Apparatus for providing a compensation signal for individual light sensors arranged in a predetermined relation

• US 4,128,830 A
• Filed: 09/26/1977
• Issued: 12/05/1978
• Est. Priority Date: 09/26/1977
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Weythman, Gayle A.
• Primary Examiner(s): Boudreau, Leo H.
• Application Number:
  US05/836,881
• Time in Patent Office: 435 Days
• Field of Search: 340/146.3 AG, 340/146.3 H, 358/282, 358/284, 358/80
• US Class Current: 382/273
• CPC Class Codes: G06V 10/12 Details of acquisition arrangements; Constructional details thereof

Abstract

The dark scan noise level produced from each of a solid state array of light sensors is obtained by preventing light from being received by each of the light sensors for a predetermined period of time. This signal is converted into a digital signal and stored in a shift register. When each of the light sensors of the array is subjected to light, the output signal produced thereby is reduced by the stored noise signal for the same light sensor. These output signals from the light sensors can be converted to digital signals and have the noise correction signals from the shift register subtracted therefrom by a digital subtractor, which is a complementary adder, or the digital noise correction signals from the shift register can be converted to analog signals and subtracted from the output signals of the light sensors of the array in an analog subtractor. The noise correction signals from the shift register are recirculated to the shift register during supply to the subtractor.

Claims

1. An apparatus for providing a compensation for dark scan noise level for each of a plurality of individual light sensors arranged in a predetermined relation including:

means to produce a separate output signal from each of the individual light sensors in accordance with the level of light received by each of the individual light sensors;

said producing means producing a separate compensation signal for dark scan noise level from each of the individual light sensors when the individual light sensors are prevented from being subjected to light;

storage means for receiving and storing the separate compensation signal from said producing means for each of the light sensors to compensate for the dark scan noise level affecting the accuracy of the separate output signal of the same light sensor from said producing means;

means to connect said producing means to said storage means only when the individual light sensors are prevented from being subjected to light;

subtracting means to subtract the separate compensation signal from said storage means from the output signal of the same light sensor from said producing means to produce a signal compensated for the dark scan noise level;

and means to supply all of the separate output signals from said producing means to said subtracting means.

2. The apparatus according to claim 1 including:

means to convert each of the separate compensation signals from said producing means into a digital signal prior to supply to said storage means and each of the output signals from said producing means into a digital signal prior to said subtracting means.

3. The apparatus according to claim 2 in which:

said producing means produces the separate output signals in serial fashion;

said storage means includes shift register means;

said producing means supplies the separate compensation signals to said shift register means from the individual light sensors in serial fashion when the individual light sensors are prevented from being subjected to light;

means to recirculate each of the separate compensation signals to said shift register means during supply of the same separate compensation signal to said subtracting means;

and means to prevent recirculation of any of the separate compensation signals to said shift register means during the supply of the separate compensation signals from said producing means to said shift register means.

4. The apparatus according to claim 2 in which said producing means produces the separate output signals in serial fashion.

5. The apparatus according to claim 1 including:

means to convert each of the separate compensation signals from said producing means into a digital signal prior to supply to said storage means;

and means to convert each of the separate compensating signals from said storage means into an analog signal prior to supply to said subtracting means.

6. The apparatus according to claim 5 in which:

said producing means produces the separate output signals in serial fashion;

said storage means includes shift register means;

said producing means supplies the separate compensation signals to said shift register means from the individual light sensors in serial fashion when the individual light sensors are prevented from being subjected to light;

means to recirculate each of the separate compensation signals to said shift register means during supply of the same separate compensation signal to said subtracting means;

and means to prevent recirculation of any of the separate compensation signals to said shift register means during the supply of the separate compensation signals from said producing means to said shift register means.

7. The apparatus according to claim 1 in which said producing means produces the separate output signals in serial fashion.