JPH0688938A - Focus detector - Google Patents

Abstract

PURPOSE:To keep the optical performance of an object image (secondary image) formed by a secondary image forming lens excellent and to detect a focus with high accuracy by making the optical axis of the secondary image forming lens for a visual field region out of the axis of an objective lens non-parallel. CONSTITUTION:Among plural pairs of secondary image forming lenses constituting a secondary optical system 45, the surfaces 40, 41 on the light exit side of secondary image forming lenses 46-2a, 46-2b, 46-3a, 46-3b corresponding to a peripheral visual field area out of the optical axis of an objective lens are composed of a plane inclined to the optical axis 39 of the secondary image forming system corresponding to the optical axis of the objective lens. Thus, the angles alpha, beta expanded between the central beams 43-2a, 43-2b, 43-3a, 43-3b of the respective beams 42-2a. 42-2b, 42-3a, 42-3b before and after refraction at the planes 40, 41 and the perpendicular lines 44-1, 44-2 of the oblique planes 40, 41 are made small. Consequently, aberrations generated at the light exit planes 40, 41 are suppressed to be small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus detecting apparatus suitable for a photographic camera, a video camera, etc. Suitable for detecting the focus state of the objective lens for a plurality of areas in the photographing range by forming a light quantity distribution regarding an image (object image) and obtaining the relative positional relationship of these plurality of light quantity distributions. The present invention relates to a simple focus detection device.

[0002]

2. Description of the Related Art Conventionally, there is a so-called image shift method as a light-receiving type focus detection method that uses a light beam that has passed through an objective lens. This image shift method is disclosed, for example, in JP-A-59-1.
It is proposed in Japanese Patent Laid-Open No. 07311 and Japanese Patent Laid-Open No. 59-107313.

FIG. 10 is a schematic diagram of an optical system of a conventional focus detection device using an image shift method.

In the figure, reference numeral 61 is an objective lens, and 62 is a field mask, which is arranged in the vicinity of the planned image forming plane of the objective lens 61. 63 is a field lens, which is arranged in the vicinity of the planned image plane. A secondary optical system 64 is composed of two lenses 64-1 and 64-2 arranged symmetrically with respect to the optical axis of the objective lens 61. Reference numeral 65 is a light receiving means, and two light receiving element rows 65- are arranged behind the two lenses 64-1 and 64-2 so as to correspond to the two lenses 64-1 and 64-2.
1 and 65-2. Reference numeral 66 denotes a diaphragm having two openings 66-1 and 66-2 arranged in front of the two lenses 64-1 and 64-2.
67 is an exit pupil of the objective lens 61, and is composed of two divided regions 67-1 and 67-2.

The field lens 63 has an opening 66-
1 and 66-2 have an action of forming an image on the areas 67-1 and 67-2 of the exit pupil 67, and each area 67-1 and 67-2
The light fluxes transmitted through the light receiving elements 65-1 and 65-2 form light amount distributions on the light receiving element arrays 65-1 and 65-2, respectively.

In the focus detecting apparatus shown in FIG. 10, when the image forming point of the objective lens 61 is on the front side of the planned image forming surface,
When the light amount distributions of the object images formed on the two light receiving element arrays 65-1 and 65-2 are close to each other, and the image forming point of the objective lens 61 is on the rear side of the planned image forming surface. Indicates that the light amount distributions formed on the two light receiving element arrays 65-1 and 65-2 are separated from each other.
Moreover, since the deviation amount of the light amount distribution formed on each of the two light receiving element arrays 65-1 and 65-2 has a certain functional relationship with the defocus amount of the objective lens 61, the deviation amount can be calculated by an appropriate calculation means. When calculated, the direction and amount of defocus of the objective lens 61 can be detected.

The focus detection device shown in FIG. 10 measures the distance to an object present in the approximate center of the object range photographed by the objective lens.

On the other hand, the present applicant has previously proposed in Japanese Patent Application No. 62-279835 a focus detection device capable of detecting a focus at a distance measuring point other than the center of the photographing range.

FIG. 11 is a schematic diagram of an optical system of a focus detection device for a plurality of distance measuring points proposed in Japanese Patent Application No. 62-279835. In the figure, 71 is a field mask, 72 is a field lens, 73 is a diaphragm having two openings 73-1 and 73-2, 74 is a secondary optical system composed of two lenses 74-1 and 74-2, and 75 is Each sensor is shown. The objective lens 61 shown in FIG. 10 is omitted.

In the figure, the visual field mask 71 has a plurality of openings 71a to 71e corresponding to a plurality of visual fields to be measured, and the light flux regulated by the visual field mask 71 is generated by the secondary optical system 74. Plural pairs of sensor rows 75a1 and 75a2, 75b1 so as to receive plural pairs of light amount distributions to be formed.
And 75b2, 75c1 and 75c2, 75d1 and 75d
2, and 75e1 and 75e2 are provided as the sensor 75.

In the figure, distance measurement is performed in a total of five areas, namely, the central portion of the photographing screen and the four portions on both sides thereof. It is very important that the focus detection can be performed in a plurality of areas in the shooting screen with such a simple configuration when applied to a camera.

In the focus detecting apparatus shown in FIG. 11, since the two light quantity distributions on the sensor relatively move in the vertical direction depending on the focus state of the objective lens, the light quantity distribution changes in this direction. It is possible to measure the distance only to the object, and the distance is measured to the object whose light quantity distribution changes only in the direction perpendicular to this, such as a black and white edge pattern with the vertical line as the boundary. I can't.

For this reason, the present applicant has filed Japanese Patent Application No. 63-2749.
With No. 40, it is possible to measure the distance even for an object in which the light amount distribution changes vertically or horizontally in the vicinity of the center of the shooting range, and also at a plurality of points other than near the center of the shooting range. A focus detection device that can measure the distance is proposed.

FIG. 12 is a schematic view of a main part of a focus detection device proposed in Japanese Patent Application No. 63-274940.

In the figure, reference numeral 31 denotes a field mask which intersects substantially the center of the photographing screen by an objective lens (photographing lens) not shown, and has, for example, a cross-shaped opening 31-1 and vertically long openings on both sides. It has 31-2 and 31-3. A field lens 32 corresponds to the three openings 31-1, 31-2, 31-3 of the visual field mask 31 and has three regions 32-1, 32-2, 32-- having predetermined optical characteristics.
It consists of three. Reference numeral 33 denotes a diaphragm, and the central portion has a pair of upper, lower, left, and right pairs, for a total of four openings 33-1a and 33-1.
b, 33-1c, 33-1d, and the left and right peripheral portions are provided with a pair of two openings 33-2a, 33-2b and openings 33-3a, 33-3b, respectively.

Each region 32- of the field lens 32
1, 32-2, 32-3 have the function of forming images of the apertures 33-1, 33-2, 33-3, which form a pair with the diaphragm 33, in the vicinity of the exit pupil of the taking lens (not shown). There is. Three
A secondary optical system 4 has four pairs of secondary imaging lenses as a whole.

That is, eight secondary imaging lenses 3 as a whole
4-1a, 34-1b, 34-1c, 34-1d, 34
-2a, 34-2b, 34-3a, 34-3b, and is arranged behind the aperture 33 in correspondence with each aperture.

A light receiving element array (sensor) 35 has four pairs of sensor arrays as a whole. That is, 8 as a whole
One sensor row 35-1a, 35-1b, 35-1c, 3
5-1d, 35-2a, 35-2b, 35-3a, 35
-3b, and is arranged so as to receive the image corresponding to the secondary imaging lens.

FIG. 13 is an explanatory view showing an image area formed on the surface of the sensor 35 of FIG. Area 36-1a, 3
Reference numerals 6-1b, 36-1c, and 36-1d denote image areas of the central aperture 31-1 of the field mask 31, and the light flux transmitted through the central portion 32-1 of the field lens 32 has the aperture 33-1a of the diaphragm 33. , 33-1b, 33-1c, 33-1d, and then the secondary imaging lens 34-1a behind it,
The sensor 3 by 34-1b, 34-1c, 34-1d
The respective states formed on the five surfaces are shown.

Reference numerals 36-2a and 36-2b are image areas of the opening 31-2 around the field mask 31, and the light flux transmitted through the peripheral portion 32-2 of the field lens 32 is the diaphragm 3.
After being regulated by the opening portions 33-2a and 33-2b of No. 3, the secondary imaging lenses 34-2a and 34-2 on the rear side thereof are regulated.
The state formed on the sensor 35 by b is shown.

Similarly, reference numerals 36-3a and 36-3b denote image areas of the opening 31-3 around the field mask 31, and the light flux transmitted through the peripheral 32-3 of the field lens 32 is the opening 33 of the diaphragm 33. -3a, 33-3b, the secondary imaging lenses 34-3a, 34-
Image regions formed on the surface of the sensor 35 by 3b are shown.

The distance measuring principle of the focus detection device shown in FIG. 12 is to detect the relative position of the image in the direction of the pair of sensors, as in the conventional case.

By adopting the configuration described above, for an object in which the light amount distribution changes only in one direction up and down or left and right near the center of the range photographed or observed by the objective lens (not shown). Even if the distance measurement is possible, the opening 31- around the field mask 31 other than the center
It is also possible to measure the distance to an object located at a position corresponding to 2, 31-3.

[0024]

In the focus detection apparatus shown in FIG. 12, distance measurement is possible even for an object in a more peripheral area within a range photographed or observed by an objective lens (photographing lens). In order to achieve this, it is necessary to provide openings 31-2 and 31-3 around the field mask 31 and field lenses 32-2 and 32-3 corresponding to the openings more near the periphery.

Even in such a case, projected images 36-2a, 36-2b, 36-3 on the sensor 35 with respect to the openings 31-2, 31-3 around the field mask 31 shown in FIG.
a and 36-3b are openings 31-1 at the center of the visual field mask 31.
Same projected images 36-1a, 36-1b, 36-1c, 36
The aperture 33 of the diaphragm 33 corresponding to the aperture of the field mask 31 and the field lens 32 is formed so as to be formed as close to the center as possible within a range that does not overlap with -1d.
-2a, 33-2b, 33-3a, 33-3b and secondary imaging lenses 34-2a, 34-2b, 34-3a, 34.
By setting -3b, it is possible to prevent the sensor 35 from becoming large and the resulting increase in cost.

However, when the field of view is expanded to the periphery by this method, it becomes very difficult to maintain the optical performance of the secondary imaging lens. FIG. 14 is a plan view of a main part when the focus detection system of FIG. 12 is viewed from above, and shows only the light flux relating to the peripheral visual field. As shown in the figure, the central ray of the light flux from the apertures 31-2 and 31-3 around the visual field mask 31 along with the expansion of the distance measuring visual field to the periphery (for example, the ray passing through the area centroid of each aperture of the diaphragm 33). 37-2a, 37-2b, 37-3a, 37-3b
, Corresponding secondary imaging lenses 34-2a, 34-2b,
34-3a, 34-3b incident angle θ _i or 2
The angle θ ₀ emitted from the secondary imaging lens increases, and the imaging performance of the secondary imaging lens rapidly deteriorates.

In particular, when the secondary imaging lens is composed of a convex plano lens or a plano-convex lens, astigmatism generated on the flat surface side becomes large, and image points A, A of the light beam in the drawing of FIG. 14 'and the image forming points B, B'of the light flux in the plane orthogonal to FIG.

FIG. 15 shows a spot diagram formed at the point B on the sensor 35 at this time. Although it is small in the sensor row direction (horizontal direction), it is orthogonal to this (vertical direction). ) Has spread widely.
Originally, the sensor only needs to detect a primary secondary image in the column direction, and it seems that there is no problem even with the spot shape as shown in FIG. 15, but in such an image-forming state, the light incident on the sensor 35 is In order to set the field mask 31 that does not block the light, it is necessary to considerably widen the width direction of the openings 31-2 and 31-3, and the original function of the field mask 31 is to prevent unnecessary light from entering. It will not be fully exerted. Furthermore, when there is such a large astigmatism, the image formation point moves in the optical axis direction depending on the wavelength of light, so the direction in which the spot diagram spreads greatly changes depending on the wavelength of light, and focus detection accuracy depends on the color of the subject. The problem is that the value will decrease.

The above problems are not limited to the case of enlarging the area in which the distance can be measured, but the total lens length of the focus detection system is shortened.
This also occurs when the distance between the field mask 31 or the field lens 32 and the diaphragm 33 is shortened in order to reduce the size of the entire apparatus.

According to the present invention, the optical arrangement of a plurality of pairs of secondary imaging lenses of the secondary optical system for enabling distance measurement in a plurality of areas in the photographing range is appropriately set to make the secondary. An object of the present invention is to provide a focus detection device capable of maintaining a good optical performance of a subject image (secondary image) formed by an imaging lens and enabling a highly accurate focus detection device.

[0031]

A focus detection apparatus of the present invention has a focus detection system arranged on the image plane side of an objective lens, and the focus detection system is used to determine the focus state of the objective lens within a photographing range. When a plurality of areas of the objective lens are obtained, the focus detection system uses a light flux that has passed through different areas of the pupil of the objective lens to form a plurality of light quantity distributions related to a subject image, and the plurality of light quantities. The secondary optical system has a plurality of pairs of secondary imaging lenses, of which the field of view of the objective lens outside the optical axis is included. Is characterized in that the optical axis of the secondary imaging lens is not parallel to the optical axis of the objective lens. In addition, the secondary imaging lens is characterized by being configured by a plano-convex lens or a convex plano lens.

[0032]

1 is a schematic view of a main part of an optical system according to a first embodiment of the present invention, FIG. 2 is a schematic view of the focus detection system of FIG. 1 when viewed from above, and FIG. 3 is a partial explanation of FIG. FIG. 4 and FIG. 4 are schematic views of main parts when the focus detection device of the present invention of FIG. 1 is applied to a single-lens reflex camera.

In the present embodiment, a plurality of pairs of secondary image forming lenses (46-) forming a secondary optical system 45 for performing so-called multi-point distance detection, which performs focus detection for a plurality of areas in the photographing range. 1a and 46-1b, 46-1c and 46-1d, 46-2a and 4
6-2b, 46-3a and 46-3b)
Next imaging lens (46-2a, 46-2b, 46-3a,
46-3b) is different from that of the secondary optical system 34 of the conventional focus detection device shown in FIG.

That is, as shown in FIGS. 1, 2 and 3, in this embodiment, the objective lens 81-1 of the secondary imaging lens 45 is used.
Secondary imaging lens 46 corresponding to the peripheral visual field outside the optical axis of
-2a, 46-2b, 46-3a, 46-3b on the exit side 40, 41 corresponds to the central visual field including the optical axis of the objective lens 81-1 or the area on the optical axis of the objective lens 81-1. It is composed of a plane inclined with respect to the optical axis 39 of the secondary image forming system. By doing so, the respective light beams 42-2a, 42-2b, 42-3 before and after refraction on the planes 40, 41
a, 42-3b central rays 43-2a, 43-2b, 4
3-4a of the surfaces 40 and 41 inclined with 3-3a and 43-3b
The angles α and β formed by 4-1 and 44-2 can be made smaller than the same angles as in the conventional case, and it becomes possible to suppress the occurrence of aberrations at the exit surfaces 40 and 41 to be small.

In the case of this embodiment, since the structure of each secondary imaging lens of the secondary optical system 45 is a convex plano lens, when the convex surface is a spherical surface, the inclination of the light beam incident on the secondary imaging lens is, so to speak. Accordingly, it is the same as tilting the secondary imaging lens.

The axis of rotation of the inclination of the emission surface is parallel to the row direction of the corresponding sensor row as is clear from the gist of the present invention, and in the case of the present embodiment, the rotation surface is the center of the emission surface of the sensor. It is the direction of the department.

Next, the respective elements of this embodiment will be described in order, though they partially overlap the respective elements of the focus detection apparatus of FIG.

In the figure, reference numeral 31 denotes a field mask, which intersects substantially the center of the photographing screen by the objective lens (photographing lens) 81-1 and has, for example, a cross-shaped opening 31-1 and vertically long openings in the peripheral portions on both sides. It has 31-2 and 31-3. Reference numeral 32 denotes a field lens, which corresponds to the three openings 31-1, 31-2, 31-3 of the field mask 31 and has three regions 32-1, 32-2, 32 having predetermined optical characteristics.
-3.

Reference numeral 33 is a diaphragm, and the center portion is inscribed in a substantially perfect circle, and one pair is provided in each of the upper, lower, left and right sides, for a total of four openings 33-1.
a, 33-1b, 33-1c, 33-1d, and the left and right peripheral portions are a pair of two openings 33-2a, 33-2.
b and openings 33-3a and 33-3b are provided, respectively.

Each area 32- of the field lens 32
1, 32-2, 32-3 have an action of forming an image of the openings 33-1, 33-2, 33-3, which form a pair of the diaphragm 33, in the vicinity of the exit pupil of the taking lens 81-1. There is. Four
A secondary optical system 5 has a plurality of pairs of secondary imaging lenses.

The plurality of secondary imaging lenses constituting the secondary optical system 45 of the present embodiment have the above-mentioned configuration, and are arranged behind the aperture 33 corresponding to the respective apertures.

A light receiving element array (sensor) 35 has four pairs of sensor arrays as a whole. That is, 8 as a whole
One sensor row 35-1a, 35-1b, 35-1c, 3
5-1d, 35-2a, 35-2b, 35-3a, 35
-3b, and is arranged so as to receive the image corresponding to the secondary imaging lens.

In this embodiment, for example, each element 31-1, 3
2-1, 33-1a, 33-1b, 46-1a, 46-
1b, 35-1a, 35-1b, the first focus detection system,
Further, each element 31-2, 32-2, 33-2a, 33-2
b, 46-2a, 46-2b, 35-2a, 35-2b
In the second focus detection system, each element 31-3, 32-32, 3
3-3a, 33-3b, 46-3a, 46-3b, 35
-3a and 35-3b form a third focus detection system.

The distance measuring principle of the focus detecting apparatus of the embodiment of the present invention shown in FIG. 1 is obtained by detecting the relative position of the image of the pair of sensors in the column direction, as in the conventional so-called image shift method. ing.

In the present embodiment, by adopting the above-mentioned structure, the light amount distribution is changed only in one direction, up and down or left and right, in the vicinity of the center of the photographing range photographed or observed by the objective lens 81-1. It is possible to measure the distance to a subject, and it is also possible to measure the distance to a subject other than the center, for example, a subject that is located far away from the center on the left and right sides with high accuracy.

Next, each element when the present invention of FIG. 4 is applied to a single-lens reflex camera will be described.

In the figure, 81-1 is a photographing lens (objective lens), 81-2 is a quick return mirror, 81
-3 is a focusing screen, 81-4 is a pentaprism, 81-5 is an eyepiece lens, 81-6 is a film surface, 81-7 is a sub-mirror, which is fixed to a part of the quick return mirror 81-2. 31 is a visual field mask, and the film surface 81
It is arranged at a position substantially equivalent to -6. 81-
An infrared cut filter 8 is arranged behind the field mask 31. 32 is a field lens, 81-9, 8
Reference numerals 1-10 denote first and second total reflection mirrors, 81-11.
Is a light-shielding mask, 33 is a diaphragm, 45 is a secondary optical system, 81-
Reference numeral 12 is a third total reflection mirror. Reference numeral 35 is a light receiving element array (sensor).

In this embodiment, the visual field mask 31 and below,
The sensors up to the sensor 35 correspond to the focus detection device shown in FIG.

When the secondary optical system 45 according to the present invention is integrally formed of plastic or glass, the boundary 47 between the horizontal portion 91 and the inclined portions 40 and 41 of the secondary optical system 45 is generally defined. It is desirable that 48 is continuous as shown in FIGS. However, a step is provided at the boundary between the center and the peripheral part for the purpose of relatively adjusting the optical path length and the imaging magnification of the entire focus detection system and adjusting the thickness of the inclined part of the secondary optical system 45. The shape shown in FIGS. 5 and 6 is also possible. Furthermore, in order to adjust the optical path length and the magnification, the radii of curvature of the respective secondary imaging lenses of the secondary optical system do not necessarily have to be the same, and they may be aspherical surfaces in order to improve the imaging performance. .

FIG. 7 is a schematic view of the essential portions of Embodiment 2 of the present invention, and FIG. 8 is a schematic view of FIG. 7 viewed from above.

In this embodiment, the openings in the peripheral visual field of the visual field mask 31 are different from the first embodiment in FIG.
The number of apertures of the visual field mask 31 and the number of sensor pairs are increasing as the number becomes 1-2, 31-3, 31-4, 31-5. In the figure, sensor rows 35-4a, 35-4b, 35-
5a and 35-5b are increasing.

In this embodiment, the two peripheral visual fields 31
-2, 31-4 and a pair of secondary imaging lenses 46-2a, 46-2 for the two peripheral visual fields 31-3, 31-5, respectively.
b and the secondary imaging lenses 46-3a and 46-3b correspond to each other. Exit surface 5 corresponding to the peripheral visual field of the secondary optical system 45
Reference numerals 1 and 52 are planes inclined with respect to the optical axis 39 of the secondary imaging system.

In this embodiment, there are two peripheral visual fields, but as in the case of FIG. 2, the central ray of the light beam from the center of these visual fields and the perpendicular to the exit surfaces 51, 52 are formed. The exit surfaces 51, 5 are angled so that both angles are small.
2 is inclined with respect to the optical axis 39.

In each of Embodiments 1 and 2 described above, the secondary optical system is a plano-convex lens, but the present invention is similarly effective even when this is a plano-convex lens.

FIG. 9A is a schematic view of the essential portions of Embodiment 3 of the present invention.

In this embodiment, the secondary optical system 53 is composed of a plano-convex lens. In this embodiment, the secondary optical system 5
In the secondary surface 3 of 3, the entrance surfaces 54 and 55 of the portions corresponding to the peripheral visual field outside the optical axis of the objective lens correspond to the optical axis of the objective lens or the central visual field including the area on the optical axis of the objective lens. It is tilted with respect to the optical axis 39 of the imaging system. Further, the angle formed by the normal line of the incident surface and the central light beam of the light beam incident thereon is smaller than that in the case where there is no inclination. By doing so, it is possible to suppress the occurrence of aberrations on this incident surface to be small, as in the previous embodiments. Further, the diaphragm 56 in this embodiment is shown in FIG.
It may be bent along the inclined planes 54 and 55 as shown by the diaphragm 57 so as to be close to or in close contact with each other to facilitate holding.

In addition to the above embodiments, it is also possible to give a curvature to the inclined plane side of the secondary optical system of the above embodiments. With such a configuration, it becomes easy to correct the aberration of the secondary optical system, it becomes possible to adjust the image forming magnification, and it is possible to disperse the refracting power and prevent the respective curvatures of the lens from becoming too large. It will be possible. Also in these forms, if each lens surface is a spherical surface, the secondary optical system as a whole is equivalent to one in which the optical axis is inclined.

[0058]

According to the present invention, as described above, the optical arrangement of a plurality of pairs of secondary image forming lenses of the secondary optical system is suitable for enabling distance measurement in a plurality of areas in the photographing range. By setting to, it is possible to achieve a focus detection device that maintains good optical performance of a subject image (secondary image) formed by the secondary imaging lens and enables highly accurate focus detection.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part of a first embodiment of the present invention.

FIG. 2 is an upper plan view of FIG.

3 is an explanatory view of the secondary optical system of FIG.

FIG. 4 is a schematic view of main parts when the present invention is applied to a single-lens reflex camera.

5 is an explanatory view of another embodiment of the secondary optical system of FIG.

6 is an explanatory view of another embodiment of the secondary optical system of FIG.

FIG. 7 is a schematic view of the essential portions of Embodiment 2 of the present invention.

8 is an upper plan view of FIG. 7.

FIG. 9 is a schematic view of the essential portions of Embodiment 3 of the present invention.

FIG. 10 is a schematic view of a main part of a conventional image shift type focus detection device.

FIG. 11 is a schematic view of a main part of a conventional image shift type focus detection device.

FIG. 12 is a schematic view of a main part of a conventional image shift type focus detection device.

13 is an explanatory diagram of a part of FIG.

14 is an upper plan view of FIG.

FIG. 15 is an explanatory diagram of a spot diagram on the sensor surface of FIG.

[Explanation of symbols]

 31 Field Mask 32 Field Lens 33 Aperture 34,45 Secondary Optical System 46 Secondary Imaging Lens 35 Sensor Row 81-1 Objective Lens

Claims (3)

[Claims] 1. A focus detection system is disposed on the image plane side of an objective lens, and when the focus state of the objective lens is obtained for a plurality of regions in a photographing range by using the focus detection system, the focus detection system is used. The detection system is a secondary optical system that forms a plurality of light amount distributions for a subject image using light beams that have passed through different regions of the pupil of the objective lens, and a light receiving unit that detects the relative positional relationship between the plurality of light amount distributions. And the secondary optical system has a plurality of pairs of 2
A focus having a secondary imaging lens, of which the optical axis of the secondary imaging lens with respect to the field area outside the optical axis of the objective lens is not parallel to the optical axis of the objective lens. Detection device. 2. The focus detection device according to claim 1, wherein the secondary imaging lens is a plano-convex lens or a convex plano lens. 3. The focus according to claim 1, wherein the secondary imaging lens is composed of a plano-convex lens or a convex plano lens, and a normal line of the plane is not parallel to the optical axis of the objective lens. Detection device.