| 摘要 |
A readhead with reduced height sensitivity for use in a reflectance photometer that measures reflectance of diffuse light from a sample disposed outside the readhead includes a housing with an upper spherical portion and a lower conical portion. The inner peripheral surface of the upper portion is hemispherically configured and the inner peripheral surface of the lower portion is conically configured to permit illumination of a sample disposed outside the readhead. The angle of the cone defined in the conical portion of the housing is in the range of 45 DEG -60 DEG . The inner peripheral surfaces of the upper and lower portions are coated with a highly reflective material, such as barium sulfate. The apex of the conically configured housing portion is truncated to provide a light transmitting aperture for sample illumination. A sample is positioned adjacent the light-transmitting aperture below and outside the conically shaped readhead housing portion. The housing includes a second aperture for receiving a high intensity light from a flash lamp or incandescent light to illuminate the interior of the housing and diffusely illuminate the sample. A baffle is located adjacent the second aperture to avoid direct illumination of the sample. Fiberoptic bundles and photodetectors as well as lenses and reflecting surfaces are provided to detect the amount of diffuse light reflected from the sample.
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