Multiple frequency ranging apparatus for focus control
First Claim
Patent Images
1. A multiple frequency ranging apparatus for measuring the distance between an object and a reference plane comprising:
- oscillator means for generating signals at first and second frequencies, the second frequency being higher than the first frequency;
wave generating means connected with the oscillator means and associated with the objects and reference plane for producing energy waves characterized by the first and second frequencies and transmitting the waves between the object and the reference plane;
wave receiving means associated with generating means for receiving the waves transmitted by the generating means between the object and the reference plane;
detecting means having an input connected with the receiving means for detecting from the waves the distance between the object and the plane at the first frequency and the second frequency; and
control means associated with the detecting means for switching the detection of the distance between the object and the plane from the first frequency for coarse detection to the second frequency for fine detection.
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Abstract
A photoplotter includes an autofocus control for maintaining a precise focal distance between a photohead in the plotter and the film surface which is exposed by the head. The autofocus control employs a dual frequency ultrasonic ranging apparatus which permits coarse focus control at one frequency and fine focus control at a second, higher frequency.
15 Citations
25 Claims
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1. A multiple frequency ranging apparatus for measuring the distance between an object and a reference plane comprising:
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oscillator means for generating signals at first and second frequencies, the second frequency being higher than the first frequency; wave generating means connected with the oscillator means and associated with the objects and reference plane for producing energy waves characterized by the first and second frequencies and transmitting the waves between the object and the reference plane; wave receiving means associated with generating means for receiving the waves transmitted by the generating means between the object and the reference plane; detecting means having an input connected with the receiving means for detecting from the waves the distance between the object and the plane at the first frequency and the second frequency; and control means associated with the detecting means for switching the detection of the distance between the object and the plane from the first frequency for coarse detection to the second frequency for fine detection. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. In an optical apparatus having an optical mechanism with a lens system for focusing on a generally planar work surface and means for adjusting the focus of the optical mechanism on the work surface, an improved focus control comprising:
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transmitting means and receiving means for sending and receiving respectively an energy wave along a wave path between the optical mechanism and the work surface, the transmitting means producing discrete energy waves at more than one characteristic frequency, and the receiving means receiving the waves at the same characteristic frequencies; detecting means connected with the receiving means for establishing from the received energy wave a measure of the correspondence between the focus of the lens system in the optical mechanism and the work surface and connected with the adjusting means for adjustment of the focus on the work surface; and control means associated with the transmitting means and the detecting means for switching the operation of the transmitting means between discrete waves at different characteristic frequencies as a function of the correspondence between the focus and the work surface. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. A photoplotter with autofocus control comprising:
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support means for holding a photosensitive film with the film surface disposed for exposure; an optical head for projecting images onto the photosensitive film for exposure and including a lens adjustable relative to the support means for focusing the projected images on the film surface; controlled carriage means for moving the optical head and the photosensitive film on the support means relative to one another in directions generally parallel to the film surface for exposing the film; motor means connected with the adjustable lens in the optical head for moving the lens and adjusting the focus of the images projected on the film surface; and an autofocus control connected with the motor means to hold the projected images in focus as the optical head and film are moved relative to one another while exposing the film including; wave generating and receiving means connected with the optical head for reflecting energy waves at a first and a second frequency between the optical head and the film surface, detecting means connected with the wave generating and receiving means for determining the distance between the optical head and the film surface in response to the reflected energy waves at the first and second frequency, and control means connected with the motor means moving the adjustable lens for adjusting the focus of the projected images in response to the distance determined by the detecting means, and also connected with the wave generating means for selectively controlling the generation of energy waves at the first and the second frequency. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25)
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Specification