Detector for distinguishing between recorded and unrecorded bands of a phonograph record
AssigneeMinnesota Mining and Manufacturing Company
InventorJohn T. Mullin
Life of this patent
Estimating the term…
Abstract
A detector for scanning the surface of a record on a phonograph turntable to distinguish between recorded and unrecorded bands by detecting physical differences on the record surface. The detector illuminates a portion of the record surface and senses light reflected from such portion with a photoelectric cell. The portion of the record surface from which reflected light is detected is accurately controlled for reliable operation by a lens that focuses such reflected light at and through an aperture. The lens is fixedly mounted a first predetermined distance from the aperture and maintained a second predetermined distance from such portion of the record surface by a wheel that rides on the record surface.
Claims14
A detector for scanning the broad surface of a record on a phonograph record turntable, wherein recorded bands are distinguished from unrecorded bands by detecting physical differences on the record surface between recorded and unrecorded portions thereof, the broad surface of said record including land areas and recording grooves recessed from said land areas, said detector comprising:
- means for illuminating a portion of the record surface;
- means for sensing light reflected from said portion of the record surface and providing an electrical output in response thereto;
- means having an aperture between said portion of the record surface and said sensing means;
- means positioned between said portion of the record surface and said aperture and at a first predetermined distance from said aperture for focusing light reflected from said portion through said aperture and upon said sensing means;
- and
- a rotatable wheel for contacting the land areas of the record surface for maintaining the focusing means at a second predetermined distance from said portion of the record surface so that light reflected from said portion is focused at said aperture and detected by said sensing means, said wheel disposed for rotation in response to movement of the detector between the outer and central portion of the record and independent of any movement of the record.
A detector for scanning the broad surface of a record on a phonograph record turntable, wherein recorded bands are distinguished from unrecorded bands by detecting physical differences on the record surface between recorded and unrecorded portions thereof, the broad surface of said record including land areas and recording grooves recessed from said land areas, said detector comprising:
- means for illuminating a portion of the record surface;
- a photoelectric cell for sensing light reflected from land areas of said portion of the record surface and providing an electrical output in response thereto;
- means having an aperture between said portion of the record surface and said photoelectric cell;
- a lens between said portion of the record surface and said aperture for focusing light reflected from said portion through said aperture and upon said photoelectric cell, said lens located a first predetermined distance from said aperture;
- a rotatable wheel riding on the land areas of the record surface for maintaining the lens at a second predetermined distance from said portion of the record surface so that light reflected from land areas of said portion is focused by said lens at said aperture and detected by said photoelectric cell, said wheel disposed for rotation in response to movement of the detector between the outer and central portion of the record and independent of any movement of the record;
- and
- amplifier means operatively connected to the electrical output of said photoelectric cell, said amplifier means including a high pass filter and an amplifier and providing an output in response to the output of said sensing means.
Dependencies are inferred from the claim text.