Apparatus for locating a variable optical focal point

Claim 1

A system having a given optical axis for locating upon the optical axis a focal point of a scanning beam of light having a cone shaped locus of scan defined from a cone apex disposed at the focal point, the direction of the scan of the beam inverting at the focal point, the system, comprising: a photodetector having a photosensitive element substantially disposed on the given optical axis and movable along the given optical axis, for generating a phase-sensitive output as a function of the direction of scan of the beam across the photosensitive elemeNt; first means responsive to the phase-sensitive output for generating a control signal as a function of the axial postion of the photosensitive element relative to the focal point; and second means responsive to the generated control signal for moving the photosensitive element toward the focal point.

Claim 2

A system having a given optical axis for locating upon the optical axis a focal point of a scanning beam of light having a cone shaped locus of scan defined from a cone apex disposed at the focal point, the direction of the scan of the beam inverting at the focal point, the system, comprising: a photodetector having a photosensitive element substantially disposed on the given optical axis and movable along the given optical axis, for generating a phase-sensitive output as a function of the direction of scan of the beam across the photosensitive elemeNt; first means responsive to the phase-sensitive output for generating a control signal as a function of the axial postion of the photosensitive element relative to the focal point; and second means responsive to the generated control signal for moving the photosensitive element toward the focal point.

Claim 3

A system having a given optical axis for locating upon the optical axis a focal point of a scanning beam of light having a cone shaped locus of scan defined from a cone apex disposed at the focal point, the direction of the scan of the beam inverting at the focal point, the system, comprising: a photodetector having a photosensitive element substantially disposed on the given optical axis and movable along the given optical axis, for generating a phase-sensitive output as a function of the direction of scan of the beam across the photosensitive elemeNt; first means responsive to the phase-sensitive output for generating a control signal as a function of the axial postion of the photosensitive element relative to the focal point; and second means responsive to the generated control signal for moving the photosensitive element toward the focal point.

Claim 4

A system having a given optical axis for locating upon the optical axis a focal point of a scanning beam of light having a cone shaped locus of scan defined from a cone apex disposed at the focal point, the direction of the scan of the beam inverting at the focal point, the system, comprising: a photodetector having a photosensitive element substantially disposed on the given optical axis and movable along the given optical axis, for generating a phase-sensitive output as a function of the direction of scan of the beam across the photosensitive elemeNt; first means responsive to the phase-sensitive output for generating a control signal as a function of the axial postion of the photosensitive element relative to the focal point; and second means responsive to the generated control signal for moving the photosensitive element toward the focal point.

Claim 12

A system having a given optical axis for locating upon the optical axis a focal point of a scanning beam of light having a cone shaped locus of scan defined from a cone apex disposed at the focal point, the direction of the scaN of the beam inverting at the focal point, the system comprising: a photodetector unit including two photosensitive elements, each of which has a photosensitive surface thereon, the photosensitive surfaces facing the beam, movable along the optical axis, and operable to generate a phase-sensitive output, as a function of the direction of scan of the beam across the photosensitive surfaces, a digital comparator for generating in response to the phase-sensitive output from the photosensitive surfaces, a signal indicative of the axial position of the photosensitive surfaces relative to the focal point, and an electro-mechanical feedback loop responsive to the generated signal for moving the two photosensitive surfaces toward the focal point.

Claim 13

A system having a given optical axis for locating upon the optical axis a focal point of a scanning beam of light having a cone shaped locus of scan defined from a cone apex disposed at the focal point, the direction of the scaN of the beam inverting at the focal point, the system comprising: a photodetector unit including two photosensitive elements, each of which has a photosensitive surface thereon, the photosensitive surfaces facing the beam, movable along the optical axis, and operable to generate a phase-sensitive output, as a function of the direction of scan of the beam across the photosensitive surfaces, a digital comparator for generating in response to the phase-sensitive output from the photosensitive surfaces, a signal indicative of the axial position of the photosensitive surfaces relative to the focal point, and an electro-mechanical feedback loop responsive to the generated signal for moving the two photosensitive surfaces toward the focal point.

Claim 18

A system for locating a light beam focal point disposed along a given optical axis of the beam of light in an electronic retinoscope for testing refraction of an eye, the beam of light is a scanning beam of light and has a cone shaped locus of scan defined from a cone apex disposed at the focal point, the axial location of the focal point serving as an indication of the refractive condition of the eye in the meridian scanned by the beam, there being an inversion of the direction of scan of the beam at the focal point, the system comprising: a photodetector unit including a peak detector and a photodetector movable along the optical axis; the photodetector including two photosensitive elements each of which has a photosensitive surface, the photosensitive surfaces facing the beam, disposed adjacent to the optical axis, and opposite each other about the optical axis, eacH of the photosensitive surfaces operable to generate separate output signals, respectively, as a function of the light intensity incident on the surfaces, the output signals are phase related as a function of the direction of scan of the light beam across the photodetector; the peak detector including two channels one each coupled to the outputs from the photosensitive surfaces for detecting the peak amplitudes of the signals generated by the photosensitive surfaces and generating therefrom two trigger signals having the same phase relationship as the output signals from the photosensitive surfaces; a digital comparator for comparing the relative phase of the two trigger signals and for generating in response thereto a digital output signal indicative of the directional axial position of the photosensitive surfaces relative to the focal point; and an electro-mechanical negative feedback loop which in response to the digital output signal moves the photodetector module along the optical axis toward the focal point whereby when the photosensitive surfaces reach the focal point, the photosensitive surfaces are scanned simultaneously, at which time the focal point has been located.

Claim 19

A system for locating a light beam focal point disposed along a given optical axis of the beam of light in an electronic retinoscope for testing refraction of an eye, the beam of light is a scanning beam of light and has a cone shaped locus of scan defined from a cone apex disposed at the focal point, the axial location of the focal point serving as an indication of the refractive condition of the eye in the meridian scanned by the beam, there being an inversion of the direction of scan of the beam at the focal point, the system comprising: a photodetector unit including a peak detector and a photodetector movable along the optical axis; the photodetector including two photosensitive elements each of which has a photosensitive surface, the photosensitive surfaces facing the beam, disposed adjacent to the optical axis, and opposite each other about the optical axis, eacH of the photosensitive surfaces operable to generate separate output signals, respectively, as a function of the light intensity incident on the surfaces, the output signals are phase related as a function of the direction of scan of the light beam across the photodetector; the peak detector including two channels one each coupled to the outputs from the photosensitive surfaces for detecting the peak amplitudes of the signals generated by the photosensitive surfaces and generating therefrom two trigger signals having the same phase relationship as the output signals from the photosensitive surfaces; a digital comparator for comparing the relative phase of the two trigger signals and for generating in response thereto a digital output signal indicative of the directional axial position of the photosensitive surfaces relative to the focal point; and an electro-mechanical negative feedback loop which in response to the digital output signal moves the photodetector module along the optical axis toward the focal point whereby when the photosensitive surfaces reach the focal point, the photosensitive surfaces are scanned simultaneously, at which time the focal point has been located.

Claim 22

A system having a given optical axis for locating upon the optical axis the focal point of a scanning beam of light in an electronic retinoscope, the scanning beam of light having a conical locus of scan with the apex thereof at the focal point, the axial position of the focal point being an indication of the refractive condition of an eye being tested by the electronic retinoscope in the meridian being scanned by the beam, there being an inversion of the direction of scan of the beam at the focal point, the system, comprising: a photodetector section including a photodetector module and a peak detector; the photodetector module including two photosensitive elements each respectively connected to two associated amplifiers forming two channels, the photodetector module being movable along the optical axis; each of the photosensitive elements having a photosensitive surface, the photosensitive surfaces facing toward the beam, each surface being disposed closely adjacent to and on opposite sides of the axis extending through the cone apex and generally in the direction of the light beam, the photosensitive surfaces generating an output signal as a function of the light beam intensity incident thereon, the relative phase of the two output signals being indicative of the direction of scan of the light beam across the photodetector module; the peak detector section includes two channels coupled to the respective outputs of the channels of the photodetector module, each channel comprising an automatic gain control amplifier to stabilize the amplitudes of the output signal from the photodetector module, and a peak detector circuit coupled to the automatic gain control amplifier for detecting the peak amplitudes of the output signal and generating therefrom a trigger signal, the two trigger signals having the same phase relationship as the output signals from the photodetector module; reset means for generating a referEnce signal having a predetermined phase relationship to the scan of the scanning beam of light; a digital comparator comprising two bistable switching circuits and a phase detector circuit, the bistable switching circuits being coupled between the output from each channel in the photodetector section and an input of the phase detector circuit, the bistable circuits being switchable from a predetermined first state to a second state by the trigger signals generated in the photodetector section, the phase detector circuit generating a digital output signal in response to the two signals from the bistable switching circuits, the digital output signal being indicative of the axial position of the photosensitive surfaces relative to the focal point; the reset means for generating a reference signal being coupled to an input of each of the bistable switching circuits whereby the bistable switching circuits may be reset to a predetermined initial state after each scan of the scanning beam of light across the photosensitive surfaces; and an electro-mechanical negative feedback loop responsive to the digital output signal for moving the photodetector module along the optical axis toward the focal point whereby when the photosensitive surfaces are scanned simultaneously, the photosensitive surfaces are disposed at the focal point.

Claim 23

A system having a given optical axis for locating upon the optical axis the focal point of a scanning beam of light in an electronic retinoscope, the scanning beam of light having a conical locus of scan with the apex thereof at the focal point, the axial position of the focal point being an indication of the refractive condition of an eye being tested by the electronic retinoscope in the meridian being scanned by the beam, there being an inversion of the direction of scan of the beam at the focal point, the system, comprising: a photodetector section including a photodetector module and a peak detector; the photodetector module including two photosensitive elements each respectively connected to two associated amplifiers forming two channels, the photodetector module being movable along the optical axis; each of the photosensitive elements having a photosensitive surface, the photosensitive surfaces facing toward the beam, each surface being disposed closely adjacent to and on opposite sides of the axis extending through the cone apex and generally in the direction of the light beam, the photosensitive surfaces generating an output signal as a function of the light beam intensity incident thereon, the relative phase of the two output signals being indicative of the direction of scan of the light beam across the photodetector module; the peak detector section includes two channels coupled to the respective outputs of the channels of the photodetector module, each channel comprising an automatic gain control amplifier to stabilize the amplitudes of the output signal from the photodetector module, and a peak detector circuit coupled to the automatic gain control amplifier for detecting the peak amplitudes of the output signal and generating therefrom a trigger signal, the two trigger signals having the same phase relationship as the output signals from the photodetector module; reset means for generating a referEnce signal having a predetermined phase relationship to the scan of the scanning beam of light; a digital comparator comprising two bistable switching circuits and a phase detector circuit, the bistable switching circuits being coupled between the output from each channel in the photodetector section and an input of the phase detector circuit, the bistable circuits being switchable from a predetermined first state to a second state by the trigger signals generated in the photodetector section, the phase detector circuit generating a digital output signal in response to the two signals from the bistable switching circuits, the digital output signal being indicative of the axial position of the photosensitive surfaces relative to the focal point; the reset means for generating a reference signal being coupled to an input of each of the bistable switching circuits whereby the bistable switching circuits may be reset to a predetermined initial state after each scan of the scanning beam of light across the photosensitive surfaces; and an electro-mechanical negative feedback loop responsive to the digital output signal for moving the photodetector module along the optical axis toward the focal point whereby when the photosensitive surfaces are scanned simultaneously, the photosensitive surfaces are disposed at the focal point.