JPH11355531A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader capable of preventing non-uniformity in the density of a read original. SOLUTION: The white plate or white sheet of uniform density is placed on contact glass 1, and first and second carriages 8 and 11 are moved to the top end of the original (A). A stick-shaped light source 4 is turned on and the angle of a first mirror 7 is adjusted so as to maximize an output value while watching the output of an image sensor 13. At the top end of the original, first and second mirrors 7 and 9 are located close and hardly affected by the error of a roof angle. Next, the first and second carriages 8 and 11 are moved to the rear end of the original (B). The stick-shaped light source 4 is turned on again and the angle of the second mirror 9 is adjusted so as to maximize the output value while watching the output of the image sensor 13. When the output of the image sensor 13 is maximized, in this case, the maximum output can be provided even when the first and second carriages 8 and 11 are returned to the top end of the original again.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus, and more particularly to a digital reading optical system such as a digital copying machine and an image scanner.

[0002]

2. Description of the Related Art In a document reading apparatus such as a copying machine, a rod-shaped halogen lamp is used as a light source for illuminating a document, and a mirror-like reflecting plate is used to enhance illumination efficiency. . The reflector has a two-stage structure in front and back to eliminate the shadow of the bonded original, and has a mountain-like light distribution in the sub-scanning direction of the original scanning, and the reading position is designed to be at the top of the mountain-like light distribution. ing. Further, as means for scanning the original, a first carriage having a mirror arranged at an angle of 45 degrees with respect to the original, and a light beam bent at 90 degrees by the first carriage are turned back by 180 degrees to guide each other to the image forming means. A second carriage composed of two mirrors called roof mirrors arranged at an angle of 90 degrees is provided. In such a scanning unit, the second carriage moves at a half speed with respect to the first carriage. In this way, the distance from the original to the imaging system is made the same.

However, if the angle (dach angle) between two mirrors called a roof mirror of the second carriage is not exactly 90 degrees, the reading angle of the original at the leading edge and the trailing edge of the original will be different. This appears as an error in the reading position of the original. Even if the reading is performed at the top of the mountain-like light distribution of the light amount distribution in the sub-scanning direction at the leading end of the original, at the top of the light amount distribution at the trailing end of the original. I can no longer read. When designing the reflector, the peak of the peak of the light amount distribution is made flat so that the reading position does not deviate from the peak even if an error occurs. However, it is difficult to set the reading position in the middle of the peak of the light amount distribution due to the accuracy of the component.

[0004] In recent years, the reading speed of a document has been increased, and as a result, the accumulation time of an image sensor (CCD) has become shorter, and it has been required that the illuminance on the document surface be higher than ever. On the other hand, it is difficult to increase the lamp power for illuminating a document due to power distribution and heat generation of the entire machine. Therefore, it is necessary to increase the lighting efficiency of the reflector,
Increasing the illumination efficiency causes a problem that the peaks of the peaks of the light amount distribution cannot be flattened.

[0005] More recently, a three-line CCD has been used for reading an image of a color copying machine. In this method, three reading elements that have been subjected to RGB filters are arranged in parallel at a constant interval. That is,
Since the reading width is wide, it is desired that the peak of the light amount distribution be wider and flatter. However, high illuminance of the document surface is required due to attenuation of the light quantity by the CCD filter and high-speed reading, and the illumination efficiency is increased for the same reason, so that the peak of the light quantity distribution cannot be flattened.

As a phenomenon caused by the above, there is density unevenness of a read original. If the trailing edge of the original is lower than the original surface illuminance as described above, this causes background contamination at the trailing edge of the copy image, and vice versa.

Therefore, in this type of image reading apparatus, it is important to prevent the density unevenness of the read original, and various techniques have been proposed. For example, JP
The linear light source disclosed in Japanese Patent No. -222663 illuminates an elongated area of an irradiation target efficiently and uniformly by scattering at least a part of light from a linear light emitting portion only in a longitudinal direction of the light emitting portion. I am trying to do it. JP-A-02-
The illuminating device disclosed in JP-A-135607 has a light absorbing portion that absorbs reflected light in a reflector portion corresponding to a light emitting portion, so that unevenness in the illuminance of a document surface does not occur even when a light source having an uneven light amount is used. Like that. JP-A-02-22
The illumination device of the document reading device disclosed in Japanese Patent No. 4458 discloses a light-adjusting filter, through which light from a light source is transmitted, provided with a dimming pattern that improves the light amount distribution of the light source and makes the light source uniform. Is increasing. JP-A-02-2
In the lighting device disclosed in Japanese Patent No. 85338, a low-reflectance portion is provided at a position of a reflection plate corresponding to a light emitting unit, so that illumination light can be made uniform in a longitudinal direction.
The lighting device disclosed in Japanese Patent Application Laid-Open No. 02-287529 is
By reducing the amount of light to be illuminated on the illuminated position parallel to the linear light source corresponding to the position of the light-emitting unit, than the amount of light at the illuminated point corresponding to the position between the light-emitting units, unevenness in the amount of light on the photoconductor surface I try to prevent it. JP 03-28839A
The illumination device disclosed in Japanese Patent Laid-Open Publication No. H10-15083 discloses a device for diffusing light from a light emitting unit in a longitudinal direction of a linear light source, so that ripple unevenness at an irradiated position on a document surface when the lighting device is brought close to the document surface. We try to prevent occurrence. The image reading device disclosed in Japanese Patent Application Laid-Open No. 03-31839 is
By using a diffusing member arranged so that it can be inserted into and removed from the optical path according to the magnitude of the reflectance of the document, blooming development of the photoelectric conversion element is prevented. The image reading device disclosed in Japanese Patent Application Laid-Open No. 05-14617 discloses an image reading apparatus in which an interval between slits formed in a reflection surface of a reflection member is formed in a state corresponding to a light intensity distribution of a light source, thereby reducing an incident light intensity distribution to a photoelectric conversion element. It is made uniform so that an accurate read signal can be obtained.

In the document illuminating device disclosed in Japanese Utility Model Laid-Open Publication No. 59-87044, the shape of the lamp reflector in the longitudinal direction is changed, and the reflection area is changed at a position corresponding to each of the light-emitting segments. Is performed, the exposure amount on the photosensitive surface can be made uniform even when the lamp has a plurality of light-emitting segments. The illumination device of a copying machine disclosed in Japanese Utility Model Laid-Open Publication No. 61-89846 has a reflecting mirror located on each optical axis extending from each light-emitting portion of a tube-shaped light bulb to an optical system through a copy original through a copy original. By forming a low reflection part lower than other parts, the light going from each light emitting part with a large amount of light to the copy original is suppressed with high precision by the low reflection part on each optical axis, and the illuminance distribution on the copy original is uniform It is possible to make it. The lighting device of a copying machine disclosed in Japanese Utility Model Laid-Open Publication No. 61-89847 has a low-reflection portion having a lower reflectance than other portions on a reflecting mirror at a position facing each light-emitting portion. The portion is formed so that the reflectance increases as the distance from the light-emitting portion increases, so that the illuminance distribution on the copy document can be made uniform and the overall brightness can be improved. The lighting device disclosed in Japanese Utility Model Laid-Open Publication No. Sho 61-174257 discloses a lighting device in which a reflecting member is arranged in accordance with the light emission characteristics of a long tube light source having a multipoint light emitting portion used in a copying machine, a printer, or the like. According to the characteristic, the light amount distribution in the longitudinal direction can be easily and reliably made uniform. An optical device disclosed in Japanese Utility Model Laid-Open Publication No. 62-161240 is used for irradiating light to a document or the like in an image forming apparatus or the like. Alternatively, a low reflectance was set, and a portion facing the non-light-emitting portion was set as a flat portion or a convex portion or a high reflectance portion, and the light distribution characteristics of light emitted to a document or the like were averaged without causing ripple. The amount of light can be obtained. The image reading apparatus disclosed in Japanese Utility Model Laid-Open Publication No. 04-135070 uses a plurality of long halogen lamps as a light source for illuminating a document, and one filament position thereof faces a position between filament positions of another halogen lamp. As described above, since a plurality of halogen lamps are arranged side by side, the distribution of the irradiation light amount on the reading line of the original can be flattened, and the density unevenness of the image signal due to the uneven irradiation light amount can be reduced. ing.

An object of the present invention is to provide an image reading apparatus which aims to prevent density unevenness of a read original similarly to the above conventional techniques by an approach different from the prior art.

[0010]

According to a first aspect of the present invention, there is provided an image reading apparatus comprising: a rod-like light source; A document illumination system having a reflector to irradiate, scanning means for scanning the document illumination system to read the document, an image sensor, and optics for reflecting the document illuminated by the scanning means and forming an image on the image sensor And a mirror of the first carriage of the scanning means is provided with an angle adjusting means so that the output of the image sensor can be adjusted to be maximum.

According to a second aspect of the present invention, the second carriage of the scanning means has two mirrors, and at least one of the two mirrors has an angle adjusting means so that the output of the image sensor can be adjusted. It is characterized in that the front and rear ends of the document surface can be adjusted to be equal.

According to a third aspect of the present invention, the output of the image sensor is maximized by a mirror angle adjusting means of the first carriage at the leading end of the document surface, and the output of the second carriage is adjusted at the trailing end of the document surface. The output of the image sensor is maximized by an angle adjusting means.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram illustrating an image reading apparatus according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a contact glass on which a document is placed, 4 denotes a bar-shaped light source for illuminating the document, 5 denotes a main reflector, 6 denotes an auxiliary reflector, and 7 denotes a first mirror. , The auxiliary reflection plate 6 and the first mirror 7 as main components are referred to as a first carriage 8. 9 is a second mirror and 10 is a third mirror.
Mirrors whose main components are
Called carriage 11. Further, in the figure, reference numeral 12 denotes an optical imaging element, and reference numeral 13 denotes an image sensor (CCD). Although not shown, the present embodiment has a mechanism for rotating the first mirror 7 and the second mirror 9 in a direction perpendicular to the optical axis.

FIG. 2 shows a state in which the peak portion of the light quantity distribution does not come on the designed optical axis due to a component error or the like in the apparatus of FIG. The solid line in the figure is the optical axis in design, but does not reach the peak of the light quantity distribution, and thus does not reach the maximum light quantity.
FIG. 3 shows a state where the reading position deviates from the peak of the light quantity distribution when the roof angle of the second carriage 8 is not 90 degrees in the apparatus of FIG. In FIG. 3, (A) shows a first mirror 7, a second mirror 9,
The position of the third mirror 10 is shown, and the ideal reading position in the light quantity distribution at that time is shown by a solid line, and the actual reading position is shown by a broken line. The illuminance when the reference plate is read is indicated as a. In FIG. 3B, the positions of the first mirror 7, the second mirror 9, and the third mirror 10 at the rear end of the original are shown. The reading position is indicated by a broken line. The illuminance when the reference plate is read is indicated as b.

As can be seen from FIG. 3A, the deviation of the reading position from the ideal value due to the roof angle of the mirror of the second carriage 11 is slight at the leading end position of the original.
The deviation from the ideal value at the rear end of the document position in FIG. 3B is large, and the deviation from the flat peak portion of the light amount distribution is deviated.

Therefore, as shown in FIG. 2, in the first carriage 8 of the present embodiment, the first mirror 7 is rotated from the position 7A indicated by the solid line to the position 7B indicated by the dotted line so that the optical axis is shifted from the position indicated by the dotted line to the position indicated by the dotted line. To match the peak of the light distribution. In this case, the adjustment of the rotation angle of the first mirror 7
This can be easily performed while watching the output of the image sensor 13.

As shown in FIG. 4, the second embodiment of the present invention
In the carriage 11, by rotating the second mirror 9 from the position 9A indicated by the solid line to the position 9B indicated by the dotted line, the optical axis is changed from the position indicated by the dotted line to the position indicated by the dotted line, thereby adjusting to the peak of the light quantity distribution. In this case, adjustment of the rotation angle of the second mirror 9
As in the case of the first mirror 7 of the first carriage 8, the operation can be easily performed while watching the output of the image sensor 13.

Next, the procedure for adjusting the original reading position in the apparatus according to the present embodiment will be described. First, a white board or blank paper having a uniform density is placed on the contact glass 1, and the first and second carriages 8, 11 are moved to the leading end of the document. Next, the rod-shaped light source 4 is turned on, and the angle of the first mirror 7 is adjusted so that the output value becomes maximum while observing the output of the image sensor 13. At the leading edge of the original shown in FIG.
Since the position of the laser beam and the second mirror 9 are close to each other, the error of the roof angle is less liable to affect the first mirror 7. Next, the first and second carriages 8 and 11 are moved to the rear end of the document. Then, the rod-shaped light source 4 is turned on again, and the angle of the second mirror 9 is adjusted so that the output value becomes maximum while observing the output of the image sensor 13. If the roof angle is adjusted at the rear end of the original shown in FIG. 3B and the output of the image sensor 13 is maximized, the maximum output is obtained even if the first and second carriages 8 and 11 are returned to the front end of the original again. Can be obtained.

[0019]

According to the first aspect of the present invention, as described above, the mirror of the first carriage of the scanning means is provided with the angle adjusting means so that the output of the image sensor can be adjusted to the maximum. Therefore, the angle of the mirror of the first carriage is adjusted while observing the output of the image sensor, and the reading position is set at the center of the peak of the light amount distribution, so that the maximum output of the image sensor can be adjusted. In addition, there is an effect that an optical system without density unevenness can be obtained.

According to a second aspect of the present invention, as described above, at least one of the two mirrors of the second carriage of the scanning means includes an angle adjusting means, and the output of the image sensor is adjusted to the original surface. Since the front end and the rear end can be adjusted to be equal, in addition to the above common effects, the first
By adjusting the reading position by moving both the mirror of the carriage and the mirror of the second carriage, it is possible to read at the maximum position of the light amount distribution over the entire surface of the document.

According to a third aspect of the present invention, as described above, the output of the image sensor is maximized by adjusting the mirror of the first carriage at the leading end of the original, and the mirror of the second carriage is adjusted at the trailing end of the original. Since the output of the image sensor is maximized by adjusting the angle, in addition to the above-described common effects, there is an effect that the illumination optical system having the maximum output and no density unevenness can be easily adjusted.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating an image reading apparatus according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram showing a state in which a mountain portion of a light amount distribution does not come on a designed optical axis in the apparatus of FIG.

FIG. 3 is a conceptual diagram showing a state in which a reading position deviates from a peak of a light amount distribution when a roof angle of a mirror of a second carriage is not 90 degrees in the apparatus of FIG. 1;

FIG. 4 is a conceptual diagram showing adjustment of an angle of a mirror of a second carriage in the apparatus of FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 contact glass 4 rod-shaped light source 5 main reflector 6 auxiliary reflector 7 first mirror 8 first carriage 9 second mirror 10 third mirror 11 second carriage 12 optical imaging device 13 image sensor (CCD)

Claims (3)

[Claims] 1. A document illumination system having a rod-shaped light source, a reflector for reflecting radiation of the rod-shaped light source and irradiating a document surface, scanning means for scanning the document illumination system for reading a document, and an image sensor And an optical system for reflecting an original illuminated by the scanning means and forming an image on the image sensor, and an angle adjusting means provided on a mirror of the first carriage of the scanning means, and an output of the image sensor is provided. An image reading apparatus characterized in that the image reading apparatus can be adjusted to be maximum. 2. The scanning device according to claim 1, wherein the second carriage has two mirrors, and at least one of the two mirrors has an angle adjusting unit, and outputs from the image sensor are a front end and a rear end of a document surface. 2. The image reading apparatus according to claim 1, wherein the image reading apparatus can be adjusted to be equal. 3. An output of the image sensor is maximized by a mirror angle adjusting means of the first carriage at a front end of the document surface, and the image sensor is adjusted by an angle adjusting means of the second carriage at a rear end of the document surface. 3. The image reading device according to claim 2, wherein the output of the image reading device is maximized.