JP2003121744A - Imaging element, imaging unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging element in which the entire length from a light incident position to an imaging surface is shortened, and which facilitates the miniaturization of a portable terminal being an instrument mounting the imaging element thereon, and to provide an imaging unit using the imaging element. SOLUTION: The imaging element is an single prism lens 1b provided with reflective surfaces (second border plane 1b2, third border plane 1b3) for refracting an optical axis. An object image is imaged on a predetermined imaging surface 1c by making at least two surfaces into a lens surface among each border plane 1b1, 1b2, 1b3 and 1b4 which transmits or reflects incident light.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a personal computer (Personal Computer).
image pickup device, which is provided in a video camera or electronic still camera used by being mounted on a mobile terminal or a mobile terminal, and forms an image of a subject on the photoelectric conversion surface of the image pickup device, and this image forming device. The present invention relates to a provided image pickup device, and more particularly to a configuration in which the total length can be shortened as compared with a conventional lens optical system.

[0002]

2. Description of the Related Art Mobile phones, PCs (Personal Compute
r), personal digital assistants, videophone devices,
Alternatively, a predetermined image plane (photoelectric conversion surface of the image pickup device) is formed on an image of a subject to be photographed by being provided inside a video camera or an electronic still camera that is installed in a key place for security purposes. ) As an optical system for forming an image on the surface, a lens optical system having two groups and two lenses as shown in FIG.

A lens optical system 3 according to the prior art shown in FIG.
Is a fixed diaphragm 3a, a first lens 3b, a second lens 3c,
And a predetermined image forming surface 3d, which is a photoelectric conversion surface of the image pickup device, are arranged in order on the optical axis 3e.

However, in the prior art configuration as shown in FIG. 3, although the optical performance including the resolution at the peripheral position of the image pickup screen satisfies the required level, the mechanical total length from the light incident position to the image forming surface (see FIG. In the configuration shown in FIG. 3, it is difficult to shorten the length from the fixed diaphragm 3a to the image plane 3d along the optical axis 3e in terms of design, and devices equipped with these lens optical systems (cell phones, portable information). This has been a major obstacle in achieving the miniaturization of devices such as terminals.

The present invention has been made in view of the above situation, and in particular, it is made of a light-transmissive medium, and after the light incident on the inside of the medium from the subject is reflected twice at the boundary surface separating the inside and outside of the medium. At least two of the two transmission surfaces and the two reflection surfaces of the medium on the optical path have a predetermined curved surface shape so that the light is emitted to the outside of the medium and is formed as a subject image at a predetermined position. By forming an imaging element characterized by the above, by shortening the mechanical total length while maintaining a predetermined optical performance, it is possible to downsize the mounted device, An object is to provide an imaging device using an image forming element.

[0006]

In order to solve the above problems, the present invention provides an imaging device and an imaging device having the following configurations (1) to (3). (1) Made of a light-transmissive medium (optical glass, optical resin), and the light incident on the inside of the medium from a subject is reflected twice at the boundary surfaces 1b2, 1b3 separating the inside and outside of the medium, and then to the outside of the medium. 2 of the medium on the optical path so as to be emitted and to be formed as an image of the subject at a predetermined position 1c.
One transmission surface 1b1, 1b4 and two reflection surfaces 1b2, 1
An imaging element (single prism lens) 1b, wherein at least two surfaces of b3 are lens surfaces having a predetermined curved surface shape. (2) A boundary surface 2c1 which is made of a light-transmissive medium and which allows light entering the inside of the medium from a subject to separate the inside and outside of the medium.
Each of the two transmissive surfaces 2c11, 2c13, and 2c so that the light is reflected twice at 2, 2c25 and then emitted to the outside of the medium to form an image of the subject at a predetermined position 2d.
c24, 2c26 and one reflecting surface 2c12, 2c25
A pair of optical elements (first prism 2c1, second prism
6c 2c11, 2c13, 2c24, 2c in which the transmission surface and the reflection surface of each optical element 2c1, 2c2 are combined and arranged.
An imaging element (two prism lenses) 2c, characterized in that at least two surfaces of 262c12 and 2c25 are lens surfaces having a predetermined curved surface shape. (3) The imaging element 1b or 2 according to claim 1 or 2.
An imaging device (video camera,
Digital still cameras, mobile phones, personal digital assistants, personal computers).

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made to the accompanying drawings for a single prism lens (first embodiment) and a two-element prism lens (second embodiment) which are preferred respective embodiments of the present invention. And explain. FIG. 1 is a block diagram of an optical system including a single prism lens that is a first example according to the embodiment of the present invention, and FIG. 2 shows a double prism lens that is a second example according to the same embodiment of the present invention. It is a block diagram of the equipped optical system.

(First Example) First, a single prism lens which is a first example according to the embodiment of the present invention will be described with reference to the configuration diagram of FIG.

The image forming optical system 1 including the single prism lens of this embodiment has a fixed diaphragm 1a and a single prism lens 1b.
And a predetermined image forming surface 1c (which is a photoelectric conversion surface of an image pickup device (not shown)) are sequentially arranged along the optical axis bent by the reflecting surface in the middle. In addition, an image pickup device required to configure a video camera or an electronic still camera (digital still camera) equipped with the single prism lens of this embodiment,
Each configuration of the signal processing unit, the signal recording / reproducing unit, the casing, etc. is based on a well-known technical configuration, and the description thereof is omitted.

In the image forming optical system 1 shown in FIG. 1, a fixed diaphragm 1a is arranged in front of the single prism lens 1b (a subject side not shown, facing left in the drawing), and behind the single prism lens 1b ( An image pickup device (not shown) is arranged in the direction of light traveling, that is, the method of turning to the right in the drawing.

The single prism lens 1b is formed of a light-transmissive medium such as optical glass or optical resin, and has two transmission surfaces (a transmission surface and a reflection surface) that transmit or reflect light relating to the formation of a subject image, which will be described later. 1b1, 1b4), and the reflection has two boundary surfaces (1b2, 1b3).

That is, the first boundary surface 1b1 which is the incident surface on which the light emitted from the subject is incident, and the second boundary surface 1 which reflects the light incident from the first boundary surface 1b1 and traveling through the medium.
b2, a third boundary surface 1b3 and a third boundary surface 1b that reflect the light reflected by the second boundary surface 1b2 and traveling in the medium.
It is a fourth boundary surface 1b4 that emits the light reflected by 3 and traveling through the medium toward the imaging surface side to the outside of the medium. The first
Is a concave transmissive surface (the medium is concave. The irregularities on the transmissive surface will be referred to as irregularities of the light transmissive medium),
Is formed as a concave reflection surface, the third boundary surface is formed as a concave reflection surface, and the fourth boundary surface is formed as a convex transmission surface.

Next, the action of each component on the traveling light will be described in order according to the traveling sequence of the light in the imaging optical system 1 of FIG. A light beam emitted from a subject (not shown) passes through the fixed diaphragm 1a so that unnecessary light is cut and enters the first boundary surface 1b1 of the single prism lens 1b.
The light rays contained in this incident light beam are refracted in the diverging direction at the first boundary surface (concave transmission surface) 1b1 and then travel in the medium,
Further, after being reflected in the converging direction by the second boundary surface (concave reflection surface) 1b2, it travels through the medium and the third boundary surface (concave reflection surface) 1
After being reflected in a converging direction at b3, it travels in the medium, is further refracted in the converging direction at the fourth boundary surface (convex transmitting surface) 1b4, and is emitted to the outside of the medium, and finally on the predetermined image forming surface 1c. It converges and forms a subject image. At this time, the shapes of the first to fourth boundary surfaces described above are lens surfaces having a predetermined curved surface shape for forming a subject image on the predetermined image forming surface 1c. The configurations (1) and (2) described below are modified examples of the configuration of the present embodiment described above, and these are also included in the present invention. That is, (1) an image-forming element made of a light-transmissive medium for forming an image of a subject on a predetermined image-forming surface, the incident surface on which light from the subject is incident, and the incident surface. A first reflecting surface, which is one boundary surface of the medium, that reflects light that has entered from the inside and travels in the medium in a direction other than the predetermined image plane side;
Second reflection surface formed by the other boundary surface of the medium and reflected by the second reflection surface of the medium and reflected by the second reflection surface of the medium to travel toward the predetermined image formation surface. And an emission surface for emitting the light traveling through the medium to the side of the predetermined image formation surface, and the light emitted from the emission surface is converged on the predetermined image formation surface to form an image of the subject. As shown in the image, by configuring at least two of the entrance surface, the first reflection surface, the second reflection surface, and the exit surface as a lens surface having a predetermined curved surface shape, In comparison, the imaging element is characterized in that its entire length can be degenerated. And (2) a light-transmissive medium, in which the light incident on the inside of the medium from a subject is reflected twice at the boundary surface separating the inside and outside of the medium, and then is emitted to the outside of the medium at the predetermined position. An imaging element characterized in that at least two of the two transmission surfaces and the two reflection surfaces of the medium on the optical path are lens surfaces having a predetermined curved surface shape so as to form an image of a subject. Is. That is, in addition to the configuration in which all the transmitting and reflecting surfaces (all four surfaces) on the optical path are lens surfaces having a predetermined shape as in this embodiment, at least two of the above four surfaces are used as lens surfaces. A configuration that achieves the same operation and effect as the embodiment is also possible.

According to the above structure, since the optical axis through which light travels can be bent at the reflecting surface in the middle,
While maintaining the optical performance, the mechanical total length L from the light incident position (the front surface of the fixed diaphragm 1a) to the predetermined image forming surface 1c is greatly shortened as compared with the conventional lens system as shown in FIG. As a result, an imaging element (single prism lens 1
It is possible to promote the miniaturization of the device equipped with b).

Each boundary surface 1b of the single prism lens 1b
The arrangement of positive and negative powers in 1, 1b2, 1b3, 1b4 is not limited to the configuration described above. For example, some boundary surfaces may be planes (power is 0),
The curved surface shape of each boundary surface is not limited to a spherical surface, and may be an aspherical surface or another shape. In the above configuration, a configuration in which at least two of the first to fourth boundary surfaces 1b1, 1b2, 1b3, 1b4 are curved surfaces to have power is one of these modifications, and the present invention includes them. The point is the same as described above. Further, in the configuration shown in FIG. 1 described above, the position of the fixed diaphragm 1a is located in front of the first boundary surface 1b1, but other arrangements are of course possible.
The reason for arranging as described above in this embodiment is that the pupil position is arranged relatively far from the image point by arranging the diaphragm near the first boundary surface (first surface of the optical system) 1b1. This is because it is possible to reduce the aberration of the peripheral image and the reduction of the light amount on the image forming surface, and to reduce the size of the single prism lens 1 by suppressing the spread of the light flux in the single prism lens 1b.

Further, a diffraction grating is provided on any of the above-mentioned boundary surfaces to suppress a specific spatial frequency response by a well-known diffractive action to suppress an interference phenomenon between the specific spatial frequency and the pixel pitch of the image sensor. It is also possible to adopt a configuration incorporating a known function of a so-called optical low-pass filter.

(Second Example) Next, a two-element prism lens, which is a second example of the embodiment of the present invention, will be described with reference to the configuration diagram of FIG.

The image forming optical system 2 shown in FIG. 2 is an IR cut filter 2 for cutting unnecessary infrared light in an incident light beam.
a, a fixed diaphragm 2b, a two-sheet prism lens 2c, and a predetermined image forming surface 2d are sequentially arranged along the optical axis having a bending point in the middle. The above two prism lens 2c
Is composed of a first prism 2c1 and a second prism 2c2 which are respectively formed of a light transmissive medium such as optical glass or optical resin. Further, the two prism lenses 2c have a first boundary surface (convex transmission surface) 2c in the order in which light travels.
11, the second boundary surface (flat reflective surface) 2c12, the third boundary surface (convex transmissive surface) are respectively provided in the first prism 2c1, the fourth boundary surface (convex transmissive surface) 2c24, the fifth The boundary surface (planar reflecting surface) 2c25 and the sixth boundary surface (convex transmitting surface) 2c26 are provided on the second prism, respectively.

The above-mentioned first boundary surface 2c11 and fourth boundary surface 2c24 have a weak curved surface power and are mainly involved in aberration correction in the imaging action, and thus the second boundary surface 2c2.
The second and third boundary surfaces 2c23 have relatively strong positive power and are mainly involved in focal length setting and aberration correction in the imaging action.

The operation of the image forming optical system 2 given to the light according to the progress of the light will be described in order. Light emitted from an object (not shown) will first be reflected by the IR cut filter 2a and the fixed diaphragm 2.
After passing through b and b, it is incident on the first boundary surface 2c11 of the first prism 2c1 forming the two-sheet prism lens 2c. The above incident light has a first boundary surface (convex transmission surface) 2
After refracting in the converging direction at c11, it travels in the medium,
After being reflected by the second boundary surface (planar reflecting surface), the light is emitted to the outside of the first prism 2c1 while being refracted in the direction of convergence by the third boundary surface (convex transmitting surface) 2c13. The emitted light is the fourth boundary surface (convex transmission surface) of the second prism 2c2.
2c24 enters the medium of the second prism 2c2,
After traveling through the medium, the fifth boundary surface (planar reflecting surface) 2c
After being reflected at 25, it travels through the medium, passes through the sixth boundary surface (convex transmissive surface) 2c26, and is refracted in the converging direction to the second surface.
Exits to the outside of the prism 2c2, and eventually the predetermined image plane 2
The image of the subject is formed by converging on d. At this time, the first
Each of the third, fourth, and sixth boundary surfaces is formed as a lens surface having a predetermined shape so that the subject image is formed on the predetermined image forming surface 2d. The configurations (1) and (2) described below are configurations embodied on the basis of the same technical idea as the present embodiment as modified examples of the configuration of the present embodiment described above. It is included in the present invention.
That is, (1) an image forming element for forming an image of a subject on a predetermined image forming surface, the first prism reflecting light incident from the subject in a direction other than the predetermined image forming surface side. And a second prism that reflects the light reflected by the first prism toward the predetermined image forming surface side, and the light reflected by the second prism converges on the predetermined image forming surface and At least two of the transmission surface and the reflection surface on the optical path of the first prism and the second prism are configured as lens surfaces having a predetermined curved surface shape so as to form an image of a subject. An imaging element characterized in that the entire length can be degenerated compared to the optical path length. And (2) a light-transmissive medium, in which light incident from the subject into the medium is reflected twice at a boundary surface separating the inside and outside of the medium and then emitted to the outside of the medium at a predetermined position. A pair of optical elements each having two transmissive surfaces and one reflective surface are arranged in combination so as to form an image of a subject, and the transmissive surface and the reflective surface of each optical element are combined. At least two of the surfaces are lens surfaces having a predetermined curved surface shape. That is, in addition to the configuration in which four surfaces out of the transmission surface and the reflection surface (all six surfaces) on the optical path are lens surfaces having a predetermined shape as in the present embodiment, at least two of all six surfaces are provided. It is also possible to adopt a configuration in which the lens surface achieves the same operation and effect as in this embodiment. Note that each component such as an image pickup device, a signal processing unit, a signal recording / reproducing unit, and a housing, which is necessary to configure a video camera equipped with the two-prism lens of this embodiment, or an electronic still camera (digital still camera). Has a configuration according to a well-known technical configuration, and a description thereof will be omitted.

In the above structure, since the optical axis through which light travels is bent at the reflecting surface in the middle, it is possible to promote the miniaturization of the equipment equipped with this image forming element (two prism lenses 2c). Point, 2 prism lens 2c
Boundary surfaces 2c11, 2c12, 2c13, 2c24 of
The arrangement of the positive and negative powers in 2c25 and 2c26 is not limited to the configuration described above, and for example, in the configuration in which at least two of the first to sixth boundary surfaces are curved to have power, However, it is possible to arrange the fixed diaphragm 2b at other positions, which is included in the present invention. However, as in the present embodiment, the diaphragm is arranged at the first boundary surface (optical). 1st surface of the system) 2c11
By arranging them in the vicinity, the pupil position can be arranged relatively far from the image point, and the aberration of the peripheral image and the light amount reduction on the image plane can be reduced, and the size of the two-prism lens 2b can be reduced. It is also possible to provide a diffraction grating on any of the above-mentioned boundary surfaces and to incorporate a function of a known optical low-pass filter in the above-mentioned first embodiment. It is similar to the single prism lens 1b.

Further, in the two-sheet prism lens 2c of the present embodiment, as a modified example whose details are different from the configuration shown in FIG.
If an IR cut filter is arranged at a position sandwiched between the first prism 2c1 and the second prism 2c2 (not shown), the total length can be further reduced, or the first prism 2c1 and the second prism 2c2 can be made smaller. If they have the same shape, it is possible to improve productivity, stabilize performance, and reduce the unit price of parts and die cost. Needless to say, the present invention includes the first and second embodiments described above, modified examples thereof, and imaging elements having configurations easily reachable from these descriptions.
Image pickup device (video camera,
Digital still cameras, etc.) and their imaging devices
Devices (cell phones, personal computers, personal digital assistants, etc.) mounted as one component block are also embodied based on the technical idea of the present invention described above, and are included in the present invention.

[0023]

As described in detail above, the present invention is
It is made of a light-transmissive medium, so that the light entering the inside of the medium from the subject is reflected twice at the boundary surface separating the inside and outside of the medium and then exits to the outside of the medium to form an image of the subject at a predetermined position. A predetermined optical performance by using an imaging element characterized in that at least two of the two transmitting surfaces and the two reflecting surfaces of the medium on the optical path are lens surfaces having a predetermined curved surface shape. The imaging element that shortens the mechanical overall length while maintaining
Also, it is possible to provide an imaging device using this imaging element.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical system including a single prism lens that is a first example according to an embodiment of the present invention.

FIG. 2 is a second example 2 according to the exemplary embodiment of the present invention.
It is a block diagram of an optical system provided with a single prism lens.

FIG. 3 is a configuration diagram of a two-lens optical system which is an imaging optical system according to a conventional technique.

[Explanation of symbols]

1b Single prism lens (imaging element) 1b1, 1b4 Transmission surface (boundary surface) 1b2, 1b3 Reflection surface (boundary surface) 1c Predetermined imaging surface (predetermined position) 2c Two prism lenses (imaging element) 2c1 1st Prism (optical element) 2c2 Second prism (optical element) 2c11, 2c13, 2c24, 2c26 Transmissive surface (boundary surface) 2c12, 2c25 Reflective surface (boundary surface) 2d Predetermined image plane (predetermined position)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 5/225 H04N 5/225 DF term (reference) 2H042 CA01 CA12 CA14 CA17 2H087 KA02 KA03 LA01 RA41 RA44 2H091 FA21X FA26X LA11 2H101 BB21 5C022 AA13 AB12 AC54

Claims (3)

[Claims] 1. A light-transmissive medium, wherein light incident on the inside of the medium from a subject is reflected twice at a boundary surface separating the inside and outside of the medium, and then is emitted to the outside of the medium at the predetermined position. An imaging element characterized in that at least two of the two transmission surfaces and the two reflection surfaces of the medium on the optical path are lens surfaces having a predetermined curved surface shape so as to form an image of a subject. . 2. A light-transmissive medium, wherein light incident on the inside of the medium from a subject is reflected twice at a boundary surface separating the inside and outside of the medium, and then is emitted to the outside of the medium at a predetermined position. 2 for each to form an image of the subject
A pair of optical elements having one transmissive surface and one reflective surface are combined and arranged, and at least two of the six surfaces of the transmissive surface and the reflective surface of each optical element are combined.
An imaging element, wherein the surface is a lens surface having a predetermined curved surface shape. 3. An image pickup apparatus comprising the image forming element according to claim 1.