JP2000036913A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader where image processing is conducted at a low capacity in the case that it is not required for a processing means at a post-stage to receive an image in full color. SOLUTION: The image reader is provided with an analog processing circuit 29 that analogically processes an electric signal converted by a photoelectric conversion element, an analog/digital conversion circuit 23 that converts an image signal outputted from the analog processing circuit 29 into a quantization signal, a digital processing circuit 30 that digitally processes the image signal quantized by the A/D converter circuit 23, and an approximate color conversion circuit 27 that converts the image signal outputted from the digital processing circuit 30 into an image signal in an approximate color. Thus, in the case that it is not required to process an image in full color by an image processing means at a post-stage, since the image signal outputted from the digital processing circuit 30 is converted into an image signal in an approximate color and outputted, the image is processed with a low capacity for the image processing means at the post-stage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus used for a scanner, a copying machine, a facsimile, and the like.
In particular, the present invention relates to an image reading apparatus that converts an original image signal read and converted into an electric signal into a digital signal and processes the digital signal.

[0002]

2. Description of the Related Art Conventionally, there are many image reading apparatuses that optically read an original image via a photoelectric conversion element, convert an image signal obtained by the reading into a digital signal, and process the digital signal. In this type of apparatus, reflected light from a document image is read for each separation color by a photoelectric conversion element, for example, a CCD, and the read image signal is converted into a digital signal by an A / D converter at a subsequent stage, and shading correction and γ correction are performed. After performing digital image processing such as, for example, a plurality of bits of image signals are output to a subsequent device such as a printer or a personal computer.

[0003]

By the way, with the recent increase in the reading accuracy of the reading device, CCDs have been developed.
As the resolution and the quantization of bits increase, the capacity of image data increases. This enlargement has caused problems such as a reduction in processing speed and a limit on the capacity of image data that can be captured.

In order to adjust the color tone of the image signal processed as described above, or to perform color processing according to the user's preference, software for image processing is separately prepared and a personal computer or the like is provided. The image processing is performed by the information processing device.

The present invention has been made in view of the above problems, and has as its object to provide an image processing apparatus capable of performing image processing with a small capacity when a subsequent processing means does not need to capture an image in full color. A reading device is provided.

Another object of the present invention is to provide an image reading apparatus capable of performing color processing in accordance with the color of a document image to be read and the user's preference.

[0007] As related related arts, Japanese Patent Application Laid-Open Nos. 3-53269, 4-235068, and 9-163169 are known.

[0008]

In order to achieve the above object, a first means is to read reflected light from a document image by a photoelectric conversion element, convert the light into an electric signal, and convert the converted electric signal into a predetermined signal. In the image reading apparatus which obtains a digital image signal by performing the above-described processing, an analog processing circuit for processing the electric signal converted by the photoelectric conversion element in an analog manner, and the image signal output from the analog processing circuit is a quantized signal An analog / digital conversion circuit for converting the image signal quantized by the analog / digital conversion circuit into a digital image, and an image signal output from the digital processing circuit to an image of an approximate color. A conversion circuit for converting the signal into a signal.

A second means is the first means, wherein the conversion circuit selects an appropriate table from a plurality of color tables stored in advance and executes a conversion process.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic sectional view showing the internal structure of an image reading apparatus according to an embodiment of the present invention. In FIG. 1, an image reading device is provided on an upper portion of a scanner body 13 and a contact glass 1 on which a read document 14 is placed.
A palogen lamp 2 for illuminating the document surface from the back side of the contact glass 1, a first to third reflection mirrors 3, 4, and 5 for receiving reflected light from the document illuminated by the halogen lamp 2 and guiding the reflected light to a subsequent stage. , These reflecting mirrors 3,
A lens unit 8 for condensing the reflected light guided by 4 and 5; a 3-line CCD sensor 9 for forming an original image condensed by the lens unit 8 on a light receiving surface and photoelectrically converting the formed original image; And 3-line CCD sensor 9
And a signal processing unit 12 for processing image data converted into an electric signal. The halogen lamp 2 and the first reflection mirror 3 are mounted on a first carriage 6, and the second and third reflection mirrors 4 and 5 are mounted on a second carriage 7, respectively. Further, a white reference plate 15 is provided adjacent to the contact glass 1 on the home position side of the first carriage 6. The white reference plate 15 is used for correcting various distortions generated by a reading optical system or the like. The first carriage 6 and the second carriage 7 are moved in the sub-scanning direction (the direction of arrow A) by a stepping motor (not shown). At that time, the second carriage 7 moves at half the speed of the first carriage 6.
The three-line CCD sensor 9 is connected to a sensor board 10.
Mounted on the signal processing unit 1 via the signal cable 11
2 is connected.

FIG. 2 is a front view showing the configuration of the three-line CCD sensor 9, and FIG. 3 is a block diagram showing the internal configuration. The CCD sensor 9 is configured by arranging color filters of separated colors RGB and coated reduced CCDs. The R-CCD 16, G-CCD 17, and B-CCD 18
Are arranged at the same dot position in the main scanning direction and are shifted by a fixed distance in the sub-scanning direction A. Therefore, each color output has a delay in the sub-scanning direction A. Therefore, it is necessary to perform correction using a line memory.

This CCD sensor 9 is, as shown in FIG.
The R-CCD16, G-CCD17, and B-CCD18 sensors for each color are divided into odd-numbered pixels and even-numbered pixels, respectively, and are arranged in two rows of registers 161, 162, 171, 172,.
181 and 182, which are driven in synchronization with the driving pulse 120 sent from the signal processing unit 12, and which are in accordance with the shift signals (1) (2) (3) 121, 122 and 123, and which are registers 161, 162 and 171. , 172, 181,
182 are respectively switched, and the image signals VRE, VRO,
VGE, VGO, VBE, and VBO are output independently. Reference numerals 163, 164, 173, 174, 18
3, 184 are the registers 161, 162, 1
These amplifiers amplify the outputs of 71, 172, 181, and 182, and are reset by 165, 175, and 185 by a reset signal, respectively.

FIG. 4 is a block diagram showing the configuration of the signal processing unit 12, and shows the CCD sensor 9 and the components for processing the output signal from the CCD sensor 9. Signal processing unit 12
Is a preamplifier circuit 19, a sample hold circuit 20,
The CCD sensor 9 includes a black level correction circuit 21, an amplification circuit 22, an A / D conversion circuit 23, a shading correction circuit 24, a memory 25, a gamma correction circuit 26, an approximate color conversion circuit 27, and a clock generator 28. Are processed in this order up to the gamma correction circuit 26, and the processed image signal is output directly from the gamma correction circuit 26 or via the approximate color conversion circuit 27. The preamplifier circuit 19, the sample and hold circuit 20, and the black level correction circuit 2 located at a stage preceding the A / D converter 23
1 and the amplification circuit 22 constitute an analog processing circuit 29 for performing analog processing, and the shading correction circuit 24, the memory 25, and the γ correction circuit 26 located at the subsequent stage of the A / D converter perform processing after digital conversion. The digital signal processing circuit 30 is configured. Hereinafter, the reading operation and the signal flow will be described in detail.

First, the original 14 placed on the contact glass 1 is illuminated by the halogen lamp 2, and reflected light from the original is transmitted through the first to third reflecting mirrors 3, 4, 5 and the lens unit 8 for three lines. An image is formed on the light receiving surface of the color CCD sensor 9 of the type, and is read line by line as the first and second carriages 6 and 7 move in the sub-scanning direction. The read image signal is received by the sensor board 10 and transmitted to the signal processing unit 12. Signal processing unit 1
In 2, the input image signal is subjected to analog processing by an analog processing circuit 29, and then converted into 8-bit digital data by an A / D converter 23.
Performs digital signal processing. The digital image signal thus obtained is converted into an image signal of an approximate color by the approximate color conversion circuit 27 as necessary. Also, C
Signals necessary for driving the CD sensor 9 are generated by the clock generator 28 of the signal processing unit 12 and are output from the sensor board 1.
0 is input to the CCD sensors 16, 17, and 18 of each color.

Here, the processing of the analog processing circuit 29 and the digital processing circuit 30 will be described in more detail. Three
The image signal V is motivated by a driving pulse output from the clock generator 28 from the line type color CCD sensor 9.
RE, VRO, VGE, VGO, VBE, and VBO are output. In the pudding amplifier circuit 19, the output of the odd-numbered and even-numbered images of each color signal is adjusted to a certain level and multiplexed to generate image signals VR, VG, and VB. Further, the reset noise included in the signal is removed. Next, the image signals VR,
VG and VB are input to the sample and hold circuit 20.
In the sample hold circuit 20, the input image signal V
R, VG, and VB are each sampled by a sample pulse and held, whereby the image signal is converted into a continuous analog signal.
Of the dark output level is corrected. Then, the signal is amplified to the level of the reference voltage for A / D conversion by the amplifier circuit 22, and is converted into 8-bit digital data for each color by the A / D converter circuit 23. The image signals VR, VG, and VB converted into digital data are corrected in the shading correction circuit 24 for variations in the sensitivity of the CCD sensor 9 and uneven light distribution of the illumination system. Are corrected, and the γ correction circuit 26 performs γ correction processing. In the shading correction circuit 24, the reflected light of the white reference plate 15 illuminated by the halogen lamp 2 is read by the CCD sensor 9, and a predetermined density level based on the density of the white reference plate 15 is obtained. , The dispersion of the sensitivity of each CCD sensor 9 and the uneven light distribution of the illumination system are corrected.

In this manner, a digital image signal of 8 bits for each color can be obtained.
From the color table prepared in advance,
An image signal of an approximate color is output by a combination of the bit depths of G and B.

FIG. 5 is a model diagram of the RGB color table prepared in advance. Here, an image signal having a bit depth of 3 bits for each of RGB is prepared. An 8-bit address (00 to FF) is assigned to each cell of the table, and each cell is sequentially filled by combining the bit depths of 3 bits for each color of RGB. In this case, actually, a combination of image signals having six bit depths is obtained. In this case, 216 combinations of image signals are prepared in the color table. FIG. 6 shows an example in which a total of 234 kinds of image signal combinations can be prepared by preparing a 3-bit image signal with RBs each having 6 bit depths and G having 7 bit depths. This is an example of a color table in which the bit depth of the color to be emphasized is deeper than the example of FIG.

FIG. 7 is a block diagram showing the configuration of the approximate color conversion circuit 27. As shown in FIG.
Are two types of multiplication circuits 31 provided for each color RGB.
R, 31G, 31B, 32R, 32G, 32B, adder circuits 34R, 34G, 34B, lower 8 bit truncation circuits 36R, 36G, 36B, ROM 37, and look-up table 38. ROM37
Stores information of several types of color tables shown in FIGS. 5 and 6 described above, and a switching signal 3 input from the outside.
9 retrieves the information of one suitable color table into the look-up table 38. At the same time, the information 40 of the color table is transmitted to a subsequent device such as a personal computer or a printer.

In this case, the digital image signal of 8 bits for each color of RGB which has been subjected to the digital signal processing in FIG. 4 is multiplied by 4 times and 2 times by the multiplication circuits 31R, 31G, 31B, 32R, 32G and 32B, respectively. Thereafter, the multiplication circuits 31, 3 are added in the addition circuits 34R, 34G, 34B.
The result of multiplication for each of RGB by 2 is added. The lower 8 bits of the 11-bit signal obtained in this manner are retained, leaving the upper 3 bits.
The bits are truncated by the truncation circuits 36R, 36G, 36B. As a result, an image signal input with 8 bits becomes an image signal of 3 bits, in other words, an image signal of 6 types of bit depths. This image signal is stored in a lookup table 3
8 and outputs 8-bit address data of an image signal corresponding to the bit depth of each color of RGB from the color table called out from the ROM 37. Thus, the approximate color 8
The bit data is output to a personal computer or a printer and processed. Therefore,
If you do not need to capture image signals in full color,
It is possible to process RGB three colors collectively with 8 bits, and there is no increase in image capacity or processing time. In addition, it is possible to select an appropriate table from a plurality of color tables stored in advance by the switching signal 39 and execute the conversion process, so that the color process can be easily performed according to the color of the document image to be read or the user's preference. It can be carried out.

That is, in order to capture an image signal of an approximate color read by the image reading apparatus into a personal computer, information of a color table received from the approximate color conversion circuit 27 and an address of the color table are provided by driver software of a scanner. A process of creating data of an approximate color image from the data is performed. When it is not necessary to take in a full-color original image from the image reading apparatus in this manner, the image can be acquired with a small data capacity in a personal computer by previously converting the original image into an approximate color as described above.

On the other hand, when an image signal of an approximate color read by the image reading apparatus is transmitted to a printer and printed, information of a color table received from the approximate color conversion circuit 27 by a control unit such as a printer controller, Then, from the address data of the color table, an image signal of each color of RGB is returned to 3 bits, and processing such as color conversion is executed.

FIG. 7 shows a circuit corresponding to the color table shown in FIG. 5. In order to correspond to the color table shown in FIG. 6, a multiplying circuit 33 shown in FIG.
G is further provided, and the multiplication circuit 31G multiplies the G color signal input by 8 bits by 4 times, the multiplication circuit 32G by 2 times, and the multiplication circuit 33G by 1 time. The result of multiplication by these multiplication circuits 31G, 32G, 33G is added to an addition circuit 35.
To obtain 11-bit data. Then, the lower 8 bits are truncated by the lower 8 bits truncation circuit, and the 8-bit address data of the image signal corresponding to the bit depth of each color of RGB is output from the color table called from the ROM 37 as described in FIG. Therefore, in such a case, if a 1-times multiplication circuit is separately provided and switched to be used when necessary, it is possible to easily perform processing at a bit depth corresponding to each color.

[0024]

As described above, according to the first aspect of the present invention, when the subsequent image processing means does not need to process an image in full color, the image signal output from the digital processing circuit is approximated. Since the image signal can be converted into a color image signal and output, the image processing means at the subsequent stage can perform image processing with a small capacity. In particular, when it is not necessary to perform full-color image processing in a personal computer or a printer, the subsequent processing device requires a small storage capacity and a high processing speed.

According to the second aspect of the present invention, since an appropriate table is selected from a plurality of color tables stored in advance and the conversion process is executed, it is easy to match the color of the original image to be read or the user's preference. Color processing.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an internal structure of an image reading apparatus according to an embodiment of the present invention.

FIG. 2 shows a three-line CCD used in the embodiment.
It is a front view of a sensor.

FIG. 3 shows a three-line CCD used in the embodiment.
FIG. 3 is a block diagram illustrating an internal structure of a sensor.

FIG. 4 is a block diagram illustrating a configuration of a signal processing unit according to the embodiment.

FIG. 5 is a model diagram of an RGB color table prepared in advance in the approximate color conversion circuit in FIG. 4;

6 is a model diagram showing an example of another RGB color table prepared in advance in the approximate color conversion circuit in FIG. 4;

FIG. 7 is a block diagram illustrating a configuration of an approximate color conversion circuit in FIG. 4;

FIG. 8 is a block diagram illustrating another configuration of the approximate color conversion circuit in FIG. 4;

[Explanation of symbols]

 9 3 line type CCD color sensor 12 signal processing section 16 R CCD sensor 17 G CCD sensor 18 B CCD sensor 19 preamplifier circuit 20 sample hold circuit 21 black level correction circuit 22 amplification circuit 23 A / D conversion circuit 24 shading correction circuit 25 memory 26 γ correction circuit 27 Approximate color conversion circuit 28 Clock generator 29 Analog processing circuit 30 Digital processing circuit 31, 32, 33 Multiplication circuit 34, 35 Addition circuit 36 Lower 8 bits truncation circuit 37 ROM 38 Lookup table 39 Table switching signal 40 Color Table information

Claims (2)

[Claims] 1. An image reading apparatus for reading reflected light from a document image by a photoelectric conversion element, converting the reflected light into an electric signal, and performing a predetermined process on the converted electric signal to obtain a digital image signal. An analog processing circuit that processes the electrical signal converted by the conversion element in an analog manner, an analog / digital conversion circuit that converts an image signal output from the analog processing circuit into a quantized signal, and an analog / digital conversion circuit An image, comprising: a digital processing circuit that digitally performs image processing on a quantized image signal; and a conversion circuit that converts an image signal output from the digital processing circuit into an image signal of an approximate color. Reader. 2. The image reading apparatus according to claim 1, wherein said conversion circuit selects an appropriate table from a plurality of color tables stored in advance and executes a conversion process.