JP4117789B2 - Surface light source device for surface inspection - Google Patents

Description

  The present invention relates to a surface light source device for surface inspection for irradiating a surface to be inspected with parallel light and inspecting the surface for micro-defects by the reflected light.

  Patent Document 1 discloses a veneer coating surface inspection apparatus in which a straight tube fluorescent lamp as a surface light emitter that illuminates the surface of a vehicle being conveyed and a CCD camera that images an illumination area are arranged on a vehicle conveyance line. It has become. This makes it possible to discriminate from the yuzu skin without reducing the reflected light level for the yuzu skin with a gentle reflection angle by an optical system with a simple configuration that uses the diffused light of the surface light source without depending on the laser light. Based on the decrease in the reflected light level due to the change in the reflection angle, irregular micro-defects such as burrs and scratches caused by dust can be detected by image processing.

  However, since this coating surface inspection device is premised on imaging reflected light on the coating surface of diffused light, the light irradiation range for the coating surface in the horizontal width direction of the straight tube fluorescent lamp can be expanded to some extent. There remains room for improvement in terms of detection sensitivity with respect to the amount of irradiation light. Therefore, according to Patent Document 2, a surface light emitter is disposed in front of a straight tube fluorescent lamp, and has a vertically long slit having a width approximately the same as or narrower than the width thereof, and is disposed in front of the slit, and a straight tube. A vertical fresnel lens that converts the irradiation light in the width direction incident through the slit into parallel light, and the image signal level output from the image sensor is normal coating surface. There is disclosed a coating surface inspection apparatus for a vehicle which detects a minute defect occurring on a coating surface of a vehicle outer surface by detecting a decrease from a high signal level corresponding to the above.

On the other hand, vehicle lamps such as tail lamps and stop lamps using light emitting diode groups arranged in a planar shape as a light source are well known. According to Patent Document 3, a Fresnel lens is provided on the front surface of light emitting diodes arranged in a planar shape along an outer lens. There is also disclosed a vehicular lamp that is arranged to control light distribution. When a light emitting diode is used in this way, a maintenance-free light source with a long life is realized without requiring time until the illuminance becomes constant from the time of lighting as in a fluorescent lamp.
Japanese Patent Laid-Open No. 3-10150 JP 2001-133409 A JP 2000-123610 A

  In the case of a surface light source in which a slit and a Fresnel lens are arranged in front of the above-mentioned straight tube fluorescent lamp, regular reflection light from a microdefect such as a flaw that changes the reflection angle is suppressed by suppressing diffusion in the lateral width direction. Although the detection accuracy can be improved by reducing the sensitivity to high sensitivity, the range of conversion to parallel light in the width direction is limited by the shape of the straight tube fluorescent lamp. In addition, as long as a fluorescent lamp is used, it does not reach the light source of the light emitting diode group in terms of luminance stability or maintainability.

  In view of the above, an object of the present invention is to provide a surface light source device for surface inspection capable of irradiating parallel light with high accuracy over a wide range using a light emitting diode.

In order to achieve this object, according to the present invention, a surface light source for surface inspection for irradiating a surface to be inspected with parallel light and inspecting the surface for minute defects by the reflected light. In the apparatus, a light source (11) by a light emitting diode group in which a plurality of light emitting diodes (11a) arranged in an arc shape are arranged in the depth direction so that each optical axis coincides with the arc center point, and the light source A Fresnel lens (15) facing in front of the arc center point and having the arc center point as a focal point, and a lateral width of the emitted light of each light emitting diode (11a) to the Fresnel lens (15) at the focal position A slit (16) is formed vertically in the depth direction so as to reduce the incident angle in the direction, and the emitted light quantity between each light emitting diode (11a) is smoothed at the light emitting diode group or the focal position. Thus, a diffusion plate (19; 19a) is provided to widen the directivity angle of each outgoing light in the lateral width direction, and the Fresnel lens (15) passes through the slit (16) and has a wide directivity angle. The incident light is emitted in parallel along the optical axis plane including each optical axis of the light emitting diodes (11a) arranged in an arc shape .

Thereby, the irradiation light which passes the focus of the Fresnel lens (15) which is the circular arc center point of each light emitting diode (11a) of circular arc arrangement enters into the Fresnel lens (15), and is emitted as parallel light. At that time, the degree of parallel conversion of the Fresnel lens (15) is increased by the diaphragm by the slit (16), and the diffusion light (19; 19a) of the light emitted from each light emitting diode (11a) is diffused by the diffusion plate (19; 19a). The brightness is made uniform among the light emitting diodes (11a).

According to the present invention, a group of light-emitting diodes arranged in a circular arc shape can irradiate parallel light having a stable luminance over a wide range via a Fresnel lens, and thus the regular reflection light in which diffusion in the arc arrangement direction is suppressed. By processing the picked-up image, it is possible to efficiently inspect high-sensitivity, with high sensitivity, by changing the reflected light of a large range of surface defects or minute flaws in the arc arrangement direction. A surface light source having an arbitrary shape can be manufactured by the arc arrangement of the light emitting diode group. Irradiation light diffused by the light emitting diodes is narrowed by the slits to improve the parallelism, and the luminance is made uniform among the light emitting diodes by the lateral diffusion that accepts a slight decrease in parallelism.

Figure 1 on the basis of FIG. 5 will be described a test surface light source device surface according to an embodiment of the present invention. 1 and 2 show a basic configuration of a surface light source device 10 for inspecting a coating surface for a vehicle. A plurality of light emitting elements arranged in an arc shape so that each optical axis coincides with an arc center point. A light source 11 composed of a light emitting diode group in which diodes 11a are further arranged in the depth direction on a base surface 12, and a Fresnel lens 15 facing the light source in front of the arc center point and having the arc center point as a focal point F. And a slit plate 17 that forms a vertically long slit 16 in the depth direction at the position of the focal point F, and each is housed in a case 13.

  The Fresnel lens 15 is set to be wider than the horizontal width of the plurality of light emitting diodes 11a arranged in an arc shape with a radius of about 8 cm, and is arranged symmetrically with respect to a symmetry plane that divides the light source 11 into two in the depth direction through the focal point F. The incident light passing through the focal point F along the optical axis plane including each optical axis of the plurality of arc-shaped light emitting diodes 11a, that is, the plane orthogonal to the above-described symmetry plane is deflected in parallel along the optical axis plane. To do. Further, the width of the Fresnel lens 15 is 10 cm, the depth is about 30 cm corresponding to the straight tube fluorescent lamp, and the light emitting diodes 11a passing through the slits 16 having a width of about 1 cm along the optical axis surface described above. A number of Fresnel surfaces significantly larger than the number of light emitting diodes are formed in the width direction so as to emit the irradiated light in parallel. The light emitting diode 11a emits blue light, and irradiates light with a directivity angle of an emitted light amount of about ± 10 ° in the lateral direction and about ± 20 ° in the depth direction with respect to the optical axis.

  FIG. 3 shows a coating surface inspection apparatus for a vehicle using the surface light source device 10. Robots 39, 39 a are arranged on both sides of the conveyance path of the vehicle 1 and are attached to the tip portions of the robot arms 9, 9 a. An imaging device 20 including a surface light source device 10 and a CCD camera 21 as an image sensor is attached to the base portion 29. The robots 39 and 39a scan the coating surface so as to sequentially shift the imaging device 20, and can arbitrarily control the three-dimensional position facing the coating surface and the angle in the three axial directions at each scanning position. . The CCD camera 21 is oriented so that specularly reflected light having a width wider than the irradiation area on the coating surface of the Fresnel lens 15 at a front position of, for example, 50 cm and a vertical width of about 200 mm is incident.

  The imaging device 20 is attached with an image processing device 30 that detects that the image signal level output from the CCD camera 21 is lowered from a normal high signal level due to a minute defect. This image processing apparatus is configured using a personal computer, stores image signals for one screen of the CCD camera 21 stopped at a predetermined scanning position while sequentially updating it, and reads out the image signal for each pixel in the horizontal width direction. By scanning, it is detected that the falling amplitude from the high image level rising corresponding to the bright paint surface exceeds the reference value.

Further, on the premise of such a basic configuration of the surface light source, as shown in FIG. 5, the slit 16 in FIG. 1 is provided with a diffusion plate 19 that widens the directivity angle in the horizontal width direction with respect to the optical axis of each light emitting diode 11a. Be placed. Instead of the diffusion plate 19, a diffusion plate 19 a can be arranged so as to exhibit a similar function to the light emitting diode group, as shown in FIG.

The operation of the surface light source device 10 configured as described above is as follows. Due to the arc arrangement of the light emitting diodes 11a and the aperture of the slit 16, irradiation light passing through the focal point or the vicinity thereof is incident on the Fresnel lens 15, and the coating surface is irradiated with parallel light or substantially parallel light. At that time, the diffuser plate 19 diffuses the directivity angle of each light emitting diode 11a of the light source 11 in the lateral width direction within a range narrowed by the slit 16, and accepts a slight decrease in parallelism. The luminance in the horizontal width direction is made uniform between the optical axes. The imaging device 20 images the reflected light within the imaging range of the CCD camera 21 and temporarily stores the image signal in the image processing device 30. Then, as shown in FIG. 4, image data obtained by reading and scanning an image signal in a width direction of about 8 cm and a depth direction of 20 cm slightly narrower than the width of the Fresnel lens 15 in the width direction is read as shown in FIG. Then, the falling point Tf and the rising point Tr from the high image level rising corresponding to the bright paint surface are detected, and when the difference between these exceeds the reference value, the pixel line data is converted into a micro defect candidate. Judge as. Furthermore, a rectangle R circumscribed by the minute defect candidate regions formed by the pixel line data of adjacent minute defect candidates in order is created, and the vertical and horizontal lengths are respectively calculated, and any of them exceeds the predetermined length. And determined as a micro defect.

Therefore, by processing the captured image of specularly reflected light with reduced diffusion in the arc arrangement direction and uniform brightness , coating surface flaws or minute scratches are detected with high sensitivity by the reflected light. A wide range can be efficiently inspected with high accuracy by reading scanning in the horizontal direction along the optical axis surface of the light emitting diodes 11a in the arc arrangement. Moreover, it is detected with a more sensitive amplitude change by blue light having a short wavelength.

It is sectional drawing of the surface light source device for surface inspection by embodiment of this invention. It is a perspective view of the surface light source device for the same surface inspection. It is a schematic front view of the coating surface inspection apparatus for vehicles using the surface light source device for surface inspection. It is a figure explaining operation | movement of the coating surface test | inspection apparatus for vehicles. It is a schematic sectional drawing explaining the arrangement | positioning state of the diffusion plate of the coating surface test | inspection apparatus for vehicles .

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle 10 Surface light source device 11 Light source 11a Light emitting diode 15 Fresnel lens 16 Slit 19, 19a Diffusing plate 20 Imaging device 21 CCD camera

Claims (1)

In the surface light source device for surface inspection for irradiating the surface to be inspected with parallel light and inspecting the surface for micro defects by the reflected light,
A light source by the light emitting diode group in which a plurality of light emitting diodes arranged in an arc shape are arranged in the depth direction so that each optical axis coincides with the arc center point, and the light source faces the light source in front of the arc center point. And a Fresnel lens having the center point of the arc as a focal point, and vertically long in the depth direction so as to narrow the incident angle of the light emitted from each light emitting diode to the Fresnel lens in the focal position at the focal position. In addition, a diffusion plate that widens the directivity angle of each of the emitted light in the lateral width direction is provided at the light emitting diode group or the focal position so as to smooth the amount of emitted light between the light emitting diodes.
The Fresnel lens emits the emitted light having passed through the slit and having a wide directivity angle in parallel along an optical axis plane including the optical axes arranged in an arc shape. Surface light source device for surface inspection.

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