| 摘要 |
PURPOSE:To perform measurement in a wide dynamic range with a high sensitivity with respect to diagnosis at short and long distances in a body by including a look-up table used to convert the output of an image sensor to a density value in accordance with the quantity of light of a filter means. CONSTITUTION:If there is a measured value Y larger than an upper limit value PH, a filter 2 is switched to an area R2, where the quantity of light attenuation ranks next to that of the filter 2, to irradiate an optical fiber 3, and a look-up table 20 is switched to a table corresponding to the filter R2 through a table switching circuit 24 because the position of the use area of the filter 2 is detected by a detector 23. The characteristic of the look-up table 20 is set to a characteristic R2, and it is discriminated whether said larger value is within the range from a lower limit value RL and the upper limit value RH or not by a window comparator 31; and if it is within this range, data is written in a frame memory 30 through a write control circuit 32. If the larger value is larger than the upper limit value PH yet in this second measurement, the filter is switched furthermore; and finally, all measured values are within the range from the lower limit value PL to the upper limit value PH, and data is written in the frame memory 30.
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