JP3388108B2 - Focus detection device for camera - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus detection device that receives subject light that has passed through an objective lens of a camera and performs focus detection.

[0002]

2. Description of the Related Art In a single-lens reflex autofocus camera or the like, a phase difference detection method using a recombination lens is used as a device for detecting the focal position of edges of a subject in the vertical and horizontal directions. This type of focus detection device is proposed in which line sensors are arranged so as to form a cross in the horizontal direction and the vertical direction (Japanese Patent Laid- Open No. 62-2126).
11 , JP-A-62-95511, JP-A-1-25100
8).

[0003] FIG. 5 is one of the above-mentioned proposed (JP-A-62- 21
2611 ), the basic structure of the other proposals is the same. Part of the subject light that has passed through the taking lens 31 is guided to a focus detection device 32 provided below the mirror.
The focus detection device 32 includes a field mask 33 in which a linear opening 33X is formed in a cross shape in the horizontal and vertical directions X and Y with respect to the optical axis LH, a condenser lens 34, and four openings 35a and 35.
The split pupil mask 3 in which b, 35c, and 35d are arranged in the horizontal and vertical directions X and Y at a predetermined distance from the optical axis LH.
5, 4 convex lenses 36a, 36b, 36c, 36d are recombined with a reciprocal lens 36 and 4 line sensors 37a, 37b, which are arranged at predetermined intervals in the horizontal and vertical directions X, Y with respect to the optical axis LH. A light receiving portion 37 formed by arranging light receiving elements such as 37c and 37d in a cross shape is sequentially arranged on the optical axis LH of the taking lens 31.

The subject light that has passed through the first photographic image 31a formed on the photographic lens 31 with the above-described structure passes through the field mask 33, the condenser lens 34, and the first opening 35a of the split pupil mask 35, First of recombination lens 36
The convex lens 36a forms a blurred image or a sharp image of the subject on the first line sensor 37a of the light receiving unit 37. Further, the second captured image 31b is similarly formed on the first line sensor 37b . It is determined whether the subject images on the first and second line sensors 37a and 37b approach each other or move away from each other, and it is determined whether the subject is a front focus or a rear focus. If it is an intermediate position, it is determined that the focus adjustment state is set.

In this way, the information of the secondary image obtained from the first and second line sensors 37a and 37b is arithmetically processed to detect the focus adjustment state of the taking lens 31 based on the lateral luminance distribution of the subject. . Also in the vertical direction, the focus adjustment state is detected based on the information from the third and fourth line sensors 37c and 37d.

An arrangement in which the recombining lens is modified as shown in FIG. 6 in the above construction is disclosed in Japanese Patent Laid-Open No. 62-955.
11 proposals. The recombination lens 38 has a lateral first
The lens 38a and the second lens 38b, and the third lens 38c and the fourth lens 38d in the vertical direction are connected to the optical axis LH so that the optical axis intervals of the respective lenses are narrowed. It is the one. As a result, the effective area of the lens is increased so that the subject light can be used efficiently. Further, JP-A-1-251008 proposes an improved recombination lens so that the detection optical system depending on the luminance distribution in the vertical direction and the detection optical system depending on the horizontal direction can be adapted to different optical designs.

[0007]

Since all of the above proposals are based on the line sensor, they can only detect the focus in a limited area in the vertical and horizontal directions of the subject image.
There is a drawback in that the focus detection of edges in the vertical direction and the horizontal direction must be performed by the respective line sensors. An object of the present invention is to provide a focus detection device for a camera, which uses a two-dimensional image pickup device for a distance measurement sensor, can detect both vertical and horizontal edges in a wide distance measurement area, and can effectively use an image pickup surface. It is in.

[0008]

In order to solve the above-mentioned problems, a focus detection device for a camera according to the present invention has a distance measuring area as a central distance measuring area and outside of left and right sides of the central distance measuring area facing each other. divided into three areas of the left and right distance measuring area is formed, the by image rotation moving means
Object light passing through the left and right ranging areas is rotated 90 degrees about the optical axis to face each other in the central ranging area.
The object light in the left and right distance measuring areas and the object light in the central distance measuring area, which are moved to the outside of the upper and lower sides of the upper and lower sides by the image rotation moving means, are rotated to the two-dimensional image sensor. The two-dimensional image pickup device is configured to receive a pair of light beams and detect the focal positions of the edges in the vertical and horizontal directions of the camera photographing area. Further, the image rotation moving means in the present invention is a prism block that combines a plurality of prisms and reflects the light an odd number of times .
And a condenser lens for making the subject light in the right distance measuring area enter the prism block, and a pair of subject light emitted from the prism block and the subject light emitted from the central condenser lens to form a pair on the two-dimensional image sensor. And an imaging lens.

[0009]

According to the above construction, the focus detection of the edges in the vertical direction and the horizontal direction can be performed on one two-dimensional sensor, and the left and right distance measuring areas can be connected to the other sides from the both sides of the central distance measuring area. By moving to the outer portion, it is possible to widen the distance between the two distance measurement areas formed on the two-dimensional image pickup device, increase the focus detection sensitivity, and effectively use each pixel of the two-dimensional image pickup device.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below with reference to the drawings. FIG. 1 is a schematic perspective view showing the basic configuration of a focus detection device for a camera according to the present invention. The subject light in the right distance measuring area 1, the center distance measuring area 2 and the left distance measuring area 3 imaged on the film equivalent surface is condensed by the respective lenses 4a, 4b and 4c of the condenser lens 4.

The subject light that has passed through the lenses 4a and 4c is input to prism blocks 5 and 6, respectively.
The prism blocks 5 and 6 are one flat glass plate 5a,
6a and three 45 degree prisms 5b, 5c, 5d, 6b,
It is composed of 6c and 6d, and the subject light is reflected by each prism three times in total. As a result, the subject light rotates to the right by 90 degrees with respect to the optical axis and moves to the outside of the upper and lower sides adjacent to the left and right facing sides of the central distance measuring area 2. Areas 7, 8 and 9 show images formed on the two-dimensional image pickup device when the re-imaging lens is omitted. As described above, in the film equivalent surface, the horizontally arranged distance measuring areas become vertically arranged distance measuring areas on the two-dimensional image pickup device.

FIG. 2 is a side view showing an embodiment of a focus detecting device for a camera according to the present invention, which is incorporated in a camera. The light from the subject that has passed through the taking lens passes through the central portion of the up-down mirror 10, is reflected by the AF mirror 11, and is guided downward. The light from the subject guided downward passes through the film equivalent surface and is guided forward by the reflection mirror 12. The camera focus detection device of FIG. 1 is installed below the up-down mirror 10 of the camera, and the light of the subject from the reflection mirror 12 enters. The camera focus detection device is composed of a condenser lens 4, two prism blocks 5, 6, a re-imaging lens 14 and a two-dimensional CCD image pickup device 15. The re-imaging lens 14 projects a pair of images so that the phase difference can be detected in the three distance measuring areas arranged in the horizontal direction to the vertical direction.

FIG. 3 shows a film equivalent surface and a two-dimensional CC.
It is a figure which shows an example of the ranging area of the D image sensor surface. As shown in (a), the distance-measuring area is provided with a central distance-measuring area capable of measuring a vertical edge in the center of the film equivalent range, and lateral edge-measuring is possible on both sides thereof. Two side distance measurement areas are set. The two-dimensional CCD image pickup device 15 projects a pair of distance measuring areas. On the right side of the center of the two-dimensional CCD image pickup device 15, the right distance measuring area CCD image pickup surface A19 and the center distance measuring area CCD image pickup surface A
18 and a left side distance measuring area CCD image pickup surface A20 are formed, and a right side distance measuring area CCD image pickup surface B is formed in the left side portion from the center.
22, a central distance measuring area CCD image pickup surface B21 and a left distance measuring area CCD image pickup surface B23 are formed.

The amount of defocus (defocus amount) from the focus on the primary image plane (film equivalent plane) is calculated based on how much the distances between the center, right side and left side distance measuring areas A and B are apart. can do. A dotted line frame 24 shows a state in which the right distance measuring area CCD image pickup surface A19 has moved with respect to a constant defocus amount. It moves not only horizontally but also vertically. The other areas move as well. With one scan of the two-dimensional CCD image pickup device 15, the distances in the center, the right side, and the left side distance measuring areas are measured, and the distances in the vertical and horizontal edges can be measured.

FIG. 4 is a diagram showing another example of the arrangement of the distance measurement areas on the surface of the two-dimensional CCD image pickup device. Central distance measuring area CCD image pickup surface 26 projected onto the two-dimensional CCD image pickup element 25,
On the lower side of 27, right side distance measuring area CCD image pickup surfaces 28a, 29
a and the left distance measuring area CCD image pickup surfaces 28b and 29b are arranged in a projected manner. In this way, even if the distance measuring areas are arranged by the prism block, the focus position can be detected in the same manner.

As described above, according to the present invention, by using the two-dimensional image pickup device, the focus detection of the edges in the vertical direction and the horizontal direction can be performed by scanning in the same direction. By rotating both side distance measurement areas by 90 degrees and moving them to the outside of the adjacent side, there is a margin on both sides of the central distance measurement area on the two-dimensional image pickup element, so that the phase difference detection method allows the two-dimensional image pickup element to be positioned on the two-dimensional image pickup element. The focus detection sensitivity can be increased by increasing the distance between the two center distance measurement areas to be imaged. Further, the both side distance measuring areas are rotated by 90 degrees and moved to the outside portion of the adjacent side, and the outside portions of the upper and lower sides (including only the upper side or the lower side) of the central area which are not normally used are used. Therefore, each pixel of the two-dimensional image sensor can be effectively used. Further, there is an effect that the distance measuring area can be set in a wide range of the surface area of the two-dimensional image sensor.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing a basic configuration of a focus detection device for a camera according to the present invention.

FIG. 2 is a side view showing an embodiment of a focus detection device for a camera according to the present invention incorporated in a camera.

FIG. 3 is a diagram showing an example of distance measurement areas on a film equivalent surface and a two-dimensional CCD image pickup element surface.

FIG. 4 is a diagram showing another example of a distance measuring area on the surface of a two-dimensional CCD image pickup device.

FIG. 5 is a diagram showing a cross-shaped distance measuring structure of a conventional focus detection device.

FIG. 6 is a diagram showing a structure of a re-imaging lens.

[Explanation of symbols]

1 ... Right ranging area 2 ... Central distance measuring area 3 ... Left ranging area 4 ... Condenser lens 5, 6 ... Prism block 7, 8, 9 ... Distance measuring area on the 2D CCD image sensor surface 10 ... Up-down mirror 11 ... AF mirror 12 ... Reflective mirror 14 ... Re-imaging lens (separator lens) 15 ... Two-dimensional CCD image sensor 16 ... Film equivalent surface

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-7-72380 (JP, A) JP-A-6-109970 (JP, A) JP-A-8-194153 (JP, A) JP-A-5- 56355 (JP, A) JP-A-3-214133 (JP, A) JP-B-46-37957 (JP, B1) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02B 7/28-7 / 40

Claims (2)

(57) [Claims] 1. A divided into three areas of the left and right distance measuring area is formed outside the left and right sides facing each other of the distance measuring area central distance measuring area and before <br/> Symbol central distance measuring area The image rotation moving means rotates the object light passing through the left and right distance measuring areas by 90 degrees about the optical axis ,
Upper or lower of the upper and lower sides facing each other in the centering area
To the outside of the camera, and the two-dimensional image pickup device is made to receive a pair of the object light in the left and right ranging areas and the object light in the central ranging area, which are rotated by the image rotation moving means, to receive a pair of them. A focus detection device for a camera, wherein the focus positions of edges in the vertical and horizontal directions are detected by the two-dimensional image pickup device. Wherein said image rotation moving means is a prism block for reflecting an odd number of times combining a plurality of prisms, the divided three areas subject light respectively condensing, left
A condenser lens that makes the subject light in the side and right distance measurement areas incident on the prism block, and a pair of subject light that is emitted from the prism block and the subject light that is emitted from the central condenser lens are focused on the two-dimensional image sensor. The focus detecting device for a camera according to claim 1 , further comprising a re-imaging lens.