JPH02253222A - Focus detector - Google Patents

Abstract

PURPOSE:To easily enlarge a range-finding visual field by shifting and arranging two lenses of a secondary optical system in specified directions respectively. CONSTITUTION:The aperture parts 6-1 and 6-2 of a diaphragm 6 are provided in parallel with the longitudinal direction of a photodetector trains 5-1 and 5-2. Meanwhile, two lenses 4-1 and 4-2 of the secondary optical system 4 are arranged by shifting the apexes of the lens surfaces oppositely to each other with respect to the centers of the aperture parts 6-1 and 6-2. Then, the aperture part images 2a1 and 2a2 of the aperture part 2a of a visual field mask 2 are formed on the surface of the photodetector means 5 by shifting oppositely to each other in a direction perpendicular to the arranging direction of the aperture parts 6-1 and 6-2 of the diaphragm 6. Thus, the size in the longitudinal direction of the aperture part 2a of the visual field mask 2 is large and the range-finding visual field is enlarged.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a focus detection device suitable for photographic cameras, video cameras, etc., and particularly to a focus detection device that divides the field of an objective lens into a plurality of regions and passes through each region. The present invention relates to a focus detection device that detects the in-focus state of an objective lens by forming light intensity distributions regarding a plurality of subject images using a light flux and determining the relative positional relationship of these plurality of light intensity distributions.

(Prior Art) Conventionally, there is a so-called image shift method as a light-receiving focus detection method that utilizes a light beam passing through an objective lens.

This image shift method has been proposed, for example, in Japanese Patent Laid-Open No. 59-107311 and Japanese Patent Laid-Open No. 59-107313.

FIG. 9 is a schematic diagram of an optical system of a focus detection device using a conventional image shift method.

In the figure, 61 is an objective lens, and 62 is a field mask, which has an opening 62a and is disposed near the intended imaging plane of the objective lens 61. Reference numeral 63 denotes a field lens, which is arranged near the intended image plane. A secondary optical system 64 is composed of two lenses 64-1 and 64-2 arranged symmetrically with respect to the optical axis of the objective lens 61. 65 is a light receiving means, and the two lenses 64-1.
It has two light-receiving element rows 65-1 and 65-2 arranged behind it in correspondence with 64-2. A diaphragm 66 has two openings 66-1.66-2 arranged in front of the two lenses 64-1.64-2. Reference numeral 67 denotes an exit pupil of the objective lens 61, which is composed of two divided regions 67-1 and 67-2.

Note that the field lens 63 has an opening 66-1.66-
2 onto areas 67-1 and 67-2 of the exit pupil 67, and the light beams transmitted through each area 67-1. The light y1 distribution between the images of people and subjects is formed.

In the focus detection device shown in FIG. 9, when the imaging point of the objective lens 61 is in front of the intended imaging plane, object images are formed on the two light-receiving element rows 65-1 and 65-2, respectively. When the light intensity distributions of the objective lens 61 become close to each other and the image forming point of the objective lens 61 is located behind the planned image forming plane,
The light quantity distributions formed on the two light receiving element rows 65-1 and 65-2 are separated from each other. At this time, the position of shift in the light intensity distribution formed on the two light receiving element arrays 65-1 and 65-2 has a certain functional relationship with the out-of-focus state of the objective lens 61, so the amount of shift can be calculated using an appropriate calculation means. The direction and degree of defocus of the objective lens 61 are detected.

The focus detection device shown in FIG. 9 performs distance measurement on a subject whose size corresponds to the opening 62a of the field mask 62, which is present approximately in the middle of the subject range photographed by the objective lens.

(Problems to be Solved by the Invention) Generally, in the focus detection device shown in FIG. It is set. At that time, the size of the light receiving element row 65-1.65-2 in the longitudinal direction of the light receiving element row 65-1.65-2 of the opening 62a is
It is set in accordance with the size of the aperture image projected onto the surface. Thereby, the light receiving element array detects the light amount distribution of the subject image corresponding to the aperture image.

However, in such a configuration, if the longitudinal dimension of the aperture 62a of the field mask 62 is increased in order to widen the distance measurement field of view, the aperture m images 62a1 and 62a2 of the aperture 62a on the light-receiving element row surface become as shown in FIG. As shown, there were cases where some parts overlapped.

For this reason, there was a limit to the expansion of the distance measurement field of view.

In addition, when performing so-called multi-point distance measurement in which distance measurement can be performed in multiple areas using a field mask having a plurality of openings in the focus detection device shown in FIG. 9, the target light receiving element Unwanted light that has passed through other openings enters the column,
There was a problem that focus detection accuracy was reduced.

The present invention makes it possible to easily expand the depth of the distance measurement field on the intended image forming plane in a so-called image shift type focus detection device, and even when a plurality of distance measurement fields are provided, It is an object of the present invention to provide a focus detection device capable of highly accurate focus detection without causing aperture images in a distance measurement field to overlap each other and without unnecessary light entering a light receiving element array.

(Means for Solving the Problems) The focus detection device of the present invention uses a secondary optical system disposed on the image plane side of an objective lens to generate a plurality of images related to a subject image using a light flux that has passed through different regions of the pupil of the objective lens. A light intensity distribution is formed, the relative positional relationship of the plurality of light intensity distributions is determined by a light receiving means having a light receiving element array made up of a plurality of elements, and an output signal from the light receiving means is used to focus the objective lens. When determining the state, a diaphragm having at least one pair of apertures parallel to the direction in which the elements of the light receiving element row are arranged is provided near the secondary optical system; The lens has at least one lens, and the apexes of the lens surfaces of the pair of lenses are arranged in opposite directions perpendicular to the arrangement direction of the elements of the light-receiving element row with respect to the aperture center of the diaphragm. It is characterized by being shifted by a predetermined amount.

(Embodiment) FIG. 1 is a schematic diagram of a main part of a first embodiment of the present invention, and FIG. 2 is an explanatory diagram of a portion of FIG. 1.

In the figure, 1 is an objective lens, 2 is a field mask,
It has an aperture 2a corresponding to the distance measurement field of view, and is arranged near the intended imaging plane of the objective lens l. Reference numeral 3 denotes a field lens, which is arranged near the intended image plane.

Reference numeral 6 denotes a diaphragm, which has two openings 6-1 and 6-2 provided symmetrically with respect to the optical axis of the objective lens l.

4 is a secondary optical system (secondary imaging lens), which has two lenses 4-1 and 4-2.

The apex of the lens surface of the lens 4-1.4-2 is located at a distance of 8-1.
6-2 arrangement direction (light receiving element r row 5-1, 5-2 to be described later)
They are arranged at a predetermined distance from each other in a direction perpendicular to the longitudinal direction of

5 is a light receiving means, and two light receiving element arrays 5-1 are arranged behind the two lenses 4-1 and 4-2.
．． 5-2. The light receiving element rows 5-1, 5-2 are arranged so as to correspond to the lenses 4-1, 4-2 and are shifted in opposite directions.

7 is the exit pupil of the objective lens 1, and the two divided f
It is composed of t4kd7-r and 7-2.

Note that the field lens 3 has the function of focusing the aperture 6-1°6-2 on the area 7-1.7-2 of the exit +17, and the light transmitted through the 6th area fd7-1.7-2 The light beams form a light amount distribution related to the subject image on the light receiving element arrays 5-1 and 5-2, respectively.

In this embodiment, the method of detecting the focus of the objective lens l is substantially the same as that of the conventional example shown in FIG.

In this embodiment, the aperture 6-1.8-2 of the diaphragm 6 is provided parallel to the longitudinal direction of the light-receiving element array 5-1.5-2. 1.4-2 are arranged so that the apexes of their lens surfaces are shifted in opposite directions relative to the center of the opening 6-1, 6-2, as described above.

As shown in FIG. 2, the aperture images 2a1 and 2a2 of the aperture 2a of the field mask 2 on the surface of the light receiving means 5 are mutually perpendicular to the direction in which the apertures 6-1, 8-2 of the diaphragm 6 are arranged. Opening images 2al, 2a2 when the longitudinal dimension of the opening 2a is changed by shifting in the opposite direction and forming an image
are arranged so that they do not overlap each other on the surface of the light receiving means 5.

As a result, the longitudinal dimension of the opening 2a of the field mask 2 is increased to enable distance measurement with an enlarged distance measurement field of view.

FIG. 3 is a schematic diagram for explaining the optical path of the light beam that passes through the secondary optical system and the diaphragm and is guided onto the light receiving means surface.

In the figure, o and o' are object points, i and i' are image points conjugate to the object point 0.0, respectively, 32 is a diaphragm that is symmetrical about the optical axis, and 33 is the vertex of the lens surface by the distance from the optical axis. The lens 35, which has a convex power and has shifted, is an imaging plane for object point 0 and corresponds to the sensor plane. The lens 33 is placed immediately after the calibration 32.

Aperture 32. The lens 33 and sensor 35 are the aperture 6, lens 4-1 (4-2), and light receiving element array 5 shown in FIG.
-1 (corresponding to 5-2>).

From the same figure, the distance from the optical axis of image point i is h (a+b)/
a, that of image point i'' is h(a' + b'')/a', and the slopes of the chief ray to image point i and the principal ray to image point i'' are h (a+b)/ab, h( a'+b')/a
'b', which is l/.

+ l/b = l/a' + I/b
' Tae J! 14 ;: Equivalent to to'j L . In other words, even if the apex position of the lens surface of the lens 33 is shifted upward, the image at the sensor 35 will not shift downward due to defocus.

FIG. 4 is an explanatory diagram showing the convergence state of the light beam when viewed from above the surface of the sensor 35 at this time.

In the figure, points P and ~P4 indicate light rays that are assumed to have passed through the apex of the lens surface that shifts due to defocusing of the objective lens, and the blur state of the light flux gradually increases but does not shift upward or downward. It represents.

FIG. 5 is a schematic diagram of main parts of a second embodiment of the present invention.

In this embodiment, the field mask 2 has four openings 2a, 2b, 2.
c, 2d H1l1 openings 2a and 2b partially overlap. ) indicates the case where so-called multi-point distance measurement is being performed.

The calibration 6 has four openings 6a to 6d corresponding to the four entrances 28 to 2d, and the secondary optical system 4 has four lenses 48.
4d, and the light receiving means is also configured to have four pairs of light receiving element rows, as will be described later.

Note that the focus detection of the objective lens is performed for each region by a method similar to the focus detection method described above.

In this embodiment, the two lenses 4c and 4d of the secondary optical system are arranged such that their lens surface vertices are shifted by a predetermined amount from each other in a direction perpendicular to the direction in which the openings 28 to 2d of the field mask 2 are arranged.

At this time, the other two lenses 4a and 4b are arranged with or without being shifted in the direction in which the openings 2a to 2d are arranged, depending on the purpose. The figure shows a case where no shift is performed.

By arranging each element in this manner, it is possible to prevent unnecessary light from entering the light receiving element array from the distance measurement field, which would otherwise have an adverse effect, when a plurality of distance measurement fields are provided.

FIG. 6 is an explanatory diagram showing the state of the aperture image of the field mask 2 on the surface of the light receiving means 5 at this time.

The figure shows a state in which, for example, unnecessary light related to the aperture image 2cl of the aperture 2c of the field mask 2 does not enter the light receiving element array 5c3 and is separated.

In addition, when the two lenses 4a and 4b are shifted relative to each other in FIG. 5, the light receiving element arrays 5cl and 5c shown in FIG.
2.5R1, 5R2, 5L1°5L2 must be shifted in opposite directions and arranged.

Figures 7 and 8 are 5. As in the embodiment shown in FIG.
FIG. 4 is a schematic diagram of main parts showing a situation when the two lenses 4C14d are not shifted relative to each other as described above.

As shown in FIG.
(2b), a field mask 2 is formed on the aperture image 2al by the light beam incident on the surface of the light receiving means 5 through the aperture 6c of the diaphragm 6.
The aperture images 2cl of the field mask 2 formed by unnecessary light passing through the aperture 6d of the diaphragm 6 from the other aperture 2c overlap.

Figure 8 shows the state on the surface of the light receiving means 5 at this time.
It is an explanatory diagram shown similarly to a figure.

In the figure, the apertures 28 to 2d of the field mask 2 are projected onto the light receiving means 5 by the four lenses 4a to 4d. This corresponds to that which has passed through 6d.

As shown in the figure, the light beams incident on the light receiving element rows 5c3, 5c4 are mixed with the light beams from the peripheral apertures 2C in addition to the light beams originally from the central aperture 2a. As a result, when focus is detected using the light-receiving element rows 5c3, 5c4, unnecessary light is mixed in the light amount distribution of the subject image, which causes erroneous distance measurement and a decrease in focus detection accuracy.

On the other hand, according to the present invention, by setting each element as described above, these problems are solved and highly accurate focus detection is made possible.

(Effects of the Invention) According to the present invention, in a focus detection device using an image shift method, the size of the distance measurement field can be adjusted by arranging the two lenses of the secondary optical system shifted in a predetermined direction relative to each other as described above. To achieve a focus detection device that can easily enlarge the field of view, and that enables highly accurate focus detection without unnecessary light entering the target light receiving element array even when a plurality of distance measuring fields are provided. be able to.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the main part of the first embodiment of the present invention, FIGS. 2 and 3 are explanatory diagrams of a part of FIG. 1, and FIG. 5 is a schematic view of the main part of the second embodiment of the present invention, FIG. 6 is an explanatory diagram of the surface of the light receiving means in FIG. 5, and FIGS. FIGS. 9 and 10, which are schematic diagrams for detailed explanation, are schematic diagrams of main parts of a conventional focus detection device. In the figure, 1, 61 is an objective lens, 2, 62 is a field mask,
28 to 2d, 62a are apertures, 3 and 63 are field lenses, 4.64 is a secondary optical system, 5.65 is a light receiving means, 6
．． 66 is the aperture, 4-114-2.64-1.64-2.
4a ~ 4d lenses, 6-1.6-2.66-1,8
6-2.6a to 6d are openings, 7 is pupils, 5-1.5-2
．． 65-1.65-2 is a light receiving element array.

Claims (2)

[Claims] (1) A secondary optical system placed on the image plane side of the objective lens uses the light beams that have passed through different areas of the pupil of the objective lens to form multiple light intensity distributions regarding the subject image, and the relative When determining the positional relationship of the objective lens by a light receiving means having a light receiving element row made up of a plurality of elements and using the output signal from the light receiving means to determine the in-focus state of the objective lens, there is a A diaphragm having at least one pair of apertures is provided parallel to the direction in which the elements of the light receiving element array are arranged, and the secondary optical system includes at least one pair of lenses.
The pair of lenses are arranged such that their lens surface vertices are shifted by a predetermined amount in opposite directions from the center of the aperture of the diaphragm in a direction perpendicular to the arrangement direction of the elements of the light-receiving element array. A focus detection device characterized by: (2) The focus detection device according to claim 1, wherein the pair of light-receiving element rows are arranged so as to be shifted by a predetermined amount in opposite directions to each other in a direction perpendicular to the direction in which the elements are arranged.