JP2015036793A - Focus detector, lens barrel, and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focus detector using two different base line lengths that performs focus detection in which the size of the focus detection sensor is well balanced with focus detection accuracy.SOLUTION: A focus detector divides a light beam passing through an imaging lens. A first focus detection optical system FD1 performs focus detection on the imaging lens, based on relative position relations between a plurality of images formed on a first detection surface part with the use of the divided light beam having a first base line length. Also, a second focus detection optical system FD2 performs focus detection on the imaging lens, based on relative position relations between a plurality of images formed on a second detection surface part with the use of the divided light beam having a second base line length different from the first base line length. Magnification or an optical path length is different for each of the imaging lenses of the first focus detection optical system FD1 and the second focus detection optical system FD2, and the size of an optical image is different for each of the focus detection optical systems.

Description

  The present invention relates to a focus detection device for an imaging optical system, and more particularly to a configuration of an imaging optical system.

  With the widespread use of digital cameras, video cameras, and the like, there is an increasing demand for higher quality and smaller size imaging devices. In particular, high accuracy and downsizing of a focus detection device that detects the focus state of an imaging lens (imaging optical system) are desired. Current focus detection devices divide the pupil of the imaging lens into a plurality of regions, and detect the focus state of the imaging lens from the relative positional relationship of the plurality of optical images formed by the light flux that has passed through each region. The Lens) phase difference detection method is mainstream. If the imaging magnification of the subject image formed on the focus detection sensor that detects the focus state information is increased, the movement of the optical image with respect to the defocus amount can be accurately detected, so that highly accurate focus detection is possible. . In addition, if the distance (baseline length) between a pair of images on the exit pupil plane of the imaging lens is long, highly accurate focus detection can be performed.

  In recent years, focus detection devices mounted on cameras perform focus detection using a long base-length light beam that operates only when a lens with a small F-number is used in order to perform focus detection with higher accuracy. There is. In this case, it is common to detect the focus with two light beams having different base lengths in the same region of the subject. For this reason, optical images with different baseline lengths are formed around one point of the focus detection sensor (generally near the center of the focus detection sensor). In a focus detection apparatus using a light beam having a long baseline length, an area where an optical image is formed is enlarged, so that the focus detection sensor is enlarged in the baseline length direction. Patent Document 1 discloses a method for efficiently arranging optical images having different base line lengths on a focus detection sensor. In Patent Document 1, as shown in FIG. 17, optical images having a short base line length are arranged in the longitudinal direction and the short direction of the focus detection sensor (see element arrays 116ah1, 116ah2, 116av1, and 116av2). Further, an optical image having a long base line length is arranged obliquely with respect to the longitudinal direction and the short direction of the focus detection sensor (see element arrangements 116as1, 16as2, 116ad1, and 116ad2). Thereby, an optical image having a long baseline length can be efficiently arranged on the focus detection sensor without increasing the size of the focus detection sensor.

JP 2011-100077 A

  The size of the optical image on the focus detection sensor is determined by the size of the aperture of the field mask near the primary imaging plane and the imaging magnification of the focus detection optical system, and the distance between the pair of optical images is determined by the baseline length. . When adjacent optical images overlap, the adjacent optical images become noise, and the focus detection accuracy decreases. Therefore, regarding the arrangement of the optical images on the focus detection sensor, it is necessary to prevent the optical images from overlapping each other in consideration of the size of the optical image and the base line length.

In the focus detection apparatus disclosed in Patent Document 1, as shown in FIG. 17, the sizes of all optical images are the same regardless of the base line length. The size of the optical image is optimized under the condition that the optical images with short baseline lengths do not overlap and the focus detection sensor does not become unnecessarily large. For this reason, the balance between the size of the focus detection sensor and the focus detection accuracy when using a light beam with a short base length is balanced. However, the size of the long baseline optical image is the same as the size of the short baseline optical image. If priority is given to reducing the size of the focus detection sensor, focus detection accuracy using a light beam having a long base length is impaired, and if priority is given to focus detection accuracy, the size of the focus detection sensor is increased.
An object of the present invention is to perform focus detection with a balance between the size of the focus detection sensor and the focus detection accuracy in a focus detection apparatus using two different baseline lengths.

  In order to solve the above-described problems, an apparatus according to the present invention is a focus detection apparatus that divides a light beam that has passed through an imaging optical system and performs focus detection of the imaging optical system using a plurality of divided light beams. First focus detection optics for performing focus detection of the imaging optical system from the relative positional relationship of a plurality of images formed on the first detection surface portion using the divided light flux having the first base length. Relative to a system and a plurality of images formed on a second detection surface portion different from the first detection surface portion using the split luminous flux having a second base length longer than the first base length A second focus detection optical system that detects the focus of the imaging optical system from a specific positional relationship, and the size of the optical image of the first focus detection optical system and the optical image of the second focus detection optical system The size of is different.

  According to the present invention, in a focus detection device using two different baseline lengths, focus detection can be performed with a balance between the size of the focus detection sensor and focus detection accuracy.

1 is a schematic configuration diagram of an imaging apparatus including a focus detection apparatus according to an embodiment of the present invention. It is a top view which shows typically the exit pupil of an imaging lens when it sees from the opening of the porous aperture_diaphragm | restriction of a focus detection apparatus. It is a schematic perspective view which shows the structural example of a focus detection apparatus. It is YZ sectional drawing of a focus detection apparatus. It is a schematic plan view which shows the visual field mask in a focus detection apparatus. It is a schematic plan view which shows the porous aperture_diaphragm | restriction in a focus detection apparatus. It is a schematic plan view which shows the re-imaging lens in a focus detection apparatus. It is XZ center sectional drawing of the re-imaging lens which concerns on 1st Embodiment of this invention. It is a schematic plan view which shows the focus detection sensor which concerns on 1st, 3rd thru | or 5th embodiment of this invention. It is XZ center sectional drawing of the re-imaging lens which concerns on 2nd Embodiment of this invention. It is a schematic plan view which shows the focus detection sensor which concerns on 2nd thru | or 5th embodiment of this invention. It is a schematic plan view which shows the focus detection sensor which concerns on 2nd Embodiment of this invention. It is a XZ side view of the focus detection sensor which concerns on 3rd Embodiment of this invention. It is XZ side view of the focus detection sensor which concerns on 4th Embodiment of this invention. It is XZ side view of the focus detection sensor which concerns on 5th Embodiment of this invention. It is a XZ side view which shows another example of the focus detection sensor which concerns on 5th Embodiment of this invention. It is a schematic plan view which shows arrangement | positioning of the optical image on the focus detection sensor in a prior art.

Embodiments of the present invention will be described with reference to the accompanying drawings.
[First Embodiment]
With reference to FIG. 1, a schematic configuration of an imaging apparatus 1 including a focus detection apparatus 100 according to a first embodiment of the present invention will be described.
The imaging device 1 includes an imaging lens 10 and a camera body. The imaging lens 10 can be attached to the camera body via a mount (not shown). The imaging device 1 is, for example, a single lens reflex camera. The interchangeable imaging lens 10 for imaging a subject includes an imaging optical system including a focus adjustment lens (not shown). In the imaging lens 10, the focus adjustment lens is driven according to the focus detection result by the focus detection apparatus 100, and the focus state is adjusted. The imaging lens 10 is held by the lens barrel LB so as to be movable in the direction of the optical axis (main optical axis OA). Note that the imaging lens 10 functions as an imaging optical system of the imaging device 1 in a state where it is mounted on the camera main body, and therefore will be treated as a component of the imaging device 1 below.

The camera body includes a main mirror 20, a finder optical system 30, a sub mirror 40, an image sensor 50, a focus detection device 100, and a control unit 80.
The main mirror 20 includes a semi-transparent half mirror or a movable mirror having a half mirror surface in part. The main mirror 20 reflects part of the light that has passed through the imaging lens 10. The reflected light is guided to the finder optical system 30 along the optical axis OA2. Part of the light that has passed through the imaging lens 10 is guided to the sub-mirror 40 along the main optical axis OA as transmitted light.
The viewfinder optical system 30 is an optical system for observing a subject, and provides the user with an observation image equivalent to the subject image. As shown in FIG. 1, the finder optical system 30 includes a focusing screen 32, a pentaprism 34, and an eyepiece lens 36.

The light from the imaging lens 10 reflected by the main mirror 20 is collected in the vicinity of the focusing screen 32. The focusing screen 32 has a mat surface and a Fresnel surface, and a finder field is formed on the surfaces. The focusing screen 32 further diffuses the subject light and emits it to the pentaprism 34. The pentaprism 34 is an optical path conversion element, reflects the light diffused by the focusing screen 32 on a plurality of surfaces, and guides it to the eyepiece lens 36. A user observes the viewfinder field formed on the focusing screen 32 by an eyepiece 36 also called an eyepiece.
The sub mirror 40 is disposed behind the main optical axis OA (on the image sensor 50 side) with respect to the main mirror 20. The sub mirror 40 reflects the light transmitted through the main mirror 20 and guides it to the focus detection apparatus 100 along the optical axis OA1. The optical axis OA1 is an optical axis deflected from the main optical axis OA by the sub mirror 40. The sub mirror 40 can be inserted into and removed from the imaging optical path on the main optical axis OA, and is disposed at a predetermined position on the imaging optical path during finder observation. Further, the sub mirror 40 is retracted out of the imaging optical path during imaging.

The image sensor 50 includes a pixel group in which a plurality of pixels are regularly arranged. The imaging element 50 receives a subject image formed on the imaging surface (pixel array surface) by the imaging lens 10 and converts it into an image signal. For example, the image pickup device 50 is configured by an area (two-dimensional) sensor of a type that photoelectrically converts a received light image for each pixel, accumulates charges corresponding to the amount of received light, and reads out the charges. The imaging device 50 is, for example, a CMOS (complementary metal oxide semiconductor) image sensor or a CCD (charge coupled device) image sensor. The output signal of the image sensor 50 is subjected to predetermined processing by an image processing circuit (not shown) and converted to recording image data. Thereafter, the recording image data is recorded on a recording medium such as a semiconductor memory, an optical disk, and a magnetic tape (not shown).
The phase difference detection type focus detection apparatus 100 detects the focus state of the imaging lens 10. The focus detection apparatus 100 divides the light that passes through the imaging lens 10 and is reflected by the sub mirror 40. A plurality of pairs of images are formed by the divided light fluxes, and the focus detection apparatus 100 determines the focus state of the imaging lens 10 according to the relative positional relationship of the images based on signals obtained by photoelectrically converting each pair of images. To detect.

  Next, the configuration of the focus detection apparatus 100 will be described with reference to FIGS. FIG. 2 is a plan view schematically showing the exit pupil of the imaging lens 10 when viewed from the opening of the aperture stop 114 of the focus detection apparatus 100 shown in FIGS. 3 and 4. 3 and 4 are detailed views of the focus detection apparatus 100. FIG. With respect to the X-axis, Y-axis, and Z-axis directions shown in FIG. 3, the Z-axis direction is the same as the optical axis OA1. The direction of the X axis orthogonal to the Z axis is the first direction (short direction) of the opening 110a of the field mask 110. The Y axis is perpendicular to the Z axis and the X axis, and the Y axis direction is the second direction (longitudinal direction) of the opening 110a of the field mask 110.

The first focus detection optical system according to the present invention performs focus detection by a light beam that has passed through the exit pupils 10a, 10c, 10e, and 10g of the imaging lens 10 disposed on a circle 101 (FIG. 2) concentric with the imaging lens 10. Do. The baseline length 10ae is the distance between the centers of gravity of the exit pupil 10a and the exit pupil 10e, and the baseline length 10cg is the distance between the centers of gravity of the exit pupil 10c and the exit pupil 10g. The baseline lengths 10ae and 10cg are the first baseline lengths in the present invention.
In addition, the second focus detection optical system according to the present invention performs focus detection using the light flux that has passed through the exit pupils 10b, 10d, 10f, and 10h disposed on the circle 102 (FIG. 2) concentric with the imaging lens 10. The baseline length 10bf is the distance between the centers of gravity of the exit pupil 10b and the exit pupil 10f, and the baseline length 10dh is the distance between the centers of gravity of the exit pupil 10d and the exit pupil 10h. The baseline lengths 10bf and 10dh are the second baseline lengths in the present invention.

The focus detection apparatus 100 shown in FIGS. 3 and 4 includes a field mask 110, a field lens 111, a filter 113, a porous aperture 114, a re-imaging lens 115, and a re-imaging lens 115 along the optical axis OA1 from the side close to the main optical axis OA. The focus detection sensor 116 is included in order. The re-imaging lens 115 is a lens group including a plurality of imaging lenses. The imaging device of the present invention is a focus detection sensor 116.
FIG. 5 shows the field mask 110. The field mask 110 has a rectangular opening 110a at the center for restricting the light beam that has passed through the imaging lens 10. The field mask 110 is disposed in the vicinity of the planned imaging plane of the imaging lens 10.

  The field lens 111 is disposed on the downstream side (focus detection sensor 116 side) of the optical axis OA1 with respect to the field mask 110, and includes a lens unit 111a having an optical action. The lens part 111 a is a part corresponding to the opening 110 a of the field mask 110 in the field lens 111. The filter 113 blocks light having a longer wavelength than near infrared light. The filter 113 is adapted to detect the focus of the imaging lens 10 whose aberration is corrected with respect to visible light, and prevents unnecessary infrared light from entering the focus detection sensor 116 described later.

The porous diaphragm 114 is formed of a thin plate and is disposed adjacent to the filter 113 on the downstream side of the optical axis OA1. The configuration of the porous aperture 114 is shown in FIG. The porous aperture 114 has a plurality of openings shown below at the center thereof.
A pair of openings 114av1 and 114av2: arranged in the longitudinal direction (Y direction) of the opening 110a.
A pair of openings 114ah1 and 114ah2: arranged in the short direction (X direction) of the opening 110a.
A pair of openings 114as1 and 114as2 are arranged in a 45 ° left oblique direction.
A pair of openings 114ad1 and 114ad2: arranged in a 45 ° diagonal direction to the right.

  The openings 114av1, 114av2, 114ah1, 114ah2 are arranged so as to be inscribed in substantially the same circle. Further, the openings 114as1, 114as2, 114ad1, and 114ad2 are arranged so as to be concentric with the above-described inscribed circle and inscribed in substantially the same circle having a larger diameter. With this arrangement, the aperture 114as1, 114as2, 114ad1, and 114ad2 reach the luminous flux of the imaging lens 10 that is brighter (having a smaller F number) than the other apertures 114av1, 114av2, 114ah1, and 114ah2. The plurality of openings 114av1, 114av2, 114ah1, 114ah2, 114as1, 114as2, 114ad1, and 114ad2 of the porous aperture 114 are collectively referred to as an opening 114a. The opening 114 a is configured to be back-projected by the lens unit 111 a of the field lens 111 near the exit pupil of the imaging lens 10. Accordingly, a part of the light beam incident on the opening 110 a of the field mask 110 always reaches the opening 114 a of the porous diaphragm 114.

The re-imaging lens 115 forms a subject image formed on the planned imaging plane by the imaging lens 10 on each element array of the focus detection sensor 116 disposed downstream of the optical axis OA1. The focus detection sensor 116 has a plurality of pairs of element arrays, and a plurality of focus detection elements are arrayed in a predetermined direction as will be described later. The re-imaging lens 115 has a prism portion and a lens portion corresponding to the four pairs of openings of the porous diaphragm 114.
7A and 7B show the incident side of the re-imaging lens 115. FIG. FIG. 7C shows the exit side of the re-imaging lens 115, and attention should be paid to the fact that the left and right sides of FIGS. 7A and 7B are reversed.
The re-imaging lens 115 has, on the incident side, a lens portion 1150a (see FIG. 7A) corresponding to the opening of the porous stop 114 or a prism portion 1151a (see FIG. 7 (A)) corresponding to the opening of the porous stop 114. B) see).

The lens unit 1150a summarizes the plurality of lens units 1150av1, 1150av2, 1150ah1, 1150ah2, 1150as1, 1150as2, 1150ad1, and 1150ad2. The arrangement of the lens portions in FIG. 7A is as follows.
Lens portions 1150av1, 1150av2: arranged in the Y direction at the center of the re-imaging lens 115.
Lens portions 1150ah1, 1150ah2: arranged in the X direction at the center of the re-imaging lens 115.
Lens portions 1150as1, 1150ad2, 1150as2, and 1150ad1: Lens portions 1150av1, 1150ah1, 1150av2, and 1150ah2 are arranged in an oblique direction adjacent to each other.

The prism portion 1151a summarizes the plurality of prism portions 1151av1, 1151av2, 1151ah1, 1151ah2, 1151as1, 1151as2, 1151ad1, and 1151ad2. The arrangement of the prism portions in FIG. 7B is as follows.
Prism portions 1151av1, 1151av2: arranged in the Y direction at the center of the re-imaging lens 115.
Prism units 1151ah1, 1151ah2: arranged in the X direction at the center of the re-imaging lens 115.
Prism portions 1151as1, 1151ad2, 1151as2, and 1151ad1: The prism portions 1151av1, 1151ah1, 1151av2, and 1151ah2 are arranged in an oblique direction adjacent to each other.

  Each prism portion will be described with reference to FIG. 7B in which the incident side of the re-imaging lens 115 is a prism portion. In this case, the re-imaging lens 115 includes a pair of prism portions 1151av1 and 1151av2 arranged in the central portion in the longitudinal direction (Y direction) of the opening 110a. A pair of prism portions 1151ah1 and 1151ah2 are arranged in the short direction (X direction) of the opening 110a. The pair of prism portions 1151av1 and 1151av2 divides the light beam limited by the opening 110a in the longitudinal direction (Y direction) of the opening 110a. The pair of prism portions 1151ah1 and 1151ah2 divides the light beam limited by the opening 110a in the short direction (X direction) of the opening 110a.

  Further, the re-imaging lens 115 has a pair of prism portions 1151as1 and 1151as2 arranged in the left oblique 45 degree direction and a pair of prism parts 1151ad1 and 1151ad2 arranged in the right oblique 45 degree direction at the center. Have. The direction of 45 degrees to the left (first oblique direction) is a direction rotated 45 degrees counterclockwise with respect to the longitudinal direction of the opening 110a when viewed from the upstream side to the downstream side of the optical axis OA1. The direction of 45 degrees diagonally right (second diagonal direction) is a direction rotated 45 degrees clockwise relative to the longitudinal direction of the opening 110a when viewed from the upstream side to the downstream side of the optical axis OA1, and the optical axis OA1. This is a direction perpendicular to the left oblique 45 degree direction in a plane perpendicular to. The pair of prism portions 1151as1 and 1151as2 divides the light beam limited by the opening 110a in the direction of 45 degrees diagonally to the left. The pair of prism portions 1151ad1 and 1151ad2 divides the light beam limited by the opening 110a in a 45 ° right oblique direction. As shown in FIG. 7A, the re-imaging lens 115 also has a lens portion 1150a on the incident side, and plays the same role as described above in the focus detection apparatus 100.

On the other hand, as shown in FIG. 7C, the re-imaging lens 115 has a lens portion 1152a corresponding to the prism portion (see FIG. 7B) and the lens portion (see FIG. 7A) on the exit side. Have The lens portion 1152a having a spherical shape summarizes the lens portions 1152av1, 1152av2, 1152ah1, 1152ah2, 1152as1, 1152as2, 1152ad1, and 1152ad2. The arrangement of the lens portions in FIG. 7C is as follows.
Lens portions 1152av1, 1152av2: arranged in the Y direction at the center of the re-imaging lens 115.
Lens portions 1152ah1, 1152ah2: arranged in the X direction at the center of the re-imaging lens 115.
Lens portions 1152ad1, 1152as2, 1152ad2, and 1152as1: Lens portions 1152av1, 1152ah2, 1152av2, and 1152ah1 are arranged in an oblique direction adjacent to each other.

  The pair of lens portions 1152av1 and 1152av2 is arranged in the longitudinal direction (Y direction) of the opening 110a at the center portion, and guides the luminous flux divided in that direction to the focus detection sensor 116. The pair of lens portions 1152ah1 and 1152ah2 is arranged in the short side direction (X direction) of the opening 110a at the center portion, and guides the luminous flux divided in that direction to the focus detection sensor 116. Further, when the re-imaging lens 115 is viewed from the upstream side to the downstream side of the optical axis OA1, the pair of lens portions 1152as1 and 1152as2 arranged in the 45 ° diagonal direction are divided in the 45 ° diagonal direction. The light beam is guided to the focus detection sensor 116. Further, the pair of lens portions 1152ad1 and 1152ad2 arranged in the 45 ° right oblique direction guides the light beam divided in the 45 ° right oblique direction to the focus detection sensor 116.

A first focus detection optical system (hereinafter referred to as a first detection system) FD1 performs focus detection using light beams that respectively pass through exit pupils 10a, 10c, 10e, and 10g (see FIG. 2) of the imaging lens 10. The first detection system FD1 is composed of the following elements, for example.
A field mask 110, a field lens 111, and a filter 113.
-Openings 114av1, 114av2, 114ah1, 114ah2 of the porous aperture 114.
Prism portions 1151av1, 1151av2, 1151ah1, 1151ah2 and lens portions 1152av1, 1152av2, 1152ah1, 1152ah2 of the re-imaging lens 115.
A focus detection sensor 116;
That is, the first detection system FD1 has a first base line length, and performs focus detection using a light beam divided in the short side direction (X direction) and the long side direction (Y direction) of the opening 110a.

A second focus detection optical system (hereinafter referred to as a second detection system) FD2 performs focus detection using light beams that respectively pass through the exit pupils 10b, 10d, 10f, and 10h (see FIG. 2) of the imaging lens 10. The second detection system FD2 includes, for example, the following elements.
A field mask 110, a field lens 111, and a filter 113.
Openings 114as1, 114as2, 114ad1, 114ad2 of the porous aperture 114.
Prism portions 1151as1, 1151as2, 1151ad1, 1151ad2 and lens portions 1152as1, 1152as2, 1152ad1, 1152ad2 of the re-imaging lens 115.
A focus detection sensor 116;
That is, the second detection system FD2 has a second base line length and performs focus detection using a light beam divided in a direction rotated by 45 degrees with respect to the longitudinal direction of the opening 110a.
The first detection system FD1 and the second detection system FD2 form optical images of the same region of the subject on the focus detection sensor 116 using pupils having different division directions. That is, the first detection system FD1 and the second detection system FD2 perform focus detection on the same area of the subject.

Next, the focus detection operation of the focus detection apparatus 100 will be described. However, reference numerals 1 and 2 at the end of the reference numbers in FIG. 7 represent elements for forming two paired object images in the phase difference detection type focus detection apparatus.
The light beam that has passed through the opening 110 a of the field mask 110 (the light beam limited by the opening 110 a) passes through the lens portion 111 a of the field lens 111 and enters the porous aperture 114 via the filter 113. Next, a light beam that has passed through the opening 110a of the field mask 110 (light beam limited by the opening 110a) passes through each prism portion and lens portion of the re-imaging lens 115 positioned downstream of the optical axis OA1 with respect to the aperture stop 114. Is guided. The opening 110a of the field mask 110 is provided for a focus detection optical system having the lens portion 111a of the field lens 111, the opening 114a of the porous aperture 114, the prism portion 1151a of the re-imaging lens 115, and the lens portion 1152a. .

The light beam emitted from the re-imaging lens 115 enters the focus detection sensor 116 located downstream of the optical axis OA1. On the light receiving surface of the focus detection sensor 116, four pairs (that is, eight) of secondary images are formed, each having the opening 110a of the field mask 110 as an object image (optical image).
In the present embodiment, the size of the optical image formed on the focus detection sensor 116 is different between the first detection system FD1 and the second detection system FD2. FIG. 8 is an XZ central sectional view of the re-imaging lens 115 according to this embodiment. In FIG. 8, the incident side of the re-imaging lens has a prism surface. The image-side main surface of the lens portion 1152x (x represents any one of av1, av2, ah1, ah2, as1, as2, ad1, ad2) of the re-imaging lens 115 is assumed to be 1153x.

  The image-side main surfaces 1153ad1 and 1153as1 of the re-imaging lens 115 are further away from the focus detection sensor 116 toward the subject than the image-side main surfaces 1153av1, 1153ah1, and 1153ah2. The image side main surfaces 1153ad2 and 1153as2 are further away from the focus detection sensor 116 toward the subject than the image side main surfaces 1153av1, 1153ah1, and 1153ah2. The curvature radii of the lens portions 1152as1, 1152as2, 1152ad1, 1152ad2 are larger than the curvature radii of the lens portions 1152av1, 1152av2, 1152ah1, 1152ah2.

  At this time, the imaging magnification of the second detection system FD2 is larger than the imaging magnification of the first detection system FD1. FIG. 9 shows an arrangement example of the optical image on the focus detection sensor 116 when the optical image of the second detection system FD2 is larger than the optical image of the first detection system FD1. In FIG. 9, optical images 116 av 1 to 116 ad 2 are formed by the opening 110 a of the field mask 110 when the imaging lens 10 is in focus. Optical images 116av1, 116av2, 116ah1, and 116ah2 are optical images formed by the light beams divided by the first detection system FD1. Inside the element array 117av1, 117av2, 117ah1, 117ah2 are arranged. The first detection surface portion 1161 has element arrays 117av1, 117av2, 117ah1, and 117ah2. Further, the optical images 116as1, 116as2, 116ad1, and 116ad2 are formed by the light beams divided by the second detection system FD2. Inside the element array, 117as1, 117as2, 117ad1, and 117ad2 are arranged. The second detection surface portion 1162 has element arrays 117as1, 117as2, 117ad1, and 117ad2.

  Each focus detection element (for example, a photodiode) generates a focus detection signal by photoelectrically converting the received light beam. When the configuration of the imaging optical system in the first detection system FD1 and the configuration of the imaging optical system in the second detection system FD2 are compared, the image side main surface position of the imaging lens and the imaging magnification of the optical system are different. . When the optical image becomes large, the focus detection sensor 116 can precisely detect the change in the focus position, so that the focus detection accuracy increases. If the imaging magnification of the first detection system FD1 is increased similarly to the second detection system FD2, the focus detection sensor 116 itself must be enlarged. However, as shown in FIG. 9, the imaging magnification of the second detection system FD2 is set to be relatively larger than the imaging magnification of the first detection system FD1, thereby preventing the focus detection sensor 116 from becoming large and focusing. It is possible to increase the accuracy of detection. Therefore, according to the present embodiment, it is possible to provide a focus detection apparatus in which the size of the image sensor and the focus detection accuracy are balanced.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. The focus detection apparatus according to the second embodiment has the same configuration as that of the first embodiment except for the position of the image-side main surface of the re-imaging lens 115 and the imaging magnification of the second detection system FD2. Therefore, in the following, the same components as those in the first embodiment will be used, and the detailed description thereof will be omitted by using the already used symbols, and the differences will be mainly described. The omission of such description is the same in the embodiments described later.

  FIG. 10 is an XZ central sectional view of the re-imaging lens 115 according to the second embodiment. In FIG. 10, the re-imaging lens 115 has a prism surface on the incident side. Image-side main surfaces 1153ad1, 1153ad2, 1153as1, and 1153as2 in the re-imaging lens 115 are located closer to the focus detection sensor 116 than the image-side main surfaces 1153av1, 1153av2, 1153ah1, and 1153ah2. The curvature radii of the lens portions 1152as1, 1152as2, 1152ad1, 1152ad2 are smaller than the curvature radii of the lens portions 1152av1, 1152av2, 1152ah1, 1152ah2. In this case, the imaging magnification of the second detection system FD2 is smaller than the imaging magnification of the first detection system FD1. As a result, the optical images 116as1, 116as2, 116ad1, and 116ad2 of the second detection system FD2 are smaller than the optical images 116av1, 116av2, 116ah1, and 116ah2 of the first detection system FD1.

  FIG. 11 is a schematic plan view showing the focus detection sensor 116 in a state where an optical image is formed in the present embodiment. In FIG. 11, since the size of the focus detection sensor 116 is smaller than that of the sensor shown in FIG. 9, the base line length 10bf and the base line length 10dh (see FIG. 2) cannot be made longer than in the case of FIG. However, if the base line length 10bf and the base line length 10dh are shortened without changing the imaging magnification, the optical images are overlapped by the focus detection optical systems FD2 and FD1, and the focus detection accuracy of the first detection system FD1 decreases. there is a possibility. Therefore, in the present embodiment, the optical image of the second detection system FD2 is made relatively small so that the optical image of the second detection system FD2 is formed on the focus detection sensor 116 while avoiding the overlap of the optical images. It becomes possible. Therefore, even when the size of the focus detection sensor 116 is limited, highly accurate focus detection is possible.

According to the present embodiment, the focus detection accuracy is not impaired even if the imaging device is downsized by making the optical image of the second detection system FD2 relatively smaller than the optical image of the first detection system FD1. . Therefore, it is possible to provide a focus detection device that balances the imaging device and the focus detection accuracy.
In the present embodiment, the second detection system FD2 splits the light beam in an oblique direction with respect to the first detection system FD1. Not limited to this, as shown in FIG. 12, the splitting direction of the light beam of the second detection system FD2 may be the same direction as the splitting direction of the light beam of the first detection system FD1. Thereby, the focus detection sensor 115 can be reduced in the short side direction. In this case, the optical images 116ah1 and 116ah2 in FIG. 12 are optical images by the first detection system FD1. Smaller optical images 116ah3 and 116ah4 are optical images of the second detection system FD2.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. The focus detection apparatus according to this embodiment has the same configuration as that of the first embodiment except for the position of the image-side main surface of the re-imaging lens 115, the radius of curvature of the lens unit, and the structure of the focus detection sensor 116. is there.

  FIG. 13 is an XZ side view of the focus detection sensor according to the present embodiment. The plane 1163 is a plane on which the first detection surface portion 1161 exists. The plane 1164 is a plane on which the second detection surface unit 1162 exists. The first detection surface portion 1161 and the second detection surface portion 1162 have a positional relationship parallel to each other. The step structure 117 is a step formed between the plane 1163 and the plane 1164 on the surface of the focus detection sensor 116. The optical path length of the imaging optical system in the first detection system FD1 and the optical path length of the imaging optical system in the second detection system FD2 differ depending on the step structure 117 that is the configuration on the detection surface side. The optical path length between the image side main surfaces 1153av1, 1153av2, 1153ah1, and 1153ah2 of the re-imaging lens 115 included in the first detection system FD1 and the first detection surface portion 1161 is defined as LA. Further, the optical path length between the image-side main surfaces 1153as1, 1153as2, 1153ad1, and 1153ad2 of the re-imaging lens 115 included in the second detection system FD2 and the second detection surface portion 1162 is denoted as LB. Due to the step structure 117, “LA <LB”, and the imaging magnification of the second detection system FD2 is larger than the imaging magnification of the first detection system FD1. Therefore, the optical images 116as1, 116as2, 116ad1, and 116ad2 of the second detection system FD2 are larger than the optical images 116av1, 116av2, 116ah1, and 116ah2 of the first detection system FD1. In this case, the arrangement of the optical images on the surface of the focus detection sensor 116 is as shown in FIG. When the optical image becomes large, the focus detection sensor 116 can accurately detect the fluctuation of the focus position, and thus the focus detection accuracy increases.

  When the imaging magnification of the first detection system FD1 is increased similarly to the second detection system FD2, the focus detection sensor 116 itself must be enlarged. However, as shown in FIG. 9, the imaging magnification of the second detection system FD2 is relatively larger than the imaging magnification of the first detection system FD1, thereby preventing an increase in size of the focus detection sensor 116, The focus detection accuracy can be increased. Therefore, it is possible to provide a focus detection device in which the size of the image sensor and the focus detection accuracy are balanced.

  In the step structure 117 described above, the plane 1163 is positioned closer to the re-imaging lens 115 than the plane 1164, but the plane 1164 may be a step structure positioned closer to the re-imaging lens 115 than the plane 1163. In this case, the imaging magnification of the second detection system FD2 is smaller than the imaging magnification of the first detection system FD1. As a result, the optical images 116as1, 116as2, 116ad1, and 116ad2 of the second detection system FD2 are smaller than the optical images 116av1, 116av2, 116ah1, and 116ah2 of the first detection system FD1. Thereby, the arrangement of the optical image on the surface of the focus detection sensor becomes as shown in FIG.

In FIG. 11, since the size of the focus detection sensor 116 is smaller than that of FIG. 9, the base line length 10bf and the base line length 10dh cannot be made as long as FIG. However, if the base line length 10bf and the base line length 10dh are shortened without changing the imaging magnification, the focus detection accuracy of the first detection system FD1 may be reduced due to the overlap of the optical images of the detection systems. Therefore, by reducing the optical image of the second detection system FD2, the optical image of the second detection system FD2 can be formed on the focus detection sensor 116 without overlapping the optical images. Therefore, even when the size of the focus detection sensor 116 is limited, highly accurate focus detection is possible.
As described above, by reducing the optical image by the second detection system FD2 relative to the optical image by the first detection system FD1, the focus detection accuracy is not impaired even if the image pickup device is downsized. Therefore, it is possible to provide a focus detection device in which the imaging element and the focus detection accuracy are balanced.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. The focus detection apparatus according to the present embodiment has the same configuration as that of the third embodiment except for the structure of the focus detection sensor 116.
FIG. 14 is an XZ side view of the focus detection sensor 115 according to the present embodiment. The protective film (protective layer) 118 for protecting the surface of the focus detection sensor 116 is made of, for example, resin or glass. The step structure 119 is formed on the protective film 118. In the step structure 119, the protective film thickness on the second detection surface portion 1162 is thicker than the protective film thickness on the first detection surface portion 1161. That is, the protective film thickness is selectively changed on the focus detection sensor 116. The step structure 119 can be obtained by, for example, a process of selectively laminating a resin layer by a microfabrication process or a process of selectively etching glass. In this case, the optical path length of the imaging optical system in the first detection system FD1 and the optical path length of the imaging optical system in the second detection system FD2 differ depending on the step structure 119 that is the configuration on the detection surface side. The optical path length between the image-side main surfaces 1153av1, 1153av2, 1153ah1, and 1153ah2 of the re-imaging lens 115 included in the first detection system FD1 and the first detection surface portion 1161 is LC. The optical path length between the image-side main surfaces 1153as1, 1153as2, 1153ad1, 1153ad2 of the re-imaging lens 115 included in the second detection system FD2 and the second detection surface portion 1162 is defined as LD. Due to the step structure 119, “LC <LD”, and the imaging magnification of the second detection system FD2 is larger than the imaging magnification of the first detection system FD1. Therefore, the arrangement of optical images on the surface of the focus detection sensor 116 is as shown in FIG. When the optical image becomes large, the focus detection sensor 116 can precisely detect the fluctuation of the focus position, so that the focus detection accuracy increases. By making the imaging magnification of the second detection system FD2 relatively larger than the imaging magnification of the first detection system FD1, it is possible to increase the focus detection accuracy while preventing an increase in the size of the focus detection sensor 116. It becomes possible. Therefore, it is possible to provide a focus detection device in which the size of the image sensor and the focus detection accuracy are balanced.

  In the case of the step structure 119, the protective film thickness on the second detection surface portion 1162 is thicker than the protective film thickness on the first detection surface portion 1161. However, the present invention is not limited to this, and a step structure in which the protective film thickness on the second detection surface portion 1162 is thinner than the protective film thickness on the first detection surface portion 1161 may be used. In this case, the imaging magnification of the second detection system FD2 is smaller than the imaging magnification of the first detection system FD1. As a result, the optical images 116as1, 116as2, 116ad1, and 116ad2 of the second detection system FD2 are smaller than the optical images 116av1, 116av2, 116ah1, and 116ah2 of the first detection system FD1. The arrangement of the optical image on the surface of the focus detection sensor is as shown in FIG.

In FIG. 11, since the size of the focus detection sensor 116 is smaller than that in FIG. 9, the base line length 10bf and the base line length 10dh cannot be made as long as those in FIG. However, if the base line length 10bf and the base line length 10dh are shortened without changing the imaging magnification, the focus detection accuracy of the first detection system FD1 may be reduced due to the overlap of the optical images of the detection systems. Therefore, by reducing the optical image of the second detection system FD2, the optical image of the second detection system FD2 can be formed on the focus detection sensor 116 without overlapping the optical images. Therefore, even when the size of the focus detection sensor 116 is limited, highly accurate focus detection is possible.
As described above, by reducing the optical image of the second detection system FD2 relative to the optical image of the first detection system FD1, the focus detection accuracy is not impaired even if the image sensor is downsized. Therefore, it is possible to provide a focus detection device in which the imaging element and the focus detection accuracy are balanced.

[Fifth Embodiment]
Next, a fifth embodiment of the present invention will be described. The focus detection apparatus according to the present embodiment has the same configuration as that of the third embodiment except for the structure of the focus detection sensor 116.
FIG. 15 is an XZ side view of the focus detection sensor according to the present embodiment. The focus detection sensor 116 has a step structure 117 and a protective film 118. The surface of the protective film 118 is a uniform plane. As shown in FIG. 16, the protective film 118 itself may have a step structure 119. In this case, the optical path length of the imaging optical system in the first detection system FD1 and the optical path length of the imaging optical system in the second detection system FD2 differ depending on the step structure 117 and the step structure 119 that are the configuration on the detection surface side.

  The optical path length between the image-side main surface of the re-imaging lens 115 and the first detection surface portion 1161 is denoted by LE. The optical path length between the image-side main surface of the re-imaging lens 115 and the second detection surface portion 1162 is LF. In the present embodiment, the difference between the optical path lengths LE and LF can be efficiently increased in a limited space as compared to the focus detection sensor 116 that does not include the protective film 118. In FIG. 16, the optical path length between the image-side main surfaces 1153av1, 1153av2, 1153ah1, 1153ah2 of the re-imaging lens 115 included in the first detection system FD1 and the first detection surface portion 1161 is LE. Further, the optical path length between the image-side main surfaces 1153as1, 1153as2, 1153ad1, and 1153ad2 of the re-imaging lens 115 included in the second detection system FD2 and the second detection surface portion 1162 is LF. Due to the step structure 117, the protective film 118, and the step structure 119, "LE <LF" is satisfied, and the imaging magnification of the second detection system FD2 is larger than the imaging magnification of the first detection system FD1. Therefore, the arrangement of optical images on the surface of the focus detection sensor 116 is as shown in FIG. When the optical image becomes large, the focus detection sensor 116 can precisely detect the fluctuation of the focus position, so that the focus detection accuracy increases.

  When the imaging magnification of the first detection system FD1 is increased similarly to the second detection system FD2, the focus detection sensor 116 itself must be enlarged. However, as shown in FIG. 9, the imaging magnification of the second detection system FD2 is relatively larger than the imaging magnification of the first detection system FD1, thereby preventing an increase in size of the focus detection sensor 116, The focus detection accuracy can be increased. Thereby, it is possible to provide a focus detection device in which the size of the image sensor and the focus detection accuracy are balanced.

  Further, the step structure 117 is configured such that the first detection surface portion 1161 is separated from the re-imaging lens 115 as compared to the second detection surface portion 1162. The step structure 119 has a structure in which the protective film thickness on the first detection surface portion 1161 is larger than the protective film thickness of the second detection surface portion 1162. In this case, the distance between the image-side main surface of the re-imaging lens 115 and the second detection surface portion 1162 is larger than the optical path length between the image-side main surface of the re-imaging lens 115 and the first detection surface portion 1161. The optical path length can be shortened. The imaging magnification of the second detection system FD2 is smaller than the imaging magnification of the first detection system FD1. As a result, the optical images 116as1, 116as2, 116ad1, and 116ad2 of the second detection system FD2 are smaller than the optical images 116av1, 116av2, 116ah1, and 116ah2 of the first detection system FD1. Thereby, the arrangement of the optical image on the surface of the focus detection sensor becomes as shown in FIG.

In FIG. 11, since the size of the focus detection sensor 116 is smaller than that in FIG. 9, the base line length 10bf and the base line length 10dh cannot be made as long as those in FIG. However, if the base line length 10bf and the base line length 10dh are shortened without changing the imaging magnification, the focus detection accuracy of the first detection system FD1 may be reduced due to the overlap of the optical images of the detection systems. Therefore, by reducing the optical image of the second detection system FD2, the optical image of the second detection system FD2 can be formed on the focus detection sensor 116 without overlapping the optical images. Therefore, even when the size of the focus detection sensor 116 is limited, highly accurate focus detection is possible.
As described above, by reducing the optical image of the second detection system FD2 relative to the optical image of the first detection system FD1, the focus detection accuracy is not impaired even if the image sensor is downsized. Therefore, it is possible to provide a focus detection device in which the imaging element and the focus detection accuracy are balanced.

10: Imaging lens 10ae, 10cg, 10bf, 10dh: Distance between the centers of gravity of the exit pupils of the imaging lens (base line length)
100: Focus detection device 115: Imaging lens (re-imaging lens)
1153av1 to 1153ad2: image-side main surface 116 focus detection sensor 1161, 1162: detection surface portion 117: step structure 118: protective film

Claims (9)

A focus detection device that divides a light beam that has passed through an imaging optical system and performs focus detection of the imaging optical system using a plurality of divided light beams,
A first focus detection optical system that performs focus detection of the imaging optical system from the relative positional relationship of a plurality of images formed on the first detection surface portion using the divided light flux having the first baseline length. When,
Relative positions of a plurality of images formed on a second detection surface portion different from the first detection surface portion using the divided light flux having a second base line length longer than the first base line length. A second focus detection optical system that performs focus detection of the imaging optical system from the relationship;
A focus detection apparatus, wherein a size of an optical image of the first focus detection optical system is different from a size of an optical image of the second focus detection optical system.   The focus detection apparatus according to claim 1, wherein an imaging magnification of the first focus detection optical system is different from an imaging magnification of the second focus detection optical system.   The position of the image side main surface of the imaging lens in the first focus detection optical system and the position of the image side main surface of the image formation lens in the second focus detection optical system are in a direction perpendicular to the detection surface portion. The focus detection apparatus according to claim 1, wherein the focus detection apparatus is different from each other. A focus detection sensor having the first detection surface portion and the second detection surface portion parallel to the first detection surface portion;
4. The focus detection apparatus according to claim 3, wherein an optical path length of the imaging optical system in the first focus detection optical system is different from an optical path length of the imaging optical system in the second focus detection optical system. .   The focus detection apparatus according to claim 4, further comprising a step structure between the first detection surface portion and the second detection surface portion.   The first detection surface portion and the second detection surface portion have a protective film on the side of the imaging lens constituting the imaging optical system, and the optical path length of the protective film of the first detection surface portion 6. The focus detection device according to claim 4, wherein the optical path length of the protective film on the second detection surface portion is different.   The first focus detection optical system and the second focus detection optical system perform focus detection of the imaging optical system on the same region of a subject. Focus detection device.   A lens barrel comprising the focus detection device according to claim 1. An imaging apparatus comprising the lens barrel according to claim 8.

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