JP3256285B2 - Output correction device for contact image sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an output correction device for a contact type image sensor, and more particularly to an improvement of a contact type image sensor capable of correcting dark output and white output and capable of reading high quality images.

[0002]

2. Description of the Related Art Image reading means using a contact type image sensor has the advantage that no complicated adjustment work is required, and the structure is compact and the structure can be simplified as compared with a reduction optical system using a lens and a CCD. However, in order to use it as reading means as in the case of the reduction optical system, it is necessary to correct the unevenness of the photoelectric conversion characteristics of each light receiving element and the non-flatness of the white output waveform caused by the bias of the light emission amount of the light source to correct the image deterioration. Need to be suppressed. Conventionally, image processing techniques have been used as a measure to improve this point. However, there is a problem that signal processing becomes complicated, and therefore, development of an output correction method using a simple method has been desired. In order to obtain high-quality image information when reading a photographic document having gradation, it is necessary to correct not only the white output but also the dark output of each pixel.

A contact image sensor receives reflected light obtained by irradiating light from a light source onto a document surface with a light receiving element and performs photoelectric conversion. The contents of the image are read in a state where the image is displayed. Since the depth of focus is extremely short and it is necessary to pass the document surface conveyed at the time of reading through a uniform position from the image sensor, it is necessary to arrange a member for pressing the document on the scan line in order to prevent fluttering of the conveyed document. Occurs. For this reason, conventionally, a method has been adopted in which a platen roller which has been subjected to white processing and serves as a white reference member separate from the roller is also used as a white reference for sensitivity correction (JP-A-3-94568).

However, while the contact type image sensor is driven, its scan line is always in close contact with the platen roller and the member for pressing the original, so that the contact portion with the scan line is used for sensitivity correction as described above. If white processing has been performed, information necessary for dark output correction cannot be collected. In addition, there is a method in which data read with the light source built in the sensor unit turned off is used as dark output correction data. However, according to this method, light emitted from the light source is reflected in an unexpected direction and received. Since the correction data does not take into account the effects of stray light arriving at the section and the effects of noise generated when the light source is turned on, the dark output correction is not accurate, and streak unevenness and lines in the black part of the reproduced image are not obtained. Inconveniences such as breakage are likely to occur, making it difficult to obtain fine image information. Or also
There is also a correction method that uses the dummy pixel output as a substitute for the dark output. However, since the output level differs for each pixel, it cannot be said that this is a realistic correction method. further,
It can be said that sensitivity correction is sufficient if the read image information is simply binarized. However, when reading an image having a gradation such as a photographic image, the darkness generated inside the sensor is sufficient. Unless correction is performed in consideration of output variations, high image quality cannot be achieved. in this way,
In order to read an image using a contact image sensor and obtain high-quality image information, it is necessary to simultaneously perform not only sensitivity correction but also dark output correction after removing a stray light component generated when the light source is turned on.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a contact type image sensor capable of simultaneously obtaining the sensitivity correction of the contact type image sensor and the white reference and black reference outputs required for dark output correction. It is intended to provide an output correction device.

[0006]

In order to achieve the above object, a first invention of the present application comprises a light source disposed in a casing, and a light source disposed on an upper surface of the casing for receiving document information light emitted from the light source and reflected on a document surface. In the contact type image sensor including the light receiving element array, the contact type image sensor is configured to be linearly movable back and forth along the document transport direction and is always elastically biased toward the transport direction upstream side, And it can be moved downstream in the transport direction by the rotation of a platen roller contacting the upper surface of the casing with a white outer peripheral surface,
In a state before the start of conveyance in which the platen roller is stopped, the image sensor is positioned on the upstream side in the conveyance direction by the elastic urging force, and the light receiving element row is positioned on the upstream side of the platen roller. When the platen roller rotates against the elastic urging force and presses the image sensor downstream in the transport direction, the element row faces the outer peripheral surface of the platen roller, and the light receiving element row is When the output of the light receiving element when the light source is turned on is located on the upstream side of the roller, the output of the light receiving element is used as a black reference to perform dark output correction, and when the light receiving element row faces the white outer peripheral surface of the platen roller. The sensitivity of the light receiving element is corrected using the output of the light receiving element as a white reference.

According to a second aspect of the present invention, there is provided a close contact comprising a light source disposed in a casing, and a light receiving element array disposed on an upper surface of the casing to receive original information light emitted from the light source and reflected on an original surface. In the image sensor, the contact image sensor is urged to elastically press the light receiving element array on the upper surface of the casing against the white outer peripheral surface of the platen roller for document conveyance, and the rotation axis of the platen roller is A black reference member is rotatably supported, and the black reference member has a black reference portion at a lower end thereof interposed between the outer peripheral surface of the platen roller and the light receiving element row to face the light receiving element row. When the platen roller rotates in the document feeding direction, the black reference portion rotates along with the platen roller and retreats from a position facing the light receiving element row, and the light receiving element row is in contact with the black reference section. versus When the light source is turned on, the output of the light receiving element when the light source is turned on is used as the black reference to perform dark output correction, and when the light receiving element row faces the white outer peripheral surface of the platen roller, the output of the light receiving element is used as the white reference. In this case, the sensitivity of the light receiving element is corrected.

According to a third aspect of the present invention, in the black reference member, a white reference portion and a black reference portion are arranged in a band shape in parallel with the light receiving element row at the lower end of the black reference member. The dark output correction is performed using the output of the light receiving element when the light source is turned on when facing the surface as a black reference, and the output of the light receiving element when the light receiving element row faces the white outer peripheral surface of the platen roller. The sensitivity of the light receiving element is corrected as a reference.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1A is a perspective view showing a schematic configuration of an output correction device of a document reading apparatus using a contact type image sensor according to the present invention, and FIGS. 1B to 1D are diagrams showing a reading procedure. As shown in FIG. 1 (a), the contact type image sensor 1 reads an image on the lower surface of a document in a process of transporting the document 3 in a direction indicated by an arrow while sandwiching the document 3 with a platen roller 2 having a white surface. It is. Output correction device A for image sensor 1
Moves the image sensor 1 from the upstream position shown in (b) to (c)
The support surface 4 is so arranged that it can advance and retreat to the downstream position shown in (d).
The image sensor 1 is pressed to the upstream side at times other than the time of document reading by a spring 6 that is supported above and is disposed between the side wall 5 and the downstream side surface of the image sensor 1. Reference numeral 7 denotes a stopper protruding from the side wall 5, which limits the moving distance of the image sensor 1 to the downstream side.

The image sensor 1 has a hollow casing 8 supported by a support surface 4 or guide means (not shown) so as to be able to move back and forth in the left-right direction of the drawing, and a direction perpendicular to the plane of the drawing at a position closer to the upstream side of the upper surface of the casing 8. It has a scan line (light-receiving element array) 9 composed of light-receiving elements linearly arranged in a direction parallel to the axial direction of the platen roller, and a light source 10 disposed immediately below the scan line 9. At the time of non-reading shown in FIG. 1 (b), the scan line 9 is maintained in a state of being retracted upstream from the contact line 2a between the platen roller 2 and the upper surface of the casing by urging the casing 8 by the spring 6 to the upstream side. . When the driving of the sensor is started in the state (b), the light source 10 is first turned on, and in this lighting state, the light receiving element forming the scan line 9 outputs the dark output _Vb including the stray light component, the noise generated at the time of driving, and the like. obtain.
Subsequently, when the platen roller 2 starts rotating in the direction of the arrow in FIG. 1C, the image sensor 1 as a whole moves downstream against the spring 6 due to the frictional resistance of the roller 2 surface. The scan line 9 is the contact line 2a
Is reached, the stopper 7 hits the sensor 1 and stops so that the sensor 1 does not move further downstream. By reading the reflected light from the white portion of the platen roller surface (the white reference portion for nonuniformity correction with white wave) at the scan line 9 in this state, obtaining a white reference output V _W for sensitivity correction. At this time, the document 3 has reached the position immediately near the platen roller.

Subsequently, when the platen roller 2 continues to rotate in the same direction, the original 3 enters the contact line 2a between the roller 2 and the upper surface of the casing as shown in FIG. It is photoelectrically converted by the light receiving element to obtain (a) black reference obtained in (b) the output V _b, respectively dark output correction by the white reference output V _W, image information by performing a sensitivity correction.

FIG. 2 shows a modification of the first embodiment, in which a side wall 15 is provided on the upstream side of the image sensor 1 and a stopper 15a which protrudes from the side wall 15 to the downstream side and regulates the range of movement of the sensor 1 on the upstream side. Further, the sensor 1 is characterized in that the sensor 1 is always pulled to the upstream side by a tension spring 6a extending from the side wall 15. In this variation, FIG.
The light source 10 is turned on in the state shown in FIG. 3 to obtain a dark output _Vb including a stray light component, noise generated during driving, and the like.
Is rotated clockwise to move the sensor 1 downstream against the spring 6a, so that the scan line 9 becomes the contact line 2
At time point a, the stopper 7 stops the sensor 1.
By reading the reflected light from the white platen roller surface at scan line 9 in this state, obtaining a white reference V _W for sensitivity correction. Finally, the source light reflected by the document surface in the same manner as FIG. 1 (d) and photoelectrically converted by the light receiving element, previously obtained black reference output V _b, sequentially dark output correction by the white reference output V _W, the sensitivity correction To obtain high quality image information.

FIGS. 3 (a) and 3 (c) are a perspective view and a front view, respectively, showing a schematic configuration of an output correction device for a contact type image sensor according to a second embodiment of the present invention. Is urged vertically upward by a spring 20 on a support surface, and a platen roller 2 is disposed close to the upper surface thereof. A black reference member 22 having a shape as shown in the figure is rotatably supported on a rotating shaft 21 of the platen roller 2 and is pressed downward by a coil spring 23 from above. The image sensor 1 includes a light source 10 in a casing 8.
And has a scan line 9 on the upper surface. The black reference member 22 has a reference plate 25 having a length substantially equivalent to the axial length of the platen roller 2 and arms 26 extending from both ends of the reference plate 25. It has a blade shape that tapers as it goes, and the lower surface of the blade portion is blackened. The arm 26 has a configuration in which the shaft 21 of the platen roller 2 can be loosely fitted. An arm 26 is loosely fitted on the shaft 21 of the platen roller 2 to rotatably support the black reference member 22, so that the lower portion (black reference portion) 25 a of the reference plate 25 is positioned between the platen roller 2 and the upper surface of the image sensor 1. It is possible to advance and retreat during. When the spring 23 presses the black reference member 22 downward, the lower portion 25a projects between the roller 2 and the sensor 1 as shown in FIG. At this time, the lower part 2 of the reference plate 25
The inner side surface of the roller 5a contacts the surface of the roller 2, and when the roller 2 rotates counterclockwise, the roller 2 rotates with the roller 2 and retreats in the same direction against the spring 23.

When the image sensor 1 starts driving according to a reading start command from a control unit (not shown), the light source 10
Lights up, irradiates the black reference portion 25a of the black reference member 22 in the initial state of FIG. 3B, and receives the reflected light at this time by the light receiving element constituting the scan line 9 to obtain a result of photoelectric conversion. The obtained sensor output _Vb is used as a black reference output including stray light components, noise generated during driving, and the like.

FIGS. 4A, 4B and 4C are diagrams for explaining the operation of the embodiment shown in FIG. 3, in which the original 3 conveyed from the left side of FIG. When the platen roller 2 starts rotating in the direction indicated by the arrow, the black reference member 22 is pushed out in the counterclockwise direction by the frictional resistance between the roller surface and retracts, and the lower black surface 25a faces the scan line 9. When retracted from the position, a spring 20 that urges the lower surface of the sensor 1 upward presses the sensor 1 against the outer peripheral surface of the platen roller 2 that has been whitened. The sensor output V _W at this time is white reference output. Subsequently, as shown in FIG. 4B, the reflected light of the light source light illuminating the lower surface of the newly inserted document 3 between the scan line 9 and the roller 2 is read by the light receiving element, and the black reference output obtained in advance is obtained. obtaining a V _b, by the white reference output V _W, and the dark output correction, sensitivity correction respectively performed, the image information of high quality. Document 3 is scan line 9
The reading is completed by completely passing
When the rotation of the roller 2 is stopped, the black reference member 22 is again brought into contact with the roller 2 and the sensor 1 by the pressing force of the spring 23 as shown in FIG.
And returns to the initial state protruding between them.

FIG. 5 shows a modification of the embodiment shown in FIGS. 3 and 4, in which the torsion spring 2 is used instead of the coil spring 23.
The feature is that the black reference member 22 is elastically biased to the initial position in FIG. The torsion spring 23 ′ has one end locked to the image reading apparatus main body side and the other end provided on a side wall of the reference plate 25.
, The reference plate 25 is urged about the shaft 21 in the direction of the arrow.

FIG. 6 shows a third embodiment of the present invention.
A band-shaped white reference portion 30 and a black reference portion 31 having a width d in a direction parallel to the scan line 9 are formed on the lower outer surface of the reference plate 25 constituting the black reference member 22 of the embodiment of FIGS. The configuration in which they are arranged adjacent to each other is characteristic, and the other configuration is the same as that of the second embodiment. In this embodiment, in the initial state as shown in FIG. 3B, the black reference portion 31 is located between the scan line 9 and the platen roller 2. By turning on the light source in this state, the black reference portion 31 is turned on. The reflected light from 31 is photoelectrically converted by a light receiving element, and the output is set as a black reference output _Vb . When the platen roller is rotated together black reference plate 25 to start rotating, to obtain a white reference output V _W for the white reference portion 30 faces the scanning line 9. Subsequently, reading of the document image is performed when the document is conveyed between the platen roller and the scan lines, each reference output V _b was getting sensor output in advance, respectively dark output correction and sensitivity correction at V _W To obtain high quality image information.

[0018]

In the conventional contact-type image sensor, since the black reference data is taken in when the light source is turned off, it is not possible to perform correction in consideration of the influence of stray light and the effect of noise generated when the light source is turned on. As a result, stray light and noise generated at the time of document reading cannot be removed, resulting in deterioration of image quality. However, by collecting the black reference data while the light source is turned on as in the present invention, more realistic dark output correction becomes possible, and at the same time sensitivity correction becomes possible, and high-quality image information can be obtained. it can. Further, according to the second embodiment of the present invention, the black reference member is used in the black reference reading as well as the white reference reading, so that the dark output correction data and the sensitivity correction data are both more realistic. This makes it possible to obtain higher quality image information. In addition, since a platen roller to which dirt or ink from the document easily adheres is not used as a white reference and a special reference member is used, there is no danger that overcorrection will occur, and the sensitivity is reduced. Correction and dark output correction can be performed, and image quality can be improved.

[Brief description of the drawings]

FIG. 1A is a perspective view showing a schematic configuration of an output correction device of a document reading apparatus using a contact type image sensor according to a first embodiment of the present invention, and FIGS. 1B to 1D show reading procedures. FIG.

FIG. 2 is a diagram showing a modification of the embodiment of FIG. 1;

FIGS. 3 (a) and 3 (b) are a perspective view and a front view showing a schematic configuration of an output correction device for a contact type image sensor according to a second embodiment of the present invention.

4 (a), (b) and (c) are explanatory diagrams of the operation of the embodiment of FIG.

FIG. 5 is a configuration explanatory view of a modification of the second embodiment of the present invention.

FIG. 6 is a perspective view of a black reference member used in a third embodiment of the present invention.

[Explanation of symbols]

A output correction device, 1 contact image sensor, 2 platen roller, 2a contact line, 3 original, 5 side wall, 6 spring, 7 stopper, 8 casing, 9 scan line (light receiving element row), 10 light source, 20 spring,
21 rotating shaft, 22 black reference member, 23 spring, 25
Reference plate, 25a Lower part (black part), 26 arms, 30
White reference part, 31 Black reference part,

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-94568 (JP, A) JP-A-5-316300 (JP, A) JP-A-60-219535 (JP, A) JP-A-4- 185166 (JP, A) JP-A-63-37775 (JP, A) JP-A-3-99581 (JP, A) JP-A-4-223666 (JP, A) JP-A-5-82168 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H04N 1/401 H04N 1/19

Claims (3)

(57) [Claims] 1. A contact type image sensor comprising: a light source disposed in a casing; and a light receiving element array disposed on an upper surface of the casing to receive document information light emitted from the light source and reflected on a document surface. The contact type image sensor is configured to be linearly movable back and forth along the document transport direction, and is always elastically biased toward the transport direction upstream side,
In addition, the platen roller which is in contact with the upper surface of the casing at a white outer peripheral surface can be moved downstream in the conveyance direction by the rotation of the platen roller. While the light receiving element row is positioned on the upstream side of the platen roller by the force and is positioned upstream of the platen roller, the platen roller rotates against the elastic urging force to move the image sensor downstream in the direction of conveyance. When pressed to the side, the element array faces the outer peripheral surface of the platen roller, and the output of the light-receiving element when the light source is turned on when the light-receiving element array is located upstream of the platen roller. The dark output correction is performed with black as the black reference, and the sensitivity of the light receiving element is defined with the output of the light receiving element when the light receiving element row faces the white outer peripheral surface of the platen roller as the white reference. Output correction apparatus of the contact type image sensor, characterized in that the manner performed positively. 2. A contact type image sensor comprising: a light source disposed in a casing; and a light receiving element array disposed on an upper surface of the casing to receive document information light emitted from the light source and reflected on a document surface. The close contact type image sensor is urged so as to elastically press the light receiving element array on the upper surface of the casing against the white outer peripheral surface of the platen roller for document conveyance, and the black reference member rotates around the rotation axis of the platen roller. While being freely supported, the black reference member is elastically urged so that the black reference portion at the lower end thereof is interposed between the outer peripheral surface of the platen roller and the light receiving element row and faces the light receiving element row, When the platen roller rotates in the document conveying direction, the black reference portion follows the platen roller and retreats from a position facing the light receiving element row, and the black reference section is turned off when the light receiving element row faces the black reference portion. light source The dark output correction is performed using the output of the light receiving element when the light is turned on as a black reference, and the sensitivity correction of the light receiving element using the output of the light receiving element when the light receiving element row faces the white outer peripheral surface of the platen roller as a white reference. And an output correction device for a contact type image sensor. 3. A white reference portion and a black reference portion are arranged at the lower end of the black reference member in a band shape in parallel with the light receiving element row.
When the light receiving element array faces the black reference portion, dark output correction is performed using the output of the light receiving element when the light source is turned on as a black reference, and the light receiving element array faces the white outer peripheral surface of the platen roller. 3. The method according to claim 2, wherein the sensitivity of the light receiving element is corrected using the output of the light receiving element during the operation as a white reference.
An output correction device for a warm contact type image sensor as described in the above.