Automatic focus control for a microscope

DETAILED DESCRIPTION The object of the present invention is a process and an apparatus which obviates this disadvantage.
Consequently the invention provides for the simultaneous formation of two images of the same object in two different image planes.
When the focusing of the microscope is optimum for the plane located in the centre of said two image planes, the focus controls of both images are the same.
According to the invention, the contrasts of the two images formed are compared and the microscope focusing is corrected so that the two contrasts are identical.
The significance of the invention is to increase the speed of correction because the comparison is no longer performed between two successive images but instead between two simultaneous images.
More precisely the invention has for its object a process for the automatic correction of the focusing of a microscope in an image plane wherein: two images of the same object are formed through two microscope outputs, said two images being formed in two different planes surrounding the image plane; the light intensity of the different points of the two images is detected by means of two photo-detector matrices; on the basis of the signals contained in each of the photo-detectors the contrast of the two images is measured; the two measured contrasts are compared; a correction signal is produced which is a function of the variation between the said two contrasts; by means of the said signal the microscope focusing correction means are operated so as to eliminate the variation.
Preferably the correction means comprise a motor and the rotation of the motor is controlled by producing a fixed amplitude signal which is transmitted to the motor when a variation exists between the contrasts.
The present invention also has for its object an apparatus for the automatic correction of the focusing of a microscope in an image plane wherein it comprises: two microscope outputs forming two images of the same object in two different planes surrounding said image plane; two matrices with at least one line of N photodetectors receiving the two images formed by the microscope; a contrast measuring circuit of each image associated with each matrix; a comparator of the signals supplied by the two contrast measuring circuits; a circuit for the formation of a correction signal connected to the output of the comparator; means for correcting the focusing of the microscope controlled by said signal