Electrophotography – Image formation – To produce microimage
Reexamination Certificate
2001-10-04
2003-10-21
Ngo, Hoang (Department: 2852)
Electrophotography
Image formation
To produce microimage
C348S096000, C348S110000, C382S319000
Reexamination Certificate
active
06636713
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an image reading apparatus which comprises an image reading unit for reading an image of a document, and a photographing unit for recording an image on a photosensitive member such as a film by exposure.
BACKGROUND OF THE INVENTION
In general, an image reading apparatus (to be referred to as a “document scanner” hereinafter) for reading an image as digital image information using a photoelectric conversion element allows easy search, edit, and the like of read and stored information. However, the stored information is not legally endorsed. For example, the stored information cannot be used as an evidence in court. On the other hand, a microfilm on which an image is recorded by the microfilm photographing apparatus is legally endorsed. However, stored information does not allow easy search, edit, and the like.
In this way, the document scanner and microfilm photographing apparatus have opposite characteristics. Hence, an image reading apparatus which can utilize merits of both the microfilm photographing apparatus and document scanner by combining the photographing function of the microfilm photographing apparatus and the function of the document scanner may be proposed. That is, an image reading apparatus which allows easy search, edit, and the like of stored information, and can store information to be legally endorsed may be proposed.
A microfilm photographing apparatus (also called a rotary microfilm camera) for photographing an image on a document on a roll film by slit exposure while feeding the document at a constant speed is known. Also, an image reading apparatus for reading an image on a document by inputting it to a fixed photoelectric conversion element as a linear image while feeding the document is known. Note that the document includes not only a sheet but also thin media such as a card, label, and the like which bear images such as text, pictures, and the like.
FIG. 2
is a schematic view showing principal part of a conventional image reading apparatus.
Referring to
FIG. 2
, reference numeral
201
denotes a document serving as an object;
202
, transparent guide glass windows provided on a convey path to photograph the conveyed document
201
;
203
A and
203
B, lamps for illuminating the document to project an image onto a light-receiving element that performs photoelectric conversion or a microfilm;
204
A and
204
B, first mirrors which form an optical path for projecting the image of the illuminated document onto the light-receiving element and microfilm; and
205
, a slit for splitting the optical path of the image illuminated with lamps into the light-receiving element side and the microfilm photographing side.
Reference numeral
206
denotes a second mirror for guiding the optical path split by the slit
205
toward the light-receiving element;
207
, a third mirror for guiding the optical path split by the slit
205
toward the microfilm side; and
208
and
209
, fourth and fifth mirrors for similarly guiding the optical path toward the microfilm.
Reference numeral
210
denotes a lens for projecting the image onto the light-receiving element;
211
, a read sensor having a photoelectric conversion light-receiving element;
212
, a microfilm lens for projecting the image onto the microfilm;
213
, a microfilm; and
214
, a light amount varying unit prepared by combining two polarization plates to adjust the amount of light to be projected onto the light-receiving element. In the light amount varying unit, the two polarization plates are arranged to overlap each other, and are pivoted so that their directions of polarization cross, thereby adjusting the transmission light amount.
The overall operation will be explained first. A document
201
is conveyed by a document convey unit (not shown) to the guide glass windows. When the conveyed document has reached an image photographing area inside the guide glass windows
202
, it is illuminated by the lamps
203
A and
203
B. An image on the illuminated document is guided toward the photographing side via the first mirrors
204
A and
204
B, and its optical path is split into the read sensor side and microfilm photographing side by the slit
205
inserted between the first mirrors
204
A and
204
B, and the second and third mirrors
206
and
207
.
Of the split optical paths, the image guided toward the read sensor side is projected onto and read by the read sensor by the lens
210
via the second mirror
206
. The image read by the read sensor is captured as image data into a main body (not shown).
The other optical path split by the slit is guided to the third, fourth, and fifth mirrors
207
,
208
, and
209
, and the microfilm
213
is exposed with the illuminated image via the microfilm lens
212
.
Read by the read sensor and photographing on the microfilm are done using identical light source light, as can be seen from the arrangement of the optical path.
However, in the aforementioned prior art, since a document is illuminated using a single light source, wavelength ranges and light amounts respectively suitable for the light-receiving element that performs photoelectric conversion, and a photosensitive material such as a microfilm or the like cannot be selected.
FIG. 6
shows an example of the characteristics of the photosensitive material and light-receiving elements depending on the light amount.
As can be seen from
FIG. 6
, when an exposure value is set to obtain an image having an appropriate density upon microfilm photographing, an appropriate image can be photographed on the microfilm. However, that exposure value results in an excessive light amount on the light-receiving element that performs photoelectric conversion, and the read image suffers fog and blurred text, resulting in poor reproduction of details.
Hence, the light amount varying unit such as a filter or the like described in the prior art is required on the optical path between the slit and light-receiving element so as to obtain an appropriate light amount on the light-receiving element. However, such unit may deteriorate image quality. Furthermore, as can be seen from
FIG. 3
, the light-receiving element that performs photoelectric conversion, and photosensitive material have different photosensitive characteristics.
As can be seen from the above description, when a single light source is used, it is very troublesome to adjust light source light to the photosensitive characteristics of both the light-receiving element and photosensitive material so as to obtain an optimal image, resulting in an expensive apparatus.
In order to allow density adjustment on the photoelectrically converted image side, the light amount varying unit described in the prior art is required, resulting in a complicated mechanism.
In addition, the density of the photographed image on the microfilm changes depending on the image density of the document upon photographing and the characteristics of a developing machine. In this case, the exposure value must be adjusted.
Likewise, density adjustment of the light-receiving element that performs photoelectric conversion is required in correspondence with an image on a document so as to read an image with higher quality.
Since the “exposure value—density output characteristics” of the light-receiving element and microfilm have no correlation, they must be individually set.
An image reading apparatus normally has a plurality of read resolutions, and changes the document convey speed in correspondence with the read resolution so as to take balance between the image quality and file size of the read image. Upon reading at high resolution, if the read speed per line is to be increased while setting a constant document speed, a high-speed, high-sensitivity photoelectric conversion element, and also a higher-speed image processing circuit are required, resulting in an expensive, complicated arrangement. Hence, the image reading apparatus changes and sets the document convey speed in correspondence with the read processing speed of a read processor while taking
Komuro Hiroshi
Okitsu Katsuhiko
Canon Denshi Kabushiki Kaisha
Morgan & Finnegan , LLP
Ngo Hoang
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