JPS61149920A - Image reader - Google Patents

Abstract

PURPOSE:To prevent a decrease in resolving power by supporting an original platen glass plate on only two sides parallel to a line sensor, correcting the deflection of the original platen glass plate in a subscanning direction by a sliding body, and scanning and reading an original. CONSTITUTION:Rolls 6 and 7 are pressed against the lower part of original platen glass 8 and the slider 11 is moved on a rail 19 while the distance between a lens array 1 and the original platen glass plate 8 is held within the depth of focus of the lens array 1, thereby scanning the original. Consequently, the strain of the original platen glass 8 in the subscanning direction is held within the focus all the time by correcting the distance between the lens array 1 and original platen glass 8 by the rolls 6 and 7. The original platen glass 8 is supported on only two sides parallel to the line sensor. Consequently, even if the glass plate flexes, there is no deflection in a main scanning direction and sufficient accuracy is obtained by original scanning because the rolls are applied, thereby preventing a decrease in resolving power.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an image reading device, and more specifically, a sensor array that scans a document surface in a sub-scanning direction and is arranged in accordance with the width of a read image in a main scanning direction. The present invention relates to an image reading device that reads an image of a document by projecting an image thereon.

Conventional technology Conventionally, image reading devices place a document on a document table, scan the surface of the document by mirror scanning or moving the document table, and form an image on a solid-state image sensor using a small lens system. There are image reading devices that read images. In something like this,
Since a complicated optical system with a reduction lens is used, the overall size of the apparatus becomes large, and the adjustment becomes a hindrance.

On the other hand, in recent years, an image reading device has been developed that scans the surface of a document in the sub-scanning direction and projects an image onto a sensor array arranged in correspondence with the width of the scanned image in the main-scanning direction to read the document image. This device has the advantage of being simple in configuration, requiring few assembly and adjustment parts, and being inexpensive. However, on the other hand, this image reading device uses a converging light transmitter array and a spherical lens array (hereinafter referred to as lens array) to form an image on the sensor array. )
Since the depth of focus is shallow, the distance between the lens array and the document surface on the glass surface deviates from the depth of focus of the lens array due to the deflection of the glass surface of the document mounting table and the deflection of the sensor scanning guide rail. , T, F (mod
ulation transfer function
), which causes inconveniences such as a significant decrease in

Problems to be Solved by the Invention The present invention is an image reading system that scans the surface of a document in the sub-scanning direction and projects an image onto a sensor array arranged in correspondence with the width of the scanned image in the main scanning direction to read the document image. It is an object of the present invention to provide an image reading device in which resolution does not deteriorate due to bending of a glass plate on which a document is placed.

In order to solve the problems, the present invention includes a holding member that holds a sensor array and an imaging optical system for projecting a document image onto the sensor array, and a holding member that is provided on the holding member and at least two sliding bodies that come into contact with and slide on the document-placing glass plate in order to position the document-placing glass plate with respect to the document-placing glass plate; a holding mechanism that holds the holding member in a vertically movable state; The present invention is characterized by comprising a biasing means for biasing the storage member so as to come into pressure contact with the document-placing glass plate, and a support means for supporting the document-placing glass plate only on two sides parallel to the sensor array. .

In other words, the original glass plate is held by only two sides parallel to the line sensor, the deflection of the original glass plate in the sub-scanning direction is corrected by the sliding member, and the original surface is scanned.

, +2 Embodiment FIG. 1 is a sectional view of the image reading device of this embodiment, and FIG. 2 is a sectional view of the sensor storage box (4).

As shown in Figure 2, the lens array (1), line sensor (2)
) and a sensor storage box (4) containing a lamp (3).
) is provided with a roller contact arm (5) on the side surface in the main scanning direction, and this roller contact arm (5) supports two rollers (6
).

(7) is supported in the sub-scanning direction by sandwiching the sensor storage box (4) so as to be in contact with the lower surface of the document mounting glass plate (8). Further, the sensor storage box (4) and the roller contact arm (5) are supported by a sensor storage box support arm (9) so as to be rotatable around a rotational fulcrum (10). (9
) is held by the slider 111) so as to be rotatable about the arm rotation fulcrum (121).In addition, the sensor storage box support arm (9) is rotated upward by the pressure contact spring (13) provided on the slider (11). is energized by
As a result, the rollers t6) and (7) are pressed against the lower surface of the original glass plate (8), and the distance between the lens array (1) in the sensor storage box (4) and the lower surface of the original glass plate (8) is Place the sensor storage box (4) on the original glass plate (8) so as to keep it within the depth of focus of the lens array (1).
It is positioned against. The slider (11) is equipped with wheels, and the glass plate (8) on which the original is placed.
The document is scanned by moving on a rail (161) provided at the bottom parallel to the document placement glass plate (8) and in the sub-scanning direction. Drive boolean IJ provided at both ends in the sub-scanning direction
-Cη and idle pulley (old wire (1)
The drive pulley (17) is rotated by a motor (not shown), and the wire (191) is wound around the drive pulley +1'rI, so that the slider (
11).

As described above, the rollers t61 and (71) are pressed against the lower part of the document placement glass (8), and the distance between the lens array (1) and the document placement glass plate (8) is adjusted to within the focal depth of the lens array (1). By moving the slider (11) on the rail U and scanning the original while keeping the original position at
(71), the distance between the lens array (1) and the document-placing glass plate (8) is corrected and always maintained within the depth of focus.

However, the document placement glass plate (8) in the main scanning direction
It is not possible to cope with the distortion caused by this type of scanning means alone. That is, for example, as shown in FIG.
When the original glass plate (8) is supported at its four vertices, generally the original glass plate (8) and the line sensor (
For distance 2), an accuracy of ±0.1 M is required, whereas the vertical distance is 300 M, which is commonly used in copying machines.

Tempered glass with a width of 360M and a thickness of 5H (Young's modulus 7.5x)
105Kp/ci) and apply a uniform load of 10KF to this glass plate, the displacement amount a=Q, 2m+ at the center where the maximum deflection occurs. Also, in the method of supporting the original glass plate (8) on its four sides as shown in Fig. 5, the displacement amount a=Q, 17 m under the same conditions, and the depth of focus of the lens array is deviated from M, T, F decreases.

In contrast, in the present invention, as shown in FIG. 3, the document placement glass (8) is supported by only two sides parallel to the line sensor. As a result, even if the glass plate is bent, the original document mounting glass plate (8) in the main scanning direction is not bent, and the image reading device can scan the original with sufficient precision for practical use using the roller contact described above.

FIG. 6 is a modification of the embodiment shown in FIG. The sensor storage box (104) is positioned with respect to the document mounting glass plate (1o8) by the sliding members (106) and (107) in FIG. In addition, instead of the sensor storage box support arm (9) in FIG. 1, the sensor storage box support arm (104) in FIG.
) is held in a state where it can be moved up and down.

Effects of the Invention As described above, the original glass plate is supported by only two sides parallel to the line sensor, the deflection of the original glass plate in the sub-scanning direction is corrected by the sliding body, the original is scanned, and the original image is created. Since reading is performed, it is possible to obtain an image reading device with sufficient accuracy for practical use without deterioration of resolution.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the image reading device, FIG. 2 is a cross-sectional view of the sensor storage box, FIG. 3 is a perspective view showing the method of supporting the document placement glass plate of the present invention, and FIGS. 4 and 5 are FIG. 6 is a cross-sectional view of an image reading device showing another embodiment. (1)...Lens array, +21...Line sensor, +4) (104)...Sensor storage box,
(5)...Roller contact arm, +61, (71・
...Roller, (8), (108)...Original placement glass plate, (9)...Sensor storage box support arm, (
11)...Slider, (131...Pressure spring, +151, (141'...Wheel, αe...
Rail, (1ri...drive pulley, (top...idle pulley, +191...wire, (10
6) , (107)...Sliding member, (109)
...Sensor storage box support rod. Applicant Minolta Camera Co., Ltd. Figure 1

Claims (1)

[Scope of Claims] 1. An image reading device that scans a document surface in a sub-scanning direction and reads a document image by projecting an image onto a sensor array arranged in correspondence with the read image width in the main scanning direction, A holding member that holds the sensor array and an imaging optical system for projecting a document image onto the sensor array; and a document mounting member provided on the holding member for positioning the holding member with respect to the document mounting glass plate. a sliding body that slides in contact with a glass plate; a holding mechanism that holds the holding member in a vertically movable state; and an urging member that urges the holding member in a direction in which the sliding body presses against the original document mounting glass plate. What is claimed is: 1. An image reading device comprising: a support means for supporting a document placing glass plate on only two sides parallel to a sensor array;