Chopper stabilized photoelectric transducer

Claim 2

A chopper stabilized apparatus adapted for use with a photoelectric transducer of the type comprising a light source having a brightness parameter, a shutter and a single photosensor having a sensitivity parameter illuminated by light from said source, said apparatus comprising: optical means for dividing light from said source into two beams and for directing only one of said beams along a first path through said shutter to said photosensor and only the other of said beams along a second path through chopper means to said photosensor; the position of said shutter being a function of a variable to be measured for varying the amount of light in said one of said beams impinging upon said photosensor as a function of said variable to produce a DC component related to said variable in the output of said photosensor; said chopper means periodically interrupting only the other beam of light from said source to produce an AC component in the output of said photosensor, the magnitude of said AC component being a function of said light source brightness parameter and said photosensor sensitivity parameter; circuit means for separating said AC component from the output of said photosensor; and control means coupled to receive said separated AC component for adjusting one of said parameters in response to said AC component for maintaining said AC component at a constant magnitude.

Claim 3

An apparatus as defined in claim 1 wherein said control means comprises means for controlling the brightness parameter of said light source.

Claim 4

An apparatus as defined in claim 1 wherein said optical means comprises first lens means for said first path and second lens means for said second path, said first and second lens means being contiguous and said first and second paths being substAntially parallel.

Claim 5

An apparatus as defined in claim 3 wherein said first lens means has a flat face parallel to said paths and said second lens means has a flat face parallel to said paths and to said flat face of said first lens means, said second lens means being mounted with said flat face of said second lens means abutting against said flat face of said first lens means.

Claim 6

An apparatus as recited in claim 4, wherein one of said flat faces is covered with a layer of light absorbing material.

Claim 7

An apparatus as recited in claim 4, wherein said first lens means is provided with a hole perpendicular to said first path and said flat face of said first lens means and wherein said shutter is positioned within said hole.

Claim 8

An apparatus as recited in claim 6, wherein said hole extends to said flat face of said first lens means, said second lens means is provided with a hole from said flat face of said second lens means aligned with said hole in said first lens means, and said shutter has a portion impervious to light in said hole in said second lens means.

Claim 9

An apparatus as recited in claim 7, wherein said shutter comprises a fixed tube, having a first portion with diametrically opposed slits in said hole within said first lens means and a second solid, unslit portion within said hole within said second lens means, and a movable tube having a portion with corresponding diametrically opposed slits within said first portion of said stationary tube.

Claim 10

An apparatus as defined in claim 3, wherein said second lens means has a focal plane and wherein said chopper means comprises a vibrating vane situated in said focal plane of said second lens means.

Claim 11

An apparatus as defined in claim 3, wherein said first lens means focuses the light in said first path on said shutter.

Claim 12

An apparatus as recited in claim 10, wherein said second lens means focuses the light in said second path on said chopper means.

Claim 13

A chopper-stabilized transducer including means positionally displaceable in response to external conditions, comprising: a single photosensor having a sensitivity parameter; a source of light having a brightness parameter; optical means providing first and second substantially straight, parallel paths between said source and said photosensor; movable shutter means disposed in said first path and coupled to said displaceable means for setting thereby for varying the amount of light incident on said photosensor in response to such external conditions for translation into a DC output component; chopper means disposed in said second path for causing a periodic variation in the amplitude of light incident on said photosensor for translation into an AC output component, the magnitude of said AC component being a function of said light source brightness parameter and said photosensor sensitivity parameter; circuit means for separating said AC component from the output of said photosensor; circuit means for separating said DC component from the output of said photosensor to provide an output voltage for indicating the setting of said movable shutter means; and means coupled to receive said separated AC component for adjusting one of said parameters in response to said AC component for maintaining said AC output component at a constant magnitude whereby, for any given setting of said shutter means, the magnitude of said DC output component is constant.

Claim 14

A chopper-stabilized transducer including means positionally displaceable in response to external conditions, comprising: a single photosensor having a sensitivity parameter; a source of light having a brightness parameter; optical means providing first and second substantially straight, parallel paths between said source and said photosensor; movable shutter means disposed in said first path and coupled to said displaceable means for setting thereby for varying the amount of light incident on said photosensor in response to such external conditions for translation into a DC output component; chopper means disposed in said second path for causing a periodic variation in the amplitude of light incident on said photosensor for translation into an AC output component, the magnitude of said AC component being a function of said light source brightness parameter and said photosensor sensitivity parameter; circuit means for separating said AC component from the output of said photosensor; circuit means for separating said DC component from the output of said photosensor to provide an output voltage for indicating the setting of said movable shutter means; and means coupled to receive said separated AC component for adjusting one of said parameters in response to said AC component for maintaining said AC output component at a constant magnitude whereby, for any given setting of said shutter means, the magnitude of said DC output component is constant.

Claim 15

A transducer as defined in claim 12, wherein said means positionally displaceable comprises a diaphragm displaceable in response to variations in an external pressure.

Claim 16

A pressure sensor comprising, in combination: a diaphragm displaceable in response to variations in an external pressure; a source of light having a brightness parameter; lens means for directing said light along two paths; shutter means cooperating with said diaphragm for setting thereby for attenuating said light in one of said paths; chopper means for periodically interrupting said light in the other of said paths; a pHotosensor having a sensitivity parameter for receiving light at the end of both said paths for providing a DC output component proportional to the position of said diaphragm and an AC output component having a magnitude indicative of the brightness parameter of said source and the sensitivity parameter of said photosensor; circuit means for separating said DC component and said AC component from the output of said photosensor; control means coupled to receive said separated AC component for adjusting one of said parameters in response to said AC component for maintaining said AC output component at a constant magnitude whereby, for any given setting of said shutter means, the magnitude of said DC output component is constant.

Claim 17

A pressure sensor comprising, in combination: a diaphragm displaceable in response to variations in an external pressure; a source of light having a brightness parameter; lens means for directing said light along two paths; shutter means cooperating with said diaphragm for setting thereby for attenuating said light in one of said paths; chopper means for periodically interrupting said light in the other of said paths; a pHotosensor having a sensitivity parameter for receiving light at the end of both said paths for providing a DC output component proportional to the position of said diaphragm and an AC output component having a magnitude indicative of the brightness parameter of said source and the sensitivity parameter of said photosensor; circuit means for separating said DC component and said AC component from the output of said photosensor; control means coupled to receive said separated AC component for adjusting one of said parameters in response to said AC component for maintaining said AC output component at a constant magnitude whereby, for any given setting of said shutter means, the magnitude of said DC output component is constant.

Claim 18

A pressure sensor defined in claim 14 wherein said paths are parallel and said lens means focuses the light in said one path on said shutter means and the light in said other path on said chopper means.