| 摘要 |
PROBLEM TO BE SOLVED: To calculate a half-tone dot area rate by applying light onto a printed board from a light source containing up to an infrared light region, by measuring the reflection factor of a plurality of wavelength bands at an arbitrary location, by comparing a reflection factor value and performing its operation and then calculating the difference, and by utilizing a conversion table. SOLUTION: Light from a light source 1 containing regions from a visible light region with a specific angle to an infrared light region is applied onto a half-tone dot on a printed board 5 and is condensed by a condensing lens 2. The light is applied onto the printed board 5 for absorbing and reflecting light with the shape of the surface of the printed board 5. A polarization device 3 is provided for the reflected light to shield scattered light before receiving light by a photosensitive part 4 and before performing optoelectric conversion and the voltage signal is sent to a data-processing part 10. Each reflection constituent at a place being formed only by image line and non-image line parts on the printed board 5 is registered to the data-processing part 10. Then, for a place where half-tone dot area rate is to be obtained, a reflection factor at each wavelength band begin affected to the maximum by the image line and non-image line parts is obtained and the difference is calculated. Then, the half-tone dot area rate is calculated based on the conversion table between a reflection factor value difference and the half-tone dot area rate being prepared in advance. |
