JP2002354196A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem in a conventional image reader employing an in-pixel transfer CCD that has caused color mixture in the case of transferring electric charges of a light receiving section via another light receiving section. SOLUTION: The in-pixel transfer CCD including a plurality of light receiving sections 101-103 closely placed to generate electric charges depending on the intensity of an optical signal and a plurality of charge transfer destinations 104, 106, 108 provided corresponding to a plurality of the light receiving sections to transfer the electric charged from a plurality of the light receiving sections is adopted for an image pickup element, when the electric charges from the light receiving section 102 placed in the middle are transferred to the charge transfer destination 106 via the adjacent light receiving section 103, an illumination light source 210 is put out to prevent occurrence of the electric charges in the light receiving section being a cause of color mixture.

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 for reading a document image or the like, and more particularly to an improvement in an image reading apparatus using an intra-pixel transfer type image pickup device.

[0002]

2. Description of the Related Art FIG. 6 is a diagram showing a configuration example of a CCD linear image sensor 201 used in a conventional color image reading device. In FIG. 6, 101, 102, 1
Reference numeral 03 denotes a light receiving unit having R, G, and B color filters, respectively. The light receiving unit is provided with a diode for converting photons into electric charges (electrons) for each pixel. For each light receiving unit, a predetermined time (accumulation time)
The charge generated in the light receiving section after the end of one cycle of accumulation time is odd (ODD)
CCD transfer unit for pixels and C for even (EVEN) pixels
The data is transferred (shifted) to the CD transfer unit. CCD transfer unit 10
The charges transferred (shifted) to 4 to 109 are sequentially transferred in a fixed direction in the CCD transfer unit while the light receiving unit is receiving and storing the next line, and sequentially transferred by the respective amplifiers 110 to 115. , Are converted into voltage signals and output.

However, in a conventional color linear image sensor as shown in FIG. 6, a CCD transfer section for transferring charges from the light receiving sections in a certain direction between the R, G, and B light receiving sections. Therefore, it is necessary to set the RG interval and the GB interval shown in FIG. 6 to be large. Therefore, when signal processing such as masking operation is performed on the R, G, and B signals read by such a CCD sensor, a memory or the like for correcting a deviation of each of the read positions of the R, G, and B is required. Is R,
As the interval between G and B increases, the required memory capacity increases.

In view of such a point, a structure has recently been proposed in which the CCD transfer unit is not disposed adjacent to the light receiving unit as shown in FIG. 7, but is disposed between light receiving units corresponding to different colors. In the CCD shown in FIG. 7, charges generated in the light receiving unit 102 located at the center are transferred (shifted) to the CCD transfer units 106 and 107 via the light receiving unit 103. Hereinafter, this type of CCD is referred to as an intra-pixel transfer type CCD.

The units 101 to 115 constituting the intra-pixel transfer type CCD shown in FIG. 7 are the same as the units 101 to 115 constituting the CCD described with reference to FIG. In the intra-pixel transfer type CCD, it is not necessary to arrange a CCD transfer unit between the light receiving units of each color, so that the intervals of R, G, and B can be greatly reduced as compared with the conventional sensor. Can be reduced in memory capacity for correcting the positional deviation.

Further, as a light source of the image reading device,
Halogen lamps, fluorescent lamps, xenon lamps and the like are used. Halogen lamps have usually been used as a light source for this type of image reading apparatus. Halogen lamps have light brightness, but the temperature rise of the apparatus accompanying the temperature rise of the lamp is large, and power consumption of 200 to 300 W is required. This necessitates an increase in power consumption of the entire apparatus.
In recent years, in order to avoid such problems, fluorescent lamps and xenon lamps having high luminance have been developed and are being used as light sources for image reading apparatuses.

[0007] Fluorescent lamps and xenon lamps use a small amount of mercury particles and Ar or Kr, Xr of several Torr in a hollow tube on a rod.
In many cases, various phosphors are applied to the inner wall of the tube, electrodes are arranged at both ends of the tube, and the tube is sealed. The discharge from the electrodes excites the phosphor coated on the inside of the tube with ultraviolet rays emitted from mercury or various gases, and emits visible light according to the emission characteristics of the phosphor.

As the phosphor, various phosphors are selected and used according to the spectral energy characteristics required as a light source. In particular, in a color image reading device, R
A light source of a wide wavelength range corresponding to GB or the like is required. In particular, when a light source with high luminance is required, a method of mixing phosphors of a plurality of colors and applying the mixture to the inner wall of a tube is used. I have. When controlling the amount of light emitted from fluorescent lamps and xenon lamps, the amount of light emitted is controlled by a pulse width modulation method that controls the lighting time at a constant current value, instead of controlling the lighting voltage as with a halogen lamp. A control method is generally used.

FIG. 8 is a diagram showing an example of a control circuit for controlling a pulse width corresponding to a lamp lighting time. CPU
1 outputs an ON / OFF signal S1 for turning ON / OFF the switching transistor Q1 at a predetermined frequency. A predetermined input voltage is supplied to the inverter transformer 2 from a power supply (not shown). C1 is a resonance capacitor that stably oscillates the inverter transformer 2 according to the frequency of the ON / OFF signal S1 output from the CPU 1. Reference numeral 3 denotes a current adjusting inductor for adjusting the impedance on the secondary side of the inverter transformer 2. A switch circuit 4 turns on / off a voltage applied to the fluorescent lamp 5 by a PWM signal S2 output from the CPU 1. Reference numeral 6 denotes a light amount sensor, 7 denotes an amplifier, 8 denotes an A / D converter, and inputs a light amount signal S3 to the CPU 1.

FIG. 9 shows a current flowing through the fluorescent lamp 5. FIG.
(A) shows an ON / OFF signal S1. When "H", the switching transistor Q1 is turned on. FIG. 9B shows the PW
M signal S2, and when "L", the switch circuit 4 is turned on,
During the “L” period, the voltage between both terminals of the fluorescent lamp 5 becomes 0 V,
The fluorescent lamp 5 turns off. FIG. 9C shows the tube current of the fluorescent lamp 5, and indicates that no current flows through the fluorescent lamp 5 while the PWM signal S2 is "L".

Normally, the ON / OFF signal S1 shown in FIG.
Is sufficiently higher than the frequency of the PWM signal S2 (for example, 10 to 10 of the frequency of the PWM signal S2).
0 times frequency). Further, the frequency of the PWM signal S2 is higher than the optical frequency of turning on and off the fluorescent lamp 5,
Lighting and extinguishing are repeated electrically according to the cycle of the PWM signal, but apparently the light is turned on at a constant light amount corresponding to a current value obtained by averaging the lamp current.

The fluorescent lamp 5 is provided with a light amount sensor 6 composed of a photodiode or the like, and outputs a photocurrent corresponding to the amount of light emitted from the fluorescent lamp 5. This photocurrent is converted to a voltage value by the amplifier 7 and amplified, and then converted to a digital signal by the A / D converter 8, and the light amount signal S3
Is input to the CPU 1. In the CPU 1, the light amount signal S
3 is compared with a predetermined value, and when the light amount of the fluorescent lamp 5 is smaller than the predetermined value, the "H" period of the PWM signal S2 is lengthened to increase the light amount of the fluorescent lamp 5, thereby increasing the light amount of the fluorescent lamp 5. Is larger than a predetermined value, the "H" period of the PWM signal S2 is shortened to reduce the light amount of the fluorescent lamp 5. That is, the PWM signal S in the 1Hsync period
The light amount of the fluorescent lamp 5 is adjusted by the Duty of 2.

[0013]

However, when an intra-pixel transfer type CCD as shown in FIG.
In order to transfer (shift) the received and accumulated charge, the D transfer unit needs to pass through a light receiving unit (pixel) of a color different from the color of the charge transferred by the CCD transfer unit. this is,
This is called intra-pixel transfer. In this case, even when the light passes through the light receiving section of a different color, the light is irradiated on the light receiving section, so that there is a problem that a slight color mixture is caused at the time of transfer (shift) in the CCD transfer section.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to prevent color mixing when transferring the electric charge of the light receiving section via the light receiving section of another color. An image reading device is provided.

[0015]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image reading apparatus for reading a document image by irradiating a document with light from a light source and receiving the reflected light by an image sensor. And a plurality of light receiving units that receive an optical signal corresponding to each color and generate a charge according to the intensity of the optical signal; and a plurality of light receiving units provided corresponding to the plurality of light receiving units. A plurality of charge transfer units for respectively transferring the charges from the light receiving units, and when transferring the charge of the light receiving unit located at the center of the plurality of light receiving units to the charge transfer unit, there is another When the charge of the light receiving portion located at the center is transferred through another adjacent light receiving portion, the image pickup device comprises an intra-pixel transfer type image pickup device that transfers the charge to a corresponding charge transfer portion via the light receiving portion. Is an image characterized by turning off the light source. It is achieved by only up device.

[0016]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a configuration diagram showing an embodiment of the image reading apparatus of the present invention. The image reading apparatus irradiates a document 212 placed on a document table glass 211 with an illumination light source 210 such as a fluorescent lamp or a xenon lamp provided with a reflection shade 209, and
The reflected light reflected from the mirror 208, 205, 206
Further, the original image is focused on a light receiving surface of a CCD (color linear image sensor) 201 by a lens 202 to form an original image. The configuration of the CCD 201 will be described later in detail.

In FIG. 1, a portion including the illumination light source 210 surrounded by a broken line 207 moves at a speed V in the direction of the arrow in the figure, and a portion included in the broken line 203 moves at a speed V / 2 in the direction of the arrow in the figure. , The image of the entire document 212 can be read.

As a control circuit for controlling the illumination light source 210, the control circuit shown in FIG. 8 can be used. In FIG. 8, the CPU 1 outputs an ON / OFF signal S1 for turning ON / OFF the switching transistor Q1 at a predetermined frequency. A predetermined input voltage is supplied to the inverter transformer 2 from a power supply (not shown). C1 is a resonance capacitor, which is an ON / OFF signal S output from the CPU1.
The inverter transformer 2 oscillates stably according to the frequency of 1. Reference numeral 3 denotes a current adjusting inductor for adjusting the impedance on the secondary side of the inverter transformer 2. Reference numeral 4 denotes a switch circuit, which is a PWM signal S output from the CPU 1.
2, the voltage applied to the illumination light source 210 (for example, a fluorescent lamp) is turned on / off. 6 is a light amount sensor,
Reference numeral 7 denotes an amplifier, and 8 denotes an A / D converter, which inputs a light amount signal S3 to the CPU 1.

FIG. 9 shows the current flowing through the illumination light source. FIG. 9A shows an ON / OFF signal S1. When "H", the switching transistor Q1 is turned on. FIG. 9B shows P
Indicates the WM signal S2, and when "L", the switch circuit 4 is turned on.
Then, during the “L” period, the voltage between both terminals of the illumination light source 210 becomes 0 V, and the illumination light source is turned off. FIG. 9C shows the tube current of the illumination light source 210, and the PWM signal S2 is "L".
The period indicates that no current is flowing through the illumination light source.

Normally, the frequency of the ON / OFF signal S1 is P
A frequency sufficiently higher than the frequency of the WM signal S2 (for example, a frequency that is 10 to 100 times the frequency of the PWM signal S2)
It is. Further, the frequency of the PWM signal S2 is higher than the optical frequency of turning on and off the illumination light source, and
Lighting and extinguishing are repeated according to the cycle of the WM signal, but apparently the light is turned on at a constant light amount corresponding to a current value obtained by averaging the lamp current. The light source for illumination is provided with a light amount sensor 6 composed of a photodiode or the like, and outputs a photocurrent corresponding to the light amount emitted from the light source for illumination.

This photocurrent is converted to a voltage value by the amplifier 7 and amplified, then converted to a digital signal by the A / D converter 8 and input to the CPU 1 as a light amount signal S3. The CPU 1 compares the light amount signal S3 with a predetermined value, and when the light amount of the illumination light source 210 is smaller than the predetermined value, increases the “H” period of the PWM signal S2 to increase the light amount of the illumination light source. When the light amount of the illumination light source is larger than the predetermined value, the light amount of the illumination light source 210 is reduced by shortening the "H" period of the PWM signal S2. That is, the PWM signal S in the 1Hsync period
The light amount of the illumination light source is adjusted by the Duty of 2.

FIG. 2 is a diagram showing a configuration example of the linear image sensor 201 of the present embodiment. 101 is an R light receiving unit, 1
02 is an R light receiving unit, and 103 is a B light receiving unit. Also, 10
4, 106, 108 are CCD transfer units, 110, 112,
Reference numeral 114 denotes an amplifier, and 116 to 119 denote transfer switch units.

Normally, the intra-pixel transfer type CCD has light receiving units 101 to 103 corresponding to R, G, and B colors as shown in FIG.
Are transferred (shifted) to the CCD transfer units 104 to 109 separately for odd-numbered pixels and even-numbered pixels.
The signals are sequentially transferred in a fixed direction in the D transfer unit, and are sequentially converted into voltage signals by the respective amplifiers 110 to 115 and output. However, here, as shown in FIG. , G, and B, the charges generated in the light receiving units 101 to 103 do not separate and transfer (shift) the odd-numbered pixels and the even-numbered pixels separately to the CCD transfer unit. Transfer unit 10
The transfer type (shift) to 4,106,108 will be described. As shown in FIG. 7, the charge of the light receiving unit may be separated into even pixels and odd pixels. In this case, similarly to FIG. 7, a CCD transfer section may be provided for even and odd pixels.

As means for transferring the charges generated in the light receiving units 101 to 103 to the CCD transfer units 104, 106 and 108, the transfer switch units 116 to 119 will be described here for the sake of simplicity. Each of the transfer switches 116 to 119 is operated by a transfer switch signal S116 to 119.
The charge generated in step (1) is transferred to the CCD transfer unit 104. The transfer switch unit 117 transfers the charge generated by the R light receiving unit 102 to the B light receiving unit 103, the transfer switch unit 118 transfers the charge transferred from the R light receiving unit 102 to the CCD transfer unit 106, and the transfer switch unit 119 transfers the charge to the CCD transfer unit 106. The charges transferred to the unit 106 are transferred to the CCD transfer unit 108, respectively.

Each switch transfer section has a switch section for each pixel, and transfers electric charge for each pixel between the light receiving section and the CCD transfer section or between the light receiving sections. Here, the light receiving units 101, 102, and 103 are light receiving units having R, G, and B color filters, respectively. In this light receiving part,
A diode (photoelectric conversion element) for converting received photons into electric charges (electrons) is provided for each pixel. In the present embodiment, for example, unlike the conventional linear image sensor shown in FIG. 6, since the CCD transfer unit is not arranged between the light receiving units corresponding to each color, the interval between the light receiving units can be reduced. Becomes

Each of the GR interval and the RB interval is a distance of about 2 times “2A” when the size of one side of a pixel capable of receiving light is “A” (see FIG. 2). It is possible to shorten by. Therefore, it is possible to set the interval between the light receiving sections to be narrower than when a linear image sensor is configured by arranging a CCD transfer section between each light receiving section as in the conventional case. It is possible to reduce the memory capacity for reading position correction.

Further, according to the configuration of this embodiment, the CCD
The transfer unit 104 and the CCD transfer units 106 and 108 are divided and arranged in the sub-scanning direction with the light receiving units 101 to 103 of each color interposed therebetween. That is, the CC for the light receiving unit G (101)
The D transfer unit 104 is arranged in the upper part of the figure, and the CCD transfer units 106 and 108 for the light receiving unit R (102) and the light receiving unit B (103) are arranged separately in the lower part of the figure. With such an arrangement, it is possible to minimize the number of light receiving units that transfer the charge accumulated in each light receiving unit via light receiving units of other colors (light receiving unit). 102 to 103).

FIG. 3 is a timing chart for explaining the operation of the present embodiment. 3A shows an Hsync signal, and FIGS. 3B to 3D show transfer switch signals S116 to S116.
9, FIG. 3E shows a PWM signal S2 for controlling a power supply applied to the illumination light source 210, and FIG.
Is a signal indicating the tube current flowing through the tube. 3 (a) to 3 (e)
Are output from a CPU (not shown).

FIG. 4 shows the light receiving section 101 at each timing.
FIG. 10 is a diagram showing to which unit the electric charge generated in to 103 is transferred. 4 (a) to 4 (d).
Corresponds to T0 to T5 in FIG. Next, FIGS.
The operation of the image reading apparatus using the intra-pixel transfer type CCD shown in FIG. 2 will be described with reference to FIG. In particular, a method in which the charge accumulated in the light receiving unit is transferred via another light receiving unit, and the amount of color mixture at this time is suppressed will be described.

FIG. 4A shows that R, R by time T0 in FIG.
This shows a state in which charges are generated based on the amounts of light applied to the G and B light receiving units 101 to 103. The charge generated in the light receiving unit 101 is indicated by horizontal hatching, the charge generated by the light receiving unit 102 is indicated by black, and the charge generated by the light receiving unit 103 is indicated by vertical hatching. In this state, when the transfer switch signal S118 is turned on at time T0 as shown in FIG. 3C, the B charge generated in the B light receiving unit 103 is transferred to the R transfer CCD 106 as shown in FIG. . At time T1, the transfer switch signal S118 turns off.

Next, as shown in FIGS. 3B and 3D, at time T2, the transfer switch signals 116, 117 and 119 are transmitted.
Is turned on, the G light receiving unit 101 is turned on as shown in FIG.
The G charge generated in the above is transferred to the CCD transfer unit 104 and the R light receiving unit 1
The R charge generated in 02 is transferred to the B light receiving unit 103, and the B charge in the CCD transfer unit 106 is transferred to the CCD transfer unit 108. Further, when the transfer switch signal 118 is turned on at time T4 as shown in FIG. 3C, the R charges in the B light receiving unit 103 are transferred to the CCD transfer unit 106 as shown in FIG.
Is forwarded to

Here, if the illumination light source 210 is turned on during the period from time T3 to T4, the B light receiving unit 103 generates B charge, and the R charge and the B charge transferred from the R light receiving unit 102 are changed. They are mixed, that is, they are mixed.
Therefore, in the present embodiment, the illumination light source 210 is turned off during the period from time T3 to T4 so that the R charge and the B charge are not mixed, and the R charge in the B light receiving unit 103 is completely removed as shown in FIG. After the time T5 when the signal is transferred to the CCD transfer unit 106, the PWM signal S2 is turned on, and the illumination light source 210 is turned on as shown in FIG.

Next, the G charge, R charge, and B charge transferred to the CCD transfer unit 104, the CCD transfer unit 106, and the CCD transfer unit 108 are supplied to the amplifiers 110, 112 by known methods.
114, and output as a G signal, an R signal, and a B signal. Hereinafter, by repeating the same operation with Hsync in FIG. 3A as a trigger, the entire original image is read as an electric signal. The light source for irradiating the original is not limited to a fluorescent lamp or a xenon lamp, and the same effect can be obtained with a light source that adjusts the amount of light by short-time on / off control, such as an LED.

FIG. 5 is a block diagram showing a configuration of an image data generating unit of an image reading apparatus using the linear image sensor according to the present embodiment. In FIG. 5, reference numeral 801 denotes a B including the aforementioned B light receiving unit 103 and its CCD transfer unit 108.
(Blue) signal input section, 802 is an R (red) signal input section including the R light receiving section 102 and its CCD transfer section 106, and similarly 803 is the G light receiving section 101 and its CCD transfer section 104
G (green) signal input sections each including. Each of 804 to 812 is a line buffer, and can store pixel data (binary or multi-valued data) corresponding to the number of reading elements of the light receiving unit corresponding to each color. Each of 814 to 816 is an A / D converter,
An analog image signal is input from each corresponding color signal input unit and converted into a digital signal.

Here, since the interval between the light receiving portions of each color is "2A" as described above, when the image data read by the light receiving portion B is stored in the line buffer 808, it corresponds to the read portion. The R-color image to be processed is stored in the line buffer 811, and the G-color data at that location is held in the line buffer 812. Accordingly, the image data of each color component is read from these line buffers, and the color signal generation circuit 813 creates one line of color image data. Here, the A / D converter 814
If 816 are 8-bit A / D converters,
One pixel of the image data read by this image reading device is represented by 24 bits. The color image data thus created is output to a connected computer device or the like.

[0036]

As described above, according to the present invention, the light source is turned off when the charge of the light receiving portion located at the center is transferred to the charge transfer portion via the other adjacent light receiving portion. Therefore, it is possible to surely prevent color mixing that occurs when data is transferred via light receiving units of different colors, and to prevent image deterioration due to color mixing.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating a configuration example of a linear image sensor used in the image reading device of FIG. 1;

FIG. 3 is a timing chart for explaining the operation of the embodiment of FIG. 1;

FIG. 4 is a diagram illustrating a timing at which charges generated in each light receiving unit of the linear image sensor of FIG. 3 are transferred;

FIG. 5 is a block diagram illustrating an image data generation unit according to the embodiment of FIG. 1;

FIG. 6 is a diagram showing a conventional CCD linear image sensor.

FIG. 7 is a diagram showing a conventional intra-pixel transfer type linear image sensor.

FIG. 8 is a circuit diagram showing an example of a control circuit for controlling an illumination light source used in a conventional image reading apparatus.

FIG. 9 is a timing chart showing an operation of the control circuit of FIG. 8;

[Explanation of symbols]

 101 to 103 Light receiving unit 104, 106, 108 CCD transfer unit 110, 112, 114 Amplifier 116 to 119 Transfer switch unit 201 CCD (color linear image sensor) 202 Lens 205, 206, 208 Mirror 209 Reflector shade 210 Illumination light source 211 Original Base glass 212 Original 801 to 803 Signal input unit 804 to 812 Line buffer 813 Color signal generation circuit 814 to 816 A / D converter

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4M118 AA10 AB01 BA13 FA08 FA35 GC08 GC15 5B047 AA01 BB02 BC14 CA05 CB04 5C051 AA01 BA03 DA03 DB08 DC05 DC07 5C072 AA01 CA02 CA12 EA05

Claims (1)

[Claims] 1. An image reading apparatus that irradiates a document with light from a light source and receives reflected light thereof with an image sensor to read an image of the document, wherein the image sensors are arranged close to each other and correspond to each color. A plurality of light receiving sections for receiving light signals to be generated and generating electric charges in accordance with the intensity of the light signals; and a plurality of light receiving sections provided corresponding to the plurality of light receiving sections and transferring the charges from the plurality of light receiving sections respectively A plurality of charge transfer portions, and when transferring the charge of the light receiving portion located at the center of the plurality of light receiving portions to the charge transfer portion, the corresponding charge via another adjacent light receiving portion When the transfer of the electric charge of the light receiving unit located at the center via another adjacent light receiving unit is performed, the transfer unit includes an in-pixel transfer type image pickup device that transfers the light to the transfer unit.
An image reading apparatus, wherein the light source is turned off.