JP5626722B2 - Image reading device - Google Patents

Description

  The present invention relates to an image reading apparatus that reads a document used in a scanner device, a copying machine, a facsimile, or the like, and relates to an improvement of a light source mechanism when an image is read by a photoelectric conversion sensor.

  In general, this type of image reading apparatus irradiates light from a light source onto an image reading surface such as a platen and guides reflected light or transmitted light from a document to a photoelectric conversion sensor for electrical reading. As a photoelectric conversion sensor, there are known a mechanism for reading an image in a plane sequence by an area sensor and a mechanism for reading an image in a line sequence by a line sensor. The present invention relates to a method of reading an image line-sequentially with a CCD line sensor.

  Conventionally, in a CCD line sensor, photoelectric conversion elements (pixels) of photodiodes are arranged in a line shape, and charges accumulated in the pixels are transferred to the outside by a CCD register. In the color sensor structure, for each color component, photoelectric conversion element rows are arranged in the sub-scanning direction, for example, in the order of R row G row B, and a horizontal shift register (output transfer path) that transfers charges to the element rows in the main scanning direction. And a vertical shift register (sub-scanning direction transfer path) for transferring charges to the output transfer path.

  In this case, the simplest structure may be a method of arranging an R shift register next to the R element row, then arranging the G element row and the G shift register in this order. However, when the element rows and the shift registers are arranged in the order of RGB, the reading lines are displaced in the farthest photoelectric conversion element rows of the R row and the B row. This is output as image blur or color misregistration and affects reading accuracy.

  Therefore, for example, element rows are arranged in the order of RGB, an R shift register next to the R row and a G shift register and a B shift register are arranged next to the B row located outside the GB row, and each pixel and the shift register are shifted to the shift gate. It is known to connect with. In this case, the sub-scanning direction transfer path for transferring the charges of the G row and the B row to the horizontal shift register is arranged so as to cross the element row.

  On the other hand, the image reading surface is constituted by a flat bed platen or a slit exposure platen. The former reads a placed original sheet, and the latter reads a running original moving at a predetermined speed. The platen is irradiated with linear light from a light source lamp, and reflected light or transmitted light from the document surface is condensed on a CCD line sensor.

  As the light source lamp, a fluorescent lamp (cold cathode tube), a xenon lamp, and the like are known, and recently, an LED (Light Emitting Diode) is used. This LED is known to have an array structure in which light-emitting elements are arranged in a line and a structure in which light from a point-like LED light-emitting element is converted into linear light by a rod-shaped light guide and irradiated.

  Therefore, conventionally, during image reading, the reading surface is continuously irradiated with light from the light source, and charge accumulation and external transfer are repeated by the line sensor. The charge accumulation and transfer cycle is controlled by a read clock.

  As described above, in the conventional reading structure in which light is continuously emitted from the light source lamp when reading an image with the CCD line sensor, the following problems occur due to the structure of the CCD line sensor. As described above, a plurality of photoelectric conversion element arrays for each color component are arranged in the sub-scanning direction, and the charge accumulated in each pixel is output to the outside through the sub-scanning direction transfer path through the output transfer path. In a structure where the transfer path crosses the photoelectric conversion element array (cross array), color misregistration becomes a problem.

  That is, for example, when transferring the charge of the G element array to the output transfer path in the sub-scanning direction transfer path, if the B photoelectric conversion portion is irradiated with light when passing through the B element array, The B component charge is superimposed on the charge. For this reason, if the charge of the B element row of another color component is mixed during the transfer of the charge of the G element row, an accurate output of the color component cannot be obtained. Conventionally, such a color mixture problem is unavoidable due to the structure of the color sensor.

  On the other hand, in order to avoid such color mixture, for example, a G color transfer path is arranged next to the G element row and then a G color transfer path is arranged next to the B element row. Since the interval between the respective reading lines becomes wider, the image reading position is displaced, which causes color misregistration.

  In view of this, the present inventor has come up with the idea that in a line sensor structure in which a plurality of photoelectric conversion element arrays are arranged in the sub-scanning direction, when the charge accumulated in the photodiode is externally transferred and output, the light source is turned off or light is blocked by a shutter or the like. It was. As a result, it is possible to solve the above-described problem that charges are mixed from photodiodes of different color components during charge transfer of the reading element array.

  An object of the present invention is to improve reading accuracy for each color component when an image is read by a line sensor in which a plurality of photoelectric conversion element arrays having different color components are arranged in the sub-scanning direction.

  To achieve the above object, the present invention provides a plurality of photoelectric conversion element arrays in which CCD line sensors that photoelectrically convert reading light from an image reading surface are arranged for each color component, and the accumulated charges are sub-scanned in the sub-scanning direction. The light-emitting means for irradiating the image reading surface with line light is controlled by the light source control means. In this case, the light source control unit is configured to turn off or block the light irradiated from the light emitting unit to the image reading surface when transferring at least one column of charge from the sub-scanning direction transfer path to the output transfer path. It is a feature.

  In further detail, the light emitting means (9) for irradiating the image reading surface (2) with line light, the light source control means for controlling the light emitting means, and the reflected light or transmitted light from the original image is collected. Imaging optical means (7) for carrying out, and a CCD line sensor (8) for photoelectrically converting light from the imaging optical means. The sensor includes a plurality of photoelectric conversion element arrays (Rh, Gh, Bh) arranged in parallel in the sub-scanning direction for each color component, and a sub-scanning direction for transferring charges of the photoelectric conversion element arrays in the sub-scanning direction. The CCD licensor has a transfer path and an output transfer path (Rs, Gs, Bs) for outputting charges from the sub-scanning direction transfer path.

  Therefore, the light source control means turns off or blocks the light irradiated from the light emitting means to the image reading surface when transferring at least one charge of the plurality of photoelectric conversion element rows from the sub-scanning direction transfer path to the output transfer path. Configure.

  According to the present invention, when the light source control means for irradiating the image reading surface with line light transfers the charge of at least one column of the photoelectric conversion element array from the sub-scanning direction transfer path to the output transfer path, Since the light applied to the light is turned off or shielded, the following effects can be obtained.

  Since the light emitting means is turned off or shielded when transferring the charges accumulated in the photoelectric conversion element array arranged in the sub-scanning direction for each color component to the output transfer path, the charges of other color components are transferred during this charge transfer. There is no fear of mixing. Therefore, for example, when an image is read for each of the RGB color components, it is possible to reduce the color mixture that is accumulated in the photoelectric conversion element row (photodiode row) having a color component different from the read color and mixed in the output transfer path.

  Furthermore, by using an LED light emitting element as the light emitting means, it is possible to control the light emission and extinction with high responsiveness according to the transfer clock of the photoelectric conversion element array. Further, when a cold cathode tube or the like is used as the light emitting means, the light amount can be adjusted according to the transfer timing by disposing an open / close shutter between the light source and the reading surface.

1 is an explanatory diagram of the overall configuration of an image reading apparatus according to the present invention. FIG. 2 is an explanatory diagram illustrating a configuration of a reading carriage that reads a document image in the apparatus of FIG. 1. 1A and 1B show the structure of a CCD line sensor in the apparatus of FIG. 1, wherein FIG. 1A is an explanatory diagram of a conceptual configuration, FIG. 1B is a conceptual explanatory diagram of an image reading optical system, and FIG. Figure. Explanatory drawing of the control structure of the apparatus of FIG. 4A and 4B show charge transfer control of the line sensor in the control configuration of FIG. 4, wherein FIG. 4A is a timing chart, and FIGS. 4B and 4C are conceptual explanatory diagrams of charge transfer. FIG. 6 is an explanatory diagram of charge transfer shown in FIG. 5. It is explanatory drawing of the detailed structure of the light source in the apparatus of FIG. 1, (a) is structure explanatory drawing of a light source unit, (b) is the structure explanatory drawing of the light-emitting body, (c) is the light emission control method different from (b). FIG. FIG. 6 is a perspective explanatory view of a reading carriage.

FIG. 1 shows an image reading apparatus A according to the present invention. In the illustrated apparatus, an image reading unit (reading carriage) 6 is built in an apparatus housing 1, and a CCD line sensor 8 and a light source means 9 are incorporated in the reading unit 6. The present invention relates to light source control when a CCD licensor 8 reads a document image on a reading surface (platen) 2. Therefore, “the structure of the CCD licensor”, “the structure of the light emission means”, “the structure of the light emission control means”, and “the image reading apparatus” will be described in this order.

[Structure of CCD line sensor]
FIG. 3A shows a model diagram of a CCD line sensor according to the present invention.
Photoelectric conversion element groups (photodiodes; hereinafter simply referred to as “element rows”) are arranged in a line in the main scanning direction (X direction in the drawing). A plurality of element rows are arranged in parallel in the sub-scanning direction (Y direction in the drawing) for each color component. For example, the illustrated R element array Rh is a red photosensitive element array, the G element array Gh is a green photosensitive element array, and the B element array Bh is a blue photosensitive element array, which are arranged at intervals in the sub-scanning direction. Various combinations of the RGB arrangement order are possible, but the case where the arrangement order is the order of the R, G, and B columns will be described.

  An R shift gate Rg is arranged in the R element row Rh, a G shift gate Gg is arranged in the G element row Gh, and a B shift gate Bg is arranged in parallel in the B element row Bh. The photoelectric conversion element is gate-connected. In addition, an R shift register (R output transfer path) Rs is arranged in parallel in the main scanning direction to the R element array Rh via an R shift gate Rg. Similarly, a G shift register (G output transfer path) Gs is provided in parallel with the G element array Gh, and a B shift register (B output transfer path) Bs is provided in parallel with the B element array Bh.

  The G shift register (G output transfer path) Gs and the B shift register (B output transfer path) Bs are arranged outside the G element row Gh, the G shift gate Gg, the B element row Bh, and the B shift gate Bg (FIG. 3 ( a) Upper side) arranged in parallel in the sub-scanning direction. As shown in FIG. 3B, the original image reading position, red Rp, green Gp, and blue Bp are displaced. In order to reduce the amount of deviation of the reading position, it is necessary to reduce the spacing Ln between the RGB element rows to make the arrangement of the element rows highly dense. For this reason, the G shift register (G output transfer path) Gs and the B shift register (B output transfer path) Bs are arranged outside (above FIG. 3A) the GB element array.

  In order to transfer the charges of the G element array Gh to the G output transfer path Gs by the element array arrangement of FIG. 3A, the B element array Bh is used as the transfer path and transferred. At this time, if light is irradiated to Bh when passing through Bh, the charge of the B component is superimposed on the charge of the passing G element array and sent to the G output transfer path Gs.

  Therefore, according to the present invention, when the light source means 9 for irradiating light on a document image, which will be described later, passes through Bh while transferring the charge of the G element array Gh to the G output transfer path Gs, it is “turned off or shielded”. It is characterized by. As shown in FIG. 3C, the light source is turned on at the time of charge transfer (Rtr, Btr) between the R element row Rh and the B element row Bh where there is no possibility that charges are mixed from different element rows, but the G element row Gh. During the charge transfer (Gtr), the light source is controlled to be in the OFF state. Thereby, for example, the charge of the B element row is not mixed in the charge transfer of the G element row Gh.

  FIG. 4 is an explanatory diagram of a control configuration for controlling the CCD line sensor 8, and the CCD line sensor 8 is electrically connected to the output processing unit 23. For example, the output processing unit 23 amplifies an output value from the sensor with an amplifier and converts it into a digital signal with an A / D converter. The digitized output value is transferred to the line memory 24 of the image processing unit 25. The output value (image data) converted into a digital signal by the image processing unit 25 is subjected to correction processing such as shading correction and color correction processing. The corrected output value is stored in a transfer memory (not shown) and transferred to the external device C in accordance with a transfer request command from the external device.

  A driver circuit 21 is connected to the CCD line sensor 8, and this circuit comprises a timing generator 21. The timing generator 21 is provided with an operation setting register therein, and is configured to be able to adjust a signal timing to be output by changing a register value.

  The control CPU 20 controls the CCD drive signal by designating a register value in the timing generator 21. At the same time, the control CPU 20 controls the power supply circuit 22 of the light source 9 to turn the light source lamp on and off. The illustrated light source 9 is composed of an LED illuminator, the driving power supply is pulse-controlled, and the control CPU 20 is configured to control the lighting time by PWM control of a pulse generator provided in the power supply circuit 22. Yes.

  Further, the control CPU 20 causes an “image reading operation” to be described later. In this image reading operation, a reading carriage 6, which will be described later, is moved in the sub-scanning direction along a document image on the platen at a predetermined speed, and images are read line-sequentially. Therefore, the control CPU 20 controls a moving motor (not shown) of the reading carriage 6 on which the CCD line sensor 8 is mounted simultaneously with the control of the light source 9.

  Next, output control of the CCD line sensor 8 by the control CPU 20 will be described. FIG. 5 is a timing chart of the shift signal Sf sent from the timing generator 21 to the CCD line sensor 8 and the ON / OFF signal (lighting signal) St of the power supply circuit 22. Both the shift signal Sf and the ON / OFF signal St are shown in FIG. Controlled by the control CPU 20. FIG. 6 is a table for explaining this timing chart. For convenience of explanation, only the transfer timings of the G element row Gh and the B element row Bh described above will be described.

  “[1] [2] [3]...” In the table of FIG. 6 represents a shift signal, and charges move at each signal timing. “Gn−1” represents the charge of the G element array Gh accumulated until the reading of the nth line of the document image is started. “G [1]” is the charge accumulated in the shift signal [1]. “Bn−1” represents the charge of the B element array Bh accumulated until the start of reading of the nth line, and “B [1]” represents the charge accumulated in the shift signal [1].

  Therefore, in the case of the G element row Gh, the charge transfer path of the G element row Gh and the B element row Bh is “G photosensitive portion Gh” → “G shift gate Gg” → “B photosensitive portion Bh” → “B shift gate”. “Bg” → “G transfer path (shift register) Gs”. In the case of the B element array Bh, “B photosensitive portion Bh” → “B shift gate Bg” → “G transfer path (shift register) Gs” → “ B transfer path (shift register) Bs ".

  Therefore, the movement of the charges when the light source control is performed will be described for the G element array Gh. As shown in FIG. 6, in the initial state, the charge Gn−1 is accumulated in the photosensitive portion (G element array Gh). At this time, the light source is in a lighting state. Then, the shift signal [1] is started and the transfer gate is opened. The accumulated Gn-1 moves to the adjacent G shift gate Gg. During this shift signal [1], since the photosensitivity is performed even during the charge transfer, G [1] is newly accumulated. The accumulated G [1] moves to the next (G shift gate Gg) because the gate is open. When the shift signal [1] ends, Gn-1 and G [1] are moved to the G shift gate Gg. This state is shown as a schematic diagram in FIG.

  Next, when the shift signal [2] is started, the charges of [Gn-1 + G [1]] transferred to the G shift gate Gg move to the B element row Bh (photosensitive portion) adjacent thereto. At this time, the light source 9 is turned off, and no charge is accumulated in the photosensitive portion in both the G element row and the B element row. This state is shown as a schematic diagram in FIG.

  Next, when the shift signal [3] is started, the charge of [Gn-1 + G [1]] transferred to the B shift gate Bg moves to the G shift gate Gg adjacent thereto. The light source 9 is kept off, and no charge is accumulated in the photosensitive portions (Gh, Bh) of the G element row and the B element row. When the shift signal [4] is started, the charge of [Gn-1 + G [1]] sent to the G shift gate Gg moves to the G transfer path Gs.

  Therefore, the light source 9 is turned on to expose the photosensitive portions of the G element row Gh and the B element row Bh. At this time, G [4] is accumulated in the photosensitive portion of the G element array Gh. Next, when the shift signal [5] is started, the charge of [Gn-1 + G [1]] sent to the G transfer path Gs moves in the transfer path. At this time, since the light source is in the lighting state, the photosensitive portions of the G element row Gh and the B element row Bh are subjected to photosensitivity, and G [5] is accumulated in the photosensitive portion of the G element row Gh.

  Therefore, the charge [G [4] + G [5]] accumulated in the G element row Gh remains in the photosensitive portion of the G element row Gh as it is and becomes the initial accumulated charge in the next line (n + 1 line). This charge [G [4] + G [5]] is represented as Gn in the table of FIG.

[Image reading device]
Next, the image reading apparatus A when the CCD line sensor 8 reads an image will be described. FIG. 1 shows the overall configuration. The image reading apparatus A is connected to an image handling apparatus such as a computer (not shown), and is connected to an image forming apparatus such as a printer that reads a document image and transfers the data, and reads the document image and prints the data. Output.

  In the illustrated image reading apparatus A, a platen 2 is provided in a casing 1, and a reading carriage 6 is built in such a manner that the platen 2 can reciprocate along the platen 2. The reading carriage 6 is connected to a light source 9 for irradiating the original image on the platen with reading light, a CCD line sensor 8 for photoelectrically converting reflected light from the original image, and a reflecting mirror 10 for guiding the reflected light to the sensor. An image lens 7 is built in.

  In addition, the reading carriage 6 may include a light source 9 and a reflection mirror 10, and the imaging lens 7 and the CCD line sensor 8 may be disposed on a chassis disposed at the bottom of the casing 1, for example. 6 shows a reading mechanism of a reduction optical system as an example, but a reading mechanism (contact type) of an equal magnification optical system may be used.

  The apparatus shown in FIG. 1 is provided with a slit exposure type platen 3 in addition to the flat bed type platen 2, and the flat bed type platen 2 is placed and set with a document sheet stationary. Set the seat to run at a predetermined speed. The platen in the present invention may be either a flat bed type, a slit exposure type platen, or may have both platens as shown. A feeder device B is disposed above the slit exposure platen 3 and feeds the original sheet to the reading unit.

  A light source 9 is mounted on the reading carriage 6 (hereinafter referred to as “carriage”) as shown in FIG. The light source 9 irradiates the reading portion R of the flat bed type platen 2 with an angle θ1 from an oblique direction. The reflected light of the document image is guided to the imaging lens 7 through the first mirror 10a, the second mirror 10b, the third mirror 10c, the fourth mirror 10d, and the second mirror 10e, and is connected to the CCD line sensor 8 from this lens. An optical path is formed so as to image.

[Light source unit]
The light source 9 will be described. This will be described with reference to FIGS. The carriage 6 described above is provided with a light source accommodating portion (light guide support frame) 13 as shown in FIG.

  A light source 9 is accommodated in the light source accommodating portion 13, and the light source 9 includes a light guide 30 and a light emitter 40. As shown in FIG. 7, the light guide 30 is composed of a rod-shaped light transmitting member having a length corresponding to the reading width (reading line width) W of the reading surface R. The light guide 30 is formed of a material having high translucency such as transparent acrylic resin and epoxy resin, and the cross-sectional shape thereof is rectangular, or a cross-sectional fan shape as shown, and the left and right end surfaces 31L, 31R. A light emitter 40 is disposed in the case. The light guide 30 has a light scattering surface 32 and a light emitting surface 33 disposed so as to face each other.

  As described above, the light scattering surface 32 and the light emitting surface 33 are arranged to face each other with a length of the reading line width W substantially in parallel with a distance Ld. The light scattering surface 32 is subjected to surface processing so as to diffusely reflect the light that is formed on the concavo-convex surface by painting, etching, molding or the like. Further, the light emitting surface 33 is surface-finished like a lens surface with high translucency.

  Therefore, the light introduced into the light guide 30 is diffused in a predetermined direction by the light scattering surface 32, and the light introduced into the light emitting surface 33 is reflected inside when the angle is equal to or larger than a predetermined critical angle, and when the angle is equal to or smaller than the critical angle. It is emitted to the outside. The light indicated by the arrow ha in FIG. 7A is reflected in the light guide 30 and dispersed in the reading line width W direction, and the light indicated by the arrow hb is emitted from the light emitting surface 33 to the reading surface R. Although not shown, light is incident in a spherical direction (360-degree direction; the illustrated one is a 60-degree wide-angle direction) from a light emitter 40, which will be described later, and irradiates the light scattering surface 32 and the light emitting surface 33.

  The light emitter 40 will now be described. The light emitter 40 is disposed on at least one end surface of the light guide 30. FIG. 7A shows a case where the light source is disposed on the left end surface 31L and the right end surface 31R, and the light sources on the left and right end surfaces are configured so as to have left and right symmetry. Although not shown, the light emitter 40 is disposed on one of the left and right end surfaces, and a reflecting member (mirror member) is disposed on the other side. The reflecting member at this time is configured so that the virtual light source is symmetrical with the light emitter 40.

  The light emitter 40 includes LED light emitting elements 41 and 42 and is connected to the power supply circuit 22. Although not shown, the power supply circuit 22 is provided with a pulse generator, and supplies a pulse current to the LED light emitting elements 41 and 42. This pulse current is ON / OFF controlled by the control CPU 20. Accordingly, the control CPU 20 performs ON / OFF control of the light (reflected light from the document image) projected onto the CCD line sensor 8 by controlling the light emitting body 40 to blink. At the same time, the control CPU 20 controls the output timing of the charges accumulated in the line sensor 8.

  In this way, when turning on / off the light projected on the CCD line sensor 8, a method of blinking the light emitter 40 (see FIG. 7A) and light in the optical path from the light emitter 40 to the CCD line sensor 8. Shutter means for blocking the above may be arranged. FIG. 7C shows a case where the liquid crystal shutter 45 is arranged on the light emitting body 40 similar to the above. Although not shown, the liquid crystal shutter 45 is configured to be openable / closable by the control CPU 20.

A Image reading device 1 Device housing 2 Reading surface (platen)
6 Image reading unit (reading carriage)
7 Imaging lens 8 CCD line sensor 9 Light source (LED emitter)
20 Control CPU
21 Driver circuit (timing generator)
22 Power supply circuit 23 Output processing unit 24 Line memory 25 Image processing unit 30 Light guide 40 Light emitter 41 LED light emitting element 42 LED light emitting element 45 Shutter means Rh R element array (red photosensitive element array)
Gh G element array (green photosensitive element array)
Bh B element array (blue photosensitive element array)
Rg R shift gate Gg G shift gate Bg B shift gate Rs R shift register (R output transfer path)
Gs G shift register (G output transfer path)
Bs B shift register (B output transfer path)
Rtr charge transfer (red)
Btr charge transfer (blue)
Gtr charge transfer (green)
Sf Shift signal St Lighting signal Gn Charge

Claims (3)

Light emitting means for irradiating light to the read-up surface,
Light source control means for controlling the light emitting means;
And Lula-sensor to photoelectrically convert the light from the reading surface,
With
Before Kira-sensor is,
A photoelectric conversion element array arranged in a line in the main scanning direction and arranged in parallel in the sub scanning direction for each color component ;
A shift gate that is a photoelectric conversion element and a gate connection of each pixel are arranged in parallel to the each photoelectric conversion element column,
A sub-scanning direction transfer path in the sub-scanning direction and a main scanning direction transfer path in the main scanning direction for transferring the charge generated in each photoelectric conversion element array to the output unit;
Consists of
The sub-scanning direction transfer path is
The charge generated in each photoelectric conversion element array is transferred to a gate-connected shift gate, and then the charge is transferred from the shift gate to an adjacent photoelectric element array,
The light source control means includes
When transferring the charges of the photoelectric element array to the shift gate, it lights the light emitting unit, when the charge transfer in the photoelectric conversion element column adjacent the shift gate, you turn off or shielding the light emitting means image reading device comprising a call. The light source control means includes
2. The image according to claim 1, wherein when transferring charges from the shift gate to an adjacent photoelectric conversion element array , light is shielded by a shutter disposed between the light emitting unit and the image reading surface. Reader. The photoelectric conversion element rows are configured in three rows for each color component,
The light source control means includes
When transferring charges charged in two photoelectric conversion element rows out of the three rows from the sub-scanning direction transfer path to the output transfer path,
The image reading apparatus according to claim 1, wherein light emitted from the light emitting unit to the image reading surface is turned on and then turned off or shielded.

Images