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US 4,538,913 AGranted
Flatness testing apparatus and method
AssigneeOptical Coating Laboratory, Inc.
InventorErik W. Anthon
Life of this patent
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AssigneeOptical Coating Laboratory, Inc.
InventorErik W. Anthon
Estimating the term…
Flatness testing apparatus for testing the flatness of a surface of a body of material a source of substantially monochromatic light for producing a light beam. First and second reticles are provided which are capable of passing the light beam. Means is provided for sensing light from the light source after it has passed through the reticles. An objective lens is provided which is adapted to be disposed adjacent the surface of the body of material. A first lens is provided in front of the source of light for imaging the source of light onto the objective lens and a second lens is provided in front of the means for sensing light for imaging the objective lens onto the means for sensing light. A mirror is provided for receiving light from the light beam after it has passed through the first reticle and for reflecting light through the second reticle to the light sensing means. Means is provided for causing relative movement of the reticle images with respect to each other to cause modulation of the light beam in accordance with the flatness of the surface.
In an apparatus for testing the flatness of the surface of a body of material, a source of light for producing a light beam, a first light transmitting reticle passing the light beam, a second light transmitting reticle passing the light beam, an objective lens adapted to be disposed adjacent the surface of an object, a lens in front of the source of light for imaging the source of light onto the objective lens, means for sensing light from said source, a lens in front of the means for sensing light for imaging the objective lens onto the means for sensing light, a mirror for receiving light from the source of light passing through the first reticle and reflecting the received light through the objective lens onto the surface of the body and receiving light reflected from the surface of the body and reflecting the light received from the surface of the body through the second reticle and onto the light sensing means, means for focusing the image from the first reticle onto the second reticle and means for causing relative movement of the image of the first reticle and the second reticle with respect to each other to modulate the light beam received by the means for sensing light to ascertain the flatness of the surface of the object.
In an apparatus for testing flatness of the surface of a body of material, a source of substantially monochromatic light for producing a light beam, a first light transmitting reticle passing the beam of light, a second light transmitting reticle passing the light beam, an objective lens adapted to be disposed adjacent the surface of an object, a lens in front of the source of light for imaging the source of light onto the objective lens, means for sensing light from said source, a lens in front of the means for sensing light for imaging the objective lens onto the means for sensing light, a mirror for receiving light from the source of light passing through the first reticle and reflecting the received light through the objective lens onto the surface of the body and receiving light reflected from the surface of the body and reflecting the light received from the surface of the body through the second reticle and onto the light sensing means, means for forcusing the image from the first reticle onto the second reticle and means for causing relative movement of the image of the first reticle and the second reticle with respect to each other to modulate the light beam received by the means for sensing light to ascertain the flatness of the surface of the object, said means for causing relative movement including means for rotating the mirror and means for mounting the mirror so that it is tilted slightly from the plane which is perpendicular to the axis of rotation for the mirror.
In a method for testing the flatness of the surface of a body of material formed of glass utilizing first and second reticles, providing a source for a beam of light, causing the beam of light from the source to pass through the first reticle and to impinge in substantially collimated form by the use of a lens upon an area of the surface being tested and to pass through the second reticle so that the image of the first reticle is formed on the second reticle without the formation of an intermediate image of the first reticle, causing relative movement between the image of said first reticle and said second reticle to modulate the light beam, the sharpness of said image of said first reticle on said second reticle being relatively unaffected by changes in position of the test surface relative to the lens and being strongly affected by the degree of flatness of the test surface whereby when the test surface is flat, the image of the first reticle on the second reticle will be sharp and will produce a high level of modulation and when the test surface is uneven, the image of the first reticle on the second reticle will be less sharp and will produce a lower level of modulation, and sensing the amount of modulation of the light beam after it has passed through the first and second reticles to ascertain the flatness of the surface.
Dependencies are inferred from the claim text.