QPD

Based on the evaluation indices QPD and IAQ perceived value C about indoor air quality, a new index called GPV ( generalized IAQ perceived value) is put forward, while relevant mathematic model is introduced in detail.

在室内空气品质评价指标QPD和IAQ感知值的基础上，提出广义IAQ感知值GPV的概念，并给出了数学模型。

After analyzing the principle and difficulties of analog QPD receiver, the article introduces the principle of digital QFD, oversampling and IF sampling, and the implement of digital receiver on MSL 400 spectrometer.

本文在分析模拟正交检波原理与不足的基础上，介绍了数字正交检波、过采样和采用中频直接采样的原理，及在400MHz核磁谱仪上的实现方案。

The essence of the traditional photoelectric autocollimator based on QPD is by detecting the location of the light intensity center of gravity to achieve the angle measurement.

传统的四象限光电自准直测量系统，其实质是通过检测聚焦点光斑光强重心的位置而实现角度测量的。