JPS6264935A - Apparatus for inspecting surface flaw - Google Patents

Abstract

PURPOSE:To make it possible to accurately detect the flaw of an entire surface without receiving the effect of noise, by comparing the surface brightnesses of an object on two wires close to each other and electronically masking noise wave forms generated at both terminal parts of an output signal. CONSTITUTION:A flaw inspecting camera 1 is constituted of the reflective mirror 3 having two reflective surfaces 5, 6 provided on the axis (l) of a lens 2 in a freely advancing and retrating manner and two linear image pickup elements 7, 8. Next, an output operation circuit 10 is constituted of a differential operation circuit 11, a digital converter circuit 12 and a masking circuit 13 consisting of n1-bit and n2-bit counters 14, 15. The reflected light from the surface of an object 20 is received by the lens 2 while the object 20 is rotated and the brightnesses of said object 20 on the radii on two wires extremely close to each other are caught as the output signals of the image pickup elements 7, 8 and a difference signal is obtained from said output signals by the differential operation circuit 11 to be digitized and both terminal parts thereof are masked by the masking circuit 13. By this method, the fine flaw on the object 20 can be detected with good accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a surface defect inspection device used for optically inspecting the presence or absence of surface defects on objects having complex shapes.

(Prior art) A surface defect inspection device in which a linear imaging device is arranged on the lens axis of a television camera has been used to inspect surface defects on plate glass, tI4 temporary, etc., but the brightness of the object surface is directly converted into an electrical signal, so when used to inspect objects such as insulators that have complex uneven surfaces and cannot be illuminated with uniform brightness, changes in surface brightness due to defects will be caused by uneven illumination. The problem was that it was hidden and correct inspection could not be performed. Therefore, the inventor has developed two direct 'faf'
He invented a surface defect inspection device in which the influence of uneven illumination was canceled by arranging IL image elements close to each other in parallel and calculating the difference between the output signals of both. I have just proposed this as a new issue.

However, since the linear image sensor itself has a width of about 101 mm, it cannot be placed close to it at a distance of less than 10 mm, and if the lens magnification is M, the width of
QXMTsuruIn addition to the problem of not being able to sufficiently improve inspection accuracy as it involves comparing the brightness on two lines that are far apart,
As shown in the figure, when using multiple cameras, if the distance between the camera and the object is kept constant in order to equalize the accuracy, a noise waveform will be generated at both ends of the field of view, so a light shielding plate is installed in front of the linear image sensor. When optical masking is performed, there remain problems such as signals at the edges tend to become unclear.

(Problems to be Solved by the Invention) The present invention solves these conventional problems and can accurately compare the brightness of two adjacent lines on the surface of an object. It was completed with the aim of creating a surface defect inspection device that prevents malfunctions by electronically masking the noise waveforms generated at both ends of the surface.

(Means for Solving the Problems) The present invention provides a reflector having two reflective surfaces mounted on the axis of a lens with a ridge line orthogonal to the axis in between, and a mirror that receives reflected light from each reflective surface. It consists of a defect inspection camera equipped with two linear image sensors, an output calculation circuit of the defect inspection camera, and a differential calculation circuit that obtains a difference signal from the outputs of the two linear image sensors; a digital conversion circuit that converts the digital signal into a digital signal, and a masking circuit that masks the end of the digital signal using a blanking signal narrower than the field of view of the camera obtained based on the clock signal for driving the linear image sensor. It is characterized by containing.

(Example) Next, the present invention will be explained in detail with reference to the illustrated example.
In Figures 1 and 2 (11 is a defect inspection camera;
(lO) is an output calculation circuit that processes the output signal of the defect inspection camera (11). The reflecting mirror (3) has two reflecting surfaces (5) at symmetrical positions across the ridgeline (4) perpendicular to the axis (
), (6), and on the inner surface of the defect inspection camera (1) are 2 that receive the reflected light from each reflective surface (5), (6).
Two linear image sensors (7) and (8) are attached.

The output calculation circuit (10) has two straight lines as shown in Figure 3.
A differential calculation circuit (11) that obtains a difference signal from the outputs of the 41A+i image elements (7) and (8), and a digital conversion circuit (11) that compares this analog signal with a reference value and converts it into a binarized digital signal. 12) and a masking circuit (13). The masking circuit (13) includes a nl bit counter (14) that counts the clock signal for driving the element up to a preset n bit, and a n2 bit counter (14) in the same middle part. n2 bit counter (15) that counts up to bits, and both of these counters (14), (1
5) is connected to be cleared by the element drive start signal, so the clock signal causes the linear imaging elements (7) and (8) to be cleared from the first bit to the last bit.
These counters (14), (15) start counting from 1 and n as the reading progresses bit by bit.
An output is generated at the 1st bit and the nth bit. Therefore, the outputs of these counters (14) and (15) are connected to the OR circuit (1
6) to the clock terminal (CK) of the flip-flop controller (17), a blanking signal from n1 bit to n bit as shown in FIG. 6(E) can be obtained.

Therefore n1sn! By appropriately setting the value of , a blanking signal canting both ends of the field of view of the camera can be obtained.If this is input to the AND circuit (18) together with the digital signal described above, both ends of the digital signal can be obtained. This results in a signal in which the masked signal is masked.

(Function) The device configured in this way is set against an object (20) such as a suspended insulator as shown in FIG. When the reflected light is received by the lens (2), the reflected light is distributed to the left and right with the ridge line of the reflecting mirror (3) installed on the axis line as the border, and is sent to the 12 linear image sensors (7) and (8). incident. In this way, the reflected light is distributed by the reflecting mirror (3), so the %? As shown in Figures 6(A) and (B), the brightness changes in the radial direction on I(21) and (22) are directly km J
This will be obtained as an analog output signal of the IS image elements (7) and (8). If there is no defect on the surface of the object (20), the output signals of the two linear image sensors (7) and (8) will have the same curve, but if there is a defect on the surface of the object (20), A moment occurs when only one linear imaging element beak 7) detects a surface defect, and one output signal includes the defect signal as shown in FIG. 6(A). Therefore, the differential arithmetic circuit (
11) to obtain the difference signal shown in FIG. 6(C), which is then digitized by the digital conversion circuit (12) as shown in FIG. 6(D).

At the end of this digital signal, the field of view of the camera is the object (
20), but if both ends are masked by the masking circuit (13) as described above, a digital signal containing only the defective signal shown in FIG. 6(F) can be obtained. This will be obtained. In this way, in the present invention, it is possible to detect changes in brightness on the two lines (21) and (22) that are very close to each other on the surface of the object (20), so even minute defects can be detected with high accuracy. I can do it. Additionally, it is possible to mask edge noise by changing the width of the blanking signal for each camera, so it is possible to inspect both wide and narrow areas of the field of view using the same type of camera, and masking can be done electronically. Since the masking is carried out in the same manner as in the case of optical masking, the edges do not become unclear as in the case of optical masking.

(Effects of the Invention) As is clear from the above description, the present invention is capable of comparing the brightness of two very close lines on the surface of an object, achieving high inspection accuracy, and Since the resulting difference signal is electronically masked bit by bit to remove edge noise, it is possible to accurately detect defects on the entire surface of the object without being affected by noise using the same type of camera. It is something that can be inspected. Therefore, the present invention can greatly contribute to the development of industry as a surface defect inspection device for articles having complex shapes such as insulators.

[Brief explanation of drawings]

FIG. 1 is a horizontal sectional view showing an embodiment of the present invention, FIG. 2 is a vertical sectional view thereof, FIG. 3 is a block diagram of the output calculation circuit, FIG. 4 is a partially cutaway perspective view showing the state of use, and FIG. FIG. 5 is a sectional view showing another state of use, and FIG. 6 is a waveform chart at each part of the output calculation circuit. (1): Defect inspection camera, (2): Lens, (3) Dual reflective mirror, (4): Ridge line, (5), (6) Dual reflective surface, (7
), (8): Linear image sensor, (10): Output calculation circuit,
(11): Differential calculation circuit, (12): Digital conversion circuit, (13): Masking circuit.

Claims (1)

[Claims] A reflector (3) having two reflective surfaces (5) and (6) is installed on the axis (l) of the lens (2) with a ridgeline (4) perpendicular to the axis (l) in between, and each reflection Surface (5), (
6) Two linear image sensors (7) that receive reflected light from
, (8), and an output calculation circuit (10) of the defect inspection camera (1),
The output calculation circuit (10) includes two linear image sensors (7),
(8) A differential arithmetic circuit (11) that obtains a difference signal from the output of A surface defect inspection apparatus comprising: a masking circuit (13) for masking an end of the digital signal using a blanking signal narrower than the field of view.