Low noise photoelectric detector apparatus

• US 3,996,476 A
• Filed: 09/10/1975
• Issued: 12/07/1976
• Est. Priority Date: 09/10/1975
• Status: Expired due to Term

• Current Assignee: Scientific Technologies Incorporated (Omron Corporation)
• Original Assignee: Scientific Technologies Incorporated (Omron Corporation)
• Inventors: Lazzara, Anthony Ross
• Primary Examiner(s): Smith, Alfred E.
• Assistant Examiner(s): Moore, David K.
• Application Number:
  US05/611,871
• Time in Patent Office: 454 Days
• Field of Search: 250/563, 250/574, 250/566, 250/227, 250/208, 250/211 J, 250/552, 250/553, 250/568
• US Class Current: 250/559.4
• CPC Class Codes: G01N 21/474 Details of optical heads therefor, e.g. using optical fibres
• CPC Class Codes: G01N 21/55 Specular reflectivity
• CPC Class Codes: G01S 17/04 Systems determining the presence of a target

Abstract

A photoelectric sensor includes a photodetector, a lens, and a light source all mounted within a framework for holding the lens with the photodetector and light source located on the central axis of the lens. The photodetector is positioned on the rear side of the lens within the framework at approximately the lens focal point. The light source is positioned to emit light away from the front side of the lens. Structure in the form of an opaque collar is provided for mounting the light source relative to the lens to prevent impingement of spurious light from the light source upon the lens. An object positioned in front of the lens intercepts the emitted light from the light source and reflects it back toward the lens, whereupon it is directed to the photodetector. A signal indicative of the presence of the object is provided by the photodetector responsive to the reflected light.

Claims

1. A low noise photoelectric sensing apparatus comprising a framework, a lens mounted in one end of said framework for focusing light impinging thereupon at a focal point located on the rear side of said lens on a central axis passing therethrough, said lens having a front side exposed to the exterior of said framework and having a central hole therein,

a photodetector mounted in said framework on said central axis positioned toward the rear of said lens for receiving the focused light and providing an output signal related thereto,

a light source mounted on said central axis positioned toward the front of said lens for emitting light away from said lens,

an opaque collar formed to fit in said central hole for shielding said lens from said emitted light to reduce noise in said output signal resulting from spurious light from said light source impinging on said photodetector, said lens serving to receive emitted light only after reflection from objects in front of said lens, whereby said output signal provides a low noise indication thereof.

2. A low noise photoelectric sensing apparatus as in claim 1 wherein said lens comprises a bundle of fiber-optics.

3. A low noise photoelectric sensing apparatus as in claim 1 wherein said framework comprises a substrate, together with a plurality of additional photodetectors positioned on said substrate, said lens being mounted overlying said photodetector and additional photodetectors, said additional photodetectors producing a plurality of additional output signals, a plurality of additional light sources, one for each additional photodetector, said light source and additional light sources positioned on the front side of said lens, whereby emitted light from said light source and additional light sources is prevented from entering said lens.

4. A low noise photoelectric sensing apparatus as in claim 3 together with means mounted on said substrate for energizing said light source and additional light sources, means for receiving said output signal and additional output signals mounted on said substrate, said last named means providing an indication of reflecting surfaces passing in front of said lens.

5. A low noise photoelectric sensing apparatus comprising a supporting framework,

a lens mounted in said framework having a front side, a rear side, a central axis, and a focal point on the rear side of said lens,

a photodetector mounted in said framework substantially at said focal point, for producing an output signal responsive to light impinging thereupon,

a light source positioned on the front side of said lens, disposed to emit light away from said lens,

an outer protective lens mounted in said framework on the front side of said lens, said outer protective lens having a hole therethrough on said central axis, and an opaque collar formed to fit in said hole and to receive said light source,

whereby spurious light emitted by said light source is prevented from reaching said photodetector through said lens, and emitted light is reflected toward said lens by objects passing in front of said lens for focusing on said photodetector.

6. A low noise photoelectric sensing apparatus comprising a substrate,

a plurality of photodetectors mounted in alignment on said substrate and producing a plurality of output signals when exposed to light of predetermined intensity,

a lens overlying said substrate and photodetectors for focusing light impinging thereupon onto said photodetectors, said lens having

a plurality of through holes, one for each photodetector and in alignment therewith,

a plurality of light sources for emittng light and having electrical connections extending through said plurality of holes and positioned one each in front of said lens overlying each of said holes, and means on said substrate for providing electrical access to said light source electrical connections and said photodetectors, whereby objects passing in front of said lens reflect said emitted light toward said lens for focusing on said photodetectors for indicating object presence.

7. A low noise photoelectric sensing apparatus as in claim 6 together with

means for energizing said plurality of light sources mounted on said substrate,

means for receiving said plurality of output signals, said last named means being mounted on said substrate and providing a predetermined signal form for indication of size of the objects reflecting emitted light.