JPH01216307A - Focus detecting device having adjusting means - Google Patents

Abstract

PURPOSE:To detect a focus with high accuracy by providing an adjusting means having a prescribed optical action in front of a photodetecting means and adjusting a projecting state of a projected image of a visual field mask on the surface of the photodetecting means. CONSTITUTION:A photodetecting means 5 has two photodetector trains 5-1, 5-2 which correspond to two lenses 4-1, 4-2 and have been placed in the rear thereof. Also, an adjusting means 16 is placed between a secondary optical system 4 and the photodetecting means 5. In this state, by moving such an optical member 16 in the direction as indicated with an arrow 19, only a luminous flux transmitting through a member 18 can be deflected in the direction as indicated with the arrow 19 without exerting no influence on a luminous flux transmitting through a member 17. In such a way, a projected image of a visual field mask can be formed easily and with high accuracy in the arranged direction of the photodetector trains and the focus can be detected with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a focus detection device having adjustment means suitable for photographic cameras, video cameras, etc. An adjustment means suitable for detecting the in-focus state of an objective lens by forming a light amount distribution regarding a plurality of subject images using the light flux passing through each region, and determining the relative positional relationship of these multiple light amount distributions. The present invention relates to a focus detection device having:

(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.

Figure 25 shows focus detection using the conventional image shift method.

FIG. 2 is a schematic diagram of the optical system of the device.

In the figure, reference numeral 1 denotes an objective lens, and 2 denotes a field mask, which are arranged near the intended imaging plane of the objective lens 1. Reference numeral 3 denotes a field lens, which is arranged near the intended image plane. Reference numeral 4 denotes a secondary optical system, which is composed of two lenses 4-1 and 4-2 arranged symmetrically with respect to the optical axis of the objective lens 1. Reference numeral 5 denotes a light receiving means, which has two light receiving element rows 5-1.5-2 arranged behind the two lenses 4-1.4-2. Of course, two ranges of one light-receiving element array may be electrically specified. 6 is an aperture which connects the two lenses 4-1 and 4-2.
Two openings 6-1.
6-2. 7 is an exit pupil of the objective lens 1, which is composed of two divided regions 7-1 and 7-2.

Note that the field lens 3 has the function of focusing the aperture 6-1°6-2 on the region 7-1.7-2 of the exit pupil 7, and transmits light through each region 7-1.7-2. The resulting light beams form a light amount distribution on the light receiving element arrays 5-1 and 5-2, respectively.

In the focus detection device shown in FIG. 25, when the imaging point of the objective lens 1 is in front of the intended imaging plane, object images are formed on the two light-receiving element rows 5-1 and 5-2, respectively. When the light intensity distributions for the two light receiving element arrays 5-1 and 5-2 become close to each other, and when the imaging point of the objective lens 1 is located behind the intended imaging plane, the light receiving elements are formed on the two light receiving element rows 5-1 and 5-2, respectively. The light amount distributions become separated from each other. Moreover, since the amount of deviation in the light intensity distribution formed on the two light receiving element arrays 5-1 and 5-2 has a certain functional relationship with the amount of defocus of the objective lens 1,
By calculating the amount of deviation using a suitable calculation means, the direction and amount of the defocus of the objective lens 1 can be detected.

In such an automatic focus detection device, the two light-receiving element rows 5-1 and 5-2 are configured to detect the light intensity distribution at the same location of a subject (not shown), particularly in a direction orthogonal to the direction of the light-receiving element rows. It becomes important to do so. In other words, the secondary optical system 4 produces two light receiving element arrays 5-1.
It is necessary to configure so that the relative positional relationship between the two images of the opening of the field mask 2 projected onto the plane 5-2 is the same, especially in the direction orthogonal to the direction of the light receiving element array.

FIG. 18 is a diagram of the secondary optical system 4 of FIG. 25 viewed from the objective lens l side. For example, as shown in Fig. 18, the secondary optical system 4
rotates integrally around the optical axis of objective lens 1,
In the case of parallel movement, the projected image of the field mask 2 on the light receiving element array 5-1.5-2 by the secondary optical system 4 will be the same as the light receiving element array 5-1.8-2 in FIG. 19, for example. 5-1.5-
The arrangement relationship is shifted from 2. In this state, if a mountain-shaped object image 9 is formed near the field mask 2 by the objective lens 1 as shown in FIG. −
1.5-2 as shown at 10-1.10-2 in FIG. Each light receiving element row 5-1.5-2 at this time
As is clear from the figure, the outputs are different.

This is because when the focus state of the objective lens 1 is detected from the relative positional relationship of the light quantity distributions regarding the two object images, the accuracy of focus detection is significantly reduced. - When fishing on a boat and shooting a subject that has a light intensity distribution in the direction perpendicular to the direction of the photodetector array, if the projection of the field mask on the photodetector surface shifts due to an assembly error of the optical elements, etc., as shown in Figure 19, the focusing accuracy may be affected. It's going to decline.

In order to prevent a decrease in focusing accuracy at this time, for example, the light receiving means 5 may be rotated around the optical axis of the objective lens 1 or rotated in a plane perpendicular to the optical axis of the objective lens l. By moving in parallel, the positional relationship can be adjusted as shown in FIG. 21.

However, the accuracy required during this adjustment is generally very strict. Generally, the accuracy required when adjusting the position of the photodetector array in the direction perpendicular to the photodetector array direction depends on the day focus accuracy of the objective lens to be detected, the magnification of the secondary optical system, the pitch of the photodetector array, etc. However, when applied to an eye reflex camera or the like, it becomes approximately 1 μm or less. If this is converted to the adjustment rotation angle accuracy when the center spacing of the light-receiving element rows is 2 mm, it is approximately 3', which requires an extremely high-precision adjustment mechanism.

The above description has been made of a focus detection device in which the viewing direction, that is, the direction of the light-receiving element array is limited to one direction.

On the other hand, the present applicant has disclosed, for example, in Japanese Patent Application Laid-Open No. 62-95511, a focus detection device that can measure a distance even to a subject having a light intensity distribution only in a direction parallel to the light receiving element array.

In the same publication, for example, as shown in FIG. 22, in addition to lenses 4-1 and 4-2 as a secondary optical system, another pair of lenses 11 is
-1.11-2 are provided, and correspondingly, light receiving element rows 13-1 and 13-2 are newly arranged in the aperture 6 as well as in the aperture 12-1 and 12-2 and in the light receiving means 5. .

The opening of the field mask 2' is cross-shaped, and a projected image 14-1.14-2.15-1.15- of the opening of the field mask 2' is shown on the surface of the light receiving means 5 as shown in FIG. 2 is formed.

The principle of distance measurement is the same as that of the focus detection device shown in FIG.
The amount of defocus of the objective lens 1 is detected from the relative positional relationship of the light amount distribution with respect to the object image detected by 3-2.

With such a configuration, it is possible to measure the distance even for objects that have a light intensity distribution only in the vertical or horizontal direction of the distance measurement field of view. It is very difficult to ensure the same relative positional relationship between the field mask and the projected image of the field mask. That is, the position of the projected image of the field mask on the surface of the light receiving means is shifted due to eccentricity of the secondary optical system, etc., resulting in a positional relationship as shown in FIG. 24, for example. Then, for one of the two pairs of light-receiving element arrays, for example, the light-receiving element array 5-1. Figure 23 5-1 due to parallel movement within
．． Like 5-2: JI alignment can ensure the identity of the two images, but the other sensor pair 13-1.13-2
However, there were problems such as the identity and gender of the two images was not necessarily guaranteed.

(Problems to be Solved by the Invention) The present invention provides a focus detection device using a so-called image shift method, in which a projected image of a field mask placed in the vicinity of a planned image forming plane is not correctly projected onto a light receiving element array surface. However, by using an adjusting means consisting of a prism or an optical member having a predetermined curved surface placed in front of the light-receiving means surface, the projected image of the field mask can be easily and precisely aligned in the direction of the light-receiving element array. It is an object of the present invention to provide a focus detection device having an adjustment means capable of highly accurate focus detection.

(Means for Solving the Problem) A plurality of light intensity distributions regarding a subject image are formed using a light flux that has passed through different regions of the pupil of the objective lens by an optical means disposed on the image plane side of the objective lens, and When determining the relative positional relationship of the light quantity distribution using a light receiving means having at least two light receiving element arrays each consisting of a plurality of elements, and determining the in-focus state of the objective lens using a signal from the light receiving means, the light received An adjusting means is provided in front of the means, which can optically adjust the formation direction of at least one light amount distribution among a plurality of light amount distributions regarding the subject image.

(Example) FIG. 1 is a schematic diagram of an optical system according to an embodiment of the present invention.

In the figure, reference numeral 1 denotes an objective lens, and 2 denotes a field mask, which are arranged near the intended imaging plane of the objective lens 1. Reference numeral 3 denotes a field lens, which is arranged near the intended image plane. Reference numeral 4 denotes a secondary optical system, which is composed of two lenses 4-1 and 4-2 arranged symmetrically with respect to the optical axis of the objective lens l. 5 is a light receiving means, and the two lenses 4-1.4. -2, it has two light receiving element rows 5-1 and 5-2 arranged behind it. A diaphragm 6 has two openings 6-1.6-2 arranged in front of the two lenses 4-1.4-2. 7 is an exit pupil of the objective lens 1, which is composed of two divided regions 7-1 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 pupil 7, and each area? The light beams transmitted through -1 and 7-2 form a luminous temperature distribution on the light receiving element arrays 5-1 and 5-2, respectively.

Reference numeral 16 denotes an adjusting means, which is arranged between the secondary optical system 4 and the light receiving means 5.

FIG. 2 is an embodiment of the adjusting means 16 shown in FIG. 1, and is a perspective view when viewed from the secondary optical system 4 side.

In this embodiment, the adjusting means is an optical member consisting of two members: a transparent parallel plate member 17 having a certain thickness and a transparent prism member 18 having a certain inclination angle in a direction perpendicular to the light receiving element array 5-1. It is made up of more. The light flux that should reach the light-receiving element array 5-1 is set to pass through the member 18, and the light flux that should reach the light-receiving element array 5-2 is transmitted through the member 17. In this embodiment, by moving the optical member 16 in the direction of the arrow 19 in the figure, only the light flux passing through the member 18 is deflected in the direction of the arrow 19 without affecting the light flux passing through the member 17. becomes possible.

For example, suppose that the projected image of the field mask is projected as 8-1.8-2 onto the light-receiving element array 5-1.5-2 on the light-receiving means S as shown in FIG. . By moving the optical member 16 of this embodiment upward,
By moving only the projected image 8-1 of the visual field mask 2 downward without changing the position of the projected image 8-2 of the visual field mask 2, the image 8-1' shown in FIG. It is possible to make the state.

In this state, the positional relationship of the projected image 8-1.8-2 of the field mask 2 with respect to the light-receiving element array pair 5-1.5-2 is the same for both, and the light-receiving element array pair 5-1. It has the same adjustment effect as the adjustment by rotation and translation. Furthermore, as shown below, the ratio of the amount of movement of the projected image of the field mask 2 to the amount of movement of the optical member 16, that is, the adjustment sensitivity, can be set small, and highly accurate adjustment can be easily achieved. FIG. 4 is an explanatory diagram of a cross section of the member 18 of the optical member 16. In the figure, if the prism angle is θ and the refractive index of the prism is n, then the light ray 20 that travels perpendicularly toward a position t on the prism bottom surface and enters the prism slope is refracted and reaches the bottom surface, and the reaching position X is X = t-tanθ・tanφ...(1)・
It is expressed as However, φ is a value expressed by n5in(θ−φ)=sinθ ---(2). Therefore: A integer sensitivity S is now 5LTO,00 assuming θ=8° n=1.5
66 That is, a 1 mm movement of the optical member 16 means that the projected image of the field mask moves by 6 to 7 μm, and highly accurate adjustment of 1 μm or less is possible with a relatively simple adjustment means.

Fifth. 6th. 8th. FIG. 9 sequentially shows the second adjustment means 16 shown in FIG. Third. 4th. FIG. 5 is a schematic diagram of a fifth embodiment.

In the second embodiment shown in FIG. 5, the member 17 of the optical member 16 in the first embodiment shown in FIG. be. In this embodiment, the projected image of the field mask is adjusted by rotating the optical member 21 around an optical axis 22 of an objective lens (not shown). Furthermore, in this embodiment, the projected images of the two field masks simultaneously move in opposite directions during adjustment, so the prism angle can be set smaller to achieve the same adjustment sensitivity compared to the first embodiment. , it has the advantage of being able to reduce various aberrations caused by the prism.

A third embodiment shown in FIG. 6 is an example in which the adjusting means 16 is applied to the focus detection device shown in FIG. 22.

The optical member 25 is a transparent parallel plate member 2 having a certain thickness.
6 and a transparent prism member 27 having a certain angle of inclination in the direction orthogonal to the light receiving element array 13-1, and should reach the light receiving element array 5-1゜5-2.13-2. The arrangement is such that the light beam to reach the light receiving element array 13-1 passes through the member 26, and the light beam to reach the light receiving element array 13-1 passes through the member 27.

Now, initially, due to eccentricity of the secondary optical system, etc., the projected image of the field mask is 14-1°14-2.15-1 as shown in FIG.
．． 15-2 are formed in a shifted manner on the light receiving element array. At this time, by parallelly moving or rotating the light receiving means, the relative positional relationship between the light receiving element array 5-1.5-2 and the projected image 14-1.14-2 of the field mask is made the same for both. The light receiving element row 13-2 is adjusted so that it almost falls within the projected image 15-2 of the field mask. Next, the optical member 25 shown in FIG.
By moving the field mask to the right, only the projected image 15-1 of the field mask in FIG. 7 moves to the left, and finally the state of the projected image 16-1' can be reached, thus completing the adjustment.

In the fourth embodiment shown in FIG. 8, the optical member 29 and the transparent parallel plate member 30° 31 having a constant thickness are arranged at opposite angles to each other in a direction perpendicular to the light receiving element rows 13-1 and 13-2. It is composed of four members, transparent prism members 32, 33 having inclined angles, and light receiving element arrays 5-1, 5-2.
The light beams that should reach 13-1 and 13-2 are respectively connected to member 3.
It is arranged to transmit 0°31.32.33.゛The adjustment in this embodiment is the same as in the second embodiment shown in FIG.
2, the projected image of the field mask corresponding to the light receiving element row 13-1.13-2 is transferred to the light receiving element row 13-1.13.
This is done by moving in mutually opposite directions perpendicular to -2.

In the fifth embodiment shown in FIG.
It is composed of three members: members 36 and 37, which are transparent prism bodies having angles perpendicular to 1 and 13-1, respectively. The beams of light that are to reach the columns 5-1, 13-1 are each arranged to be transmitted through the elements 36, 37.

In this embodiment, by moving the optical member 34 in the vertical direction of the arrow 19, the projected image of the field mask corresponding to the light receiving element row 5-1 is moved vertically, and the optical member 34 is moved in the horizontal direction of the arrow 28. Adjustment is performed by moving the projected image of the field mask corresponding to the light-receiving element row 13-1 independently to the left and right.

In this embodiment, since it is possible to independently move and adjust the projected image of the field mask corresponding to one of the light receiving element rows of each light receiving element row pair, high precision can be achieved for both light receiving element rows. Adjustment is easily achieved.

All of the above embodiments utilize the deflection of light by a prism as an optical member, so even in an ideal reference state where there is no eccentricity of the secondary optical system, the light beam passing through the prism is deflected by a certain amount, and the light receiving means reach. Accordingly, it is effective from the viewpoint of reducing the amount of adjustment to arrange the light-receiving element arrays in a slightly shifted manner in advance, rather than arranging them in a -straight line or in a seven-figure line.

Further, the optical member is not limited to one having a fixed angle of inclination like the prism of the above embodiment, but it is also possible to use one whose inclination angle changes depending on the location, in other words, one having a curved surface.

10th. 12th. FIG. 13 sequentially shows the sixth section of the adjusting means 16 shown in FIG. 7th. FIG. 8 is a schematic diagram of an eighth embodiment, in which the projected image of the field mask is adjusted using a curved member.

In the sixth embodiment shown in FIG.
It is composed of two members, the member 40 consisting of a cylindrical lens having power only in the direction perpendicular to -1,
The arrangement is such that the light flux that should reach the light receiving element array 5-1 passes through the member 40, and the light flux that should reach the light receiving element array 5-2 passes through the member 39. By moving the optical member 38 in the direction of the arrow 19 with such a configuration, only the light beam passing through the member 40 can be deflected in the direction of the arrow without any effect on the light beam passing through the member 39. The same adjustment as in the first embodiment shown in FIG. 2 is possible. FIG. 11 shows the member 4 of the cylindrical lens of the optical member 38.
It is an explanatory diagram showing a cross section of the cylindrical lens, where γ is the radius of curvature of the cylindrical lens, n is the refractive index, dl is the thickness, d2 is the distance from the bottom of the cylindrical lens to the light receiving element row i,
The position X where the light ray 42 that travels perpendicularly toward the position t on the surface of the light-receiving element array 41 and is incident on the cylindrical lens surface is refracted and reaches the light-receiving element array 41 is x = (a+ - (γ-F door-ro). )) jan (θ−φ)+d, tanξ−−(4). However, here θ, φ, ξ are n5in(θ−φ)=
sinξ... is a value expressed by (6). Now, for example, γ=20, d,=1, d2=1, n=1.5
Then, at t=1, x=0.041, and at t=2, x=0.0
80, and the adjustment sensitivity is reduced to about 1/25.

Therefore, as in the embodiment using the prism described above, highly accurate adjustment is possible.

FIG. 12 shows a seventh embodiment using a cylindrical lens, and this embodiment is on the right side of the sixth embodiment shown in FIG. As in the sixth embodiment, adjustment is performed by moving the optical member 42 in the direction of the arrow 19.

This embodiment differs from the fifth embodiment in that the projected images of the two field masks simultaneously move in opposite directions during adjustment by moving the optical member 42.

FIG. 13 is an explanatory diagram showing an eighth embodiment that also uses a cylindrical lens number. In this embodiment, the optical member 45 is composed of one cylindrical lens having power in a direction perpendicular to the light receiving element array, and adjustment is performed by rotating an objective lens (not shown) about the optical axis 22.

14th. 15th. tS and FIG. 17 are sequentially shown in FIG. 9 of the adjusting means 16 shown in FIG. 10th. 11. It is a schematic view of the 12th embodiment, and all of them utilize a member made of a cylindrical lens as an optical member. Also, both are the second
This is applied to the focus detection device shown in FIG.

In the ninth embodiment shown in FIG. 14, only the member 47 through which the light flux that should reach the light receiving element array 13-1 of the optical member 46 is transmitted is a cylindrical lens. This is to adjust the position of the projected image of the visual field mask corresponding to 13-1.

The tenth embodiment shown in FIG.
The members 50 and 52 through which the light flux to reach 3-2 is transmitted are cylindrical lenses having radii of curvature with opposite positive and negative directions, and by moving in the direction of arrow 28, the light receiving element arrays 13-1 and 13-2 are moved. Adjustment is performed by moving the projected images of two corresponding field masks in opposite directions.

The eleventh embodiment shown in FIG. 16 is a light receiving element array 13-1.1.
The members 56 and 57 through which the light flux that should reach 3-2 is transmitted,
Each of the cylindrical lenses has power in a direction perpendicular to the light receiving element array, and the light receiving element array 13-1.13 is rotated around the optical axis 22 of an objective lens (not shown).
Adjustments are made by moving the projected images of the visual field masks corresponding to -2 in opposite directions.

The twelfth embodiment shown in FIG. 17 is a light receiving element array 5-1.13.
The members 60 and 61 through which the light flux that should reach -1 is transmitted are cylindrical lenses each having power in the direction orthogonal to the light receiving element array. By moving the projected image of the field mask corresponding to the light receiving element row 5-1 in the vertical direction of the arrow 19 in the figure, the projected image of the field mask corresponding to the light receiving element row 13-1 is moved in the left and right direction of the arrow 28. Adjustments are made by moving the projected images independently of each other.

In each of the above embodiments, an optical member having a prism and a cylindrical lens has been described as an example of an adjustment means, but the present invention is not limited to this. Any optical member may be used as long as it changes. For example, an optical member may be used in which not only the surface shape but also the internal refractive index changes in a direction perpendicular to the direction of the light receiving element array.

Further, the present invention is not limited to the image shift type focus detection apparatus shown in FIGS. 25 and 22, but can also be applied to focus detection apparatuses having a different field of view shape or using a different method.

Incidentally, since the optical member used in the present invention is suitably used by being located in front of the light receiving means, it can also be used as a protective member such as a cover glass for the light receiving means.

(Effects of the Invention) According to the present invention, highly accurate focus detection is achieved by providing an adjusting means having a predetermined optical effect in front of the light receiving means and adjusting the projection state of the projected image of the field mask on the surface of the light receiving means. A possible focus detection device can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an optical system according to an embodiment of the present invention. Second. Fifth. 6th. 8th. 9th. 10th ° 12th. 1st
3. 14th. 15th. 16 and 17 are schematic diagrams of the first to twelfth embodiments of the adjusting means according to the present invention, and the third. 7th. No. 19゜No. 21. 23rd. 24 is an explanatory diagram showing the relationship between the light-receiving element array and the projected image of the field mask in each image shift type focus detection device, FIG. 4 is a cross-sectional view of a portion of FIG. 2, and FIG. 11 is the diagram of FIG. 10. Partial cross-sectional view, No. 18
The figures are an explanatory diagram of a part of FIG. 1, FIG. 20 is an explanatory diagram showing the relationship between the field mask and the subject, and FIG. FIG. 25 is a schematic diagram of an optical system of a conventional image shift type focus detection device. In the figure, 1 is an objective lens, 2 is a field mask, 3 is a field lens, 4 is a secondary optical system, 5 is a light receiving means, 5-1.5-
2.13-1.13-2 is a light receiving element array, 6 is an aperture, 7 is an exit pupil, 1a, zl. 25.29, 34.3B, 42, 45, 47°50.5
3.58 is an adjustment means, and 8-1.8-2 is a projected image of the field mask 2. Patent applicant Canon Co., Ltd.

Claims (3)

[Claims] (1) Forming a plurality of light intensity distributions regarding the subject image using an optical means disposed on the image plane side of the objective lens using light fluxes that have passed through different areas of the pupil of the objective lens, and comparing the relative light intensity distributions of the plurality of light intensity distributions. When the positional relationship is determined by a light receiving means having at least two light receiving element arrays each consisting of a plurality of elements, and when determining the in-focus state of the objective lens using a signal from the light receiving means, the subject image is placed in front of the light receiving means. What is claimed is: 1. A focus detection device having an adjusting means, comprising: an adjusting means capable of optically adjusting the formation direction of at least one light amount distribution among a plurality of light amount distributions. (2) A focus detection device having an adjusting means according to claim 1, wherein the adjusting means has an optical member that exerts an optical effect in a direction perpendicular to the direction in which the light-receiving element rows are arranged. (3) The focus detection device with adjusting means according to claim 2, wherein the optical member is a prism, a curved member having a predetermined curvature distribution, a cylindrical lens, or a gradient index member.