WO2007114587A1

WO2007114587A1 - Integrated micro-optic device

Info

Publication number: WO2007114587A1
Application number: PCT/KR2007/001544
Authority: WO
Inventors: Sung-Chul Juh
Original assignee: Mobisol Inc.
Priority date: 2006-03-30
Filing date: 2007-03-29
Publication date: 2007-10-11

Abstract

The present invention relates to an integrated micro-optic device capable of preventing light rays radiated from a light source from being scattered and directly reaching a sensor and providing enhanced optical efficiency, manufacturability, and cost reduction through an integrated illumination optical system. The integrated micro-optic device in accordance with the invention comprises at least one light source; at least one illumination optical system for condensing light rays onto an object plane; an imaging lens system, which is integrally formed with the illumination optical system(s), for condensing the light reflected from the object plane onto a sensor; and a sensor cover module, which is assembled together with the illumination optical system(s) and the imaging lens system, for limiting the amount of light admitted to the sensor.

Description

Description INTEGRATED MICRO-OPTIC DEVICE

Technical Field

[1] The present invention relates, in general, to an integrated micro-optic device and, in particular, to an integrated micro-optic device capable of preventing light rays radiated from a light source from being scattered and directly reaching a sensor and providing enhanced optical efficiency, manufacturability, and cost reduction through an integrated illumination optical system.

[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 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, 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 application 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]

Disclosure of Invention

Technical Problem

[13] An embodiment of the present invention is directed to an integrated micro-optic device capable of preventing light rays radiated from a light source from being scattered and directly reaching a sensor.

[14] Another embodiment of the invention pertains to an integrated micro-optic device comprising at least two illumination optical systems to counterbalance the different intensity of illumination relative to the distance from each light source and thus ensure a uniform illuminance.

[15] Yet another embodiment of the invention concerns an integrated micro-optic device comprising a sensor cover module, which is airtight except for an aperture, for protecting and limiting the amount of light admitted to the sensor.

[16] Still another embodiment of the invention relates to an integrated micro-optic device allowing for modular assembly of an integrated lens module and a sensor cover module onto a PCB, thus enhancing manufacturability and minimizing defects.

[17]

Technical Solution

[18] An embodiment of an integrated micro-optic device in accordance with the present invention comprises at least one light source; at least one illumination optical system for condensing light rays onto an object plane; an imaging lens system, which is integrally formed with the illumination optical system(s), for condensing the light reflected from the object plane onto a sensor; and a sensor cover module, which is assembled together with the illumination optical system(s) and the imaging lens system, for limiting the amount of light admitted to the sensor. [19]

Advantageous Effects

[20] An embodiment of a lens module in accordance with the present invention comprises at least one illumination optical system comprising three lenses to collimate, direct, and focus light rays radiated from a light source toward an object plane. [21] A preferred embodiment according to the invention comprises a plurality of illumination optical systems for uniform illumination of the object plane. [22] The illumination optical system minimizes stray light and problems associated with use of an LED chip as a light source. In addition, enhanced optical efficiency reduces required intensity of radiation and thus power consumption. [23] An embodiment of a sensor cover module in accordance with the invention prevents stray light from being admitted to a sensor. [24] Being airtight except for an aperture, the sensor cover module protects and limits the amount of light admitted to the sensor. [25] An embodiment of an integrated micro-optic device in accordance with the present invention allows for modular assembly of the lens module and the sensor cover module onto a PCB, thus enhancing manufacturability and minimizing defects. [26]

Brief Description of the Drawings

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

[28] 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; [29] FIG. 3 is a cross-sectional view of an optical device according to an embodiment of the invention; [30] FIG. 4 is a perspective view of a lens module according to an embodiment of the invention; [31] FIG. 5 is a perspective view of a sensor cover module according to an embodiment of the present invention; [32] FIG. 6 is a cross-sectional view of an optical device according to another embodiment of the invention; [33] FIG. 7 is a cross-sectional view of an illumination optical system according to an embodiment of the invention; [35] FIG. 8 is a perspective view of a lens module according to another embodiment of the invention;

[36] FIG. 9 is a perspective view of a sensor cover module according to another embodiment of the invention;

[37] FIG. 10 is a graph illustrating the intensity of illumination on an object plane according to one example of the invention;

[38] FIG. 11 is a schematic diagram illustrating a configuration of light sources according to an embodiment of the invention; and

[39] FIG. 12 is a schematic diagram illustrating a configuration of light sources according to another embodiment of the invention.

[40]

[41] <Description of reference numerals>

[42] 100, 230: LED 110: optical system 120: object surface

[43] 200: first lens plane 210: reflective surface 220: sensor

[44] 240: second lens plane 300, 300': light source 310, 310': illumination optical system

[45] 311: input lens 312: reflector lens 313: output lens

[46] 320: imaging lens system 321: imaging lens 330: lens module

[47] 331: lens module foot 332: assembly hole 340: object plane

[48] 350: lens protection structure 360: sensor 370: sensor cover module

[49] 371: aperture portion 372: stray light shield 373: sensor cover module foot

[50] 380: PCB

[51]

Mode for the Invention

[52] 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.

[53] 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.

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

[55] FIG. 3 is a cross-sectional view of an optical device according to an embodiment of the present invention. FIG. 4 is a perspective view of a lens module according to an embodiment of the present invention. FIG. 5 is a perspective view of a sensor cover module according to an embodiment of the present invention. Referring to FIGS. 3 to 5, the optical device according to an embodiment of the present invention comprises a lens module 330 for modulating and directing light rays radiated from a light source 300; an object plane 340 on which an object to be imaged is placed; a lens protection structure 350 for protecting the lens module 330; a sensor 360 for sensing light reflected from the object placed on the object plane 340; and a sensor cover module 370 for protecting and limiting the amount of light admitted to the sensor 360.

[56] FIG. 6 and FIGS. 8 to 10 illustrate an optical device according to another embodiment of the invention, which comprises at least two illumination optical systems to counterbalance the different intensity of illumination relative to the distance from each light source and thus ensure a uniform illuminance.

[57] FIG. 6 is a cross-sectional of an optical device according to another embodiment of the present invention. FIG. 7 is a cross-sectional view of an illumination optical system according to an embodiment of the present invention.

[58] The optical device according to another embodiment of the present invention comprises a pair of illumination optical systems 310, 310' for modulating and directing light rays radiated from a pair of light sources 300, 300', respectively; a lens protection structure 350 for physical protection of the illumination optical systems 310, 310'; an object plane 340 on which an object to be imaged is placed; an imaging lens system 320 for focusing light reflected from the object placed on the object plane 340 onto a sensor 360 for sensing said reflected light; and a sensor cover module 370 for protecting and limiting the amount of light admitted to the sensor 360.

[59] When a plurality of light sources are 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.

[60] When an optical device comprises a plurality of illumination optical systems but only one light source, light can be supplied to the respective input lenses of the plurality of illumination optical systems through optical fibers.

[61] The first illumination optical system 310 comprises three optical surfaces for collimating, directing, and focusing light rays radiated from the first light source 300 toward the object plane 340.

[62] The 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' face the object plane 340 from opposite directions and constitute an integrated module together with the imaging lens system 320.

[63] 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.

[64] 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 light components diffusing away from 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.

[65] 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, aspheric, cylindrical, or toroidal shape.

[66] 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.

[67] The imaging lens system 320 comprises an imaging lens 321 for condensing the light reflected from the object placed on the object plane 340 onto the sensor 360.

[68] The sensor cover module 370 is made of opaque material and optically/electrically separates the bright light sources 300, 300' from the highly sensitive sensor 360. The sensor cover module 370 comprises a pair of stray light shields 372 integrated therewith for preventing light radiated from the light sources 300, 300' from affecting the sensor 360 directly.

[69] 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.

[70] The method of attaching the sensor 360 to the PCB includes, but is not limited to, wire bonding and flip chip technologies.

[71] FIG. 8 is a perspective view of the lens module according to another embodiment of the present invention. FIG. 9 is a perspective view of the sensor cover module according to another embodiment of the present invention.

[72] The sensor cover module 370 is disposed beneath the illumination optical systems

310, 310' and the imaging lens system 320 so as to preclude direct incidence of light onto the sensor 360. Being airtight except for an aperture portion 371, the sensor cover module 370 protects and limits the amount of light admitted to the sensor. [73] The sensor cover module 370 comprises integrally formed feet 373 for coupling to a

PCB 380.

[74] The lens module 330 has a pair of assembly holes 332 formed respectively between the imaging lens system 320 and the first/second illumination optical system 310, 310'. A pair of stray light shields 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. The coupling of the sensor cover module 370 and the lens module 330 may involve application of epoxy or other adhesives.

[75] The lens module 330, which comprises the illumination optical systems 310, 310' and the imaging lens system 320, has integral lens module feet 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.

[76] 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.

[77] FIG. 10 is a graph illustrating the intensity of illumination on an object plane according to an example of the present invention. As illustrated in FIG. 10, 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.

[78] Curve A of FIG. 10 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.

[79] 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.

[80] 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.

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

[82] This uniform illumination of the object plane 340 through a pair of illumination optical systems 310, 310' 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. [83] FIG. 11 is a schematic diagram illustrating a configuration of light sources according to an embodiment of the invention. FIG. 12 illustrates an alternative configuration according to another embodiment of the invention. As shown in FIGS. 11 and 12, 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 340.

[84] If there are two illumination optical systems as illustrated in FIG. 6, the illumination optical systems 310, 310' are placed such that they face the imaging lens 321 from opposite directions. If there are three illumination optical systems, each illumination optical system is spaced apart at an angle of 120° from each other around the imaging lens. Use of four or more illumination optical systems, of course, should further improve the uniformity of illumination.

[85] Such plurality of illumination optical systems are thus preferably placed at a uniform distance from and spaced equiangularly around the object plane, or the imaging lens for that matter.

[86] 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.

[87] 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.

[88] Optical device embodiments in accordance with the invention structurally prevent typical problems associated with prior art slim/micro 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 lens modules and sensor cover modules are monolithically fabricated, respectively.

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

[90] 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.

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

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

[93] 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. [94] The invention may help enhance the functionality of remote control devices for home network environments. [95] The invention may also help enhance the functionality and reliability of kiosks and other public access devices. [96] 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; at least one illumination optical system for focusing the radiated light onto an object plane; an imaging lens system, which is integrally formed with the illumination optical system(s), for condensing the light reflected from the object plane on a sensor; and a sensor cover module, which is assembled together with the illumination optical system(s) and the imaging lens system, for regulating the amount of light admitted to the sensor.

[2] The integrated micro-optic device of claim 1, wherein the sensor cover module comprises: at least one integrally-formed stray light shield for preventing scattered light from the light source from entering the sensor; and at least one integrally-formed sensor cover module foot for the mounting of the sensor cover module onto a PCB.

[3] The integrated micro-optic device of claim 2, wherein the stray light shield(s) is/ are inserted into (an) assembly hole(s) formed between the illumination optical system(s) and the imaging lens system.

[4] The integrated micro-optic device of claim 3, wherein the number of stray light shields is the same as the number of light sources.

[5] The integrated micro-optic device of any one of claims 1 to 4 comprising at least two illumination optical systems, wherein the plurality of illumination optical systems are placed at a uniform distance from and spaced equiangularly around the object plane.

[6] The integrated micro-optic device of claim 5, wherein each of the illumination optical systems comprises: an input lens for collimating light radiated from the light source; a reflector lens for redirecting the parallel light rays transmitted via the input lens toward the object plane; and an output lens for condensing the light transmitted via the reflector lens onto the object plane.

[7] The integrated micro-optic device of claim 6, wherein each of the input lens, the reflector lens, and the output lens has a transparent prism structure.

[8] The integrated micro-optic device of claim 6, wherein each of the input lens, the reflector lens, and the output lens is of a spherical, aspheric, cylindrical, or toroidal shape.

[9] The integrated micro-optic device of any one of claims 1 to 4, further comprising at least one optical fiber for transmitting light from the light source to the illumination optical system(s).

[10] The integrated micro-optic device of any one of claims 1 to 4, wherein the light source is a slim LED, laser diode, or infrared diode chip.

[11] A wired optical mouse employing the integrated micro-optic device according to any one of claims 1 to 4.

[12] A wireless optical mouse employing the integrated micro-optic device according to any one of claims 1 to 4.

[13] A built-in pointing device of a notebook computer employing the integrated micro-optic device according to any one of claims 1 to 4.

[14] A pointing device for a portable electronic device employing the integrated micro-optic device according to any one of claims 1 to 4.

[15] A pointing device for a remote control device employing the integrated micro- optic device according to any one of claims 1 to 4.

[16] A built-in pointing device of a kiosk employing the integrated micro-optic device according to any one of claims 1 to 4.

[17] A fingerprint sensing device employing the integrated micro-optic device according to any one of claims 1 to 4.