초록 ▼

Change of distance measuring apparatus features a light transmitter - receiver unit 23 which is used to sense the distance A to the surface of a measurement object 35 and more particularly to sense changes in the distance A occurring due to changes in thickness of the measurement object 35 as it mov

Change of distance measuring apparatus features a light transmitter - receiver unit 23 which is used to sense the distance A to the surface of a measurement object 35 and more particularly to sense changes in the distance A occurring due to changes in thickness of the measurement object 35 as it moves against a guide surface in the direction of the arrow F. The optical system features a front objective 14 which focuses a parallel beam of light received from a laser light source via beam widening optics 13′, 13″, a modal aperture 12 for limiting the beam to the zero order diffraction image of the laser light source and a beam dividing mirror 33. Light returned from the surface of the measurement object whether specularly reflected or scattered is gathered by the front objective 14 and is passed to a photoelectric converter 19 via the dividing mirror 33, a further objective 16 and a second modal aperture stop 18. The signal at the photoelectric converter 19 is a maximum when the surface of the measurement object 35 is located in the desired plane 15. The position of the desired plane can be adjusted by optical means such as moving the front lens 14 and the extent of the movement required to maximize the signal at the photoelectric converter 19 is indicative of the change in the distance A. Various useful modifications are disclosed including the use of a comparison beam 36.

대표청구항 ▼

Change of distance measuring apparatus for measuring the change of a distance from a datum to a surface, the apparatus comprising a monochromatic laser light source for generating a laser light beam, means limiting the laser light beam emitted from said source to the zero order diffraction beam, bea

Change of distance measuring apparatus for measuring the change of a distance from a datum to a surface, the apparatus comprising a monochromatic laser light source for generating a laser light beam, means limiting the laser light beam emitted from said source to the zero order diffraction beam, beam widening means for spreading the zero order diffraction beam into a parallel beam of light, a front objective positioned to receive said parallel beam of light and to bring the same to a point focus, adjusting means for adjusting the position of said point focus to bring the same into substantial coincidence with said surface without varying the parallelism of said parallel beam of light, means for producing high frequency cyclical variation of the position of said point focus without disturbing the parallelism of said beam of light, beam dividing means located in said parallel beam of light between said beam widening means and said front objective, said beam dividing means being adapted to pass at least a fraction of said parallel beam of light to said objective and to direct light returned through said front objective from said surface to a second objective, means defining a modal aperture stop at the focal plane of said second objective which allows only a zero order diffraction image of the light source to pass, photoelectric converter means positioned to receive light from said zero order diffraction image and an electronic processing circuit for processing signals derived from said photoelectric converter means to produce a control signal for said adjusting means to bring said point focus into substantial coincidence with said surface.