Calibration method and endoscope system

An endoscope system having semiconductor light sources for emitting different types of illumination light with different wavelength ranges, a light source controller for controlling the semiconductor light sources with respective light source control signals, and a brightness command signal generator for generating a brightness command signal n for commanding the light source controller to change a light amount of the each illumination light based on a brightness step n (n being an integer from 0 to N−1) of N (N being an integer greater than or equal to 2) levels, a light amount ratio between the light amounts of the illumination light being set in advance as a set light amount ratio, the endoscope system comprising:

• a calibration light controller for applying a first light source control signal to the each semiconductor light source and allowing the each semiconductor light source to emit the each illumination light to a reference object;
• a light amount calculator for calculating a light amount of the each illumination light reflected from the reference object;
• a first associating section for generating calibration data by associating the first light source control signals with the light amounts of the illumination light calculated by the light amount calculator in a case where the first light source control signals are applied;
• a maximum light amount setter for setting a maximum light amount of the each illumination light in accordance with the set light amount ratio and based on the calibration data;
• an nth light amount setter for setting an nth light amount for the each illumination light based on the maximum light amount of the each illumination light, the nth light amount increasing or decreasing linearly relative to the brightness step n;
• a light source control signal setter for referring to the calibration data and determining a light source control signal corresponding to the nth light amount from the first light source control signals, and setting the determined light source control signal as a second light source control signal corresponding to the brightness step n;
• and
• a second associating section for associating the second light source control signal with the brightness command signal n corresponding to the brightness step n, to generate a light control table.

A calibration method for an endoscope system having semiconductor light sources for emitting different types of illumination light with different wavelength ranges, a light source controller for controlling the semiconductor light sources with respective light source control signals, a brightness command signal generator for generating a brightness command signal n for commanding the light source controller to change a light amount of the each illumination light based on a brightness step n (n being an integer from 0 to N−1) of N (N being an integer greater than or equal to 2) levels, and a color image sensor, a signal ratio between image signals of different colors being set in advance as a set signal ratio, the image signals being obtained by imaging an observation object under the different types of the illumination light with the color image sensor, the calibration method comprising the steps of:

• (A) applying a light source control signal to the each semiconductor light source and allowing the each semiconductor light source to emit the each illumination light to a reference object, and imaging the reference object with the color image sensor;
• (B) setting the light source control signal which makes the signal ratio between image signals of different colors obtained by imaging the reference object and outputted from the color image sensor equivalent to the set signal ratio, as a specific light source control signal;
• (C) setting the light source control signal which is applied to the semiconductor light source with high light emission, as a reference light source control signal, the highest of the specific light source control signals being applied to the semiconductor light source with the high light emission;
• (D) obtaining a control signal ratio between the specific light source control signals;
• (E) obtaining the light source control signal for the brightness step n for the each semiconductor light source based on the reference light source control signal and the control signal ratio, the light source control signal for the brightness step n corresponding to the brightness step n;
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• (F) storing the light source control signal for the brightness step n and the brightness command signal n for the brightness step n in a light control table such that the light source control signal for the brightness step n is associated with the brightness command signal n for the brightness step n.