jk , V _2jk ).

That is, the correction parameters κ, g, offset
First, the maximum product Q of the object 3 in a range where the outputs of the amplifier circuits 24a and 24b are not saturated is set.
A combination of the amplitude P _{j at} which ₀ is obtained and the amplification A _k ,
The product Q is obtained such that a product Q _{-1 which} is one step smaller than the product Q ₀ is obtained.
_The distance measurement signals V _1jk , V _2jk are obtained by combining the amplitude P _j and the amplification A _k for which ₀ is obtained with one step lower than the amplification A _k for each amplitude P _j .
Ask for. That is, when the correction parameters κ, g, and offset are set, in the first embodiment , the distance measurement signals V _1jk and V _2jk are obtained when the amplitude P _j is changed with respect to the one-stage amplification A _k. Now, for one step amplitude P _j ,
_The difference is that the distance measurement signals V _1jk and V _2jk when _k is changed are obtained. Here, in this embodiment, it is assumed that the amplitude P _j is set to increase as the value of j increases, and conversely, the amplification A _k decreases as the value of k increases. That is, the relationship is opposite to that of the first embodiment .

Here, the ranging 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 signal in a combination in which the product is Q ₋₁ is (V ₁₁₂ , V ₂₁₂ ),
( _V123 , _V223 ), ..., (V1 _{(n-1) n} , V2 _{(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 degrees are A _L and A
_{It is} obtained by the measurement result changed to _{L + 1,} and when the amplitude is P _{L + 1} , the amplification degree is A _L and A _{L + 1.}
It can be considered that the ranging signal changes at the same ratio when the distance is changed. That is, it is estimated that the following equation holds for the ranging signals (V _{1 (L + 1) L} , V _{2 (L + 1) L} ) whose products are 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, similarly to the first embodiment , the distance measurement in which the product of the amplitude P _j and the amplification A _k becomes an arbitrary value Signal (V _1jk ,
V _2jk ), it is estimated that the following _equation 2 holds.

[0042]

(Equation 2)

By using _{equation (2)} , the estimated values of the ranging 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 the estimated values. is there. Other configurations are the same as in the first embodiment .

[0044]

According to the present invention, as described above, the amplification degree adjusting means for adjusting the amplification degree of the amplification means and the intensity adjustment means for adjusting the irradiation intensity of the projection spot are provided.
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 decreased by the amplification degree adjusting means, or the irradiation intensity of the projected spot is reduced by the intensity adjusting means. By doing so, it is possible to respond. Conversely, 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 increased by the intensity adjusting means. By increasing it, it becomes possible to respond.
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 measured accurately.

Since it is not necessary to replace the standard object or the neutral density filter when obtaining the correction coefficient, there is an advantage that the correction coefficient can be obtained accurately without substantial change in conditions. Moreover, there is no need to replace the object or the neutral density filter. Further, when setting a correction parameter for correcting the measured value of the distance to the object,
A correction parameter corresponding to a combination of irradiation intensity and amplification that cannot be measured with a standard object,
Since it is set based on the signal value estimated from the output signal value of the amplifying means in a measurable combination, it is possible to set correction parameters for any combination of irradiation intensity and amplification degree using only a standard object. There is an advantage of becoming. The correction parameters based on the estimated signal values include a correction parameter when measuring the distance by adjusting the amplification intensity while keeping the irradiation intensity constant, and a correction parameter when measuring the distance by adjusting the irradiation intensity while keeping the amplification intensity constant. And correction parameters can be set.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram showing a basic configuration .

FIG. 2 is a circuit diagram of a driving unit used for a basic configuration .

FIG. 3 is a circuit diagram of an amplifier circuit used for a basic configuration .

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

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

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

 REFERENCE SIGNS LIST 1 light projecting means 2 light receiving means 11 light projecting element 12 light projecting optical system 13 modulation signal generating unit 14 driving unit 21 position sensor 22 light receiving optical system 23 a current-voltage converting circuit 23 b current-voltage converting circuit 24 a amplifying circuit 24 b amplifying circuit 25 Judgment unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01C 3/06 G01B 11/00

Claims (2)

(57) [Claims] 1. A light projecting means for irradiating a light projecting spot, which is a point-like light pattern, onto the surface of an object, and receiving reflected light of light illuminating the object from the light projecting means to form an image of the light projecting spot. Light receiving means for outputting a pair of position signals whose output level ratio 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 amplifying means for amplifying each position signal. , e Bei and calculating means for calculating a distance to the object based on the output of the amplifying means, the amplification factor adjusting means for adjusting the amplification degree of the increase <br/> width means adjusts the irradiation intensity of the projected light spot Displacement with strength adjusting means
In the sensor, the calculating means is a signal value of an output of the amplifying means.
Is applied to the correction
Correction means for determining the distance to the object by
Using the measured value of the distance to the body and the value calculated by the calculation means
Parameter setting means for determining correction parameters
The amplification degree adjustment means and the intensity adjustment means
And irradiation intensity can be set in multiple stages.
The correction parameter setting means is increased by using a standard object.
In multiple combinations where the product of width and irradiation intensity is constant
The product is set in two stages and the amplification means for each combination
Calculate the output signal value and convert it to the determined output signal value of the amplifying means.
Combination of amplification and irradiation intensity not measured based on
The signal value of the output of the amplifying means in response to the
The irradiation intensity is kept constant based on the
A displacement sensor for obtaining a correction parameter for measurement . 2. A light projecting spot which is a point-like light pattern.
Light emitting means for irradiating the surface of the object, and light emitting means
Receives the reflected light of the irradiated light and creates an image of the projected spot
Output level ratio according to the position of the formed light receiving spot
Rate changes and the sum of output levels changes according to the amount of received light.
Light receiving means for outputting a pair of position signals
Amplifying means for amplifying each signal, and
Calculation means for calculating the distance to the object based on the
Amplification degree adjusting means for adjusting the amplification degree of the width means;
Displacement provided with intensity adjustment means for adjusting the irradiation intensity of the unit
In the sensor, the calculating means includes a correcting means for calculating a distance to the object by performing a correction calculation by applying a predetermined correction parameter to the signal value of the output of the amplifying means, and an actual value of the distance to the object and the calculating means. Parameter setting means for determining a correction parameter using the calculated value according to the above, amplification degree adjustment means and intensity adjustment means are configured so that the amplification degree and irradiation intensity can be set in a plurality of stages, respectively, the correction parameter The setting means sets the product in two stages in a plurality of combinations in which the product of the amplification degree and the irradiation intensity is constant using a standard object, obtains the signal value of the output of the amplifying means for each combination, and obtains the obtained amplification. estimating the signal value of the output of the amplifying means for a combination of the amplification degree of the irradiation intensity is not measured on the basis of the signal value of the output means, the amplification degree based on the estimation result And obtaining the correction parameters in the measurement of the distance by adjusting the radiation intensity and constant
Strange position sensor.