JP2856498B2 - Cylindrical surface image capture device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a cylindrical image capturing apparatus, and more particularly, to a cylindrical image capturing apparatus applicable to inspection of a cylindrical outer peripheral surface such as a photosensitive drum of a copying machine. It concerns the device.

(Prior art) As a method of inspecting the outer peripheral surface of a photosensitive drum of a copying machine,
As shown in FIG. 7 (a), an optical flat 2 is made to face the outer peripheral surface of the photosensitive drum 1, and light is made incident on the optical flat 2 so that light reflected from the optical flat and the outer peripheral surface of the drum is converted from interference fringes. A method for inspecting the surface condition (see JP-A-62-52408) and a visual inspection method. As shown in FIG. 8, the illumination light from the illumination light source 4 is directly applied to the peripheral surface of the photosensitive drum, and the camera 5 and the like are used. A method of taking in a drum surface image and inspecting it with the image processing device 6.

(Problems to be Solved by the Invention) As shown in FIG. 7 (b), the conventional inspection method employs a surface of an optical flat 2 and a photosensitive drum 1 as shown in FIG.
When the change in the distance from the outer peripheral surface increases, the density of the interference fringes 3 increases and measurement becomes impossible. For example, interference fringes can be observed in a portion where the optical flat surface and the outer peripheral surface of the photosensitive drum are close to each other, but as the distance increases, the fringe density increases and the observation becomes impossible. Therefore, the observable outer peripheral surface of the photosensitive drum is limited to a narrow range.

In the inspection method (1), since the outer peripheral surface of the photosensitive drum is glossy, it is difficult to visually observe the surface, and the burden on the observer increases.

In the inspection method of (1), for adjusting the exposure of the camera, the illumination must be arranged so as not to take in the directly reflected light due to the gloss, and since the drum surface is a curved surface, the drum image 1 shown in FIG. As is apparent from the comparison between the codes A and B, the illuminance unevenness is remarkable, and there is a problem that the observable area is limited to a narrow range near the top viewed from the camera.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a cylindrical surface image capturing device that can obtain a wide observation area in which uneven illuminance is eliminated on a cylindrical surface to facilitate inspection and improve accuracy.

(Means for Solving the Problems) In order to achieve the above object, in a cylindrical surface image capturing apparatus according to the present invention, a light source for generating a plane wave, an optical system for converting the plane wave into a columnar wave, An imaging optical system having a cylindrical surface as an object surface, which is installed so that the wavefront of the surface wave coincides with the curvature, and an area image sensor installed on the image plane of the imaging optical system are provided.

In this case, a diffusion plate may be provided on the image plane of the imaging optical system, and a variable focal length lens and an area sensor for re-imaging an image on the diffusion plate may be provided.

(Operation) The area to be detected on the outer peripheral surface of the photosensitive drum is irradiated with the light of the columnar wave according to the curvature of the area.

(Embodiment) Example 1 (see FIGS. 1 to 5) In FIG. 1 showing the entire configuration of a cylindrical surface image capturing apparatus according to the present invention, an object surface is placed with an imaging optical system 12 interposed therebetween. The photosensitive drum 1 as a subject is disposed on the side, and an area image sensor 13 is disposed on the image plane side. That is, the imaging optical system 12 is provided to establish an imaging relationship between the outer peripheral surface of the photosensitive drum 1 and the area image sensor 13. The half mirror 9 and the beam expander rear group 10 are arranged on the optical axis of the imaging optical system 12 and between the imaging optical system and the photosensitive drum in order from the side closer to the imaging optical system. , A cylindrical optical system 11 is provided. The light source 7 and the front group 8 of the beam expander are arranged at positions where light is incident on the rear group 10 of the beam expander via the half mirror 9.

Here, the light source 7 generates a plane wave, and for example, a laser light source is used. The cylindrical optical system 11 is a condensing lens having no power in the axial direction of the photosensitive drum, has a function of converting a plane wave into a columnar wave, and includes a cylindrical lens or the like.

Hereinafter, the irradiation process and the imaging process will be described separately.

First, regarding the irradiation process, in FIG. 1 in which an illumination optical system is taken out and shown in FIG. 1, light emitted from a light source is divided into a beam expander front group 8, a half mirror 9,
After passing through the beam expander group 10, it becomes a plane wave. Then, a cylindrical wave having a curvature matching the outer peripheral surface of the photosensitive drum 1 is formed by the cylindrical optical system 11. It is assumed that the photosensitive drum 1 is disposed in advance at a position where the curvature of the outer peripheral surface matches the curvature of the columnar wave.

Therefore, in the irradiation area of the columnar wave on the outer peripheral surface of the photosensitive drum, there is no illuminance unevenness.

Next, in the image forming process, in FIGS. 3 to 5 in which the image forming optical system is taken out and shown in FIG. 1, the reflected light from the peripheral surface of the photosensitive drum is reflected by the cylindrical optical system 11, the beam expander Rear group 10, half mirror 9, imaging optical system 12
Then, an image is formed on the area image sensor 13 via.

Thus, the area image sensor 13 captures the image information of the drum outer peripheral surface. The subsequent image processing is performed by known means.

In the case of this example, uniform illumination is performed in the irradiation area on the outer peripheral surface of the photosensitive drum, so that a relatively large observable area can be obtained.

Example 2 (See FIG. 6) The difference between the configuration of Example 2 and Example 1 is that a diffusing plate such as frosted glass is provided between the imaging optical system 12 and the area image sensor 13.
14 and a variable focal length lens 15.

In this example, an image on the outer peripheral surface of the photosensitive drum is formed on the diffusion surface of the diffusion plate 14. Then, an image is re-imaged on the area image sensor 13 by using the focal length variable lens 15 from behind the diffusion surface, and is taken in.

In the case of this example, the image on the outer peripheral surface of the photosensitive drum can be captured by the variable focal length lens 15 at an arbitrary magnification.

It should be noted that the imaging optical system 12 may have a variable focus function instead of the variable focal length lens 15, but it is considered that the example shown in the figure has less burden on the optical system.

In this example, since a diffusing plate and a variable focus lens are added as the image forming means, the image on the outer peripheral surface of the photosensitive drum can be captured at an arbitrary magnification, and there is an advantage that the adaptability to the size of the defect is increased. is there.

(Effects of the Invention) According to the present invention, it is possible to obtain a wide observation area in which uneven illuminance is eliminated on a cylindrical surface, facilitate inspection, and improve accuracy.

[Brief description of the drawings]

FIGS. 1 and 6 are diagrams illustrating the overall configuration of the apparatus according to the present invention, FIG. 2 is a diagram illustrating an illumination process, FIGS. 3 and 4 are diagrams illustrating an imaging process, FIG. 5 is a perspective view illustrating the configuration of the imaging system in FIG. 1 taken out and described, and FIGS. 7 and 8 are explanatory views of the prior art. 4 ... Illumination light source, 11 ... Cylindrical optical system, 12 ...
Imaging optical system, 13 area image sensor, 14 diffuser plate, 15 focal length variable lens.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04N 5/225 H04N 1/04 102

Claims (2)

(57) [Claims] 1. A light source for generating a plane wave, an optical system for converting the plane wave into a columnar wave, and an image forming optical system having an object surface on a cylindrical surface installed so that the wavefront of the columnar wave coincides with the curvature. A cylindrical surface image capturing device comprising: a system; and an area image sensor installed on an image plane of the imaging optical system. 2. The image forming apparatus according to claim 1, further comprising a diffusing plate provided on an image plane of the image forming optical system, and a variable focal length lens and an area sensor for re-imaging an image on the diffusing plate. Cylindrical surface image capture device.