Photodetector for optical encoder

Abstract

A photodetector for an optical encoder has plural sets of segmented photodiodes, each set of which is made by two adjoining segmented photodiodes capable of coping with a scale slit having a reference resolution. Output lines of the two adjoining segmented photodiodes are connected together in each set of the photodiodes. These output lines are connected to output lines of the corresponding segmented photodiodes in the other sets. The two adjoining segmented photodiodes function like one segmented photodiode, and thereby, the resolution of the applied scale slit is made ½ of the reference resolution. Thus, this photodetector easily copes with a scale slit having a half resolution of the reference resolution at low cost only by modification of wiring without changing any configuration of the segmented photodiodes.

1 . A photodetector for an optical encoder constructed by a plurality of segmented photodiodes which are formed by being electrically divided on a semiconductor chip, comprising: 
 output terminals of two or more mutually adjacent segmented photodiodes electrically connected together.    
     
     
         2 . A photodetector for an optical encoder constructed by a plurality of segmented photodiodes which are formed by being electrically divided on a semiconductor chip, comprising: 
 two or more arrays of the plurality of segmented photodiodes arranged in parallel such that segmented photodiodes in one array are shifted in relation to segmented photodiodes in another array by one half an arrangement pitch of the segmented photodiodes to mutually shift phases of segmented photodiodes between the arrays.    
     
     
         3 . The photodetector for an optical encoder as claimed in  claim 2 , further comprising: 
 output terminals of two or more adjacent segmented photodiodes in each of the arrays electrically connected together.    
     
     
         4 . The photodetector for an optical encoder as claimed in  claim 1 , wherein, 
 output terminals of two segmented photodiodes located at both ends in three or more adjacent segmented photodiodes are electrically disconnected.    
     
     
         5 . The photodetector for an optical encoder as claimed in  claim 3 , wherein, 
 output terminals of two segmented photodiodes located at both ends in three or more adjacent segmented photodiodes are electrically disconnected.    
     
     
         6 . The photodetector for an optical encoder as claimed in  claim 1 , wherein 
 the electrical connection of the output terminals of the segmented photodiodes is achieved by adjusting metal wiring with use of laser trimming.    
     
     
         7 . The photodetector for an optical encoder as claimed in  claim 1 , wherein 
 the electrical connection of the output terminals of the segmented photodiodes is achieved by switching means having a control terminal, and    the segmented photodiode of the output terminals, which are electrically connected, is changed in number by an external control signal to the control terminal of the switching means.