JPH0814844A - Three-dimensional measurement method for contour - Google Patents

Abstract

PURPOSE:To measure an object contour according to actual arrangement by making a plane correction for contour data obtained from a fringe image via the deformation grating projection method. CONSTITUTION:A beam through a grating 3 and a projection lens 4 after emission from a light source 1a, forms fringe images on the surface of a measurement object at equal pitches (i.e., deformation grating projection method). Then, the picture element data of the fringe images is inputted to a computer 11 through a CCD camera 7, a controller 9 and an input board 10. Thereafter, the grating 3 is moved by 1/4 pitch on the operation of a table controller 12 and the fringe images are similarly photographed. The data so obtained is repeatedly inputted to the computer 11 by four times and jointed across the entire surface of the object, thereby obtaining overall contour data. Then, this data is subjected to a plane correction, using an equation Z=a+bX+cY, where (a), (b) and (c) are conversion parameters, X and Y are the coordinates of contour data for analysis and Z is correction height.

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 non-contactly obtaining the surface shape of an object to be measured.

[0002]

2. Description of the Related Art Conventionally, as a method of highly accurately measuring the surfaces of electrical parts such as mechanical parts and contacts in a non-contact manner, an optical contact probe applying the principle of triangulation is used as a measuring head and measured on an XY table. A target object is installed and the surface shape is measured by driving this XY table, or an electron beam is applied to the measurement target object surface using a scanning electron microscope.
There is a method in which the reflected beam is captured by multiple sensors and the shape is calculated by calculation.

However, an application of the principle of triangulation may not be practical because it takes time to scan an XY table, and an application of a scanning electron microscope requires evaporation as a pretreatment of an object to be measured. Because it is necessary
Strictly speaking, it cannot be said to be non-contact, and the object to be measured may become unusable.

Therefore, as disclosed in Japanese Patent Laid-Open No. 4-278406, a grating is projected from a light source positioned obliquely to the surface of the object to be measured, and the object to be measured shown in FIG.
By using the modified grid projection method that measures the brightness of the striped image A formed on the surface of 2 from an angle different from the projection direction of the grid, the striped image A is processed to calculate the three-dimensional surface shape of the object. There is a fringe scanning method required. The measuring device using the modified grid projection method and the fringe scanning method includes a light source that emits light, a grating that has a constant pitch, and a projection lens that projects light that has passed through the grating as a fringe image onto a measurement target object. , A taking lens for taking a striped image of the surface of the object to be measured, a CCD camera for inputting a striped image taken by the taking lens, and a CCD
And a control unit that calculates and obtains the surface shape of the measurement target object from the image of the camera. This measuring device measures a projection system including a light source, a grating, a projection lens, and an object to be measured in a direction having a certain angle from a normal line direction of the object to be measured, and an imaging system including an object to be measured, a taking lens, and a CCD camera. It is provided in the direction normal to the target object.

[0005]

In the three-dimensional surface shape measuring method using the modified grid projection method and the fringe scanning method described above, the projection system is provided in a direction having a constant angle from the normal direction of the object 2 to be measured. Therefore, the shape data B indicating the three-dimensional surface shape of the object obtained by the stripe scanning method for calculating the stripe image
However, it is in a tilted state as shown in FIG. Therefore, the shape data is displayed in a graph or the like in the tilted state to observe the surface shape of the object.

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 by which the surface shape of an object can be obtained according to the actual arrangement.

[0007]

In order to solve such a problem, according to a surface shape three-dimensional measuring method as set forth in claim 1, a grid projected obliquely onto the surface of the object to be measured is observed from another angle. In the three-dimensional surface shape measuring method for obtaining a plurality of fringe images by the modified grid projection method and for obtaining shape data from the fringe images by the fringe scanning method, the surface shape of the object to be measured is obtained by plane-correcting the shape data. I have a method.

[0008]

According to the method of claim 1, the shape data obtained by the fringe scanning method is plane-corrected so that the shape data does not tilt even when projected from an oblique direction onto the object surface to be measured. Moreover, the surface shape of the object is obtained as it is actually arranged.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a flow chart showing plane correction of a surface shape three-dimensional measuring method of the present invention, and FIG. 2 is a configuration for carrying out the method.

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 to the measurement target object 2 at a constant angle.

Reference numeral 3 denotes a grating, which is configured to allow light to pass through a gap having a constant pitch. This grid is formed of metal, resin, wood, liquid crystal, or the like so as to have two patterns of a place where light passes and a place where light does not pass.

Reference numeral 4 denotes a projection lens, which projects the light passing through the grating 3 onto the surface of the object 2 to be measured to form a striped image having a striped pattern having light and dark. The optical axis of this projection lens 4 is perpendicular to the grating 3 and
It has a certain angle with respect to the normal line. 5 is a measuring table on which the object 2 to be measured is placed.

Reference numeral 6 denotes a photographing lens for photographing a fringe image of the surface of the measurement target object 2 and
It is located right above. By the way, light source 1, grating 3,
The projection lens 4, the optical axis consisting of the measurement target object 2
The optical axis consisting of the object to be measured 2 and the taking lens 6 is called the taking system. Therefore, the projection system should have a certain angle with respect to the normal line of the object to be measured 2, and the imaging system should be
It is provided in the normal direction of 2.

Reference numeral 7 denotes a CCD camera, which inputs a striped image taken by the taking lens 6 as a video.

Reference numeral 8 is a control unit which calculates the surface shape of the object 2 to be measured from the image of the CCD camera 7. The control unit 8 includes a camera controller 9 and an image input board 1
0, a computer 11 and a table controller 12 are provided, and the striped image input to the CCD camera 7 is input to the computer 11 via the camera controller 9 and the image input board 10. Table controller 12 grid
The position of 3 is moved in the pitch direction, and is controlled by the computer 11.

Next, a three-dimensional surface shape measuring method using the above configuration will be described. By turning on the light source 1,
The light that has passed through the grating 3 and the projection lens 4 is
Fringe images are formed on the surface of the substrate at evenly spaced pitches when viewed from the projection system. By observing the fringe image with the photographic lens 6 from the photographic system, it is possible to capture a fringe image composed of a deformed lattice corresponding to the unevenness of the surface of the measurement target object 2. This is the modified grid projection method. After inputting the pixel data of the striped image to the computer 11 via the CCD camera 7, the camera controller 9 and the image input board 10, the table controller 12 moves the lattice 3 in the pitch direction by ¼ pitch of the lattice. . Then, a striped image is captured in the same manner as above. This is repeated four times, and four types of striped images (striped image 1,
The striped image 2, striped image 3, striped image 4) are input to the computer 11 as pixel data.

Assuming that the light intensities of the pixels of each fringe image at any position of the object to be measured 2 are I1, I2, I3, I4, the phase φ at any position can be calculated by the following equation.

Φ = tan ⁻¹ ((I 2 −I 4) / (I 1 −I 3)) By connecting this data over the entire surface of the measurement target object, the entire shape data can be obtained. In addition,
Performing the above calculation is called a stripe scanning method. The shape data B is inclined as shown in FIG.

Next, a method of plane-correcting the shape data B will be described. The equation for plane correction of this shape data is Z = a + bX + cY. In this equation, a, b and c are conversion parameters, X and Y are coordinates of shape data to be analyzed, and Z is a corrected height.

Here, c = 0 can be set by setting the Y axis in parallel with the gaps of the grating 3 having a constant pitch. Then, as shown in FIG.
B = p / n, where p is the vertical pitch of light passing therethrough and n is the number of pixels on the CCD camera 7 per pitch when a striped image is formed on a plane. Further, if the point on the X axis of the shape data where Z = 0 at the analysis region start point is x ₁ , then a = −bx ₁ can be obtained. Therefore, _{Z = -bx 1 + bX = -p} / n (x 1 -X). The corrected height Z at each X position is calculated from this equation, and Z is subtracted from the phase φ of the shape data to obtain plane-corrected shape data. However, in order to subtract the correction height Z from the phase φ, phase jump correction and unit conversion are necessary. The phase jump correction is to make the phase jumping from π to −π continuous. After performing the phase jump correction, the unit conversion is performed as Z (φ) = pφ / (2π) to obtain a correction higher than the phase φ. It becomes possible to subtract Z.

Therefore, from the plane-corrected shape data obtained as described above, the object to be measured according to the actual arrangement is measured.
A three-dimensional surface shape of 2 is required.

Although the grating 3 has two patterns, that is, a place where light passes and a place where light does not pass, it is not limited to this, and it has a liquid crystal pattern in which the amount of passing light gradually changes. You may form. Further, the fringe scanning method using four screens has been described, but the present invention is not particularly limited to four screens, and three or more screens can be used.

[0023]

According to the surface shape three-dimensional measuring method of the first aspect, the shape data obtained by the fringe scanning method is subjected to plane correction so that the shape can be projected even in an oblique direction onto the object surface to be measured. The surface shape of the object can be obtained according to the actual arrangement without tilting the data, which facilitates analysis.

[Brief description of drawings]

FIG. 1 is a flowchart showing plane correction of a surface shape three-dimensional measuring method of the present invention.

FIG. 2 is a block diagram showing a configuration of a three-dimensional surface shape measuring method.

FIG. 3 is a side view showing how the object to be measured is exposed to light.

FIG. 4 is an explanatory diagram showing coordinates for plane correction of the shape data.

FIG. 5 is a plan view showing a striped image on the surface of a measurement target object showing a conventional example of the present invention.

FIG. 6 shows the shape data.

[Explanation of symbols]

 1 Light source 2 Object to be measured 3 Lattice 4 Projection lens 5 Measuring stand 6 Photographing lens 7 CCD camera 8 Controller 9 Camera control 10 Image input board 11 Computer 12 Table controller

Claims (1)

[Claims] 1. A plurality of fringe images are obtained by a modified lattice projection method in which a lattice projected obliquely to the surface of a measurement target object is observed from another angle, and shape data is obtained from the fringe images by a fringe scanning method. In the three-dimensional surface shape measuring method, the surface shape of a measurement target object is obtained by performing plane correction on the shape data.