Densitometer with automatic gain and reference value adjustment of

Abstract

A computer controlled diagnostic densitometer for analyzing optical density patterns of blood samples or the like scans a sample and generates an analog waveform signal representative of the scanned optical density pattern. The analog signal is amplified, digitized, stored in a memory and is later read from memory to reconstruct a visual display of the waveform for analysis. Several types of optical density pattens may be scanned which result in analog signals of different amplitudes and signal-to-background noise ratios. An improved amplification system automatically preadjusts the gain and reference value of the analog signal prior to digitization in order to substantially eliminate background noise in the signal and produce substantially full scale analog signal values. The gain and reference value preadjustments are performed by a pair of corresponding multipliers which multiply the analog signal by memory-stored digital data which is unique to the type of optical density pattern being scanned. The gain and reference voltage may also be manually preadjusted in order to assure sample-to-sample analysis consistency for samples from the same patient.