JP2001183117A - Surface shape measuring device and measuring method - Google Patents

Abstract

(57) [Summary] [PROBLEM] To measure a surface shape by a light beam scanning method,
Provided are a three-dimensional shape measuring apparatus and a measuring method that can easily perform signal analysis and perform accurate shape measurement even when the influence of disturbance is large, and can reduce the size and cost of the apparatus. A laser projector, a laser scanner for scanning a laser beam by rotating a mirror, a light receiving element for distance measurement for receiving reflected light from the surface of the object to be measured and providing distance information, and a laser scanner. The rotation angle detection means 3 is provided, and the output signals of the distance measurement light receiving element and the rotation angle detection means of the mirror are synchronously acquired in time series to perform shape analysis. Further, a general-purpose motor 12 and a crank mechanism 13 are used as a mirror rotation mechanism, and a means for directly measuring the rotation of the shaft such as an optical measurement means or a potentiometer is used as the rotation angle detection means 3 of the laser scanner 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring device and a measuring method for measuring a surface shape of an object surface using a laser beam.

[0002]

2. Description of the Related Art Conventionally, in order to measure a profile of an object surface in a non-contact manner, a light beam such as a laser is projected onto a surface to be measured, and the reflected light is received by a light receiving element, and the distance to the surface to be measured is measured. Is widely performed, and an optical scanning shape measurement method in which projection light is scanned by a rotating mirror is known. This is because, as shown in FIG. 8, a spot-like light beam from the projector 1 is reflected by a mirror 17 that oscillates within a certain angle range and is projected on the surface of the DUT 14,
The projection light is scanned in a plane orthogonal to the rotation axis of the mirror 17. The light reflected from the surface to be measured is received by the light receiving device 2 including the light receiving element 18 and the light receiving lens 6, and distance information between the mirror and the reflection point is obtained. The distance between the projection light and each point on the scanning line AB is obtained. Can be measured, and the profile of the object to be measured can be obtained by analyzing the information together with the information on the projection direction.

The distance measurement is based on the principle of triangulation, and as shown in FIG. 9, a light emitter 1 and a light receiver 2 are installed at a predetermined distance from each other. Looking at P, the fact that the light receiving position Q in the light receiving element 18 changes according to the distance X between the projector 1 and the measurement point P is used. When the distance X becomes longer, the light receiving position Q moves upward in the light receiving surface of the light receiving element 18, and the relationship between the light receiving position and the distance X is constant unless the optical arrangement is changed. Therefore, the distance X can be obtained by analyzing the light receiving position information of the light receiving element 18. In this distance measuring method, even if the laser spot light is scanned with the rotating mirror 17 interposed in the path of the projected light and the reflected light, as long as both light beams are installed so as to be incident on the rotation axis of the mirror, the projector ( The correct distance from the mirror axis to the reflection point can be obtained. In addition, if the positional relationship between the measuring device including the light emitting device, the light receiving device and the rotating mirror and the object to be measured does not change, only the profile of the projected light projected on the scanning surface can be measured.
If the measurement is performed while moving the measuring device with respect to the object to be measured, for example, in a direction perpendicular to the scanning plane of the projection light, the three-dimensional shape of the surface to be measured can be measured.

The information actually required is not the distance in the radial direction from the measuring instrument but the shape of the surface of the object. Therefore, the information in the radial direction is added to the information and converted into a coordinate system fixed to the ground. Must be displayed. For this reason, it is necessary to accurately determine the rotation angle of the reflection mirror. Conventionally, a galvanometer mirror or a polygon mirror is mainly used as the rotation mirror, and information on the radiation direction is obtained from the drive angles of these mirror devices. However, high-precision galvanometer mirrors are expensive. In addition, the size is large, and the measuring instrument incorporating the device is also large. On the other hand, the laser scanning by the polygon mirror has a problem that the correction calculation at the time of measurement is complicated because the rotation center of the mirror and the reflection portion of the laser spot light are relatively displaced. Also, when the optical scanning type surface profile measuring device as described above is applied to an automatic welding robot,
There is a problem that the influence of disturbance due to welding arc light is large, and accurate shape measurement becomes difficult.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an inexpensive and compact measuring device capable of accurately measuring the surface shape even when the influence of a disturbance such as welding arc light is large. It is an object of the present invention to provide a surface shape measuring means using a laser beam which can be used.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a surface shape measuring apparatus of the present invention comprises a laser projector for projecting a laser spot light on an object to be measured. A light receiving element for measuring the distance, which receives the reflected light of the laser spot light scattered and reflected on the surface of the object to be measured, and provides information on the distance to the surface of the object to be measured; a laser projector and a light receiving element for measuring the distance meter; A laser scanner that has a rotating mirror interposed between the laser beam source and the received laser beam for reflecting the laser beam and scans the laser spot light on the object to be measured, a rotating mechanism that rotationally drives the laser scanner, and a laser. A rotation angle detection mechanism for detecting a tilt angle of the scanner; an output signal provided by the distance measuring light-receiving element at predetermined intervals in each direction during scanning; and a rotation angle detection acquired in synchronization with the output signal. Characterized by measuring the surface profile of the workpiece based on the output signal of the structure.

According to the surface profile measuring apparatus of the present invention, since the rotation angle of the laser scanner is directly measured and used as information on the scanning direction, the mirror only needs to be appropriately driven. A simple and compact device can be realized without incorporating an expensive and large precision device such as a galvanometer mirror. Further, by using the laser spot light, the shape can be sufficiently measured even under a disturbance environment such as a welding arc.

Further, the surface shape measuring apparatus of the present invention comprises a laser light source, a scanner angle detecting mirror arranged coaxially with a rotating mirror of a laser scanner and integrally rotating, and a laser through a scanner angle detecting mirror. It is preferable that the rotation angle of the rotation mirror is detected by a rotation angle detection mechanism including a position detection light receiving element that receives the laser light of the light source. Note that a linear C
A CD element and a PSD element can be used as the position detecting light receiving element.

It is preferable that the light receiving element for distance measurement includes a lens optical system so that a focal point is focused on the surface of the light receiving element. When the lens optical system is provided, since the distance to the laser spot changes, the light receiving element surface is arranged obliquely with respect to the optical axis so that the laser spot light within the measurement range is imaged on the light receiving element surface. Is preferred. Also,
As the rotation angle detecting mechanism, a potentiometer or an encoder arranged on the rotation axis of the laser scanner can be used. In the present invention, as a rotating mechanism, a general-purpose motor,
A simple mechanism comprising a crank mechanism for converting the full rotation of the motor into a reciprocating swing within a predetermined angle range can be employed.

In the surface shape measuring method according to the present invention, the laser spot light is scanned in a fan shape on the object to be measured by a rotating mirror, and the reflected light of the laser spot light scattered and reflected on the surface of the object to be measured is transmitted to a light receiving element. Receives light, obtains the distance corresponding to the distance to the surface of the object to be measured based on the light receiving position on the light receiving element at the desired interval, detects the angle of the rotating mirror in synchronization with the desired interval, and detects the same time. Is obtained by developing the coordinate system based on the surface shape of the object to be measured based on the distance to the object to be measured and the angle of the rotating mirror.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a surface shape measuring apparatus according to the present invention.

[0012]

Embodiment 1 FIG. 1 is an explanatory view showing a configuration of a surface shape measuring apparatus according to a first embodiment of the present invention. This device is
Laser projectors (hereinafter simply referred to as projectors) 1a, 1b,
It comprises a light receiver 2, a light receiving element 3 for detecting a scanner angle, a laser scanner 4, signal analysis means, and the like. The first projector 1a is for distance measurement, and the second projector 1b is for scanner angle detection, and each has a laser light source and a projection lens. The light receiver 2 has a distance measuring light receiving element 5 and a light receiving lens 6. The distance measuring light receiving element 5 uses a linear CCD sensor, and the scanner angle detecting light receiving element 3 uses a PSD.

The laser scanner 4 has bearings 8 at both ends.
The light projecting mirror 9, the light receiving mirror 10, and the scanner angle detecting mirror 11 are coaxially arranged on the rotating shaft 7 supported by the above, and the axis of the rotating shaft 7 is located on the reflection surface of each mirror. It has become. The light-projecting mirror 9 and the light-receiving mirror 10 are arranged such that their reflection surfaces are on the same plane, and the light-projecting mirror 9 is such that the light axis of the light projected from the light projector 1a is incident on the axis of the rotation axis. The light receiving mirror 10 is disposed at a position where the reflected light enters the light receiver 2. The mirror 11 for scanner angle detection is mounted at a position corresponding to the light projector 1b at an angle such that the reflected light enters the light receiving element 3 for scanner angle detection. Also, floodlight 1
a and 1b are arranged such that their optical axes pass through the axis of the rotating shaft 7 and enter the rotating shaft 7 at a substantially right angle. The light emitter 1a and the light receiver 2 are arranged at a predetermined distance so that triangulation can be performed.

The laser scanner 4 is rotated about a rotation shaft 7 by a rotation mechanism. In this embodiment, a general-purpose motor 12 and a crank mechanism 13 are used as a rotating mechanism. The crank mechanism 13 converts the entire rotation of the general-purpose motor 12 into a reciprocating motion.
Swings within a predetermined angle range. The principle of shape measurement by the present apparatus is the same as that described above, but the projector 1a
The laser beam condensed in a spot shape by the light projecting lens is reflected by the oscillating light projecting mirror 9 and scanned in a fan shape on a plane orthogonal to the rotation axis 7. The reflected light of the laser spot light scattered and reflected by the surface of the device under test 14 enters the light receiver 2 via the light receiving mirror 10 and is output as a signal output related to the light receiving position of the distance measuring light receiving element 5 (CCD). Information about the distance to the measured surface (reflection point) is output. The CCD element having an appropriate number of pixels (for example, about 2000 pixels) based on the relationship between the measurement range and the resolution is used so that the measurement can be performed with necessary accuracy.

The laser light projected from the light projector 1b is reflected by the scanner angle detecting mirror 11, enters the scanner angle detecting light receiving element 3 composed of PSD, and produces an output corresponding to the peak position of the incident light distribution. . The position of the center of gravity of the incident light distribution is output as a continuous function with a resolution of about 1/1000, and can be measured with a resolution of about 1 minute when converted into the angle of the mirror 11. The output signals of these CCDs and PSDs are input to a signal analyzer 15, which performs an analysis described later, and outputs information on the surface shape of the device to be measured to an output device 16. With the rotation of the laser scanner 4, the position of the reflection point on the DUT 14 changes every moment on the scanning line AB. However, the scanner angle at the time of distance measurement is directly measured, and the position of the reflection point is measured in the irradiation direction of the distance measurement laser light. It is a feature of the present invention that the surface shape of the object to be measured is obtained by performing coordinate calculation based on the coordinates.

FIG. 2 is a perspective view showing a configuration of a sensor head in the surface shape measuring device of the present embodiment. The sensor head includes a projector 19a, 1b, a distance measuring light receiving element 5, a light receiving lens 6, a laser scanner 4, a scanner angle detecting light receiving element 3, and a laser scanner 4 in a case 19 (partially broken away). , And fixed mirrors 20a, 20b, 20c for adjusting the optical axis. Since the distance to the laser spot changes even within the measurement range, the distance measurement light-receiving element 5 has a predetermined light-receiving surface with respect to the light-receiving axis in order to match the imaging position with the light-receiving element surface over most of the measurement range. It is arranged to be inclined at an angle of. By arranging the light receiving surface obliquely in this manner, there is also an effect that the distance to the spot is enlarged and measured. The fixed mirrors 20a, 20b, and 20c are arranged at positions corresponding to the light projectors 1a, 1b and the light receiver, respectively, so that the optical axis is adjusted and the entire sensor head is compact.

Further, since the rotation angle of the laser scanner 4 is directly measured to obtain a value at each time, it is not necessary to drive the laser scanner 4 with a high-precision driving device to perform a precise constant velocity movement. , An ordinary general-purpose rotary motor 1
It is sufficient to assemble the simple link mechanism 13 in FIG. Therefore, the entire device can be formed inexpensively and compactly. Although not shown, if the sensor head is moved in a direction perpendicular to the scanning line by a mechanical scanning mechanism, the surface of the workpiece 14 can be measured surface.

In the present invention, since the measurement range is determined based on the actually measured mirror angle, the laser scanner 4
Instead of swinging by the general-purpose motor 12 and the crank mechanism 13, the rotary shaft 7 may be directly connected to the general-purpose motor and rotated around the entire circumference. Further, a direct connection motor that reciprocates in a predetermined angle range may be used. In addition, the light-emitting mirror 9 and the light-receiving mirror 10 may emit and receive light with a single mirror, and the arrangement of each mirror is not limited to the example of FIG. Further, without separately arranging the scanner angle detecting light projecting device 1b, the laser light of the light projecting device 1a is split into two by a beam splitter or the like, and one of them is made incident on the light projecting mirror 9 and the other is made incident on the scanner angle detecting mirror 11. Such a configuration may be adopted. In addition, P as an angle detecting light receiving element
A CCD element may be used instead of SD.

The method of measuring the surface shape in this embodiment is as follows.
A laser beam scanning means for scanning the laser spot light in a fan-like manner on the object to be measured by a rotating mirror, and receiving the reflected light of the laser spot light scattered and reflected on the surface of the object to be measured, to a distance to the surface of the object to be measured. A light receiving position detecting means for detecting a corresponding light receiving position, and an angle detecting means for detecting an angle of the rotating mirror, wherein an output signal of the light receiving position detecting means and an output signal of the angle detecting means at the same time are output. Obtain and analyze in chronological order to measure the surface shape of the measured object.

FIG. 3 is a schematic diagram for explaining the measurement principle in the present invention. In the figure, the laser spot beam is projected where reflected to the rotation axis position O from the radiation port X mirror 17 of projector 1a forms a reflected light spot P ₁ of the spot-like at the surface of the object 14. When the image of the reflected light point P ₁ is observed by the light receiver 2 via the mirror 17, the reflected point O on the mirror 17 on OY extending the light projecting axis OX is obtained.
Distance from OQ ₁ is observed as a point Q ₁ equal to the distance OP _1. This distance OQ ₁ can be measured by the CCD element of the light receiver 2 based on the principle of triangulation.

In the present invention, the reflection point O on the mirror 17, which is configured to be positioned to the axis of the rotating shaft 7, also the reflection light spot mirror 17 rotates and moves to P ₂ The position of the reflection point O on the mirror 17 does not change, and the reflection point P ₂
Image is observed as a point Q ₂ on the same axis OY. Also the distance OQ ₂ between the new point can be measured in the same way. Further, the projection light reflected by the rotating mirror 17 is scanned on the AB in a plane orthogonal to the rotation axis 7, and the mirror 1
By measuring the angle of 7, the irradiation direction of the laser spot light can be specified.

Therefore, in the measuring method of the present invention, the irradiation direction of the laser spot light is specified by the means for detecting the angle of the rotating mirror, and the distance OP _i to the reflection point is determined.
The by measuring the light position detecting means, it is possible to measure the surface position of the reflection point P _i of the workpiece surface in a very straightforward principle. In particular, when using a light-receiving position detecting means such as a CCD element that reads out measurement results at predetermined intervals, acquire the output signal of the angle detecting means in synchronization with the reading time and analyze the signal at the same time. Accordingly, the surface shape of the object to be measured on the scanning line AB can be accurately measured using the corresponding distance information and angle information.

FIG. 4 is an explanatory diagram of a sampling method of an input signal, FIG. 5 is a block diagram showing a configuration of the input signal, and FIG. 6 is a flowchart showing a calculation procedure. 4, the image processing, the scanner detects the angle V is performed only while it is within a predetermined range of the image measurement start position V ₁ and the end position V _2. During this time, for example, 100 μ
A sampling signal is issued at a predetermined cycle such as about s,
Based on this signal, the signal of the CCD element is read out and taken into the image input board. On the other hand, as shown in FIG. 5, a sampling signal synchronized with the sampling cycle of the CCD image sensor is supplied to the AD conversion board, and a continuously output PSD angle measurement signal is sampled and AD converted in synchronization with the distance information. Later, it is sent to the arithmetic unit. Therefore, the angle information at the same time as when the distance information is obtained is read out and used for the calculation.

As shown in FIG. 6, the calculation procedure first waits for the timing at which the image measurement start position (V ₁ ) is reached based on the scanner angle information. Measured if the scanner angle is determined to be an image measurement start position V ₁ is started (S
1) At each sampling timing by the synchronous clock, distance information on the CCD element is obtained (S).
2). On the other hand, the angle detection information of the laser scanner detected by the PSD element or the like is transmitted to the AD converter as it is detected (S3). Is sampled (S4).

The scanner angle reaches the image measurement end position V ₂ (S5), and stop sampling, based on the pair of the obtained angle information and distance information for each synchronization clock,
The position of the measurement point (reflection point of the projection light) is calculated. V ₁ ~V ₂
By converting the measurement point information between the XY coordinates in the vertical plane (S6), a contour image of the measured surface on the scanning line AB of the scanner is obtained almost online as a ground coordinate system expression,
According to the image processing method of the present invention, which can directly display a contour image on a CRT display or the like, a high-precision surface shape image can be efficiently obtained in a short time with a reduced calculation load.

[0026]

[Embodiment 2] FIG. 7 is an explanatory view showing the configuration of a surface shape measuring apparatus according to a second embodiment of the present invention. In this embodiment, as a scanner angle detecting means, a scanner angle detector 17 for directly measuring the rotation angle of the rotating shaft 7 is used instead of a combination of a projector for detecting a scanner angle, a mirror, and a light receiving element. That is, the apparatus of the second embodiment includes a laser projector 1a, a light receiver 2, a laser scanner 4,
The laser scanner 4 includes a scanner angle detector 17 and a signal analysis output stage. The laser scanner 4 has only a light projecting mirror 9 and a light receiving mirror 10 arranged coaxially. In this embodiment, a magnetic potentiometer is used for the scanner angle detector 17, but this may be a resistance potentiometer or various encoders.

Also in the second embodiment, the general-purpose motor 12 and the crank mechanism 1 are used as the rotating mechanism of the scanner mirror.
The use of 3 is the same as in the first embodiment. Floodlight 1
The configuration, arrangement, and the like of a, the light receiver 2, the light-emitting mirror 9, the light-receiving mirror 10, and the like are almost the same as those in the first embodiment. The principle of shape measurement and the signal analysis method are the same as in the first embodiment, except that the information on the scanner angle input to the signal analyzer 15 is a signal from the scanner angle detector 17. Further, the measurement of the surface shape by moving the sensor head by a mechanical scanning mechanism is the same as in the first embodiment. As a rotating mechanism, in addition to the example shown in FIG. 7, a general-purpose motor alone or a reciprocating rocking motor can be used, and the light-emitting mirror 9 and the light-receiving mirror 10 can be replaced by a single mirror. This is the same as in the first embodiment. The surface shape measuring device of the present invention does not need to use a galvanometer mirror or a polygon mirror as a laser scanner by the configuration as in the first or second embodiment. Simultaneous acquisition of information and information on the scanner angle facilitates signal analysis and enables accurate shape measurement even when the influence of disturbance is great.

[0028]

According to the present invention, since the surface shape is measured by detecting the angle of the laser scanner at the timing of measuring the distance, highly accurate shape measurement can be performed even if the operation of the laser scanner fluctuates. In other words, by measuring the angle of the laser scanner and detecting the irradiation direction of the distance measuring laser, the spatial position of the measurement point (reflection point) is determined based on the distance to the target, so that the operation of the laser scanner is stable. High-precision measurement is possible without performing.

Therefore, it is not necessary to precisely control the rotation operation of the laser scanner, and a simple and inexpensive rotation mechanism can be employed. That is, instead of repeatedly rotating the laser scanner with a carbano mirror or a control motor as in the past, the laser scanner can be driven to rotate only by a general-purpose motor or by a combination of a general-purpose motor and a crank mechanism, and the rotation mechanism is simple. And durability is improved.

In the embodiment of the first embodiment,
The projection mirror and the angle detection mirror of the laser scanner are arranged coaxially, and the axis of the scanner is located on the reflection surface of the mirror, and the distance measurement laser and the angle detection laser are reflected on the axis. Therefore, the reflection point on the mirror does not move due to the rotation of the laser scanner. Therefore, the irradiation direction of the laser for distance measurement can be directly obtained from the angle information of the laser scanner without complicated calibration, and the shape can be easily analyzed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of a surface shape measuring device according to a first embodiment of the present invention.

FIG. 2 is a perspective view illustrating a configuration of a sensor head according to the first embodiment.

FIG. 3 is an explanatory diagram of a measurement principle in the surface shape measurement method according to the first embodiment.

FIG. 4 is an explanatory diagram of a sampling method of an input signal in the image processing of the first embodiment.

FIG. 5 is a block diagram illustrating a configuration of an input signal in image processing according to the first embodiment.

FIG. 6 is a flowchart illustrating a calculation procedure in image processing according to the first embodiment.

FIG. 7 is an explanatory diagram showing a configuration of a surface shape measuring device according to a second embodiment of the present invention.

FIG. 8 is an explanatory diagram of a conventional optical scanning type shape measuring method.

FIG. 9 is an explanatory diagram of the principle of the triangulation method.

[Explanation of symbols]

 1, 1a, 1b Laser projector 2 Receiver 3 Scanner angle detecting light receiving element 4 Laser scanner 5 Distance measuring light receiving element 6 Light receiving lens 7 Rotating axis 8 Bearing 9 Light emitting mirror 10 Light receiving mirror 11 Scanner angle detecting mirror DESCRIPTION OF SYMBOLS 12 General-purpose motor 13 Crank mechanism 14 Device under test 15 Signal analyzer 16 Output device 17 Mirror 18 Light receiving element 19 Case 20a, 20b, 20 Fixed mirror

Continuing from the front page (72) Inventor Takao Kanamaru 118 Futatsuka Noda-shi, Chiba Prefecture Kawasaki Heavy Industries Noda Factory (72) Inventor Shutake Miki 118 Futatsuka Noda-shi Chiba Prefecture Kawasaki Heavy Industries Noda Factory (72) Inventor Shigeru Nakayama 118 Futatsuka, Noda City, Chiba Prefecture Kawasaki Heavy Industries Noda Factory Co., Ltd. F-term (reference)

Claims (8)

[Claims] 1. A laser projector for projecting a laser spot light onto an object to be measured, and a reflected light of the laser spot light scattered and reflected on the surface of the object to be received to give information on a distance to the surface of the object to be measured. A distance measuring light-receiving element, and a rotary mirror interposed between the laser projector and the distance-measuring light-receiving element and the DUT to reflect the projected laser spot light and the received laser spot light. A laser scanner that scans a laser spot light on an object to be measured, a rotation mechanism that rotationally drives the laser scanner, and a rotation angle detection mechanism that detects an inclination angle of the laser scanner. The surface shape of the object to be measured is determined based on an output signal provided by the light receiving element at predetermined intervals in each direction during scanning and an output signal of the rotation angle detection mechanism acquired in synchronization with the output signal. Surface shape measurement device to measure. 2. The method according to claim 1, wherein the light receiving element for distance measurement is a linear CCD.
The surface shape measuring device according to claim 1, wherein the surface shape measuring device is an element. 3. The apparatus according to claim 2, wherein the rotation angle detecting mechanism includes a laser light source,
A scanner angle detection mirror arranged coaxially with the rotating mirror of the laser scanner and integrally rotating, and a position detection light receiving element for receiving the laser spot light of the laser light source through the scanner angle detection mirror, 3. The surface shape measuring device according to claim 1, wherein the rotation angle of the rotating mirror is detected. 4. The surface shape measuring apparatus according to claim 3, wherein said position detecting light receiving element is a PSD element. 5. The device according to claim 1, wherein the position detecting light-receiving element includes a lens optical system, and the light-receiving element is arranged so that a focal point is focused on an element surface in a distance measurement range in relation to the lens optical system. 5. The surface shape measuring device according to 3 or 4. 6. The surface shape measuring apparatus according to claim 1, wherein the rotation angle detecting mechanism comprises a potentiometer or an encoder disposed on a rotation axis of the laser scanner. 7. The surface shape according to claim 1, wherein said rotating mechanism comprises a general-purpose motor and a crank mechanism for converting the full rotation of said motor into a reciprocating swing within a predetermined angle range. Measuring device. 8. A laser mirror scans the laser spot light in a fan-shaped manner on the object to be measured by a rotating mirror, and receives the reflected light of the laser spot light scattered and reflected on the surface of the object to be detected by a light receiving element, and receives the light at predetermined intervals. The distance corresponding to the distance to the surface of the object to be measured is obtained based on the light receiving position on the element, the angle of the rotating mirror is detected in synchronization with the expected interval, and the distance and the rotating mirror angle at the same time are detected. A method for measuring the surface shape of an object to be measured, based on the method.