JPH04115661A - Color picture reading method and color picture forming device - Google Patents

Abstract

PURPOSE:To attain good color reproduction by cutting off the light in IR range when a color image sensor with a color filter arranged on a light receiving element front face is made to receive the reflected light of an original. CONSTITUTION:When a color mode is selected by the operation of a color/ monochrome selecting key 43, an IR cutting filter 21 is interposed on an optical path and an IR component is made to be cut. The IR cut-off filter 21 possesses a property to cut light with >=700nm wave length (range (a)). When cut-off wave length is more than 700nm, the light more than 750nm (range (b)) is cut surely on the design of the filter. The light unnecessary for color reproduction is not made incident to a linear sensor 24 and an S/N ratio is improved by the cutting of the IR light in this way. Thus, a good color picture can be obtained while maintaining the color reproducing area broadly.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a color image forming apparatus that has a color linear image sensor and an infrared cut filter device in an image reading section and superimposes a color toner image on an image forming body. It is related to.

(Background of the Invention) A color image forming apparatus, particularly a digital color image forming apparatus, is generally configured with a color image processing system such as an image reading section and an image writing section. Pass the optical image of the surface through an imaging lens system for reading.

Furthermore, the blue color provided on the linear image sensor.

A method has been proposed in which transmitted light from a red monochromatic light filter is imaged on a solid-state imaging device such as a CCD, and image data corresponding to each light image is input to the image writing section.

In this color image forming apparatus, for example, blue and green.

The light image that has passed through each red monochromatic light filter is received by a CCD, and after signal processing such as shape ink correction, masking processing, and gradation correction processing, it is processed into Y (yellow), 1M (magenta), and C (cyan). , BK (black), and based on this image data, the image writing section sequentially forms electrostatic latent images on the image forming body, and then M (magenta).
, a developing device that reproduces a color image by superimposing toner images of the necessary parts with C (cyan) toner to form a color toner image, and then loads BK (black) toner based on the black image data. A toner image is formed on an image forming body. A color image is formed by separating, transferring, and fixing the color toner images superposed in this way onto a transfer material.

(Problems to be Solved by the Invention) The inventors of the present application have conducted various studies on image forming apparatuses using the above-mentioned color image sensor. As a result,
The following problems were clarified.

(1) Reading output by color linear sensor (R.

Of the light transmitted through each of the G and B filters, light of 700 nm or more acts as noise and reduces the S/N ratio of each signal. Furthermore, the color correction range due to these is narrow and color reproducibility is poor.

(2) In the monochrome mode, recording is normally performed using a signal from a green (G) filter, but in this case, the reproducibility of documents printed in greenish colors is poor due to the influence of the above-mentioned noise.

This problem will be explained in more detail using FIG. 5.

When reading a color original with a color image sensor, R
, G, and B filters is proportional to the product of the spectral characteristics of the light source and optical system and the sensor sensitivity characteristics including the color filter. Of this sensor output, wavelengths of 700 nm or more are unnecessary for color reproduction.

However, as shown in FIG. 5, the spectral sensitivity characteristics of the sensor (CCD), including the transmission characteristics of the color filter, have high sensitivity in this infrared region of wavelengths of 700 nm or more. In particular, R, G at 750 nm to 820 nm
, B both have high sensitivity, and the outputs of each sensor are equivalent to gettinga, and the spectral sensitivity ratio becomes small.

That is, the output IR+IC+1 of each R, G, and B cell
, becomes as follows.

Ia = IR (V) + IR (ir) I6 = Ic (V) + Ic (ir) 1B-1
a (V) + Ia (ir) However, IR (V),
IG (V) and IB (V) are outputs proportional to the sensitivity of visible light components, and IR (i r) and IG (i
r), IB (i r) is an output proportional to the sensitivity of the infrared light component. Therefore, when pursuing accuracy in image reading, when the light source and optical system have infrared light as their spectral characteristics, lR (ir), IG (ir), 1B
The existence of (ir) cannot be ignored.

The present invention has been made in view of these problems, and its purpose is to provide a color image reading method capable of obtaining a good color image with a wide color reproduction area, and to provide a method for reading an original. An object of the present invention is to provide a color image forming apparatus that can satisfactorily reproduce color/monochrome images of any type.

(Means for Solving the Problems) The present invention provides an infrared cut filter interposed in an optical system,
The infrared light is cut off before the sensor receives it, and the infrared components are I, l (ir), and Ic (ir).

This makes Ia(ir) almost zero.

(Function) By cutting out infrared light unnecessary for color reproduction, S/N is improved.
The ratio is improved, and good color image reproduction becomes possible.

(Example) Next, an example of the present invention will be described with reference to the drawings.

(1) Overall configuration FIG. 1 is a diagram showing the overall configuration of a color copying machine to which the present invention is applied.

In this embodiment, the light source 20. An infrared cut filter 21 supported by a pedestal 22. Lens barrel 23. A color image reading section including a color linear image sensor 24 and a control section 25
and a light source (semiconductor laser) 31 for image writing,
Developing units 34 to 37 for each color of Y, M, C, and BK, a photosensitive drum 32, a charging electrode 33, a transfer pole 39, and a separation pole 40
, a paper feeding section 38 , a fixing/discharging section 41 , a cleaning device 42 , and a color/monochrome selection key 43 .

The control section 25 includes a motor control means 26, two A/D converters 27 and 28, a signal processing means 29, and a writing light source driving means 30.

(2) Configuration and operation of the color linear image sensor 24 The color linear image sensor 24 used in this embodiment has a line sensor 1 as shown in FIG.
Red and blue row sensors 2 and photo storage gate 3
．． 5, a one-line delay analog memory 6 for aligning the reading position of each column, a shift gate 4.7, a CCD shift register 8 for red and blue, a peripheral CCD shift register 9, an output gate 10, Output buffer 11.1
2. As shown, the red and blue pixels are arranged alternately, and the recording pixels are shifted from the red and blue pixels by 1/2 pixel. In the figure, B1 to B32 are black reference pixels, and D1 to D8 are dummy invalid pixels. Note that the reason why one line of recording pixels is prepared is that green has a strong influence on the human eye and affects the reproduction accuracy of luminance information.

The charges stored by scanning the optical system (not shown) are read out at the timing shown in FIG. 4.

That is, first, φSC2 goes high and the charges in the analog memory 6 are transferred to the red and blue CCD shift registers 8, and then φ7 and φ.

1 becomes high level, and the transfer of the red and blue charges to the analog memory 6 and the transfer of the line column charges to the edge CCD shift register 9 are executed.

Next, charges are sequentially transferred in the horizontal direction (
(to the left), and the signal O8 of each color is shifted in synchronization with φR.
I, OS2 is output. 052 is the signal of one line before.

(3) Processing and writing of signals from the sensor 24 Two systems of signals obtained from the color linear image sensor 24 (green pixel corresponding signal and red and blue pixel corresponding signal) are respectively sent to the A/D in the control unit 25. The data is converted into digital data by converters 27 and 28, and is input to the signal processing means 29.

In the color linear image sensor 24, there is a difference in reading density between the red and blue pixels and the recording pixel, and if the output signal of each sensor row is processed as it is, the reproducibility will deteriorate.
You can't expect high image quality. Therefore, it is necessary to combine the output signals of each pixel into one data. The signal processing means 29 first performs shading correction, and then performs processing to create the above-mentioned set of data. This process is
For example, the first green pixel is a combination of the first red pixel and the first blue pixel, and the second green pixel is the second red pixel and the first blue pixel. It's about getting a match. As a result, the reading density of recording pixels is not impaired. Note that a set of data may be obtained using linear interpolation.

Thereafter, color signal processing is performed, and the processed signal is sent to the driving means 30, which drives the writing light source 31 to write an image.

The writing light from the writing light source 32 is incident on the photosensitive drum 33 whose surface is charged to a predetermined potential by the charging electrode 33, and as a result, an electrostatic latent image is formed.

Subsequently, overlapping development of each color is performed using the developing units 34 to 37, and a color toner image is formed on the photoreceptor drum 32. This color toner image is transferred onto a transfer paper supplied from a paper feed section 38, and this transfer paper is subjected to a fixing process in a fixing/discharging section 41 and then discharged outside the machine. On the other hand, the cleaning device 4 cleans the surface of the photoreceptor drum 32.
2, and is recharged, after which the next image formation is started.

As shown in FIG. 2, the infrared cut filter 21 is
It is housed in a filter frame A, and is securely held so as not to cause optical distortion by a common presser plate having holes in the effective area of the filter surface. The lower surface of the filter frame A engages with a rail on the upper surface of the pedestal 22, and is attached so that the infrared cut filter 21 can be slid in the filter arrangement direction.

Further, a rack R located at the lower end of the filter frame A is engaged with a pinion P on the shaft of a servo motor M built in the mount 22. The operation of the motor M is controlled by a motor control means 26, and the rotation of this motor M causes the infrared cut filter 21 to slide and be placed on the optical path of the reflected light from the original (on the optical axis of the lens barrel 23). , or it can be evacuated from the optical path and not intervene.

In this embodiment, when the color mode is selected by operating the color/monochrome selection key 43, the infrared cut filter 21 is interposed on the optical path to cut the infrared component.

This infrared cut filter 21, as shown in FIG.
It has the property of cutting light with a wavelength of 700 nm or more (area A). Due to the design of the filter, if the cutoff wavelength is 700 nm or more, it must be at least 750 nm or more (area A).
to ensure that the light is cut out.

By cutting such infrared light, unnecessary light for color reproduction will not be incident on the linear sensor 24, and the S/N will be reduced.
ratio is improved. This makes it possible to obtain a good color image while maintaining a wide color reproduction area.

In this embodiment, a case where the present invention is applied to a color copying machine has been described, but the present invention is not limited to this, and can also be applied to a color facsimile, a color scanner, etc. Furthermore, when copying a document with edges in monochrome mode, reproducibility can be improved by interposing the infrared cut filter 21 in the optical path to cut out infrared light.

The presence/absence of the infrared cut filter 21 can be arbitrarily set by changing the control program of the motor control means 2B.

(Effects of the Invention) As explained above, according to the present invention, by interposing an infrared cut filter in the optical system and cutting infrared light before the sensor receives the light as necessary, the following effects can be achieved. is obtained.

(1) Infrared light unnecessary for color reproduction is removed, the S/N ratio is improved, and good color image reproduction is possible while maintaining a wide color reproduction range.

(2) It is possible to provide a color image forming apparatus that can reproduce color/monochrome images well regardless of the type of original.

(3) Furthermore, it has a recording pixel row for one line and a pixel row in which red and blue pixels are arranged alternately, and the recording pixels and the red and blue pixels are arranged 1/2 pixel apart from each other. By using a color linear image sensor,
It is possible to reproduce high-quality color images without impairing the reading density of recording pixels and suppressing the occurrence of moiré. Also, the linear image sensor only needs 2 lines,
The configuration is also simplified.

(4) With these, it is possible to improve the performance of color copying machines and the like while keeping costs down.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the overall configuration of an embodiment of the present invention, FIG. 2 is a diagram showing the configuration of an infrared cut filter 21 and its peripheral mechanism, and FIG. 3 is a diagram showing the configuration of an infrared cut filter 21 and its peripheral mechanism. Figure 4 shows the configuration of the CCD linear image sensor shown in Figure 3.
FIG. 5 is a timing chart for explaining the operation of the D linear image sensor, and is a diagram showing the spectral sensitivity characteristics of the CCD linear image sensor including the transmission characteristics of the color filter. 1... Sensors in line rows 2... Sensors in red and blue columns 3.5... Photostorage gate 6... 1 line delay analog memory for aligning the reading position of each column 4.7.・Shift Kate 8... CCD shift register 9 for red and blue・C for line
CD shift register 10... Output buffer -1 11.12... Output buffer 20... Light source 21... Infrared cut filter 22... Mount 23... Lens barrel 24... CCD linear image Sensor 25...Control unit 26...Motor control means 27, 28...A/D converter 29...Signal processing means 30...Motor drive means 31...Writing light source (semiconductor laser) 32 ...Photosensitive drum 33...Charging electrodes 34-37...Y, M, C, BK color developing device 38...
Paper feed section 39...Transfer pole 40...Separation pole 41...
- Fixing and paper ejection section 42... Cleaning device 43... Color/monochrome selection key A... Filter frame D... Presser spring plate R... Rack P... Binion M... Servo motor

Claims (9)

[Claims] (1) A color image reading method characterized in that when a color image sensor having a color filter disposed in front of a light receiving element receives reflected light from a document, light in an infrared region is substantially cut. (2) The color image reading method according to claim 1, wherein light having a wavelength of 700 nm or more is substantially cut. (3) The color image reading method according to claim 1, wherein light having a wavelength of 750 nm or more is substantially cut. (4) The color image reading method according to claim 1, wherein the color filter is provided for each unit cell of the light receiving element. (5) The color image reading method according to claim 1, wherein the color filters are red, green, and blue filters, and the arrangement pitches of the color filters are different from each other. (6) A color image reading device (24) using a color image sensor in which red (R), green (G), and blue (B) color filters are arranged at different pitches, and from the color image reading device (24). Based on the color recording signal obtained by processing the output color image signal, a color toner image is created on the photoreceptor using toner of each color: yellow (Y), magenta (M), cyan (C), and black (BK). a color image recording device (31, 32, 34, 35, 36, 37) that forms a color image sensor; and a control device () that sets an infrared cut filter (21) in front of the color image sensor depending on monochrome mode or color mode. 26) A color image forming apparatus comprising: (7) The color image forming apparatus according to claim 6, wherein the infrared cut filter (21) has a characteristic of cutting light having a wavelength of 700 nm or more. (8) The color image forming apparatus according to claim 6, wherein the infrared cut filter (21) has a characteristic of cutting light having a wavelength of 750 nm or more. (9) The color image forming apparatus according to claim 6, wherein the infrared cut filter (21) is set in a color mode.