Automatic focusing system for projectors and the like

Claim 1

A projection device of the type including an element for positioning a transparency on an optical axis defined by a movable objective lens mounted between such element and a screen remote from the device including, a system for automatically focusing a transparency image on said screen comprising; a. a first appraisal subsystem to sense variations in the distance between the objective lens and the screen including; 1. a first source of wave energy, 2. means for directing a beam of wave energy from said first source to the projection screen, and 3. first detection means adapted to receive wave energy reflected from the screen and responsive thereto to generate a first electircal pulse; b. a second appraisal subsystem to sense buckling of the transparency including: 1. a second source of wave energy, 2. a means for directing a beam of wave energy from the second source to the transparency, and 3. detection means positioned to receive wave energy reflected from the transparency and responsive thereto to generate a second electrical pulse; said first and second electrical pulses being in time phase with each other when the transparency image is focussed upon said screen and out of time phase with each other upon displacement of either the screen or the transparency as measured along the optical axis; c. control circuit means connected to said first and second detection means and adapted to produce a control signal representing the time phase differential between said first and second electrical pulses; and d. motive means operated by the control circuit means and responsive to the control signals to axially move the objective lens to establish focus of the screen image and bring the pulses generated by the two detection means into time phase.

Claim 25

A method for automatically positioning an objective lens on the optical axis of a projection device to establish focusing of transparency image on a remote projection screen comprising the steps of: a. directing a beam of wave energy from a wave energy source to a first detection means along paths which are defined in part by said wave energy being reflected from said screen; b. directing a second beam of wave energy from a wave energy source to a second detection means along paths which are defined in part by said wave energy beam reflected from said transparency; c. generating a first electrical pulse by said first detection means upon its illumination by the beam of wave energy reflected by said screen; d. generating a second electrical pulse by said second detection means upon its illumination by the beam of wave energy reflected from said transparency; e. electronically comparing said first and second electrical pulses to determine whether they are in time phase with each other, which occurs upon the simultaneous illumination of both the first and second detection means, and represents the focussed condition of the transparency on the screen; f. generating a control signal representing the time differential between said first and second electrical pulses; and g. driving reversible motive means with said control signal to move the objective lens of the projector in either a forward or reverse direction along the optical axis thereof, so as to establish a focussed condition of the image upon the screen and bring said first and second electrical pulses into time phase with each other.

Claim 26

A method for automatically positioning an objective lens on the optical axis of a projection device to establish focusing of transparency image on a remote projection screen comprising the steps of: a. directing a beam of wave energy from a wave energy source to a first detection means along paths which are defined in part by said wave energy being reflected from said screen; b. directing a second beam of wave energy from a wave energy source to a second detection means along paths which are defined in part by said wave energy beam reflected from said transparency; c. generating a first electrical pulse by said first detection means upon its illumination by the beam of wave energy reflected by said screen; d. generating a second electrical pulse by said second detection means upon its illumination by the beam of wave energy reflected from said transparency; e. electronically comparing said first and second electrical pulses to determine whether they are in time phase with each other, which occurs upon the simultaneous illumination of both the first and second detection means, and represents the focussed condition of the transparency on the screen; f. generating a control signal representing the time differential between said first and second electrical pulses; and g. driving reversible motive means with said control signal to move the objective lens of the projector in either a forward or reverse direction along the optical axis thereof, so as to establish a focussed condition of the image upon the screen and bring said first and second electrical pulses into time phase with each other.