JP2761736B2 - Image reading device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a sheet-through type image reading apparatus.

(Prior Art) Conventionally, this type of image reading apparatus first performs shading correction by irradiating a white reference plate disposed above a document glass with a light source, and then irradiates the document with a line image. The image is read by detecting with the sensor.

(Problems to be Solved by the Invention) However, the line image sensor cannot accurately detect the boundary of the document, so that the document image cannot be trimmed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet-through type image reading apparatus capable of detecting a boundary of a document by a line image sensor and capable of trimming a document image.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a light source for irradiating a document, document conveying means for conveying a document in a direction intersecting the longitudinal direction of the light source, and reflection from the document. Means for converting light into an electric signal by forming an image on a line image sensor via an optical system, and irradiating the original after irradiating a white substrate and performing shading correction; When the document is irradiated, the white reference plate is moved from the irradiation position, or a shielding means is provided for blocking the irradiated portion of the white reference plate.

(Operation) The operation of the present invention based on the above configuration is as follows. First, the white reference plate is irradiated with the light from the light source to perform shading correction.
After the document irradiation is completed, the process returns to the initial state.

Embodiment Next, the present invention will be described based on an embodiment shown in the attached drawings.

FIG. 1 shows a first embodiment of the present invention, wherein 1 is an image reading apparatus of the present application, 2 is a light source for irradiating a document P conveyed by a conveying means (not shown), 3 is a reflection mirror, and 4 is a lens. Reference numeral 5 denotes a line image sensor that converts reflected light irradiated on the document P into an electric signal. 6 is the original P to be conveyed
This is a detecting means for detecting the front end and the rear end of the image.

 Reference numeral 7 denotes a white reference plate provided above the original glass 8.

Reference numeral 9 denotes a shielding means provided on the lower surface of the white reference plate 7, and the shielding means 9 is for shielding the irradiated portion of the white reference plate 7 when irradiating the original. The shielding means 9 includes a black plate 10, a tension spring 11 for holding the black plate 10 at a solid line position, and a solenoid 12 for moving the black plate 10 to a position indicated by a two-dot chain line against the tension spring 11. Have been. FIG. 2 is a block diagram showing these configurations.

Next, the operation of the first embodiment will be described with reference to the flowchart shown in FIG.

First, when the reading button (not shown) of the operation unit is pressed while the document P is set (step), the light source 2 is turned on (step). Then, after the presence or absence of the document P is determined (step) by the detecting means 6, a reading / reading command is issued from the control unit to the line image sensor 5 (step), and the light source 2 irradiates the white reference plate 7 to record a shading waveform. (Step) is performed and the original P
Can be determined. The state shifts to “reading state” (step).

Then, the solenoid 12 is turned on, the black plate 10 is pulled in the direction of arrow a to move the black plate to the position indicated by the two-dot chain line, and the conveyance (step) of the document P is started, and the light source 2 irradiates the document P Then, the original is read by the line image sensor 5 (step). Then, after the reading of the document is completed, the detecting means 6 detects the rear end of the document P (step), the solenoid 12 is turned off, and the tension spring 11 pulls the solenoid 12 in the direction of arrow b to return to the initial position indicated by the solid line (step). It will be.

FIG. 4 shows a second embodiment of the present invention. In the case of the second embodiment, the white reference plate 7 is at the position indicated by the solid line when the shading waveform is recorded, and the leading end of the document P is detected by the detecting means 6.
Is detected, the solenoid 12 is turned on, the white reference plate 7 is pulled in the direction of arrow c, and moves to the position indicated by the two-dot chain line. After the reading is completed, the detecting means 6 detects the rear end of the document P and the solenoid 12 is turned off.
As a result, it is pulled in the direction of arrow d and returns to the initial position. Other configurations are the same as in the first embodiment.

FIG. 5 shows a third embodiment of the present invention. In the third embodiment, a white reference plate 7, a solenoid 12, a tension spring 11
Is provided on the lower surface side of the original glass 8, and is configured to operate in exactly the same manner as in the second embodiment.

FIG. 6 shows a fourth embodiment of the present invention. In the figure, reference numeral 13 denotes a liquid crystal shutter provided on the lower surface of the white reference plate 7. When the detecting means 6 detects the leading end of the document P, the liquid crystal shutter 13 is in a "closed" state to shut off the light source 2 and the white reference plate 7. The document is read, and after the reading of the document is completed, when the detecting means 6 detects the trailing edge of the document P, it returns to the "open" state, and waits for the next shading recording.
Other configurations are the same as those of the other embodiments.

FIG. 7 shows a fifth embodiment of the present invention. In the figure, reference numeral 14 denotes a plate member, which is a white reference plate 7 and a black plate 10.
And the front and back sides are formed, and are rotatably supported by a rotating shaft 15 orthogonal to the conveying direction of the document P. The rotating shaft 15 is moved 180 ° by a driving means (not shown) such as a stepping motor as shown by an arrow (the direction may be reversed).
° It is configured to rotate.

That is, when the shading waveform is read, the white reference plate 7 is located on the lower surface side as shown in the figure, and when the detecting means 6 detects the leading edge of the document P, the driving means is driven to rotate by 180 ° and the black plate 10 And the original is read. Then, after the reading of the document is completed, the detecting means 6 sets the document P
When the rear end is detected, the driving means is driven again to rotate by 180 °, and the white reference plate 7 returns to the initial state with the lower surface side.

(Effects of the Invention) According to the present invention, the reading position of the image line sensor is moved in the direction intersecting with the line sensor to read the image by reading the image. Boundary detection is
This has become possible with a through-type image reading device, and accurate position detection of a document and trimming of a document image have also become possible with a sheet-through type image reading device.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 1 is a schematic explanatory view of the first embodiment, FIG. 2 is the same block diagram, FIG. 3 is the same flowchart, and FIGS. FIG. 14 is a schematic explanatory view of the second, third, fourth, and fifth embodiments. DESCRIPTION OF SYMBOLS 1 ... Image reading apparatus of the present application, 2 ... Light source 5 ... Line image sensor 7 ... White reference plate, 9 ... Shielding means P ... Original

Claims (1)

(57) [Claims] A light source for irradiating a document, document transport means for transporting the document in a direction intersecting the longitudinal direction of the light source, and a line image sensor for receiving reflected light from the document and reading the document. An image forming apparatus for reading a document being moved by a document conveying means on a predetermined reading line in a document conveying path; a white reference plate for shading correction, a black plate, illumination on the reading line and the light source. And a switching unit that switches so as to arrange either the white reference plate or the black plate at a position where the image reading is performed.