WO2007142403A1

WO2007142403A1 - Integrated micro-optic device

Info

Publication number: WO2007142403A1
Application number: PCT/KR2007/001611
Authority: WO
Inventors: Sung-Chul Juh
Original assignee: Mobisol Inc.
Priority date: 2006-06-02
Filing date: 2007-04-03
Publication date: 2007-12-13
Also published as: KR20060080146A; KR100700507B1

Abstract

The present invention relates to an integrated micro-optic device characterized by structural features aimed at providing bent optical paths to effectively block stray light from reaching an imaging lens. A preferred embodiment of an integrated micro-optic device according to the invention comprises at least one light source; a transparent lens module comprising at least one illumination optical system for directing radiated light rays and an imaging lens system for focusing the light reflected from the object plane onto a sensor; an opaque module cover structure which houses the lens module and comprises at least one first stray light blocking portion disposed between the light source(s) and the sensor; and a sensor cover module which is assembled under the lens module and comprises at least one second stray light blocking portion disposed between the light source(s) and the sensor.

Description

Description INTEGRATED MICRO-OPTIC DEVICE

Technical Field

[1] The present invention relates to an integrated micro-optic device characterized by structural features aimed at providing bent optical paths to effectively block stray light from reaching an imaging lens.

[2]

Background Art

[3] FIG. 1 is a cross-sectional view of a conventional optical device.

[4] The conventional optical device is configured such that light rays radiated from an

LED 100 having a convex light-emitting surface enter a monolithic optical system 110 comprising optically transparent lenses and reflective surfaces, in which the light rays are reflected twice before hitting and bouncing off an object surface 120 to get to a sensor via an imaging lens.

[5] This conventional optical device offers a uniform radiation pattern provided by the

LED having a convex light-emitting surface; therefore, reflective surface design requires little more than optical path calculation. It can also accommodate an imaging lens with an extended depth of focus.

[6] Such a conventional structure of optical device, however, would be rendered inoperable if miniaturized, for optical efficiency would significantly deteriorate.

[7] FIG. 2 is a cross-sectional view of another example of a prior art optical system as disclosed in Korean Patent OPN (Unexamined Publication Number) 10-2004-89907. This optical system comprising an LED chip-on-board (COB) module requires a first lens plane 200 for condensing light rays radiated from a light source and a reflective surface 210 for directing the light beam onto an object surface. Intended for use in a miniature mouse, this optical system has a sensor 220 and an LED 230 mounted on a same plane using COB technology, thus allowing for a significant reduction in height.

[8] Although employment of a slim LED as a light source, which may be mounted on a printed circuit board (PCB) using either COB or surface mount technology (SMT), allows for a slim design, a Lambertian radiation associated with such a light source cannot provide an adequate lighting to allow an imaging sensor to obtain quality images if used with simple convex lenses and planar reflective and output surfaces.

[9] Application of a slim LED, thus, requires an optical system with light directing capability to provide optimum uniform illumination of areas relevant to acquisition of images. In addition, it is desirable that said optical system with light directing capability have light condensing capability to enhance optical efficiency for ap- plication in portable information devices.

[10] Referring to FIG. 2, the optically transparent interior of the conventional optical system cannot prevent stray light components from being scattered and eventually admitted through a second lens plane 240. Nor does the optical system have an aperture control mechanism to prevent light rays radiated from the light source from affecting the sensor directly as optical noise. The intensity of light directly incident to an imaging lens is greater than that of light incident to the imaging lens after being reflected from an object plane. Thus, the signal-to-noise ratio may likely be too low to ensure normal operation of the sensor.

[11] This problem is aggravated by the proximity of the sensor, the light source, and a target object illuminated, so designed to obtain a slim and small optical sensor module. Because of the closeness of a bright light source and a sensor of high sensitivity, even an otherwise insignificant amount of stray light may seriously degrade or even disable the operation of the sensor. Thus, optical and electrical separation of the two is of vital importance.

[12] In optical illumination, the intensity of illumination on an object plane is inversely proportional to the square of the optical distance from the light source to a given spot. Such distance difference is not negligible when the light source, sensor, and target object illuminated are in close proximity to each other. In a slim and small optical system, for example, spots closer to the light source will be perceptibly brighter than more distant spots. Such varying illumination will degrade the operation of the sensor.

[13] Illumination of segmented target areas using light guide means such as fiber-optic bundles may solve this particular problem but is not a viable option due to the cost and difficulty associated with incorporating such a system into an integrated unit.

[14]

Disclosure of Invention Technical Problem

[15] It is an object of the present invention to provide an integrated micro-optic device capable of preventing light rays radiated from internal/external light sources from being scattered and directly reaching a sensor.

[16]

Technical Solution

[17] To achieve the above object, according to a preferred embodiment of the present invention, there is provided an integrated micro-optic device comprising at least one light source; a transparent lens module comprising at least one illumination optical system for directing radiated light rays and an imaging lens system for focusing the light reflected from the object plane onto a sensor; an opaque module cover structure which houses the lens module and comprises at least one first stray light blocking portion disposed between the light source(s) and the sensor; and a sensor cover module which is assembled under the lens module and comprises at least one second stray light blocking portion disposed between the light source(s) and the sensor. [18]

Advantageous Effects

[19] An integrated micro-optic device according to the present invention is characterized by structural features that provide bent optical paths to effectively block stray light from reaching the sensor via the imaging lens. [20]

Brief Description of the Drawings

[21] FIG. 1 is a cross-sectional view of a conventional optical device;

[22] FIG. 2 is a cross-sectional view of another example of a prior art optical system as disclosed in Korean Patent OPN (Unexamined Publication Number) 10-2004-89907; [23] FIGS. 3 and 4 are disassembled perspective views of an optical device according to an embodiment of the present invention; [24] FIGS. 5 and 6 are perspective views of a module cover structure according to an embodiment of the invention; [25] FIGS. 7 and 8 are perspective views of a lens module according to an embodiment of the invention; [26] FIGS. 9 and 10 are perspective views of a sensor cover module according to an embodiment of the invention; [27] FIG. 11 is a schematic cross-sectional view of an optical device according to the invention, such as shown in FIGS. 3 and 4, taken along the illumination optical systems. [28] FIG. 12 is a schematic cross-sectional view of an embodiment of an illumination optical system according to the invention; [29] FIG. 13 is a schematic cross-sectional view of an optical device according to the invention, such as shown in FIGS. 3 and 4, taken along the first stray light blocking portions. [30] FIG. 14 is a graph illustrating the intensity of illumination on an object plane according to one example of the invention; [31] FIG. 15 is a schematic diagram illustrating a configuration of light sources according to an embodiment of the invention; and [32] FIG. 16 is a schematic diagram illustrating a configuration of light sources according to another embodiment of the invention. [34] <Description of reference numerals>

[35] 100, 230: LED 110: optical system 120: object surface

[36] 200: first lens plane 210: reflective surface 220: sensor

[37] 240: second lens plane 300, 300': light source 310, 310': illumination optical system

[38] 311: input lens 312: reflector lens 313: output lens

[39] 320: imaging lens system 321: imaging lens 330: lens module

[40] 331: lens module foot 332: assembly hole 340: object plane

[41] 360: sensor 370: sensor cover module 371: aperture portion

[42] 372: second stray light blocking portion 373: sensor cover module foot 374: complementary stray light blocking portion

[43] 380: PCB 390: module cover structure 391: first stray light blocking portion

[44] 392: lens module coupling portion 393: module cover foot

[45]

Mode for the Invention

[46] It is to be understood that the terminology and phraseology employed herein are for the purpose of description and are not to be construed as limiting. They are, thus, best understood when interpreted in the context of the technological concept and scope of the present invention.

[47] Likewise, the constructions as illustrated and described in the drawings and specification are merely representative of some of the currently preferred embodiments of the present invention. They do not represent the entire technological concept and scope of the invention, and a number of equivalent or modified substitutes for them may exist at the time of filing the present application.

[48] The present invention will now be described in detail in connection with the preferred embodiments thereof with reference to the accompanying drawings.

[49] FIGS. 3 and 4 are disassembled perspective views of an optical device according to an embodiment of the present invention. Referring to FIGS. 3 and 4, an optical device in accordance with the invention comprises a PCB 380 on which are mounted at least one light source 300 and a sensor 360 for sensing light reflected from an object; a sensor cover module 370 for protecting the sensor 360; a lens module 330 for condensing light rays radiated from the light source(s) 300 onto an object plane 340 and focusing the light reflected from the object plane 340 onto the sensor 360; and a module cover structure 390 for housing and protecting the sensor cover module 370 and the lens module 330 mounted on the PCB 380.

[50] When more than one light source 300 is used, the light sources may be formed of diode chips emitting lights of different colors, taking into account their different reflection characteristics for objects with different optical characteristics. Possible light sources include LED chips, laser diode chips, and infrared diode chips.

[51] Methods of attaching a sensor 360 to a PCB 380 include, but are not limited to, wire bonding and flip chip technologies.

[52] FIGS. 5 and 6 are perspective views of a module cover structure according to an embodiment of the invention. Referring to FIGS. 5 and 6, a module cover structure 390, which is coupled to and covers a lens module 330, comprises at least one first stray light blocking portion 391 for blocking stray light radiated from the light source(s) 300 from entering the sensor 360; at least one lens module coupling portion 392 into each of which an illumination optical system 310 of the lens module 330 is coupled; an object plane 340 on which an object to be imaged is placed; and optionally at least one module cover foot 393 for coupling to a PCB 380.

[53] A module cover structure 390 in accordance with the invention is made of opaque material to prevent external stray light from entering the module cover structure 390 and impairing the operation of an optical structure.

[54] A module cover structure 390 in accordance with the invention integrally comprises at least one first stray light blocking portion 391 and optionally at least one module cover foot 393.

[55] FIGS. 7 and 8 are perspective views of a lens module according to an embodiment of the invention. Referring to FIGS. 7 and 8, a lens module 330 in accordance with the invention comprises at least one illumination optical system 310 for directing light rays radiated from a light source 300; an imaging lens system 320 for focusing the light reflected from an object placed on an object plane 340 onto a sensor 360; at least one assembly hole 332 for coupling with a sensor cover module 370; and optionally at least one lens module foot for coupling to a PCB 380. The imaging lens system 320 comprises an imaging lens 321 for focusing the light reflected from an object placed on an object plane 340 onto the sensor.

[56] A lens module 330 in accordance with the invention integrally comprises at least one illumination optical system 310, an imaging lens system 320, and optionally at least one lens module foot 331.

[57] FIGS. 9 and 10 are perspective views of a sensor cover module according to an embodiment of the invention. Referring to FIGS. 9 and 10, a sensor cover module 370 in accordance with the invention comprises at least one second stray light blocking portion 372 for blocking stray light radiated from the light source(s) 300 from entering the sensor 360; an aperture portion 371 for regulating the amount of light admitted to the sensor 360; at least one complementary stray light blocking portion 374 for complementing the stray light blocking function of the first stray light blocking portion(s) 391; and optionally at least one sensor cover module foot 373 for coupling to a PCB 380. [58] A sensor cover module 370 in accordance with the invention integrally comprises at least one second stray light blocking portion 372, at least one complementary stray light blocking portion 374, and optionally at least one sensor cover module foot 373.

[59] Referring to FIGS. 7 through 10, a sensor cover module 370 in accordance with the invention is disposed beneath illumination optical systems 310, 310' and an imaging lens system 320 to block external light from entering the sensor 360. Being lighttight except for an aperture portion 371, the sensor cover module 370 regulates the amount of light admitted to, and protects the sensor.

[60] A sensor cover module 370 according to the invention integrally comprises optionally at least one sensor cover module foot 373 for coupling to a PCB 380 as well.

[61] An embodiment of a lens module according to the invention comprises a pair of assembly holes 332 formed between an imaging lens system 320 and a first/second illumination optical system 310, 310', respectively, for coupling with a sensor cover module 370. A pair of opaque second stray light blocking portions 372 provided in the sensor cover module 370 are inserted through the pair of assembly holes 332, thus effectively coupling the two modules and preventing light radiated from the illumination optical systems 310, 310' from being directly admitted to the imaging lens system 320.

[62] The coupling of the sensor cover module 370 and the lens module 330 may involve application of epoxy or other adhesives. Such coupling of the sensor cover module 370 and the lens module 330 provides an airtight and lighttight structure including the optical aperture portion, thereby forming a stray light blocking structure together with a module cover structure 390 as well as protecting the sensor from dust or moisture.

[63] The lens module 330, which comprises the illumination optical systems 310, 310' and the imaging lens system 320, integrally comprises optionally at least one lens module foot 331 for mounting onto the PCB 380. Having a variety of functional components in one integrated structure, the lens module 330 is preferably fabricated by injection molding.

[64] Fabrication of integrated micro-optic devices according to the invention is made simple and precise because one has only to insert the sensor cover module feet 373 and the lens module feet 331 into the PCB 380.

[65] FIG. 11 is a schematic cross-sectional view of an optical device according to the invention, such as shown in FIGS. 3 and 4, taken along the illumination optical systems. FIG. 12 is a schematic cross-sectional view of an embodiment of an illumination optical system according to the invention. Referring to FIGS. 11 and 12, a sensor cover module 370 is mounted using at least one sensor cover module foot 373 on a PCB 380 on which a sensor 360 and light sources 300, 300' are mounted. The sensor cover module 370 is then assembled with a lens module 330 by inserting second stray light blocking portion(s) 372 formed in the former through assembly hole(s) 332 formed in the latter. The lens module 330 is then covered by a module cover structure 390 that blocks external light from entering the lens module 330.

[66] The following refers to a specific embodiment of the invention having a pair of light sources and illumination optical systems.

[67] A first illumination optical system 310 comprises three optical surfaces for collimating, directing, and focusing light rays radiated from a first light source 300 toward an object plane 340.

[68] A second illumination optical system 310' has the same structure and function as the first illumination optical system 310. The first and second illumination optical systems 310, 310' are aligned symmetrically referring an object plane 340 and constitute an integrated module together with an imaging lens system 320.

[69] The first illumination optical system 310 comprises an input lens 311 for collimating light radiated from the first light source 300; a reflector lens 312 for redirecting the parallel light rays transmitted via the input lens 311; and an output lens 313 for focusing the light reflected from the reflector lens 312 onto the object plane 340. Each of the lenses has a particular prism structure suited to their respective functions.

[70] In addition to their primary functions of beam forming, redirecting, and focusing, the input lens 311, the reflector lens 312, and the output lens 313 respectively condense diffusing light along imaginary axes x, y, and z linking the centers of the input lens 311, the reflector lens 312, the output lens 313, and the object plane 340, respectively.

[71 ] Each of the input lens 311, the reflector lens 312, and the output lens 313 of the first illumination optical system 310 can be of a spherical or aspheric globose, cylindrical, or toroidal shape.

[72] In transmitting light radiated from the first light source 300 to the object plane 340, the three lenses included in the first illumination optical system 310 respectively condense light rays, which would otherwise scatter randomly in all directions, thus minimizing stray light and problems associated with use of an LED chip as a light source. The consequent enhancement in optical efficiency reduces required intensity of radiation and thus power consumption.

[73] A sensor cover module 370 is made of opaque material and optically/electrically separates the bright light sources from a highly sensitive sensor. The sensor cover module 370 comprises a pair of second stray light blocking portions 372 integrated therewith for preventing light radiated from the light sources 300, 300' from affecting the sensor 360 directly. This protection is of critical importance because even a small amount of stray light directly incident to the imaging lens 321 would make it difficult to properly detect the light reflected from the object plane 340 having a much weaker intensity of radiation.

[74] FIG. 13 is a schematic cross-sectional view of an optical device according to the invention, such as shown in FIGS. 3 and 4, taken along the first stray light blocking portions. FIG. 13 illustrates a specific embodiment of the invention having a pair of light sources and illumination optical systems.

[75] The respective pairs of light sources 300, 300' and illumination optical systems

310, 310' are aligned symmetrically referring an object plane 340. Accordingly, a second stray light blocking portion is provided on each side.

[76] Stray light that cannot be blocked by the pair of second stray light blocking portions is blocked by a pair of first stray light blocking portions formed along an axis perpendicular to the one along which the second stray light blocking portions are placed.

[77] The first stray light blocking portions are integrally formed with a module cover structure in a convex shape toward a sensor presumed to be located in their lower direction. Providing such bent optical paths between an imaging lens and the exterior of a lens module, by forming the first stray light blocking portions in a convex shape, prevents stray light components from directly entering the sensor via the imaging lens. As illustrated in FIG. 13, stray light rays are attenuated as they hit the first stray light blocking portion.

[78] The portions of a sensor cover module corresponding to the first stray light blocking portions, that is, between the aperture portion and the outer edges, are also formed in a similarly concave shape toward the first stray light blocking portions respectively. The outer edges that are formed in a convex shape constitute complementary stray light blocking portions, which reduce the range of angles within which stray light can continue traveling toward the imaging lens.

[79] The portions of a lens module corresponding to the first stray light blocking portions may be fabricated by electrical discharge machining (EDM) or other precision machining techniques.

[80] Sensor cover modules and module cover structures are made of antireflective, preferably black, material such as optical glass, PMMA (polymethyl methacrylate), PC (polycarbonate), or acetal resin. Sensor cover modules and module cover structures are preferably roughened by EDM or sandblasting to allow the roughened surfaces to better absorb and scatter the stray light.

[81] FIG. 14 is a graph illustrating the intensity of illumination on an object plane according to an example of the present invention. As illustrated in FIG. 14, the intensity of illumination on the object plane 340 varies relative to the distance from the first/second light source 300, 300' to the target spot.

[82] Curve A of FIG. 14 represents the intensity of illumination relative to the distance from the center of the object plane 340 for the light transmitted from the first light source 300 via the first illumination optical system 310.

[83] As shown in the graph, the intensity of illumination is higher on spots closer to the first illumination optical system 310, that is, on the left of the central point 0.0 of the object plane 340 than on spots farther away from the first light source 300.

[84] Hence, a second illumination optical system 310' is disposed opposite the first illumination optical system 310 to obtain approximate uniformity in the intensity of illumination on the object plane 340.

[85] Spots on the object plane 340 farther away from the second illumination optical system 310' with lower illuminance correspond to spots closer to the first illumination optical system 310 with higher illuminance, and vice versa. Thus, the combined illuminance is approximately uniform over the entire object plane 340.

[86] This uniform illumination of the object plane through a pair of illumination optical systems allows for uniform illumination of the sensor as well and thus contributes to maximizing the optical efficiency of an optical device according to the invention.

[87] FIG. 15 is a schematic diagram illustrating a configuration of light sources according to an embodiment of the invention. FIG. 16 illustrates an alternative configuration according to another embodiment of the invention. As shown in FIGS. 15 and 16, an optical device in accordance with the invention preferably comprises two or more illumination optical systems to ensure a uniform illumination of the object plane.

[88] If there are two illumination optical systems as illustrated in FIG. 11, the illumination optical systems 310, 310' are placed symmetrically referring the imaging lens 321. If there are three illumination optical systems, each illumination optical system is spaced equiangularly around the imaging lens.

[89] It is preferable that an optical device embodiment with a plurality of illumination optical systems have the same number of light sources so as to assign one to each.

[90] An optical device embodiment having a plurality of illumination optical systems but only one light source may offer the same functionality as one with the same number of light sources by supplying light from the single light source to each of the plurality of illumination optical systems through fiber-optic transmission.

[91] Optical device embodiments in accordance with the invention structurally prevent typical problems associated with prior art slim/micro optical devices, such as inadequate quality of illumination and the imaging system's exposure to direct/indirect stray light leading to sensor malfunction. Low-cost fabrication is made possible because a sensor cover module, a lens module, and a module cover structure are mono- lithically fabricated.

[92] Accordingly, micro-optic embodiments in accordance with the invention are applicable to mini pointing/input devices.

[93] Being free from illumination quality or stray light problems even when miniaturized, the invention is effectively applicable to mini fingerprint sensing devices for providing a higher standard of security for PCs and portable electronic devices.

[94] The invention is further applicable to slim/micro pointing/input devices for integration into wireless input devices in the form of a watch, ring, button, or the like.

[95] Micro-optic devices according to the invention can be built into notebook PCs or tablet PCs, or attached to wired/wireless keyboard devices as a high-performance mini pointing device.

[96] The invention is also well suited for implementation in miniaturized pointing/input devices for replacing the navigation keys or adding pointing/input functionality in a variety of devices, including portable gaming devices.

[97] In addition, the invention may help enhance the functionality of remote control devices for home network environments.

[98] The invention may also help enhance the functionality and reliability of kiosks and other public access devices.

[99] Although specific embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions, and substitutions are possible without departing from the concept and scope of the invention as disclosed in the accompanying claims.

Claims

[1] An integrated micro-optic device, comprising: at least one light source that radiates light; a transparent lens module comprising at least one illumination optical system through which the radiated light is transmitted and an imaging lens system for focusing the light reflected from an object plane onto a sensor; an opaque module cover structure which houses said lens module and comprises at least one first stray light blocking portion disposed between said at least one light source and said sensor for blocking stray light radiated from said light source(s) from entering said sensor; and an opaque sensor cover module which is assembled beneath said lens module and comprises at least one second stray light blocking portion disposed between said at least one light source and said sensor for blocking stray light radiated from said light source(s) from entering said sensor.

[2] The integrated micro-optic device of claim 1, wherein: said at least one illumination optical system and said imaging lens system are integrally formed with said lens module; said at least one first stray light blocking portion is integrally formed with said module cover structure; and said at least one second stray light blocking portion is integrally formed with said sensor cover module.

[3] The integrated micro-optic device of claim 2, wherein said at least one first stray light blocking portion is formed in a top interior portion of said module cover structure such that a projection is formed between said object plane and the top interior edge of said module cover structure to thereby block stray light radiated from said light source(s).

[4] The integrated micro-optic device of claim 3, wherein the top exterior of said sensor cover module is formed such that a shallow U shape is formed between the top exterior edge and an aperture portion of said sensor cover module.

[5] The integrated micro-optic device of claim 4, wherein the top of said lens module is formed such that a shallow U shape is formed between an imaging lens and the top edge of said lens module.

[6] The integrated micro-optic device of claim 5, wherein the portion between said imaging lens and said top edge of said lens module constitutes a stray light blocking structure fabricated by electrical discharge machining (EDM) or other precision machining techniques.

[7] The integrated micro-optic device of claim 5, wherein said sensor cover module and said module cover structure are made of optical glass, PMMA, PC, or acetal resin capable of blocking stray light.

[8] The integrated micro-optic device of claim 5, wherein the method of fabricating said sensor cover module and said module cover structure for added stray light blocking capability involves EDM or sandblasting.