A beam of coherent light is expanded and reparallelized by a single lens and a parabolic mirror. The beam then passes through the test region, which may be of any convenient size and impinges on a back surface mirror at 45 degrees. About 10 percent of the light is reflected from the front surface of the glass. This is slightly offset from the image reflected from the rear surface. Any refractive index gradients perpendicular to the direction of propagation then create fringes in the overlapping reflected images which may be visually observed or recorded directly on film.
A method for effecting adjustment of the focus and adjustment of the position of a condensing optical system by the steps of condensing coherent signal light beams on a substantially moving photosensitive body making use of the condensing optical system, having a reflected wave surface, which passes through again the condensing optical system from a condensing point, interfered with a reference wave surface coherent with the reflected wave surface, and observing interference fringes produced by the interference thereof.
A method and system for imaging unstained smaple material constituents on a gel electrophoresis unit. The system includes a gel electrophoresis unit, preferably having a pH gradient gel thereon, phase detection optics including a collimated light source, shearing interferometer, phase contrast microscope or schlieren microscope, an image digitizer, and data processing electronics, such as a computer, for determining the concentration of sample constituents at each position on the electrophoresis unit. The method relies on the difference in index of refraction between sample material and gel material to introduce optical path differences in light rays passing through the material. The modified light is subjected to shearing interferometry to locate gel-sample boundaries, phase imaging to directly image the sample, or a laser scanner for directly measuring the deviation in a light beam due to the sample.
An optical distortion analyzer system which is capable of automatically quantifying with a high degree of accuracy and repeatability the optical quality of transparencies such as windshields or windows. The analyzer system is made up of a platform adapted to support the transparency with two degrees of freedom. A probe beam of electromagnetic radiation emanating from, for example, a laser is passed through the transparency as the transparency is moved about a horizontal and vertical axis establishing a plurality of test points on the transparency. An analyzer unit receives the probe beam and therefrom establishes horizontal and vertical deviations in the transparency as well as determining the cylindrical and spherical lens power components and principal meridan angle of the transparency. A processor provides recognizable opthalmic parameters of the above characteristics of the transparency and correlates these parameters with the plurality of test points on the transparency.
A retroreflective type focusing schlieren system which permits the light source to be positioned on the optic side of the system. The system includes an extended light source, as opposed to a point source, located adjacent a beam splitter which projects light through the flow field onto a reflecting grating in the form of a grid which generates sheets of light that are directed back through the flow field and the beam splitter onto a primary lens behind which is located a cut-off grid having a grid pattern which corresponds to the grid pattern of the reflecting grating. The cut-off grid is adjustably positioned behind the primary lens and an image plane for imaging the turbulence is adjustably located behind the cut-off grid.
The present invention provides an apparatus and method to automatically focus an incident beam of monochromatic parallel planar light on a work piece, using a fringe plate and a vision detector. The work piece may have a perfect mirror surface, or have a non-reflective patterned surface. The incident light beam is focused on the work piece and then reflected through a fringe plate forming an interference pattern on the vision detector. The incident light beam is then scanned or wobbled. The wobbling incident light beam forms a distinctively oscillating output signal from the vision detector when the light is focused on the work piece. When the light is not focused on the work piece a distinctive and more constant output signal is produced by the vision detector. For a given position of the work piece, by noting whether the output signal is rapidly changing or relatively constant, the invention can automatically determine whether or not the work piece is at the focal point of the incident light beam. This can be used to automatically focus the etching or writing laser on the chip or wafer in a laser etching system. The present invention can also be used to automatically determine the focal surface of an objective lens.
