WO2002079857A1

WO2002079857A1 - Small optical system using in image transmission apparatus

Info

Publication number: WO2002079857A1
Application number: PCT/KR2002/000470
Authority: WO
Inventors: Kyeng-Yong Kang; Jong-Jin Lee; Hyung-Su Kim
Original assignee: Kasc Technology Co., Ltd.
Priority date: 2001-03-20
Filing date: 2002-03-20
Publication date: 2002-10-10
Also published as: CN1509421A; KR100386647B1; KR20020074558A

Abstract

A small optical system for use in an image transmission apparatus is provided. The small optical system includes a base board, an image sensor, an optical refraction structure, a housing, and an infrared blocking unit. The image sensor is formed on the base board. The optical refraction structure is installed on the base board to cover the image sensor. In the optical refraction structure, a lens unit for focusing incident light on the image sensor, and a holder for the lens unit are integrated. The optical refraction structure partly contacts the area around the image sensing area of the image sensor. The housing contacts and seals the area on the base board around the optical refraction structure and covers the optical refraction structure excluding the lens unit. The infrared blocking unit is installed between the housing and the image sensor.

Description

SMALL OPTICAL SYSTEM USING IN IMAGE TRANSMISSION APPARATUS

Technical Field The present invention relates to the field of small optical systems, and more particularly, to a small optical system used in an image transmission apparatus.

Background Art Optical systems are generally composed of a plurality of lenses, a diaphragm, a filter, a holder and a body tube. The holder and the body tube are both for holding the lenses, the diaphragm and the filter so that they are distanced from one another at predetermined intervals.

As described above, most optical systems having lenses are required to be constructed in such a way that the lenses accurately focus on a surface within an allowable tolerance by compensating for the aberration of the lenses, in order to obtain a desired image. Accordingly, most optical systems are manufactured considering the above-described fact. FIG. 1 is a cross-section of a conventional small optical system for use in an image transmission apparatus. Referring to FIG. 1 , reference numeral 10 denotes a body tube, in which a lens 16 for focusing incident lights L1 and L2 onto an image sensor 14, and an infrared blocking filter 18 placed under the lens 16, are installed. Reference 20 denotes a holder built on a printed circuit board (PCB) 22 bonded with the image sensor 14 in a shape to surround the image sensor 14 while supporting the body tube 10. The holder 20 is screwed to the body tube 10. Accordingly, the body tube 10 and the holder 20 can be assembled by screwing the body tube 10 so that the lens 16 built in the body tube 10 focuses on the image sensor 14. A fixing ring 24 for fixing the lens 16 and the infrared blocking filter 18 a predetermined distance apart from each other is installed within the body tube 10.

Referring to FIG. 2, the image sensor 14, which is packaged, is composed of a package 22a bonded on the PCB 22, a stand 22b bonded onto the package 22a using an adhesive, such as, epoxy, and a board 22c bonded onto the stand 22b. Reference numeral 22d denotes an image sensing area on the board 22c. The image sensing area 22d senses the information included in the incident light beams L1 and L2. Reference numeral 26 denotes a wire for bonding the board 22c with the package 22a.

Such a conventional small optical system is bulky and heavy because of the existence of the holder 20 and the body tube 10. Accordingly, this structure is not suitable for a small optical system that is supposed to be compact and light, and the tolerance increases during the assembling of the optical system. For example, while the lens 16 is combined with the body tube 10, while the body tube 10 and the holder 20 are assembled, and while the holder 20 is combined with the PCB 22, tolerance may be generated or tilting may occur. These problems may also occur while constructing the image sensor 14 and while installing the image sensor 14 on the PCB 22. In particular, while constructing the image sensor 14, tolerance may be generated depending on the thickness of the stand 22b, tilting may be caused by the use of an adhesive like epoxy to adhere the stand 22b to the package 22a even if the thickness of the stand 22b is uniform, and tolerance may be generated depending on the thickness of epoxy. Also, while the component elements are sequentially assembled to construct the image sensor 14, tolerance may be generated depending on the rotation or tilting of each of the component elements. The above-mentioned individual tolerances are small, but the total tolerance of the above-described conventional optical system exceeds an allowable value. Accordingly, the above-described conventional small optical system requires an extra adjustment for compensating for the tolerances after its assembly. Thus, it is considered that substantial mass-production is impossible.

FIG. 3 is a cross-section of another conventional small optical system for use in an image transmission apparatus, in which a lens and its holder are unified. Referring to FIG. 3, the image sensor 14 having such a structure as shown in FIG. 2 is installed on the PCB 22, and an optical refraction structure 34, into which a lens unit 30 and its holder 32 are integrated, is coupled to the PCB 22 around the image sensor 14. The optical refraction structure 34 is coupled to the PCB 22 such that the lens unit 30 is located over the image sensor 14. An infrared blocking filter 36 is installed on the lens unit 30 of the optical refraction structure 34. A diaphragm 38 for restricting the incidence of light beams L3 and L4 upon the lens unit 30 is installed over the infrared blocking filter 36.

Unlike the conventional small optical system of FIG. 1 , the conventional small optical system of FIG. 3 does not require an extra focusing operation because the lens unit 30 and its holder 32 are unified and coupled to the PCB 22. However, the conventional small optical system of FIG. 3 still has the above-described problem in that tolerance may be generated or tilting may occur while constructing the image sensor 14 and while installing the image sensor 14 on the PCB 22.

Disclosure of the Invention

An object of the present invention to solve the above-described problems of the prior art is to provide a small optical system for an image transmission apparatus, the small optical system being compact and light and capable of increasing reliability and minimizing tolerance generated during assembly. In order to achieve the above object of the present invention, there is provided a small optical system for use in an image transmission apparatus, the system including a base board, an image sensor, an optical refraction structure, a housing, and an infrared blocking unit. The image sensor is formed on the base board. The optical refraction structure is installed on the base board to cover the image sensor. A lens unit for focusing incident light on the image sensor, and its holder, are integrated in the optical refraction structure. The optical refraction structure partly contacts the area around the image sensing area of the image sensor. The housing contacts and seals the area on the base board around the optical refraction structure and covers the optical refraction structure around the circumference of the lens unit. The infrared blocking unit is installed between the housing and the image sensor. Here, the image sensor is a wafer, in which semiconductor devices for image sensing are formed on the image sensing area.

A diaphragm and a lens are further installed around the lens unit of the optical refraction structure.

The rim of the optical refraction structure is fixed to the base board by indirectly contacting the base board through an adhesive. The image sensor included in the small optical system according to the present invention is not such an image sensor as shown FIG. 2 but a wafer on which a semiconductor device for image sensing is formed. The optical refraction structure, in which a lens unit and its holder are integrated, is coupled to the wafer such that the lens unit faces the semiconductor device for image sensing.

In a small optical system according to the present invention described above, an optical refraction structure directly contacts a wafer, on which a semiconductor device for image sensing is formed, and an image sensor does not have the packages and stands of a conventional image sensor and, accordingly, does not require an adhesive to attach a stand to the image sensor. This reduces a focusing tolerance generated by the coupling of the optical refraction structure to a PCB and a focusing tolerance generated by the use of a package, a stand, and an adhesive. Consequently, the total focusing tolerance of an optical system is reduced.

In addition, the space between a PCB and a portion of the optical refraction structure positioned around the wafer is filled with an adhesive to bond the PCB and the optical refraction structure. The PCB is also bonded with a housing that covers the optical refraction structure. That is, the optical system according to the present invention is constructed by double bonding, thus improving the reliability over a conventional optical system.

Brief Description of the Drawings FIG. 1 is a cross-section of a conventional small optical system for use in an image transmission apparatus;

FIG. 2 is a detailed cross-section of the image sensor of FIG. 1 ; FIG. 3 is a cross-section of another conventional small optical system for use in an image transmission apparatus; FIG. 4 is a cross-section of a small optical system for an image transmission apparatus, according to a first embodiment of the present invention;

FIG. 5 is a plan view of the image sensor of the small optical system of FIG. 4; and FIGS. 6 and 7 are cross-sections of small optical systems for an image transmission apparatus, according to the second and third embodiments of the present invention, respectively.

Best mode for carrying out the Invention The thicknesses of areas shown in the drawings are exaggerated for clarity of the specification. <First embodiment

Referring to FIG. 4, an image sensor 52 is attached onto a base board 50. The base board 50 can be one of the following: a printed circuit board (PCB), a flexible PCB (FPCB), and a printed wiring board (PWB). The image sensor 52 is a wafer W with an image sensing area 52a formed thereon, the image sensing area 52a on which image sensing semiconductor devices (not shown) are formed. An optical refraction structure 54, which covers the image sensor 52, is installed on the base board 50. Preferably, the optical refraction structure 54 is made of a material that is shock-resistant and not sensitive to changes in temperature. The optical refraction structure 54 is composed of a lens unit 54a and its holder 54b, which are integrated together. Preferably, the optical refraction structure 54 is positioned such that the center of the lens unit 54a faces the center of the image sensing area 52a. It is preferable that the lens unit 54a has a shape capable of focusing incident light beams L5 and L6 onto the image sensing area 52a of the image sensor 52. For example, the lens unit 54a is convex toward the image sensor 52, while having different radii of curvature at both sides of the lens unit 54a. An infrared blocking filter 56 for selectively blocking infrared from the light beams L5 and L6 incident through the lens unit 54a is installed between the lens unit 54a of the optical refraction structure 54 and the image sensing area 52a of the image sensor 52. A groove 58 is formed on the optical refraction structure 54 such that the infrared blocking filter 56 is inserted into the groove 58.

The optical refraction structure 54 directly contacts the image sensor 52. As shown in FIG. 5, it is preferable that they contact each other in some areas on a wafer W between the image sensing area 52a and bonding pads P. The optical refraction structure 54 and the image sensor 52 contact each other in four areas 60 around the image sensing area 52a. The area 60 may increase or decrease in number and area. The shape of each of the areas 60 may vary. For example, each area 60 can be circular or shapes other than rectangular.

The rim of the optical refraction structure 54 surrounds the image sensor 52, and is a predetermined distance isolated from the base board 50 around the image sensor 52. The space between the rim of the optical refraction structure 54 and the base board 50 is filled with an adhesive 62.

The optical refraction structure 54 is first contactedly fixed to the image sensor 52. Next, the space between the rim of the optical refraction structure 54 and the base board 50 is filled with an adhesive 62, such that the optical refraction structure 54 is fixed to the base board 50. Accordingly, when the optical refraction structure 54 is coupled to the base board 50, the distance between the lens unit 54a and the image sensor 52 are maintained to be uniform. Thus, a focusing tolerance of the lens unit 54a is not generated while the optical refraction structure 54 is coupled to the base board 50.

A housing 64 for protecting the optical refraction structure 54 is installed on the base board 50 such that the space between the housing 64 and the base are sealed and the lens unit 54a is exposed. The housing 64 serves as a diaphragm that blocks light from being projected onto areas other than the lens unit 54a by limiting the light beams L5 and L6 to be projected onto the lens unit 54a. Preferably, the housing 64 is made of a black, dull material that is wet-resistant and shock-resistant.

<Second embodiment

The reference numerals same as those of the first embodiment denote the same elements. The second embodiment will now be described by focusing on portions different from those in the first embodiment. Referring to FIG. 6, a small optical system according to the second embodiment of the present invention further includes a diaphragm 68, which limits light to be incident upon the lens unit 54a, installed around the lens unit 54a on an optical refraction structure 66. The diaphragm 68 is covered by a lens 70 for refracting incident light beams L7 and L8 prior to reaching the lens unit 54a. An area where the diaphragm 68 and the lens 70 can be installed is provided on the lens unit 54a of the optical refraction structure 66. Preferably, the lens 70 has a shape in which the incident light beams L7 and L8 are refracted so as to be collected within the diaphragm 68. A housing 72 is installed on the base board 50 to cover the optical refraction structure 66 and contacts the rim of the lens 70. <Third embodiment The same reference numerals as those in the first embodiment denote the same elements. The third embodiment will now be described by focusing on portions different from those in the first embodiment.

Referring to FIG. 7, an infrared blocking filter 76 is installed on a housing 74, unlike the small optical system according to the first embodiment of the present invention in which the infrared blocking filter 56 is interposed between the lens unit 54a and the image sensor 52. The infrared blocking filter 76 is installed on the housing 74 such as to cover the lens unit 54a. In order to support the edge of the infrared blocking filter 76 while also preventing the infrared blocking filter from protruding, the circumference of the lens unit 54a of the housing 74 is formed thinner than the other portions.

While this invention has been particularly shown and described with reference to preferred embodiments thereof, it should not be construed as being limited to the embodiments set fourth herein. For example, instead of additionally installing an infrared blocking filter, those skilled in the art to which the present invention pertains can think of alternative ways of coating one side of the lens unit 54a, preferably, its inner side, with an infrared film, or coating one side of the lens 70 installed on the lens unit 54a with an infrared film. Alternatively, an infrared blocking filter can be attached to the inner surface of a housing. Also, those skilled in the art to which the present invention pertains can diversify the shape, in which an optical refraction structure contacts an image sensor, into a circle, a rectangle, or other shapes. Therefore, the scope of the invention must not be defined by the described embodiments but by the technical spirit of the appended claims.

Industrial Applicability

In a small optical system according to the present invention as described above, an optical refraction structure directly contacts a wafer on which a semiconductor device for image sensing is formed, and an image sensor does not have the packages and stands of a conventional image sensor and, accordingly, does not require an adhesive to attach a stand to the image sensor. This reduces a focusing tolerance generated by the coupling of the optical refraction structure to a PCB and a focusing tolerance generated by the use of a package, a stand, and an adhesive. Consequently, the total focusing tolerance of an optical system is reduced.

Claims

What is claimed is:

1. A small optical system for use in an image transmission apparatus, the system comprising: a base board; an image sensor formed on the base board; an optical refraction structure installed on the base board to cover the image sensor, wherein a lens unit for focusing incident light on the image sensor, and a holder for the lens unit, are integrated, and the optical refraction structure partly contacting the area around the image sensing area of the image sensor; a housing that contacts and seals the area on the base board around the optical refraction structure and covers the optical refraction structure excluding the lens unit; and an infrared blocking unit installed between the housing and the image sensor.

2. The small optical system of claim 1 , wherein the infrared blocking unit is an infrared blocking filter installed between the image sensor and the lens unit.

3. The small optical system of claim 1 or 2, wherein the image sensor is a wafer in which semiconductor devices for image sensing are formed on the image sensing area.

4. The small optical system of claim 2, further comprising a diaphragm installed around the lens unit of the optical refraction structure.

5. The small optical system of claim 4, further comprising a lens installed on the lens unit in order to cover the diaphragm.

6. The small optical system of claim 1 , wherein the infrared blocking unit is an infrared blocking coating film with which the side of the lens unit facing the image sensor is coated.

7. The small optical system of claim 6, further comprising a diaphragm installed around the lens unit of the optical refraction structure.

8. The small optical system of claim 7, further comprising a lens installed on the lens unit in order to cover the diaphragm.

9. The small optical system of claim 1 , wherein the infrared blocking unit is an infrared blocking filter installed on the housing so as to cover the lens unit.

10. The small optical system of claim 1 , wherein the rim of the optical refraction structure is fixed to the base board by indirectly contacting the base board through an adhesive.

1 1. The small optical system of claim 1 , wherein the optical refraction structure directly contacts at least two areas on the image sensor around the image sensing area.