US 12,072,286 B2
Methods and apparatus for a self-aligned digital projection and reflected glare reduction imaging system
Brett F. Bathel, Yorktown, VA (US); and Joshua M. Weisberger, Newport News, VA (US)
Assigned to UNITED STATES OF AMERICA AS REPRESENTED BY THE ADMINISTRATOR OF NASA, Washington, DC (US)
Filed by UNITED STATES OF AMERICA AS REPRESENTED BY THE ADMINISTRATOR OF NASA, Washington, DC (US)
Filed on Sep. 30, 2021, as Appl. No. 17/490,612.
Claims priority of provisional application 63/163,290, filed on Mar. 19, 2021.
Prior Publication US 2022/0299437 A1, Sep. 22, 2022
Int. Cl. G01N 21/45 (2006.01); G01N 21/958 (2006.01); G02B 27/54 (2006.01)
CPC G01N 21/455 (2013.01) [G01N 21/958 (2013.01); G02B 27/54 (2013.01)] 14 Claims
OG exemplary drawing
 
1. A digital projection focusing optical system for measuring a test object in a test section of an instrument, comprising:
a beam splitter configured to reflect an incident linear vertically polarized (LVP) light from a light source along an optical axis of the optical system;
an LCD element positioned to receive the LVP light from the beam splitter, wherein the LCD element comprises a selectable pixel element configured to:
generate a source grid comprising regions of the selectable pixel element switchable between a transparent state and an opaque state; and
rotate the LVP light by ninety degrees to be liner horizontally polarized (LHP) light when regions of the generated source grid are in the transparent state;
a polarizing prism configured to receive the LHP light from the LCD element and split the LHP light into two light beams, wherein:
a first light beam comprising LHP light is refracted by a small angle relative to the optical axis and exits the polarizing prism at that small angle; and
a second light beam comprising LVP light continues along and exits the polarizing prism aligned with the optical axis;
a quarter-wave plate positioned between the polarizing prism and a retroreflective background, wherein the quarter-wave plate is configured to:
modify the LVP light exiting the polarizing prism to right circularly polarized (RCP) light; and
modify the LHP light exiting the polarizing prism to left circularly polarized (LCP) light; and
an imaging lens positioned between the LCD element and the test section, wherein the imaging lens is configured to project the generated source grid onto the retroreflective background, wherein:
the retroreflective background is configured to:
reflect the incoming RCP light back towards the quarter wave plate and reverse the RCP light to LCP light;
reflect the incoming LCP light back towards the quarter wave plate and reverse the LCP light to RCP light; and
reflect an image of the projected source grid; and
the imaging lens projects the reflected image of the source grid back onto the LCD element.