JPH063367B2 - Method and apparatus for determining shape of object by projection - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention optically projects a shape of an object, calculates a curved shape of an axis line (center line of the object) from the projected shape, and uses this to perform a pattern matching method. The present invention relates to a method and an apparatus for making a judgment.

[Prior Art] When inspecting a member having a complicated curved shape, for example, a curved shape of a bending rod such as an automobile stabilizer,
Conventionally, various inspection methods have been proposed. That one is first
This is a mechanical inspection method using an inspection jig as shown in FIG. To explain this inspection method, the inspection jig 10 is U
A block 102 having a V-shaped recess 101 is provided with a bending rod 1
It is configured to be mounted on a large number of pedestals 103 according to the design shape of the
The bending bar 1 to be inspected is put in the second recess 101, and the quality of the bent shape is determined by visually observing whether or not the bending bar 1 fits properly in the recess 101 of each block 102.

However, in the mechanical inspection method using such an inspection jig, firstly, it is necessary to prepare a different inspection jig for each different type of the bending rod 1, which increases the manufacturing cost of the inspection jig. Not only does it require a large space to store the inspection jig. Secondly, it is necessary to replace the inspection jig each time the type of the bending rod 1 is changed, and there is a problem that handling of the heavy inspection jig is labor intensive and complicated.

Inspection jigs have also been proposed to improve such problems. For example, FIG. 11 shows an inspection jig for the bending rod 1 disclosed in Japanese Patent Laid-Open No. 58-68601, and a ruler rod 111 bent into the same shape as the intended bending shape as shown in the drawing.
A large number of receiving members 113 having U-shaped recesses 112 are attached to the support bar 1 on the pedestal 114.
The bending bar 1 to be inspected is attached to the indentation 112, and the bending bar 1 to be inspected is superposed on the ruler bar 111 while being fitted in the recess 112, and the bending shape of the bending bar 1 is visually inspected. Therefore, with the inspection jig shown in FIG. 11, the inspection jig can be made lighter and more compact, and the manufacturing of the inspection jig can be simplified. However, even when this inspection jig is used, it does not fundamentally solve the first and second problems.

Next, another method of inspecting the curved shape is to judge by electrically processing the video signal using an optical system. There are generally two methods for this.

(1) Pattern matching method This is to represent the reference axis line shape as a three-dimensional binary pattern and prepare a pattern in which this pattern is enlarged by the amount including the allowable range and made thicker after the pass / fail judgment. This is a method for judging the quality of the shape by checking whether or not all points on the axis line are included in this thickened pattern.

(2) Deviation calculation method This is to express the reference axis shape by an array of coordinates of each point on the axis, calculate the deviation from the reference axis for each point on the axis to be inspected, and judge whether the deviation is good or bad. This is a method of judging the quality of the shape based on whether or not it is within the above allowable range.

Of these two methods, the pattern matching method (1) generally requires a short time for the quality judgment, but
There is a problem that an enormous amount of memory is required for expressing the dimensional binary pattern. On the other hand, in the deviation calculation method of (2), the memory capacity required for expressing the reference axis line shape is small, but there is a problem that it takes a huge amount of time to calculate the deviation of the measured axis line coordinates from the reference axis line.

[Problems to be Solved by the Invention] In the inspection of the curved shape of the object as described above, it goes without saying that the inspection should be able to be performed accurately in a short time in order to ensure productivity. Therefore, the mechanical inspection method using the inspection jig as described above is not preferable also from this viewpoint. On the other hand, the optical inspection method is far more advantageous than the mechanical inspection method in this respect. Also, the test results are quantitative,
Moreover, there is an advantage that the inspection result can be fed back to the processing conditions of the bending machine. However,
The optical inspection method also includes the above problems.
In particular, in carrying out this optical inspection method, it is difficult to simultaneously achieve a reduction in calculation time and a reduction in memory capacity.

Therefore, the inventors of the present invention have adopted the pattern matching method, which is advantageous for shortening the calculation time, among the above optical inspection methods, and have made efforts to reduce the memory capacity. By doing so, we have seen its success.

The present invention basically relates to a pattern matching method, and an object of the present invention is to obtain a shape determining method and apparatus capable of inspecting a bent shape of an object accurately in a short time and using a small-capacity memory.

[Means for Solving the Problem] A method of determining the shape of an object by projection according to the present invention uses a reference when determining the axis line shape of an object and a reference axis line shape by a pattern matching method of a shape projected in a plurality of directions. The axis line shape is enlarged and thickened by the amount including the allowable range based on the projection pattern in each direction as described above, and the reference axis line shape is from the macro first layer with low resolution. High resolution micro nth
It has n layers up to the layer and has the i-th layer (i =
The shape patterns of 2, 3, ..., N) are designed to be extracted only for the block including the reference axis line shape among the shape patterns of the (i-1) th layer, and the axis line shape of the object is used as a reference. It is judged as acceptable only when it is within all the reference axis shapes from the first hierarchical layer to the nth hierarchical layer of the axial shape, and it is judged as defective when even one of them is out of alignment.

Further, a shape determining apparatus for performing such a shape determining method is a silhouette for obtaining projection patterns in a plurality of directions with respect to an axial shape of an object and a reference axial shape that is a comparison target of the axial shape by optical projection. An image pickup device, and an axis position detecting means for detecting an axis position from each projection pattern for expressing the projection pattern picked up by the image pickup device in each direction as a three-dimensional binary pattern,
Regarding the reference axis shape, in order to represent the projection patterns in a plurality of directions obtained by the silhouette image capturing device by a plurality of projection patterns in each direction, the resolution is high from the macro first shape pattern having a low resolution for each projection pattern. An n-stage hierarchical structure is formed up to a micron-th hierarchical shape pattern, and the i-th hierarchical shape pattern (i = 2, 3, ..., N) is a reference axis line of the (i-1) th hierarchical shape pattern. A plurality of shape master tables configured to be extracted only for blocks that include shapes, and a shape master table calculation that expands each projection pattern of the reference axis shape by the amount that includes the allowable range and makes it thicker and registers it in the shape master table. And a means.

[Operation] In the present invention, the curved shape of the center line of the object, that is, the curved line of the axis line is compared by the pattern matching method to judge the quality. In this case, the reference reference axis line shape is expressed as a three-dimensional binary pattern, and is thickened by the allowable range. In such a pattern matching method, the present invention further provides an n-stage hierarchical structure from the macro first hierarchical layer having a low resolution to the micro nth hierarchical layer having a high resolution for each projection pattern whose reference axis shape is in a plurality of directions. And the i-th layer (i = 2,
Since the shape patterns of 3, ..., N) are registered in advance as a configuration for extracting only the block including the reference axis shape among the shape patterns of the (i-1) th layer, it is determined that the shape pattern is the axis shape of the target object. In this case, the axis shape may be compared with the reference axis shape registered as described above,
It is possible to determine the pass only when the reference axis shape is included in all the reference axis shapes from the first layer to the n-th layer, and it is possible to determine the defect when even one of them is out of the reference axis shape. Therefore, the curved shape can be inspected accurately in a short time, and the memory capacity when the determination method is implemented as a device is small.

[Example] Hereinafter, the shape determination method according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is an external view of a shape measuring apparatus for obtaining a projection pattern of an axial shape and a reference axial shape of an object in the present invention. FIG. 2 is an internal configuration diagram mainly showing the optical system of this measuring apparatus.

In the present invention, first, the axial shape and the reference axial shape of the object are measured by optical projection. For this purpose, the reference axis line shape serving as a reference is set as a master piece as the object 1, and the axis line shape of the inspection target is set as a test piece as the object 1 in the shape measuring apparatus as shown in the figure, and the measurement is performed.

First, a master piece or a test piece is supported on a rotary table 2 of a rotary scanning device via a plurality of arms 3. A support tool 32 having a U-shaped recess 31 is provided at the tip of each arm 3, and a plurality of positions of the object 1 are fitted into the recesses 31 of these support tools 32 to support the target object 1.
The object 1 supported in this manner is rotated within the image pickup space 41 of the silhouette image pickup device 4 by rotating the turntable 2 at a predetermined angle by one pitch by an appropriate rotating means (not shown). To do.

As shown in FIG. 2, the silhouette image pickup device 4 includes two parallel light sources 5 and 6 and two contact image sensors 7 and 8.
And a reflecting mirror 9. The light beam 10 emitted from the parallel light source 5 is refracted by 90 degrees by the reflecting mirror 9, converted into a light beam parallel to the rotation axis 21 of the rotating table 2 and projected onto the object 1 in the imaging space 41, and the rotating table 2 A silhouette image of the object 1 is formed on the contact-type image sensor 7 provided in parallel with.
On the other hand, from the parallel light source 6, a light beam 1 whose optical axis is parallel to the upper surface of the turntable 2 and is orthogonal to the light beam 10 parallel to the rotation axis 21.
1 is emitted and this light flux 11 is projected onto the object 1 in the imaging space 41, and a silhouette image of the object 1 is formed on the contact image sensor 8 provided in parallel with the rotation axis 21.

Here, the parallel light sources 5 and 6 are used as the light sources because the light rays emitted from the parallel light sources 5 and 6 are parallel and the spatial coherence is high, so that they are generated in the silhouette image regardless of the shape of the object 1. The amount of blur is reduced, the measurement resolution can be increased, and since it is neither divergent light nor convergent light,
This is because it is not affected by fluctuations in the distance from the object 1.

Further, the contact type image sensors 7 and 8 have a size of 100 μm × 100, which has been widely used in small facsimiles in recent years.
A line scan type linear image sensor is used in which 2048 light receiving elements having a size of μm are linearly arranged at a pitch of 125 μm, and a voltage proportional to the amount of light received by each element is serially output. By using one or a plurality of such image sensors as needed, the image forming system of the optical system is not required, and the size of the apparatus can be reduced.

With the silhouette image capturing device 4 described above, projection patterns in a plurality of directions can be obtained for the axial line shape and the reference axial line shape of the object 1. Next, the projected patterns in these directions are converted into a three-dimensional binary pattern. The means for expressing will be described. FIG. 3 shows an example of such means, and is a block diagram of a shape determination device for determining a curved shape of an object from a silhouette signal of a projection pattern.

In the figure, 12 is an axis position detecting circuit for processing the signals of a plurality of contact image sensors 7 and 8 in the silhouette image pickup device 4 to detect the axis position of the object 1, and 13 is an axis position detecting circuit 12. A coordinate conversion circuit for converting the output axis position expressed in the cylindrical coordinate system into the orthogonal coordinate system, 14
Is a reference axis line shape measured for the master piece, decomposed into a plurality of projection patterns, expanded by the amount including the error in the quality judgment, that is, the allowable range, and made into a thick line, and further expanded into hierarchical structure data to form the shape master table described later. The shape master table arithmetic circuit, which is registered in step 1, is provided corresponding to a plurality of projection patterns of the reference axis shape and has a low resolution from a macro first pattern shape pattern to a high resolution micro nth level pattern pattern. The shape master table that stores the reference axis line shape expressed in the hierarchical structure of n stages up to, and 16 shows the axis line shape data measured for the test piece in advance in the shape master table 15
A pass / fail judgment circuit that determines whether or not the reference axis line shape registered in 1 is within an allowable range, and 17 is an output circuit that outputs a pass / fail judgment result.

The operation of the shape determination device configured as above will be described below. The axis position detection circuit 12 and the coordinate conversion circuit 13 are commonly used both when registering the master piece shape and when determining the test piece shape. That is, the master piece or the test piece is set on the arm 3 of the shape measuring device shown in FIG. 1 at the time of registration of each shape and at the time of quality judgment, and the silhouette imaging device 4 is set every time the rotary table 2 rotates one pitch. A silhouette image is observed, and the contact image sensors 7 and 8 output silhouette signals in the r direction (radial direction) and the z direction (height direction), respectively.

The axis position detecting circuit 12 binarizes the silhouette signals output from the contact image sensors 7 and 8 as described above, as shown in FIG. 4, and outputs the central position 42 of the silhouette portion 41 where the output voltage 40 is zero. To calculate the center position 42
Are output as axis line positions r (θ) and z (θ) expressed in a cylindrical coordinate system.

The coordinate conversion circuit 13 converts the axial line positions r (θ) and z (θ) of the cylindrical coordinate system obtained from the axial line position detection circuit 12 into a rectangular coordinate system and outputs it as (x _i , y _i , z _i ).

On the other hand, in the shape determination device, after the axial line shape (x _i , y _i , z _i ) of the object 1 represented in the orthogonal coordinate system as described above is obtained, the master piece shape is registered and the test piece shape is registered. The method of processing differs depending on the determination.

First, a method of creating the shape master table 15 for registering the master piece shape will be described.

The shape master table arithmetic circuit 14 calculates the axis shape (x _i , y _i , z _i ) obtained by measuring the master piece.
Based on the above, for example, as shown in FIGS. 5A to 5D, it is decomposed into a plurality of projection patterns. Here, FIG. 10A shows an axial projection pattern 50a on the XZ plane.
(B) is an axial projection pattern 50b for the XY plane, (c) is an axial projection pattern 50c for the YZ plane seen from the left side, and (d) is the right side. 50d axial projection pattern on the YZ plane viewed from above
Is shown.

In creating these projection patterns, for a portion such as the support 32 of the arm 3 that supports the master piece, where the shape of the master piece cannot be directly measured, the axial shape data continuously obtained by interpolation from the shape data in the vicinity thereof is appropriately used. Further, prior to registration in the shape master table 15, for convenience of shape determination later, the projection pattern is thickened in advance by an allowable range in pass / fail determination.

Each of the plurality of projection patterns created as described above has an n-layer hierarchical structure from a macro shape pattern having a low resolution to a micro shape pattern having a high resolution, and further has an i-th layer (i = 2, 3). , ..., N) are registered in the shape master table 15 configured to extract and include only the blocks including the reference axis shape among the shape patterns of the (i-1) th layer.

For example, the axial projection pattern 50b on the XY plane shown in FIG. 5B is represented by a hierarchical data structure from macro to micro as shown in FIGS. That is, FIG. 6 shows the first hierarchical table 61 obtained by dividing the axial projection pattern shown in FIG. 5 (b) into, for example, (12 × 6) blocks, and 0 is assigned to the block in which the axial projection pattern does not exist. In addition, the memory addresses A _{1 to} A ₁₆ in the shape master table 15 in which the second hierarchical table corresponding to each block is stored are registered in the block where the axis projection pattern exists. FIG. 7 shows A in FIG.
Corresponding to the block of the first layer shown by ₅ , the block A ₅ is further divided into (16 × 16) blocks and one of the second layer tables 62 expressing the axial projection pattern is shown. These second hierarchical tables 62 are respectively memory addresses A in the shape master table 15.
Stored below ₁₆ . Also in the second layer table 62, 0 is registered in a block having no axis projection pattern, and memory addresses B _{1 to} B _{25 of} the third layer table corresponding to the block are registered in the existing block. There is. Finally, FIG. 8 shows the lowermost table 63 corresponding to the block indicated by B ₁₆ in the second layer. In the table 63 of the lowermost layer, a part of the axis projection pattern is registered as, for example, (16 × 16) 0/1 information. The example of FIG. 8 shows an example in which the allowable error in pass / fail judgment is ± 2 image system and the axial line projection pattern is registered as the two-image system thick line 64.

Next, referring to the shape master table 15 registered in this way, a method for the quality determination circuit 16 to determine the quality of the test piece shape will be described based on the flow chart of FIG.

The axis line position data obtained for each point on the test piece is first compared with the first hierarchical table 61 representing the most macro shape in the shape master table 15 (step 91), and whether or not it is included therein. Is determined (step 92). At this time, if it does not enter, it is determined that the corresponding portion on the test piece has a defective shape (step 98). If it is included in the first layer table 61, then the second layer table 62 corresponding to the block is referred to (step 93), and the same quality judgment is made (step 94). And finally, the second
If it is included in the hierarchy table 62, the third hierarchy table 63 corresponding to the block is referred to (step 9
5), 0/1 of the data in the table corresponding to the measured axial position data is determined (step 96), and only in the case of 1, it is determined that the axial position data is within the predetermined shape (step 96). 97).

The above judgment is performed for all points on the test piece, and when the axis line position data is within the predetermined shape for all points, the test piece is judged as a good product, and
If even one point is out, it is determined as a defective product, and the quality determination result and the defective portion are output and displayed via the output circuit 7.

Although the master shape is registered based on the measurement data in the above embodiment, the master shape may not necessarily be measured, and may be registered based on the CAD data, for example. Further, when the projection pattern of the shape master is created, the projection onto the plane composed of the coordinate axes of the orthogonal coordinate system is used, but the gist of the present invention is not necessarily limited to this, and the shape master is uniquely defined. For example, projection patterns on the (R, θ) plane and the (θ, Z) plane in the cylindrical coordinate system may be used as long as they can be expressed.

[Effects of the Invention] As described above, according to the present invention, the axial line shapes of objects are compared by a pattern matching method to determine their quality, and the reference axial line shape serving as a reference is expressed as a three-dimensional binary pattern. The projection pattern in each of a plurality of directions is thickened to the allowable range, and the projection patterns in a plurality of directions are distributed from the macro first layer with low resolution to the micro nth layer with high resolution.
And a i-th hierarchy (i = 2, 3, ...,
The shape pattern n) is registered in advance as a configuration for extracting only the block including the reference axis shape among the shape patterns of the (i-1) th layer, so that the determination as the axis shape of the object can be performed quickly and accurately. As well as
The effect is that the memory capacity is small.

[Brief description of drawings]

FIG. 1 is an external view of a shape measuring apparatus used in the shape determining direction according to the present invention, FIG. 2 is an internal configuration diagram of the shape measuring apparatus, and FIG. 3 is a block diagram showing an embodiment of the shape determining apparatus according to the present invention. FIGS. 4 and 5 are output waveform diagrams of the shape determination device, FIGS. 5 (a) to 5 (d) are explanatory views showing axial projection patterns for respective planes, and FIG. 6 shows a first hierarchical table of the shape master table. Explanatory drawing, FIG. 7 is an explanatory view showing a second hierarchical table of the shape master table, FIG. 8 is an explanatory view showing a third hierarchical table of the shape master table, and FIG. 9 is a shape judging device shown in FIG. FIG. 10 and FIG. 11 are flow charts showing the operation of the above, respectively, and are configuration diagrams of the inspection jig used in the conventional mechanical inspection method. DESCRIPTION OF SYMBOLS 1 ... Object 4 ... Silhouette image imaging device 12 ... Axis position detection circuit 13 ... Coordinate conversion circuit 14 ... Shape master table arithmetic circuit 15 ... Shape master table 16 ... Good / bad judgment circuit 17 ... Output circuit 50a-50d ... Axis projection pattern 61 ... first tier table 62 ... second tier table 63 ... third tier table

Claims (2)

[Claims] 1. A curved shape by comparing the axial shape of an object with a reference axial shape which is enlarged and thickened by an amount including an allowable range in each direction based on a projection pattern obtained by projecting in a plurality of directions. The reference axis shape is divided into n levels of hierarchy from a macroscopic first hierarchical shape pattern with low resolution to a microscopic nth hierarchical shape pattern with high resolution, and The shape pattern of the hierarchy (i = 2, 3, ..., N) is the (i-1) th
Only the block including the reference axis line shape is extracted from the shape patterns of the layers, and the axis line shape of the object is selected from the first layer to the nth layer of the reference axis line shape.
A method for determining the shape of an object by projection, which comprises determining the quality of a curved shape by sequentially comparing layers. 2. A silhouette image capturing device having an axial shape of an object and a reference axial line shape serving as a reference; and a plurality of directions of projection patterns obtained by the silhouette image capturing device with respect to the axial shape and the reference axial line shape of the object, respectively. Axis position detecting means for detecting the axis position of the macroscopic first-layer shape pattern having a low resolution, which is provided in correspondence with the projection patterns in a plurality of directions obtained by the silhouette image capturing device with respect to the reference axis shape. To a micron shape pattern with high resolution from the nth hierarchical structure, and the i-th hierarchical structure (i =
A plurality of shape master tables configured so as to have only the blocks including the reference axis shape among the shape patterns of the (i-1) th layer among the shape patterns 2, 3, ..., N); A shape master table calculating means for enlarging each projection pattern of the reference axis shape by an amount including an allowable range and registering it in the thickened master table, the object shape determining apparatus by projection.