Introduction

Light source Incident Color Meter with accuracy similar to a Spectroradiometer

The CS-200 is an instrument that enables highly accurate luminance and chromaticity measurements, comparable to those of a spectroscopic type of instrument while maintaining the simplicity, operability, and competitive price of a tristimulus type.
The CS-200 features 40 sensors and performs calculations using the spectral sensitivity characteristics (colour-matching functions) corresponding to the sensitivity of the human eye. With this newly developed spectral fitting method, tristimulus values (XYZ for red, green, and blue) with a far higher accuracy than those of conventional tristimulus colorimeters can be obtained, providing excellent results.
Measurements over a wide range of luminance levels from a low luminance of 0.01 cd/m² through high luminance of 20,000,000 cd/m² (with measuring angle of 0.1°) can be carried out.
Three measuring angles can be selected: 1°, 0.2°, and 0.1°. The measuring angle can be switched according to the measurement target, ranging from display devices or other objects with large areas to measure, to objects with tiny areas to measure, such as car audio control panels, vehicle instrument panels, and compact LCDs.

Areas of application

Light sources of all types can be measured with the CS-200, for example signal, traffic lights, airport lighting, lamps, LEDs, picture tubes, LCDs, PDPs, etc., simply anything that emits light. With the ever-growing demand for diversified media, stimulated by the growth of information-technology business and full-scale service of digital broadcasting, research and development has accelerated for various display devices centring on plasma displays and LCDs. Innovations in LED technology have led to remarkable breakthroughs in the development of LED products including traffic lights, backlights for reflective LCDs, and large outdoor display screens.

Background knowledge

There are two ways of determining luminance and chromaticity values for a light source.

A tristimulus type of instrument measures light sources with three sensors (red, green, blue light) which have similar sensitivity to light as the human eye. The filters used to reach this sensitivity have a limit in precision and thus the readings of tristimulus instruments can not be perfect for all kinds of light sources. Best accuracy is reached when measuring light sources with a similar spectral distribution like that of the light source used for calibration of the instrument.

The second method, which is used by the CS-200, is to measure the spectral emittance of the light source and perform calculations using the spectral sensitivity characteristics (colour-matching functions) corresponding to the sensitivity of human eye. Using this method, the mis-matching of filters is avoided and thus the measurement results are much more precise.