Photocopying – Projection printing and copying cameras – Illumination systems or details
Reexamination Certificate
2000-08-01
2003-04-22
Fuller, Rodney (Department: 2851)
Photocopying
Projection printing and copying cameras
Illumination systems or details
C355S067000, C382S275000
Reexamination Certificate
active
06552778
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image reading device for obtaining image data by reading light transmitted through or reflected from a frame image recorded on an original.
2. Description of the Related Art
Recent years have seen the appearance of technology in which a frame image recorded on an original such as a photographic film is read photoelectrically by a reading sensor such as a CCD. Image processing, such as enlargement or reduction and various types of correction, is then carried out on the read digital image data, and an image is formed on a recording material using laser light modulated on the basis of the digital image data that has completed the image processing.
In technology such as this, in which a frame image is read digitally using a reading sensor such as a CCD, in order to obtain an accurate image reading, the frame image undergoes a preliminary reading (known as a prescan), and reading conditions (for example, the amount of light to be irradiated onto the frame image, the charge accumulation time of the CCD, and the like) are decided in accordance with the density and the like of the frame image. The frame image is then read once again on the basis of the decided reading conditions (known as a fine scan).
In these image readings, it is common for unevenness in the amount of light to be suppressed by diffusing the illumination light using a diffusion plate before irradiating it onto the film surface so that the entire image surface of the frame image is illuminated uniformly.
If, however, there is a scratch or the like present on the image surface, the light irradiated onto the film surface is scattered by the scratch. Consequently, the problem arises that, because correct detected amounts of light which match the image information cannot be obtained by the reading sensor, variations in the amount of light and the like occur and resultingly image defect portions such as black spots and the like appear on the image.
In order to reduce the effects on an image brought about by scratches on the film surface or by dust or the like present on the optical path between the light source and the film (these will be referred to below generically as “defect portions”), it is common to provide the above diffusion plate near the film (on the light source side) so as to diffuse the illumination light, and then read the frame image using this diffused light. As a result, scratches are erased optically such that defect portions appearing on the image do not stand out.
Alternatively, technology is also proposed in which an image is read using non-visible light that does not respond to image information of the color wavelengths (i.e. wavelengths of the visible light regions), such as infrared light (IR), so as to detect only the light scattering portions caused by defect portions. The image defect portions caused by the detected defect portions are then corrected by undergoing image processing digitally (electrically), based on image information peripheral to the defect portion.
However, the optical erasing of scratches using the above diffusion plate has the drawback that the scratch erasing capability thereof is not so good as compared with that of image correction using non-visible light, although the processing speed of the optical erasing of scratches is faster than the image correction using non-visible light because detection of defect portions using non-visible light (i.e. image reading) is not carried out in the optical erasing of scratches.
In contrast, electrical image correction using non-visible light enables highly accurate correction compared with optical scratch erasure, however, it has the drawback of a slow processing speed.
Moreover, in conventional electrical correction of an image using non-visible light, a diffusion plate (for suppressing unevenness in the light amounts) is generally positioned on the identical optical path used by the light source for illumination light and the light source for non-visible light, and is used in common by both light sources. As a result, the non-visible light also ends up being diffused by the diffusion plate intended for diffusing the illumination light. The drawback thus arises that the capability of detecting defect portions is reduced.
SUMMARY OF THE INVENTION
In consideration of the above, it is a first object of the present invention to provide an image reading device capable of reading an image in accordance with desired print conditions by using different scratch erasure methods for originals. It is a second object of the present invention to improve the defect portion detection performance when electrically correcting an image using non-visible light.
The first aspect of the present invention is an image reading device for reading an image recorded on an original according to predetermined different color wavelengths comprising: a light source for visible light for irradiating light of visible light regions onto a surface of the original in accordance with the color wavelengths so as to read image information of the original; a light source for non-visible light for irradiating light of non-visible light regions onto a surface of the original in order to detect scratching on the original or dust on the optical path; a diffusion member that is provided on an optical path of the light source for visible light and the light source for non-visible light and which makes the amount of light irradiated onto the surface of the original substantially uniform; and an image processing section for correcting the image information based on image defect portion detection information obtained by an image reading using light from the light source for non-visible light.
According to the first aspect, the light source for visible light and the light source for non-visible light are provided and a diffusion member is placed on the optical paths of both these light sources so as to make the amounts of light irradiated onto the surface of an original substantially uniform. In the image processing section, image information read using light from the light source for visible light is corrected, based on image defect portion detection information arising from scratching on the original or dust on the optical path obtained by an image reading using light from the light source for non-visible light.
Therefore, according to the first aspect, it is possible to use either of two types of scratch erasure method. Namely, if priority is to be given to the processing speed, even if the effects of scratching on the image are somewhat obvious, scratch erasure is carried out using diffused light. If priority is to be given to the image quality rather than to the processing speed, scratches are accurately corrected using scratch detection by non-visible light. By differentiating between the scratch control methods in this way, it is possible to read an image in accordance with the desired print conditions.
In the second aspect of the present invention, a preliminary reading (a prescan) of image information of the original is made using light of the light source for visible light and, based on the density of the image (the degree of the density) obtained from the reading, a switch is made between an image reading (scratch erasure) using the diffusion member using light from the light source for visible light, and image correction using light from the light source for non-visible light.
According to the second aspect, it is possible to switch flexibly between two types of scratch erasure method. For example, when the density of the image is high and the image reading speed is slow, by switching from image correction using light from a light source for non-visible light to an optical scratch erasure image reading using a light source for visible light, it is possible to prevent the reading speed from being slowed to an extreme. If, on the other hand, the density of the image is low, it is possible to employ a suitable combination of scratch erasure methods in accordance with the density, such
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