Transducer-positioning system using radiation-sensitive means

Claim 2

In a positioning system of a type for registering a signal transducer with respect to each of a plurality of laterally adjacent record paths defined upon a record medium comprising means forming first and second light paths, light source means for projecting light along said paths, first and second photoresponsive means respectively disposed in each of said paths for providing electrical signal representations indicative of the level of light projected in their respective paths, first and second mask means having discrete, spaced transmissive portions respectively serving to subdivide the light projected in said paths, each of said photoresponsive means being disposed to be influenced by the aggregate light passing simultaneously via a large number of said transmissive portions of its associated mask means to provide its said signal representation, shutter means carried by said transducer for progressively increasIng the light transmitted via one of said mask means relative to the light transmitted via the other of said mask means in response to movement of said transducer to provide relatively oppositely varying signal representations from said first and second photoresponsive means, and means conjointly responsive to changing differences in said signal representations changing in a predetermined electrical direction and to a net difference of predetermined polarity between the two signal representations of said first and second photoresponsive means to move and dispose the transducer with stability at said track positions.

Claim 3

A positioning system according to claim 1 further including means providing a predetermined degree of difference between said signal representations to effect movement of said transducer.

Claim 4

A positioning system according to claim 1 further including means serving to move said transducer by discrete steps in response to a predetermined degree of difference between said signal representations, and means for counting the steps taken by the transducer.

Claim 5

In a positioning system of a type for registering a positionable element with respect to each of a plurality of adjacent positions comprising means forming first and second light paths, light source means for projecting light along said paths, first and second photoresponsive means respectively disposed in each of said paths for providing electric signal representations indicative of the level of light projected in their respective paths, first and second mask means having discrete, spaced transmissive portions respectively serving to subdivide the light projected in said paths, each of said photoresponsive means being disposed to be influenced by the aggregate light passing simultaneously via a large number of said transmissive portions of its associated mask means to provide its said signal representation, shutter means carried by said positionable element for progressively increasing the light transmitted via one of said mask means relative to the light transmitted via the other of said mask means in response to movement of said element to provide relatively oppositely varying signal representations from said first and second photoresponsive means, and means responsive to alternately occurring minimum differences between the signal representations of said first and second photoresponsive means developed during continued relative movement between said first and second mask means and to those differences of a predetermined polarity between said signal representations of said first and second photoresponsive means to move and register said positionable element with stability centrally of one of said positions.

Claim 6

In a positioning system of a type for registering a positionable element with respect to each of a plurality of adjacent positions comprising means forming first and second light paths, light source means for projecting light along said paths, first and second photoresponsive means respectively disposed in each of said paths for providing electric signal representations indicative of the level of light projected in their respective paths, first and second mask means having discrete, spaced transmissive portions respectively serving to subdivide the light projected in said paths, each of said photoresponsive means being disposed to be influenced by the aggregate light passing simultaneously via a large number of said transmissive portions of its associated mask means to provide its said signal representation, shutter means carried by said positionable element for progressively increasing the light transmitted via one of said mask means relative to the light transmitted via the other of said mask means in response to movement of said element to provide relatively oppositely varying signal representations from said first and second photoresponsive means, and means responsive to alternately occurring minimum differences between the signal representations of said first and second photoresponsive means developed during continued relative movement between said first and second mask means and to those differences of a predetermined polarity between said signal representations of said first and second photoresponsive means to move and register said positionable element with stability centrally of one of said positions.

Claim 7

A positioning system according to claim 1 wherein said light source means comprises a single light source common to both of said light paths.