JP2003037711A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader that increases the illuminance of an original face at a read position. SOLUTION: A fluorescent lamp 40 with a fluorescent tube 42, placed in parallel with an original face, is turnalby supported by bearings and a drive section 30 drives the fluorescent lamp 40. The drive section 30 can drive the fluorescent lamp 40, in response to variations in a direction of a read position, when viewed from the fluorescent tube 42 in response to variations of a distance between an original platen glass plate 10 and the original side. A microcomputer 80 controls the drive section 30, on the basis of an image signal outputted from a CCD image sensor 35 to make the illuminance of the original face on a read line increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device.

[0002]

2. Description of the Related Art Conventionally, image reading devices such as scanners, copying machines, and facsimiles have been known. In these image reading apparatuses, image data is generated by scanning a document illuminated on a fluorescent lamp. The higher the illuminance of the original, the better the reading performance of the original. A fluorescent lamp for an image reading apparatus includes a transparent member such as a glass tube in which an inert gas is sealed and a fluorescent film is formed on the inner wall. Generally, the outer wall of a transparent member such as a glass tube is provided with a light shield having an opening, so that the illuminance distribution in the lamp circumferential direction is not uniform.
Further, even in the light emitted from the opening, the illuminance distribution in the lamp circumferential direction is not uniform, and for example, the illuminance is highest at the circumferential center of the opening. Therefore, in order to improve the reading accuracy of the document, it is desirable to set the mounting angle of the lamp in the circumferential direction so that the illuminance on the document surface becomes the highest.

[0003]

By the way, there is known an image reading apparatus having an automatic focus adjustment function for scanning a document that cannot be brought into close contact with the platen glass with high precision. In automatic focus adjustment in an image reading apparatus, for example, a mirror in the optical path is moved to adjust the optical path length and focus. On the other hand, the tube end members provided at both ends of the fluorescent tube for fixing the fluorescent lamp to a mating member such as a carriage generally have positioning portions for fixing the position and angle of the lamp and are fixed to the fluorescent tube. . For this reason, the mounting angle of the fluorescent lamp in the circumferential direction cannot be changed after the fluorescent lamp is mounted on the image reading device by bringing the positioning portion of the tube end member into contact with the carriage or the like. Therefore, in the conventional image reading apparatus, even if the optical path length of an original that cannot be brought into close contact with the original glass is adjusted and focused, the illuminance on the original surface may be low at the focal position.

It is an object of the present invention to provide an image reading device which increases the illuminance of the original surface at the reading position.

[0005]

According to the first aspect of the present invention, a fluorescent lamp having a fluorescent tube parallel to the document surface is provided on a carriage or the like which reciprocates in parallel to the document surface. The bearing is rotatably supported, and the drive unit rotates the fluorescent lamp. This makes it possible to rotate the lamp in the circumferential direction after mounting the lamp. In other words, the direction of the reading position seen from the fluorescent tube changes due to the change in the distance between the transparent member for placing the original such as the original platen glass and the original surface, and the driving unit rotates the fluorescent lamp accordingly. Can be made. Therefore, in the invention according to claim 1 of the present invention, the illuminance of the document surface at the reading position is increased by controlling the drive unit by the control unit based on the image signal output from the image pickup unit.

According to the second aspect of the present invention, there is provided automatic focus adjusting means for changing the optical path length from the document to the light receiving surface of the image pickup section for focusing on the basis of the image signal output from the image pickup section. Therefore, the control unit and the automatic focus adjustment unit can be linked to scan a document that cannot be brought into close contact with the platen glass with high precision.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment showing an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing a scanner according to an embodiment of the present invention. The original 90 represents an original that is floating from the original plate, and the original 91 represents an original that is in close contact with the original plate. This scanner forms an image of the originals 90 and 91 illuminated by the fluorescent lamp 40 on the CCD line sensor 35 using the optical system 20 such as a lens,
The image reading device scans the originals 90 and 91 and outputs image data. The present invention includes a scanner, a copying machine,
The present invention can be applied to various image reading devices such as a facsimile that irradiates a document with a light source to form an image on an imaging device.

The original platen glass 10 is a transparent plate-like member on which an original is placed. The fluorescent lamp 40 serving as a light source for illuminating the document surface is rod-shaped, is parallel to the document-side plane of the document table glass 10 on the opposite side of the document table glass 10 from the CCD,
The line sensor 35 is provided in parallel with the arrangement direction of the light receiving elements. The fluorescent lamp 40 has a fluorescent tube 42 in which a fluorescent film 46 is formed on the inner wall of a transparent tubular member such as a glass tube. The fluorescent tube 42 is filled with a xenon gas or a mixed gas of an appropriate amount of mercury and an inert gas such as argon. The electrodes of the fluorescent tube 42 can be provided on both ends or the outer wall of the fluorescent tube 42. When the electrodes are provided on the outer wall of the fluorescent tube 42, the blackening of the end portion of the fluorescent tube 42 can be reduced. Fluorescent tube 42
A light-shielding body 41 such as an electrode is provided around the area. The light shield 41 covers the outer wall of the fluorescent tube 42 with an angular width of about 300 ° about the axis of the fluorescent tube 42. Therefore, the fluorescent lamp 40 has an opening 43 extending in the axial direction with an angular width of about 60 °.

As shown in FIGS. 2 and 3, a fluorescent lamp 40
A tube end member 45 that seals gas in the fluorescent tube 42 is fixed to both ends of the tube. The tube end member 45 is formed in a cylindrical outer shape and is rotatably supported by the bearing 44. Bearing 4
4 is fixed to the carriage 26 as shown in FIG. As shown in FIGS. 2 and 3, one tube end member 45 is provided with a gear 33 that constitutes a worm gear for rotating the fluorescent lamp 40. The gear 32 forming the worm gear meshes with the gear 33 and rotates together with the rotation shaft of the motor 31. The motor 31 is driven by a drive circuit (not shown). The worm gear, the motor 31, and the drive circuit constitute the drive unit described in the claims.

The optical system 20 shown in FIG. 1 includes a fluorescent lamp 40.
The reflected light image of the original illuminated by the CCD line sensor 35
Mirrors 21 and 2 shown in FIG.
2, 23, 24 and a condenser lens 25.
Some of the components of the optical system 20 are movable, and these movable components constitute the automatic focusing means described in the claims. The movable element of the optical system 20 changes the optical path length from the document surface to the light receiving surface of the CCD line sensor 35 by being driven by a driving unit (not shown), and the document lifted from the document glass 10 as shown in FIG. It is possible to focus the position of A with respect to 90. For example, the optical path length can be changed by moving the movable mirrors 23 and 24 as a set in a direction parallel to the document surface.

The CCD line sensor 35 constitutes the image pickup section described in the claims. CCD line sensor 3
Reference numeral 5 has a large number of light receiving elements arranged in parallel with the axial direction of the fluorescent lamp 40. The light receiving element accumulates an amount of electric charge according to the amount of light incident on the light receiving surface. The charges accumulated in the light receiving element are transferred to the analog shift register by the pulse input to the transfer gate. The charges transferred to the analog shift register are transferred to the charge-voltage converter by the pulses that are sequentially input, and converted into a voltage. The output signal of the CCD line sensor 35 is input to an AFE (Analog Front End) chip 50.

The AFE chip 50 includes a CCD control circuit, an amplifier, an A / D converter, etc. (not shown), samples an analog signal input from the CCD line sensor 35 and converts it into a digital signal, and an image processing ASIC (Applicat.
Ion Specific Integrated Circuit) 60.
Various pulses for controlling the CCD line sensor 35 are output from the CCD control circuit.

The image processing ASIC 60 compares the white reference data obtained by reading the white reference before the start of reading with the black reference data stored in advance,
Various signal processes such as correction of variations in sensitivity of each element in the CCD line sensor 35, correction of variations in luminance in the axial direction of the fluorescent lamp 40, gamma correction, and color correction are performed.

The interface section 70 constitutes an interface for connecting a computer (not shown) and the scanner. The microcomputer 80 is a C (not shown).
The AFE chip 50 includes a PU, a RAM, a ROM, etc., and executes firmware stored in the ROM.
It controls the image processing ASIC 60, the interface unit 70, the drive unit 30, and the like. The microcomputer 80 is AFE
The light receiving amount of each light receiving element of the CCD line sensor 35 is detected based on the digital signal output from the image processing ASIC 60 or the image processing ASIC 60. The microcomputer 80 constitutes the automatic focus adjusting means described in the claims, and the optical system is arranged so that the difference in the amount of light received between the adjacent light receiving elements becomes the maximum based on the detection result of the amount of light received by each light receiving element. The optical system 20 is focused on the document surface by feedback controlling the movable elements of 20. The microcomputer 80 constitutes the control means described in the claims, and feedback-controls the drive unit 30 to rotate the fluorescent lamp 40 so that the amount of light received by the light-receiving element becomes maximum.

The configuration of the scanner according to the embodiment of the present invention has been described above. FIG. 5 is a schematic diagram for explaining the distance from the platen glass 10 to the document and the illuminance distribution on the document surface. L1 is a fluorescent lamp 4 for the original 90
The illuminance distribution in the original 90 before adjusting the irradiation angle of 0 is shown. L2 indicates the illuminance distribution on the original 91. L3 is a fluorescent lamp 40 for the original 90
9 shows the illuminance distribution on the original 90 after adjusting the irradiation angle of.

When the surface of the original is illuminated by the fluorescent lamp 40, the illuminance on the original is generally such that a virtual plane connecting the central axis of the fluorescent tube 42 and the central portion of the opening 43 intersects the original surface as shown in FIG. It becomes the largest near the appearing virtual straight line.
Therefore, the document 9 that is far from the platen glass 10
The peak position C of the illuminance at 0 is farther from the fluorescent lamp 40 than the peak position D of the illuminance at the original 91 that is closer to the platen glass 10. On the other hand, the focus position of the optical system 20 moves on the straight line AB perpendicular to the document surface by the focusing operation under the control of the microcomputer 80 when the distance from the document table glass 10 to the document changes. The focusing operation here means, for example, the mirrors 23 and 24 shown in FIG.
Is the move. The focus position of the optical system 20 corresponds to the reading line. When the original 90 is lifted from the platen glass 10 and the peak position of the illuminance changes from D to C along the original surface, the original surface illuminance on the reading line of the original 90 decreases from M1 to M3. At this time, the microcomputer 80 is arranged so that the amount of light received by the light receiving element is maximized.
When the fluorescent lamp 40 is rotated by feedback control of the motor 31, the peak position of illuminance can be moved from C to D along the document surface, and the peak position of illuminance can be converged on the reading line. At this time, in the reading line of the original 90, the original surface illuminance increases from M3 to M2. As described above, according to the scanner of this embodiment, the illuminance of the document surface on the reading line can be increased. The fluorescent lamp 40 may be rotated before or after the focusing operation.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a scanner according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a fluorescent lamp, a bearing, and a driving unit according to an embodiment of the present invention.

FIG. 3 is a plan view showing a fluorescent lamp, a bearing, and a driving unit according to an embodiment of the present invention.

FIG. 4 is a schematic diagram showing an image pickup unit according to an embodiment of the present invention.

FIG. 5 is a schematic diagram for explaining a distance from a platen glass to a document and an illuminance distribution on a document surface.

[Explanation of symbols] 10 Platen glass 20 Optical system 21, 22, 23, 24 Mirror 25 Condensing lens 26 carriage 30 Drive 31 motor 32 gears 33 gears 35 CCD line sensor 40 fluorescent lamp 41 light shield 42 Fluorescent tube 43 opening 45 Pipe end member 46 Fluorescent film 60 Image processing ASIC 70 Interface unit 80 microcomputer 90 manuscripts 91 manuscript

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H109 AA02 AA15 AA23 AA32 AA92                       AB00 AB22 AB23                 2H110 AA01 AA22 AC03 CC01 CD05                 5C051 AA02 CA07 DB24 DC04 DC07                       DE09 FA01                 5C072 AA03 BA15 CA06 HA02 HA13                       XA05

Claims (2)

[Claims] 1. A fluorescent lamp having a fluorescent tube parallel to a document surface, a bearing for rotatably supporting the fluorescent lamp, a driving unit for rotating the fluorescent lamp, and a document irradiated on the fluorescent lamp. An image pickup unit that receives the reflected light or transmitted light of the document and generates an image signal corresponding to the optical density information of the document, and the document surface by controlling the drive unit based on the image signal output from the image pickup unit. An image reading apparatus comprising: a control unit that increases illuminance. 2. An automatic focus adjusting means for changing the optical path length from the document to the light receiving surface of the image pickup unit to focus on the basis of an image signal output from the image pickup unit. Item 1. The image reading device according to item 1.