JP2007198988A - Measuring method and device of surface shape error - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device capable of inspecting a shape error from a design value of a component or a product in various manufacturing industries, easily and highly accurately in the noncontact state, by enabling measurement of a surface shape error of an inspection object. <P>SOLUTION: When the surface shape of the inspection object has no error to a design value, a projection lattice designed beforehand so that a projected deformed lattice image becomes linear is projected by a projector onto the object surface having an actual error, and the acquired deformed lattice image is analyzed. Hereby, even in the case of an object having a step or a groove or having a steep undulation, the surface shape error of an actual measuring object having an error can be measured and inspected highly accurately in the noncontact state by determining easily the order of the deformed lattice, and by preventing the line width of the deformed lattice from being widened and preventing brightness of the deformed lattice image from being weakened. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method and apparatus for easily and accurately measuring an error of a surface shape by projecting a lattice created according to a design value of the surface shape of the inspection object onto the inspection object. .

  As a conventional surface shape error measuring method and apparatus, a linear grid is projected onto an object having a surface shape to be inspected, and the surface shape is measured from a projected deformed grid image (called a grid projection method). Patent Documents 1 and 2), and then there was a method and apparatus for obtaining an error by subtracting the design value of the surface shape from it.

JP-A-7-208950 JP-A-8-2014844

  When measuring the error of the shape of a target with a step or groove using the conventional normal grid projection method, the lattice image projected on the target (called a deformed lattice image) is discontinuous before and after the step or groove. Therefore, the order of the grid cannot be determined, and therefore the shape error may not be measured correctly.

  Also, in the conventional normal grid projection method, when a straight grid is projected onto a steeply shaped part, the line width of the deformed grid widens and the luminance becomes weak, so the grid image cannot be read and measurement is difficult. There was a case.

  The present invention solves the above-mentioned conventional problems, and can easily determine the order of the deformed grid even when measuring the shape error of a target having a step, a groove, or a shape with severe undulations. It is an object of the present invention to provide a shape error measuring method and apparatus using a grid projection method in which the line width is not increased and as a result the brightness of the grid image is not decreased.

  In order to solve the above problems, the present invention calculates in advance so that the deformed grid image projected on the surface of the measurement object becomes a parallel straight line group when the surface shape of the measurement object has no error compared to the design value. By analyzing the deformed grid image generated by projecting the projection grating created in this way onto the surface of the actual measurement object manufactured according to the design value, the actual measurement object manufactured according to the design value is analyzed. There is provided a shape error measuring method characterized by a shape error measuring method characterized by measuring a surface shape error.

  Furthermore, when the surface shape of the measurement target has no error compared to the design value, a projection grid created and created in advance so that the deformed grid image projected on the surface of the measurement target becomes a parallel straight line group, Inspecting the surface shape error of the actual measurement object having the above error by visually monitoring the deformed grid image generated by projecting on the surface of the actual measurement object manufactured according to the design value. A shape error inspection method is provided.

  In addition, when the surface shape of the measurement target has no error compared to the design value, a liquid crystal projection lattice created by calculating in advance so that the deformed lattice image projected on the surface of the measurement target becomes a parallel straight line group. By writing a deformed grid image generated by projecting the projection grid written on the liquid crystal panel on the surface of the actual measurement object written according to the design value written on the panel with a video camera and analyzing it with a computer The present invention provides a shape error measuring apparatus for measuring a surface shape error of an actual measurement object manufactured according to the erroneous design value.

  In addition, when the surface shape of the measurement target has no error compared to the design value, a liquid crystal projection lattice created by calculating in advance so that the deformed lattice image projected on the surface of the measurement target becomes a parallel straight line group. By writing on the panel and monitoring the deformed grid image generated by projecting the pattern written on the liquid crystal panel onto the surface of the actual measurement object that has an error compared to the design value, the error is obtained. A shape error inspection apparatus characterized by inspecting a surface shape error of an actual measurement object is provided.

  In the present invention, when the surface shape of the object to be inspected has no error with respect to the design value, a projection grating designed in advance so that the projected deformed grating image becomes a group of parallel straight lines has an actual error. Because it is based on the principle of projecting onto the surface of a target object, the order of the deformed grid can be easily determined even for objects with steps, grooves, or undulating shapes. Since the width is not widened and the brightness of the image of the deformed grating does not become weak, the position of the deformed grating can be read accurately, and a shape error can be easily and accurately measured even for a complex shaped object.

  The best mode for carrying out the surface shape meter error measuring method and apparatus according to the present invention will be described below with reference to the drawings based on the embodiments.

  FIG. 1 shows an outline of an embodiment of a surface shape error measuring apparatus according to the present invention. A surface shape error measuring apparatus 1 includes a light source 2, a projection lens 3, a projection grating mask (liquid crystal panel, etc.) 4, a video camera 5, a liquid crystal panel control and shape error data analysis computer 6, and a measurement target. 7.

  The light from the light source is spread by the lens and illuminates the projection grating mask (here, the liquid crystal panel). In the liquid crystal panel, a projection grid (hereinafter referred to as a shape correction type projection grid) calculated in advance from the design value of the shape to be measured and the arrangement of the optical system is written by a measurement control computer.

The shape correction type projection grating is enlarged by a lens system, is projected onto the target surface, and generates a deformed grating (hereinafter referred to as an error deformed grating) slightly distorted by a shape error.
The error deformation grid is read by a video camera, and the position of the error deformation grid and the order of the grid are determined by a computer, and the shape error of the object is obtained.

FIG. 2A shows an example of a conventional projection grating mask. And consist linear grating of equally spaced D _0, the grid was eight A1 through A8. On the other hand, FIG. 2B shows an example of a shape correction type projection grating mask used in the present invention. The shape correction type grating generated from this mask is a projection grating for measuring an error of a shape having a step having a height of h, a width of w, and a length of l.

The grids C4 and C5 in FIG. 2B are at positions where ΔD ₀ is shifted by an amount from the grid positions of A4 and A5, respectively, and the step shape is corrected. By projecting this onto the surface of the step, if the step to be inspected is manufactured according to the design value and there is no error, the resulting deformed lattice image becomes a straight line with equal intervals.

  FIG. 3A shows a step having a height of h, a width of w and a length of 1 from the direction of the incident angle θ of a conventional linearly equidistant lattice as shown in FIG. This shows how the image is projected onto the target. Here, the deformed lattice image is observed from the front (above FIG. 3A) by the video lamella.

  As shown in FIG. 3B, the obtained deformed lattice image is largely separated from the lattices (B4 and B5) of the corresponding order in the stepped portions (D4 and D5). For this reason, in general, when the shape of the target has a step or a groove, or when a large number of projection lattices are required due to severe undulations, the lattice order of the obtained deformed lattice image cannot be distinguished. Measurement of the shape becomes difficult.

  On the other hand, FIG. 4A projects a shape-corrected projection grating as shown in FIG. 2B onto an object having a step having a height of h, a width of w, and a length of l. Shows the case. Here, the deformed grating is observed from the front by a video camera. As shown in FIG. 4B, the obtained deformed lattice image has a stepped portion of the deformed lattice (D4 and D5) and a stepped portion of the deformed lattice (B4 and B5) if there is no shape error in the stepped portion. Match exactly.

  In actual error measurement, there is a shape error in the step portion, but the shift is only the error, and is sufficiently smaller than the shift amount d in FIG. Therefore, even if the shape of the target generally has a step or a groove, or a large number of projection grids are required due to severe undulations, it is easy to determine the order of the grid and it is difficult to measure the shape. No.

Here, the error amount measured using the equation is quantitatively obtained. First, a projection grating generated by a straight line group mask with an equal interval D ₀ as shown in FIG. 2A is long from height of h and width w from the direction of the incident angle θ as shown in FIG. Consider a case where a step shape is measured by a conventional grid projection method in which projection is performed on an object having a height difference of l.

The deformed lattice image at this time is as shown in FIG. 3B, and a positional deviation of d occurs between a portion with a step and a portion without a step. By measuring this d, the height h of the step is obtained by the following equation.
h = d / {(D _p / D ₀ ) ² −1} ^1/2 . . . . (1)
Here, Dp is the interval between the deformed lattice images projected on a plane parallel to the stepless portion,
D _p = D ₀ / cos θ. . . . (2)
There is a relationship.

  Next, consider a case where the shape correction type projection grating (FIG. 2B) according to the present invention is projected onto a step target having a height h, a width w, a length l, and a shape error Δh.

In other words, in this case, according to the calculation, the shape correction type projection grating (FIG. 2B) is a projection grating (C4 and C5 in FIG. 4A) projected onto the step difference. 4 (a) A4 and A5), ΔD ₀ = h / {(D _p / D ₀ ) ² +1} ^1/2 . . . . (3)
Must be separated by a distance.

The direction of this shift is opposite to that shown in FIG. 3B, which is a modified lattice image obtained by the conventional method. In this way, when the object has no error with respect to the design value, the obtained deformed lattice image becomes a parallel straight line group, and when there is an error, the obtained deformed lattice image is shifted by the error. become. As a result, the presence / absence of an error becomes obvious at a glance, and it is possible to easily determine whether parts are good or bad.
Further, the error amount can be easily calculated after using the equation (1) as it is.

That is, if the amount of deviation observed in the shape-corrected deformed lattice image is Δd, the height error Δh of the step is Δh = Δd / {(D _p / D ₀ ) ² −1} ^1/2 . . . . (4)
It is obtained.

  The most important advantage of the present invention is that the normal error amount Δh is considered to be clearly smaller than h, and therefore the order can be easily determined even if there is a discontinuity in the deformed grid. That is, if there is a discontinuity in the deformed grid, it can be determined that the order matches the order of the nearest grid. As a result, the shape error can be accurately obtained without error. This is not possible with the conventional normal grid projection method.

  Further, in the conventional grating projection method, the deformed grating projected onto the steeply shaped shape portion has a wide line width and the intensity of the grating image is weak, and the position of the deformed grating cannot be read accurately. In the present invention, since only the shape error is detected as a deformed lattice image, the line width of the deformed lattice image is not widened, and therefore the strength of the lattice image is not weakened, and the position of the deformed lattice image can be read accurately. . This is also a great advantage of the present invention.

  The present invention relates to a method and apparatus for measuring and inspecting a shape error with respect to a design value of a measurement target, but the shape can be easily obtained. That is, the shape is obtained by adding the shape error measured by the present invention to the design value.

  The best mode of the present invention has been described based on the embodiments. However, the present invention is not limited to such embodiments, and various implementations can be made within the scope of the technical matters described in the claims. It goes without saying that there are examples.

  According to the present invention having the above configuration, an error in the surface shape can be easily and accurately measured by projecting a lattice created according to the design value of the surface shape of the inspection target onto the inspection target. Therefore, the present invention is extremely useful when applied to the field of shape inspection of parts made by a mold, for example. That is, the design value of the part shape to be processed by the mold is calculated from the design value of the mold, and the projection grid created based on the calculated value is projected onto the part actually manufactured by the projector. The shape error can be measured and inspected easily and accurately from the distortion of the parallel straight grid image.

It is a figure which shows the outline | summary of the measuring device of the surface shape error based on this invention. It is a figure for comparing the conventional normal projection grating | lattice (a) and the shape correction type | mold projection grating | lattice (b) based on this invention. It is a figure which shows the conventional optical system (a) of a normal grating | lattice projection, and a deformation | transformation grating | lattice image (b). It is a figure which shows the optical system (a) of a shape correction type | mold grating | lattice projection based on this invention, and an error deformation | transformation grating | lattice image (b).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Surface shape error measuring device 2 Light source 3 Projection lens 4 Projection grating mask (liquid crystal panel)
5 Video camera 6 Projection grating mask (liquid crystal panel) control and shape error data analysis computer 7 Measurement object

Claims (4)

  When the surface shape of the measurement target has no error compared to the design value, the projection grid created by calculating in advance so that the deformed grid image projected on the surface of the measurement target becomes a group of parallel lines is used as the design value. Measuring a surface shape error of an actual measurement object manufactured according to the design value by analyzing a deformed grid image generated by projecting on a surface of the actual measurement object manufactured according to Shape error measurement method to do.   When the surface shape of the measurement target has no error compared to the design value, the projection grid created by calculating in advance so that the deformed grid image projected on the surface of the measurement target becomes a group of parallel lines is used as the design value. A shape characterized by inspecting a surface shape error of an actual measurement object having the error by monitoring a deformed grid image generated by projecting with a projector onto the surface of the actual measurement object manufactured according to Error inspection method.   When the surface shape of the measurement target has no error compared to the design value, a projection grid created and created in advance so that the deformed grid image projected on the measurement target surface becomes a group of parallel straight lines is displayed on the liquid crystal panel. By writing, using a video camera, a deformed grid image generated by projecting a projection grid written on the liquid crystal panel onto the surface of an actual measurement target manufactured according to the writing and design values, and analyzing with a computer, A shape error measuring apparatus for measuring a surface shape error of an actual measurement object manufactured according to an erroneous design value. When the surface shape of the measurement target has no error compared to the design value, a projection grid created and created in advance so that the deformed grid image projected on the measurement target surface becomes a group of parallel straight lines is displayed on the liquid crystal panel. Actually with the above error by monitoring the deformed lattice image generated by projecting the pattern written on the liquid crystal panel on the surface of the actual measurement object that has an error compared with the writing and design value A shape error inspection apparatus characterized by inspecting a surface shape error of a measurement object.

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