JPH0989521A - Calibration method in laser distance measuring device - Google Patents

Abstract

(57) Abstract: A calibration method in a laser distance measuring device capable of easily measuring a displacement amount of an object to be measured over a wide range. SOLUTION: The object to be measured 3 is irradiated with a laser beam 4,
When the reflected light beam 5 is received by the CCD image sensor 7 through the lens 6 and this light receiving position is input to a predetermined arithmetic expression to measure the distance of the object to be measured, the parameters included in the above arithmetic expression Is a method of calibrating a plurality of known displacement amounts to the calibration measurement object 3A, obtains measurement data according to the displacement amounts, and uses these measurement data to set the above-mentioned respective parameters. This is a method of estimation by the least squares method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a calibration method in a laser distance measuring device, and more specifically, it calibrates parameters of an arithmetic expression used when measuring a distance to an object to be measured by the laser distance measuring device. Regarding the method.

[0002]

2. Description of the Related Art There is a laser distance measuring device utilizing a laser beam for measuring the size of an object in a non-contact manner. Some of the laser distance measuring devices are based on the triangulation method.

In the laser distance measuring device using the triangulation method, as shown in FIG. 2, a laser beam 53 is irradiated from a laser beam irradiator 51 to an object 52 to be measured, and the reflected laser beam 54 is emitted. Through lens 55 to CCD
By receiving light at the linear image sensor 56 and detecting the light receiving position (actually, the distance from the center of the image sensor to the light receiving point) Δx at the image sensor 56,
The distance Δd from the reference position a corresponding to the center position of the image sensor 56 to the object to be measured 52 is obtained.

That is, there is a fixed relationship between the distance (displacement amount) Δd from the reference position a to the object to be measured 52 and the distance Δx to the light receiving position on the image sensor 56. The distance (displacement amount) Δd to the object to be measured 52 was measured.

And, regarding the above-mentioned certain relationship,
Conventionally, it has been obtained by assuming a quadratic curve or a cubic curve and approximating with a regression line.

[0006]

However, when approximating with the above regression line, the range of measurement that can be approximated is limited, and when measuring in a wide range, the regression line is changed for each predetermined section. The spline curve needs to be approximated in its entirety, and therefore requires a very troublesome calculation, and has a drawback that the distance itself, that is, the entire distance cannot be measured.

Therefore, it is an object of the present invention to provide a calibration method in a laser distance measuring device that can solve the above problems.

[0008]

In order to solve the above-mentioned problems, a calibration method for a laser displacement meter of the present invention comprises a laser beam irradiator and a reflected beam of a laser beam radiated from the irradiator to an object to be measured. The image sensor that receives light through the lens and the light receiving position of this image sensor are detected, and the distance from the reference position to the object to be measured is the distance from the object to be measured to the lens, or the distance from the lens to the image sensor. And a method of calibrating the parameters of the above-mentioned arithmetic expression in a laser distance measuring device having an arithmetic processing unit that obtains based on an arithmetic expression having an irradiation optical axis of a laser beam and its reflected optical axis as a parameter. A plurality of known displacements are given to the measuring object for measurement, and the measurement data is acquired according to the displacements, and these measurement data are used to determine the parameters described above. The chromatography data, a method of estimating by the least square method.

According to the above construction, when the distance from the reference position to the object to be measured is calculated by an arithmetic expression, the parameter contained in the arithmetic expression is used to displace the calibration measuring object and to calculate these displacements. By applying the least squares method using the measured data, it is possible to calibrate to a value with very few errors, and therefore it is possible to measure the displacement amount of the DUT over a wide range and to measure the distance to the DUT. Can also be obtained over a wide range.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A calibration method for a laser distance measuring apparatus according to an embodiment of the present invention will be described below with reference to FIG.

First, a laser distance measuring device to which the calibration method according to the present invention is applied will be described. As shown in FIG. 1, a laser distance measuring device 1 includes a laser beam irradiator 2
And a CCD for receiving a reflected beam 5 of a laser beam 4 emitted from the irradiator 2 onto the DUT 3 through a lens 6.
The image sensor 7 and the light receiving position of the image sensor 7 are detected, and the distance Δd from the predetermined reference position A to the DUT 3, the distance S from the DUT 3 to the lens 6, and the image sensor from the lens 6 are detected. 7 and the irradiation optical axis of the laser beam 4 and the reflected optical axis from the reference position A (optical axis of the reflected light beam passing through the central position of the image sensor 7)
A computer device (arithmetic processing unit) that is obtained based on the arithmetic expression shown in the following equation (1) using the angle K formed by
8 is provided, and a calibration auxiliary device 9 for calibrating the values of these respective parameters is further provided.

The calibration auxiliary device 9 includes a calibration measurement object 3A used for performing calibration, and the calibration measurement object 3A.
A moving device (for example, a motor) 11 for moving A in the irradiation direction of the laser beam 4 and a drive unit 12 for moving the moving device 11 by a predetermined distance according to an instruction from the computer 8 are provided. The light receiving position signal from the image sensor 7 is sent to the amplifier 13, A
It is input to the computer device 8 via the / D converter 14.

Next, in the computer device 8,
The calculation formula (1) to be calculated will be described. This formula
In (1), when the DUT 3 (3A) moves (displaces) in the irradiation optical axis direction (y-axis direction) of the laser beam 4, the light receiving position of the reflected beam 5 detected by the image sensor 7 changes. .
At this time, the relationship as shown in equation (1) below is established.

Δd = Δx · S / (f · sin K−Δx · cos K) (1) However, Δd: displacement of the object to be measured (movement amount from the reference position) Δx: image sensor Change in the light receiving position of S: Distance from the object to be measured at the reference position to the lens f: Distance from the lens to the image sensor K: Angle between the laser beam and the optical axis of the lens (reflected optical axis at the reference position) Shown respectively.

Therefore, the amount of movement of the object 3 to be measured in the y-axis direction, that is, the amount of displacement Δd is obtained from the above equation (1), and for example, at the center position B of the lens 6 which is known in advance,
If the displacement amount Δd is added to the distance C to the reference position A corresponding to the center position of the image sensor 7, the distance L from the center position B of the lens 6 in the irradiation optical axis direction (y-axis direction).
(C + Δd) can be obtained.

In the above equation, S,
The exact values of f and K are unknown and it is necessary to estimate them as accurately as possible. Hereinafter, a method of estimating the values of S, f, and K as accurately as possible, that is, calibrating, will be described.

First, the displacement amount Δd obtained by using * S, * f, * K as provisional values is Δ * d (* S, * f, * S, *
K) and the true values are S, f, and K, the provisional value *
Between S, * f, * S, and * K, errors ΔS, Δf, and Δ
K is occurring.

That is, the true value is expressed by the following equations (2) to (4). S = * S-ΔS (2) f = * f-Δf (3) K = * K-ΔK (4) where the displacement of the calibration measurement object 3A Since the true value of is known by the computer device 8, if this true value is known Δd, the residual U is expressed by the following equation (5).

[0019]

[Equation 1]

Here, if Δ * d (S, f, K) ≈Δd, the above equation (5) can be expressed as the following equation (6). U = Δ * d _S × ΔS + Δ * d _f × Δf + Δ * dK _K × ΔK (6) However, in the formula (6),

[0021]

[Equation 2]

Is represented by Actually, partial differentiation is as shown in the following equations (7) to (9).

[0023]

(Equation 3)

However, the value of (S, f, K) is a provisional value (*
S, * f, * K). Then above
The least squares method is applied to the equation (6) to obtain an approximate solution of ΔS, Δf, ΔK.

First, assuming that the objective function is U ² , U ² is expressed by the following equation (10).

[0026]

[Equation 4]

When the above equation (10) is partially differentiated by ΔS, Δf, and ΔK, the following equations (11) to (13) are obtained.

[0028]

(Equation 5)

The above equations (11) to (13) are set to zero as shown in the following equation (14).

[0030]

(Equation 6)

By solving the above equation (14), (ΔS,
Δf, ΔK) is obtained. However, since the partial differentiation of Eqs. (7) to (9) is evaluated by (* S, * f, * K), this is not the final value, and the above Eqs. (2) to (4) are used. Therefore, as shown in the following equations (15) to (17), the estimated value (* S ′, *
f ', * K') is calculated.

[0032]

[Equation 7] * S '= * S-ΔS ··· (15) * f ′ = * f-Δf ··· (16) * K ′ = * K-ΔK ··· (17) Above (* S ', * f', * K ') is calculated several times to obtain a convergent solution. That is, the calibration measurement object is moved several times, and calculation is performed using these measurement data.
This convergent solution is an estimated value of each parameter to be obtained and is very close to the true value.

As described above, when the distance from the reference position to the object to be measured is obtained by an arithmetic expression, the parameters included in the arithmetic expression can be calibrated to a more true value, and therefore the conventional method can be used. As described above, compared with the case of using the spline curve, the displacement amount of the measured object can be easily measured over a wide range, and the distance to the measured object can also be measured over a wide range.

[0034]

As described above, according to the configuration of the present invention, when the distance from the reference position to the object to be measured is calculated by an arithmetic expression, the parameter included in the arithmetic expression is used as the calibration measuring object. Since the measurement data is applied and the least-squares method is applied for calibration along with the displacement, the error can be made very small, which is different from the case where the spline curve is used as in the past. The displacement amount of the measured object can be easily measured over a wide range, and the distance to the measured object can also be measured over a wide range.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a laser distance measuring device according to an embodiment of the present invention.

FIG. 2 is a principle diagram illustrating a conventional laser distance measuring method.

[Explanation of symbols]

 1 Laser Distance Measuring Device 2 Irradiator 3 Object to be Measured 3A Measuring Object for Calibration 4 Laser Beam 5 Reflected Ray 6 Lens 7 Image Sensor 8 Computer Device 9 Auxiliary Equipment for Calibration

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Masao Kinoshita 5-3-8 Nishikujo, Konohana-ku, Osaka City, Osaka Prefecture Hitachi Shipbuilding Co., Ltd. (72) Seiichi Maeda, Nishikujo, Nishinojo-ku, Osaka City, Osaka Prefecture 3-28, Hitachi Shipbuilding Co., Ltd. (72) Haruhiko Yoshida 5--3-28, Nishikujo Nishikonohana-ku, Osaka City, Osaka Prefecture Hitachi Shipbuilding Co., Ltd.

Claims (1)

[Claims] 1. A laser beam irradiator, an image sensor for receiving a reflected light beam of a laser beam emitted from the irradiator to an object to be measured through a lens, and detecting a light receiving position in the image sensor. , The distance from the reference position to the object to be measured, the distance from the reference position to the lens, the distance from the lens to the image sensor, and the angle between the irradiation optical axis of the laser beam and the reflection optical axis from the reference position are used as parameters. A method for calibrating the parameters of the above-described arithmetic expression in a laser distance measuring device having an arithmetic processing unit obtained based on an arithmetic expression, wherein a plurality of known displacement amounts are given to a calibration measurement object, A laser distance measuring device characterized by obtaining measured data by using the measured data and estimating each of the above parameters by the least square method using these measured data. Kick calibration method.