Zone range finder apparatus

Claim 2

In zone type range finder apparatus for determining whether an object is disposed within a first range of distances relative to a reference plane or a second range of distances relative to the reference plane and including means for projecting a beam of light towards an object and first and second photosensitive devices, with each device having a parameter the magnitude of which varies as a function of the brightness of incident illumination reflected from the object, the combination comprising: a. means coupled to said first and second photosensitive devices for producing a signal the magnitude and polarity of which varies in accordance with changes in the magnitude of the parameters of the first and second photosensitive devices, said signal having a first polarity when said object is disposed in said first range of distances and a second polarity when said object is disposed in said second range of distances; and b. means responsive to said signal having said first polarity and having a magnitude greater than a predetermined level in said first polarity for indicating that said object is in said first range of distances and responsive to said signal having said second polarity and having a magnitude less than a predetermined level in said second polarity for indicating said object is in said second range of distances.

Claim 3

The invention as set forth in claim 1 wherein said signal producing means comprises a differential amplifier and said signal responsive means comprises logic circuitry.

Claim 4

The invention as set forth in claim 1 wherein said range finding apparatus is an automatic focusing apparatus having means an objective lens and for moving said objective lens to a first position for focusing an image of the object in the reference plane when the object is in said first range of distances and for moving said objective lens to a second position when the object is in said second range of distances.

Claim 5

The invention as set forth in claim 1 wherein said signal responsive means comprises a lamp and means for projecting an image when said lamp is energized to indicate that the object is disposed in said particular range of distances.

Claim 6

In zone type rangefinder apparatus for determining whether an object is disposed within a first range of distances relative to a reference plane or a second range of distances relative to the reference plane and including means for projecting a pulsated beam of light at a predetermined frequency towards an object and first and second photosensitive devices each having a parameter the magnitude of which varies as a function of the brightness of incident illumination reflected from the object, the combination comprising: a. means coupled to the first and second photosensitive devices and including signal filtering means for passing a filtered signal at said predetermined frequency having a magnitude and polarity which varies in accordance with changes in the magnitude of the parameters of the first and second photosensitive devices, said filtered signal having a first positive polarity taken with respect to a reference level when the object is disposed in the first range of distances and a second negative polarity taken with respect to the reference level when the object is disposed in the second range of distances; b. logic means responSive to said signal for producing a first logic signal when said filtered signal is in said first polarity at a magnitude greater than a predetermined positive level taken with respect to the reference level and a second logic signal when said filtered signal is in said second polarity at a magnitude less than at predetermined negative level taken with respect to the reference level; and c. indicating means including first means responsive to said first logic signal for indicating that the object is disposed in the first range of distances and second means responsive to said second logic signal for indicating that the object is disposed in the second range of distances.

Claim 7

In zone type rangefinder apparatus for determining whether an object is disposed within a first range of distances relative to a reference plane or a second range of distances relative to the reference plane and including means for projecting a pulsated beam of light at a predetermined frequency towards an object and first and second photosensitive devices each having a parameter the magnitude of which varies as a function of the brightness of incident illumination reflected from the object, the combination comprising: a. means coupled to the first and second photosensitive devices and including signal filtering means for passing a filtered signal at said predetermined frequency having a magnitude and polarity which varies in accordance with changes in the magnitude of the parameters of the first and second photosensitive devices, said filtered signal having a first positive polarity taken with respect to a reference level when the object is disposed in the first range of distances and a second negative polarity taken with respect to the reference level when the object is disposed in the second range of distances; b. logic means responSive to said signal for producing a first logic signal when said filtered signal is in said first polarity at a magnitude greater than a predetermined positive level taken with respect to the reference level and a second logic signal when said filtered signal is in said second polarity at a magnitude less than at predetermined negative level taken with respect to the reference level; and c. indicating means including first means responsive to said first logic signal for indicating that the object is disposed in the first range of distances and second means responsive to said second logic signal for indicating that the object is disposed in the second range of distances.

Claim 8

The invention as set forth in claim 5 wherein said indicating means comprises automatic focusing means having an objective lens and including means for positioning the object lens to focus an image of the object in the reference plane in response to said first and second logic signals.

Claim 9

The invention as set forth in claim 5 wherein said first means comprises a first lamp and means responsive to said first logic signal for energizing said first lamp and wherein said second means comprises a second lamp and means responsive to said second logic signal for energizing said second lamp.