Black point correcting method for sensor, and colour image forming deivce
A color image and sensor technology, applied in the sensor field, can solve the problems of reduced information accuracy, reduced accuracy of color stabilization control of image forming devices, inability to stabilize shading correction, etc.
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Embodiment 1
[0027] Hereinafter, embodiments of the "sensor shading correction method" of the present invention will be described with reference to the drawings. In addition, the color mark detection for color stabilization following shading correction will be described. In addition, in the case of a sensor that detects color, because not only the intensity of the light or the sensitivity of the sensor, but also the variation of the wavelength is the cause of the error, so here, the difference in the sensitivity of the sensor, the difference in the light-emitting characteristics of the light source, and the sensor detect The amount of light in the position is not uniform, the difference in the spectral transmittance of the filter, etc. are collected together to be corrected and defined as black point correction.
[0028] FIG. 1A shows an example of the color patch used in the calibration, and FIG. 1B shows the flow of the calibration. FIG. 2 shows the relationship between the toner amount of t...
Embodiment 2
[0052] In the case of detecting the reflected light from the dark K toner patch 101 described in the first embodiment, the signal level is small compared with the case of detecting the reflected light from the normal color patch, and it is likely to be subject to quantization errors during AD conversion. The problem of worsening S / N. Here, the "shading correction method" to improve this problem will be explained.
[0053] First, as shown in FIG. 8A, in the case of a type of sensor that performs IV conversion and readout of the photocurrent generated in a photodiode or phototransistor, the characteristic is that it detects concentration during normal color mark detection and during calibration. Change the readout gain at the time of the K toner patch. FIG. 3 shows a circuit illustrating the present embodiment for a pixel corresponding to a filter (here, R). The resistance value for IV conversion can be switched according to the control signal SEL. The anode side of the photodiode 2...
Embodiment 3
[0060] As the sensor, in the case of using a sensor such as a CMOS sensor and a CCD that stores the generated photocurrent for a predetermined period of time and then reads it out, by changing the storage time, it is possible to prevent the detection of a high-K toner color mark. The signal level at the time of reflected light is reduced, enabling high-precision detection. Here, the "black point correction method" using a memory sensor is explained.
[0061]First, an example of a storage type sensor will be explained using FIG. 5. 121 is an example of a 1-pixel equivalent circuit diagram of the bipolar storage sensor BASIS (Base Stored Image Sensor) proposed by the applicant. 124 is a bipolar transistor with a high current amplification rate for detecting light, and 125 is a capacitance between the base and the collector, which acts as a storage charge. 126 is the PMOSFET that resets the base voltage to Vbb based on the base reset signal φbr, 127 is the NMOSFET that resets the emi...
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