JP2985635B2 - Surface shape 3D measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-dimensional surface shape measuring method for determining the surface shape of an object to be measured without contact.

[0002]

2. Description of the Related Art Conventionally, as a method for measuring the surface of an electric component such as a mechanical component or a contact point with high accuracy without contact, an optical stylus applying the principle of triangulation is used as a measuring head and measured on an XY table. A target object is set up, a surface shape is measured by driving the XY table, or an electron beam is applied to a target surface using a scanning electron microscope.
There is a method in which a reflected beam is captured by a plurality of sensors and converted into a shape by calculation.

As shown in Japanese Patent Application Laid-Open No. 4-278406, a grid having an illuminance distribution of a sine state is projected from an oblique direction to an object plane to be measured, and the brightness of a fringe image formed on the object plane is projected on the grid. There is a fringe scanning method for calculating a three-dimensional surface shape of an object by measuring and calculating from an angle different from the direction.

[0004]

The three-dimensional surface shape measuring method described above has the following problems.

In some cases, the application of the principle of triangulation is not practical because scanning of the XY table requires time, and in the case of using a scanning electron microscope, evaporation is required as a pretreatment of the object to be measured. Therefore, it cannot be said that the contact is strictly non-contact, and the object to be measured cannot be used.

In the fringe scanning method, a CCD camera used for normal image input has a gray scale resolution of 8 bits, ie, 256 bits.
Since the gradation is reduced to about 1/3 due to the influence of noise, the reliability of the surface shape data decreases,
When the influence is large, the determination of the unevenness may be erroneously made. Further, similarly, due to the influence of the gradation, a phase jump phenomenon occurs when the phase calculation is performed. In particular, the error in the inclined portion becomes large, and the shape determination in the inclined portion may be erroneously performed. In order to solve such a problem, it is conceivable to remove the grid and input a grayscale image separately. However, removing the grid requires a physical moving operation, and requires labor and time.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a three-dimensional surface shape measuring method in which an error in shape determination hardly occurs.

In order to solve such a problem, a three-dimensional surface shape measuring method according to claim 1 uses a modified grid projection method in which a grid projected from a certain direction with respect to an object surface to be measured is observed from another angle. Types of fringe images are obtained, shape data is obtained from the fringe images by a fringe scanning method, and the measurement object
Light intensity I1, I of a pixel of each stripe image at an arbitrary position on the body
From 2, I3 and I4, (I1 + I2 + I3 + I4) / 4
The gray value expressed by
The image data is obtained by connecting the entire surface of the body to obtain the image data, and the shape data and the image data are arithmetically processed to obtain the surface shape of the object to be measured.

[0009]

According to the first aspect of the present invention, the shape data and the image data of the object surface to be measured are simultaneously obtained from the stripe image obtained by the modified grid projection method, and these can be processed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a system configuration diagram of the present invention. The three-dimensional surface shape measuring method includes a sensor unit A and a control unit.
The surface shape of the object to be measured is measured using B as a main component.

Reference numeral 1 denotes a light source, which has a lamp 1a, a lens 1b, and a reflector 1c and emits light. The light passes through a grating and a projection lens, which will be described later, and is applied at a certain angle with respect to the normal to the object to be measured.

Reference numeral 2 denotes a grating, which is configured so that light passes through a gap having a constant pitch. The grating may be formed not only of two patterns of light passing areas and non-light passing areas but also of a liquid crystal pattern of a sine-wave-shape gray-scale image in which the light passing amount changes gradually.

Reference numeral 3 denotes a projection lens which projects the light passing through the grating 2 onto the surface of the measurement object 4 to form a fringe image. The optical axis of the projection lens 3 is perpendicular to the grating 2 and has a certain angle with respect to the normal to the object 4 to be measured. 5 is a measuring table.

Reference numeral 6 denotes a photographing lens for photographing a fringe image of the surface of the object 4 to be measured.
It is provided directly above. The fringe image taken by the taking lens 6 is input to the CCD camera 7. The above is the structure of the sensor unit.

The control unit inputs the stripe image input to the CCD camera 7 to the computer 10 via the camera controller 8 and the image input board 9.

Reference numeral 11 denotes a table controller,
Is moved in the pitch direction, and is connected to the computer 10.

Next, a three-dimensional surface shape measuring method using the above configuration will be described. By turning on light source 1,
The light that has passed through the grating 2 and the projection lens 3
A fringe image is formed on the surface of the image. By observing it with a photographing lens 6 provided at another angle, it is possible to photograph a fringe image composed of a deformed grating corresponding to the surface irregularities. After the pixel data of the stripe image is input to the computer 10 through the CCD camera 7, the camera controller 8, and the image input board 9, the grid 2 is moved by the table controller 11 in the pitch direction by 1/4 pitch of the grid. . Then, a stripe image is photographed as described above. This is repeated four times, and four types of stripe images (strip image 1, stripe image 2, stripe image 3,
The fringe image 4) is input to the computer 10 as pixel data.

Assuming that the light intensities of the pixels of each fringe image at an arbitrary position on the object to be measured are I1, I2, I3, and I4, the phase φ at an arbitrary position can be obtained by the following equation.

Φ = tan ⁻¹ ((I 2 −I 4) / (I 1 −I 3)) By joining this data over the entire surface of the measurement target object, overall shape data can be obtained. In addition,
Performing the above operation is called a fringe scanning method. Also,
Although the fringe scanning method using four screens has been described, the present invention is not particularly limited to four screens and can be used on three or more screens.

Next, the gray value g at an arbitrary position of the object to be measured is obtained by the following equation. g = (I1 + I2 + I3 + I4) / 4 By linking this data over the entire surface of the measurement target object, the entire image data represented by shading can be obtained. Therefore, there is no need to input a new grayscale image.

From the shape data and image data obtained as described above, an accurate 3
A two-dimensional surface shape is obtained, and shape data and image data are determined using each threshold value as shown in FIG. 2, so that defects such as surface flaws and adhesion can be easily obtained.

Next, a modification of the present invention is shown in FIGS. FIG. 3 shows a first modification, in which a projection system including a light source 1, a grating 2, and a projection lens 3 is provided right above a measurement object 4;
An imaging system including an imaging lens 6 and a CCD camera 7 has a certain angle with respect to the normal line of the object 4 to be measured. FIG. 4 shows a second modification, in which a projection system,
The imaging system has a certain angle with respect to the normal line of the object 4 to be measured. In the case of FIG. 4, the pitch of the grid to be photographed is enlarged as compared with FIGS.

[0023]

According to the surface shape three-dimensional measuring method of the present invention, the shape data and the image data of the object surface to be measured are simultaneously obtained by the stripe image obtained by the modified grid projection method.
Since these can be arithmetically processed, the shape of the object surface to be measured can be accurately determined in a short time.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing an embodiment of the present invention.

FIG. 2 shows the processing algorithm.

FIG. 3 is a system configuration diagram showing a first modified example thereof.

FIG. 4 is a system configuration diagram showing a second modified example thereof.

[Explanation of symbols]

 1 Light source 2 Grid 3 Projection lens 4 Object to be measured 5 Measuring table 6 Shooting lens 7 CCD camera 8 Camera control 9 Image input board 10 Computer 11 Table controller

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01B 11/00-11/30 102 G06T 7/00-9/20

Claims (1)

(57) [Claims] 1. Four types of fringe images are obtained by a modified grid projection method in which a grid projected from a certain direction on a measurement object surface is observed from another angle, and shape data is obtained from the fringe images by a fringe scanning method. At an arbitrary position of the object to be measured
Light intensity I1, I2, I3, I4 of the pixel of each stripe image
The gray value represented by (I1 + I2 + I3 + I4) / 4
And the gray value is distributed over the entire surface of the object to be measured.
A surface shape three-dimensional measurement method, wherein image data is obtained by joining together , and the shape data and the image data are subjected to arithmetic processing to obtain the surface shape of the object to be measured.