Shape measurement method

Abstract

This invention provides a shape measurement method that can quickly and accurately measure the shapes of multiple workpieces under inspection. [Solution] Multiple identical workpieces W are arranged at intervals on a plane within a predetermined area, and these workpieces W are simultaneously imaged by an area-type laser scanner 2 capable of scanning within the predetermined area. The images Wi of the multiple imaged workpieces W are separated individually, and each separated workpiece image Wi is compared with a CAD image of a workpiece W with a normal shape. The shape defect of the corresponding workpiece W is measured based on the difference between the workpiece image Wi and the CAD image.

Description

Technical Field

[0001] The present invention relates to a shape measurement method, and more particularly to a method for quickly measuring the precise shapes of a plurality of workpieces by optical measurement and detecting shape defects thereof.

Background Art

[0002] Laser scanners that can obtain the precise shape of a workpiece to be inspected as point cloud data that can be directly processed in a computer are increasingly being used. In this case, for example, as shown in Patent Document 1, a laser scanner that scans a laser across the workpiece to be inspected is moved in a direction intersecting (usually orthogonal) to the scanning direction to obtain a point cloud data image of the entire outer shape of the workpiece to be inspected.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above conventional method of obtaining a data image by moving a laser scanner, when there are a plurality of workpieces to be inspected, the moving distance becomes long according to the number thereof, so there is a problem that it takes time for shape measurement and determination of shape defects based thereon.

[0005] Therefore, the present invention solves such problems and aims to provide a shape measurement method capable of quickly and accurately measuring the shapes of a plurality of workpieces to be inspected.

Means for Solving the Problems

[0006] To achieve the above objective, in this first invention, multiple identical workpieces (W) are arranged at intervals on a plane within a predetermined area, these workpieces (W) are simultaneously imaged by an area-type laser scanner (2) capable of scanning within the predetermined area, the images (Wi) of the multiple imaged workpieces (W) are separated individually, and each separated workpiece image (Wi) is compared with a CAD image of a workpiece (W) with a normal shape, and the shape defect of the corresponding workpiece (W) is measured from the difference between the workpiece image (Wi) and the CAD image.

[0007] According to this first invention, multiple workpieces are imaged simultaneously, the images of the multiple workpieces are separated individually, and shape defects are measured by comparing each separated workpiece image with a CAD image. Therefore, compared to conventional methods that involve moving a laser scanner, the shapes of multiple workpieces can be measured quickly and accurately.

[0008] In this second invention, the workpiece to be inspected (W) is inserted into a plurality of recesses (41) formed at predetermined intervals on the upper surface of the mounting plate (4), the recesses being shaped to conform to the outer circumference of the workpiece to be inspected (W).

[0009] According to this second invention, multiple workpieces to be tested can be easily arranged at predetermined intervals.

[0010] In this third invention, the spacing between the workpieces (W) is confirmed using a frame image (Fi) in which multiple frames are formed surrounding each of the multiple workpiece images (Wi) to be inspected.

[0011] According to this third invention, it is possible to quickly confirm whether the arrangement of the workpiece under inspection is correct using a frame image.

[0012] The symbols in parentheses above are for reference only, indicating the correspondence with the specific means described in the embodiments described later. [Effects of the Invention]

[0013] As described above, the shape measurement method of the present invention makes it possible to quickly and accurately measure the shapes of multiple workpieces to be inspected. [Brief explanation of the drawing]

[0014] [Figure 1] This is a perspective view of the tilting mechanism. [Figure 2] This is a perspective view of the mounting plate on which the test workpiece is placed. [Figure 3] This is an image of the workpiece being tested, placed on a mounting plate. [Figure 4] This image shows a frame image superimposed on an image of the workpiece being examined. [Figure 5] This is an image of the workpiece that has been cropped. [Figure 6] This is a magnified view of a portion of the image when the workpiece image and the CAD image are aligned. [Modes for carrying out the invention]

[0015] The embodiments described below are merely examples, and various design improvements made by those skilled in the art without departing from the spirit of the present invention are also included within the scope of the present invention.

[0016] Figure 1 shows the external appearance of an apparatus for carrying out the method of the present invention. In Figure 1, the tilting device comprises a motor-driven ring-shaped frame 1, the frame 1 is capable of swiveling around a rotation axis 11 within a predetermined angular range, and at the swiveling position around the rotation axis 11, it is also capable of swiveling around a rotation axis 12 perpendicular to the rotation axis 11 within a predetermined angular range.

[0017] A rectangular mounting plate 4, as shown in Figure 2, is fixed to the base frame 1. Multiple recesses 41 are formed on the surface of the mounting plate 4 at intervals. Each recess 41 is shaped to conform to the outer circumference of the workpiece W to be inspected. In this embodiment, each recess 41 is rectangular and is formed in 15 locations on the upper surface of the mounting plate 4 in 5 vertical rows and 3 horizontal rows. Thick-walled rectangular workpieces W of the same shape are inserted into each recess 41. By tilting the mounting plate three-dimensionally as appropriate, the orientation of multiple workpieces W placed on the mounting plate 4 can be changed simultaneously.

[0018] Above the table frame 1 (i.e., above the workpiece W to be inspected), an area-type laser scanner 2 is disposed. By scanning the area on the mounting plate 4 with a laser beam at once by the laser scanner 2, three-dimensional images (point cloud data) of all the workpieces W to be inspected placed on the mounting plate 4 can be obtained simultaneously. All the images of the workpieces W to be inspected obtained by the laser scanner 2 are sent to a computer 3 connected thereto, and defects in the shape of each workpiece W to be inspected are measured by the process described below.

[0019] FIG. 3 shows three-dimensional images (workpiece images to be inspected) Wi of all the workpieces W to be inspected on the mounting plate 4 obtained by the area-type laser scanner 2 described above. Note that FIG. 3 shows the case where the workpieces W to be inspected are inserted into all the recesses 41 of the mounting plate 4.

[0020] In this state, in the present embodiment, as shown in FIG. 4, a square grid-shaped frame image Fi is superimposed on all the workpiece images Wi to be inspected. Each square frame of the frame image Fi has a size that surrounds the recess 41 of the mounting plate 4, and the pitch of the square frames is the same as that of the recess W. Thereby, when the workpiece image Wi to be inspected interferes with the square frame of the frame image Fi, it is regarded that the workpiece W to be inspected is not properly inserted into the recess 41 of the mounting plate 4, and subsequent processing is not performed, and repositioning of the workpiece W to be inspected into the recess 41 is prompted.

[0021] After confirming that the workpiece image Wi to be inspected is arranged at an appropriate position using the frame image Fi, the workpiece image Wi to be inspected is cut out one by one softly from the plurality of workpiece images Wi to be inspected, and the cut-out workpiece image to be inspected is sequentially moved to a predetermined origin position for the following alignment as shown in FIG. 5. The workpiece image Wi to be inspected moved to the origin position is aligned with a CAD image of a workpiece to be inspected having a normal shape stored in advance. This alignment is performed by, for example, the ICP (Iterative Closest Point) method.

[0022] If, due to alignment, a difference occurs between the CAD image (line a) and the workpiece image (line b) as shown in Figure 6 (shaded area in Figure 6), then it is assumed that a shape defect such as chipping has occurred in the corresponding workpiece W at the area of ​​difference. [Explanation of Symbols]

[0023] 1...frame, 2...area-type laser scanner, 3...computer, 4...mounting plate, 41...recess, Fi...frame image, W...workpiece under inspection, Wi...workpiece under inspection image.

Claims

1. A shape measurement method comprising: arranging multiple identical workpieces of a certain shape at intervals on a plane within a predetermined area; simultaneously imaging these workpieces with an area-type laser scanner capable of scanning within the predetermined area; separating the images of the multiple captured workpieces individually; comparing each separated workpiece image with a CAD image of a workpiece with a normal shape; and measuring the shape defect of the workpiece based on the difference between the workpiece image and the CAD image.

2. The shape measurement method according to claim 1, wherein the workpiece to be inspected is inserted into each of a plurality of recesses formed at predetermined intervals on the upper surface of the mounting plate, the recesses being shaped to conform to the outer circumference of the workpiece to be inspected.

3. The shape measurement method according to claim 1 or 2, wherein the spacing between the workpieces is confirmed using a frame image in which multiple frames are formed surrounding each of the multiple workpiece images to be inspected.

Images