Image sensor and rangefinder device having background subtraction with paired analog shift registers

• US 4,490,036 A
• Filed: 08/18/1982
• Issued: 12/25/1984
• Est. Priority Date: 08/18/1982
• Status: Expired due to Fees

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Anagnostopoulos, Constantine N.
• Primary Examiner(s): Buczinski, S. C.
• Assistant Examiner(s): Sotomayor, John B.
• Application Number:
  US06/409,256
• Time in Patent Office: 860 Days
• Field of Search: 356/1, 356/4, 354/403
• US Class Current: 356/3.07
• CPC Class Codes: G01S 17/46 Indirect determination of position data
• CPC Class Codes: G02B 7/32 using active means, e.g. light emitter including both an active and a passive focus detecting device G02B7/285; using ultrasound G02B7/40
• CPC Class Codes: H01L 27/14825 Linear CCD imagers

Abstract

A rangefinder device includes means for projecting a beam of light to illuminate a spot on an object in a scene, an image sensor for sensing an image of the scene, and signal processing means responsive to signals produced by the image sensor for determining the relative location of the illuminated spot in the image of the scene to determine the distance to the object. The rangefinder device features means for removing the contribution due to ambient scene illumination from the photosignals, including an improved image sensor having an array of photosensors and a pair of analog shift registers for receiving the photosignals from the array of photosensors. One of the analog shift registers receives photosignals from the photosensor array when the beam is turned off, and the other analog shift register receives photosignals from the array when the beam is turned on. The shift registers are read out simultaneously and the signals therefrom are differenced to yield a series of photosignals free from background scene information. The difference signals are supplied serially to a peak detector to determine the location of the illuminated spot. In a preferred embodiment, the rangefinder is designed to operate from a single low voltage power source.

Claims

1. A range finder, comprising:

means energizable for projecting a beam of light to illuminate a spot on an object in a scene;

a linear array of photosensors responsive to light for generating a photosignal proportional to the quantity of light falling thereon;

means for forming an image of a portion of the scene containing the illuminated spot on said array;

first and second analog shift register means for receiving, in parallel, a plurality of analog signals, and responsive to control signals for delivering said analog signals serially to first and second output means respectively;

first and second means actuable for transferring the photosignals in said array to said first and second analog shift register means respectively;

control means for energizing said light beam and actuating said first transfer means, for deenergizing said light beam and actuating said second transfer means, and for supplying control signals simultaneously to said first and second analog shift register means to cause the photosignals therein to be delivered in synchronism to said first and second output means respectively;

differential means connected to said first and second output means and responsive to the photosignals thereat to form difference signals; and

signal processing means responsive to said difference signals for detecting the location of the image of said illuminated spot on said array and producing a distance signal in response thereto.

2. The invention claimed in claim 1, wherein said photosensors comprise photodiodes, said analog shift register means comprise buried channel CCD shift registers, and said transfer means comprise transfer gates for forming surface channels between said photodiodes and said buried channel CCD shift registers, whereby said automatic range finder may be operated by a single low voltage power supply.

3. The invention claimed in claim 2, further comprising sense and reset FET preamplifiers associated with each of said CCD shift registers, wherein the reset FET of said preamplifier is a buried channel FET and the sense FET is a surface channel FET, whereby said sense and reset preamplifiers are operated by the single low voltage power supply.

4. A rangefinder of the type having means for projecting a beam of light to illuminate a spot on an object in a scene, an image sensor for sensing the light from a scene and producing photosignals representative thereof, and means responsive to the photosignals for detecting the position of the illuminated spot in the scene to determine the distance to the object, said rangefinder including means for removing background noise from the photosignals produced by the image sensor by sensing the scene with the light beam on and again with the light beam off, and forming difference signals from the photosignals produced thereby, characterized in that said image sensor includes:

(1) an array of photosensors (22) responsive to incident light for producing photosignals, (2) first and second analog shift registers (24 and 24'"'"'), adjacent the array of photosensitive elements, for receiving a plurality of signals in parallel and shifting the signals serially to an output location, (28 and 28'"'"') (3) first and second transfer gates (26 and 26'"'"') located respectively between the array of photosensitive elements and the first and second analog shift registers, for selectively transferring the photosignals produced by the photosensitive elements into the respective shift registers,

whereby, the photosignals produced with the light beam on are transferred to the first shift register, and the photosignals produced with the light beam off are transferred to the second shift register, and the shift registers are read out simultaneously to deliver the photosignals to a differencing circuit.

5. The invention claimed in claim 4, further characterized by said photosensitive elements (22) being photodiodes, said analog shift registers (24 and 24'"'"') being buried channel charge coupled device shift registers, and said transfer gates (26 and 26'"'"') being actuable for forming surface channels between said photodiodes and said buried channel CCD shift registers,

whereby, the image sensor may be operated from a single low voltage power supply.