Sensing color with the TAOS TCS230The TAOS TCS230 is a small， highly integrated color sensing device packaged in a clear plastic 8-pin SOIC. It reports ， as analog frequency, the amount of shortwave (blue ） , mediumwave （ green) ， longwave （ red) ， and wideband (white） optical power incident onto the device。 It can be used in a variety of color sensing applications. Details of the device can be found in its datasheet. This white paper details the concepts and calculations involved in color sensing using the TCS230. We will use the ColorChecker chart as an optical stimulus to work through a numerical example of color sensing 。 The chart ， depicted in Figure 1 ， is manufactured and distributed by GretagMacbeth。 The chart measures approximately 13 inches by 9 inches （ 330 mm by 230 mm ） ; it contains 24 colored patches arranged in a 6 by 4 array. Figures 2 through 5 overleaf show the spectral reflectance of the patches in each of the four rows of the chart – that is, the fraction of incident light that is reflected （with respect to an ideal diffuse reflector)， as a function of wavelength from 350 nm to 750 nm.Figure 1 The ColorChecker contains 18 colored patches and a 6—step gray series。Figure 2 ColorChecker spectra, top row.Figure 3 ColorChecker spectra， second row。Figure 4 ColorChecker spectra， third row。Figure 5 ColorChecker spectra, bottom row (neutral series）Figure 6 Cone sensitivities of cone photoreceptors are shown. Theshortwave-sensitivephotoreceptors are much less sensitive than the other two types。 The responses of the mediumwave and longwave photoreceptors have a great deal of overlap。 Vision is not sensitive to the precise wavelength of the stimulus ：...
