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Apparatus-for-converting-light-signals-into-digital-electrical-signals

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Apparatus for converting light signals into digital electrical signals

Details

Inventors: Maeda, Yoshio;
Assignee: Hitachi, Ltd. (JP)
Primary Examiner: Hille; Rolf G.
Assistant Examiner:
Attorney, Agent or Firm: Craig & Antonelli

A light signal entering a photo-electric converter means is interrupted at a certain interval of time. An electrical signal produced from the photo-electric converter means, after a predetermined amount of electrical signal is added to it, is A-D converted. The difference between the digital signal associated with the interruption of light to the photo-electric converter means and the digital signal associated with non-interruption of light to the photo-electric converter means is produced, which difference is proportional to the incident light signal. Even when the light entering the photo-electric converter means is very weak, the fact that a predetermined amount of electrical signal is added contributes to A-D conversion of good linearity. Even very weak light is thus A-D converted accurately. Noises and undesirable DC signal components contained in the two types of digital signals are offset by production of the difference.

DETAILED DESCRIPTION Accordingly, it is an object of the present invention to provide an apparatus for converting light with wide dynamic range, especially, very weak light accurately into a digital electrical signal by eliminating the effect of the noise superimposed on the electrical signal produced from the photoelectric converter means.
The light signal entering the photo-electric converter means is converted into an electrical signal and then into a digital signal by an A-D converter means.
A predetermined amount of signal is added to the electrical signal applied to the A-D converter means.
The difference between the digital signals associated with interruption and non-interruption of light entering the photo-electric converter is calculated.
In view of the fact that a predetermined signal is added, even very weak light to be measured, which enters the photo-electric converter means, is converted with accuracy into a digital signal in the satisfactory linearity range of the A-D converter means.

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