| 摘要 |
1,172,944. Measuring weight per unit of area and constituent absorption. BRUN SENSOR SYSTEMS Inc. May 22, 1968, No. 24347/68. Heading G1A. An apparatus comprises optical means 16, Fig. 1 for deriving at least three separate beams of substantially monocromatic radiation from an infrared source 13 and directing them through an organic sheet material, such as paper 10, on to detector means the beams of wavelength # 1 , # 2 , # 3 , being subject respectively to molecular bond absorption by the absorbed constituent but independent of molecular bond absorption by molecules of the sheet material; independent of molecular bond absorption by both; and subject to molecular bond absorption by the sheet material but independent of molecular bond absorption of the absorbed constituent and producing separable electrical signals the ratios Vm proportional to signal # 1 / signal # 2 ; and Vw proportional to signal # 3 / signal # 2 , of which are derived and used to indicate absorbed constituent content and basic weight of the material. The light beam may be chopped by a chopper 30 before splitting and the beams directed to separate detectors, the separate beams may be chopped at different frequencies and directed on to a common detector, or the beams may be separated in time rather than space by for example a rotating set of filters and again applied to a common detector. Suitable wavelengths in the infrared band are exemplified, and two separate wavebands meeting the requirements of # 2 may be used so that the resulting four signals may be detected in pairs. Signals proportional to ratios Vm and Vw are used in the embodiment of Fig. 1 to give a proportional moisture reading. The amplifiers in the arrangements described are tuned to the chopping frequency of the signal they are required to handle. |
