JPH09130540A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain reading of image data with high reproducibility by suppressing flair due to production of a secondary light source from a light source to an original and to improve the S/N of image data. SOLUTION: The image reader in which a carriage 7 having image sensors arranged in the main scanning direction of an original is scanned in the subscanning direction of the original to read image data on the original 1 sequentially for each line is provided with a condenser lens 13 concentrating the luminous flux from a light source onto a prescribed range in parallel with the subscanning direction of the original 1, and the condenser lens 13 is provided with an opaque slit 13a and a transparent opening slit 13b in parallel with the main scanning direction of the original.

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 used in a facsimile, a digital copying machine or the like and capable of reading multi-gray original image data.

[0002]

2. Description of the Related Art In recent years, image reading apparatuses capable of digitally reading planar image data of an original in multiple gradations and reproducing halftones have been widely used, including digital copying machines. It was

In order to accurately read image data of an original including halftones such as color originals in multiple gradations, the irradiation optical system is devised to increase the exposure light amount of the image sensor and increase the read output of the white area of the original. S / N of image data
It is important to increase the ratio, and to suppress fluctuations in the signal level of the white area of the original and floating of the black level of the original black area, which are caused by flare caused by the generation of the secondary light source from the light source, the original, and the adjacent object. .

Conventionally, in order to suppress the occurrence of flare due to the secondary light source, there is an image reading apparatus in which a light blocking member for limiting the irradiation range of the light source is provided only near the line of interest for reading an original in the vicinity of the light source.

FIG. 9 is a block diagram of a mechanical system of a conventional image reading apparatus. 1 is a document, 2 is a light source, 3 is a lens,
Reference numeral 4 is a line type image sensor such as CCD, 5 is a light blocking member (hereinafter referred to as an aperture member) provided with a slit for limiting the luminous flux of the light source 2, 6 is a document glass formed of a transparent material for holding a document, 7 Is a carriage that holds an optical system composed of the light source 2, the lens 3, the image sensor 4, and the aperture member 5, and is movable in the sub-scanning direction indicated by arrow A. Reference numeral 8 denotes a carriage drive means, which is composed of a drive pulley 9, a passive pulley 10, a drive wire 11, and a motor 12, and is configured so that the carriage 7 can be moved in the document surface sub-scanning direction.

FIG. 10 is a block diagram of a circuit system of a conventional image reading apparatus. Reference numeral 100 is an image sensor drive circuit for supplying a scan start signal HSYNC and a scan clock signal VCLK to the image sensor 4, and 101 is an image sensor from the image sensor 4. An amplifier that amplifies the image signal output to an appropriate level, and 102 is an A / D converter that quantizes the image signal from the image sensor 4 and converts it into image data of a digital value. Reference numeral 103 denotes a shading correction circuit that normalizes and corrects image signal output variations in the main scanning direction, which are caused by nonuniformity of light emitted from the light source and variations in sensitivity of each pixel of the image sensor 4, and the like. Interface circuit for accumulating a predetermined amount of the image signal and outputting the same in synchronization with the instruction of an external device (not shown), 105 is a motor drive circuit for rotating the motor 12 at an arbitrary speed, 106 is a light source 2, an image sensor A CPU that controls the drive circuit 100, the interface circuit 104, and the motor drive circuit 105.

The operation of the conventional image reading apparatus configured as described above will be described below. First, when an image reading is instructed from an external device (not shown) such as a host computer, the CPU 106 drives the motor 12 to drive the carriage 7 via the carriage driving means 8 in any direction of the document sub-scanning direction A. , Performs an initial operation of moving the document 1 to the reading start position. After the initial operation is completed, the CPU 106 turns on the light source 2 and starts reading the image data of the original 1.
At this time, the light flux emitted to the original by the light source 2 is transmitted through the original glass 6 and guided to the original 1 after the aperture member 5 restricts the extra light except for the reading line of the original in the main scanning direction. The light flux guided to the document 1 is reflected in proportion to the reflectance of the document of each part, that is, the lightness which is the degree of brightness, and is then condensed by the lens 3 to be received by the image sensor 4 (not shown in the figure). ) And focus. In the light receiving portion of the image sensor 4, light receiving elements are arranged over one line or a plurality of lines in the main scanning direction of the document.

In this way, the image information for one line of the main scanning of the document 1 of interest is guided to the corresponding light receiving element on the image sensor 4, and the reflected light of the document at the portion corresponding to the pixel position of the light receiving element. Is received, and a charge proportional to its brightness is accumulated. This accumulated charge is the scanning start signal HSYNC.
During the period, a voltage proportional to the amount of accumulated charge appears in each pixel as an image signal output of the pixel corresponding to each light receiving element.
The voltage appearing in each pixel is sequentially output as an image signal output in the pixel arrangement order in synchronization with the scanning clock VCLK by the next HSYNC signal.

The image signal thus output from the image sensor 4 is amplified to a sufficient level by the amplifier 101 and then converted into digital value image data quantized by the next A / D converter 102. Then, the shading correction circuit 103 normalizes and corrects the image signal output variation in the main scanning direction, that is, the shading distortion caused by the nonuniformity of the irradiation light of the light source, the sensitivity variation of each pixel of the image sensor 4, and the like. The data is output. The image data whose shading distortion has been corrected is sequentially output to an external device (not shown) via the interface circuit 104. When the reading of the read image data for one line of the document is completed in this way, the carriage 7 moves to the next reading line, and the image data of the next line is sequentially read as the line of interest.

In this manner, each time image data for one line is obtained, the motor drive circuit 105 moves the carriage 7 through the drive means 8 by a moving distance corresponding to one line, thereby two-dimensionally moving. The image data of the original document is read in a plane.

The flare caused by the secondary light source generated when the light beam from the light source 2 is applied to a wide area of the original will be described. FIG. 11 is an explanatory view of generation of a secondary light source and flare due to a difference between conventional documents, FIG. 12 is a view showing an illumination optical system not using the aperture member and a document surface illuminance distribution in the sub-scanning direction, and FIG. 13 is the same. FIG. 13 is a diagram showing an illumination optical system provided with an aperture member and a document surface illuminance distribution in the sub-scanning direction, and FIG. 13 is a diagram for explaining the shape of the aperture member.

In FIG. 11, in the originals m and n in which the white part and the black part respectively have the same lightness k1 and k2, m
Indicates a black block pattern printed on a white part document, and n indicates a document on which a white block pattern is printed on a black part document. Here, since the brightness of the white part and the black part of the document m and the document n are the same, the high-level output voltage H corresponding to the white part reading of the image reading signal output of each document and the black part in the illustrated reading line of interest. The low level output voltage L corresponding to the reading should match.

However, in the illumination optical system shown in FIG. 12 in which the aperture member is not provided, when the light source irradiates a relatively wide area of the white background document, irregular reflection light from the document near the line of interest required for reading is generated. Then, the so-called secondary light source is generated in which the total illuminance increases more than the actual value by repeating the reflection with the light source or the near object a plurality of times again. Since this secondary light source has little influence in the case of a black-colored original document as is apparent from the above description, the white area read output H1 is the same for the original document m and the original document n described in FIG. ,
The output is higher than the white background reading output H2 of the black original document n, which causes whiteness at the lightness level. The whitening has a similar effect on a portion of the original having a lower brightness than a portion of the lightness, and as a flare, the read image quality of the original is greatly deteriorated.

Next, in the conventional illumination optical system shown in FIG.
As a countermeasure against this flare, an aperture member 5 is provided to limit the luminous flux from the light source 2 other than the reading line of the original 1 to which attention is paid. FIG. 12 shows an illumination optical system without an aperture member, and FIG. 13 shows a conventional illumination optical system with an aperture member 5. As shown in FIG. 13, the aperture member 5 limits the luminous flux irradiating the original with the transparent portion 5a and the opaque portion 5b, and the extra luminous flux is absorbed by the opaque portion 5b. 1
On the other hand, by irradiating only the vicinity of the reading line of interest, the secondary light source between the light source 2, the document 1 and the near object is suppressed, and the flare is suppressed.

[0015]

However, in the above-described conventional configuration, as is clear from the comparison of the conventional examples of FIGS. 12 and 13, most of the light flux generated by the light source 2 is limited by the aperture member 5. The illumination efficiency with which the light source 2 illuminates the document 1 is significantly reduced. Further, since it is not possible to ideally control the luminous flux so as to irradiate only the vicinity of the line of interest of the document, it is impossible to completely suppress the generation of the secondary light source. It was insufficient.

In view of the above-mentioned problems, the present invention suppresses the deterioration of the read image quality due to the variation in the brightness of the document caused by the flare caused by the generation of the secondary light source on the document, and
It is an object of the present invention to provide an image reading device capable of performing high-reproducibility image data reading by improving the S / N of image data of a read document.

[0017]

In order to solve the above-mentioned problems, the present invention provides a reading means composed of an image sensor having a light receiving pixel array in the document main scanning direction, a light source for irradiating a document having image data. What is claimed is: 1. An image reading apparatus, comprising: an optical unit that forms an image of reflected light from a document on the reading unit; and a drive unit that relatively moves the document and the reading unit in the sub-scanning direction. And a transparent opening and an opaque portion are provided in the light collecting means.

With the above structure, the illumination efficiency of the light source on the original surface can be significantly improved.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention comprises a reading means composed of an image sensor having a light receiving pixel array in the document main scanning direction, a light source for irradiating a document having image data, and a document source. An image reading apparatus having an optical means for forming an image of reflected light of the image on the reading means and a driving means for relatively moving the document and the reading means in the sub-scanning direction, the image reading device being parallel to the sub-scanning direction of the document. The image reading device is characterized in that it has a condensing means for concentrating the light flux from the light source in a certain fixed range, and that this condensing means is provided with a transparent opening and an opaque portion. With this configuration, it is possible to significantly improve the illumination efficiency of the light source on the original surface.

According to a second aspect of the present invention, there is provided an image reading device characterized in that a rod lens is used as the light converging means according to the first aspect.

According to a third aspect of the present invention, the transparent opening provided in the light collecting means according to the first or second aspect is formed in a slit shape parallel to the original sub-scanning direction.
Further, the width is variable from the central part to the peripheral part, and the width of the central part is formed so as to be effectively narrower than the width of the peripheral part.

With this configuration, it is possible to more precisely irradiate only the vicinity of the reading line of interest of the document, which adversely affects the reading of the document without lowering the illumination efficiency of the light source on the document surface. Flare caused by the generation of the secondary light source can be significantly suppressed.

Further, by making the width of the transparent opening in the peripheral portion wider than the width in the central portion with respect to the main scanning direction of the original, the effect of so-called shading correction for correcting the decrease in the light amount in the peripheral portion of the light source is condensed. Can be attached to the lens.

As described above, the occurrence of flare caused by the secondary light source of the original from the image data is largely suppressed, so that whitening at the lightness level is eliminated and the shape of the aperture of the condenser lens is devised. Thus, by simultaneously performing the shading correction of the light source, it is possible to suppress the S / N deterioration of the image data in the peripheral portion of the document due to the decrease in the light amount at both ends of the light source.

Therefore, the reading S / N is high irrespective of the type of the original, and the fluctuation of the reading brightness level can be suppressed, so that the image reading apparatus having a very high reading reproducibility can be realized.

(Embodiment 1) Next, Embodiment 1 of the present invention will be described with reference to the drawings. 1 is a block diagram of a mechanism system of an image reading apparatus according to Embodiment 1 of the present invention, and FIG. 2 is a block diagram of a circuit system of the image reading apparatus. 3 is an explanatory view of the shape of the condenser lens, and FIG.
FIG. 3 is a diagram showing the illumination optical system and the document surface illuminance distribution in the sub-scanning direction.

In FIG. 1, 1 is a document, 2 is a light source, 3 is a lens, 4 is a line image sensor such as a CCD, 6 is a document glass for holding a document formed of a transparent material, and 7 is a light source 2. , A carriage that holds the lens 3 and the image sensor 4 and is movable in the sub-scanning direction indicated by arrow A,
Reference numeral 8 denotes a carriage drive means for moving the carriage 7 in the sub-scanning direction of the document surface, which is composed of a drive pulley 9, a passive pulley 10, a drive wire 11, and a motor 12. Reference numeral 13 denotes a rod lens such as a cylindrical lens having an opaque portion 13a and a transparent opening portion 13b formed in the main scanning direction by printing or other method, and a light beam from the light source 2 is focused on the original 1 in the main scanning direction 1 line. It is a condensing lens that is limited to around the minute.

In FIG. 2, 100 is the image sensor 4.
Scan start signal HSYNC and scan clock signal VCL
An image sensor driving circuit that gives K, 101 is an amplifier that amplifies the image signal output from the image sensor 4 to an appropriate level, and 102 is an A / D that quantizes the image signal from the image sensor 4 and converts it into digital value image data. It is a converter. Reference numeral 103 denotes a shading correction circuit that normalizes and corrects image signal output variations in the main scanning direction, which are caused by unevenness of light emitted from the light source and variations in sensitivity of each pixel of the image sensor 4. Interface circuit for accumulating a predetermined amount of the image signal and outputting the same in synchronization with the instruction of an external device (not shown), 105 is a motor drive circuit for rotating the motor 12 at an arbitrary speed, 106 is a light source 2, an image sensor It is a CPU that controls the drive circuit 100, the interface circuit 4, and the motor drive circuit 105, and the circuit contents are the same as in the conventional example.

The operation of the image reading apparatus configured as described above will be described below. First, when an image reading is instructed from an external device (not shown) such as a host computer, the CPU 106 drives the motor 12 to drive the carriage 7 via the drive means 8 in any direction of the document sub-scanning direction A. , Perform an initial operation of moving to the reading start position. When the initial operation is completed, the CPU 106 then turns on the light source 2 and starts reading the image data of the original 1 on which the carriage 7 is placed on the original glass 6 by the carriage driving means 8. At this time, the light flux applied to the original by the light source 2 is condensed by the condenser lens 13 in the vicinity of the reading line in the main scanning direction of interest of the original, and after the extra light is limited, it passes through the original glass 6. Guided to manuscript 1.

The light beam guided to the original 1 is reflected in proportion to the reflectance of each part of the original, that is, the brightness, which is the degree of brightness, and then is condensed by the lens 3 to be received by the image sensor 4 (in the drawing, a light receiving portion (in the figure). (Omitted) and focus.
The light receiving portion of the image sensor 4 has a 1 in the main scanning direction of the document.
The light receiving elements are arrayed over a line or a plurality of lines.

As described above, the image information of one line of the main scanning of the original 1 which is noticed is guided to the corresponding light receiving element on the image sensor 4, and the reflected light of the original of the portion corresponding to the pixel position of the light receiving element is reflected. Light is received, and an electric charge proportional to its brightness is accumulated. This accumulated charge is the scanning start signal HSYNC.
During the period, a voltage proportional to the amount of accumulated charge appears in each pixel as an image signal output of the pixel corresponding to each light receiving element.
The voltage appearing in each pixel is sequentially output as an image signal output in the pixel arrangement order in synchronization with the scanning clock VCLK by the next HSYNC signal.

The image signal thus output from the image sensor 4 is amplified by the amplifier 101 to a sufficient level and then converted into image data of digital value quantized by the next A / D converter 102. In the shading correction circuit 103, image data output variation in the main scanning direction, that is, image data in which shading distortion is normalized and corrected, which is caused by unevenness of light emitted from the light source and variation in sensitivity of each pixel of the image sensor 4, etc. Is output.

The image data whose shading distortion has been corrected is sequentially output to an external device (not shown) via the interface circuit 104. When the reading of the read image data for one line of the document is completed in this manner, the carriage 5 moves to the next reading line, and the image data of the next line is sequentially read as the target line.

In this way, each time image data for one line is obtained, the motor drive circuit 105 moves the carriage 7 through the drive means 8 by a moving distance corresponding to one line, thereby It is configured to read image data of a three-dimensional original in a plane.

Here, the shape of the condenser lens 13 is shown in FIG. 3, and the effect thereof will be described below. Condensing lens 13
Uses a semi-circular or round rod-shaped cylindrical lens or rod lens, and the opaque portion 13a is formed on the condenser lens 13 except for the central portion by black paint or black printing or coloring of the material. The transparent aperture 13 is provided near the center of the condenser lens 13
b is formed in a slit shape. Therefore, in the illumination optical system shown in FIG. 4, the luminous flux from the light source 2 is focused only by the cylindrical lens near the reading line of interest on the document surface, so that the effective document illuminance can be greatly improved. Further, the light flux to the area other than the reading line of interest of the original document 1 is significantly reduced by the condenser lens 13, but the skirt of the illuminance on the original document is slightly widened due to the aberration or the like caused by the incompleteness of the lens. Since this unnecessary light flux is absorbed by the opaque portion 13a as shown by the dotted line a in FIG. 4, it is possible to precisely illuminate only the vicinity of the reading line of interest of the document 1. Further, even when a part of the light flux from the light source 2 acts as a secondary light source, the opaque portion 13a absorbs it, so that the influence of flare due to the generation of the secondary light source can be significantly suppressed.

(Second Embodiment) Next, an image reading apparatus according to a second embodiment of the present invention will be described. FIG. 5 is a diagram showing the shape of a condenser lens that also serves as shading correction according to the second embodiment of the present invention. Reference numeral 14 is a condenser lens, 14a is an opaque portion formed on the condenser lens 14, and 14b is an opaque portion. It is a transparent opening. Since the mechanical system and the circuit system are the same as those in the first embodiment, the description thereof will be omitted.

Here, the condenser lens 14 is the same as in the first embodiment.
A semi-circular or round rod-shaped cylindrical lens or rod lens is used in the same manner as above.
An opaque portion 14a is provided except for the vicinity of the central portion by black paint, black printing, or coloring of the material, so that the transparent opening 1 is provided near the central portion of the condenser lens 14.
4b is formed in a slit shape.

As shown in FIG. 5, the transparent opening 14b is formed such that the central portion is narrow and the width is gradually increased over the peripheral portion, and the luminous flux from the light source 2 is directed to the original 1 in the main scanning direction of interest. It is formed so as to be limited to the vicinity of one line and to vary the illuminance of the document surface in the document main scanning direction.

Next, FIGS. 6 (a) and 6 (b) are illuminance distribution charts of the illumination optical system according to Embodiment 2 of the present invention and the document surface in the document main scanning direction, and FIGS. 7 (a) and 7 (b) are conventional. 3 is an illumination optical system and an illuminance distribution diagram of a document surface with respect to a document main scanning direction.

When a linear light source such as a fluorescent lamp is used as the light source 2,
Since the light quantity at both ends of the light source is lower than that near the central portion of the light source, the illuminance at the central portion in the document scanning main scanning direction is generally high and the illuminance at the peripheral portions is low, resulting in an illuminance distribution as shown in FIG. .

In the second embodiment, the transparent opening formed in the shape of a slit on the condenser lens 14 is formed such that the central portion is narrow and the peripheral portion is gradually widened. Therefore, the opaque portion is formed. In the peripheral portion, the ineffective component of the light source absorbed by 14a is effectively used for illuminating the document surface. Therefore, the illuminance distribution in the document main scanning direction can be made substantially uniform by compensating for the reduction in the illuminance of the document surface in the peripheral portion of the document while the light amount at both ends of the light source 2 is reduced, while suppressing flare.
At the same time, shading correction of the light source 2 can be performed.

Although the image reading of a black and white original is described in the above embodiment, the present invention can also be used for reading a color original. Although the opaque portion is provided on the document side of the condenser lens, it may be provided on the light source side or the material itself may be colored. Needless to say, the slit shape is not limited to the shape of the present embodiment as long as it has the same effect.

[0043]

As described above, according to the present invention, as shown in the first embodiment, a rod lens represented by a cylindrical lens is used as a condensing lens, and the luminous flux of the light source is near the reading line of interest of the original. By condensing the light, it is possible to suppress flare due to the generation of the secondary light source generated by irradiating the document over a wide range, and it is possible to remarkably improve the illumination efficiency of the light source onto the document surface. The S / N can be greatly improved.

By forming an opaque portion and a transparent opening on the condenser lens by printing or another method, it becomes possible to precisely irradiate only the vicinity of the reading line of interest of the original document, and It has become possible to further significantly suppress the occurrence of flare without lowering the illumination efficiency on the document surface.

In addition, as in the second embodiment, the transparent opening of the condenser lens is designed such that the peripheral portion is wider than the central portion so that the shading correction is performed at the same time. It is possible to provide an image reading apparatus having extremely high image reproducibility over the entire image surface regardless of the type of the original, such as suppressing the S / N reduction due to the decrease in the light amount of
The practical effect is great.

[Brief description of the drawings]

FIG. 1 is a block diagram of a mechanism system of an image reading apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a circuit system of the image reading apparatus according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a shape of a condenser lens according to the first embodiment of the present invention.

FIG. 4 is a diagram showing an illumination optical system according to Embodiment 1 of the present invention and a document surface illuminance distribution in a sub-scanning direction.

FIG. 5 is a diagram showing the shape of a condenser lens that also serves as shading correction according to the second embodiment of the present invention.

FIG. 6 is an illumination optical system according to a second embodiment of the present invention and an illuminance distribution diagram of a document surface with respect to a document main scanning direction.

FIG. 7 is a conventional illuminating optical system and an illuminance distribution diagram of a document surface in a document main scanning direction.

FIG. 8 is a block diagram of a mechanical system of a conventional image reading device.

FIG. 9 is a block diagram of a circuit system of a conventional image reading device.

FIG. 10 is an explanatory diagram of the generation of a secondary light source and flare due to the difference in the conventional document.

FIG. 11 is a diagram showing an illumination optical system that does not use a conventional aperture member and a document surface illuminance distribution in the sub-scanning direction.

FIG. 12 is a diagram showing an illumination optical system provided with a conventional aperture member and a document surface illuminance distribution in the sub-scanning direction.

FIG. 13 is a diagram illustrating the shape of a conventional aperture member.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Original 2 Light source 3 Lens 4 Image sensor 7 Carriage 8 Carriage driving means 13, 14 Condensing lens 13a, 14a Opaque part 13b, 14b Transparent opening 100 Image sensor drive circuit 101 Amplifier 102 A / D converter 103 Shading correction circuit 104 interface circuit 105 motor drive circuit 106 CPU

Claims (3)

[Claims] 1. A reading means comprising an image sensor having a light-receiving pixel array in the main scanning direction of the original, a light source for illuminating the original having image data, and an optical means for forming reflected light from the original on the reading means. An image reading apparatus having a driving unit that relatively moves the document and the reading unit in the sub-scanning direction, the light-collecting unit condensing a light flux from a light source in a certain range parallel to the sub-scanning direction of the document. An image reading apparatus having means, and a transparent opening and an opaque portion being provided in the light collecting means. 2. The image reading apparatus according to claim 1, wherein a rod lens is used as the condensing means. 3. The transparent opening provided in the condensing means is formed in a slit shape parallel to the original sub-scanning direction,
3. The image reading device according to claim 1, wherein the width is variable from the central portion to the peripheral portion, and the width of the central portion is effectively narrower than the width of the peripheral portion. apparatus.