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Browse Prior Art Database

Pneumatic Autofocus Mechanism

IP.com Disclosure Number: IPCOM000121092D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 3 page(s) / 125K

Publishing Venue

IBM

Related People

Hsieh, DS: AUTHOR [+3]

Abstract

A mechanism has been proposed for providing micron resolution dynamic autofocusing. The proposed mechanism is pneumatic in nature, not optical, and thus independent of material properties, such as reflectivity and photosensitivity that are inherent to optical techniques.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Pneumatic Autofocus Mechanism

      A mechanism has been proposed for providing micron
resolution dynamic autofocusing.  The proposed mechanism is pneumatic
in nature, not optical, and thus independent of material properties,
such as reflectivity and photosensitivity that are inherent to
optical techniques.

      Fig. 1 displays the components of the mechanism.  The system
has a double acting frictionless air cylinder with upper and lower
chambers, a piston/rod assembly, and a nozzle 1.  This nozzle can be
placed in close proximity to the objective lens of an imaging system,
as shown in Fig. 1, or it can be integrated into the housing of the
lens and surround the point of focus.  This will ensure that the
mechanism maintains the proper point of the object in focus with the
focal point of the imaging system.  The driving energy of the
autofocus system is provided by a regulated air supply, thus no
supporting electronics are needed.  This supply, typically, 30 psi,
is split and delivered to both the lower chamber and the nozzle.  The
lower chamber has a bleed hole which maintains a reference pressure
of 15 psi, half of the supply.  The nozzle exhausts to the top
surface of the object to be focused.  The back pressure from the
nozzle, determined by the gap 2 between the nozzle and the object is
fed to the upper chamber.

      When initially turned on, the piston travels up or down until
the back pressure in the upper chamber is equivalent to the reference
pressure in the lower chamber, 15 psi.  The gap created at this
equilibrium position is the fly height of the system.  This gap
distance is dependent on the nozzle orifice as well as supply
pressure.  As topology of the object to be focused is encountered
through lateral scanning, the piston will react to precisely maintain
the fly height.  By keeping the nozzle stationary relative to
whatever the object needs to be in focus with, such as a lens, the
mechanism will move the object up and down to maintain a constant
distance from lens to object without the need for feedback
electronics to drive an external stage.  The mechanism operates o...