DD210359A1 - ARRANGEMENT FOR AUTOMATIC SHARPENING OF PHOTOGRAPHIC CAMERAS - Google Patents

Abstract

The object of the invention is to improve the focus by increasing the system sensitivity and lowering the Grenzleuchtdichte, wherein the Aufloesungsvermöegen the image division is essentially determined only by the Aufloesungsvermoegen the multiple Empfaengerarar. The object is achieved by an arrangement in which the measuring plane lies in a second image plane in which optical means are provided in a pupil plane for producing at least two identical images of a limited section of a first image plane in the second image plane and the identical images by means of a multiple Arrays can be disassembled into at least two sub-images, wherein from the brightness distribution of diametral pupil areas by comparison of the same image parts associated receivers of different fields the magnitude signal and including the comparison of the receivers within a field the direction signal for the focus deviation is obtained.

Description

:;:! ^; ^; ^ Ρ ^βΝ Dresden, on August 13, 1982

Title of the invention

  Arrangement for automatic focusing of photographic cameras. ,

Field of application of the invention

: 5 The invention relates to an arrangement for the automatic focusing of photographic cameras, in which the focus is evaluated by dependent · Abschattwirkung'erzeugte sanctity distribution of the exit pupil of the entire system in a measurement plane.

TO characteristic of the known technical solutions

It is known that the shadowing effect of a field stop in the exit pupil of a system can be detected photoelectrically by measuring the distribution of brightness.

Furthermore, it is known to divide the image of the object to be sharpened into partial images and thus make a pupil multiplication, wherein the photoelectric data acquisition is performed by multiple receiver arrays in the plane of the partial pupils. The crucial advantage of image splitting lies in the possibility of obtaining an unsigned signal while simultaneously increasing the sensitivity.

Π Λ P Γ Π J Λ r η η η -s ri .η r.

However, there are still significant disadvantages.

The resolution of the bi-division, and thus the system sensitivity, are limited by the limitations of producing the required optical means for division. In contrast, there is an unfavorable adaptation of Yielfach-part receiver, which do not work at optimal Futz-Stör ratios in the required thereby larger dimensions of the sub-receiver, but on the other hand with much smaller dimensions and ~ s 10 thus optimal Hutz-Stör-conditions are technologically produced ,

For explanation, it should be noted that the focus-dependent measurement effect (relative change of the focus signal at defocus by a fixed amount) increases immediately with the reduction of the field width and on the other hand, the border luminance (smallest processable object luminance depending on object contrast) is inversely proportional; to the root of the resolution (fields per mm) decreases.

Object of the invention ·

By applying the invention, the stated disadvantages are intended to be eliminated .

Explanation of the essence of the invention

The invention has the object of improving the focusing by increasing the system sensitivity and lowering the luminance limit by means of an arrangement in which the resolution of the image division is essentially determined only by the resolution of the Yielfach receiver array.

The object is achieved according to the invention by an optical arrangement in which the measuring plane is in 'one' second

, Image plane is located, are provided in the lying between the first and second image plane pupil plane optical means for generating at least two identical images of a limited section of a first image plane in 'the second image plane, and in which the identical images of the second image plane by means of a Multiple arrays can be disassembled into at least two partial images in each case, whereby the brightness distribution of diametric pupil regions is determined by comparison of the same image segments. associated receiver of different fields the. ,, Amount signal and taking into account the comparison of the receiver within a field the Richtungs.signal for the focus deviation is obtained. To perform the automatic focusing, it is furthermore necessary for at least two pupil lenses to be arranged in the pupil plane in diametral peripheral parts of the pupil in a first and / or a second direction perpendicular thereto. If the pupil lenses are arranged only in one direction, d, h _e there is a measuring; value processing in only one direction., this direction is preferably opposite to horizontal or ^; vertical 'object edges by an angle > χ, inclined. An improved embodiment of the arrangement according to the invention provides, in addition to the abovementioned diametrical pupil lenses, a central pupil lens (central image C) whose optical axis coincides with the optical axis of the photographic objective. The focal lengths of the pupil lenses are expediently dimensioned such that a reduction takes place in the second image plane with respect to the first image plane. As image limiting means, for example, a field stop is arranged in the first image plane. Furthermore, it is expedient that shielding diaphragms are provided between the images in the second image plane. For the practical application of the arrangement according to the invention, it is advantageous that those in the first image plane and in the following ones. Planes arranged optical components and the Viel-

Facharray are summarized into a compact module. For measuring value processing, the focusing arrangement is connected to a signal processing part such that (m-1) first differences 3 / L of assigned receivers

ger of two images A and B from diametrical parts of the pupil corresponding to IL = ν An - Bn I _. , . > and (m-1)

second differences M _{0 of} the receivers, one each of the

f 'T

two pictures corresponding to M ~ = ) An-f 1 - An \ " _Λ -, _Λ ^ 1 sin η - ι f». \, iii- ι

or IL = isn + 1.-BnL _Λ r _{m Λ} \ and the 2n Ι ιn = 1 ... (m-1 ;, sign of l / L and M ₂ ^ are determined, the sign of the focus deviation for each of the (m-1) .focus signals from the correspondence or mismatch of the signs of 1L "and M _2n , it is more advantageous according to the invention to derive the signal M- from a central image C which is involved in the formation of the" Signal 'M'

is not involved, and 'is multiplied by the signal Ml for Vo ssichengewinnung. The signs of the signals M _{1 and.} M ₀ can also by means of a logical in dsl

Circuit to be tested. Another feature of the arrangement according to the invention is that of m-1 'focus signals at least one signal directly or at least two signals are summed processed.

Execution example ;

The invention will be explained in more detail below using an exemplary embodiment. Show it .

Pig. 1 is a schematic representation of the arrangement according to the invention,

Pig. 2a, 2b arrangement variants of the pupil lenses, 'Fig. Figure 3 shows the imaging ratios on the -CCD array. and

Pig. 4 shows an exemplary embodiment of the arrangement according to the invention in an SR camera. ;

The Aufnahmeob.jektiv 2 forms according to Pig. 1 in an equivalent to the film plane first image plane 4 from the, the field stop 4 a limited image β of the object to be sharpened 1 from. The measuring field lens 5 arranged in the first "image plane 4" images the exit pupil 3 of the receiving objective 2 into the pupil plane 8. The pupil lenses 7a, 7b and 7c are arranged in the pupil plane 8 in the variant shown in FIG Image plane 9 three identical images 10a, 10b and 10c of the image 6 of the first image plane 4 on a Yielfach receiver array 10, eg, a CCD array according to Fig. 3. Between the pupil lenses 7a and 7c and 7c and 7b Shields 11a, 11b arranged.

Using a numerical example, the image sizes are briefly illustrated:

The picture size 6 is z. B, 4,8. * 4 * 8 mm. ,

The opening number k, * of the measuring system is given by the distance d _{o Λ} between the levels 8 and 4 and the diameter dg ;, the total pupil 8a, DiS measuring orifice number is "

^k M = ^ 4 ^ _{3f4 |}

^a 8a

if z. B. interchangeable lenses of the opening number for open panel k '= 2j8 to be used.

from that

follows for: 2. 3'id _{Q A} = 15: mm;

^d 8a = 4.4 mm

and a focal length of the pupil lenses 7a - 7c of about 2 mm. The image size on the OCD-Arfäy is thus approximately 0.74 ^; x 0 ', 74 mm.

If z. B. starting from a screening of the CCD array 10 of 40 sub-receivers per mm in the x and y direction, 3p 'results in a number of about 30 χ 30 Teilbildem (30 receiver lines to 30 Teilempfangerh). It is

the line indexing takes care of the orientation of the. Pupil lenses 7 (y-direction) identical. This has the consequence that only edge positions in the object can be evaluated perpendicular to the line blanking with maximum sensitivity.

Optimum sensitivity in both mutually perpendicular directions requires the lens arrangement shown in FIG . 3. 5 pupil lenses and a corresponding matrix structure of the CCD array (query in the x and y direction) for measured value processing. , ..

1.0 Opposite Pig. 3, the CCD array 10 can also consist of one line in the extreme case, the partial receiver either have a corresponding width in the x direction with respect to the x-dimension or purpose of ⁷ optimal energy balance 'is converged more optically in a known manner, the x-direction.

To obtain the total focus signal, first the sub-picture-corresponding independent focus signals are formed according to magnitude and sign (direction of the required adjustment / \ s of the objective). The total focus signal can then be the signal of a single arbitrarily selectable partial image or can be composed (summed) from the focus signals of a plurality of partial images (maximum m-1). The selection of certain partial images is based on ^: increasing the good yield of the system. '

For example, to eliminate a disturbing background (simultaneous presence of objects of different distances), it may be expedient to automatically select and further process only that part object with the smallest object distance by means of a computer program.

30; at ten. '. ,

Since the partial focus signals assigned to the differently located sub-objects pass through their full passages when

In this case, the partial focus signal whose zero crossing is closest to the hah adjustment limit is selected.

The amount formation takes place per sub-image by the comparison of the diametrically opposite pupils Ja and 7b, ie by forming a first difference M ^ _n associated partial images An, Bn of the images 10a and 10b,

M- "= S An - BnI , _M 1n 1 r η = 1 ... (m-1 )

^ - J

The sub-signal of each sub-receiver is thus determined by the integral image content of the corresponding sub-picture (strictly focused) and by the "shading effect of its translated into the first image plane 4 limit (aperture effect) in defocusing.

Since the difference in M sequence depending on the brightness H / D or D / S ά in the picture no clear sign: & ^ ^': -I> efol ^ 3B ± ai ^ § ^r - A's ^ft ^ ß ^ ip ^' ^:) . -a '- unique' · direction determination is required. This is done in the image 10c by comparing the corresponding partial image On with the adjacent partial image, z, B. Cn + 1,. according to the formation of a second difference.

JZL- = Gn + 1 - Cn f " _Λ ,. ₁ s 2n 1 ι η = 1, ·. (M-1;

Ss turns out that the change in the brightness sequence, z. 3. D / H - H / D changes both the sign of the first difference 2 / L and the sign of the second difference Mp.

For this reason, the sign of the focus signal is unequivocally positive, and the two terms have the same sign and negative, if both differences

have unequal sign or vice versa. This can be checked by a simple logic circuit, Da3 same result is obtained if both differences, M. and JJL _{n are} multiplied. The image 10a or 10b can also be used to form the differences Mp _n , in which case the central pupil lens 7c and thus also the image 10c are omitted. However, it has to be taken into account that, with larger defocusing due to shadowing and lateral image shift, sign distortion can occur.

This sign distortion is sufficiently limited if pupil parts are used to form the difference Mp _n , which are as close as possible ^; ; lie on the optical axis of the system.

For this reason dia ::. ^v y-off stretch of Pupil lenlinse 7c possible klein.und the lens surface of the lenses 7a and 7b as possible, be the same.

When focusing, the difference undergoes IvL case, the difference Mu is independent of the defocusing

always unlike Hull, as long as there is sufficient contrast. -.- ..

The described 'measured value processing' :, refers to a line in the y-direction. If several lines are present, the said processing can take place line by line one after the other. If an arrangement according to FIG. 2'b is used in conjunction with an x, y matrix structure of the CCD array, then this processing mode can also take place for the 2 'direction. "·.

For practical application, processing in one direction is generally sufficient, if the lens assembly

7a - 7c and the associated receiver array is aligned under et äsgegenüber horizontal and vertical edges of objects.

The lens assembly should be designed to ensure a compact design and high measurement effects with the largest possible reduction scale. When choosing the smallest possible focal length of the pupil lenses, the lens diameter (f / d ratio) must be taken into consideration with regard to the imaging quality. A small distance (dg , in FIG. 1) counteracts the largest possible f / d ratio.

Pig '«- 4- displays. Aüsführungsbeispiel. for the optical arrangement in an SE camera,

In known manner, the measuring device is housed in the camera base, wherein the Meßstrahlengang on the partially transparent Xlappspiegel 14 with hinged Hilfsspie- gg'ih, 15 led wircL '

The optical components of the first image plane, the pupil plane 8 and the second image plane are combined to form a compact module IS. This can be manufactured and adjusted separately, so that the installation into the camera is greatly simplified »The individual designations are identical with Pis. · 1.

-O '

Compared with known arrangements, the solution according to the invention has the possibility of image reduction with two decisive advantages:

There is an increase in the illuminance on the Mehrfacharräy and thus an increase in the Hutζ-Stor Abs'tändes. '. ,

Furthermore, the use of a compact Anordnimg possible, whereby the disadvantage of a necessary second image plane is compensated again.

Furthermore, the adaptation of the partial receiver to the position determined by optical image division is eliminated. The photoelectrically defined field requires less Justieraufwand and detects the measuring surface fully only in accordance with the defects between the sub-receivers.

Claims (7)

, Claim for service · 1. Arrangement for focusing of photographic cameras, in which the brightness distribution of the .Autumn pupil of the entire system generated by focus-dependent Abschattwirkung is evaluated in a measuring plane • and the measured values for fully automatic or semi-automatic Bins division of the recording lens are used, characterized in that the measuring. e) in a second image plane (9) lies / that in the pupil plane (8) optical means (7) are provided for generating at least two identical images of a limited section of a first image plane (4) in the second image plane (9) and that the identical ¹ images of the second image plane (9) 15 / by means of a multiple array (10) are divided into at least ¹ , 2 sub-images, wherein from the brightness distribution of diametral pupil areas by comparison of the same image parts assigned, receiver 've-rschi edener' fields the amount signal 20 '· un'd ^ un-teriBih ^ within a field, the direction signal for the focus deviation is obtained. 2, arrangement for focusing according to item 1, characterized in that in the pupil plane (8) in dia -... metralen peripheral pupil parts in a first ^: and / or a second direction perpendicular thereto at least two pupils! are arranged in the en (7a, 7 "b). Arrangement for focusing according to point 2, characterized in that the pupil lenses (7a, 7b) are arranged only in one direction, this direction preferably being inclined with respect to horizontal or vertical object edges by an angle c0 . 4. Arrangement for focusing according to item 3, characterized in that in the central part of the pupil plane (8) a lens (7 c) is arranged, whose optical axis coincides with the optical system axis. Arrangement for focusing according to point 4, characterized in that the focal length of the pupil lenses (7) is dimensioned such that comminution takes place in the second image plane with respect to the first image plane. · 6 arrangement for focusing with a signal processing part according to item 1, characterized in that (m-1) corresponding first differences of assigned receivers of two images A and 3 of diametrical parts of the pupil I ₁ ,, ¹ = \ An - Bn> _ _Λ . / _Λ % and (m-1) second diffe-IXi ι j η - <ι * «« vm * ~ \ j each one of the two images corresponds to M ^ "= SAn + 1 - An 1 ^. / ^ or ι = ι »·« ^ m- ι; ^M 2n ⁼ | ^B n ₊ 1 * ³ n \ η = 1 ... (m-1) S Sign of l / L and M ^ _1n , where the sign of the pole derivative for each of the (m-1) focus signals, from the coincidence or non-coincidence of the laws of M. and M ₂₁₁ , is apparent. 7. Arrangement for focusing on point β, characterized marked by the fact that the signal Mp _{n is} derived from a central image C, which is not involved in the formation of the signal M-,. 8th'. Arrangement for focusing according to point β, characterized in that multiplied by the signals IvL and M _2n for sign acquisition or "whose- Vorseichen are tested by means of a logic circuit. 9. arrangement for focusing according to item 6, characterized in that m-1 focus signals at least one signal directly or at least two signals are summed processed. 10. Arrangement for focusing according to point T, characterized in that image-limiting means, for. Third
a field stop (4a). are arranged in the first image plane. 1.1. Arrangement for focusing according to item 1, characterized in that between the images in the second image plane Abschinnbienden (11a, Hb) are provided. 12. Arrangement for focusing according to item 1, characterized in that arranged in the first image plane and the subsequent planes optical components and the Yielfacharray to a compact
Block (16) are summarized. (See 3 pages drawings)