Photography – With exposure objective focusing means – focusing aid – or...
Patent
1997-07-10
1998-09-15
Perkey, W. B.
Photography
With exposure objective focusing means, focusing aid, or...
396342, 396437, G03B 500, G03B 508, G03B 1336
Patent
active
058093494
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a focusing process for a camera, said camera: positionally relative to one another in a straight line optical bench direction in which the spatial interval between them is variable, wherein the said interval changes are signaled to a microprocessor, to pivot about two axes, said axes being vertical to one another and to an optical bench, the two respective objective lens angles and the focal length of said lens being input to a processor, glass plate is secured, which screen is moveable about two axes vertically disposed to one another and to the direction of the bench, the two respective image reception angles being sent to the processor, degree of focus, and is positionable in two image reception coordinates which, together with the focus value, are conducted to the processor, secondary image plane for the simultaneous adjustment of the focus, determination of their respective image screen coordinates by means of a change in the interval between the image carrier and the objective lens sequentially for each area through focus adjustment, and the said positional changes of the image carrier are input to the processor, computer a determination of the positional parameters of the image screen as well as of the secondary image from which, together with a further image parameter necessary for computation, this latter originating in the solution of image equations, there will be calculated fixed adjustment values suitable for the pivoting of the objective lens carrier along with a value for the adjustment of the interval between the carriers of the image and the objective carrier, the results thereof being made available, so that the new image plane adjusted by these set-point values comes as close as possible to coinciding with the image screen.
A camera of this type is brought into common knowledge by DE 34 33 412 C2. In this case, were determined from the optical imagery of a scale of the image, to which purpose a focus sensor serves as an aid, and degrees of deviation, to the image screen, measured values.
From these data the processor computes the set point signal for the adjustment angle and the said interval. In this computation, the processor makes use of the Law of Scheimpflug according to which, the objective lens plane, the plane to which the real image belongs and the plane to which the focused image points belong, must mandatorily intersect in one straight line.
Thus, in accord with a preset adjustment, the selected image point area of the real subject, by means of the so called double focus compensation, is imaged as sharply as possible. With this apparatus, in addition the absolute space coordinates of the image points and the structural data of the imagery optics are required as starting point values for a final solution of the image equations. This is in order to find such a position of the image screen in relation to the setting of the objective lens, that the select image point areas lie with the sharpest possible focus in the image screen. This requires a substantial array of means of measurement having high requirements as to precision. Moreover, the Law of Scheimpflug, which was employed, is valid only for the imagery in a paraxial zone of a thin lens, making it of little meaning in practice.
Thus, it is the purpose of the invention, to achieve an automatic focus adjustment of a real image, using the camera described in the introductory passages, employing double focus compensation with the reduced demand for measurement equipment, simplified apparatus and an objective lens acceptable in practice.
The accomplishment of this purpose lies therein, in that one of the objective lens adjustment parameters can be altered in given quantity, and as this is carried out, for a selected image point, the extension difference of a extension adjustment apparatus lying between its two focus adjustments in the bench direction, is measured. This brings about a first set of the of the image equations by the use of the original objective lens adjustment parameters and an undetermined
REFERENCES:
patent: 5027143 (1991-06-01), Clark, III et al.
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