公开(公告)号：US5173750A

公开(公告)日：1992-12-22

申请号：US475575

申请日：1990-02-06

Applicant: Joseph F. Laukaitis

Inventor： Joseph F. Laukaitis

IPC: G01J1/16 ,  G01J1/18 ,  G01J1/44 ,  G01N21/27

CPC classification number: G01J1/16 ,  G01N21/27 ,  G01J2001/1694 ,  G01J2001/184 ,  G01J2001/4433 ,  G01N21/4738 ,  G01N2201/0621

Abstract: A reflection densitometer includes a light source and a photodetector having an output which has a signal component characteristic of the amount of reflected light received from a surface to be measured and a noise component. The noise component of the output is isolated in time by switching the light source on and off so as to create alternating first and second time periods during which the output of the photodetector is characteristic of only the noise component and in which the output of the photodetector is characteristic of both the signal component plus the noise component, respectively. The output of the photodetector during the second time period is subtracted from the output during the first time period to obtain a signal characteristic of only the output of the photodetector characteristic of relected light received. The signal is held constant during the first and second periods by a sample and hold circuit adapted to sample the signal during the second periods and to hold the sampled signal during the first periods.

Abstract translation: 反射光密度计包括光源和具有输出的光电检测器，该输出具有从被测量表面接收的反射光的信号分量特性和噪声分量。 通过切换光源来输出的噪声分量在时间上是隔离的，以便产生交替的第一和第二时间段，在该时间段期间，光电检测器的输出仅具有噪声分量，并且其中光电检测器的输出 分别是信号分量加噪声分量的特征。 在第一时间段期间，从第二时间段的光电检测器的输出中减去输出，以获得仅接收的所选择的光的光检测器特性的输出的信号特性。 信号在第一和第二周期期间由采样和保持电路保持恒定，该采样和保持电路适于在第二周期期间对信号进行采样并且在第一周期期间保持采样信号。