The purpose of this study was to investigate the influence of the illuminance of the illuminating lights on the chromatical values of the non-contact type spectrophotometer.
The spectrophotometer used in this study was the Hitachi Products Co. Color Analyzer C-1020. The C-1020 is the spectrophotometer which utilizes a telephoto camera lens and the reflection light of the object is received into the spectroscope. Color is measured in the natural light covered conpact room. The D65 fluorescent lamps were used for the room lights and the D65 xenon lamp was used for the spotlight. The illuminance on the color measuring surface was 481.2 lx in the case lit up with the room lights without the spotlight and the illuminance on the color measuring surface was 2867 lx in the case lit up with the room lights and the spotlight. Both in the cases of with and without the spotlight, the spectral reflectances and the chromatical values of the standard white color plate were compared between the conditions when the number of the converter of the telephoto camera lens was one and the number of that was two for measuring smaller areas. Adding to that, both in the cases of with and without the spotlight, cheek skin colors of the 24 year old female were compared between the conditions of using one converter and using two converters, and the lower lip colors and gingival colors of the same subject were measured using two converters.
The following results were obtained.
1) The influence of the illuminance of the illuminating lights on the spectral reflectance and the chromatical values was significant.
2) The chromatical values measured with the non-contact type spectrophotometer which utilizes a telephoto camera lens were influenced with the illuminance of the illuminating lights, spotlight, the number of the converter of the telephoto camera lens and the dimension of the color measuring area.
3) In the condition of using one converter for measuring relatively large areas, the precision of the chromatical values was higher in the case without spotlight than that illuminated with the spotlight.
4) When using two converters for measuring 3 mm or under 3 mm diameter small areas, the precision of the chromatical values might be higher in the case illuminated with the spotlight than that without the spotlight.