Signal processing apparatus and image forming apparatus

Abstract

A signal processing apparatus comprising: an optical sensor for outputting a detection signal by detecting a surface of a recording medium on which a correction image is to be formed; and a control section configured to obtain a detection signal of the surface of the recording medium with the correction image from which a dominant frequency component has been deleted by making reverse frequency analysis of an analysis signal that has been obtained by making a frequency analysis of a detection signal outputted by the optical sensor detecting the surface of the recording medium on which the correction image it formed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram representing the structure of the printing process in a color image forming apparatus 100;

FIG. 2 is a diagram representing the structure of the intermediate transfer member 6 with a correction image being formed, and optical sensors 12A and 12B;

FIG. 3 is a block diagram representing the functional structure of the data processing in a color image forming apparatus 100;

FIG. 4 is a diagram representing the structure of the image writing unit 3Y;

FIG. 5 is a diagram representing the structure of controlling the color image forming apparatus 100;

FIG. 6 is a flowchart representing the process of baseline measurement;

FIG. 7 (a) is a diagram representing the ideal output waveform of the optical sensors 12A and 12B after baseline correction;

FIG. 7 (b) is a diagram representing an example of the practical output waveform of the optical sensors 12A and 12B after baseline correction;

FIG. 8 is a diagram representing an example of the waveform of the baseline sampling data after frequency analysis;

FIG. 9 is a flowchart representing the process of measuring the correction image;

FIG. 10 (a) is a diagram representing the ideal output waveform of the optical sensors 12A and 12B at the time of detecting the registration mark CR;

FIG. 10 (b) is a diagram representing the frequency-analyzed waveform of the ideal sampling data at the time of detecting the registration mark CR;

FIG. 11 (a) is a diagram representing an example of the practical output waveform of the optical sensors 12A and 12B at the time of detecting the registration mark CR;

FIG. 11 (b) is a diagram representing the frequency-analyzed waveform of the practical sampling data at the time of detecting the registration mark CR;

FIG. 12 is a diagram representing an example of detecting the dominant frequency component from the sampling data of the correction image;

FIG. 13 (a) is a diagram representing the binarized pattern detection signal;

FIG. 13 (b) is a diagram representing an example of determining the center position of the pattern detection signal having been detected by the optical sensors 12A and 12B;

FIG. 14 (a) is a diagram representing the gain with respect to frequency in a low-order FIR filter;

FIG. 14 (b) is a diagram representing the phase component with respect to frequency in a low-order FIR filter;

FIG. 15 (a) is a diagram representing the gain with respect to frequency in a high-order FIR filter; and

FIG. 15 (b) is a diagram representing the phase component with respect to frequency in a high-order FIR filter.

Claims

1. A signal processing apparatus comprising: an optical sensor for outputting a detection signal by detecting a surface of a recording medium on which a correction image is to be formed; anda control section configured to conduct control steps of:having said optical sensor to detect the surface of the recording medium without the correction image being formed thereon;making a frequency analysis of a first detection signal outputted from said optical sensor detecting the surface of the recording medium without the correction image being formed thereon;extracting a dominant frequency-corresponding to the frequency component dominant over other values from a first analysis signal obtained by making the frequency analysis of the first detection signal;having said optical sensor to detect the surface of the recording medium with the correction image formed thereon;making a frequency analysis of a second detection signal outputted from said optical sensor detecting the surface of the recording medium with the correction image being formed thereon;deleting the component of the dominant frequency from a second analysis signal obtained by making the frequency analysis of the second detection signal; andobtaining a detection signal wherein the dominant frequency component has been deleted by making reverse frequency analysis of the second analysis signal from which the dominant frequency component has been deleted.

2. The signal processing apparatus according to claim 1, wherein said control section is configured to conduct the extracting step by extracting dominant frequency corresponding to noise due to a scratch or dust on the intermediate transfer member from the first analysis signal.

3. The signal processing apparatus according to claim 1, wherein the correction image includes density patch for density correction in an image forming operation and wherein said control section calculates density information in accordance with a detection signal obtained by detecting the density patch wherein the dominant frequency has been deleted from the detection signal.

4. The signal processing apparatus according to claim 1, wherein the correction image includes registration mark for registration correction in an image formation and wherein said control section calculates position information of the registration mark in accordance with a detection signal obtained by detecting the registration mark wherein the dominant frequency has been deleted from the detection signal.

5. The signal processing apparatus according to claim 1, wherein said control section calculates correction information for correcting image formation in accordance with the detection signal wherein the dominant frequency component has been deleted.

6. The signal processing apparatus according to claim 1, wherein the recording medium is an intermediate transfer member.

7. An image forming apparatus comprising: an image forming section for forming an image on a recording medium; anda signal processing apparatus,wherein the signal processing apparatus including:an optical sensor for outputting a detection signal by detecting a surface of the recording medium on which a correction image is to be formed by said image forming section; anda control section configured to conduct control steps of:having said optical sensor to detect the surface of the recording medium without the correction image being formed thereon;making a frequency analysis of a first detection signal outputted from said optical sensor detecting the surface of the recording medium without the correction image being formed thereon;extracting a dominant frequency corresponding to the frequency component dominant over other values from a first analysis signal obtained by making the frequency analysis of the first detection signal;having said optical sensor to detect the surface of the recording medium with the correction image formed thereon;making a frequency analysis of a second detection signal outputted from said optical sensor detecting the surface of the recording medium with the correction image being formed thereon;deleting the component of the dominant frequency from a second analysis signal obtained by making the frequency analysis of the second detection signal; andobtaining a detection signal wherein the dominant frequency component has been deleted by making reverse frequency analysis of the second analysis signal from which the dominant frequency component has been deleted.

8. The image forming apparatus according to claim 7, wherein the correction image includes density patch for density correction in an image forming operation and wherein said control section calculates density information in accordance with a detection signal obtained by detecting the density patch wherein the dominant frequency has been deleted from the detection signal and wherein said image forming section forms an image in accordance with the calculated density information.

9. The image forming apparatus according to claim 7, wherein the correction image includes registration mark for registration correction in an image formation and wherein said control section calculates position information of the registration mark in accordance with a detection signal obtained by detecting the registration mark wherein the dominant frequency has been deleted from the detection signal and wherein said image forming section forms an image in accordance with the calculated position information.

10. The image forming apparatus according to claim 7, wherein said control section calculates correction information for correcting image formation in accordance with the detection signal wherein the dominant frequency component has been delete and wherein said image forming section forms an image in accordance with the calculated correction information.

11. The image forming apparatus according to claim 7, wherein the recording medium is an intermediate transfer member.