JPS5994720A - Focusing detector - Google Patents

Abstract

PURPOSE:To obtain superior focusing detection precision by causing the principal light beam of luminous flux which has asymmetry of rotation to strike mutually corresponding parts of a couple of photodetecting element arrays. CONSTITUTION:A couple of photodetecting element arrays 4' and 5' are formed so that the length perpendicular to the array direction of photodetection surfaces of individual photodetecting elements which constitute the arrays respectively is l, where no influence upon the output distribution of respective photodetecting element arrays is exerted substantially even when images 14 and 15 projected on the photodetecting element arrays 4' and 5' shift in positions by distance (x) in the opposite directions. Therefore, the pitch interval of the photodetecting element arrays 4' and 5' may be equal to reference distance L, so that a focusing position is detected precisely not only when pieces of luminous flux incident to the photodetecting element arrays 4' and 5' are rotationally asymmetrical, but also when they are rotationally symmetrical.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a focus detection device using a blur image detection method used in optical devices such as still cameras, cine cameras, video cameras, microscopes, etc., and particularly to a light receiving device for focus detection thereof. FIG. 1 is a diagram showing the basic structure of an optical system of a focus detection device using a blurred image detection method. The image projected by the imaging lens 1 is divided into two parts by the half mirror 2 and formed on the predetermined state plane N8.3'. A pair of light receiving element rows 4.5 are arranged in front of the predetermined focal plane 3 and behind the other predetermined focal plane 8', separated by a distance NId. Therefore, if the projected image by the imaging lens 1 is formed on the predetermined focal plane 3.8', the projected image on each light-receiving element row 4.5 becomes an image of the same root once, so each of those light-receiving elements From each output in column 4.5, an appropriate evaluation function representing the amount of blur is calculated separately, and by comparing the results, it is possible to determine the in-focus and defocus directions.

However, for some reason, for example, as shown in FIG. 2, which schematically shows an example of a configuration applied to a single-lens reflex camera, a part of the luminous flux of the single lens 1 is transferred to a pair of light receiving element arrays 4. .5, the quick return baller 6 is placed behind the quick return baller 6.
A part of the light beam 8 is reflected on the sub-mirror 7 fixedly inserted in the
In the case of a fragment, the light beam incident on the light-receiving element array 4.5 has non-rotation symmetry. In the same figure, 1° is a film surface placed on the predetermined focal plane of the imaging lens 1, and 11 is a film surface that directs the light beam from the sub-glare 7 to each light receiving element array 4.
This is a beam splitting optical system for dividing and guiding the light beam into 5 light beams, and an intermediate position in the optical path between each of the light receiving element arrays 4.5 coincides with a position that is optically conjugate with the film surface 1o. Further, 12 is a finder optical system provided so that the projected image of the imaging lens 1 guided by the quick return mirror 6 can be observed.

In other words, the principle diagram is shown in FIG.

A part of the light beam from the object 13 is blocked by the imaging lens 1 by the shielding object 7' such as the mirror 7, so that the light beam from the imaging lens 1 becomes non-rotationally symmetrical.
The principal ray 9 of the luminous flux is inclined by an angle θ with respect to the principal ray O when the luminous flux is rotationally symmetric. Therefore, there is a distance Md before and after the expected focal plane 8, which is the focusing position of the imaging lens l.
Each blurred image on the plane separated by 14.15 is shifted by a distance
= 2dtanθ - (1).

Therefore, as shown in FIG. 2, such a rotationally non-symmetrical light beam is transmitted to each light receiving element array 4.
5, as shown in an enlarged view of the beam splitting means 11 in FIG. For the light-receiving element row 4.5 formed in the light-receiving element row 4.5, the principal ray 9 of the light beam incident on the light-receiving element row 4.5 would be is tilted as explained earlier, resulting in a shift of 7"1. in the optical image on each light-receiving element row 4.5. FIG. 5 shows the state of the shift. When the light flux incident on the light receiving element array 4.5 is incident on the shield 7' without being interrupted, the corresponding and identical parts of each light receiving element row 4.5 on which the principal ray of the light flux enters are designated as A and B as shown in the figure. Then, when the light beam incident on the light receiving element array 4.5 is eclipsed by the shield 7' (see Fig. 8), the incident position of the chief ray is shifted from the positions A and B. , A' and B shifted by distance X in opposite directions
It will move to position l. For this purpose, each light receiving element row 4
The output distribution of the workpiece 5 does not have the same shape, for example,
Figure 6 shows the sharpness of each n image obtained from each output of each light-receiving element row 4.5, assuming that the subject has a residual distribution in the direction perpendicular to the row direction of the light-receiving element row 4.5. As shown in the evaluation functions Fl and F2 representing degrees, the evaluation values F differ by Δ.

In the focus detection device using the image detection method, the values of the respective evaluation functions F0 and F2 are compared, and when the values are equal, the imaging lens 1 detects the optical Since the detection is performed assuming that the object is in focus at the intermediate position, it is clear that if the evaluation functions F□ and □F2 differ by Δ as described above, the heating detection accuracy will decrease.

In particular, in the case of a -eye flex camera station, a sub-mirror 7 is usually provided at the back of the quick return 6 to guide the focus detection light beam to the light receiving element array 4.5, as shown in FIG. It is necessary to make the sub-mirror 7 sufficiently small so that when the quick-return mirror 6 rotates in the direction of the arrow and flips up, the light beam incident on the film surface 10 is not interrupted. On the other hand, in order to obtain sufficient focus detection sensitivity, the reflective surface of the sub-mirror 7 needs to have a wide area. In order to satisfy the former requirement and also satisfy the latter requirement to some extent, a sub-mirror 7 having a fairly large reflective surface is used, so that when the quick return mirror 6 flips up, the end of the sub-mirror 7 In order to prevent the light flux incident on the film surface IO from being continuous, the quick return mirror 6 must be mounted offset from the optical axis.In this case, the phenomenon explained in FIG. 8 will occur, This causes a decrease in focus detection accuracy.

An object of the present invention is to provide a focus detection device using a lateral shift detection method with high focus detection sensitivity without being affected by image shift due to the non-rotational symmetry of the light beam incident on the focus detection light receiving element array as described above. This is what I am trying to do.

The focus detection device of the present invention is arranged to sandwich a focusing surface of an imaging lens or a surface that is optically conjugate to the focusing point, and project images onto a pair of light receiving element arrays arranged at positions equidistant from the focusing surface. In a focus detection device that detects an imaging state at the focusing plane of the imaging lens by comparing the sharpness of images, the focus detection device detects the imaging state at the focusing plane of the imaging lens, which is caused by the non-unifold symmetry of the light beam used for detecting the imaging state. The principal rays of the beams having non-rotation symmetry are incident on substantially corresponding portions of the pair of light-receiving element arrays, so that the projected images of the respective pairs of light-receiving elements j, This feature is characterized in that compensation is achieved by configuring as follows.

Hereinafter, the present invention will be described in detail based on examples.

The basic configuration of the apparatus of the present invention is as described with reference to FIGS. 1, 2, and 8. The device of the present invention is characterized by its light receiving device in its basic configuration.

FIG. 7 shows an embodiment in which one of a pair of light-receiving element arrays of the light-receiving device according to the present invention is shifted by 2X in the direction of the arrow. That is, when the chief ray of the light beam guided to the light receiving element array 4.5 has rotational symmetry, if the position AJ is incident on one of the light receiving element arrays 4, the light flux is non-1.
When rotational symmetry is achieved, at a position A" shifted in the direction of the arrow by the shifted view 2X between the projected images on each light-receiving confectionery 4,b that shifts,
A pair of light-receiving element rows 4.5 is used in which the light-receiving element row 4 is arranged, and the other light-receiving element row 5 is arranged in the same position.

The light-receiving element array 4.5 formed in this manner is arranged to face the beam splitting optical system 11 as shown in FIG. If the principal ray M9'k of the optical flux is incident on a predetermined portion A'' of one of the light-receiving element arrays shown, for example, 4 in FIG. distance L
(When the incident principal ray is rotationally symmetric, the distance between the corresponding positions A and B of the light receiving element array 4.5 where the principal ray is incident.) Furthermore, the predetermined portion A# at the 2Xfnfc position The light will be incident on a predetermined portion B of the other corresponding light receiving element array 5. Therefore, the same portion of the image from the imaging lens l projected onto each of the nine light-receiving element rows 4.5 is photoelectrically converted by each of the nine light-receiving element rows 4.5. As shown in Fig. 8, the evaluation functions F□ and F2 regarding the sharpness of the image determined as the photoelectric conversion output are the same when the images on each light-receiving element array 4.5 have the same sharpness. Therefore, even if the light beam incident on the light-receiving element array 4.5 has non-rotation symmetry, the focus detection accuracy does not deteriorate.

In the above embodiment, one of the pair of light-receiving element rows 4.5 is shifted so that the arrangement is relatively expanded by 2X, but the interval between each light-receiving element row 4.5 is changed from the reference interval. Of course, each light-receiving element array may be shifted outward by X in order to further expand the distance by 2X.

Further, the spacing between the pair of light receiving element rows 4.5 is the same as the conventional one, using the standard spacing as described above, and each light receiving element row 4.
-16 or mirror 1 of the beam splitting means, for example indicated by 11 in FIG.
By appropriately setting the reflection angle of the reflecting surface 7 or the reflecting surfaces 16.17, the chief ray of the light beam incident on each light receiving element row 4.5 can be The light may be applied to mutually corresponding parts of the rows 4 and 5, and such an embodiment is also included in the apparatus of the present invention.0 Figure 9 shows another embodiment of the present invention. The configuration of the light receiving element array 4.5 is shown.

In this embodiment, each pair of light receiving element rows 4', 5
The length in the direction perpendicular to the column direction of the light-receiving surfaces of the individual light-receiving elements constituting each of the light-receiving element rows 4' and 5'
The length t is such that even if the images 14 and 15 projected on the images 14 and 15 are shifted by a distance X in opposite directions, the output distribution of each light-receiving element array is not substantially affected. Therefore, in this embodiment, the pitch interval of each light receiving element row 4', 5' may be equal to the reference distance as in the previous embodiment, and each light receiving element row 4. This has the advantage that the in-focus position can be detected with high accuracy not only when the light beam incident on the rays 1 and 5/ is rotationally symmetrical, but also when it has rotational symmetry.

That is, since the width t in the direction perpendicular to the column direction of each light-receiving element row i, /, 5/ is sufficiently wide, each light-receiving element row Φ' is incident when the chief ray of the incident light beam is rotationally symmetrical.

If for some reason, for example, as shown in Fig. 10, the incident position of the principal ray of the incident light beam shifts to A' and B', respectively, from the corresponding positions A and B on 5'. However, as is clear from the explanatory diagram shown in FIG. 10 using the same method as in FIG. is sufficiently wide, the change in the output distribution of the photodetector arrays 4' and 5' is as follows.
This can be virtually ignored. Therefore, each light receiving element row 4'
The evaluation functions F□, Fg regarding the sharpness of the fc image obtained from the outputs of F is #
Since the hills are equal, the heating state can be detected with high accuracy regardless of the nature of the light beam incident on the light receiving element arrays +, /, and 5/.

As is clear from the above description, according to the apparatus of the present invention, the influence on the evaluation value representing the sharpness of an image due to the non-rotational symmetry of the focus detection light beam can be compensated for with a relatively simple configuration. Therefore, it is possible to provide a focus detection device with excellent focus detection accuracy for an optical device in which the focus detection light beam has non-rotation symmetry.

Further, according to the embodiment shown in FIG. 9, it is possible to provide a focus detection device using a blurred image method that always achieves a high focus of 8 degrees regardless of the nature of the light beam for focus detection. effective.

[Brief explanation of drawings]

Figure m1 is a basic configuration diagram of the optical system of a focus detection device using a blurred image detection method, Figure 2 is a schematic configuration diagram of case 7 in which the focus detection device is applied to a single-lens reflex camera, and Figure 3 The figure is an explanatory diagram of the phenomenon of generation of non-rotationally symmetrical light beams, FIG. 4 is an enlarged view of the configuration of the light receiving device portion consisting of the light beam splitting means and the light receiving element array in FIG. 2, and FIG. 5 is the light receiving device in the conventional device. FIG. 6 is an explanatory diagram of the relationship between the arrangement of the element rows and the incident light image. FIG. 6 is an explanatory diagram of the drawbacks of the conventional device. FIG. 8 is an evaluation function curve diagram for explaining the effectiveness of the device of the present invention. FIG. 9 is a configuration diagram of a light-receiving element array in another embodiment of the present invention. FIG. 9 is an explanatory diagram of the operation in the embodiment of FIG. 9; l...Imaging lens, 2...Half ε sea, 3.8'
... Pre-focus plane, 4.5... Light receiving element array, 6...
Quick return mirror, 7... Sub-baler, 7'.
. . . Shielding object, 8 . 2. Object: 14.15...Blurred image, 16...Light receiving element array forming substrate, 17...Half baller, 18...Mirror. Figure 1 Figure 2 Figure 8 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] L Projected onto a pair of light-receiving element arrays placed equidistantly from the focusing surface of the imaging lens or a surface optically conjugate to the focusing surface. In a focus detection device that detects the imaging state at the focusing plane of the imaging lens by comparing the sharpness of images, the sharpness of the image is The projected images 7-'L of the light-receiving confectionery pairs are arranged so that the chief rays of the light beams having non-rotation symmetry are incident on substantially corresponding portions of the pair of light-receiving element arrays. A focus detection device characterized in that it compensates by configuring. The reflection angle of the reflecting surface in the beam splitting means for making the principal ray of the light beam having non-rotationally non-rotation symmetry enter the pair of light receiving element rows or dividing the principal ray into each light receiving element row. Claim g! characterized in that by appropriately setting the light, the light is incident on the same portion of the corresponding light receiving element array. The focus detection device 0 according to item A1 & the pair of light receiving element rows have a sufficiently long dimension in the direction orthogonal to the row direction? By configuring the light-receiving confectionery with a light-receiving confectionery having a plurality of light-receiving elements, an output equivalent to the principal ray of the non-rotationally symmetric light beam incident on a corresponding portion of each light-receiving element row of the pair can be obtained from each light-receiving element row. A focus detection device according to claim 1, characterized in that: