JPH046509A - Focus detector - Google Patents

Abstract

PURPOSE:To enable focus detection at various positions in a visual field and to obtain high focus detection accuracy and image forming performance by composing a secondary image formation system of >=2 lenses with positive refracting power, and making at least one of their lens surfaces aspherical. CONSTITUTION:The secondary image formation optical system consists of a lens system which is arranged behind a brightness stop 25 and equipped with at least two lenses 26 and 27 having positive refracting power while at least one surface is made aspherical. A 2nd lens which causes trouble in correcting the aberration of both a pupil system and a visual field system excellently like a conventional example can, therefore, be omitted. Consequently, the aberrations of the pupil system can be compensated sufficiently by a condenser lens 24 and the aberration of the visual field system can be compensated sufficiently by the lens which has the positive refracting power and is arranged behind a brightness stop. Consequently, one optional couple of secondary images can be formed on a photoelectric converting element over the wide visual field range of a body without providing many secondary image formation optical systems successively, and the high focus detection accuracy and image formation performance can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a focus detection device used in a camera, a still video camera, a video camera, and the like.

[Conventional technology]

As a conventional focus detection device of this kind, for example, Japanese Patent Laid-Open No. 62-3
The device described in the 2012 publication includes a photographing lens 1, a flip-up quick return mirror 3 consisting of a half mirror pivotally mounted in a mirror box 2, and a quick return mirror 3, as shown in FIG. 1O. When the quick return mirror 3 is pivoted on the back side and is in the down position (the position shown in the figure), it is perpendicular to the quick return mirror 3 as shown in the figure, but when the quick return mirror 3 is in the up position, the quick A sub-mirror 4 that is in close contact with the back surface of the return mirror 3, a film surface 5 placed behind the sub-mirror 4 on the rear surface of the mirror box 2, and a film surface 5 that is on the optical path reflected by the sub-mirror 4 and is equivalent to the film surface 5. A field stop 6 placed on the surface, a condenser lens (pupil projection lens) 7 placed near the field stop 6, a mirror 8 placed behind the condenser lens 7, and a mirror 8 placed behind the mirror 8. An aperture diaphragm 9 having a pair of apertures arranged in a direction perpendicular to the plane of the paper with an interval that ensures focusing accuracy, and an aperture diaphragm 9 arranged behind each of the pair of aperture diaphragms 9 in a direction perpendicular to the plane of the paper. a pair of separator lenses (re-imaging lenses) 10 lined up, a light-receiving element 11 arranged at the image-forming position of the separator lens 10;
A matte surface 12 provided on the optical path reflected by the quick return mirror 3 and on a surface equivalent to the film surface 5, a condenser lens 13 provided in front of the matte surface 12, and a condenser lens 13 provided at the same position as the matte surface 12. field aperture 1
4, a pentaprism I5 whose entrance surface is located behind the matte surface 12, and an eyepiece lens 16 which is located behind the exit surface of the pentaprism 15. The photographing lens 1 and the film surface 5 constituted an imaging optical system. Also, quick return mirror 3, sub mirror 4, field diaphragm 6, condenser lens 7 and mirror 8
and a pair of apertures of the aperture diaphragm 9, a pair of separator lenses 10, and a light receiving element 11 detect the relative positional relationship of the pair of subject images using the light beams that have passed through different areas of the photographic lens 1, thereby determining the focus. It consisted of a phase-difference type fish collection detection optical system that performs detection. Furthermore, the quick return mirror 3, condenser lens 13, matte surface 12, field stop 14, pentaprism 15, and eyepiece lens 1G constituted a finder optical system.

That is, when the quick return mirror 3 is in the up position, a primary image I of the object point O is captured by the photographing lens 1. is imaged onto the film surface 5.

In addition, when the quick return mirror 3 is in the down position, the light flux that passes through the quick return mirror 3 out of the light flux formed by the photographic lens 1 is guided to the focus detection optical system, and the light flux reflected by the quick return mirror 3 is guided to the finder optical system.

In the focus detection optical system, the light beam transmitted through the quick return mirror 3 is reflected by the submirror 4 to form a primary image 1 of the object point O.
．． is imaged onto a field stop 6, and then a condenser lens 7, a mirror 8. A pair of apertures of the Meirusa aperture 9,
A pair of secondary images 1, , I are formed on a light receiving element 11 via a pair of separator lenses 10.

In the finder optical system, the light beam reflected by the quick return mirror 3 is generally condensed by the condenser lens 13, and the primary image of object point 0 (, /) is formed on the matte surface 12, and then the field diaphragm 14 is converted into an erect image by a pentaprism 15, magnified by an eyepiece lens 16, and observed at an eye point EP.

In addition, in the focus detection optical system, the exit pupil P of the photographic lens 1
The image is formed on the aperture diaphragm 9 by the condenser lens 7, and the two light beams that have passed through different areas of the exit pupil P are separated by the pair of apertures in the aperture diaphragm 9 and the pair of separator lenses 1O. is the light receiving element l while maintaining a certain baseline length (distance between the centers of gravity of both luminous fluxes (referred to as the centroid luminous flux)).
L is led on.

In addition, as a focus detection device based on the above-mentioned conventional technology, it is possible to detect focus not only at the center of the photographic screen but also at the periphery. There are things listed.

Explaining the former with reference to Figure 11, this is because in a phase difference optical system with a large NA, the resolution around the field of view decreases, so it is The field of view is expanded by providing three sets of phase difference optical systems in line.

That is, in FIG. 11, the field stop 6 has three apertures 6a, 6b, and 6c arranged in the long side direction, and the condenser lens 7 has three lenses 7a corresponding to the apertures 6a, 6b, and 6C, respectively. . , three pairs of separator lenses 10 a, l Ob, corresponding to the three pairs of openings 9 a, 9 b, 9 c, respectively.
The light-receiving elements 11 are three light-receiving elements 11a arranged in parallel in the longitudinal direction, corresponding to the three pairs of separator lenses 10a, 10b, and loc, respectively.

11b, llc.

The imaging light beam formed by the photographing lens l has its field of view determined by the three apertures 6a, 6b, and 6c of the field diaphragm 6, and forms three primary images A, BC1 at the apertures 6a, 6b, and 6c.
6b, 6c, respectively, and then three condenser lenses 7a, 7b, 7c, three pairs of apertures 9a, 9b, 9c of the aperture diaphragm 9, and three pairs of separator lenses 10a, 1
Three light receiving parts IIa of the light receiving element 11 via 0b and 10c
, llb, and 11c, respectively, have parallaxes.
2, B2, and C2. Also, the image of the exit pupil P of the photographing lens 1 is formed by three condenser lenses 7.
a, 7b, and 7c form three pairs of apertures 9a of the aperture diaphragm 9.
, 9b, 9c, and the three pairs of openings 9a.

9b, 9c and three pairs of separator lenses 10a.

10b and 10c, the two light fluxes that have passed through different areas of the exit pupil P maintain the baseline length and are directed to each light receiving portion 1 of the light receiving element 11.
1a, llb, and llc, respectively.

In addition, the latter has a field diaphragm 6 orthogonal to the optical axis of the photographic lens 1.
Apertures are arranged in parallel in the long side direction to define discrete focus detection areas limited to the apertures, and a field of view for forming discrete images corresponding to the apertures on the line sensor lid of the light receiving element 11. It is composed of a dual optical system consisting of a transmission optical system (hereinafter referred to as the viewing system) and a pupil transmission optical system (hereinafter referred to as the pupil system) that images the exit pupil P of the photographing lens 1 onto the aperture diaphragm 9. It is something.

That is, in FIG. 12, the field diaphragm 6 has seven openings 6d lined up in the long side direction, behind which a field lens 18 consisting of, for example, five compound lenses is arranged, and further behind it a plano-convex field lens 6d. The aperture stop 9 behind the second lens 19 is provided with a pair of openings 9d in the short side direction of the field stop 6. The light receiving element 11 includes line sensors 11 whose number is equal to the number of apertures 6d of the field diaphragm 6.
d is provided corresponding to the aperture 6d, and a pair of separator lenses 20 corresponding to the aperture 9d of the aperture diaphragm 9 and a fourth lens 21 are arranged between the aperture diaphragm 9 and the light receiving element 11. has been done.

The image-forming light flux by the photographing lens 1 focuses different parts of the object image on each line sensor lid as a pair of object images via the separator lens 20 according to each aperture 6d of the field diaphragm 6. be imaged. Note that FIG. 13 is a view of the focus detection optical system cut along a plane parallel to the short side direction of the aperture diaphragm 9 passing through the principal optical axis, as seen from the short side direction. The optical axes of the separator lenses 20 passing through the aperture 9d of the aperture diaphragm 9 are arranged at certain intervals at positions symmetrical in the short side direction eccentric to the main optical axis.

In the viewing system, the field lens 18 is close to the primary image of the photographing lens 1, so it hardly contributes to image formation, and the secondary image is mainly formed by the second lens 19, separator lens 20, and fourth lens 21. is imaged. Furthermore, in the pupil system, imaging is performed by a field lens 18 and a second lens 20. Therefore, the second lens 20
plays a major role in both the field of view and the pupil transmission optics.

[Problem to be solved by the invention]

However, the above conventional example has the following drawbacks.

(1) The focus detection area extends only in the long side direction of the photographic field and does not extend in the short side direction (
(See Figures 11 and 12).

(ii) The focus detection area is discrete.

In the field system, expanding the focus detection area means increasing the NA and brightening the optical system in the pupil system.
The field stop 6 in the field system corresponds to the brightness stop in the pupil system.

In the prior art, the NA of the pupil system is considerably reduced because the apertures of the aperture diaphragm are arranged discretely in the long side direction and are formed in the shape of a slit with an extremely narrow width.

For this reason, the distance between the centers of gravity of the two images on the light receiving element ll somehow remains within the tolerance range for the base line length.

However, in order to improve the drawback of (i) above, each opening of the field stop 6 is widened greatly in the short side direction, and (ii)
) If the mask between the discrete apertures is eliminated in order to improve the disadvantages of pupil system, the NA of the pupil system becomes extremely large.
In the optical system with the above-mentioned boiling configuration, aberrations of the pupil system including spherical aberration increase. As a result, a disadvantage arises in that the focus detection accuracy of the visual field system cannot be maintained at a required level.

In particular, in the device disclosed in JP-A-1-120518, the second lens 19 that acts on both the pupil system and the visual field system is designed to increase the NA to improve the performance of the pupil system, and to reduce aberrations to improve the visual field system. The presence of this second lens 19 makes it difficult to improve the imaging performance of both systems at the same time, since improving the performance of both systems is contradictory to each other.

Further, the condenser lens 7 includes three lenses 7a.

7b and 7c are combined, and each field lens 18 constitutes a composite field lens in which five lenses are combined, but there is a large step at the connecting part of these lenses 7 and 18,
A ghost image is generated by the light flux passing through this portion. When the mask of the field diaphragm 6 is widened as described above, this ghost image will reach the image sensor of the light receiving element 11, which also causes a decrease in focus detection accuracy. .

Furthermore, when attempting to solve the drawbacks (i) and (m) as described above, the object height of the primary image, that is, the image of the visual field system, increases in any of the conventional devices.

However, maintaining good imaging performance on the sensor surface over the entire increased object height, as well as maintaining the distance error between the two secondary images within an acceptable range, is the key to maintaining the conventional separator lens. This was not possible due to the configuration.

(ii) It is difficult to adjust the optical axis.

The above-mentioned conventional devices have a combination of condenser lenses and separator lenses, or are arranged in pairs.
There are many optical axes, and adjusting the position of each optical axis is complicated and difficult.

In particular, in the device disclosed in Japanese Patent Application Laid-Open No. 63-131111, there are three condenser lenses 7a and 7b.

7c, one set of separator lenses 10a, respectively.
Because of the presence of Adjustment with the central axis is required.

In view of these problems, it is an object of the present invention to provide a focus detection device that can perform focus detection at various positions within the field of view and at the same time facilitates adjustment when assembling the focus detection optical system. shall be.

[Means to solve the problem]

The focus advancement device according to the present invention focuses a light beam that has passed through different areas of the exit pupil of a photographic lens on a photoelectric conversion element by a secondary imaging optical system via an aperture diaphragm, and forms a pair of object images on a photoelectric conversion element. In a phase-difference focus detection device that detects the relative positional relationship between a pair of object images on a photoelectric conversion element, the secondary imaging optical system consists of two or more lenses arranged behind an aperture diaphragm. It is characterized in that it is constituted by a lens having a positive refractive power, and that at least one of the lens surfaces of the lens is an aspherical surface.

[For production]

According to the above configuration, the secondary imaging optical system is configured by a lens system including two or more lenses having positive refractive power and having at least one aspherical surface, which are arranged behind the aperture stop. As a result, it is now possible to omit the second lens, which was an obstacle to good correction of aberrations in both the pupil system and the visual field system, as in the conventional example. Therefore, aberrations in the pupil system can be sufficiently corrected with a condenser lens, and at the same time,
The aberrations of the viewing system can be sufficiently corrected by the above-mentioned lens with positive refractive power placed behind the aperture stop, and there is no need to install many secondary imaging optical systems in parallel as in the conventional example.
Any pair of secondary images can be formed on the photoelectric conversion element over a wide viewing range of the object, and high focus detection accuracy and imaging performance can be obtained.

〔Example〕

Hereinafter, the present invention will be described in detail based on the illustrated embodiment, with the same reference numerals assigned to the same members as in the above-mentioned conventional example.

FIG. 1 shows a diagram of the principle of the present invention, which will be described as a first embodiment (a first numerical example to be described later). Of the focus detection optical system, only the imaging optical system after the field stop is shown in the figure. This optical system includes a field stop 23 that has a wide field of view (for example, rectangular) and one aperture 23a, a single condenser lens 24 that mainly transmits a pupil image, and a condenser lens. an aperture diaphragm 25 formed with a pair of symmetric apertures 25a and 25b having aperture centers eccentric by δ with respect to the main optical axis of the condenser lens 24; It is composed of a first separator lens 26 and a second separator lens 27 that have a common eccentric optical axis and have a positive refractive power. Note that at least one of the lens surfaces of these two separator lenses 26.27 is set to be an aspherical surface, and these separator lenses 26.27
Although shown in the figure, they are each integrally molded and joined to each other, they may be constructed as separate bodies, as shown in the modified example of FIG.

Since this embodiment is configured as described above, the bundle is imaged as a primary image with a wide field of view by the field stop 23,
Then, after this second image is slightly enlarged by the condenser lens 24, the pair of apertures 25a, 25 of the aperture diaphragm 25
b, is relayed by the first separator lens 26 and the second separator lens 27, and is formed on the sensor surface of the light receiving element as a secondary image that is an inverted real image, forming two secondary images with parallax. It can be imaged.

The exit pupil image of the photographing lens is formed on an aperture stop 25 by a condenser lens 24 in the pupil system. Therefore, the main factor determining focus detection accuracy is
The plane of incidence (
F, NO) are determined by the distance between the two aperture centers of the aperture diaphragm 25. Further, the image plane illuminance on the secondary image plane, which is a major factor determining the minimum subject brightness, is determined by the aperture size of the apertures 25a and 25b of the brightness diaphragm 25.

As described above, according to this embodiment, the optical system is constructed without disposing the second lens that acts strongly on both the pupil system and the visual field system at the same time between the condenser lens 24 and the aperture diaphragm 25 as in the conventional example. Because it can be configured, it is possible to use a power arrangement that focuses on correcting aberrations in the pupil system in the visual field system. Therefore, even if the NA of the pupil system is large, various aberrations in the pupil system, mainly spherical aberration, are can be kept small and well.

Therefore, a single condenser lens 24 can be arranged without requiring a joint portion having a large step difference as in the conventional example.

Also, as described above, the first and second separator lenses 26.
27, it is possible to satisfy the imaging performance on the sensor surface of the light-receiving element 11 even if the image height of the -order image is increased to increase the field of view of the viewing system. The amount of error (hereinafter referred to as distortion) with respect to the next image interval can be reduced. Therefore, without having to install a large number of secondary imaging optical systems in parallel as in the conventional example, two secondary images can be generated over a wider viewing range than in the conventional example, that is, not only in the long side direction but also in the short side direction and diagonal direction. can be detected, and a continuous focus detection area can be obtained.

Furthermore, since the number of optical axes of the secondary imaging optical system is reduced, adjustment between the optical axes is easy, and a slit-shaped field mask is not required.

Note that the object-side lens surface of the first separator lens 26 is
It is preferable to have a convex shape in the object direction for correcting aberrations.

Also, if the imaging magnification of the secondary image with respect to the -order image is 8 lenses, then 0.8≧1βT 1≧0.05 (1
) is preferable. Here, 1β, 1 is 0.05
As the size becomes smaller, focus detection accuracy deteriorates. Also, 0.8
When 1βT + increases beyond , the focus detection accuracy becomes high (
However, on the other hand, the amount of image movement of the secondary image in the direction perpendicular to the main optical axis becomes large, which requires a large light receiving element and also causes problems such as deterioration of imaging performance in the peripheral area. occurs.

Further, a patent characterized in that the focal length of the first separator lens 26 is fl + the focal length of the second separator lens 27 is 0.2 ≦ f, /f, ≦0.9.
...It is desirable to satisfy (2). here,
If 1f1/f21 exceeds the lower limit and the power of f becomes too strong, distortion and peripheral coma aberration will worsen, which is undesirable. Furthermore, if the power of f2 becomes too strong beyond the upper limit, distortion and peripheral coma aberration will similarly worsen, which is not desirable.

FIG. 3 shows an imaging optical system of a second embodiment (second numerical example described later) of the present invention. In this embodiment, two lenses are used in place of the condenser lens 24 in the first embodiment. A condenser lens 29.30 is arranged.

However, the second condenser lens 30 when viewed from the object side
is arranged not near the aperture stop 25 but near the first imaging plane.

Thereby, the spherical aberration of the pupil system can be removed better than the single-lens condenser lens 24 without adversely affecting the visual field system, such as aberrations.

FIG. 4 shows a third embodiment (third numerical example),
In the figure, only the separator lens group that forms one secondary image is shown. In the figure, a parallel plate cover glass 32 is disposed in front of the sensor surface of the light-receiving element 11 on which a secondary image is formed, so that the sensor surface is hermetically sealed. This makes it possible to prevent dust and the like from adhering to the sensor, which is useful for reducing focus detection errors.

FIG. 5 shows a fourth embodiment (fourth numerical example),
In the cover glass 32 in the third embodiment, the front surface of the sensor surface is configured as a spherical or aspherical negative lens surface 33 whose principal optical axis and optical axis coincide and are rotationally symmetrical with respect to the optical axis. .

Thereby, when the image height of the secondary image is high, it is possible to further reduce distortion in the peripheral area of the secondary image forming surface, which is preferable. Therefore, the focus detection field of view ratio can be further increased.

Further, as a fifth embodiment, as shown in the fifth numerical example, instead of the negative lens surface 33 of the fourth embodiment, a lens whose front axis coincides with the main optical axis and is rotationally symmetrical with respect to the optical axis is used. It may be configured such that a positive power surface is arranged.

As a result, the distortion in the peripheral area of the secondary image at a high image height can be reduced as in the fourth embodiment.

FIG. 6 shows a sixth embodiment (sixth numerical example),
First separator lens 26 and second separator lens 27
The apex of each lens surface is arbitrarily decentered with respect to the principal optical axis, or the optical axis of each lens surface is tilted with respect to the principal optical axis. However, the imaging magnification of the secondary image by this optical system must be maintained within the range of equation (1) above. still,
In the figure, the y direction indicates the eccentricity direction of the top of the lens surface with respect to the principal optical axis, and the a direction indicates the inclination of the optical axis of the lens surface at an angle θ with respect to the principal optical axis.

According to this embodiment, by giving appropriate eccentricity and inclination to all lens surfaces, it is possible to control the target focus detection accuracy to the highest degree, but depending on the difference in target accuracy, at least It is also possible to provide eccentricity or inclination to one surface.

Further, as a seventh embodiment, as shown in the seventh numerical example, the front surface of the second separator lens 27 may be configured as an aspherical surface, and in this case as well, good focus detection accuracy and imaging performance can be obtained. preferable.

Next, an optical system in which the focus detection optical system according to the present invention is actually incorporated into a single-lens reflex camera will be described below as an eighth embodiment.

First, FIG. 7 shows an eighth embodiment, in which a condenser lens 34 and a half mirror 35 are placed on the optical path reflected by the quick return mirror 3, which is made of an ordinary reflecting member.
is arranged, and has a pair of apertures on the optical path reflected by the half mirror 35. A pair of separator lens groups 36 including the first and second separator lenses 26, 27, etc., and the light receiving element 11 are arranged in this order to constitute a focus detection optical system. Furthermore, a mirror 37 is disposed on the optical path transmitted by the half mirror 35, and an aperture stop 38 is placed on the optical path reflected by the mirror 37. Visual field transmission lens 39. Pupil transmission lens 20. An eyepiece lens 16 is arranged to constitute a finder optical system.

Note that the condenser lens 34 is equivalent to the above-mentioned condenser lens 24 or 29.30, and is composed of at least one positive lens having at least one aspherical surface, and has an exit pupil of the photographic lens 1. It has the role of transmitting information to the eye point EP of the finder optical system and the brightness aperture 25 of the focus detection optical system.

Since the present embodiment is configured as described above, in terms of visual field image transmission, in the finder optical system, the visual field image 11 on the condenser lens 34 by the photographing lens 1 is transferred to the half mirror 35, the mirror 37, and so on. A vertically and horizontally inverted image I2 is formed near the pupil transmission lens 20 by the visual field transmission lens 39, and the image I2 is enlarged and observed by the eyepiece lens 16 as an erect virtual image. In addition, in the focus detection optical system,
Visual field image 1. is half mirror 35, separator lens group 3
Two images with parallax due to 6 1. ,1. Closed light receiving element 1
The image is formed on 1.

Regarding pupil image transmission, in the finder optical system, the image of the exit pupil P of the photographing lens 1 is transferred to the quick return mirror 3.
．． Condenser lens 34. Nokan-Fumira 35. It is transmitted by a mirror 37 onto an aperture diaphragm 38 and then onto a field transmitting lens 39 . Pupil transmission lens 20. The light is transmitted to the eyepoint EP by the eyepiece lens 16. In addition, in the focus detection optical system, the image of the exit pupil F or the quick return mirror 3.
Condenser lens 34. The light is transmitted to the aperture diaphragm 25 by the half mirror 35.

As described above, according to this embodiment, the light flux from the photographic lens 1 is directed to either the film surface 5 or the finder optical system behind the quick return mirror 3, and the light flux directed to the finder optical system is directed to the focus detection optical system. Since the half mirror 35 that divides the system into two systems is installed, the focus detection optical system and finder optical system can be combined without having to make the quick return mirror a half mirror and install a submirror (optical path switching mirror) on the back side of the quick return mirror as in the conventional example. It becomes possible to coexist. Therefore, the focus detection field range can be freely selected without being affected by the size and shape of the sub-mirror, which largely depends on the size of the mirror box, and without having to take a long back focus of the photographing lens 1. The detection range can be expanded in the short side direction and diagonal direction of the photographic field of view.

FIG. 8 shows the optical system of the ninth embodiment, in which the visual field transmission lens 39 for vertically and horizontally inverting the image of the finder optical system is common not only to the finder optical system but also to the focus detection optical system. In order to achieve this, a half mirror 35 is arranged between the visual field transmitting lens 39 and the pupil transmitting lens 20, and furthermore, in the focus detection optical system on the optical path reflected by the half mirror 35, the pupil is placed between the half mirror 35 and the aperture diaphragm 25. It is constructed by arranging a transmission lens 40.

Since the present embodiment is configured as described above, regarding field image transmission, in the finder optical system, the field image 11 near the condenser lens 34 by the photographing lens l is transferred to the mirror 37. The visual field transmission lens 39 is formed in the vicinity of the pupil transmission lens 20 as an image I2 which is vertically and horizontally inverted by the half mirror 35, and the image I2 is enlarged and observed by the eyepiece lens 16 as an erect virtual image. In addition, in the focus detection optical system, the field image 1. is mirror 37. The visual field transmission lens 39 is formed in the vicinity of the pupil transmission lens 40 as an image I3 that is vertically and horizontally inverted by the half mirror 35, and the image I is transformed into two images B, I, and I with parallax by the separator lens group 36.
An image is formed on the light-receiving element 11 as an image.

Regarding pupil image transmission, in the finder optical system, the image of the exit pupil P of the photographing lens l is transferred to the quick return mirror 3.
．． Condenser lens 34. transmitted by a mirror 37 onto a field diaphragm 38 and then onto a field transmitting lens 39 . Pupil transmission lens 20. The light is transmitted to the eyepoint EP by the eyepiece lens 16.

In addition, in the focus detection optical system, the image of the pupil P on the aperture diaphragm 38 is transferred to the visual field transmission lens 39. The half-mirror 35° pupil transmission lens 40 transmits the image onto the next aperture stop 25 .

As described above, according to this embodiment, since the visual field transmission lens 39 is shared by both the finder optical system and the focus detection optical system, the distance from the half mirror 35 to the eye point EP and the distance from the half mirror 35 to This is preferable because the distance to the light-receiving element 11 can be shortened, and as a result, the eyepoint EP can be set at a position where the eye can be easily placed on the layout of the camera.

In addition, the 8 imaging magnifications from image ■1 to image ■4 or from image ■1 to image ■ are as follows: 0.05≦1βT 1≦0.8 (
3) is desirable. If the lower limit of this condition is exceeded, focus detection accuracy will deteriorate. If the upper limit is exceeded, the focus detection accuracy will increase, but the amount of image movement in the direction perpendicular to the optical axis will increase, which is not preferable because the light receiving element 11 will become larger and the imaging performance at the peripheral image height will deteriorate. .

FIG. 9 shows the optical system of the strategist embodiment, which includes field-of-view transmitting lenses 39. ．． 39. In addition, a mirror 41 is arranged between the visual field transmission lens 39 and the pupil transmission lens 40 in the focus detection optical system.

Since this embodiment is configured as described above, in the viewfinder optical system, the field image (1) near the condenser lens 34 by the photographing lens 1 is transmitted by the half mirror 35, the mirror 37° field transmission lens 391. A vertically and horizontally inverted image I2 is formed in the vicinity of the pupil transmission lens 20, and the image I2 is enlarged and observed by the eyepiece lens 16 as an erect virtual image. In addition, in the focus detection optical system, the field image 11 is transmitted through the half mirror 35 and the field transmission lens 3.
92. Image 1 which is vertically and horizontally reversed by the mirror 41. The image I,
is the two images I4 with parallax caused by the separator lens group 36.
．． An image is formed on the light receiving element 11 as II.

Regarding pupil image transmission, in the finder optical system, the image of the exit pupil P of the photographing lens l is transferred to the quick return mirror 3.
．． Condenser lens 34. The aperture is transmitted onto the aperture diaphragm 38 by the half mirror 35 and mirror 37, and then the field transmitting lens 39. Pupil transmission lens 20. The light is transmitted to the eyepoint EP by the eyepiece lens 16. In addition, in the focus detection optical system, the image of the pupil P on the aperture diaphragm 25 is transmitted to the visual field transmission lens 39□, the mirror 41 . The pupil transmission lens 40 transmits the image onto the next aperture diaphragm 25 .

As described above, according to this embodiment, the visual field transmitting lens 391 for the finder optical system and the visual field transmitting lens 39□ for the focus detection optical system are separate, so both visual field transmitting lenses 39. , 39□ can be set to suit each optical system, and the functions of both optical systems can be improved.

In addition, if the imaging magnification by the field of view transmission lens 39□ in the focus detection optical system is βR, then the amount of movement from image 1 to image I in the direction perpendicular to the optical axis is magnification β.

changes in proportion to. Therefore, if the reduction magnification is extremely small, images 1. The amount of defocus in the optical axis direction increases, resulting in a decrease in focus detection accuracy. In that case, the distance between the left and right apertures of the aperture stop 25 in the focus detection optical system after image I8 and the distance between the optical axes of the left and right separator lens groups 36 and 36 must be increased, and aberrations at the peripheral image height This increases the burden on the lens system regarding correction. Therefore, βR1≧0.3
...(4) is desirable.

Also, image ■, image ■, or image 1. The 8 imaging magnifications from image ■ to image ■ are 0.05≦ β7 ≦0.8 (5
) is desirable. If the lower limit of this condition is exceeded, focus detection accuracy will deteriorate. If the upper limit is exceeded, the focus detection accuracy will increase, but the amount of image movement in the direction perpendicular to the optical axis will increase, which is not preferable because the light receiving element 11 will become larger and the imaging performance at the peripheral image height will deteriorate. .

Next, numerical examples of the secondary imaging optical system will be shown.

1. Figures 1 and 2 are diagrams showing the configuration of this embodiment, respectively, and the data thereof are shown below.

r, = ■ (field stop surface) d = O r t = 21.86326 (aspheric surface) d2 = lO
n, =1.49216 v, =57.5r
, =-49,65109 d, =39.095 r, =■ (brightness stop surface) d, =0.3 r s = 3.92959 (aspherical surface) d5=1.
353 n2=1.49216 vt=57
．． 5r, = 293.39149 de=1.87 r7 = 8.95436 d, = 1.068 ns = 1.49216
v, =57.5r * = -25,59431 (aspherical surface) Aspheric coefficient 2nd surface P = -1,105345, E = -0,38495
7X 10-'F=0.105822X10-'G
=-0,545387X10-”H=0.8576x
10 5th surface P = -11,663382, E = 0.1156
03x 1O-F=0.419768X10-'G
=-0,290648Xl0-”H=0.506744
x 10' 8th surface P=-68,765305, E=0.658229xl
O-'F=0.483142X10-' G=-0,
188197Xl0-”H= 0.325557x 1
0-' The object point position is on the field aperture plane. The entrance pupil position is -120 from the first surface. The maximum object cylinder is y coordinate 12.6; 2 in the y direction Brightness diaphragm aperture radius is 0.833 Viewing system image magnification is 0.15 The amount of eccentricity in the y direction from the 5th to 8th surfaces is 2! 1. The third diagram is a diagram showing the configuration of this embodiment, and its data is shown below.

r, = 00 (Field stop surface) d = O r t = 32.65854 (Aspherical surface) dt = 8
n, =1.49216 v, =57.5r
, =-93,96524 d, =3 r , = 101.45233 d 4=8 nt = 1.49216
v2=57.5rs=-60,36185(
Aspherical surface) d, =36.34 rs=oo (brightness aperture surface) d, =0.751 r, =8.79794 (Aspherical surface) d7=1.09
2 ns = 1.49216 vr = 57.5r
s = 6.86537 d, = 0.959 r e −-24,0038 ds = 1.709 n, = 1.49216 v
, =57.5r1゜= -2,55279 (aspherical surface)
Aspheric coefficient second surface P=0.701729, E=-0,385868x
lO-'F=-0,188434xlO-', G=-
0,419535xlO-”H= 0.116914X
10-' 2 5th surface P = -42,801518, E = 0.543459xl
O-5F = -0,97198X 10-', G
= 0.211464X 10-'H=0 7th surface P=-1460,345733,E=0.174754
XIO-F=0.445846X10-”, G=-0
,132411Xl0-2H= -0,150981X
10 10th surface P = 1.056411, E = -0,
199031X 10-”F = 0.220749X
10-”, G = −0,558277x 10-
"H= 0.136432 X 10-" The object point position is on the field aperture plane.The entrance pupil position is -120 from the first surface.The maximum object tube is y-coordinate 12.6. x coordinate 8.4 Object side NA is 0.082 Brightness aperture center eccentricity is 2 in the y direction Brightness aperture aperture radius is 0.833 Field system image magnification is 0.15 Y direction eccentricity from 7th to 10th plane The amount is 2! Figure 4 shows the configuration of this embodiment, and its data is shown below.

r, = 00 (Field stop surface) d = O r 2 = 21.86316 (Aspherical surface) d2 = = 10
n, =l. 49216 v+ =57.5r
s = -49,'65109 d, = 39.095401 r4 = ■ (brightness aperture surface) d, = 0.3 r s = 2.53080 (aspherical surface) ds = 1
．． 250598 nt = 1.49216 vt
=57.5r s = 5.17841 d, =0.823 r? = 22.17629 d, = 1.005 n, = 1°49216 v
s = 57.5r, = -7,84574 (aspherical surface) d, = 2.563 r, =OO (plane) do = 1. Ont =1.49216 1/+
=57.5ro-■ (plane) Aspheric coefficient 2nd surface P =-1,105345, E =-0,384957
X 10-"F = -0,105822X 10-'
, G = -0,545387X 10-'H = 0
．． 85763 x 10 5th side P=0.319557, E=0.17X10-
2F =0.213961X 10-2. G=0
．． 147994X 1O-2H=0.45635 XI
O” 8th side P=-23,678061, E=0.376846xl
O-2F =0.295538X 10-2. G
=-0,200585X 10-”H=0.5413
99x 10 Object point position is on the field aperture plane Entrance pupil position is -120 Maximum object height is y coordinate 10.56. x coordinate 6° object side N
A is 0.08 Brightness aperture center eccentricity is 2.43 in the y direction; brightness aperture aperture radius is 0.98; visual field system image magnification is 0.15; surface eccentricity of the 5th to 8th surfaces is 2 in the y direction. Figure 5 shows the configuration of this embodiment, and its data is shown below.

r+=■ (field stop surface) 1-O r , =21.86316 (aspherical surface) cL =10
n, =1.49216 v, =57.5r
s = -49,65109 d, =39.095 r, =oo (brightness stop surface) d, =0.3 r5 = 2.60057 (aspherical surface) ds =1.5'17 n! =1.49216 v,
=57.5rs = 13.58694 d, =0.951 r, =-14,78858 d, =1. OOnt =1.49216 1/s =5
7.5r, --7,26268 (aspherical surface) d s
= 2.579 n 4 = 1.49216r
, = -32,52909 (aspheric surface) d, = 1.0 r, o = OO (plane) Aspheric coefficient second surface P = -1, 105345, E F = 0.105822x 10-'H = 0. 85
763
5697 x 10-' Object point position is on the field stop plane Entrance pupil position is -120 E = 0.154303X 10-2'' G =
-0,141463X 10-20.384957
Xl0-'G = -0,545387x 10-'E = 0.
498918x 1O-2G = 0.301923X
10-'ν 4 57.5 The maximum object cylinder has a y coordinate of 10.56. x coordinate 6 NA on the object side is 0.08 Brightness aperture center eccentricity is 2.43 in the y direction Brightness aperture aperture radius is 0.98 Viewing system image magnification is 0.15 y direction plane eccentricity of the 5th to 8th surfaces The amount is 2.43 Fifth numerical example rl-oo (field stop surface) d 20r 2 = 21. ．． 86316 (Aspherical surface) d2=1
0 n, =1.49216 v, =57,5
r s = -49,65109 d, = 39.095 r4-ω (brightness stop surface) d, = 0.303 rs = 3.88929 (aspherical surface) ds = 1.3
33 n2=1.49216 vt=57.5r
, =125.68198 d, =1.864 r7 = 7.70529 d7 = 1.008 ns = 1.4
9216! /s = D1.5r, = -
53,12440 (aspherical surface) di=2.771 r e ”'334.24794 do =1 n4 =1.49216
vt = 57.5r1゜-〇〇 (plane) Aspheric coefficient 2nd surface P = -1,105345, E = -0,3849
5X 1O-5F=0.105822X10-', G
=-0,545387Xl0-'H=0.85763
Xl0-12 5th surface P --5,356146, E =0.211265x
1O-2F=0.448218xlO-2, G=-0
,259659Xl0-”H=0.506744X
10-” 8th side P = -43,996656, E = 0.6510
33 x 10-”F=0.859544xlO-”,
G=0.13603 xlO−'H= −0,558
058x 10 Object point position is on the field aperture plane Entrance pupil position is -120 from the first surface Maximum object cylinder is y-coordinate 10.56. x coordinate 6 object side NA is 0.082 brightness aperture center eccentricity is 2.43 brightness aperture aperture radius is 1.31 field system image magnification is 0.15 y direction eccentricity from 5th to 8th surface The amount is 2.43 Sixth Numerical Example FIG. 6 is a diagram showing the configuration of this embodiment, and its data is shown below.

rl”■ (field stop surface) d1=O r , =21.86316 (aspherical surface) cL =10
n, =1.49216 v, =57.5r
s = -49,65109 d, =39. -095 rt=■ (brightness aperture surface) d, =0.305 r5=4.04289 (aspherical surface) ds ””2.101 n2=1.49216 ν*
=57.5ra = 60.65514 d6 =2.043 r, = 4.77161 d7=2,046 ns = 1.4921
6 v s =57.5r, =24.656
98 (Aspherical surface) d, =, 1.682 r, = -9055,57102 (Aspherical surface) d,
=1. On+ =1.49216v, =57.5
r1o-oo (plane) Aspheric coefficient second surface P = -1,105345, E = -0,3849
57X 10-'F=0.105822xlO-'
G=-0,545387xlO-'H=0.8576
3 x 10 5th surface P=-0,251284, E=-0,103594Xl
0-”F=-0,239439Xl0-2.G=-0
, 177898Xl0-”H= 0.471666X
to”” 8th surface Pm2O3, 833861E=0.790122X10
-2F=0.575889X10-', G=-0,
918832Xl0-'H=0.913202x 10
-S 9th surface P = 3510304.44951, E = -0,
988514X 10-”F=-0,14145X10
-, G=0.690170X10-'H=0.
150048 11th surface 2.605 Object point position is on the field stop plane Field system image magnification is 0.15 Entrance pupil position is -120 from the 1st surface Maximum object height is 13.4 in the X direction Object side NA is 0.08 Brightness The eccentricity of the center of the aperture is 2.43 in the y direction. The radius of the aperture aperture is 0.98. aspherical surface) d 2 = l
On l=1.49216 v 1=57.5r s
"-49,65109 d s = 39.095 r4 = ■ (brightness stop surface) d, = 0.3 rs "2.56822 (aspherical surface) d s = 1.
291 n 2 = 1.49216 v t =57
．． 5r s = 5.28922 d, = 1.105 ry = 5.83352 (aspherical surface) d, = 1.6
38 ns =1.49216 J/, =57.
5rs = -30,33058 dl =2.178 r e = -10,68439 (aspherical surface) d * =
1. On + = 1.49216 v 4 = 5
7.5r1゜=Cx3 (plane) Aspheric coefficient second surface P = -1,105345, E = -0,3849
57X 10-'F=O, L05822X10-@G=
-0,545387X10-'H= 0.85763
X 10 5th side P=0.592941 E=0.464293X1
0-2F=0.672586X10-”G=-0,
308043X10-2H=0.127078X
10-” 7th side P = 1.586963 E = -0,95
5708x 10-”F=-0,205166X10-
! G=0.491314X10-'H=-0,2473
02X 10-” 9th side P = 2.348081 E = 0.324
787 x 10-'F=0.364604XlO-'
G=-0,647883X10-'H=0.21
5411 2.43 Brightness diaphragm aperture radius is 0.98 Field system image magnification is 0.15 Y direction eccentricity from 5th to 8th surface is 2.43 However, rllrz+ ... in each of the above examples The radius of curvature of the lens surface, dl+d2+ ... is the distance between each lens surface, n
+112+... is the refractive index of each lens, and C2. C2
．． ... is the Atsube number of each lens.

Further, the aspherical shape in each of the above embodiments is expressed by the following formula using the aspherical coefficients described above. However, the coordinate in the optical axis direction is X, and the coordinate in the direction perpendicular to the optical axis is Y.

Here, C is the curvature (=1/r) at the apex of the aspherical surface.

〔Effect of the invention〕

As described above, in the focus detection device according to the present invention, the secondary imaging optical system is composed of two or more lenses with positive refractive power, and at least one of the lens surfaces is made aspheric, so that the focus detection device The detection range can be expanded not only in the long side direction within the photographic field of view, but also in the short side direction, diagonal direction, etc., and a continuous focus detection area can be obtained, while improving focus detection accuracy and pupil transmission. The imaging performance of the system can be maintained at a high level.

Further, optical adjustment during assembly is easy.

[Brief explanation of the drawing]

1 to 9 show each embodiment of the focus detection device according to the present invention, FIG. 1 is a sectional view of the main part of the focus detection optical system showing the first embodiment, and FIG. FIG. 3 is a perspective view of the main parts of the focus detection optical system showing a modification of the embodiment, FIG. 3 is a perspective view of the main parts of the focus detection optical system showing the second embodiment, and FIG. 4 is a separator lens group showing the third embodiment. , FIG. 5 is a view similar to FIG. 4 showing the fourth embodiment, FIG. 6 is a view similar to FIG. 4 showing the sixth embodiment, FIGS. 7, 8, and 9. The figures are schematic cross-sectional views showing the eighth, ninth and strategist embodiments as imaging optical systems, respectively. Figures 1O, 11 and 12 are diagrams showing optical systems of conventional examples and optical systems of other conventional examples, respectively. FIG. 13 is a cross-sectional view of the main part of the secondary imaging optical system of the optical system shown in FIG. 12. l...Photographing lens, 9,25...Brightness aperture,
11... Light receiving element, 24.29.30... Condenser lens, 26, 27.36... Condenser lens. Figure 1-5 Figure O Figure 6 Off Figure O Figure 8 Figure 11 Procedure auxiliary device (self-produced) 1, 1991, Patent Application No. 2-108195 Focus detection device 4, Address: 5, Shinbashi, Minato-ku, Tokyo 105 19 Figure 12Figure 13
Corrected to 60-32012J. (2) "Correct the incident plane J to r incidence angle 1" on page 16, line 14. (3) Correct rG=0.147994Xlo-'J on page 36, line 10 to rG=-0,1
Corrected to 47994X10-21. (4) Delete rn4=1.49216 ci4=57.5J on the second line of page 38. (5) rds on the 4th line of the same page = 1. rn after O.J.
Insert 4=1.49216 1/4=575J. (6) Same page, line 177, rG=0.301923X10-'J, rG=-0,3
01923X 10-'J,! -Correct. (7) "G=0.13603x1m'" on page 40, line 18 is corrected to rG=-0,13603x 10-'1. rF=-0, 239439x l O-2'' on page 42, line 16, fF=o
, 239439xlO-'1.

Claims (1)

[Claims] The light beams that have passed through different areas of the exit pupil of the photographic lens are imaged as a pair of object images on the photoelectric conversion element by the secondary imaging optical system via the aperture diaphragm, and the pair of object images on the photoelectric conversion element are formed. In a phase difference type focus detection device configured to detect the relative positional relationship of images, the secondary imaging optical system has two or more lenses with positive refractive power arranged behind an aperture diaphragm. A focus detection device comprising a lens, and at least one lens surface of the lens is made an aspherical surface.