JP2002333574A - Digital camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a digital camera equipped with a focusing means capable of sufficiently securing resolution necessary for focusing with a simple mechanism and having no possibility of the occurrence of Newton's rings or damage. SOLUTION: This digital camera is provided with a 1st wedged optical device having a 1st plane formed to be plane on either side and having a 1st inclined plane formed to be plane and inclined to the 1st plane on the other side, and a 2nd wedged optical device having a 2nd inclined plane formed to be plane in parallel with the 1st inclined plane on either side and having a 2nd plane formed to be plane in parallel with the 1st plane on the other side. The 1st and the 2nd wedged optical devices are arranged in a lens group or between the lens group and an imaging device, in a state where the 1st and the 2nd inclined planes are opposed to provide a specified gap. At least either the 1st wedged optical device or the 2nd wedged optical device is moved in a nearly orthogonal direction to an optical axis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to focus adjustment of an image pickup device by a lens group constituting an image pickup optical system in a digital camera.

[0002]

2. Description of the Related Art As a focus adjustment in a digital camera, a mechanical system such as a system in which a lens group constituting an imaging optical system is directly moved by providing a screw on a motor shaft or a system in which a lens group is cam-driven by a motor is used. Things are common.

[0003] On the other hand, although it is not a digital camera, a method of optically moving an image has been conventionally known.

For example, in a range finder of a camera, there is known a Dray-Kile system in which two wedge glasses are rotated in opposite directions to change a wedge angle when they are overlapped, and an active type auto focus system is known. A camera is known in which a glass plate is disposed between an element and a lens for adjusting a light beam for distance measurement, and the position of an image is moved by adjusting a tilt angle of the glass plate.

Further, in the field of civil engineering and construction, a laser projector used for distance measurement is disclosed in Japanese Patent Application Laid-Open No. H10-300499.
No. pp. 147-64. This is because the two wedge prisms are arranged in the laser beam projecting optical system with their inclined surfaces in contact with each other, and the two wedge prisms are moved along the inclined surfaces so that the focus of the laser light is increased. It is for making adjustments.

[0006]

In recent years, digital cameras have rapidly spread, and CCDs and CMs are used as image pickup devices.
An OS is used. Since these imaging elements have a smaller imaging area than a film, there is an advantage that the lens group can be made very small. However, with this, the amount of movement of the lens group required for focus adjustment is also extremely small, and the resolution required for focus adjustment is further reduced by increasing the number of pixels in the image sensor with the same area. Is being demanded. Similarly, the manufacturing tolerance of the imaging optical system itself is also proportionally narrowed. For these requests,
In the conventional focus adjustment method that moves the lens mechanically,
The number of intervening parts such as sliding parts increases, and accumulation errors accumulate, which is disadvantageous in terms of accuracy. Also, regarding the required resolution for focus adjustment (lens moving step), the method of rotating the screw stepwise has a limitation on the pitch of the screw,
At present, it is simply not possible to make details.

In the invention disclosed in Japanese Patent Application Laid-Open No. Hei 10-300499, the inclined surfaces of the two wedge prisms are brought into contact with each other, and there is a possibility that a Newton ring may be generated between the inclined surfaces or a scratch may occur. It is not suitable for use in the image pickup optical system.

The present invention has been made in view of such a problem, and it is not necessary to move a lens group unlike a conventional digital camera. Therefore, it is not necessary to maintain accuracy for coping with an optical axis shift due to the movement. SUMMARY OF THE INVENTION It is an object of the present invention to propose a digital camera provided with a focus adjusting means which can secure a sufficient resolution required for focus adjustment at a low cost with a simple mechanism and which does not cause the occurrence of Newton rings or damage. Aim.

[0009]

The above object is achieved by any of the following means.

In a digital camera in which subject light transmitted through a lens group constituting an image pickup optical system forms an image on an image pickup device, a first plane formed on a plane is provided on one side, and the first plane is formed with respect to the first plane. A first wedge-shaped optical element having a first inclined surface formed on an inclined plane on the other side, and a second inclined surface formed on a plane parallel to the first inclined surface on one side; A second wedge-shaped optical element having, on the other side, a second plane formed on a plane parallel to the first plane;
The first wedge-shaped optical element and the second wedge-shaped optical element are placed in the lens group or between the lens group and the imaging element in a state where a predetermined gap is provided with the second inclined surface facing the inclined surface. And moving at least one of the first wedge-shaped optical element and the second wedge-shaped optical element in a direction substantially perpendicular to an optical axis to perform focus adjustment on the image pickup element by the lens group. Digital camera that features.

In a digital camera in which subject light transmitted through a lens group constituting an imaging optical system forms an image on an image sensor, a curved surface formed symmetrically with respect to an optical axis of the lens group on one side, A first wedge-shaped optical element having, on the other side, a first inclined surface formed on a plane inclined with respect to the optical axis; and a second inclined surface formed on a plane parallel to the first inclined surface with one side. And a second wedge-shaped optical element having a plane formed orthogonally to the optical axis on the other side, wherein the second inclined surface is opposed to the first inclined surface. The first wedge-shaped optical element and the second wedge-shaped optical element are arranged in the lens group or between the lens group and the image pickup element with a gap, and the second wedge-shaped optical element is moved along the optical axis. And moved in a direction substantially perpendicular to the image pickup element by the lens group. Digital camera and performs focus adjustment to.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a digital camera according to the present invention will be described in detail with reference to the drawings.

First, the basic principle of the present invention will be described with reference to FIG. In FIG. 1, reference numeral 1 denotes a lens group constituting an imaging optical system of a digital camera, and reference numeral 2 denotes an optical element having planes parallel to each other. If there is no optical element 2,
Infinite subject image transmitted through the lens unit 1 forms an image on P _1, the distance from the final surface of the lens unit 1 to the image forming position P _1,
That is, the back focus and FB _1. Also, when the optical element 2 is inserted, the subject image at infinity extends by d and becomes P
Image on ₂ . Therefore, the thickness of the optical element 2 and t, and the refractive index is n, the back focus FB ₂ of when inserting the optical element 2 is expressed by the following equation.

FB ₂ = FB ₁ + d = FB ₁ + t (1-1 /
Here n), to arrange the imaging surface of the imaging device, such as a CCD at the position of P _2, infinite subject image is formed on the imaging surface of the imaging element. At this time, if the thickness t of the optical element 2 is reduced, F
The value of B ₂ becomes small, an infinite subject image is focused on the front of the imaging surface of the imaging device, the object distance formed on the imaging device is moved to the short distance side.

If the thickness of the optical element 2 is changed in this way, the distance of a subject to be imaged on the image sensor can be changed while the lens group 1 and the image sensor are fixed.

Next, an embodiment of the image pickup optical system according to the present invention will be described with reference to FIG. In FIG. 2, 11
Denotes a lens group, and at least one of a diaphragm and a sector 12 is disposed between the lens systems.
13 is an OLP filter and an IR cut filter,
Reference numeral 14 denotes an image sensor including a CCD or the like.

Here, a pair of wedge-shaped optical elements 15 and 16 are arranged between the lens group 11 and the OLP filter and the IR cut filter 13. Surface 15a of wedge-shaped optical element 15 on lens group 11 side, and wedge-shaped optical element 16
The surface 16a on the side of the OLP filter and the IR cut filter 13 is formed in a plane orthogonal to the optical axis O. On the other hand, opposing surfaces of the wedge-shaped optical elements 15 and 16 are inclined surfaces 1 inclined in parallel to the optical axis O.
5b, 16b, and inclined surfaces 15b, 16b
Are arranged so as to have a gap of about 0.2 m to 0.3 mm.

By moving such wedge-shaped optical elements 15 and 16 in a direction substantially perpendicular to the optical axis and in different directions, the wedge-shaped optical elements 15 and 16 are moved within a range where the principal ray of the lens group 11 is transmitted. Is changed, and the subject distance to be imaged on the image sensor 14 can be changed according to the above-described principle. Therefore, the focus can be adjusted by moving the wedge-shaped optical elements 15 and 16.

If the surfaces 15a and 16a are arranged in parallel with each other, they need not necessarily be orthogonal to the optical axis O.

The moving directions of the wedge-shaped optical elements 15, 16 need not necessarily be perpendicular to the optical axis as long as the surfaces 15a, 16a and the inclined surfaces 15b, 16b are maintained parallel to each other. For example, the direction may be along the inclined surfaces 15b, 16b.

Further, in some cases, one wedge-shaped optical element may be fixed and only the other wedge-shaped optical element may be moved.

Next, another embodiment of the image pickup optical system according to the present invention will be described with reference to FIG.

In FIG. 3, the same members as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted. The difference from FIG. 2 is the shape of the wedge-shaped optical element. The wedge-shaped optical element 25 has a curved surface 25a formed of a spherical surface or an aspherical surface on the lens group 11 side and formed symmetrically with respect to the optical axis O.
5a forms an imaging optical system together with the lens group 11.
Note that the wedge-shaped optical element 25 is fixed and does not move. Also,
The curved surface 25a may be convex or concave.

On the other hand, the wedge-shaped optical element 26 is
6, and moves independently in a direction substantially orthogonal to the optical axis O. The inclined surfaces 25b and 26b of the wedge-shaped optical elements 25 and 26 are inclined in parallel with each other and have a predetermined gap. As a result, similarly, the thickness of the wedge-shaped optical elements 25 and 26 changes within the range where the principal ray of the lens group 11 passes, and the subject distance to be imaged on the image sensor 14 can be changed according to the above-described principle. Element 26
The focus can be adjusted by moving.

The moving direction of the wedge-shaped optical element 26 is such that if the surface 26a maintains a state perpendicular to the optical axis O,
The direction does not always need to be orthogonal to the optical axis O, and may be, for example, a direction along the inclined surface 25b.

Contrary to the above, the wedge-shaped optical element 26 may be provided with a curved surface and fixed, and the wedge-shaped optical element 25 may be moved with both surfaces flat.

Further, the inclined surfaces 15b, 16 in FIG.
3 and the provision of the gaps on the inclined surfaces 25b and 26b in FIG. 3 prevent the generation of Newton rings,
This is to prevent the occurrence of scratches.

Next, an embodiment for moving the wedge-shaped optical element will be described with reference to FIG. Wedge-shaped optical elements 31 and 3
Reference numeral 2 denotes an optical element that performs the same operation as the wedge-shaped optical elements 15 and 16 in FIG.
a, and the wedge-shaped optical element 32 has a guide portion 32a at a lower portion. The guide portions 31a and 32a are guided by guide members (not shown), slide in the vertical direction, and keep the inclined surfaces 31b and 32b at a predetermined gap.

Driving levers 33 and 34 are provided to the left of the wedge-shaped optical elements 31 and 32 so as to be rotatable about a support shaft 35. The pin 31 c fits into a hole provided at the right end of the drive lever 33, and the drive pin 32 c standing upright on the guide portion 32 a of the wedge-shaped optical element 32 fits into a hole provided at the right end of the drive lever 34. Spring levers 33a, 34a are provided upright on the drive levers 33, 34, respectively, and a tension spring 36 is provided on the spring levers 33a, 34a. Therefore, the drive lever 33 is biased clockwise and the drive lever 34 is biased counterclockwise.
The drive lever 33 does not rotate clockwise from a predetermined position due to a stopper not shown, and the drive lever 34 does not rotate counterclockwise from a predetermined position.

Reference numeral 37 denotes a linear drive member, the lower portion of which is screwed with a shaft 38a of the motor 38, and the rotation of the linear drive member 37 is regulated by a guide member (not shown). Therefore, when the shaft 38a of the motor 38 rotates, the straight drive member 37 moves straight in the direction of the arrow. When the rectilinear driving member 37 moves rightward, the upper arm 37a presses the left ends of the driving levers 33 and 34, and the driving lever 33 rotates counterclockwise against the urging force of the tension spring 36,
The drive lever 34 rotates clockwise. As a result, the wedge-shaped optical element 31 moves upward via the drive pin 31c, and the wedge-shaped optical element 32 moves downward via the drive pin 32c. Therefore, the focus of the lens group 11 can be adjusted as described above.

When the linear drive member 37 moves leftward due to the rotation of the shaft 38a of the motor 38, the upper arm portion 37a
Try to separate from the left ends of the drive levers 33 and 34, but the urging force of the tension spring 36
Rotates clockwise and the drive lever 34 rotates counterclockwise, so that the left ends of the drive levers 33 and 34 follow the movement of the upper arm 37 a of the linear drive member 37. This allows
The wedge-shaped optical element 31 moves downward via the drive pin 31b, and the wedge-shaped optical element 32 moves upward via the drive pin 32b. Therefore, also at this time, the focus of the lens group 11 can be adjusted.

A reference portion 37b protrudes below the linear drive member 37, and can pass through the space between the photointerrupters 39 to detect a reference position for focus adjustment. The movement amount of the straight drive member 37 is controlled based on this reference position.

The wedge-shaped optical elements 31, 32 are molded from a resin material or a glass material, and the guide portions 31a, 32a are formed.
It is desirable from the viewpoint of cost to integrally mold with the drive pins 31c and 32c.
a and the like may be formed as separate members and integrally mounted on the wedge-shaped optical elements 31 and 32.

Next, another embodiment for moving the wedge-shaped optical element will be described with reference to FIG. Wedge-shaped optical element 41,
Reference numeral 42 denotes an optical element that performs the same operation as the wedge-shaped optical elements 25 and 26 in FIG. Wedge-shaped optical element 4 having curved surface 41a
1 has a flange portion 41c at the top, and the flange portion 41c
Is fixed to a fixing member (not shown) by a positioning pin 41d provided upright and fixed by bonding or the like. The wedge-shaped optical element 42 has a guide portion 42c on the left side, and is guided in the up-down direction by a guide member (not shown).

Reference numeral 47 denotes a linear drive member, the lower portion of which is screwed with a shaft 48a of a motor 48, and the rotation of the linear drive member 47 is regulated by a guide member (not shown). Therefore, when the shaft 48a of the motor 48 rotates, the straight drive member 47 moves straight in the direction of the arrow. Further, a left arm 47 a provided on the linear drive member 47 is fitted into a lower portion of the guide portion 42 c of the wedge-shaped optical element 42. Therefore, the wedge-shaped optical element 42 also moves in the vertical direction with the vertical movement of the linear drive member 47. Therefore, the focus of the lens group 11 can be adjusted.

The reference position for focus adjustment can be detected by passing the right arm 47b of the linear drive member 47 between the photointerrupters 49. The movement amount control of the straight drive member 47 is performed based on this reference position.

Finally, the correspondence between the terms described in the claims and the terms described in the embodiments of the invention will be described.

The first wedge-shaped optical element according to claim 1 corresponds to the wedge-shaped optical element 15, the first plane corresponds to the surface 15a,
The first inclined surface corresponds to the inclined surface 15b. The second wedge-shaped optical element corresponds to the wedge-shaped optical element 16, and the second plane corresponds to the surface 1
6a, and the second inclined surface corresponds to the inclined surface 16b.

The first wedge-shaped optical element according to claim 3 corresponds to the wedge-shaped optical element 25, the curved surface corresponds to the curved surface 25a, and the first inclined surface corresponds to the inclined surface 25b. The second wedge-shaped optical element corresponds to the wedge-shaped optical element 26, the plane corresponds to the surface 26a, and the second inclined surface corresponds to the inclined surface 26b.

[0040]

According to the digital camera described in the first to fifth aspects, it is not necessary to move the lens group unlike the conventional digital camera, so that it is not necessary to maintain the accuracy for coping with the optical axis shift due to the movement. Thus, the cost can be reduced by a simple mechanism, the resolution required for the focus adjustment can be sufficiently secured, and there is no danger of the occurrence of Newton's rings and damage.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic principle of the present invention.

FIG. 2 is a diagram of an embodiment of an imaging optical system.

FIG. 3 is a diagram of another embodiment of the imaging optical system.

FIG. 4 is a diagram of an embodiment in which a wedge-shaped optical element is moved.

FIG. 5 is a view of another embodiment for moving a wedge-shaped optical element.

[Explanation of symbols]

1,11 lens group 14 imaging element 15,16,25,26,31,32,41,42 wedge-shaped optical element

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) G03B 13/36 H04N 5/232 A 19/02 101: 00 H04N 5/225 G02B 7/11 D 5/232 P // H04N 101: 00 G03B 3/00 A

Claims (5)

[Claims] 1. A digital camera in which subject light transmitted through a lens group forming an image pickup optical system forms an image on an image pickup device. The digital camera has a first plane formed on one side, and the first plane is formed on the first plane. A first wedge-shaped optical element having, on the other side, a first inclined surface formed on a plane inclined with respect to the first inclined surface, and a second inclined surface formed on a plane parallel to the first inclined surface on one side; A second wedge-shaped optical element having, on the other side, a second plane formed on a plane parallel to the first plane;
The first wedge-shaped optical element and the second wedge-shaped optical element are placed in the lens group or between the lens group and the imaging element in a state where a predetermined gap is provided with the second inclined surface facing the inclined surface. And moving at least one of the first wedge-shaped optical element and the second wedge-shaped optical element in a direction substantially perpendicular to an optical axis to perform focus adjustment on the image pickup element by the lens group. Digital camera that features. 2. The apparatus according to claim 1, wherein said first plane and said second plane are orthogonal to an optical axis of said lens group.
A digital camera according to claim 1. 3. A digital camera in which object light transmitted through a lens group forming an image pickup optical system forms an image on an image pickup device, and a curved surface formed symmetrically around an optical axis of the lens group is provided on one side. A first wedge-shaped optical element having, on the other side, a first inclined surface formed on a plane inclined with respect to the optical axis; and a second inclined surface formed on a plane parallel to the first inclined surface. A second wedge-shaped optical element having a flat surface formed on one side and orthogonal to the optical axis is provided on the other side, and the second inclined surface is opposed to the first inclined surface. The first wedge-shaped optical element and the second wedge-shaped optical element are arranged in the lens group or between the lens group and the imaging element with a predetermined gap, and the second wedge-shaped optical element is The imaging element is moved by the lens group in a direction substantially orthogonal to the optical axis. A digital camera characterized by focusing on a child. 4. The curved surface formed on the first wedge-shaped optical element is a spherical surface or an aspherical surface.
A digital camera according to claim 1. 5. The digital camera according to claim 1, wherein the first wedge-shaped optical element and the second wedge-shaped optical element are formed of a resin material.