JPH05142466A - Focus detecting device - Google Patents

Abstract

PURPOSE:To obtain a focus detecting device which can detect the focusing state of a photographing lens corresponding to various kinds of the photographing lenses when the line sensor in an detection area outside an axis is not aligned with the diameter direction of the photographing lens, or when the detection area including an optical axis includes the high part of image height. CONSTITUTION:An optical system for forming an image again which has condenser lenses 20 and 21 and a detecting means constituted of line sensors 40 and 41 are plurally provided for one focus detecting zone 11 on an aimed focusing surface 10, and any one of the plural detecting means is selected corresponding to the change of the position in the optical axis direction of the exit pupil position of the photographing lens, then the focusing state of the photographing lens toward an object positioned in the detection zone 11 is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus detecting device for detecting a focus state of a photographing lens such as a camera on an object.

[0002]

2. Description of the Related Art Conventionally, as a focus detection device for a single-lens reflex camera or the like, light fluxes passing through different parts of the exit pupil of a photographing lens are coupled on a pair of line sensors by reimaging lenses of a focus detection optical system. A configuration is known in which an image is formed and the focusing state of the photographing lens is detected based on the relationship between the output signals of the pair of line sensors. The principle of this focus detection device is detailed in, for example, Japanese Patent Laid-Open No. 2-5.

Further, there is conventionally known a device in which a detection area is provided outside the optical axis in order to detect the focus state of the photographing lens with respect to an object located other than the center of the screen.

However, when the distance of the off-axis detection area from the optical axis becomes large, the pupil of the focus detection optical system is vignetted when the position or size of the exit pupil of the taking lens changes due to lens replacement or zooming. Occasionally, the range in which the light flux can be captured may be narrowed. In such a case, the interchangeable lens that can use the automatic focus detection is limited, or the automatic focus detection device does not work at a specific focal length in the zooming range.

In order to solve such a problem, JP-A-2-
In 58012, in order to eliminate the influence of vignetting of the focus detection system due to the change of the exit pupil of the taking lens, a focus detection device having an off-axis detection area uses a light flux that has passed through three different exit pupils. A configuration is disclosed in which three sets of re-imaging optical systems are provided, and the outputs of the line sensors of the two re-imaging optical systems in which vignetting does not occur are used to perform focus detection on an object in the zone.

[0006]

However, in this prior art, three sets of re-imaging optical systems must be provided for each detection area, and three detection areas outside the optical axis must be provided.
There was a constraint that the direction of the pair of line sensors had to be substantially aligned with the diametrical direction of the taking lens.

Further, when the area to be detected is large, that is, when the image height is high, vignetting may occur in the area including the optical axis of the taking lens. I can't solve the point.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and requires only two re-imaging optical systems for one detection area and a detection area including an optical axis. An object of the present invention is to provide a focus detection device capable of detecting the in-focus state of a photographing lens corresponding to various photographing lenses even when including a portion having a high image height.

[0009]

In order to achieve the above-mentioned object, a focus detection device according to the present invention passes through different portions of the exit pupil of the taking lens and detects a common focus on the planned focal plane of the taking lens. In a focus detection device that refocuses a pair of light fluxes that have passed through a zone to detect the focus state of a photographing lens on an object located in the focus detection zone, one focus detection zone on a planned focal plane is used. On the other hand, a plurality of detecting means are provided, and any one of the plurality of detecting means is selected in accordance with the change of the position of the exit pupil position of the photographing lens in the optical axis direction and is positioned within the focus detection zone. It is characterized in that the focus state of the taking lens on the subject is detected.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

[0011]

First Embodiment FIG. 1 shows a first embodiment of the present invention. In this embodiment, a focus detection zone 11 long in the sagittal direction orthogonal to the diametrical direction is provided at a position deviated from the optical axis Ax of the photographing lens on the planned focal plane 10 on which an image of the subject is formed by the photographing lens (not shown). The focus state of the photographing lens with respect to the image in the detection zone 11 is detected.
The planned focal plane 10 is at a position conjugate with the actual focal plane of the taking lens.

As a general property of the taking lens (zoom lens), the exit pupil EPt of the taking lens at the time of telephoto is farther from the planned focal plane 10 than the exit pupil EPw at the time of wide angle. In addition, the size of the exit pupil also changes with the change in the F number of the taking lens.

Therefore, the apparatus according to the first embodiment is provided with a plurality of detecting means for one focus detecting zone 11, and a plurality of detecting means are provided corresponding to changes in the position of the exit pupil position of the photographing lens in the optical axis direction. Any one of the above is selected to detect the focus state of the photographing lens with respect to the subject located in the focus detection zone. The detection means is composed of two sets of re-imaging optical systems and two sets of line sensors having a pair of light receiving regions.

The first re-imaging optical system takes in a pair of light fluxes, which have passed through portions At and Bt having different exit pupils EPt of the photographing lens at the time of telephoto, by a first condenser lens 20, and a pair of separator lenses 30, First line sensor 40
The images in the detection zone 11 are separated and re-imaged on the two regions 40A and 40B. Similarly, the second re-imaging optical system includes a second condenser lens 21, a pair of separator lenses 32 and 33, and a second
The second line sensor has a line sensor 41, and a pair of light fluxes that have passed through portions Aw and Bw having different exit pupils EPw at the wide angle of the photographing lens via a pair of separator lenses 32 and 33.
An image is formed on the regions 41A and 41B of 41.

Each of the line sensors 40 and 41 has two regions 40 so that it can receive a pair of divided images.
It is composed of A, 40B, 41A, 41B, and by calculating the positional relationship of the images formed in each area, it is possible to detect the focus state of the photographing lens with respect to the subject located in the detection zone 11. ..

That is, the outputs of the line sensors 40 and 41 are input to the signal processing circuit 50 and the arithmetic control circuit 51,
The signal processing circuit 50 and the arithmetic control circuit 51 use the output of the line sensor 40 or 41 to calculate the positional relationship of the divided images to calculate the defocus amount of the subject. The calculation control circuit 51 drives the control motor 52 in the camera body B based on the calculation result, operates the focus adjustment mechanism 54 of the photographing lens L via the drive coupling 53, and moves the focus adjustment lens 55 in the optical axis direction. Move to.

Which output of the line sensors 40 and 41 is used can be determined in advance. The position and size of the exit pupil of the taking lens are determined by its focal length and F value, and these can be stored in the lens ROM or CPU in the interchangeable lens L as data specific to the taking lens. Therefore, by performing communication regarding this stored data between the interchangeable lens L and the camera body B of the single-lens reflex camera by well-known means, the output of either the line sensor 40 or 41 depending on the type of the interchangeable lens. Can be used. In the case of a zoom lens, the line sensors 40 and 41 can be used depending on the focal length.
The output of and can be switched and used. Of course, it is also possible to determine the amount of light incident on the line sensors 40 and 41 and automatically switch and use the output.

The condenser lenses 20 and 21 have a function as a condensing means that takes in the light beams entering the focus detection zone 11 from different directions and forms images on the line sensors 40 and 41, respectively. , 41 are arranged in parallel in a direction orthogonal to the pixel array direction.
These condenser lenses 20 and 21 are arranged at least in the longitudinal direction of the line sensors 40 and 41 (in the pixel array direction) so that the luminous fluxes incident on the detection zone 11 at different angles due to the change of the exit pupil position are aligned and emitted in substantially the same direction. It is formed so that the power in the direction orthogonal to () gradually changes.

With the above configuration, even when the exit pupil of the taking lens changes, the planned focus can be selected by selecting one of the pair of re-imaging optical systems according to the position and size of the exit pupil. It is possible to detect the focus state of the taking lens with respect to the subject at the same position on the surface.

As described above, it is important that both of the two sets of re-imaging optical systems perform the focus detecting function for the subject at the same position when the device is incorporated in a camera. In general, a viewfinder system of an autofocus camera displays a focus detection zone which is a range of focus detection. The photographer can place the target subject in the detection zone in the finder to focus the photographing lens on the subject. However, if the detection zone on the planned focal plane is moved by switching the re-imaging optical system, for example, the detection zone in the viewfinder and the actual detection target zone will not match, and Focusing is performed on a subject that is different from the intended subject.

Next, a modified example of the apparatus shown in FIG. 1 will be described with reference to FIGS.
It will be explained based on 6.

FIG. 2 shows an example in which each re-imaging optical system independently has a line sensor and a separate lens as in the example of FIG. In the optical system of FIG. 2A, each re-imaging optical system has condenser lenses 20A and 21A having substantially the same power, and a prism 21a is provided in front of one condenser lens 21A.
By adding the deflecting action of the prism 21a, it is possible to take in light fluxes incident from different directions even if the same condenser lens is used.

2 to 6, the pixel array direction of the line sensors 40 and 41 is a direction orthogonal to the paper surface.

The optical system shown in FIG. 2 (b) is provided with two condenser lenses 20 and 21 whose powers are gradually changed in the direction orthogonal to the pixel array direction of the line sensor as in the example shown in FIG. There is.

FIG. 2C shows an example in which a common aspherical condenser lens 20B is used for each re-imaging optical system. This aspherical condenser lens 20B is formed so that the power becomes stronger as it goes away from the center, and the light flux that has passed through the high image height portion is refracted more than the light flux that has passed through the central portion, and is in substantially the same direction. Is ejected.

FIG. 3 shows an example in which a single condenser lens 20C is used and a prism 20a is provided in the optical path of a re-imaging optical system that takes in a light beam at a wide angle. This makes it possible to align the directions of the light beams that enter from different directions.

4 and 5 show an example in which two re-imaging optical systems share a separate lens. These examples, by strengthening the power of one of the condensing means (condenser lenses 21, 21A, 21B) in the example shown in FIGS. 1 to 3, the light flux is incident on the common separator lens 30, 31,
An image is formed on the separate line sensors 40 and 41.
That is, the separator lenses 32 and 33 in the above example are not provided in this example.

FIG. 4 (a) shows an example in which condenser lenses 20D and 21D having different powers are provided, and FIG. 4 (b) shows a condenser means for taking in a luminous flux at the time of telephoto as a condenser lens 20E and a prism 20a. This is an example in which a synthetic optical system is used and the other condensing optical system is configured by a single condenser lens 21E.

FIG. 5A shows a pair of condenser lenses 20.
Condenser lens 2 that takes in the light flux at wide angle among F and 21F
The optical axis of 1F is tilted, and the prism is behind it.
21a is provided, FIG. 5 (b) is an example in which a single aspherical condenser lens 20G formed so that its power becomes stronger as it goes away from the center is commonly used in two sets of re-imaging optical systems.
5 (c) is an example in which the condenser lens 20H is shared and the prism 20a is provided in the optical path of the re-imaging optical system that takes in a light beam at a wide angle.

FIG. 6 shows an example in which the line sensor 40 is shared by a pair of re-imaging optical systems. In order to share the line sensor, it is necessary to block the optical path of the unused re-imaging optical system and detect only the light flux of the one re-imaging optical system depending on the position of the exit pupil. is there.

Therefore, in the example of FIG. 6 (a), a single condenser lens 20J is used, and a prism 20a is provided in the optical path of the re-imaging optical system that takes in a light beam at a wide angle. Light shield 5
0 is for blocking the optical path of one re-imaging optical system that is not used for detection, and is movable in the direction of the arrow in the figure. FIG. 6 (b) shows that in addition to the elements of FIG. 6 (a), the prism 2
An example in which 0b is provided is shown.

A separator lens as in the above embodiments,
Alternatively, the line sensor can be commonly used by both re-imaging optical systems to reduce the number of components.

In the above example, in order to simplify the description, only the single detection zone 11 provided outside the optical axis has been described. However, when it is mounted on a camera, for example, regarding the optical axis, It is practical to provide detection zones at positions symmetrical to the above detection zone 11 and at positions including the optical axis, and detect the in-focus state of the taking lens using the detection zones corresponding to the subject to be focused. And is preferable.

FIG. 7 shows another embodiment of the present invention. In this example, the detection zone 12 is the planned focal plane.
It is arranged at the center of 10, that is, at a position including the optical axis Ax of the taking lens. Two sets of re-imaging optical systems are provided for the detection zone 12 so as to be selectable.

The light flux which passes through the detection zone 12 and enters from the portions Aw and Bw having different exit pupils EPw at the wide angle of the photographing lens is condensed and deflected by the first condenser lens 22,
Area 42 of line sensor 42 by separator lenses 34, 35
An image is formed on A and 42B. On the other hand, the light flux that passes through the detection zone 12 and enters from the different portions At and Bt of the exit pupil EPt at the time of telephoto is condensed and deflected by the second condenser lens 23,
An image is formed on the line sensor 43 by the separator lenses 34 and 35. On both line sensors 42 and 43, the detection zone 1
The same subject image formed in 2 is divided and formed.

When the detection zones 12 are provided symmetrically with each other including the optical axis, if the width of the detection zones 12 in the longitudinal direction is narrow, it is unlikely to be affected by the change of the exit pupil. However, when the width is set wide, as shown in FIG. 8, in the high image height portion, the overlapping portion of the light flux captured from the exit pupil EPt at telephoto and the light flux captured from the exit pupil EPw at wide angle. Therefore, for example, if a single condenser lens 23 that can capture a light beam at the time of telephoto is used, it becomes impossible to capture a light beam that forms an image of a portion having a high image height at a wide angle.

Therefore, in this embodiment, a re-imaging optical system having a condenser lens 22 having a strong power and a re-imaging optical system having a condenser lens 23 having a weak power are provided side by side, and a condenser lens having a weak power at the time of telephoto. An image is formed on the line sensor 43 by using a re-imaging optical system composed of 23 and common separator lenses 34 and 35, and is composed of a condenser lens 22 having strong power and a common separator lens 34 and 35 at wide angle. The re-imaging optical system described above is used to form an image on the line sensor 42.

[0038]

As described above, according to the present invention, by selecting the detecting means according to the change in the position and size of the exit pupil of the photographing lens, the vignetting of the light flux is suppressed and the line sensor is reached. It is possible to secure a sufficient amount of light flux, and it is possible to accurately detect the in-focus state of the taking lens.

[Brief description of drawings]

FIG. 1 is a perspective view showing a focus detection device according to a first embodiment.

2A and 2B are diagrams showing a main part of a modified example of the first embodiment, in which FIG. 2A is an example using two condenser lenses and a prism having the same power, and FIG. An example using a condenser lens, (c) is an example using a single aspherical condenser lens.

FIG. 3 shows a main part of a modified example of the first embodiment using a single condenser lens and a prism.

4A and 4B show a main part of a modified example of the first embodiment sharing a separator lens, FIG. 4A being an example using two condenser lenses having different powers, and FIG. 4B being different in powers. This is an example using two condenser lenses and a prism.

FIG. 5 shows a main part of a modified example of the first embodiment in which a separator lens is shared, and (a) is an example using two condenser lenses and a prism having different powers,
(b) is an example using a single aspherical condenser lens, and (c) is an example using a single condenser lens and a prism.

6A and 6B show a main part of a modification of the first embodiment sharing a line sensor, in which FIG. 6A is an example using a single condenser lens and one prism, and FIG. This is an example using a single condenser lens and two prisms.

FIG. 7 is a perspective view showing a focus detection device according to another embodiment.

FIG. 8 is a plan view of the device of FIG.

[Explanation of symbols]

 10… Planned focal plane 11, 12… Detection zone 20, 21, 22, 23… Condenser lens 20a, 21a, 21b… Prism 30, 31, 32, 33, 34, 35… Separator lens 40, 41, 42, 43… Line sensor

Claims (23)

[Claims] 1. A pair of light fluxes, which have passed through different portions of the exit pupil of the photographing lens and have passed through a common focus detection zone on the planned focal plane of the photographing lens, are re-imaged into the focus detection zone. In a focus detection device for detecting a focus state of the photographing lens on a subject located therein, a plurality of detecting means are provided for one focus detection zone on the planned focal plane, and an exit pupil position of the photographing lens is provided. Of the plurality of detecting means corresponding to the change of the position in the optical axis direction, and detects the focus state of the photographing lens with respect to the subject located in the focus detection zone. A focus detection device. 2. The detecting means comprises a plurality of re-imaging optical systems,
The focus detection device according to claim 1, further comprising a plurality of line sensors having a pair of light receiving regions. 3. The re-imaging optical system separates a condenser lens into which the pair of light fluxes are incident and a light flux corresponding to the pair of light fluxes emitted from the condenser lens into the pair of line sensors. The focus detection device according to claim 2, further comprising: a separator lens that makes the light incident. 4. A pair of light fluxes, which have passed through different portions of the exit pupil of the taking lens and passed through a common focus detection zone on the planned focal plane of the taking lens, are respectively corresponded via re-imaging optical systems. In a focus detection device for re-imaging on a pair of line sensors, respectively, the pair of light fluxes incident on the focus detection zone from different directions are re-imaged according to a change in the position of the exit pupil in the optical axis direction. At least two sets of re-imaging optical systems for forming images, and images are formed by these two sets of re-imaging optical systems, respectively.
A focus detection device comprising: at least a pair of line sensors on which an image is formed by the pair of light beams. 5. The two sets of re-imaging optical systems correspond to one condenser lens to which the pair of light beams having different incident angles with respect to a focus detection zone are incident, and the pair of light beams emitted from the condenser lens. The focus detection device according to claim 4, further comprising: a separator lens that separates the incident light flux into the pair of line sensors and makes the incident light. 6. The two sets of re-imaging optical systems include a condenser lens common to the two sets of re-imaging optical systems, and a light beam corresponding to a pair of light beams emitted from the condenser lens, the pair of lines. The focus detection device according to claim 4, further comprising a separator lens that separates and enters the sensor. 7. A prism for refracting an optical path is disposed in front of or behind the common condenser lens in one of the two sets of re-imaging optical systems. The focus detection device described in 1. 8. The pair of re-imaging optical systems receives the pair of light beams having different incident angles with respect to the focus detection zone.
Two sets of re-imaging optics, in which separate condenser lenses are provided in the two sets of re-imaging optical systems, and light beams corresponding to the pair of light beams emitted from the condenser lenses are separated and made incident on the pair of line sensors. The focus detection device according to claim 4, further comprising a separator lens common to the system. 9. The pair of line sensors are respectively provided in two sets of re-imaging optical systems, and a pair of light fluxes which have passed through the common separator lens and are incident on the focus detection zone from different directions are respectively provided. 9. The focus detection device according to claim 8, wherein an image is formed on the line sensor. 10. The focus detection device according to claim 4, wherein the pair of line sensors are provided separately for each of the two sets of re-imaging optical systems. 11. The focus detection device according to claim 10, wherein one of the two sets of line sensors is selectively used according to the position of the exit pupil. 12. The pair of line sensors are common to two sets of re-imaging optical systems.
The focus detection device described in 1. 13. The two sets of re-imaging optical systems include a condenser lens common to the two sets of re-imaging optical systems, and a light beam corresponding to a pair of light beams emitted from the condenser lens. The focus detection device according to claim 12, further comprising a separator lens that separates and enters the sensor. 14. A prism for refracting an optical path is arranged in front of or behind the common condenser lens in one of the two sets of re-imaging optical systems. The focus detection device described in 1. 15. The focus according to claim 14, wherein at least one of the two sets of re-imaging optical system is provided with a light-shielding means for blocking an optical path of the re-imaging optical system. Detection device. 16. The focus detecting apparatus according to claim 15, wherein the light shielding means shields the re-imaging optical system when the re-imaging optical system is not used. 17. The focus detection device according to claim 4, wherein the focus detection zone is provided outside the optical axis of the taking lens. 18. The focus detection device according to claim 4, wherein the taking lens is an interchangeable lens of a single lens reflex camera. 19. The focus detection device according to claim 4, wherein the taking lens is a zoom lens. 20. A first re-imaging for re-imaging an image of a fixed focus detection zone on a planned focal plane formed by a taking lens on a pair of line sensors through a first condensing means. An optical system, and a second condensing means arranged side by side with the first condensing means, spaced apart in a direction orthogonal to the pixel array direction of the line sensor, the first re-imaging optics By a light beam entering from a direction different from the light beam entering the system, an image of the fixed region on the planned focal plane is passed through the second converging means to the pair of line sensors, or another line sensor. And a second re-imaging optical system for re-imaging on a pair of line sensors. 21. The first and second re-imaging optical systems each have an independent pair of line sensors, and are provided between the first and second condensing means and the pair of line sensors. The focus detection device according to claim 20, wherein the focus detection device has a common separator lens. 22. The focus detection device according to claim 20, wherein the first and second re-imaging optical systems have independent separator lenses and line sensors, respectively. 23. The first and second re-imaging optical systems each have an independent separator lens, and selectively block a common line sensor and a light beam passing through one of the separator lenses. 21. The focus detection device according to claim 20, further comprising a shielding unit that operates.