JP2503516Y2 - Focus detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a focus detection device for use in a camera, which performs focus detection using the subject light that has passed through a photographic lens,
In particular, the present invention relates to a phase difference detection type focus detection device provided with a condenser lens.

[Prior Art] Conventionally, as this type of focus detection device, for example, the one shown in FIG. 8 is known.

In FIG. 8, 10 is a taking lens, 20 is a field mask,
Reference numeral 30 denotes a condenser lens arranged near the planned focal plane position of the taking lens, and 41 and 42 are provided at positions conjugate with the vicinity of the exit pupil of the taking lens 10 and divided regions 11 and 12 inside the projected image. Aperture opening of aperture mask 40, which forms
Is a re-imaging lens, and 60 is an image sensor having a pair of sensor arrays A and B.

The light flux incident through the area 11 of the photographing lens 10 passes through the field mask 20, the condenser lens 30, the aperture opening 41, and the re-imaging lens 51, and the sensor array A of the image sensor 60.
Image on top. Similarly, the light beam incident through the area 12 of the photographing lens 10 passes through the field mask 20, the condenser lens 30, the opening 42, and the re-imaging lens 52 to form an image on the sensor array B of the image sensor 60. The pair of optical images formed on the sensor arrays A and B of the image sensor 60 come close to each other in a so-called front focus state in which the focus adjustment state of the taking lens 10 forms a sharp image of the subject before the planned focal plane, and the opposite. In the so-called rear pin state that connects after the planned focal plane,
At the time of so-called focusing to connect to the planned focal plane, they are lined up at a predetermined interval in between. In addition, the difference between the distance between the light images at the time of front focusing and rear focusing and the predetermined distance at the time of focusing has a value corresponding to the distance between the position where the sharp image of the subject is formed and the planned focal plane. Accordingly, after the pair of light images are photoelectrically converted by the sensor arrays A and B of the image sensor 60, the arithmetic processing is performed by the arithmetic unit to obtain the distance between the pair of light images, so that the focus adjustment state of the photographing lens 10 can be known. .

By the way, the condenser lens 30 used in the focus detection device shown in FIG. 8 has a jaw surface 32 provided orthogonally to the optical axis direction around the lens portion 31 as shown in FIG. , And has an outer peripheral surface 33 formed orthogonal to the jaw surface 32. On the other hand, the lens mounting portion 70 is provided with an optical axis direction positioning surface 71 formed so as to be orthogonal to the optical axis, and a mounting hole 72 having the optical axis as a central axis.

The condenser lens 30 supported by such a lens mounting member 70 has its position in the optical axis direction restricted by the contact between the jaw surface 32 and the optical axis direction positioning surface 71 of the mounting portion 70.
Also, the inner peripheral surface of the mounting hole 72 and the jaw surface 32 of the condenser lens 30.
The position in the plane orthogonal to the optical axis is regulated by fitting with the surface 33 following the.

[Problems to be Solved by the Invention] However, in such a conventional condenser lens support structure, due to the play between the outer peripheral surface 33 of the condenser lens 30 and the mounting hole 72 of the lens mounting member 70,
The condenser lens 30 may be displaced in a plane orthogonal to the optical axis.

Assuming that the condenser lens 30 is displaced in the plane orthogonal to the optical axis due to the looseness of the mounting, the condenser lens 30 may be displaced relative to the pair of aperture openings 41 and 42 formed in the aperture mask 40 as shown in FIG. An error θ occurs in the projection direction of the projected image by the lens 30.

When the error θ in the projection direction occurs in this way, in order to prevent vignetting of the light flux that should pass through the aperture openings 41 and 42 due to the pupil of the imaging lens 10, the projection direction of the aperture openings 41 and 4 is set to the direction of the imaging lens. There is no choice but to adjust the attitude of the focus detection device so that it is directed to the center of the exit pupil.

Therefore, if there is an error θ in the projection direction of the aperture openings 41, 42 of the aperture mask, the focus detection surface of the focus detection device will be inclined with respect to the planned focal plane of the taking lens 10, so it will be separated from the center of the focus detection field of view. There is a problem that the larger the subject image, that is, the subject image having an image height, the greater the focus detection error.

The present invention has been made in view of the above problems of the prior art, and prevents a focus detection error due to a displacement of a condenser lens mounting position, and enables a focus detection to be performed accurately even for a subject image having an image height. An object is to provide a detection device.

[Means for Solving the Problems] First of all, the present invention relates to a condenser lens positioned in the vicinity of an expected focal position of a photographing lens, and a diaphragm means provided behind the condenser lens and having two or more light transmitting holes. When,
And a re-imaging lens for forming a pair of secondary images on a line sensor corresponding to pupil division on a photographing lens provided behind the diaphragm means, wherein the condenser lens is supported by a lens mounting portion. The focus detection device is.

In the present invention for such a focus detection device, the condenser lens has a lens portion and a tapered surface formed by a conical surface of a cone formed around the lens portion and having the lens optical axis as a center, On the other hand, the lens mounting member has a tapered surface provided by a conical surface of a conical body that is substantially coaxial with a conical body that provides the tapered surface of the lens portion, and the tapered surface of the condenser lens and the taper of the lens mounting portion. The position of the condenser lens is restricted by the contact of the surfaces.

[Operation] According to the focus detection device of the present invention having such a configuration, since the condenser lens is positioned by abutting the tapered surface, the condenser lens can be positioned without rattling and the position in the plane orthogonal to the optical axis. Displacement can be reliably prevented. Therefore, it is possible to eliminate an error in the projection direction of the aperture opening and prevent a focus detection error due to the error.

[Embodiment] FIG. 1 shows an extracted support structure for a condenser lens according to the present invention, and FIG. 2 shows a single-lens reflex camera having a phase difference detection type focus detection device adopting the support structure shown in FIG. The example used for was shown.

First, in FIG. 2, the focus detection device is incorporated in the bottom of the camera body. The light from the subject that has passed through the taking lens 10 passes through the main mirror 80, is reflected downward by the sub mirror 81, and enters the focus detection apparatus 100.

The main elements of the focus detection device 100 are schematically shown together with the taking lens 10 of the camera, and are the same as those of the conventional device shown in FIG.

Alternatively, the photometric information may be detected by calculating the average value of the sum of the outputs of the sensor arrays A and B of the image sensor 60.

The focus detection device 100 includes a plastic housing 90, a visual field mask 20, a condenser lens 30, and a folding mirror 8.
3, diaphragm mask 40, re-imaging lens 50, image sensor 60
Fixed, and the infrared cut filter 82 is a field mask
The structure is glued on 20.

FIG. 3 shows a YY cross section near the re-imaging lens 50, and FIG. 4 shows an explanatory view seen from the Z direction in FIG.

In FIGS. 3 and 4, the re-imaging lens 50 is made of transparent plastic by integrally molding a pair of lenses 51 and 52 on the surface of one plate, and on both sides of the lens parts 51 and 52. A circular hole 53 for positioning and an oval hole 54 are formed. Further, the diaphragm mask 40 is a thin film having a light-shielding property and is provided with a pair of openings, and a circular hole 43 for positioning and an oblong hole 44 are also formed in this. On the other hand, two cylindrical bosses 91, 92 for positioning are formed in the housing 90, and the boss 92 is fitted into the re-imaging lens 50 and the circular holes 53, 43 of the diaphragm mask 40 to form the boss 91.
Are fitted with elliptical holes 54 and 44.

The specific assembly is as follows. First, the diaphragm mask 40 and the re-imaging lens 50.
The corresponding holes 43, 44, 53, 54 and the bosses 91, 92 are fitted into the housing 90 while being fitted in this order. Next, as is apparent from FIG. 4, viscous adhesives 93, 94, 95, 96 are filled and fixed in four places between the re-imaging lens 50 and the housing 90 so that they are spread in equal amounts. To do. When fixed in this way, the reimaging lens 50 is made by gluing adhesive on the tips of the bosses 91, 92.
Unlike the case of fixing between the
Re-imaging lens 50 because it does not need to protrude from 3,54
Even if the bosses 91 and 92 and the holes 53 and 54 are thin in place of the thickness of the device, there is no difficulty in manufacturing, and it is effective when it is desired to downsize the device.

Further, this fixing method has an advantage that even if the adhesive undergoes irreversible deformation due to changes in humidity and temperature, the position of the re-imaging lens 50 causes only reversible changes due to thermal expansion of itself and the housing 90. . As shown in FIG. 4, the four places where the adhesives 93, 94, 95, 96 are filled are as shown in FIG.
2 are symmetrically arranged with the center of 2 as an axis, and a concave portion for accumulating the adhesive is formed at a corresponding position of the re-imaging lens 50.

Next, the support structure of the condenser lens 30 will be described with reference to FIG.

In FIG. 1, a tapered surface 34 having the lens optical axis as the central axis is formed around the lens portion 31 of the condenser lens 30. The tapered surface 34 is provided as a part of a conical surface of a conical body having an axis coinciding with the optical axis of the condenser lens 30 and having a vertex P.

On the other hand, a tapered surface 98 is formed on the lens mounting portion 97 on the housing 90. Similar to the tapered surface 34 of the condenser lens 30, this tapered surface is provided as a conical surface of a cone having an axis that coincides with the optical axis of the condenser lens 30 and having the apex as the point P.

To attach the condenser lens 30 to the housing 90, the tapered surface 34 and the tapered surface 98 are in contact with each other as shown in the figure,
As shown in FIG. 2, a snap fit 21 of a visual field mask 20 made of plastic is fitted and engaged so as to sandwich the condenser lens 30 with the housing 90. For this reason,
The condenser lens 30 is biased and positioned in the optical axis direction by the elasticity of the field mask 20.

That is, by pressing the tapered surface 34 and the tapered surface 98,
Even if there is a relative positional deviation in the direction orthogonal to the optical axis on both sides, the centering function of the central axes of the two is obtained by the close contact of the tapered surfaces, and the condenser lens 30 is not decentered and the housing 90
Be positioned at.

Further, as shown in the figure, when the inclination directions of the tapered surfaces of the tapered surface 34 and the tapered surface 98 are formed so as to be narrowed to the light incident side, that is, the upper side of the condenser lens 30, both tapered surfaces are erroneously assembled at the time of assembly. Even if the condenser lens 30 is fixed in a tilted state without being firmly engaged with each other, there is an advantage that a focus detection error that occurs is small. The reason is as follows.

FIGS. 5 and 6 show a state in which the condenser lens 30 is tilted and attached, and the condenser lens 30 is tilted counterclockwise on the paper surface.

By the way, the sharp image on the focus detection surface of the focus detection device is
A sharp image is formed on the sensor array A of the image sensor 60 by the combined action of the condenser lens 30 and the re-imaging lens 51, while a sharp image is formed on the sensor array B of the image sensor 60 by the combined action of the condenser lens 30 and the re-imaging lens 52. Tie

Therefore, considering the optical path in the reverse direction, the focus detection surface 20
Reference numeral 1 denotes a surface on which the images of the sensor arrays A and B of the image sensor 60 are formed by the action of the re-imaging lens 51 or 52 and the condenser lens 30. When the condenser lens 30 is tilted counterclockwise as shown in FIG. 5, the focus detection surface 201 on which the images of the sensor arrays A and B of the image sensor 60 are formed is the same as shown in FIG. Tilt counterclockwise.

Referring again to FIG. 5, the condenser lens 30 shifts substantially along the tapered surface, and as a result, it is guided counterclockwise toward the paper surface and, at the same time, moves in parallel to the left. Due to the parallel movement of the condenser lens 30 due to this inclination, as shown in FIG. 7, the projection directions of the openings 41 and 42 of the aperture mask 40 by the condenser lens 30 are counterclockwise toward the paper surface. Lean. However, the aperture openings 41, 4
Adjust the posture of the focus detection device so that the projection direction of the aperture openings 41, 42 is directed to the center of the exit pupil of the photographing lens 10 in order to prevent the light flux that should pass through 2 from being vignetted in the pupil of the photographing lens 10. I have no choice.

As a result, the focus detection apparatus 100 is installed in the camera while being tilted clockwise toward the paper surface. In this adjustment, as shown in FIG. 7, the focus detection surface 201 tilted with respect to the optical axis X1 of the focus detection device in the state of FIG. It becomes a movement with the direction to make it follow the direction of.

Therefore, the inclination between the focus detection surface and the planned focal plane is smaller than the maximum inclination that can occur when the conventional support structure as shown in FIG. 9 is assembled without error.

This is because in the structure shown in FIG. 9, the back surface between the outer peripheral surface 33 of the condenser lens 30 and the mounting hole 72 of the lens mounting member 70 causes the condenser lens 30 to be in a plane orthogonal to the optical axis even if it is assembled without error. There was a risk of misalignment.

Assuming that the condenser lens 30 is displaced in the plane orthogonal to the optical axis due to the mounting play, the pair of diaphragm apertures formed in the diaphragm mask 40 as shown in FIG.
An error θ in the projection direction of the projected image by the condenser lens 30 is generated for 41 and 42.

When the error θ in the projection direction occurs in this way, the projection direction of the aperture openings 41, 42 is also captured in order to prevent vignetting of the light flux that should pass through the aperture openings 41, 42 due to the pupil of the imaging lens 10. There is no choice but to adjust the attitude of the focus detection device so that it is directed to the center of the exit pupil of the lens.

Thus, the focus detection plane is tilted with respect to the planned focal plane, and there is no action for automatically reducing it. On the other hand, in this embodiment, as described above,
Even if it is assembled by mistake, the inclination of the condenser lens 30 and the displacement of the focus detection surface due to the parallel movement cancel each other out, so that the inclination with respect to the planned focal plane becomes smaller.

That is, by arranging the condenser lens 30 and the tapered surfaces 34, 98 of the mounting portion 97 shown in FIG. 1 to the incident side, the displacement of the focus detection surface due to the inclination of the condenser lens 30 and the parallel movement is offset. Therefore, the focus detection error can be minimized.

[Advantage of the Invention] As described above, according to the present invention, since the lens mounting of the condenser lens is performed by contacting the tapered surfaces with each other, the mounting play can be removed and the focus detection error can be minimized. Furthermore, when the direction of the condenser lens and the taper surface of the mounting part is narrowed down to the photographing lens side (incident side), the condenser lens was incorrectly fixed during assembly without tilting the taper surface. Even in this case, the influence of the inclination of the condenser lens and the influence of the parallel movement tend to cancel each other out, and the effect of reducing the focus detection error can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment showing the mounting structure of a condenser lens according to the present invention; FIG. 2 is a structural view of an embodiment showing the mounting structure of a focus detection device of the present invention for a single-lens reflex camera; 3 is a sectional view taken along line YY of FIG. 2; FIG. 4 is an explanatory view seen from the Z direction of FIG. 3; FIG. 5 is an explanatory view of a state in which the condenser lens is tilted and assembled; FIG. 7 is an explanatory view of an operation when the condenser lens is tilted; FIG. 7 is an explanatory view of an operation when the condenser lens is moved in parallel, FIG. 8 is a configuration diagram of a conventional device, and FIG. 9 is an explanation of a conventional condenser lens mounting structure. It is a figure. [Explanation of symbols of main parts] 100: focus detection device, 10: photographing lens, 20: visual field mask, 3
0: Condenser lens, 34, 98: Tapered surface, 40: Aperture mask, 41, 42: Aperture aperture, 50: Re-imaging lens, 51, 52: Lens part, 60: Image sensor, 90: Housing, A, B: Sensor array

Claims (2)

(57) [Scope of utility model registration request] 1. A condenser lens disposed near a planned focal position of a taking lens, a diaphragm means provided behind the condenser lens and having two or more light transmitting portions, and a diaphragm means provided behind the diaphragm means. In a focus detection device having a structure in which a pair of secondary images corresponding to pupil division on the photographing lens are formed on a line sensor, and the condenser lens is supported by a lens mounting portion, The condenser lens has a lens portion and a taper surface formed on the periphery of the lens portion by a conical surface of a conical body having the lens optical axis as an axis center, and the lens mounting portion has a taper surface of the condenser lens. The tapered surface of the conical surface of the conical body that is substantially coaxial with the conical body that provides Ri focus detection device, characterized in that for regulating the position of the condenser lens. 2. The focus detecting device according to claim 1, wherein the tapered surface of the condenser lens is formed so that a diameter thereof is narrowed toward the photographing lens side.