Recording apparatus utilizing plane of polarization modulator

Claim 2

In apparatus for recording a signal including periodic blanking pulses at a predetermined recurrence frequency, the combination comprising, means for producing a beam of coherent electromagnetic radiation, reference signal means for producing a reference signal having a frequency bearing a predetermined relationship to the rate of occurrence of the blanking pulses in said signal to be recorded, modulation means operative in response to said signal to be recorded and to said reference signal to modulate said beam of coherent electromagnetic radiation to produce a modulated output including a recurring reference component related to said reference signal, monitor means for monitoring said reference component and producing a monitor output corresponding thereto, phase detector means operative to compare the phase between said monitor output and said reference signal and to produce a control signal, and control means operative in response to said control signal to control said modulation means to cause said refErence component to conform to a predetermined standard.

Claim 3

Apparatus as set forth in claim 1 in which said means for producing a beam of coherent electromagnetic radiation comprises a laser.

Claim 4

Apparatus as set forth in claim 1 in which said modulation means comprises polarizing means for polarizing said radiation in a first plane, analyzing means for transmitting radiation polarized in a second plane, and means operative in response to application of said signal to be recorded to adjust the orientation of the plane of polarization of radiation passing from said polarizing means to said analyzing means in accordance with said signal.

Claim 5

In recording apparatus, a laser for producing a beam of coherent light, polarizing means for polarizing said light in a first plane, analyzing means for transmitting radiation polarized in a second plane, a light modulator for adjusting the orientation of the plane of polarization of light en route from said polarizing means to said analyzing means, means for impressing a signal to be recorded including a blanking portion and having a horizontal line drive on said light modulator to control the action thereof, clamp means for applying a black signal to said light modulator during blanking, means for producing a square wave signal of small amplitude and having a frequency equal to half the horizontal line drive frequency of the signal to be recorded, means for gating the square wave signal at the horizontal line drive frequency to produce a gated signal and for modifying said signal to be recorded as a function of said gated signal, a photomultiplier for monitoring the light transmitted by said analyzer and producing an output proportionate thereto, means for gating said output synchronously with the gating of said square wave signal, a phase detector for making a phase comparison between the gated output of said photomultiplier and said square wave signal, and means responsive to the output of said phase detector for adjusting at least one of said light modulator and polarizing, analyzing, and clamp means to maintain maximum extinction ratio.

Claim 6

In recording apparatus, a laser for producing a beam of coherent light, polarizing means for polarizing said light in a first plane, analyzing means for transmitting radiation polarized in a second plane, a light modulator for adjusting the orientation of the plane of polarization of light en route from said polarizing means to said analyzing means, means for impressing a signal to be recorded including a blanking portion and having a horizontal line drive on said light modulator to control the action thereof, clamp means for applying a black signal to said light modulator during blanking, means for producing a square wave signal of small amplitude and having a frequency equal to half the horizontal line drive frequency of the signal to be recorded, means for gating the square wave signal at the horizontal line drive frequency to produce a gated signal and for modifying said signal to be recorded as a function of said gated signal, a photomultiplier for monitoring the light transmitted by said analyzer and producing an output proportionate thereto, means for gating said output synchronously with the gating of said square wave signal, a phase detector for making a phase comparison between the gated output of said photomultiplier and said square wave signal, and means responsive to the output of said phase detector for adjusting at least one of said light modulator and polarizing, analyzing, and clamp means to maintain maximum extinction ratio.

Claim 7

In recording apparatus, a laser for producing a beam of coherent light, polarizing means for polarizing said light in a first plane, analyzing means for transmitting radiation polarized in a second plane, a light modulator for adjusting the orientation of the plane of polarization of light en route from said polarizing means to said analyzing means, means for impressing a signal including a blanking signal on said light modulator to control the action thereof, means for alternately increasing and decreasing the blanking signal level, means for monitoring light intensity transmitted by said analyzing means during blanking, and means responsive to said light intensity for adjusting at least one of said light modulator and polarizing and analyzing means so that the plane of polarization of light incident upon said analyzing means during a given blanking interval is offset by a given angle from a plane normal to said second plane and the plane of polarization of light incident upon said analyzing means during the next succeeding blanking interval is offset an equal but opposite angle from said normal plane.

Claim 8

In recording apparatus, a laser for producing a beam of coherent light, polarizing means for polarizing said light in a first plane, analyzing means for transmitting radiation polarized in a second plane, a light modulator for adjusting the orientation of the plane of polarization of light en route from said polarizing means to said analyzing means, means for impressing a signal including a blanking signal on said light modulator to control the action thereof, means for alternately increasing and decreasing the blanking signal level, means for monitoring light intensity transmitted by said analyzing means during blanking, and means responsive to said light intensity for adjusting at least one of said light modulator and polarizing and analyzing means so that the plane of polarization of light incident upon said analyzing means during a given blanking interval is offset by a given angle from a plane normal to said second plane and the plane of polarization of light incident upon said analyzing means during the next succeeding blanking interval is offset an equal but opposite angle from said normal plane.

Claim 9

In recording apparatus, a laser for producing a beam of coherent light, polarizing means for polarizing said light in a first plane, analyzing means for transmitting radiation polarized in a second plane, a light modulator for adjusting the orientation of the plane of polarization of light en route from said polarizing means to said analyzing means, means for impressing a signal to be recorded including white reference pulses on said light modulator to control the action thereof, successive ones of said white reference pulses being alternately of higher and lower amplitude, means for monitoring the intensity of light transmitted by said analyzing means during said white reference pulse intervals and producing a monitor output signal proportionate thereto, means for generating a referEnce signal having a frequency equal to half the frequency of recurrence of said white reference pulses, means for making a phase comparison between said monitor output signal and said reference signal, and means response to the output of said phase detector for adjusting the gain of said signal to be recorded so that successive white reference pulses cause said light modulator to offset the plane of polarization of light incident upon said analyzing means through equal and opposite angles with respect to the polarizing plane of said analyzing means.

Claim 10

In recording apparatus, a laser for producing a beam of coherent light, polarizing means for polarizing said light in a first plane, analyzing means for transmitting radiation polarized in a second plane, a light modulator for adjusting the orientation of the plane of polarization of light en route from said polarizing means to said analyzing means, means for impressing a signal to be recorded including white reference pulses on said light modulator to control the action thereof, successive ones of said white reference pulses being alternately of higher and lower amplitude, means for monitoring the intensity of light transmitted by said analyzing means during said white reference pulse intervals and producing a monitor output signal proportionate thereto, means for generating a referEnce signal having a frequency equal to half the frequency of recurrence of said white reference pulses, means for making a phase comparison between said monitor output signal and said reference signal, and means response to the output of said phase detector for adjusting the gain of said signal to be recorded so that successive white reference pulses cause said light modulator to offset the plane of polarization of light incident upon said analyzing means through equal and opposite angles with respect to the polarizing plane of said analyzing means.

Claim 11

In apparatus for recording a video signal including periodic blanking pulses and having a predetermined horizontal line drive frequency, the combination comprising: means for producing a beam of coherent electromagnetic radiation; polarizing means for polarizing said radiation in a first plane; analyzing means for transmitting radiation polarized in a second plane; a modulator interposed between said polarizing means and said analyzing means and operative to vary the orientation of the plane of polarization of radiation passing from said polarizing means to said analyzing means in response to application of an electrical signal; means for applying said video signal to said modulator; means for alternately increasing and decreasing the level of the blanking pulses of said video signal; means for measuring the intensity of the radiation transmitted by said analyzing means during blanking; and means operative in response to said measured intensity for adjusting at least one of said modulator and polarizing and analyzing means to cause the plane of polarization of radiation incident on said analyzing means during a given blanking interval to be offset by a given angle from a plane normal to said second plane and the plane of polarization of radiation incident on said analyzing means during the next succeeding blanking interval to be offset by an equal but opposite angle from said normal plane.

Claim 12

In apparatus for recording a video signal including periodic blanking pulses and having a predetermined horizontal line drive frequency, the combination comprising: means for producing a beam of coherent electromagnetic radiation; polarizing means for polarizing said radiation in a first plane; analyzing means for transmitting radiation polarized in a second plane; a modulator interposed between said polarizing means and said analyzing means and operative to vary the orientation of the plane of polarization of radiation passing from said polarizing means to said analyzing means in response to application of an electrical signal; means for applying said video signal to said modulator; means for alternately increasing and decreasing the level of the blanking pulses of said video signal; means for measuring the intensity of the radiation transmitted by said analyzing means during blanking; and means operative in response to said measured intensity for adjusting at least one of said modulator and polarizing and analyzing means to cause the plane of polarization of radiation incident on said analyzing means during a given blanking interval to be offset by a given angle from a plane normal to said second plane and the plane of polarization of radiation incident on said analyzing means during the next succeeding blanking interval to be offset by an equal but opposite angle from said normal plane.

Claim 13

Apparatus as set forth in claim 7 wherein said radiation producing means comprises a laser.

Claim 14

Apparatus as set forth in claim 8 wherein said modulator is a light modulator and further includes means for clamping the video signal applied to said modulator at a predetermined bias level to maintain maximum extinction ratio.

Claim 15

Apparatus as set forth in claim 9 wherein said means for alternately increasing and decreasing the level of the blanking pulses of said video signal comprises means for generating a square wave reference signal having a frequency equal to one-half said line drive frequency, and means for combining said square wave reference signal with said video signal prior to application to said modulator.