JP3828331B2 - Image reading apparatus and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image processing apparatus and an image forming apparatus that perform digital image processing by inputting a document image to a solid-state imaging device using a reading optical system.
[0002]
[Prior art]
As described in Japanese Patent Application Laid-Open No. 9-98152, when data processing is performed in synchronization with a clock signal in a microprocessor or the like, the clock signal is susceptible to EMI (electromagnetic interference), so the frequency of the clock signal A proposal has been made to reduce the vibration width by diffusing.
[0003]
[Problems to be solved by the invention]
In an image reading apparatus such as a digital copying machine, a series of processing such as analog processing, digital processing, and digital image processing of the output of a solid-state imaging device is required to be performed at high speed in synchronization with a clock signal. The frequency of the signal and its radiation level are very high. In the case of processing a color image, the amount of data is tripled (8 or 10 bits × 3), so that the EMI radiation level is further increased.
[0004]
The EMI radiation level must be within the limits of each country (for example, VCCI in Japan and FCC in the United States). For this reason, it is necessary to take measures on the part structure such as multilayering the printed circuit board, inserting a ferrite core in the connection cable, and reinforcing the shield of the housing, and the cost increases.
[0005]
An object of the present invention is to keep the EMI radiation level within a regulation value without taking measures on the component structure as described above.
[0006]
Furthermore, an object of the present invention is to suppress the occurrence of image noise.
[0007]
[Means for Solving the Problems]
The image processing apparatus according to claim 1, wherein a document image is input to a solid-state image sensor by a reading optical system, and an image data signal output from the solid-state image sensor in synchronization with a clock signal generated by a clock signal generation unit. an image processing apparatus that performs image processing for, a clock signal spreading means for spreading a frequency of the pre-Symbol clock signal, the clock signal spreading means, the frequency of the clock signal spread in the process of digital image processing, It is characterized by not diffusing in processing steps other than digital image processing .
[0008]
Therefore, since the frequency of the clock signal is diffused by the clock signal diffusing means, it is possible to keep the EMI radiation level within the regulation value without taking measures on the component structure. In the image processing process, the frequency of the clock signal is not diffused in a process that has a high contribution rate to the generation of image noise, and the frequency of the clock signal can be diffused in other processes. It is possible to keep the EMI radiation level within the regulation value while suppressing the above.
[0009]
According to a second aspect of the present invention, in the invention according to the first aspect, the clock signal spreading means spreads the frequency of the clock signal in the process of processing the image data signal that has a low contribution rate to image noise generation. It is characterized by that. In the process where the contribution rate to image noise generation is low, it is possible to keep the EMI radiation level within the regulation value by spreading the frequency of the clock signal.
[0010]
According to a third aspect of the present invention, in the first aspect of the invention, the clock signal spreading means does not spread the frequency of the clock signal related to the process of outputting the image data from the solid-state imaging device. Features. In the process where the contribution rate to image noise generation is low, it is possible to keep the EMI radiation level within the regulation value by spreading the frequency of the clock signal.
[0011]
According to a fourth aspect of the present invention, in the invention according to the first aspect, the clock signal spreading means does not spread a frequency of the clock signal related to a process of outputting image data from the solid-state imaging device, and The frequency of the clock signal related to digital image processing is spread. It is possible to spread the frequency of the clock signal in a process that has a high contribution rate to the generation of image noise, and to spread the frequency of the clock signal in the other processes. It is possible to keep the level within the regulation value.
[0012]
An image forming apparatus according to a fifth aspect includes the image processing apparatus according to any one of the first to fourth aspects, and a printing unit that outputs image data read by the image processing apparatus.
[0014]
Therefore, since the frequency of the clock signal is diffused by the clock signal diffusion means when reading the document image, it is possible to keep the EMI radiation level within the regulation value without taking measures on the part structure. This makes it possible to improve the image quality during printing.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described with reference to FIGS. 1 is a longitudinal front view showing a schematic configuration of the image reading apparatus, FIG. 2 is a block diagram showing an electrical connection configuration, and FIG. 3 is a graph showing a waveform of a clock signal and a waveform obtained by spreading the frequency.
[0016]
In FIG. 1, a contact glass 3 and a pressure plate (not shown) for pressing the document 4 on the contact glass 3 are provided on the upper surface of the housing 2 of the image reading apparatus 1. A white reference plate 5 for shading correction is provided near one end of the contact glass 3.
[0017]
In addition, a reading optical system 7 for inputting a document image to a CCD 6 that is a solid-state imaging device is provided inside the housing 2. The reading optical system 7 includes a halogen lamp 9 and a first mirror 10 mounted on the first traveling body 8, a second mirror 12 and a third mirror 13 mounted on the second traveling body 11, and a front surface of the CCD 6. It consists of the converging lens 14 which faces. The first traveling body 8 and the second traveling body 11 are provided so as to travel in a one-to-two relationship with a motor (not shown). That is, in the process of traveling the first traveling body 8 and the second traveling body 11 in the direction of arrow A, the image of the document 4 on the contact glass 3 is illuminated by the halogen lamp 9, and the reflected image of the document 4 is the first, The beam is deflected by the second and third mirrors 10, 12, and 13, converged by the convergence lens 14, and input to the CCD 6.
[0018]
The CCD 6 can read an image color-separated into R (red), G (green), and B (blue). The CCD 6 is provided on the sensor substrate 15. The sensor substrate 15 is connected to the signal processing substrate 17 by a cable 16.
[0019]
As shown in FIG. 2, an analog processing unit 18, an A / D converter 19, and a digital image processing unit 20 are sequentially connected to the CCD 6. A crystal oscillator (hereinafter referred to as OSC) 21 serving as a clock signal generation unit that generates a reference clock signal is a spread spectrum clock generation circuit (hereinafter referred to as SSCG) 22 serving as clock signal spreading means for spreading the frequency of the clock signal. Are connected to the CCD 6, the analog processing unit 18, the A / D converter 19, and the digital image processing unit 20 through the timing circuit 23.
[0020]
Next, processing of the image data signal output from the CCD 6 will be described. Since the operation for inputting the image of the document 4 to the CCD 6 has already been described, a description thereof will be omitted. The image data signal output from the CCD 6 is clamped, sampled and held by the analog processing unit 18, converted into an 8-bit digital signal by the A / D converter 19, and subjected to predetermined image processing by the digital image processing unit 20. And output to a printer unit (not shown).
[0021]
In this series of image processing, the timing signal from the timing circuit 23 given to each block (CCD 6, analog processing unit 18, A / D converter 19, digital image processing unit 20) is a clock signal output from the OSC 21. Is a signal obtained by spreading the frequency of the signal by the SSCG 22.
[0022]
The clock signal output from the OSC 21 has a narrow spectrum distribution width and a high EMI radiation level as shown by a solid line in FIG. On the other hand, the signal spread by the SSCG 22 has a wide spectrum distribution width and a low EMI radiation level by spreading the original clock signal with a predetermined spreading factor (for example, ± 1%) as shown by a dotted line in FIG. .
[0023]
Therefore, it is possible to keep the EMI radiation level within the regulation value at a low cost without taking measures on the component structure.
[0024]
Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those of the above-described embodiment are denoted by the same reference numerals, and description thereof is also omitted.
[0025]
In the present embodiment, a process with a high contribution rate to image noise generation, specifically, a process of outputting an image data signal from the CCD 6, a process of processing the image data signal by the analog processing unit 18, and an A / D converter 19 In the process of converting the image data signal into the digital signal, the frequency of the clock signal is not spread, and in the other processing steps in the digital image processing unit 20, the OSC 21 is used to spread the frequency of the clock signal. Are connected to the CCD 6, the analog processing unit 18, and the A / D converter 19, and are connected to the digital image processing unit 20 through the SSCG 22 and the timing circuit 23.
[0026]
In such a configuration, the process from when the image data signal is output from the CCD 6 to the conversion of the image data signal into a digital signal is a process that has a high contribution rate to the generation of image noise. By suppressing the generation of image noise without diffusing and diffusing the frequency of the clock signal related to subsequent digital image processing, the EMI radiation level can be kept within the regulation value.
[0027]
Next, an example of an image forming apparatus including the image reading apparatus 1 will be described with reference to FIG. Although the image forming apparatus in the present embodiment is a digital copying machine C, the image forming apparatus provided with the image reading apparatus 1 includes a facsimile in addition to the copying machine.
[0028]
As shown in FIG. 5, the above-described image reading apparatus 1 is provided on the upper part of the main body 100 of the digital copying machine C. A printing unit 101 is provided inside the main body 100. The printing unit 101 uniformly charges the surface of the photoconductor 103 with the charger 102, develops the electrostatic latent image written on the charged portion with the optical writing device 104 with the developing unit 105, and develops the developed image. This is a known configuration in which the image is transferred onto a sheet by a transfer belt 106, the transferred image is fixed by a fixing device 107, and the surface of the photosensitive member 103 is cleaned by a cleaning unit 108 in order to form a next image. The optical writing device 104 is a deflection scanning type that forms an electrostatic latent image by irradiating the photosensitive member 103 with laser light modulated based on the image data read by the image reading device 1 described above. However, a line-type optical writing unit that includes a large number of light-emitting elements along the axial direction of the photoconductor 103 and selectively emits the light-emitting elements to form an electrostatic latent image on the surface of the photoconductor 103 is used. It doesn't matter.
[0029]
In addition, the digital copying machine C according to the present embodiment includes known paper feeding units 109, 110, and 111, and conveys paper from these paper feeding units 109, 110, and 111 to a paper discharge unit (paper discharge tray) 112. In the passage 113, sheet conveying members 114, 115, 116, and 117 that convey the sheet S are arranged. Therefore, an image is printed by the printing unit 101 in the process in which the sheet S fed from one of the selected sheet feeding units 109, 110, and 111 is guided to the sheet conveyance path 113 and discharged to the sheet discharge unit 112. Is done.
[0030]
【The invention's effect】
According to the image processing apparatus according to claim 1, wherein, in the image processing apparatus that performs image processing on the image data signal output from the solid-state imaging device in synchronization with a clock signal generated by a clock signal generator, before A clock signal diffusing means for diffusing the frequency of the clock signal, diffusing the frequency of the clock signal in a processing process in digital image processing, and not diffusing in a processing process other than digital image processing; Can be contained within. In addition, the EMI radiation level can be kept within the regulation value without taking measures on the part structure.
[0031]
According to the image processing apparatus of the second aspect, in the invention of the first aspect, the frequency of the clock signal is diffused in the process of processing the image data signal having a low contribution rate to the generation of the image noise. In the process where the contribution rate is low, the frequency of the clock signal is diffused to suppress the generation of image noise, and the EMI radiation level can be kept within the regulation value.
[0032]
According to a third aspect of the present invention, in the first aspect of the present invention, since the frequency of the clock signal related to the process of outputting the image data from the solid-state image sensor is not diffused, image noise is generated. In the process where the contribution ratio is low, the frequency of the clock signal is diffused to suppress the generation of image noise, and the EMI radiation level can be kept within the regulation value.
According to an image processing apparatus according to claim 4, in the invention according to claim 1, the frequency of the clock signal related to the process of outputting the image data from the solid-state imaging device is not diffused, and is related to the digital image processing. Since the frequency of the clock signal is spread, it is possible to spread the frequency of the clock signal in other processes without spreading the frequency of the clock signal in a process that has a high contribution rate to image noise generation. It is possible to keep the EMI radiation level within the regulation value while suppressing the generation of image noise.
[0033]
An image forming apparatus according to a fifth aspect includes the image processing apparatus according to any one of the first to fourth aspects, and a printing unit that outputs image data read by the image processing apparatus.
[Brief description of the drawings]
FIG. 1 is a longitudinal front view showing a schematic configuration of an image reading apparatus according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing an electrical connection configuration.
FIG. 3 is a graph showing a waveform of a clock signal and a waveform obtained by spreading the frequency.
FIG. 4 is a block diagram showing an electrical connection configuration in a second embodiment of the present invention.
FIG. 5 is a longitudinal front view showing an example of an image forming apparatus equipped with an image reading apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Image reader 4 Document 6 Solid-state image sensor 7 Reading optical system 21 Clock signal generation part 22 Clock signal spreading | diffusion means 101 Printing part S Paper

Claims (5)

In an image processing apparatus that inputs a document image to a solid-state imaging device by a reading optical system and performs image processing on an image data signal output from the solid-state imaging device in synchronization with a clock signal generated by a clock signal generation unit ,
Clock signal spreading means for spreading the frequency of the clock signal;
The clock signal spreading means spreads the frequency of the clock signal in a process in digital image processing, and does not spread in a process other than digital image processing.
The image processing apparatus according to claim 1.   The clock signal spreading means spreads the frequency of the clock signal in the process of processing the image data signal that has a low contribution rate to image noise generation.
  The image processing apparatus according to claim 1.   The clock signal spreading means does not spread the frequency of the clock signal related to the process of outputting image data from the solid-state imaging device,
  The image processing apparatus according to claim 1.   The clock signal spreading means does not spread the frequency of the clock signal related to the process of outputting image data from the solid-state imaging device, but spreads the frequency of the clock signal related to the digital image processing.
  The image processing apparatus according to claim 1. An image forming apparatus comprising: the image processing apparatus according to claim 1; and a printing unit that outputs image data read by the image processing apparatus.

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