JPS58178328A - Focus detector - Google Patents

Abstract

PURPOSE:To filter space frequency components of higher order and to detect a focus exactly, by detecting the focus with the blurred images on photoelectric transducers. CONSTITUTION:If the plane existing at a distance X forward from a focus detecting plane D is considered and X is increased gradually from 0, the images by the reimaging lenses 261, 263 of two sets of photoelectric transducers A1(211)- A6(216), B1(221)-B(226) on the plane X are blurred gradually increasingly and deviate from each other. When the X attains a certain value, the images of A1 and B2-A5 and B6 overlap on each other. If the X is increased further, the overlaps deviate by each other. The images on the transducers A1-A6, B1-B6 in this stage are blurred but the outputs of the A1 and the B3 are equal, and the respective outputs of the A2 and B4, the A3 and B4 and the A4 and B6 are equal as well. If the equality in these paired outputs is detected, the focusing is detected. The focus is detected exactly by selecting the X so as to decrease >=fN components without decreasing the <=fN/2 space frequency components of the blurred images too much.

Description

[Detailed Description of the Invention] The present invention relates to T T L (throt+gh th@L@
ns) type focus detection device.

A TTL type focus detection device was developed by the present applicant in 1972.
The appearance of both types of optical systems disclosed in US Pat. No. 4,185.191 by another applicant is completely different. However, the essential effects are the same. In other words, each of the two beams of light passing through different exit pupil portions of the photographic lens is separated from the other on the detection surface of the focus detection device to form a plurality of photoelectric conversion elements Als..., ANS Bls.
..., it has a structure that leads to BNK. The output turns from these photoelectric conversion elements AI, ..., AN are P
The output patterns from the photoelectric conversion elements Bl, . However, these optical devices have the drawback that they may give inappropriate results when the image contains certain high-order spatial frequency components (components above the Nyquist limit).

An object of the present invention is to provide an optical device that enables accurate focus detection by filtering out high-order spatial frequency components that cause errors by detecting a close match by focusing on the detector itself. It is.

First, regarding the optical image projected onto the detection surface of the focus detection device, 4I detection micro-areas D1%D1, . . . , D are arranged on the detection surface at intervals d.

The photoelectric output al,'l,... associated with the optical sound incident on
&N, and this photoelectric output alS &! , ..., the problem when discussing the shape and movement of the pattern of an optical image from the pattern created by my is that a lattice image of the space d with a spatial frequency f-1 is projected onto the 1st D, ..., DB. , when this spatial grating image is displaced little by little to the right, e(A') corresponds to the photoelectric output 'l, aI, . . . , 1. is shown in (A''). In this case, it can be seen that the light image is moving to the right, and the output pattern is also moving gradually to the right.

Figure 1 (B) shows the case where the spatial grating d image of the spatial frequency f-- is displaced to the right (B') and the corresponding changes in the photoelectric output &1, l mushroom, ..., aI (B'). !
′). In this case, even though the light gI#'' is moving to the right, the output pattern only changes the amplitude or changes the phase by 1800 degrees, corresponding to my minute movement, resulting in a smooth change in the phase of the running cover turn. It is not allowed.

When I is displaced to the right (σ) and the corresponding change in photoelectric output '1.11,..., Hatake 1 (c'')
This is what is shown. In this case, even though the light image is moving to the right, it can be seen that the exit pattern is moving in the opposite direction to the left.

Above this, the spatial frequency of the optical image is the Nyquist frequency f, F
In the case of (B), which corresponds to =i, or fN〈f < 2fJ
corresponds to
When there are many components corresponding to f and K, there will be a very large error in determining the movement of the optical image. Therefore, the photoelectric output cover turns Pu from the two sets of plurality of detection elements A1.1m, .
From the direction and magnitude of mutual displacement of s Pj, focusing,
In a focus detection device that determines front focus and rear focus, the presence of a spatial frequency component of f≧11 in an optical image causes malfunction. The present invention relates to an appropriate arrangement of the detection surface of a focus detection device that eliminates high-order spatial frequency components that cause these malfunctions by blurring.

FIG. 2 and FIG. 3 are equivalent to the optical system disclosed in Japanese Utility Model Application Publication No. 55-26516, and the conventional example will be explained first. In FIG. 2, a plurality of charging conversion elements A
I (211), A mushroom (212), As (213),
A4 (214), AI (215), AI (21B)
and the other plurality of photoelectric conversion elements B1 (221), B1
(222), Bs (223), Ha (224), B
, (225), Bs (22B) are the field lens 23G by the reconsolidation lenses 261 and 262, respectively.
Adjustments are made so that the respective conjugate images are aligned and positioned on a nearby surface in a substantially focused state. That is, the conjugate images of AI(211) and B+(221J are Dt(231), At(212) and th(222)
) is the conjugate image of Dt(232...As(216)
The conjugates of and B·(221i) are formed on os(236), respectively.

The surface where these mutually conjugate images overlap 9 is the detection surface of this conventional focus detection device, and is ib and D1 to D1 on the detection surface.
D6 form a "detection minute area" lined up at an interval d. Further, the field lens 230 is the re-imaging lens 261.26.
The aperture of No. 2 transmits its conjugate image to the exit pupil position 20G of the focusing lens (lens whose focus is detected) set in front at a distance t from the field lens, and the first part of the exit pupil (251) and the exit l1ik, respectively. Its curvature is determined to be formed as the second portion (252) of.

In the "focus detection method using a sharp lens" which is normally used in such a configuration, the arrangement is such that a matching signal is generated when the sharpest image plane of the focusing lens coincides with the focus detection plane DK. That is, in the focused state, the images on the plurality of photoelectric conversion elements A, ~A1, and 81~B- are in the clearest state.

) In this clear state, the spatial frequency component f≧f, I is not removed, which may cause the above-mentioned malfunction. Photoelectric conversion elements AI (211) and B
t (221), A Tomi (212) and Bl (222), As
Focusing can be detected by detecting that each pair of (213) and Bl (223), . . . As (216) and B. (226) has an equal output.

In the present invention, the blurred image surface coincides with the detection surface of the focus detection device to the extent that the spatial frequency component of f'&i is greatly reduced without significantly reducing the spatial frequency component of t < y/2. This is because it provides an arrangement that generates a focus signal when the lens is focused, that is, a ``focus detection method based on blurring''.

Next, the present invention will be explained in detail using FIG. In this example, the injection [120G, field lens 230, reconsolidation lens 261, 262, photoelectric conversion elements A, -A4,
The positional relationship of Bs to B- is the same as the nine conventional ones described above.

In FIG. 2, the focus detection plane, that is, the detection minute area Dt(2
Consider a surface located at a distance X in front of the surface where 3L) to D.(236) exist. Since the reconvergence lens forms a clear image of the photoelectric conversion elements A1~AI, Bl''-B- on the detection surface, as X is gradually increased from 0, the Two sets of charging conversion elements AJ-Ag
, 81~Bm by the re-imaging lens gradually become blurred and deviate from each other, and when X takes a certain value, the photoelectric conversion elements AI (211) and Bl (222) also become A (212). And Bs (223) is・”'As (2
15) and Bl (226) overlap. Further X
When increasing and reaching the +X position shown in FIG. 2, photoelectric conversion elements Al (211) and IIg (2
23) is 243, AI (212) and Bs
(224) is 244, ...An(21
4) and Bv(22B) overlap at 246, respectively. Here, when the angle from the detection 1iiD of the focus detection device to the center of the first and second portions of the exit pupil is θ as shown in the figure, and the interval between the detection minute areas on the detection surface is d, the upper To the extent that the elements of photoelectric conversion elements AI and Bj as described above overlap each other (albeit slightly blurred), ft is -1, 1, 2, 3
It is given by n-(1), and the priest is in the case of n-2 in Figure 2. Here, the centers of the first and second parts of the exit pupil are the points where the rays corresponding to the centers of gravity of the energy density distribution of the light fluxes that have passed through both parts intersect with the pupil plane. Therefore, if the partial shape is circular and the energy density distribution is uniform, this center will coincide with the center of this circle. In this device, conversely, when the sharpest image plane of the convergence lens (i.e., the photographing lens in a camera) comes to a position away from the detection plane by the amount X given by equation (1), the single focal point detection device For example, in the case of Fig. 2, the outputs of At and B are the same, As is 84%, AI is 81%, A4 and B The outputs of and are also equal to each other. Therefore, if it is detected that the output of each pair of and is rich, it is possible to detect the focus rather than the blur on the photoelectric conversion element. If the surface is provided, the surface shown in FIG. 2 will be at a position conjugate to the film surface, but in the embodiment explained using FIG. Of course n-...-3, -2, -1, 1, 2, 3.
If the configuration is such that the focus detection device performs focus determination at a position of
Since the respective outputs of ~A- and 81~B. do not correspond and do not match completely, the error in focus determination becomes large. In this way, the quantity X (where n−
...-3, -2, -111,2,3...) If the focus is determined when the sharpest image plane of the photographing lens is at a position away from the detection plane, the image will be blurred. Accurate focus detection can be performed without being adversely affected by high-order spatial frequency components. Furthermore, the most suitable magnitude of difficulty at X = nd/θ is determined as follows.

First, the timing of HmQ is to determine focus when the detection plane coincides with the clearest image plane of the photographing lens, and this corresponds to the conventional method described above. Now, from the detection side
Multiple photoelectric conversion elements AI-A@, B at positions separated by
As shown in Figure 2, the degree of blur for 1 to B6 is about b-ψ・X, assuming the angle from the detection surface to the partial pupil is 9. In other words, the degree of blur is approximately b−ψ・X, as shown in Figure 2. If the magnification is 1 km, the images on the plurality of photoelectric conversion elements A1 to A@, B1 to B- will be blurred to an extent of m-b. This blur is 'N/2
WCf x without reducing the following spatial frequency components
What is necessary is to select the value of KX, that is, the critical value, so as to greatly reduce the above spatial frequency components. Such conditions are approximately d
'(J<2d':d' = d
) / l.

Also, in order to accurately determine focus when the detection surface of the focus detection device does not match the sharpest image surface of the photographing lens, the blur on the multiple charging conversion elements is also A! ~A6 top and 81~Ba
371 and 372 as shown in Fig. 3, the corresponding light receiving surfaces of the photoelectric conversion elements A1 to Muro and Bl-%-IF must completely overlap each other. The value of X that matches will somewhat reduce the effectiveness of the present invention. Therefore, in the "focus detection method using bokeh gIK" as in the present invention, the shapes of the first and second parts of the exit pupil are moved in parallel along the line connecting the centers of the two parts (perpendicular to the optical axis of the photographing lens). It is preferable to set the shape so that the shapes of the two overlap each other. However, even in the case of Fig. 3, both the plurality of photoelectric conversion elements including the blur are of the schematic type.
That is, it is possible to find a position where the centers of gravity of both blurred images overlap, and in that case, the position may be placed at a position that satisfies the condition of KFs or equation (1). In this case, the angle θ in FIG. 3 is assumed to take a value given by the angle from the detection surface to the center of the 11th second portion of the emission plane.

The re-imaging lens on the plane of the light receiving elements 310 and 320 that is separated by X from the detection 1i1iD produces the following gR#'i. That is, the light-receiving element 31D13 is caused by a light ray passing through the center of the reconvergence lens (this coincides with the light ray passing through the centers of the first and second parts of the exit pupil described above).
20 (not shown, but the shape is exactly the same as 243 to 246 in FIG. 2) is shaped like a shape 371 and 372 similar to the shape of the re-imaging lens aperture.

In addition, in the examples shown in Fig. g2 and Fig. 3, the detection surface, that is, the surface where the bonds formed by the recombination lenses of the photoelectric conversion elements A, -A-, and B1 to B are clearly and overlapping with each other is the field lens surface. This shows a case where they roughly match, but the role of the field lens is to approximately project the reconsolidation lens aperture onto the exit pupil of the photographing lens, so even if the detection surface and the field lens surface do not necessarily match. good. That is, the field lens 230 is placed, for example, in front of the detection surface
It is also possible to bring it to the position of In that case, the photoelectric conversion elements A1 to A, 81 to B- at the position of X
d' is not affected by the power of the field lens, so its magnitude is slightly different from the value d' shown in Figure 2.
The value is simply determined by the consolidation magnification of the reconsolidation lens.

Next, a description will be given of an embodiment for performing exactly the same thing in the case of another optical system (US Pat. No. 4,185,191) with reference to FIGS. 4 and 5. In FIG. 4, there are microlens arrays 431 to 436 on the detection surface of the focus detection device, and these microlenses are lined up at an interval d on the detection surface. The aperture area Ds(4
31) to D, (43g) form a "detection minute area", and the "detection minute area DI(231) to as (
238) Corresponds to J.

The detection micro-regions D1-D in the case of FIG.
is determined by the shape of the apertures of the microlenses 431 to 436. In the device shown in FIG. 4, photoelectric conversion elements are arranged in pairs behind these microlens arrays, and Dl (4
31) AI (411) and Bt (421) are behind
However, behind Dt (432) there are As (412) and Bl (
422) is... placed. The optical system is arranged so that the conjugate images of these photoelectric conversion elements are superimposed on each other at the photographing lens exit position 400, which is a distance t in front of the detection surface, by means of microlenses corresponding to the shapes of the light receiving surfaces of these photoelectric conversion elements. That is, the amount of light incident on the microlenses 431 to 436 on the detection surface due to the light flux passing through the first portion 451 of the exit pupil is the same as the amount of light that has passed through the first portion 451 of the exit pupil.
3.414.415.416 and passes through the second portion 452 of the exit pupil, the microlenses 431~
The amount of light incident on each photoelectric conversion element 421.
422.42 to 3.424.425.426. In the focus detection optical system shown in Figs. 2 and 3, the shape of the first and second parts of the exit pupil was determined by the aperture shape of the reconstitution lens, but in Figs. In the focus detection optical system, the shapes of the first and second portions of the exit pupil are determined by the shape of the photoelectric conversion element. Although there is such a difference in correspondence, the photoelectric conversion elements AI and A
The appearance of the outputs of I, . . . , A6 and Bl, Bl, . That is, in FIG. 4 and a modified version of FIG. 5, the first and second exit parts 451.452 (or 551.552
) is the angle looking at the center (center of gravity) of ,-2,
-1°1.2.3...) Focus is determined when the surface of the photographic lens with the highest sharpness comes to a surface that is away from the detection surface by a distance of -1°1.2.3...). Of course, if the image with the highest clarity is placed on the detection surface by the photographing lens, it can be assumed that the image with the highest clarity will also be placed on the surfaces of the photoelectric conversion elements 411 to 416 and 421 to 426, but the detection surface When an image with the highest clarity appears on a plane separated by X from above, the images formed on the planes of photoelectric conversion elements 411 to 426 will be blurred as in the case of FIGS. 2 and 3. In the case of a conventional device in which a camera is equipped with this type of detection device, the surface shown in FIG. The plane that is X away from is conjugate to the film plane. In the embodiments of FIGS. 4 and 5, areas 443 to 446ib or 543 to
546, the overlapped image is detected by a photoelectric conversion element, accurate focus detection is performed from the blurred image on the photoelectric conversion element, and it is not affected by high-order spatial frequency components. Figure 4 t! Corresponding to the case of n-2, As (411) and Bs in the in-focus state (i.e., when the most vivid image appears on the plane that is X away from the detection plane).
The output of (423) is A嘗(412> and B, (42
4) The output of AI (413) and Bs (425) are equal, and the output of A4 (414) and Bs (426) are equal, respectively, and by detecting this, the detection plane and the highest sharpness are determined. Accurate focus detection is possible despite the distance X between the lens and the body surface.

The degree of blur in this case is determined by the spread of blur b = ψ, which is the spread angle of the pupil seen from the detection surface as shown in Figure 4.
It is given by ψ・X, and as in the case of Mongolia 2, VCa, b
~2d; d'-d*(t-X)/l It is preferable to select 9 degrees. Figure 5 shows a case where the shapes of the first exit 11 part and the second exit pupil part do not overlap due to mutual parallel movement (movement J in the direction perpendicular to the optical axis of the photographic lens, and in this case, the shapes of the first exit 11 part and the second exit pupil part do not overlap). Even if the condition of K(1) is satisfied as in the case, the photoelectric conversion elements A1 to A6 and 8 are
It is not guaranteed that the outputs of numbers 1 to B perfectly match, and the degree of focusing is somewhat degraded compared to the case where the shapes of the pupil portions overlap and match due to mutual parallel movement. However, even with such a device, the object of the present invention can be achieved.

So far, in each embodiment, we have described how to determine focus from the output of the photoelectric conversion element. Furthermore, when the photographic lens moves forward or backward from the in-focus state on the optical axis, I have not given much thought to what happens to the image on the photoelectric conversion element formed by the photographic lens when the photographic lens dies. However, A
The layers formed on the photoelectric conversion element surfaces of the series and the B series are moved on the photoelectric conversion element surfaces by the movement of the photographic lens in the optical axis direction, and are formed on the photoelectric conversion element surfaces of the A series. By detecting the relative position between the image formed and the image formed on the B-series element from the output of each photoelectric conversion element, the front focus and the rear focus can be detected as in the prior art.

As detailed above, the present invention performs focus detection in the vicinity of the in-focus area using the blurred image formed on the photoelectric conversion element, so there is a possibility that the focus may be incorrectly detected due to the influence of higher-order spatial frequency components. The drawbacks of conventional devices can be solved.

[Brief explanation of drawings]

Fig. 1 is a diagram for explaining the drawbacks of the conventional device, Fig. 2 is a perspective view of the first embodiment of the present invention, Fig. 3 is a perspective view of the second embodiment of the present invention, and Fig. 4 is a perspective view of the second embodiment of the present invention. FIG. 5 is a perspective view of the fourth embodiment of the present invention. [Explanation of symbols of main parts] 200:400:500...Exit pupil position of ossuary lens 251:451:551...Exit -
1st part 252:452:552...Second part D of exit pupil...Detection surface Applicant Nippon Kogaku Kogyo Co., Ltd. σ
2 (1B (Is 1 figure CC) Q (712Q3f144J (Btsu (C・) (..

Claims (1)

[Claims] 1. A plurality of detection micro-regions D1 arranged at intervals d on the detection surface out of the light flux that has passed through the first part of the exit pupil of the condensation lens;
A plurality of first photoelectric conversion elements AI, Am,... which receive optical energy incident on DI,..., DN, respectively.
, AN and the plurality of detection minute areas D1%DI% among the ninety-nine bundles passing through the second part of the exit pupil of the confluence lens.
・A second plurality of photoelectric conversion elements B1, Bl, .
ff and B1, . When the angle looking into the center of the part is θ, using this θ and the interval d between the arrangement of the micro regions, Xζ1
- Generate a focusing signal when the plane with the highest sharpness comes to the plane that is away from the detection plane by the amount given by d/'# (n-±1.±2...) Features a focus detection device. 2. When one of the first and second parts is moved parallel to a line connecting the centers of the first part and the second part, the shapes of the first part and the second part of the exit pupil are approximately the same as each other. 2. The focus detection device according to claim 1, wherein the first and second portions have shapes that overlap each other.