Distance measuring apparatus

Claim 1

A distance measuring apparatus for measuring a distance from a reference point to a subject of interest comprising: means for radiating an energy beam toward said subject of interest; receiving means for receiving the portion of said energy beam reflected from said subject, said receiving means including a receiving surface defined between two extreme points and means for supplying first and second current signals with the magnitude of each of said first and second current signals being respectively determined by the location of impingement of said reflected energy beam within and in respect to said two extreme points; first extracting means for extracting and outputting a first fluctuating component from said first current signal in the form of a voltage said first extracting means including a first logarithmic conversion circuit for receiving said first current signal, first storing means for storing a background light component prior to radiation by said energy beam and first sampling means for sampling said first fluctuating component as a difference between sid background light component stored in said first storing means and said first current signal; second extracting means for extracting and outputting a second fluctuating component from said second current signal in the form of a voltage said second extracting means including a second logarithmic conversion circuit for receiving said second current signal, second storing means for storing said background light component prior to radiation by said energy beam and second sampling means for sampling said second fluctuating component as a difference between said background light component stored in said second storing means and said second current signal; and a differential processing means for producing a distance signal indicating a distance to said subject by taking a difference between said first and second fluctuating components which are output from said first and second extracting means.