Photoelectric system and method for detecting the longitudinal location of surfaces

Claim 2

In a focusing method for photoelectric detection of longitudinal locations by revealing deformations in a wave surface in the plane of a puPil by its differentiated shape obtained by interferometry of two wave surfaces due to duplication of the pupil of an instrument having a tube, this duplication being effected by means of a double refracting wave duplicator, the improved steps comprising: alternately modulating the tube of the instrument so as to create a focusing error alternating with respect to that plane of the image which would correspond to perfect focusing without modulation, creating a variable photoelectric signal by means of a photoreceiver responsive to variations in light flux transmitted by an interferometer located in a portion common to the two waves in the plane of the pupil, processing the photoelectric signal to obtain an error signal, and controlling the displacement between the objective and the object along the optical axis in response to said error signal to complete focusing.

Claim 3

A focusing system for photoelectric detection of longitudinal locations by revealing deformations in a wave surface in the plane of a pupil by its differentiated shape obtained by interferometry of two wave surfaces due to duplication of the pupil of an instrument, comprising: A. an object to be focused upon illuminated by a light source and disposed in an image plane of an objective, B. a crystalline wave duplicator operating by refraction and disposed between crossed polarizers to permit duplication of an exit pupil of the objective in a rear focal plane of the objective, thereby producing two waves having respective wave surfaces, C. means for alternately modulating a focusing error, D. a receiver photosensitive to illuminations due to the interference of the two wave surfaces in the plane of the duplicated pupil, and E. means activated by the receiver for determining or adjusting the location of the object with respect to the objective.

Claim 4

A focusing system for photoelectric detection of longitudinal locations by revealing deformations in a wave surface in the plane of a pupil by its differentiated shape obtained by interferometry of two wave surfaces due to duplication of the pupil of an instrument, comprising: A. an object to be focused upon illuminated by a light source and disposed in an image plane of an objective, B. a crystalline wave duplicator operating by refraction and disposed between crossed polarizers to permit duplication of an exit pupil of the objective in a rear focal plane of the objective, thereby producing two waves having respective wave surfaces, C. means for alternately modulating a focusing error, D. a receiver photosensitive to illuminations due to the interference of the two wave surfaces in the plane of the duplicated pupil, and E. means activated by the receiver for determining or adjusting the location of the object with respect to the objective.

Claim 5

A system according to Claim 2 comprising: a light source providing, through an appropriate condensor means, a light beam passing through: A. a polarizer, then B. a polarizing interferometer which includes either one or more Wollaston prisms or derivatives of a Wollaston prism, C. said objective being aplanetic and fully corrected for geometric and chromatic aberrations in the image plane in which are positioned the interference fringes from the interferometer, and D. an adjustable aperture diaphragm and a field diaphragm, being effectively placed in the image plane of the objective and in the plane of its exit pupil respectively, E. the beam then reflecting onto the object and passing again through the objective, F. the beam then reflecting onto a mirror which is moved by an alternating movement enabling the modulation of the tube length, G. the beam then passing through an analyser in crossed relation with the polarizer before reaching, H. a photosensitive receiver, the output of this receiver device being connected to means adapted to put the signal in form for synchronous detection, thereby allowing the production of an error signal to enable automatic focusing by a displacement of at least the objective and of the object relatively to one another.

Claim 6

An arrangement according to claim 3 in which the error signal causes displacement of at least one of the objective and the object to focus the arrangement.

Claim 7

A focusing arrangement according to claim 3 wherein the interferometer is fixed to a vibrating element and is a derivative of a Wollaston prism, and is provided with its own interference fringe pattern perpendicular to the optical axis to be used in the large values of duplication requiring a large prism angle.

Claim 8

A focusing arrangement according to claim 3 further comprising a double refraction duplicator with variable duplication to function as at least one of the interferometers.