| 摘要 |
PROBLEM TO BE SOLVED: To provide an image processing unit provided with an analog/digital converter that has a conversion characteristic to suppress production of pseudo contour and uneven gradation even when processing is applied to the data of a reflectance and a gray scale and is configured not to incur a large scale circuitry and a complicated circuitry. SOLUTION: Input ranges of the analog/digital converter are divided at a crossover point of the characteristic (at a point where an output step width of a low reflectance part is equal to an output step width of a high reflectance part are equal to each other) in a way that the low reflectance part shows a gray scale linear characteristic (gamma characteristic) and the high reflectance part indicates a reflectance linear characteristic and they are made composite. The gradation is made proper in the entire conversion range and no uneven gradation is caused in data after the conversion in the image processing process to keep the image quality excellent. In order to configure the analog/digital converter with the composite conversion characteristic, adjusting the configuration of a resistor ladder supplying a reference voltage to obtain the conversion characteristic of the analog/digital converter can realize the configuration without the need for addition of a particular voltage supply circuit. |
