JPH0467907B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a surface defect detection method for optically detecting the presence and extent of pinholes, cracks, etc. on the surface of a detected object such as a water faucet.

(Prior Art) In the manufacturing process of faucets and the like, pinhole defects, cracks, etc. may occur, and it is necessary to remove these defective products from the manufacturing line.

Since the surfaces of faucets and the like are curved, it is difficult to automatically inspect them compared to flat objects, and inspections have been performed visually by humans.

(Problems to be Solved by the Invention) In recent years, with advances in image processing technology, automatic defect detection using a television camera has been put into practical use.
Object image receiving means using a camera can be roughly divided into transmitted light reception and reflected light reception, but in the case of faucet defect detection, since the faucet itself is non-transparent, the latter detection method based on reflected light reception is adopted. are doing. If the object to be detected is a flat object such as a plate or a cylindrical pipe, the reflected light waveform is flat, so processing is relatively easy. However, if the object is curved like a faucet, the reflected light waveform is flat. The waveform also fluctuates with unevenness corresponding to the curved surface shape, which requires some ingenuity in the detection process, resulting in a problem that defect detection becomes complicated.

In addition, when inspecting faucets and the like for defects, if only the presence or absence of defects is determined, small defects that should be considered as good products are also determined to be defective, resulting in a high rejection rate and poor yield.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a surface defect detection method that can detect defects simply and accurately.

(Means for Solving the Problems) In order to solve the above-mentioned problems and achieve the above objects, the present invention provides means for transmitting light from the surface of an object to be detected to a light detection means having a plurality of pixels. It is a surface defect detection method in which defects such as pinholes on the surface of the object to be detected are detected based on the received light output corresponding to the amount of incident light of each pixel by converging the incident light and sequentially scanning the plurality of pixels at a predetermined period. The output of each pixel located at a predetermined pixel interval among the total number of pixels is sequentially compared, and the output of the pixel located on the front side in the scanning direction is at a predetermined level or higher than the output of the pixel located on the rear side in the scanning direction. defect start position determining means for determining the pixel located on the front side as a pixel corresponding to the defect start position when the output level is low, and the output level of the pixel located on the front side with respect to the scanning direction continues the scanning and the output level of the pixel located on the front side with respect to the scanning direction is a predetermined level. a defect end position determining means that determines the pixel as a pixel corresponding to the defect end position when the pixel has recovered to the above, and a pixel interval between the determining pixel of the defect starting position determining means and the determining pixel of the defect end position determining means. The present invention is characterized in that a defect width calculation means for calculating a defect width is provided, and when the defect width is equal to or larger than a predetermined value, it is determined to be a defect.

(Example) Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a half-sectional view showing a water faucet as an example of a detected object, and Fig. 3a is a normal water faucet. Figure 3b is a waveform diagram of the received light level obtained from the faucet surface. Figure 3c is an enlarged view of the defective part in Figure 3b. FIG. Reference numeral 1 denotes a one-dimensional camera (CCD sensor) that is equipped with a plurality of pixels and serves as a light detection means that outputs an analog light reception signal corresponding to the amount of light incident on each pixel. To explain the one-dimensional camera (CCD sensor) 1 in detail, it has a structure in which, for example, 2048 pixels are arranged horizontally in a straight line, and it captures light from the surface of a faucet with a total length of about 80 mm, which will be described later, through a lens, etc. Since it converges and enters the pixels,
It has a resolution corresponding to each pixel interval, ie, a resolution of about 40 microns. Further, the 2048 pixels are sequentially scanned at predetermined intervals, and the light reception output of each pixel is extracted in accordance with the scanning interval, and each pixel is initialized in synchronization with the scanning interval. The light reception signal obtained by the one-dimensional camera (CCD sensor) 1 is
Each pixel is sequentially converted into a multilevel (256 gradation) digital value via an A/D (analog/digital) converter 2. This digital value data is supplied to a shift register 3 that shifts data for N (integer) pixels and a subtraction circuit 4. The subtraction circuit 4 uses the current pixel data D _A and the past data N pixels before, which is obtained via the shift register 3.
D _B , calculates (D _B - D _A ) = △D, and then the sign discrimination circuit 5 uses the comparison circuit 6 only when △D is positive.
Output to. The comparison circuit 6 compares the judgment value of the judgment value circuit 7 with the value of △D, and when △D is greater than the judgment value, that is, the defect has started at the position corresponding to point A in Fig. 3 c. , the data of pixel counter 8 is N
The number of pixels is subtracted, that is, the pixel position X _S is stored in the memory 9. The pixel counter 8 is supplied with a signal synchronized with the scanning period from an oscillator (not shown). Also, set the D _B value at this time as a threshold value as D _S ,
The comparison circuit 10 sequentially compares the D _S value and the current pixel data D _A , and as shown in FIG. 3c, D _S ≦
The pixel position X _E that corresponds to D _A is determined to be the end of the defect. The subtraction circuit 20 calculates the difference △ between the X _E value and the defect start pixel position X _S value stored in the memory 9.
Calculate X as the defect width. The value of △X is determined by the width comparison circuit 1 for determining small width defects as good products.
1 and the value of ΔX is greater than or equal to a preset threshold, that is, only defects with large widths are output. 21 is an AND circuit.

FIG. 4 is a block diagram showing another embodiment of the present invention. If the level at position B is the same as or higher than the level at position A in Fig. 3c, the defect can be reliably detected using the embodiment in Fig. If this occurs, it becomes difficult to determine the end of the defect. Since the direction of the unevenness of a faucet is determined depending on the part, in the part of the surface level where the level of position B is lower than the level of position A, the pixel address direction is scanned in the opposite direction, and
is characterized in that it is treated as the beginning of a defect. To specifically explain the embodiment in FIG _. 4 _, as shown in _FIG .
p ₁ , p ₂ , p ₃ are set, and the data A/D converted by the A/D converter 2 is used in the forward scanning M process.
After storing it in the memory 12 so as to process it with a one-scan delay in order to match the timing with the reverse scan P, only the areas m ₁ , m ₂ , and m ₃ are processed based on the forward scan area signal M of the forward address counter 19. 13. The processing block 13 has functions equivalent to those within the dotted line in FIG. In the reverse scan process,
After the data A/D converted by the A/D converter 2 is stored in the memory 14, only the areas p ₁ , p ₂ , p ₃ are processed in the processing block 16 based on the reverse scanning area signal P of the reverse address counter 15. . This processing block 1
6 has a function equivalent to the processing function within the dotted line in FIG. The defect signals from each processing block 13 and 16 are outputted via an OR circuit 17.

Note that in the above embodiment, one camera (CCD sensor) is used to perform forward and reverse scanning processing, but two cameras are used and the mounting positions of the cameras are reversed so that each camera is The configuration may be such that the waveform of light received from the sensor is a forward scan or a reverse scan.

Furthermore, although the above-described embodiment has been described using a one-dimensional camera, the present invention can also be applied to a case where similar processing is performed using a signal of one horizontal scanning line of a two-dimensional camera.

In the above-described embodiments, the case where the defect level is smaller than the normal level has been described, but the same concept can be applied to the case where the defect level is larger than the normal level on the surface.

(Effects of the Invention) As described above, according to the present invention, it is possible to easily and accurately detect defects on the surface of a faucet or the like.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing one embodiment of the present invention, Figure 2 is a half-sectional view of a water faucet, and Figure 3 is a one-dimensional diagram.
FIG. 4 is a block diagram showing another embodiment of the present invention, and FIG. 5 is a diagram showing a detection area corresponding to the scanning direction. 1...One-dimensional CCD camera, 2...A/D converter, 3...Shift register, 4...Subtraction circuit, 5
... Sign discrimination circuit, 6, 10, 11 ... Comparison circuit, 7 ... Judgment value circuit, 8 ... Pixel counter, 9
...Memory, 12, 14...Scanning memory, 13,
16...processing block, 15...reverse address counter, 17...OR circuit.

Claims (1)

[Claims] 1. Light from the surface of an object to be detected is converged and incident on a light detection means having a plurality of pixels, and the plurality of pixels are scanned at predetermined intervals to obtain a light reception output corresponding to the amount of incident light at each pixel. In a surface defect detection method that detects defects on the surface of a detected object based on the above, the output of each pixel located at a predetermined pixel interval among the total number of pixels is sequentially compared, and the pixel output is located on the front side in the scanning direction. defect start position determining means for determining the pixel located on the front side as a pixel corresponding to a defect start position when the pixel output is lower than the pixel output located on the rear side by a predetermined level or more; defect end position determining means for determining the pixel as a pixel corresponding to the defect end position when the output level of the pixel located in front of the pixel recovers to a predetermined level or higher; and a determination pixel of the defect start position determining means. Defect width calculation means for calculating a defect width according to a pixel interval with a determination pixel of the defect end position determination means, and when the defect width is equal to or greater than a predetermined value, it is determined as a defect. method. 2. The scanning direction of the light detection means is set alternately to the forward direction and the reverse direction, and each region is scanned in an area where the amount of light incident from the surface of the object to be detected increases or does not change with respect to the scanning of the light detection means. 2. The surface defect detection method according to claim 1, wherein the defect detection method is performed only within each area by setting the area according to the direction.