Facsimile and static presentation processing – Facsimile – Picture signal generator
Reexamination Certificate
2000-08-24
2004-06-01
Lee, Cheukfan (Department: 2622)
Facsimile and static presentation processing
Facsimile
Picture signal generator
C358S496000, C358S461000, C358S483000, C250S208100, C250S559150
Reexamination Certificate
active
06744540
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a document end detecting unit for detecting a front-end or rear-end of a document moving relatively to a light source, a document reading unit which reads a document moving relatively to a light-receiving section, and a facsimile apparatus equipped with a document reading unit.
2. Description of the Related Art
An electronic equipment for processing an image such as a facsimile apparatus is equipped with a document reading unit for optically reading a document. A document reading unit comprises a light-receiving section for reading a document, a light source, and a moving system for moving a document relatively to the light-receiving section. For reading a document, it is ideal that the light source illuminates a point to be read of the document from a direction forming an angle of 45° with the surface of the document and the light-receiving section reads the surface of the document from a perpendicular direction to the surface of the document. When a document is illuminated from one direction slanting to the surface of the document, a shade caused by the thickness of the document appears in close to either the front-end or rear-end of the document. A front-end of a document is an end on the downstream side in the document moving direction, and a rear-end of a document is an end on the upstream side in the document moving direction. In the case where the light source locates on the upstream side in the document moving direction from the light-receiving section, a shade caused by a front-end of a document appears. In the case where the light source locates on the downstream side in the document moving direction from the light-receiving section, a shade caused by a rear-end of a document appears. When a shade of the front-end or rear-end appears, the light-receiving section reads the shade, so that an unnecessary black line is inserted into an image which is a result of reading.
A first method of preventing insertion of a black line caused by a shade is to place light sources both on the downstream side and the upstream side in the document moving direction from the light-receiving section and illuminate a document from both the sides of the light-receiving section. In this case, it is difficult to completely delete both shades of the front-end and rear-end of a document at a time. Moreover, since a plurality of light sources need to be placed, the production cost of a document reading unit increases.
A second method of preventing insertion of a black line caused by a shade is to accurately detect a front-end or rear-end of a document causing a shade and, based on a result of detection, eliminate a shade of the front-end or rear-end of the document from an image which is a result of reading. In view of economy, the second method is appropriate for an electronic equipment such as a facsimile apparatus as a method of preventing insertion of a black line caused by a shade. In the second method, it is necessary to accurately detect a shade of a front-end or rear-end of a document when reading the document.
In Japanese Examined Patent Publication JP-B2 2898453, the applicant of this invention discloses a document reading unit which detects a front-end of a document based on a change of outputs of reading means caused by a shade of the front-end of the document. The document reading unit disclosed in JP-B2 2898453 detects a change of outputs of reading means caused by cutting off light reflected from a white backboard whose end on the downstream side in the document transferring direction is flat, transfers the document a predetermined distance from a point in time of detecting the change of outputs, and thereafter starts to read the document.
Japanese Unexamined Patent Publication JP-A 8-214108 (1996) discloses a method of detecting a front-end of a document in a document reading unit which moves a document with a light-receiving section fixed. The document reading unit disclosed in JP-A 8-214108 further comprises a white member, which is a roller for transferring a document. The light-receiving section of the document reading unit has a portion working as a light-receiving portion for detecting a front-end other than a portion working as a light-receiving portion for reading a document. The white member is opposed to the light-receiving portion for reading a document and the light-receiving portion for detecting a front-end. The surface of the white member is white, and in order to make the light reflectivity of part of the surface of the white member lower than that of the remainder, the part of the surface of the white member has a slot or a black-colored portion. The light-receiving portion for detecting a front-end is placed on the same board as the light-receiving portion for reading a document, on the upstream side in the document moving direction from the light-receiving portion for reading a document, and opposed to the slot or the colored portion. When a document starts to move, the light-receiving portion for detecting a front-end receives light reflected from the slot or the colored portion, and when the document comes between the slot or colored portion and the light-receiving portion for detecting a front-end, receives light reflected from the document. The document reading unit determines the difference between a color of the slot or colored portion and the white color of the background color of the document based on a change over time of the amount of the reflected light, and detects the front-end of the document based on the difference.
In the case of optically detecting a front-end or rear-end of a document causing a shade, the shorter a distance from the light-receiving portion for reading a document to the light-receiving portion for detecting a front-end is, the smaller an error in detection of a front-end or rear-end caused by transfer of a document is. The smaller an error in detection of a front-end or rear-end is, the more accurately a shade caused by a front-end or rear-end is eliminated from an image which is a result of reading. The best construction of a document reading unit is the one that the light-receiving portion for reading a document also works as the light-receiving portion for detecting a front-end. In the document reading unit disclosed in JP-A 8-214108, the light-receiving portion for reading a document and the light-receiving portion for detecting an end of a document are disposed separately. Moreover, since the document reading unit of JP-A 8-214108 does not detect a shade and has the slot for lowering the light reflectivity of part of the white member, the object thereof is different from that of the invention. In the case where instead of the slot a colored portion is provided on the surface of the white member in order to lower the light reflectivity, as described in JP-A 8-214108, it becomes difficult to detect the shade.
In a document reading unit, output data showing a light-receiving result of a light-receiving section are often subjected to shading correction. In shading correction, an output waveform showing a distribution of output data from light-receiving elements with respect to positions of the light-receiving elements composing a light-receiving section is compared with a reference waveform which is set in advance, and the output waveform is corrected in accordance with the reference waveform. The reference waveform is set individually in every document reading unit. For example, in a state where a light source illuminates a white member opposed to a light-receiving section for reading a document, the light-receiving section receives light reflected from the white member, whereby in accordance with an output waveform of data outputted as a result of light-reception, a reference waveform is formed. In the document reading unit of JP-A 8-214108 mentioned before, the white member has the slot or colored portion, so that the amount of light reflected from the white member is largely different depending on a place where light is reflected. There
Masuda Ichizo
Nishikawa Takatomi
Sugahara Kenji
Birch Stewart Kolasch & Birch
Lee Cheukfan
Sharp Kabushiki Kaisha
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