Transmittance and reflectance measuring spectrophotometer having dual use light channels

摘要

An apparatus and method are provided for selectively measuring color values of a transmittance sample in a transmittance mode and a reflectance sample in a reflectance mode. The spectrophotometer includes two light channels, a first light channel from a light source to a first detector and a second light channel from the same light source to a second detector. The light channels conduct the light through the spectrophotometer. The spectrophotometer includes appropriate circuitry to compare the light striking the first and second detectors to determine the color value of a sample. A transmittance cell is located in the first light channel for selectively receiving a transmittance sample. When a sample is present, light passing through the transmittance sample is altered because the sample selectively absorbs some of the wavelengths of light. The spectrophotometer also includes a reflectance measurement area in the second light channel for selectively receiving a reflectance sample. When a sample is present, the light reflects off of the sample, the sample selectively absorbs certain wavelengths of light and reflects other wavelengths of light. When the spectrophotometer is in said transmittance mode, the transmittance sample is in the transmittance cell and a non-light altering element (such as a white tile) is in said reflectance measurement area. When the spectrophotometer is in the reflectance mode the transmittance cell is empty and the reflectance sample is received in the reflectance measurement area.