JPH1054711A - Method of measuring surface shape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To judge the unevenness of the surface of an object to be measured, and measure the quantity of unevenness with precision not more than the interval of moire fringes. SOLUTION: The polarized beam emitted from a laser beam source 1 is extended by a beam expander 2 and made into parallel beams by a lens 3. The parallel beams are emitted to the surface of a object to be measured 5 through a flat grid 4 to project the shadow of the flat grid 4 to the object surface. The shadow is observed by a CCD camera 8 through the original flat grid 4, a condenser 6 and a polarizer 7. A holder 9 with a moving stage for mounting the object to be measured 5 is quantitatively movable in the vertical direction to the grid surface of the flat grid 4 by a stepping motor. When the object 5 is moved in the direction leaving the grid surface and observed, the moire fringes appearing on the object surface are moved so that the unevenness can be judged, and the quantity of the unevenness can be also measured by superposing the moire fringes on each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the shape of an object surface using contour moire fringes.

[0002]

2. Description of the Related Art A moire fringe is another fringe pattern generated as a trajectory of an intersection when two straight line groups or curve groups are superimposed. The method of obtaining the surface shape of an object using the moire fringes is called contour moire fringe measurement (moire topography). In a grid-illuminated moire topography, a shadow of a plane grid is emitted from a point-like or slit-like light source. The light is projected onto the surface of the object to be measured, and this shadow is obtained at the observation point through the original grid, making it possible to perform non-contact measurement of the surface shape using moire fringes generated by the shadow of the plane grid. is there.

[0003]

In the contour moiré fringe measurement, fringes are formed on the surface of the object to be measured at equal intervals perpendicular to the lattice plane, and the shape is observed quickly and accurately. However, this method cannot determine the relative height of the contour lines, that is, the so-called unevenness. Further, in order to measure the unevenness with a finer accuracy, contour moire fringes with a narrow interval are used, and it is necessary to make the pitch of a grating used finer. In such a case, there is a problem that the contrast is reduced.

An object of the present invention is to solve the problems of the prior art and to obtain a surface shape measuring method capable of determining unevenness on the surface of an object to be measured and measuring the amount of unevenness with an accuracy equal to or less than the interval between moire fringes. Aim.

[0005]

According to the surface shape measuring method of the present invention, a shadow of a plane grating is projected on the surface of an object to be measured by light emitted from a point-like or slit-like light source, and this shadow is used as an original. In the method of obtaining the surface shape of the object using the moire fringes generated by the shadow of the plane grid obtained at the observation point through the grid, the object to be measured is moved in the vertical direction with respect to the grid plane of the plane grid. The method is characterized in that irregularities on the surface are determined.

In the present invention, the object to be measured is moved in a direction perpendicular to the lattice plane, and the unevenness can be determined from the moving direction of the moire fringes on the surface of the object to be measured with respect to the moving direction. Furthermore, by quantifying the amount of displacement of the irregularities from the amount of movement of the object to be measured in the direction perpendicular to the lattice plane and the positions of moiré fringes on the surface of the object before and after the movement, the amount of unevenness on the surface of the object is measured. It is more preferable that the measurement can be performed with an accuracy equal to or less than the interval of the contour moire fringes.

That is, contour moire fringes appear in principle by a relative distance to the lattice plane. Thus, when the object to be measured moves away from the lattice plane, the moiré fringes move in the convex direction of the object surface, and when it approaches the lattice plane, the moiré fringes move in the concave direction. Therefore, the unevenness can be determined by observing the moving direction of the moire fringes when the object to be measured is moved from the lattice plane in the vertical direction. Further, since the displacement amount (movement amount) of the relative distance between the object and the lattice plane is equal to the height difference (amount of unevenness) between the positions before and after the movement of the moire fringes on the object surface, the quantitative From the measurement of the moving amount and the observation of the moving position of the moiré fringes, it is possible to measure the fine unevenness less than the interval of the contour moiré fringes.

[0008] These methods are not limited to the apparatus and the object to be measured, as long as they are measurement methods using contour moire fringes.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A contour moire fringe measuring apparatus according to an embodiment of the present invention shown in FIG. 1 will be described. Polarized light emitted from the laser light source 1 is expanded by the beam expander 2 and converted into a parallel light by the lens 3. The parallel rays are radiated to the surface of the DUT 5 through the plane grating 4 and the shadow of the plane grating 4 is projected on the surface of the DUT. This shadow is passed through the original plane grating 4, condensing lens 6 and polarizer 7 to the CCD.
Observe with the camera 8. The DUT 5 is attached to a holder 9 having a moving stage. This stage can be quantitatively moved in a direction perpendicular to the lattice plane of the plane lattice 4 by a stepping motor.

In the embodiment, the surface of a disk-shaped object having a diameter of 130 mm was observed. A Ronchi grating having a pitch of 50 μm was used as the plane grating. The irradiation angle of light on the plane grating is 45
゜. The contour moiré fringes appear at intervals of 25 μm. Further, in the present example, observation was performed by moving the holder moving stage relatively away from the first observation position by 5 μm from the lattice plane to 25 μm.

FIG. 2 shows an observed contour moire fringe image of the object surface. Each numerical value below the image in FIG. 2 indicates the disk moving distance (μm). When the object to be measured is moved in a direction away from the lattice plane as shown in FIG. 2, the moire fringes appearing on the object surface move, and the object surface of the embodiment has a mainly concave shape. Can be determined. Further, as shown in FIG. 3, when the moiré fringes obtained in the observation of the embodiment of FIG.
The amount of unevenness at m intervals can be measured.

[0012]

As described above, according to the measuring method of the present invention, irregularities on the surface of the object to be measured can be determined, and the amount of the irregularities can be measured with an accuracy equal to or less than the interval between moire fringes.

[Brief description of the drawings]

FIG. 1 shows the configuration of a measuring device using the measuring method of the present invention.

FIG. 2 is a contour moire fringe image of an object surface observed by the method of the present invention.

FIG. 3 shows relative contours of the object surface measured according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser light source 2 Beam expander 3 Lens 4 Planar grating 5 Object to be measured 6 Condensing lens 7 Polarizer 8 CCD camera 9 Holder with moving stage

Claims (2)

[Claims] 1. A shadow of a plane grating is projected on a surface of an object to be measured by light emitted from a point-like or slit-like light source,
In the method of obtaining this shadow at the observation point through the original grid and obtaining the object surface shape using the moire fringes generated by the shadow of the plane grid, moving the object to be measured in the vertical direction with respect to the grid plane of the plane grid A surface shape measuring method characterized in that irregularities on the surface of an object to be measured are determined by the method. 2. An object to be measured is moved in a direction perpendicular to a lattice plane of a plane grating, and an amount of irregularities on the surface of the object to be measured is determined by a contour moire fringe based on a movement amount of the object to be measured and a movement amount of the observed contour moire fringes. 2. The surface shape measuring method according to claim 1, wherein the measurement is performed with an accuracy equal to or less than the interval of.