JPS5932723B2 - Object surface defect detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for detecting defects on the surface of an object, and more particularly to an apparatus for detecting defects on the surface of an object that measures the accuracy of the object surface using an optical system and detects defects on the surface of the object. be.

In general, optical systems are used to measure and test defects on the surface of an object to be measured, such as dirt, scratches, irregularities, and circularity, and to measure angular indexing accuracy such as gears. It is used in many ways.

A particularly important requirement when measuring and testing the accuracy of an object's surface using an optical system is to form an extremely small light spot on the object's surface in order to detect and measure the condition of the object's surface with high precision. That's true. Furthermore, in order to obtain a very small light spot, it is necessary that the measuring light beam be a single light beam and that this single light beam produce a parallel light beam. Various devices have been proposed to detect defects on the surface of objects using this type of optical device, but none of them have been able to meet the above requirements and have been lacking in reliability in terms of detected data. There are many things that are lacking. The present invention has been made in view of the above points, and its purpose is to provide a highly reliable defect detection device on the surface of an object that is easy to detect and can obtain highly accurate detection data. An embodiment of the present invention will be described below with reference to the accompanying drawings. In the drawing, 1 is a laser light source which is a light source part, and this laser light source 1
In front of the laser light source 1, a light beam refracting unit, for example, a first plane mirror 2, is located at a predetermined distance apart.
, and is installed so as to be inclined by a predetermined angle θ0 with respect to the optical path of .

In this case, the reflection surface of the first plane mirror 2 is set so that θ1=450 with respect to the output beam 11 of the laser light source 1. Reference numeral 3 designates a so-called half mirror, which is a semi-transmissive mirror whose center portion is located on the optical path of the reflected light beam 12 from the first plane mirror 2 and which is inclined at a predetermined angle θ2 with respect to the light beam 12. A second plane mirror 4 is provided at the center of one plane of the transmitting mirror 3.

This second plane mirror 4 may be a general plane mirror with good reflectivity, or may be a coated reflecting mirror. On one plane side of the semi-transparent mirror 3, a concave light projecting mirror, such as a rotating parabolic mirror 5 with an open bottom, is installed so that its central axis coincides with the optical path of the reflected light beam 13 by the second plane mirror 4. .

Inside the parabolic mirror 5 for projection, a scanning mirror 6 is installed with a reflective surface located at the focal point f1 of the parabolic mirror 5 and inclined with respect to the light beam 13, and the scanning mirror 6 rotates for scanning. The drive unit 7 is attached to the rotating shaft 8 of a motor, for example,
As this scanning mirror 6, a plane mirror or a prism can be used. On the other side of the semi-transmissive mirror 3, a concave mirror such as a rotating parabolic mirror 9 for receiving light is installed so that its center axis coincides with that of the parabolic mirror 5 for projecting light. The object to be measured 11 is placed.

In addition, the reflected light from the light receiving parabolic mirror 9 is transmitted to the semi-transmissive mirror 3.
A condensing lens 12 is installed on the optical axis of the light beam reflected by the condensing lens 12, and the focal point F3 of this condensing lens 12 is
A light receiver 13 is installed near the. The light receiver 13 has a photoelectric conversion section that converts an optical signal into an electrical signal and other control circuit sections. Next, the operation of the present detection device will be explained using the above embodiment.

When the light beam 11 from the laser light source 1 is incident on the first plane mirror 2, it is refracted and reflected in the right angle direction by the first plane mirror 2. The light enters the plane mirror 4 of No. 2, is further refracted by 90 times, and is reflected. The reflected light ray 13 from the second plane mirror 4 enters the scanning mirror 6, is refracted 904, and becomes a light ray 14 that is reflected toward the reflecting surface of the light projecting parabolic mirror 5. At this time, when the scanning mirror 6 is rotated as shown by the arrow 15 by the motor 7,
The light ray 14 forms a radial circular trajectory L1. This group of 14 radial circular light rays is reflected and refracted by the projection parabolic mirror 5 in a direction parallel to the optical axis 10, and a ring-shaped light beam L2 consisting of 15 groups of light rays is formed. After the light beam L2 passes through the semi-transmissive mirror 3, it enters the light-receiving parabolic mirror 9 and is further refracted, and the light beam L3 consisting of 16 groups of light rays passes through the parabolic mirror 9.
is focused toward the focal point F2. When the object to be measured 11 is placed within this focused light, the outer peripheral surface of the object to be measured 11 is scanned and irradiated. Now, if the object to be measured 11 is moved along the optical axis 10 as shown by the arrow 16, the object to be measured 1
1 can be scanned. If the outer peripheral surface of the object to be measured 11 is defect-free during this scanning, the object to be measured 11
From the outer peripheral surface of the detection reflected light beam 17 passes through the same optical path as the light beam 16 and enters the reflective surface of the light-receiving parabolic mirror 9 again, yielding a detection light beam L5. The detection light beam L5 is refracted in the right angle direction by the semi-transmissive mirror 3 and enters the condenser lens 12. The condenser lens 12 converges the light beam L5 to form a convergent light L6, which is condensed at a focal point F3. This focused light spot is detected by the light receiver 13 and converted into an electrical signal by, for example, a photoelectric converter. The output signal P of the light receiver 13 is guided to the display control section 14. If an oscilloscope or other signal converter is used as the display control section 14, it is possible to display the surface condition of the object to be measured 11 and obtain control signals for other devices. On the other hand, when a defect exists on the surface of the object to be measured 11, the reflected light from the object to be measured 11 is scattered or absorbed, and the amount of light incident on the light receiver 13 decreases. This means that it can be detected and displayed, or a desired control signal can be generated and detected. In the above embodiment, the output beam 11 from the laser light source 1 is directly transmitted to the second plane mirror 4 on the semi-transparent mirror 3.
It is also possible to omit the first plane mirror 2 if it is implemented so that the light can be incident on the beam. As explained above, according to the present detection device, since a laser beam is used as the scanning beam, there is no change in the amount of light due to scattering or absorption during optical scanning, and highly accurate optical scanning can be performed.

In addition, when scanning and detecting the surface of the object to be measured 11, the scanning mirror 6 is rotated to obtain a ring-shaped light beam, so the operation is only required to insert the measurement sample, making the detection work easier. High-precision measurement is possible, and since the parabolic mirror 5 is used in the scanning light flux generation section and the parabolic mirror 9 is also used in the detection light generation section, the light flux can be emitted and received in parallel, making it extremely small. It has the advantage of being able to obtain a bright light spot and detecting detailed defects with high precision.
It is particularly effective as a detection device for cylindrical objects to be measured.

[Brief explanation of the drawing]

The drawing is a configuration diagram showing an embodiment of the present invention.

Claims (1)

[Claims] 1. A semi-transmissive mirror that is arranged obliquely with respect to the optical path of a single beam from a laser light source and has a total reflection section in the center that refracts the single beam; a scanning mirror that is installed at a distance and refracts the reflected light beam from the total reflection section in a right angle direction; a rotation driving section that rotates the scanning mirror; a light projecting parabolic mirror that generates a ring-shaped parallel light beam by rotating the mirror; and a light receiving parabolic mirror that is installed on the opposite side of the semi-transmissive mirror with the same optical axis as the light projecting parabolic mirror. , a condenser lens that converges the reflected light beam reflected from the surface of the object to be measured via the light-receiving parabolic mirror, and a light receiver that receives the light condensed by the condenser lens and converts it into a desired electrical signal. An apparatus for detecting defects on the surface of an object, characterized by comprising: