JP2892593B2 - Image input device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image input device using a solid-state linear image sensor, and more particularly, to an image input device that switches an optical system according to the content of an image to be input.

[0002]

2. Description of the Related Art Conventionally, as an image input device, there are a device for reading binary data from an image mainly composed of a line drawing and a device for reading multi-valued data from a continuous tone image such as a photograph.

In an apparatus for reading a binary image as in the former, an image of a scanning line area formed by an optical system is divided and projected onto a plurality of line sensors, and the scanning line area is shared by each line sensor. Read the image. And
By connecting pixels receiving the same document information at the boundary between adjacent line sensors, an image is read with high resolution and without dropouts or overlaps (Japanese Unexamined Patent Publication No.
No. 1752). It is to be noted that the image is divided into a plurality of line sensors and projected as described above, because an existing line sensor cannot obtain a long effective reading length with a high pixel density. This is because if the image is directly projected on the sensor, the image cannot be read at a high resolution.

In an apparatus for reading a multi-valued image as in the latter, since the image is continuous tone, if this image is divided and projected onto a plurality of line sensors and read as it is, the delicate There is a problem that a density difference that is not present in a document occurs in a detected image at a joint portion due to a difference in sensitivity. For this reason, a gray scale or the like that expresses the density stepwise or continuously on one tablet, such as a gray scale, is placed in advance at a position corresponding to the connection portion of the line sensor on the original surface, and the density is actually changed from low density to high density. , And electrical correction is performed so that the output level of the connected portions of the line sensors connected at each reading position becomes the same. However, since such a correction cannot achieve a complete connection process, when reading a multi-valued image, an original image is usually read by reducing and projecting it onto a single line sensor.

[0005]

As described above, the required specifications are different between the image input device for a binary image and the image input device for a multi-valued image, and the reading method is essentially corresponding to this. When a multi-valued image is read by an image input device for a binary image, there is a problem that a discontinuous portion is easily generated at a connection portion of a CCD. There is a problem that the resolution is reduced when reading. That is, there is a problem that both the binary image and the multi-valued image cannot be read with high quality by the same image input device.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image input device capable of reading a binary image or a multi-value image with high quality using a single device.

[0007]

According to a first aspect of the present invention, there is provided an image input apparatus for reading an image of a document while relatively moving the document and an imaging unit. An image capturing unit configured to form a plurality of solid-state linear image sensors and form an image of a document at a first magnification when reading a binary image, and to project the divided image onto the plurality of solid-state linear image sensors; And an optical system that forms an image of a document at a second magnification lower than the first magnification when reading the original and projects the image on any one of the plurality of solid-state linear image sensors. It is characterized by the following.

According to a second aspect of the present invention, in the image input apparatus, the optical system changes the magnification of the image of the original between the first and second magnifications and forms an image. Image dividing means for dividing an image of the original at the first magnification from an optical system and projecting the divided images onto the plurality of solid-state linear image sensors.

According to a third aspect of the present invention, in the image input apparatus, the variable power optical system is capable of moving back and forth on the optical axis of the variable power optical system, and when the variable power optical system is arranged on the optical axis, the image of the document is converted. A first lens that forms an image at the first magnification, and a second lens that is capable of moving back and forth on the optical axis and forms an image of a document at the second magnification when arranged on the optical axis And lens driving means for alternately moving the first and second lenses on and off the optical axis.

The image input apparatus according to a fourth aspect is characterized in that the variable power optical system has a zoom lens.

The image input apparatus according to a fifth aspect is characterized in that the variable power optical system has a varifocal lens.

According to a sixth aspect of the present invention, in the image input apparatus, the variable power optical system includes an imaging lens disposed on an optical axis of the variable power optical system, and a conversion lens capable of moving back and forth on the optical axis. Lens driving means for moving the conversion lens forward and backward on the optical axis.

The image input device according to a seventh aspect is characterized in that the image dividing means is a mirror.

In one embodiment of the present invention, one of the plurality of solid-state linear image sensors is arranged on the optical axis, and the image dividing means is configured to output the second linear image sensor from the variable power optical system. The image of the original at a magnification of 1 is divided and projected onto the plurality of solid-state linear image sensors individually, and the image of the original at the second magnification from the variable power optical system is arranged on the optical axis. Projected on a solid-state linear image sensor.

[0015]

In the image input device according to the first aspect, the image pickup unit includes:
When reading a binary image, an image of the document is formed at a first magnification and divided and projected on the plurality of solid-state linear image sensors. Since an optical system for forming an image at a second magnification lower than the magnification and projecting the image on any one of the plurality of solid-state linear image sensors is provided, reading of a binary image mainly including a line drawing is performed. And high resolution can be obtained, and it is possible to eliminate the bridging process in which it is difficult to obtain sufficient accuracy when reading a multi-valued image mainly composed of a continuous tone image. Even high-quality images can be read.

Further, in the image input apparatus according to the present invention, the optical system includes a variable-magnification optical system that forms an image of a document by changing the magnification between the first and second magnifications. Image splitting means for splitting the image of the original at the first magnification from the optical system and individually projecting the split image on the plurality of solid-state linear image sensors. Even multi-valued images can be read with high quality.

According to a third aspect of the present invention, in the image input apparatus, the variable power optical system is capable of moving back and forth on the optical axis of the variable power optical system, and is configured to copy an image of a document when the variable power optical system is disposed on the optical axis. A first lens that forms an image at the first magnification, and a second lens that is capable of moving back and forth on the optical axis and forms an image of a document at the second magnification when arranged on the optical axis And a lens driving means for alternately moving the first and second lenses on and off the optical axis, so that it is possible to read a binary image or a multi-valued image with high quality using a device having a simple structure. it can.

Further, in the image input apparatus according to the fourth aspect, since the variable power optical system has a zoom lens, a single optical system can read a binary image or a multi-valued image with high quality.

Further, in the image input apparatus according to the fifth aspect, since the variable power optical system has a varifocal lens, a single optical system can read a binary image or a multivalued image with high quality.

According to a sixth aspect of the present invention, in the image input apparatus, the variable power optical system is disposed on an optical axis of the variable power optical system, and the image forming lens is disposed on the optical axis so as to be able to advance and retreat. Since it has a conversion lens and lens driving means for moving the conversion lens forward and backward on the optical axis, it is possible to read a binary image or a multi-valued image with high quality using a device having a simple structure.

In the image input device according to the present invention, since the image dividing means is a mirror, it is possible to read a binary image or a multi-valued image with high quality by using a device having a simple structure.

Further, in the image input apparatus according to the present invention, any one of the plurality of solid-state linear image sensors is disposed on the optical axis, and the image dividing means is configured to output the second linear image sensor from the variable power optical system. The image of the original at a magnification of 1 is divided and projected onto the plurality of solid-state linear image sensors individually, and the image of the original at the second magnification from the variable power optical system is arranged on the optical axis. Since the image is projected on the solid-state linear image sensor, a binary image or a multi-valued image can be read with high quality using a device having a simple structure.

[0023]

FIG. 1 is a perspective view showing a main part of an image input apparatus according to a first embodiment. FIG. 1A shows a state of an optical system when a binary image mainly composed of a line image is read,
FIG. 1B shows the state of the optical system when reading a multivalued image mainly composed of a continuous tone image.

The original 2 is relatively moved in the AB direction with respect to the imaging unit 3 by a sub-scanning mechanism not shown.
The image light from the linear scanning area 2 a having a length corresponding to the effective document width of the document 2 is appropriately reduced / divided by the optical system 4 of the imaging unit 3 and projected onto the sensor unit 6 of the imaging unit 3. You.

The optical system 4 includes first and second reduction projection lenses 14 and 24. Each reduction projection lens 14, 24
Is the optical axis OA of the optical system 4 by the lens driving device 34.
Move up and down alternately. That is, when reading a binary image mainly composed of a line image from the original 2, the first reduction projection lens 14 is arranged on the optical axis OA, and the scanning area 2 of the original 2 is scanned.
a image at a first magnification m and the sensor unit 6
CCD1 which is three linear image sensors constituting
6, 26, and 36 (see FIG. 1A). When reading a multi-valued image mainly composed of a continuous tone image from the document 2, the second reduction projection lens 24 is arranged on the optical axis OA, and the image of the scanning area 2a of the document 2 is read.
CCDs 16, 26, and 36 which form an image at a second magnification m 'lower than the first magnification m and constitute the sensor unit 6
Of the central CCD 16 arranged on the optical axis OA
(See FIG. 1B).

In this embodiment, the first and second magnifications m and m 'are both reduction magnifications (that is, m <1, m').
<1: However, m ′ <m). Therefore, the first (reduction) magnification m is relatively higher than the second (reduction) magnification m ′, and conversely, the second (reduction) magnification m ′ is the first (reduction) magnification. The magnification is lower than m. Therefore, in the following description, these are generally referred to as “relatively high magnification” and “relatively low magnification”, respectively, and images obtained from the first and second reduction projection lenses 14 and 24 are referred to as “relatively high magnification”, respectively. They are referred to as "high magnification images" and "relatively low magnification images".

The present invention is not limited to such a case. For example, the first magnification m is the same magnification (m = 1), and the second magnification m 'is the reduction magnification (m'<1). Such cases are also included.

On the other hand, the lens driving device 34 drives the first reduction projection lens 14 to rotate about a rotation axis RA1 which is parallel to the optical axis OA and is separated from the first reduction projection lens 14 by a predetermined distance. Is driven to rotate about a rotation axis RA2 which is parallel to the optical axis OA and is separated from the optical axis OA by a predetermined distance. As a result, each reduction projection lens 14, 24
The optical system 4 reciprocates between the image forming position on the optical axis OA and the retracted position retracted from the optical axis OA. At this time, the reduction projection lenses 14 and 24 are rotated in opposite directions by a gear mechanism including a plurality of gears (not shown). Therefore, each reduction projection lens 14, 24
Move forward and backward alternately on the optical axis OA.
When the reduction projection lens 14 is disposed at the image forming position on the optical axis OA, the second reduction projection lens 24 is disposed at the retracted position (see FIG. 1A), and the second reduction projection lens 24 is disposed.
Is located at the image forming position on the optical axis OA, the first reduction projection lens 14 is located at the retracted position (FIG. 1B).
reference).

The first or second reduction projection lens 1
Since the imaging magnifications 4 and 24 are different, the positions where they are arranged on the optical axis OA are also different. That is, in FIG. 1A, the magnification m of the first reduction projection lens 14 is
Corresponds substantially to (object distance a / image distance b), and FIG.
, The magnification m ′ of the second reduction projection lens 24 substantially corresponds to (object distance a ′ / image distance b ′).

On the optical axis OA, a dividing mirror 54 is arranged between the first or second reduction projection lens 14, 24 and the central CCD 16. This mirror 54 is provided with the first reduction projection lens 1 disposed at the image forming position.
The light flux of the relatively high-magnification image from 4 is divided into three and each CC
D16, 26, and 36, and at the same time, has a function of guiding the light flux of the image of relatively low magnification from the second reduction projection lens 24 disposed at the image forming position onto the central CCD 16.

Each of the CCDs 16, 2, 2
Numerals 6 and 36 have the same structure, and a light beam of a relatively high-magnification image from the first reduction projection lens 14 is divided into three and projected onto the linear light receiving area. Also, the central CC
The light flux of the image with relatively low magnification from the second reduction projection lens 24 is also projected onto the light receiving area D16 at one time.

The outputs of the CCDs 16, 26 and 36 are processed by a CCD drive circuit and a signal processing circuit (not shown). That is, when reading a binary image mainly composed of a line drawing, a pattern of a binary signal corresponding to a joint at an end of each of the CCDs 16, 26, and 36 is determined, and a position is determined so that these patterns match. The connection processing is performed on the image signal while compensating for the deviation. This allows each CCD
A one-dimensional binary image signal can be obtained in the same manner as when 16, 26, and 36 are arranged on a straight line without any break. When reading a multi-valued image mainly composed of a continuous tone image, a one-dimensional multi-valued image signal is obtained only from the central CCD 16.

In the first embodiment, a relatively high-magnification image from the first reduction projection lens 14 disposed at the image forming position is divided into three parts and projected onto the CCDs 16, 26, and 36. However, a relatively high-magnification image from the first reduction projection lens 14 can be divided and projected onto a large number of four or more CCDs.

FIG. 2 is a perspective view showing a main part of the image input apparatus of the second embodiment. FIG. 2A shows a state in which a binary image mainly composed of a line image is read, and FIG.
Indicates a state in which a multivalued image mainly composed of a continuous tone image is read. Note that the image input device of the second embodiment is the same as that of the first embodiment.
Since this embodiment is the same as the first embodiment except that a zoom lens is used by modifying the optical system 4 of the embodiment, common parts are denoted by the same reference numerals and description thereof is omitted.

The optical system 4 has a zoom lens 64.
The focal length of the zoom lens 64 is continuously changed between a relatively high magnification and a relatively low magnification by a lens driving device (not shown), and the optical axis O of the optical system 4 is changed.
Move back and forth on A. That is, when reading a binary image mainly composed of a line image from a document, the zoom lens 64 is used.
The original image is imaged at a relatively high magnification by increasing the magnification of
When reading a multi-valued image mainly composed of a continuous tone image from a document, the magnification of the zoom lens 64 is reduced and the image is transferred to the mirror 54 side (see FIG. 2A). By moving, the original image is formed at a relatively low magnification and projected on the CCD 16 (FIG. 2B).
reference).

In the second embodiment, the optical system 4 is composed of a zoom lens having a continuously changing focal length. However, a varifocal lens having a focal length of 2 or more and discontinuously changing is used. The optical system 4 can also be configured from

FIG. 3 is a perspective view showing a main part of the image input apparatus of the third embodiment. FIG. 3A shows a state in which a binary image mainly composed of a line image is read, and FIG.
Indicates a state in which a multivalued image mainly composed of a continuous tone image is read. The image input device of the third embodiment is the same as the first embodiment.
This is the same as the first embodiment except that the optical system 4 of the embodiment is modified and a conversion lens is used.

The optical system 4 includes a reduction projection lens 74 and a conversion lens 84. Reduction projection lens 74
Is an optical system 4 by a lens driving device (not shown).
Move back and forth on the optical axis OA. The conversion lens 84 is rotated by a lens driving device (not shown) around a rotation axis RA3 deviated from the optical axis OA in synchronism with the movement of the reduction projection lens 74, so that the conversion lens 84 is positioned on the optical axis OA of the optical system 4. Reciprocating (moving forward and backward) between the position (1) and the retracted position retracted from the optical axis OA. As a result, when reading a binary image mainly composed of a line image from a document, the conversion lens 84 is moved to the retracted position,
The reduction projection lens 74 is moved to the original side to form an image of the original at a relatively high magnification, and the divided images are projected on the CCDs 16, 26, and 36 (see FIG. 3A). When reading a multi-valued image mainly composed of a continuous tone image from a document, the conversion lens 84 is moved to a position on the optical axis, and the reduction projection lens 74 is moved to the mirror 54 to compare the document images. An image is formed at a very low magnification and projected onto the CCD 16 (see FIG. 3B).

[0039]

As described above, according to each of the image input devices according to the first to eighth aspects, an image input device that reads an image of a document while relatively moving the document and the imaging unit is provided. The image forming unit forms an image of a document at a first magnification when reading a binary image, divides and projects the image on the plurality of solid-state linear image sensors, and reads the document when reading a multi-valued image. Since an optical system for forming an image at a second magnification lower than the first magnification and projecting the image onto any one of the plurality of solid-state linear image sensors is provided, a single device is used. By using this method, a binary image or a multi-valued image can be read with high quality.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a first embodiment.

FIG. 2 is a perspective view showing a configuration of a second embodiment.

FIG. 3 is a perspective view showing a configuration of a third embodiment.

[Explanation of symbols]

 2 Document 3 Imaging unit 4 Optical system 6 Sensor unit 14 First reduction projection lens 16 CCD 24 Second reduction projection lens 26 CCD 36 CCD 64 Zoom lens 74 Reduction projection lens 84 Conversion lens

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-13060 (JP, A) JP-A-7-38714 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04N 1/04-1/207

Claims (8)

(57) [Claims] 1. An image input apparatus for reading an image of a document while relatively moving the document and an image pickup unit, wherein the image pickup unit includes a plurality of solid-state linear image sensors,
When reading a value image, an image of a document is formed at a first magnification and divided and projected on the plurality of solid-state linear image sensors. When reading a multi-valued image, the image of the document is converted to the first magnification. An optical system that forms an image at a lower second magnification and projects the image onto any one of the plurality of solid-state linear image sensors. 2. The variable magnification optical system according to claim 2, wherein the optical system is configured to change the size of the image of the document between the first and second magnifications to form an image, and the first magnification from the variable magnification optical system. 2. An image dividing means for dividing an image of an original and projecting the divided images on the plurality of solid-state linear image sensors.
The image input device according to the above. 3. The variable power optical system is capable of moving back and forth on the optical axis of the variable power optical system and forms an image of a document at the first magnification when arranged on the optical axis. A first lens, a second lens capable of moving back and forth on the optical axis and forming an image of a document at the second magnification when arranged on the optical axis, and the first and second lenses 3. An image input apparatus according to claim 2, further comprising a lens driving means for moving the lens unit alternately on and off the optical axis. 4. The image input device according to claim 2, wherein the variable power optical system has a zoom lens. 5. The image input device according to claim 2, wherein the variable power optical system has a varifocal lens. 6. The variable power optical system includes: an imaging lens disposed on an optical axis of the variable power optical system; a conversion lens capable of moving back and forth on the optical axis; 3. An image input apparatus according to claim 2, further comprising a lens driving means for moving forward and backward. 7. The image input device according to claim 2, wherein said image dividing means is a mirror. 8. One of the plurality of solid-state linear image sensors is arranged on the optical axis, and the image dividing means converts an image of the original at the first magnification from the variable power optical system. While dividing and projecting individually onto the plurality of solid-state linear image sensors, the image of the original at the second magnification from the variable power optical system is projected onto the solid-state linear image sensor arranged on the optical axis. 3. The image input device according to claim 2, wherein