WO2013141649A1

WO2013141649A1 - Light emitting unit array and light diffusing lens suitable for the same

Info

Publication number: WO2013141649A1
Application number: PCT/KR2013/002402
Authority: WO
Inventors: Eun Ju Kim; Dae Sung Cho
Original assignee: Seoul Semiconductor Co., Ltd.
Priority date: 2012-03-23
Filing date: 2013-03-22
Publication date: 2013-09-26

Abstract

A light emitting unit array comprises: a plurality of light emitting units arranged under a target surface in a matrix form. Each of the light emitting units comprises a light diffusing lens with a central axis and an LED disposed under the light diffusing lens. The light emitting units form light patterns having different illuminance distributions in at least one direction from the central axis. Each of the light patterns comprises a central region and peripheral regions having an illuminance lower than that of the central region. The central region depends on a single light pattern. A plurality of light patterns overlap one another in each of the peripheral regions. Therefore, it is possible to provide a uniform illuminance distribution as a whole.

Description

LIGHT EMITTING UNIT ARRAY AND LIGHT DIFFUSING LENS SUITABLE FOR THE SAME

The present invention relates generally to a light emitting unit array and a light diffusing lens suitable for the same, and more particularly, to a light emitting unit array suitable for surface illumination or backlighting for a liquid crystal display.

A direct type backlight unit comprises a plurality of LEDs arranged under a substantial flat type object, such as a liquid crystal panel or a light diffusion plate, at regular intervals, and illuminates the corresponding object. The direct type backlight unit has been used for surface illumination or backlighting for a liquid crystal display. In order to uniformly illuminate the object by using the plurality of LEDs alone, it is necessary to densely arrange a large number of LEDs, leading to an increase in power consumption. Furthermore, when there is a deviation in the quality of the LEDs, the object is non-uniformly backlit. In order to reduce the number of LEDs used, technique for mounting a light diffusing lens on each LED to disperse light may be used. In this technique, a light diffusing lens and at least one LED corresponding thereto constitute one light emitting unit.

A conventional light diffusing lens has a structure in which both of a light incident portion and a light emission portion are axis-symmetric with respect to a central axis. As illustrated in FIG. 1, a light emitting unit using such a light diffusing lens along with an LED forms a circular light pattern Lp on a target surface. When a large number of light emitting units are disposed under the target surface at regular intervals, bright portions Wp in which lights intersect with each other are formed between two adjacent light-orientation patterns Lp on the target surface, and dark portions Bp in which lights are hardly illuminated are formed between four adjacent light-orientation patterns Lp on the target surface.

In addition, in order to reduce such dark portions and increase uniformity of illuminance, light emitting units including light diffusing lenses may be arranged. However, in this case, it is difficult to control an illuminance distribution in the edges of light patterns generated by the light emitting units.

An aspect of the present invention is directed to a light emitting unit array capable of providing a uniform illuminance distribution on a target surface.

Another aspect of the present invention is directed to a light diffusing lens capable of contributing to a uniform illuminance distribution on a target surface when applied to each light emitting unit of a light emitting unit array.

According to an embodiment of the present invention, a light emitting unit array comprises: a plurality of light emitting units arranged under a target surface in a matrix form, wherein each of the light emitting units comprises a light diffusing lens with a central axis and an LED disposed under the light diffusing lens, the light emitting units form light patterns having different illuminance distributions in at least one direction from the central axis, each of the light patterns comprises a central region and peripheral regions having an illuminance lower than that of the central region, the central region depends on a single light pattern, and a plurality of light patterns overlap one another in each of the peripheral regions.

According to another embodiment of the present invention, there is provided a light diffusing lens suitable for each light emitting unit of a light emitting unit array, wherein the light diffusing lens receives light from an LED and forms light patterns having different illuminance distributions in at least one direction with respect to a central axis, each of the light patterns comprises a central region and peripheral regions each having an illuminance lower than that of the central region, the central region depends on a single light pattern, and a plurality of light patterns overlaps one another in each of the peripheral regions.

According to the present invention, a substantially uniform illuminance distribution can be provided on a target surface by an array of light emitting units that form axis-asymmetric light patterns on the target surface by using axis-asymmetric light diffusing lenses, achieving the implementation of surface illumination or liquid crystal displays having a uniform illuminance distribution.

In addition, according to the present invention, a substantially uniform illuminance distribution can be provided on a target surface by an array of light emitting units that form elongated light patterns in a single-axis direction, achieving the implementation of surface illumination or liquid crystal displays having a uniform illuminance distribution.

Furthermore, the light diffusing lens according to the present invention can provide a uniformly widely diffused light distribution by effectively widely diffusing light being within a range of 60 degrees from an optical axis when a light incident portion is formed adjacent to an LED, without concave portions, in an upper center of a light emission surface. In this case, the omission of the concave portion makes it possible to more easily design and manufacture a light diffusing lens and to minimize the failure of the light diffusing lens caused by defects on the concave portion.

FIG. 1 is a diagram for describing the prior art.

FIG. 2 is a conceptual diagram for describing the formation of light patterns on a predetermined target surface by light emitting units according to the present invention.

FIG. 3 is a diagram for describing a light emitting unit array including the light emitting units of FIG. 2, and the overall light patterns formed by the light emitting unit array.

FIGS. 4a and 4b are diagrams, respectively, illustrating a light pattern illuminance distribution and an orientation angle distribution of a conventional single light emitting unit having an axis-symmetric structure.

FIGS. 5a and 5b are diagrams, respectively, illustrating a light pattern illuminance distribution and an orientation angle distribution of a single light emitting unit according to the present invention, which has a 90-degree rotational symmetric and axis-asymmetric structure.

FIGS. 6a and 6b are diagrams, respectively, illustrating the illuminance distribution of the overall light patterns when the conventional light emitting units each having the illuminance distribution and light-orientation distribution illustrated in FIG. 4a and 4b are regularly arranged, and the illuminance distribution of the overall light patterns when the conventional light emitting units are irregularly arranged.

FIG. 7 is a diagram illustrating the illuminance distribution of a light emitting unit array in which the light emitting units of FIG. 5 according to the embodiment are arranged with twenty-five sets.

FIG. 8 is a plan view illustrating a first embodiment of a light emitting unit applicable to the light emitting unit array according to the present invention.

FIG. 9 is a cross-sectional view of the light emitting unit of FIG. 8, taken along x axis.

FIGS. 10a, 10b and 10c are cross-sectional views taken along lines a-a, b-b and c-c of FIG. 9.

FIG. 11 is a perspective view illustrating an LED of the light emitting unit according to the embodiment of the present invention.

FIG. 12 is a bottom view of a light diffusing lens according to a second embodiment of the present invention.

FIG. 13 is a conceptual diagram for describing the formation of light patterns on a predetermined target surface by the light emitting units according to the present invention.

FIG. 14 is a diagram for describing a light emitting unit array including the light emitting units of FIG. 13, and the overall light patterns formed by the light emitting unit array.

FIGS. 15a and 15b are diagrams, respectively, illustrating a light pattern illuminance distribution and an orientation angle distribution of a single light emitting unit according to the present invention, which has a 180-degree rotational symmetric and axis-asymmetric structure.

FIG. 16 is a perspective view illustrating a third embodiment of a light emitting unit applicable to the light emitting unit array according to the present invention.

FIG. 17a is a cross-sectional view of the light emitting unit of FIG. 16, taken along a major-axis (y) direction, and FIG. 17b is a cross-sectional view of the light emitting unit of FIG. 16, taken along a minor-axis (x) direction.

FIGS. 18 to 21 are diagrams for describing embodiments of a light incident portion applicable to the light diffusing lens of the light emitting unit according to the present invention.

FIG. 22 is an exploded perspective view for describing a light emitting unit according to a fourth embodiment of the present invention.

FIGS. 23a and 23b are cross-sectional views, respectively, taken along two directions which intersect the light emitting unit illustrated in FIG. 22.

FIG. 24 is a cross-sectional view of a light emitting unit according to a fifth embodiment of the present invention.

FIGS. 25Aa, 25Bb and 25c are cross-sectional views taken along lines a-a, b-b and c-c of FIG. 24.

FIG. 26 is a detailed diagram for describing the light diffusing lens of the light emitting unit illustrated in FIG. 24.

FIG. 27 is a diagram illustrating a light orientation angle distribution when using the light diffusing lens illustrated in FIG. 26.

FIG. 28 is a diagram for describing a light diffusing lens according to a sixth embodiment of the present invention.

FIG. 29 is a diagram illustrating a light orientation angle distribution available using the light diffusing lens of FIG. 28.

FIGS. 30a and 30b are diagrams, respectively, illustrating a light diffusing lens and an orientation angle distribution according to a first comparative example.

FIGS. 31a and 31b are diagrams, respectively, illustrating a light diffusing lens and an orientation angle distribution according to a second comparative example.

Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. In the drawings, the widths, lengths and thicknesses of elements may be exaggerated for clarity. Throughout the drawings and description, like reference numerals will be used to refer to like elements.

FIG. 2 conceptually illustrates light patterns that can be formed on a predetermined target surface by light emitting units according to the present invention. Each light emitting unit 1 includes an LED and a light diffusing lens. The light emitting unit 1 forms a light pattern with a substantially square shape, which is 90-degree rotational symmetric and axis-asymmetric with respect to the central axis of the light diffusing lens, on a predetermined target surface. In the light pattern, illuminance distributions in x-axis and y-axis directions intersecting each other are identical to each other, and illuminance distribution in a 45-degree diagonal-axis direction is different from the illuminance distribution in x-axis and y-axis directions. In this case, the x-axis, y-axis and diagonal-axis are located on a virtual plane which is perpendicular to the center of a light diffusing lens, and the diagonal-axis is located between x-axis and y-axis on the plane.

Although FIG. 2 illustrates that the light emitting unit and its light pattern are the perfect square, an actual light pattern may have a rounded square or a similar shape thereto.

The light pattern Lp is divided into nine regions according illuminance, to which reference symbols Ao1, Ax2, Ay2 and Az3 are assigned. Ao1 indicates the central region of the square, which has the highest illuminance or light intensity, Ax2 indicates a pair of first lateral regions, which are symmetric to each other in the x-axis direction with respect to the central region Ao1, and Ay2 indicates a pair of second lateral regions, which are symmetric to each other in the y-axis direction with respect to the central region Ao1. The illuminance of each of the first lateral regions Ax2 is identical to that of each of the second lateral regions Ay2. Az3 indicates four corner regions which are symmetric to each other in the 45-degree diagonal-axis direction with respect to the central region Ao1. The illuminance of the corner regions Az3 is lowest.

FIG. 3 illustrates the light emitting unit array in which the light emitting units 1 are arranged in two rows and two columns. A light emitting unit array including more light emitting units arranged in N rows and n columns (where N and n are integers equal to or greater than 2) falls within the scope of the present invention. For the sake of convenience, the light emitting unit array including light emitting units arranged in two rows and two columns will be described as an example.

Each of the light emitting units 1 includes an LED and a light diffusing lens. In this case, four light patterns Lp are formed by the four light emitting units 1 on a predetermined target surface spaced apart a certain distance from the light emitting unit in a vertical direction. The central region Ao1 of the light pattern by the single light emitting unit 1 has illuminance dependent on the light from the corresponding light emitting unit 1 by at least 90%, ideally 100%, without overlapping the light pattern of another light emitting unit. In addition, the light patterns of two adjacent light emitting units are overlapped in the two first lateral regions Ax2. Due to the overlapping of the light patterns, the illuminance in the two first lateral regions Ax2 may be almost identical to the illuminance in the central region Ao1. In addition, the light patterns of the two adjacent light emitting units are overlapped in the two second lateral regions Ay2. Due to the overlapping of the light patterns, the illuminance in the two second lateral regions Ay2 may be almost identical to the illuminance in the central region Ao1. In addition, the light patterns of the four light emitting units are overlapped in the four corner regions Az3. Due to the overlapping of the light patterns, the illuminance in each of the four corner regions Az3 may be identical to the illuminance in the central region Ao1.

The individual light patterns formed by the above-described light emitting units 1 constitute one large integrated light pattern on the predetermined target surface without gaps therebetween. Also, in the integrated light pattern, the respective central regions, the respective first and second lateral regions, the respective corner regions have the identical or similar illuminance. Therefore, the overall light pattern on the predetermined target surface has a substantially uniform illuminance distribution.

The uniform illuminance distribution corresponds to a case where light uniformity is equal to or greater than 70% in the absence of a diffusion plate, and corresponds to a case where light uniformity is equal to or greater than 80% in the presence of a diffusion plate.

Since the light patterns Lp having the substantial square shape are arranged, it is possible to prevent or minimize the formation of dark portions or relatively brighter portions in such a manner that the lateral regions or corner regions of the light pattern are overlapped with the adjacent lateral regions or corner regions. Therefore, it is possible to more easily implement a surface light source or a direct type backlight unit having a uniform illuminance on a predetermined target surface.

FIGS. 4a and 4b are diagrams, respectively, illustrating a light pattern illuminance distribution and an orientation angle distribution of a conventional single light emitting unit having an axis-symmetric structure. FIGS. 5a and 5b are diagrams, respectively, illustrating a light pattern illuminance distribution and an orientation angle distribution of a single light emitting unit according to the present invention, which has a 90-degree rotational symmetric and axis-asymmetric structure.

First of all, referring to FIG. 4a, in the case of using a conventional light emitting unit including an axis-symmetric lens, circular light patterns having illuminance distribution symmetric in all axis-directions on the same plane perpendicular to the above-described central axis are formed on a target surface. Although FIG. 4A illustrates only the x-axis direction and the y-axis direction among the all axis-directions, it can be easily understood that the circular light patterns have the illuminance distributions symmetric in the all axis-directions, and the light patterns are axis-symmetric with respect to the central axis thereof. In addition, referring to FIG. 4b, an orientation angle distribution pattern having a peak light intensity at about 78 degrees from the central axis thereof can be seen. The orientation angle distribution pattern is equal in all axis-directions on the same plane perpendicular to the central axis. That is, when the conventional light emitting unit is used, the orientation angle distribution pattern is always equal regardless of axis directions.

Next, referring to FIG. 5a, in the case of using a conventional light emitting unit including a light diffusing lens which is 90-degree rotational symmetric and axis-asymmetric with respect to a central axis, an illuminance distribution in x-axis direction illustrated on the left side of FIG. 5a among the axes on the same plane perpendicular to the central axis of the light diffusing lens is different from an illuminance distribution in an 45-degree diagonal-axis direction illustrated on the right side of FIG. 5b. Although not illustrated, an illuminance distribution in the y-axis direction is identical to the illuminance distribution in the x-axis direction. Therefore, the substantial square light pattern having the same illuminance distribution in the x-axis direction and the y-axis direction and different illuminance distributions in the diagonal-axis directions is formed on the target surface.

In addition, referring to FIG. 5b, two light orientation angle distribution patterns having different peak light intensities can be seen. The pattern having the smaller peak light intensity of the two light orientation angle distribution patterns is the light orientation angle distribution pattern of the x-axis and y-axis directions, and the pattern having the greater peak light intensity of the two light orientation angle distribution patterns is the light orientation angle distribution pattern of the 45-degree diagonal-axis direction. The two light orientation angle distribution patterns all have the peak light intensity at about 70 degrees. Referring to FIG. 5a, in the case of using the light diffusing lens which is 90-degree rotational symmetric and axis-asymmetric, the light orientation angle distribution patterns in the x-axis and y-axis directions are identical to each other, and the light orientation angle distribution pattern in the 45-degree diagonal-direction is different from the light orientation angle distribution patterns in the x-axis and y-axis directions.

FIG. 6a illustrates the illuminance distribution of the integrated light patterns when the conventional light emitting units each having the illuminance distribution and orientation angle distribution illustrated in FIG. 4a and 4b are regularly arranged, and FIG. 6b illustrates the illuminance distribution of the integrated light patterns when the conventional light emitting units each having the illuminance distribution and orientation angle distribution illustrated in FIG. 4a and 4b are irregularly arranged. FIG. 7 illustrates the illuminance distribution of a light emitting unit array in which the light emitting units of the present invention having the illuminance distribution of FIG. 5a and the orientation angle distribution of FIG. 5b are arranged with twenty-five sets.

Referring to FIG. 6a, the light patterns of the axis-symmetric light emitting units arranged regularly have a non-uniform illuminance distribution due to bright lines and dark regions formed on the target surface. Referring to FIG. 6b, it is possible to reduce bright lines and dark regions to some degree by irregularly arranging light emitting units that are axis-symmetric with respect to the central axis. However, there is a limit to the reduction of the bright lines and the dark regions, and it is difficult to control the edge illuminance of the integrated light patterns.

Referring to FIG. 7, the light emitting unit array according to the present invention can obtain a uniform illuminance distribution having almost no bright lines and dark regions through a specific arrangement of the light emitting units each including the light diffusing lens which is 90-degree rotational symmetric and axis-asymmetric with respect to the central axis, and their light patterns. Such uniform illuminance distribution can be obtained when each of the light emitting units constituting the light emitting unit array has the illuminance distribution and orientation angle distribution as illustrated in FIGS. 5a and 5b.

In addition, the uniform illuminance distribution by the light emitting unit array as described above can be obtained in such a manner that the illuminance of the central region of each of the light patterns, the illuminance of the lateral regions generated by the overlapping of two light patterns adjacent in the x-axis or y-axis direction, and the illuminance of the corner regions generated by the overlapping of the four light patterns are made to be substantially identical or similar to one another.

FIG. 8 is a plan view illustrating a first embodiment of a light emitting unit applicable to the light emitting unit array according to the present invention. FIG. 9 is a cross-sectional view of the light emitting unit of FIG. 8, taken along x axis. FIGS. 10a, 10b and 10c are cross-sectional views taken along lines a-a, b-b and c-c of FIG. 9. In this case, the line a-a is a cut line in a lower portion of the light diffusing lens, the line c-c is a cut line in an upper portion of the light diffusing lens, and the line b-b is a cut line in a middle height of the light diffusing lens between the line a-a and the line c-c. FIG. 11 is a perspective view illustrating an LED of the light emitting unit.

First, referring to FIGS. 8 and 9, the light emitting unit 1 is disposed on a printed circuit board 10, and includes an LED 20 and a light diffusing lens 30 disposed thereon. Although the printed circuit board 10 is partially illustrated such that a single light emitting unit is shown, four or more sets of light emitting units may be arranged on the single printed circuit board 10 in an Nxn matrix form.

The printed circuit board 10 includes conductive land patterns on the top surface thereof, in which terminals of the LED 20 are bonded to the conductive land patterns. In addition, the printed circuit board 10 may include a reflective film on the top surface thereof. The printed circuit board 10 may be a metal-core PCB (MCPCB) made of a metal having excellent thermal conductivity, or may be made of an insulating substrate material, such as FR4. Although not illustrated, a heat sink may be arranged under the printed circuit board 10 so as to dissipate heat generated from the LED 20. In addition, as illustrated in FIG. 8, the light diffusing lens 30 has a structure that is 90-degree rotational symmetric with respect to the central axis C thereof.

As illustrated in FIG. 11, the LED 20 may include a housing 21, an LED chip 23 mounted on the housing 21, and a wavelength conversion layer 25 covering the LED chip 23. The LED 20 may further include lead terminals (not illustrated) supported to the housing 21. Alternatively, the LED 20 may include an LED chip directly mounted on the printed circuit board, and a transparent encapsulating material for protecting the LED chip. The housing 21 may have a cavity 21a for mounting the LED chip 23. The cavity 21a defines a light emission portion of the LED 20. The wavelength conversion layer 25 covers the LED chip 23. In one embodiment, the wavelength conversion layer 25 may be formed by filling the cavity 21a with a phosphor-containing molding resin after the mounting of the LED chip 23. In this case, the wavelength conversion layer 25 may fill the cavity 21a of the housing 21 and have a substantially flat or convex top surface. Furthermore, a molding resin having a lens shape may be further applied on the wavelength conversion layer 25. In another embodiment, the LED chip 23, on which a conformal phosphor coating layer is formed, may be mounted on the housing 21. That is, the conformal phosphor coating layer may be applied on the LED chip 23, and the LED chip 23 with the phosphor coating layer may be mounted on the housing 21. The LED chip 23 with the conformal coating layer may be molded with a transparent resin. Furthermore, the molding resin may have a lens shape, and therefore, may function as a primary lens. The wavelength conversion layer 25 performs wavelength conversion on light emitted from the LED chip 23 to implement mixed color light, for example, white light. The LED 20 is designed to have a light orientation distribution having a mirror symmetric structure, and more particularly, may be designed to have a light orientation distribution having a rotational symmetric structure. In this case, an axis of the LED directed to the center of the light orientation distribution is defined as an optical axis L. That is, the LED 20 is designed to have a light orientation distribution which is left-right symmetric with respect to the optical axis L. In this case, the optical axis L may be defined as a straight line passing through the center of the cavity 21a. Although the LED 20 including the LED chip 23 and the housing 21 has been described as being mounted on the printed circuit board 10, the LED may have a structure in which the LED chip 23 is directly mounted on the printed circuit board 10, and the wavelength conversion layer 25 covers the LED chip 23 on the printed circuit board 10. The optical axis L may be coincident with the central axis C of the light diffusing lens 30 (see FIGS. 8 and 9).

Referring to FIG. 9, the light diffusing lens 30 may include a bottom surface 31 and a top surface 35, and may include a leg portion 39. The bottom surface 31 includes a concave light incident portion 31a, and the top surface 35 includes a concave surface 35a and a convex surface 35b. The inner surface of the light incident portion 31a may include a lateral surface 33a and a flat upper surface 33b. The upper surface 33b is perpendicular to the central axis C, and the lateral surface 33a extends from the upper surface 33b to the incident of the concave portion 31a. In this case, when the central axis C is aligned to be coincident with the optical axis L of the LED 20, the central axis C is defined as an axis being the center of the light orientation distribution emitted from the lens 30. Instead of omitting the flat upper surface 33b, the inner surface of the light incident portion 31b may be formed such that the lateral surface 33a meets the central axis C.

Referring to FIG. 10a, the bottom surface 31 of the light diffusing lens 30 substantially forms a square plane. Four corners of the square have rounded portions R. The bottom of the concave light incident portion 31a is located at the center of the bottom surface 31. The bottom surface of the light incident portion 31a has a circular shape. The circular shape of the light incident portion 31a is maintained over the entire height thereof, and the diameter thereof gradually decreases from the bottom toward the top (see FIG. 9).

Referring to FIGS. 10a, 10b and 10c in sequence, it can be seen that the bottom surface 31 of the diffusing lens 30 has a substantially square outer shape due to the substantially square bottom surface 31, but the outer shape of the diffusing lens become circular toward the top side. In order words, assuming that the shortest distance from the central axis to light emission surface of the diffusing lens 30 in the x-axis and y-axis directions is R1 and the shortest distance from the central axis to light emission surface of the diffusing lens 30 in the 45-degree diagonal-axis direction is R2, a difference between R2 and R1 decreases toward the top surface on the bottom surface of the light diffusing lens 30.

In particular, as illustrated in FIG. 10c, the light diffusing lens 30 includes a substantial circular top surface 35. A square concave surface 35a is formed in the central region of the top surface 35. The small square of the concave surface 35a is rotated by 45 degrees, with the same center as the large square of the bottom surface 31 of the light diffusing lens 30 (see FIG. 8). The above-described structure in which the shape of the concave surface 35a is rotated by 45 degrees with respect to the shape of the bottom surface 31 contributes to the improvement of the luminous efficiency. The light diffusing lens in which the concave surface 35a is omitted and the upper end portion of the light diffusing lens 30 is substantially flat may be also utilized. In addition, the light diffusing lens 30 may have a structure in which the top surface is circular and the central region of the circular top surface is flat or convex. Referring again to FIG. 9, the light incident portion 31a is a portion in which light emitted form the LED 20 is incident on the inside of the light diffusing lens 30. The LED 20 is located under the light incident portion 31a or located at a position corresponding to the light incident portion 31a. As described above, the incident region of the light incident portion 31a is circular. Therefore, the substantial square-shaped light pattern formed on the predetermined target surface by the diffusing lens 30 depends on the square-shaped bottom surface of the light diffusing lens 30, or the shape of the plane (that is, the light exist surface) expending from the corners of the bottom surface to the top surface of the diffusing lens 30.

FIG. 12 is a bottom view of a light diffusing lens according to a second embodiment of the present invention. Referring to the FIG. 12, the incident region of the light incident portion 31a may have a substantial square symmetric in the x-axis and y-axis directions. The four corners of the square may be rounded. In the case of using the square-shaped light incident portion 31a, the outer shape of the bottom surface 31 of the diffusing lens 30 may be circular as a whole. This is because the substantial square-shaped light pattern may be generated due to the square-shaped light incident portion 31a.

FIG. 13 conceptually illustrates the light patterns that can be formed on the predetermined target surface by the light emitting units according to the present invention. Each of the light emitting unit 1 includes an LED and a light diffusing lens. The light emitting unit 1 forms the light pattern having a substantial rectangular or ova shape or a similar shape thereto, which is axis-symmetric and 180-degree rotational symmetric with respect to the central axis of the light diffusing lens, on the predetermined target surface. The light pattern has the x-axis (minor-axis) and y-axis (major-axis) which are perpendicular to the central axis of the light diffusing lens on the same plane. In addition, the light pattern has a diagonal axis (or θ-axis) in a direction defined as θ = tan^-1(y/x) between the x-axis and the y-axis on the same plane. In this case, the illuminance in the x-axis, the illuminance in the y-axis, and the illuminance in the diagonal-axis are different from one other.

Although FIG. 13 illustrates that the light emitting unit 1 and its light pattern Lp are the perfect rectangular shape, an actual light pattern may have various shapes, for example, an elongated shape in the y-axis direction, such as a rounded rectangle or an oval shape.

The light pattern Lp is divided into nine regions according illuminance, to which reference symbols Ao1, Ax2, Ay2 and Az3 are assigned. Ao1 indicates the rectangular central region, which has the highest illuminance or light intensity, Ay2 indicates a pair of first lateral regions, which are symmetric to each other in the y-axis direction with respect to the central region Ao1, and Ax2 indicates a pair of second lateral regions, which are symmetric to each other in the x-axis direction with respect to the central region Ao1. Each of the first lateral regions Ay2 is a region where light is most concentrated next to the central region Ao1, and each of the second lateral regions Ax2 is a region where light is most concentrated next to the first lateral regions Ay2. Az3 indicates four corner regions, which are symmetric to each other in the 45-degree diagonal-axis direction with respect to the central region Ao1. The corner regions Az3 are regions where light is mot concentrated.

FIG. 14 is a diagram for describing a light emitting unit array including the light emitting units shown in FIG. 13 and the overall light patterns formed by the light emitting unit array.

FIG. 14 illustrates a light emitting unit array in which the light emitting units 1 are arranged in two rows and two columns. A light emitting unit array including more light emitting units arranged in N rows and n columns (where N and n are integers equal to or greater than 2) falls within the scope of the present invention. For the sake of convenience, the light emitting unit array including light emitting units arranged in two rows and two columns will be described as an example.

Each of the light emitting units 1 includes an LED and a light diffusing lens (see FIGS. 8, 9, 15 and 16). In this case, four light patterns Lp are formed by the four light emitting units 1 on a predetermined target surface spaced apart a certain distance from the light emitting unit in a vertical direction.

The central region Ao1 of the light pattern by the single light emitting unit 1 has illuminance dependent on the light from the corresponding light emitting unit 1 by at least 90%, ideally 100%, without overlapping the light pattern of another light emitting unit.

In addition, the light patterns of two adjacent light emitting units are overlapped in the two first lateral regions Ay2. Due to the overlapping of the light patterns, the illuminance in the two first lateral regions Ay2 may be almost similar to the illuminance in the central region Ao1. In addition, the light patterns of the two adjacent light emitting units are overlapped in the two second lateral regions Ax2. Due to the overlapping of the light patterns, the illuminance in the two second lateral regions Ax2 may be almost similar to the illuminance in the central region Ao1.

In addition, the light patterns of the four light emitting units are overlapped in the four corner regions Az3. Due to the overlapping of the light patterns, the illuminance in each of the four corner regions Az3 may be similar to the illuminance in the central region Ao1.

The individual light patterns elongated in a single axis direction by the above-descried light emitting units 1 form one large integrated light pattern on the predetermined target surface without gaps therebetween. In the integrated light pattern, the plurality of first and second lateral regions having relatively small illuminance and light intensity as compared with the central region are overlapped with the same regions of other light patterns adjacent to the plurality of corner regions. Therefore, the overall light pattern on the predetermined target surface may have a more uniform illuminance distribution.

Since the substantially rectangular or oval light patterns Lp, which are 180-degree rotational symmetric with respect to the central axis of the lens, are arranged on the target surface, it is possible to prevent or minimize the formation of darker portions or brighter portions in such a manner that the lateral regions or corner regions of the optical patterns are overlapped with the lateral regions or corner regions of the adjacent optical patterns. Therefore, it is possible to easily implement a surface light source or a direct type backlight having a uniform illuminance on the predetermined target surface.

Referring to FIG. 15a, in the case of using the light emitting unit including the light diffusing lens that is axis-asymmetric and 180-degree rotational symmetric with respect to the central axis thereof, illuminance distributions in the x-axis, y-axis and θ-axis (θ= tan^-1(y/x)) on the same plane perpendicular to the central axis of the light diffusing lens are different to one another. The light patterns having such illuminance distribution form a substantial rectangular or oval shape which is 180-degree rotational symmetric with respect to the central axis.

FIG. 15b illustrates three light orientation angle distribution patterns having different peak light intensities. Among the three light orientation angle distribution patterns, the pattern having the high light intensity is the pattern of the major-axis (y-axis) direction. The pattern having the second highest light intensity is the pattern of the θ-axis direction. The pattern having the lowest light intensity is the pattern of the minor-axis (x-axis) direction. The three light orientation angle distribution patterns illustrated in FIG. 15b all have peak light intensities of about 70 degree to 80 degrees. As can be seen from FIG. 15b, in the case of using the light diffusing lens that is 180-degree rotational symmetric and axis-asymmetric, the light orientation angle distribution patterns all have different light orientation angle distributions in the x-axis, y-axis and θ-axis directions.

The light emitting unit array according to the present invention can obtain a uniform illuminance distribution having almost no bright lines and dark regions through a specific arrangement of the light emitting units each including the light diffusing lens which is 180-degree rotational symmetric and axis-asymmetric with respect to the central axis, and their light patterns which are 180-degree rotational symmetric (see FIG. 7). Such uniform illuminance distribution can be obtained when each of the light emitting units constituting the light emitting unit array has the illuminance distribution and orientation angle distribution as illustrated in FIGS. 15a and 15b.

The uniform illuminance distribution can be obtained in such a manner that the illuminance of the central region of each of the light patterns, the illuminance of the first and second lateral regions generated by the overlapping of two light patterns adjacent in the x-axis and y-axis directions, and the illuminance of the corner regions generated by the overlapping of the four light patterns are made to be substantially similar to one another.

Light emitting units according to various embodiments of the present invention, which can form light patterns 180-degree rotational symmetric with respect to the central axis on a target surface as describes above, will be described below.

FIG. 16 is a schematic perspective view for describing a light emitting unit according to a third embodiment of the present invention. FIG. 17a is a cross-sectional view of the light emitting unit of FIG. 16, taken along a major-axis (y) direction, and FIG. 17b is a cross-sectional view of the light emitting unit of FIG. 16, taken along a minor-axis (x) direction.

Referring to FIGS. 16 and 17, the light emitting unit includes an LED 20 and a light diffusing lens 130 on a printed circuit board 10. Although a part of the printed circuit board 10 is illustrated, a plurality of LEDs 20 are arranged on the single printed circuit board 10 in a matrix form.

The printed circuit board 10 includes conductive land patterns on a top surface thereof, in which terminals of the LED 20 are bonded to the conductive land patterns. In addition, the printed circuit board 10 may include a reflective film on the top surface thereof. The printed circuit board 10 may be an MCPCB made of a metal having excellent thermal conductivity, or may be made of an insulating substrate material, such as FR4. Although not illustrated, a heat sink may be arranged under the printed circuit board 10 so as to dissipate heat generated from the LED 20.

As illustrated in FIG. 11, the LED 20 may include a housing 21, an LED chip 23 mounted on the housing 21, and a wavelength conversion layer 25 covering the LED chip 23. The LED 20 may further include lead terminals (not illustrated) supported to the housing 21.

The housing 21 constituting a package body may be made of a plastic resin, such as PA or PPA, by injection molding. In this case, the housing 21 may be molded to support the lead terminals by injection molding, and may have a cavity 21a for mounting the LED chip 23. The cavity 21a defines the light emission portion of the LED 20.

The lead terminals are disposed spaced apart from one another within the housing 21, and extend to the outside of the housing 21 and are bonded to the land patterns on the printed circuit board 10.

The LED chip 23 is mounted on the bottom of the cavity 21a and is electrically connected to the lead terminals. The LED chip 23 may be a gallium nitride-based LED for emitting ultraviolet light or blue light.

On the other hand, the wavelength conversion layer 25 covers the LED chip 23. In one embodiment, the wavelength conversion layer 25 may be formed by filling the cavity 21a with a phosphor-containing molding resin after the mounting of the LED chip 23. In this case, the wavelength conversion layer 25 may fill the cavity 21a of the housing 21, and have a substantially flat or convex top surface. Furthermore, a molding resin having a lens shape may be further applied on the wavelength conversion layer 25.

In another embodiment, the LED chip 23, on which a conformal phosphor coating layer is formed, may be mounted on the housing 21. That is, the conformal phosphor coating layer may be applied on the LED chip 23, and the LED chip 23 with the phosphor coating layer may be mounted on the housing 21. The LED chip 23 with the conformal coating layer may be molded with a transparent resin. Furthermore, the molding resin may have a lens shape, and therefore, may function as a primary lens.

The wavelength conversion layer 25 performs wavelength conversion on light emitted from the LED chip 23 to implement mixed color light, for example, white light.

The LED 20 is designed to have a light orientation distribution having a mirror symmetric structure, and more particularly, may be designed to have a light orientation distribution having a rotational symmetric structure. In this case, an axis of the LED 20 directed to the center of the light orientation distribution is defined as an optical axis L. That is, the LED 20 is designed to have a light orientation distribution which is left-right symmetric with respect to the optical axis L. In this case, the optical axis L may be defined as a straight line passing through the center of the cavity 21a. The optical axis L may be coincident with the central axis C of the light diffusing lens 30.

Although the LED 20 including the LED chip 23 and the housing 21 has been described as being mounted on the printed circuit board 10, the LED chip 23 may be directly mounted on the printed circuit board 10, and the wavelength conversion layer 25 may cover the LED chip 23 on the printed circuit board 10.

Referring again to FIGS. 17a and 17b, the light diffusing lens 130 may include a bottom surface 131 and a top surface 135, and may include a flange 137 and a leg portion 139. The bottom surface 131 includes a concave light incident portion 131a, and the top surface 135 includes a concave surface 135a and a convex surface 135b.

The bottom surface 131 forms a substantially disk-shaped plane, and the light incident portion 131a is located in the central portion of the bottom surface. The bottom surface 131 is not necessarily a plane, and may various uneven patterns may be formed thereon.

The light incident portion 131a is a portion of the lens 130 on which light emitted from the LED 20 is incident. The LED 20 and the LED chip 23 included therein are located under the central portion of the light incident portion 131a. The incident region of the light incident portion 131a may have an elongated shape. In FIGS. 17a and 17b, the incident region of the light incident portion 131a is elongated in the y-axis (major-axis) direction, in which the x-axis direction is a minor-axis direction and the y-axis direction is a major-axis direction.

The incident region of the light incident portion 131a may have various shapes, for example, (a) a rectangular shape, (b) an oval shape, or (c) a rounded rectangular shape as illustrated in FIG. 18. In the incident region of the light incident portion 131a, the width of the major-axis direction is indicated by "a", and the width of the minor-axis direction is indicated by "b".

Meanwhile, the width of the light incident portion 131a decreases from the incident region to the inside of the light incident portion 131a. As illustrated in FIG. 18, 19a and 19b, the cross-sectional shape of the light incident portion 131a may be a trapezoid shape having a left-right symmetric structure. In this case, FIG. 19a illustrates a cross section of the light incident portion 131a, taken along the major-axis (y-axis) direction, and FIG. 19B illustrates a cross section of the light incident portion 131a, taken along the minor-axis (x-axis) direction.

In FIG. 19a, the length of the lower side of the trapezoid is indicated by "a1" the length of the upper side of the trapezoid is indicated by "a2" and the angle with respect to the central axis of the line passing from the center of the lower side to the edge of the upper side is indicated by "a" In this case, a2 is less than the a1. On the other hand, in FIG. 19B, the length of the lower side of the trapezoid is indicated by "b1" the length of the upper side of the trapezoid is indicated by "b2" and the angle with respect to the central axis of the line passing from the center of the lower side to the edge of the upper side is indicated by "β". In this case, b2 is less than b1. Since a2 is greater than b2, it is preferable that is greater than β.

In FIGS. 19a and 19b, the cross-sectional shape of the light incident portion 131a is the trapezoid, the sides of which are straight lines. However, as illustrated in FIGS. 20a and 20b, the cross-sectional shape of the light incident portion 131a may have a trapezoid, the sides of which are curved.

As described above, the elongated optical patterns, which are 180-degree rotational symmetric, can be implemented by forming the incident region of the light incident portion 131a in the elongated shape.

Referring again to FIGS. 17a and 17b, the inner surface of the light incident portion 131a may have a lateral surface 133a and an upper surface 133b. The upper surface 33b is perpendicular to the central axis C, and the lateral surface 133a extends from the upper surface 133b to the incident of the light incident portion 131a. In this case, when the central axis C is aligned to be coincident with the optical axis L of the LED 20, the central axis C is defined as an axis being the center of the light orientation distribution emitted from the lens 130. Although FIGS. 17a and 17b illustrate that the light incident portion 131a has a flat upper surface, the light incident portion 131a may have an apex point at the upper end.

As described above, the light incident portion 131a may be narrower upward from the incident. That is, the lateral surface 133a is closer to the central axis C from the incident to the upper surface 133b. Therefore, the region of the upper surface 133b may be formed to be relatively smaller than the incident. The slope of the lateral surface 133a may be relatively gentle around the upper surface 133b.

The region of the upper surface 133b is limited within a region narrower than the incident region of the light incident portion 131a. In particular, the width in the minor-axis (x-axis) direction of the upper surface 133b may be limited within a region narrower than the region surrounded by a variable line formed by the concave surface 135 and the convex surface 135b of the upper surface 135. Furthermore, the width in the minor-axis (x-axis) direction of the upper surface 133b may be limited within a region narrower than the region of the cavity 21a of the LED 20, that is, the light emission portion.

When the optical axis L of the LED 20 and the central axis C of the lens 130 are misaligned, the region of the upper surface 133b alleviates the change in the orientation distribution of the light emitted through the top surface 135 of the lens 130. Therefore, the region of the upper surface 133b can be minimized in consideration of the alignment error between the LED 20 and the lens 130.

On the other hand, the top surface 135 of the lens 130 includes a concave surface 135a and a convex surface 135b extending from the concave surface 135a, with reference to the central axis C. A line defined when the concave surface 135a and the convex surface 135b are met becomes a variable line. The concave surface 135a refracts the light emitted around the central axis C of the lens 130 at a relatively large angle to disperse the light around the central axis C. In addition, the convex surface 135b increases the amount of light emitted outward from the central axis C.

The lens 130 has been described as being limited to the structure in which the concave surface 135a is formed on the top surface 135, but the present invention is not limited thereto. The central region of the top surface 135 may be flat or convex.

The top surface 135 and the light incident portion 131a may have a mirror-symmetric structure with respect to the plane passing through the central axis C along the x-axis or y-axis. In addition, the top surface 135 or the light emission surface may have a rotator shape that is axis-symmetric with respect to the central axis C. Furthermore, the light incident portion 131a and the top surface 135 may have various shapes according to a required light orientation angle distribution.

On the other hand, the flange 137 connects the top surface 135 and the bottom surface 131 and limits the outer size of the lens. Uneven patterns may be formed on the side of the flange 137 and the bottom surface 131. Meanwhile, the leg portion 139 of the lens 130 is connected to the printed circuit board 10, so that the bottom surface 131 is supported spaced apart from the printed circuit board 10. The connection is achieved in such a manner that the front ends of the leg portions 139 are attached to the printed circuit board 10 by, for example, an adhesive, or the leg portions 139 are respectively fitted into holes formed in the printed circuit board 10.

The lens 130 is located spaced apart from the LED 20. Therefore, the light incident portion 131a forms the boundary with external air. The housing 21 of the LED 20 may be located under the bottom surface 131. Furthermore, the wavelength conversion layer 25 of the LED 20 may be spaced apart from the light incident portion 131a and located under the bottom surface 313. Therefore, it is possible to prevent the light traveling within the light incident portion 131a from being lost due to absorption by the housing 21 or the wavelength conversion layer 25.

According to this embodiment, since the incident region of the light incident portion 131a has an elongated shape that is 180-degree rotational symmetric with respect to the central axis C, the orientation pattern of the light emitted through the lens 130 may have an elongated shape that is 180-degree rotational symmetric in the minor-axis (x-axis) direction.

Although the light incident portion 131a has been described as having the trapezoidal shape, the shape of the light incident portion 131a is not limited thereto and may have various shapes. FIGS. 21a to 21Dd are cross-sectional views for describing various modifications of the light incident portion.

FIG. 21a illustrates a case where a portion around the central axis C of the upper surface 133b perpendicular to the central axis C described with reference FIGS. 14a and 14b forms a downwardly convex shape. Due to the convex surface, light incident around the central axis C can be primarily controlled to disperse the light.

FIG. 21b is similar to but different from FIG. 21Aa in that the surface perpendicular to the central axis C in the upper surface of FIG. 21a is formed to be upwardly convex. Since the upwardly convex surface and the downwardly convex surface are mixed in the upper surface, it is possible to alleviate the change in the light orientation distribution due to alignment error of the LED and the lens.

FIG. 21c illustrates a case where a portion around the central axis C of the upper surface 133b perpendicular to the central axis C described with reference FIGS. 21Aa and 21b forms an upwardly convex shape. Due to the convex surface, light incident around the central axis C can be further dispersed.

FIG. 21d is similar to but different from FIG. 21c in that the surface perpendicular to the central axis C in the upper surface of FIG. 21c is formed to be downwardly convex. Since the upwardly convex surface and the downwardly convex surface are mixed in the upper surface, it is possible to alleviate the change in the light orientation distribution due to alignment error of the LED and the lens.

The above description has been focused on the light diffusing lens capable of forming the elongated light patterns on the predetermined target surface because the light incident portion has the elongated shape that is 180-degree rotational symmetric. The following description will be given of embodiments of the light diffusing lens capable of forming the elongated light patterns because the outer shape of the light exist surface with respect to the central axis, in particular, the shape of the bottom surface is 180-degree rotational symmetric.

FIG. 22 is an exploded perspective view for describing a light emitting unit according to a fourth embodiment of the present invention, and FIGS. 23A and 23B are cross-sectional views of the light emitting unit, taken along perpendicular directions of the light diffusing lens. Referring to FIGS. 22 to 23, the outer shape of the light emission surface 235 of the light diffusing lens 230 has an elongated shape in a direction perpendicular to the major-axis direction of the light incident portion 231a, that is, a minor-axis direction of the light incident portion 231a. In particular, the top surface of the light diffusing lens 230 may have a shape defined by overlapping of two semispheres. The symmetric surface of the two semispheres may be coincident with a surface passing through the center of the light incident portion 231a along the major-axis direction of the light incident portion 231a.

Since the outer shape of the light emission surface of the light diffusing lens 230 has the elongated shape in the minor-axis direction of the light incident portion 231a, the light can be dispersed by the shape of the light incident portion 231a and the outer shape of the light emission surface 235. Therefore, the light pattern can be formed to have a further elongated shape on a predetermined target surface. In a case where the outer shape of the light emission surface 235 has a shape that is 180-degree rotational symmetric with respect to the central axis C or a shape that is elongated in the major-axis direction, the light pattern elongated in a single axis direction can be formed on the target surface, even when the outer shape of the light emission surface 235 is axis-symmetric with respect to the central axis C of the light incident portion 231a.

On the other hand, the light emitting unit includes an LED 20 disposed under the light incident portion 231a of the light diffusing lens 230, and the LED 20 includes a cavity 21a that is 180-degree rotational symmetric. A light emitting surface is formed by filling the cavity 21a with an encapsulating material. The encapsulating material may contain a wavelength conversion material.

In this embodiment, the cavity and the light emitting surface of the LED 20 have a major-axis parallel to the major-axis of the light incident portion 231a and a minor-axis parallel to the minor-axis of the light incident portion 231a. In addition, the major-axis axes of the cavity and the light emitting surface of the LED 20 are parallel to the minor-axis of the outer shape of the light emission surface of the light diffusing lens 30 and perpendicularly intersect in the major-axis direction of the outer shape of the light emission surface. The LED 20 includes a pair of LED chips 25 arranged symmetrically in its own major-axis direction with respect to the central axis of the lens. The outer shape of the light emission surface of the light diffusing lens 230 is formed to have an elongated shape in the minor-axis direction of the light incident portion 231a, and the LED 20 is arranged to be elongated and symmetric in the major-axis direction of the light incident portion 231a. Therefore, the luminous efficiency can be enhanced, and the elongated light pattern that is 180-degree rotational symmetric can be more effectively formed on the target surface.

FIG. 24 is a cross-sectional view of a light emitting unit according to a fifth embodiment of the present invention, and FIGS. 25a, 25b and 25c are cross-sectional views taken along lines a-a, b-b and c-c of FIG. 24. The line a-a is a line on a bottom surface of the light diffusing lens, the line c-c is a line on the top surface of the light diffusing lens, and the line b-b is a cut line in a middle height of the light diffusing lens between the line a-a and the line c-c. FIG. 26 is a detailed diagram for describing the light diffusing lens of the light emitting unit illustrated in FIG. 24. FIG. 27 is a diagram illustrating a light orientation angle distribution when using the light diffusing lens illustrated in FIG. 26.

Referring to FIG. 24, the light emitting unit includes an LED 20 disposed on a printed circuit board 10, and a light diffusing lens 30 made of a resin or glass material and disposed on the LED 20. Although the printed circuit board 10 is partially illustrated such that a single light emitting unit is shown, a plurality of light emitting units may be arranged regularly on the single printed circuit board 10.

The printed circuit board 10 includes conductive land patterns on the top surface thereof, in which terminals of the LED 20 are bonded to the conductive land patterns. In addition, the printed circuit board 10 may include a reflective film on the top surface thereof. The printed circuit board 10 may be an MCPCB made of a metal having excellent thermal conductivity, or may be made of an insulating substrate material, such as FR4. Although not illustrated, a heat sink may be arranged under the printed circuit board 10 so as to dissipate heat generated from the LED 20.

Since the LED 20 has been described above in detail with reference to FIG. 11, the detailed description thereof will be omitted.

Referring to FIG. 24, the light diffusing lens 330 includes a bottom surface 331 and a light emission surface 335 opposite to the bottom surface, and may include a leg portion 339. The bottom surface 331 includes a concave light incident portion 331a. The light emission surface 335 is curved to be upwardly convex as a whole, and includes a flat surface 335a on the upper center. The flat surface 335a is located at a position corresponding to the concave portion of the conventional light diffusing lens, while the light diffusing lens 330 of this embodiment can diffuse the light around the optical axis widely without any concave portion in the upper center by the structure of the light incident portion 331a which will described in detail below. The light incident portion 331a has a substantial bell-shaped cross-section, and is gradually convergent from the lower incident adjacent to the LED 20 toward the apex point of the upper end.

Referring to FIG. 25a, the bottom surface 331 of the light diffusing lens 330 is circular. In addition, the lower portion of the light incident portion 331a is located at the center of the bottom surface 331, and the lower portion of the light incident portion 331a is circular. The shape of the light incident portion 331a maintains the circular shape from the lower incident to the upper apex point, and the diameter thereof gradually decreases from the lower portion toward the upper portion. Referring to FIG. 25c, the upper flat surface 335a of the light diffusing lens 330 is also circular.

Referring to FIGS. 25a, 25b and 25c in sequence, the light diffusing lens 330 has a circular bottom surface 331 that gradually becomes smaller toward the upper portion. The change in the diameter of the outer circular shape in the lateral lower portion of the lens 330 may be larger than the change in the diameter of the outer circular shape in the lateral upper portion of the lens 330. The diameter of the circular light incident portion 331a gradually decreases.

FIG. 26 illustrates the optical axis L that is the central axis of the light diffusing lens 330. In order to obtain uniform light distribution by using the light diffusing lens 330, a peak light intensity has to exist at an angle of not less than 60 degrees from the optical axis L. In order to obtain the above-described optical characteristic, it is important to effectively disperse light within a range of 50 degrees from the optical axis L. In FIG. 4, a reference line r forms 50 degrees with respect to the optical axis L.

In order to effectively disperse light within the range of 50 degrees from the optical axis L, in the angel range between the optical axis L and the reference line r, that is, within a range of 50 degrees, the shortest distance "b" from an arbitrary point p on the optical axis L to the apex point of the light incident portion 331a is greater than the shortest distance "a" from the point p to the side of the light incident portion 331a. In the case of b > a, as describe above, the light incident portion 331a may contribute to widely diffusing light traveling within the range of 50 degrees from the light axis L to be passed at more than 60 degrees from the optical axis L. On the other hand, in the case of b < a, with respect to light passing in the range of 50 degrees from the optical axis L, the light incident portion 31a hardly contributes to diffusion of light. Therefore, a separate concave portion is required to widely diffuse light in the upper center of the light emission surface according to the prior art. In order words, the light diffusing lens 330 according to the present invention can omit the concave portion in the upper center of the light emission portion required in the prior art due to the curvature structure of the light incident portion 331a satisfying the condition of b > a within the range of 50 degrees from the optical axis L.

In this case, the height of the light incident portion 331a is preferably greater than the diameter R of the lower incident of the light incident portion 331a. Furthermore, the height H is most preferably greater than 1.5 times the diameter R. In addition, the lower portion of the light incident portion 331a forms the boundary with air, the reflective index of which is lower than that of a resin or glass material, and the upper portion of the light emission surface also forms the boundary with air, the reflective index of which is lower than that of a resin or glass material.

FIG. 27 illustrates a light orientation angle distribution available using the light diffusing lens of FIG. 26. Referring to FIG. 27, it can be seen that a peak light intensity occurs at a location spaced apart from the optical axis L by 72 degrees, which means that light is widely diffused and distributed. From the results of FIG. 27, it can be seen that the light diffusing lens 330 according to the present invention effectively diffuses light within 60 degrees from the optical axis L without the concave portion in the upper center of the light emission surface due to the curvature structure of the light incident portion 31a satisfying the condition of b > a within the range of 50 degrees from the optical axis L. Therefore, the light can be uniformly diffused and distributed.

FIG. 28 is a diagram for describing a light diffusing lens according to a sixth embodiment of the present invention. As is well illustrated in FIG. 28, in the light diffusing lens 430 according to this embodiment, the curvature structure of the light incident portion 431a is identical to that of the light diffusing lens according to the previous embodiment illustrated in FIG. 26. Therefore, the light incident portion 431a satisfies the condition of b > a within the range of 50 degrees from the optical axis L. In the previous embodiment, the light diffusing lens includes a flat surface in the upper center of the light emission surface. However, in this embodiment, the light diffusing lens 430 includes a convex curved surface 435b in the upper center of the light emission surface.

FIG. 29 is a diagram illustrating a light orientation angle distribution available using the light diffusing lens of FIG. 28. Referring to FIG. 29, it can be seen that a peak light intensity occurs at a location spaced apart from the optical axis L by 72 degrees, which means that light is widely diffused and distributed. In addition, when the light orientation angle distribution illustrated in FIG. 29 is compared with the light orientation angle distribution illustrated in FIG. 27, a great difference is hardly found. It can be seen that, if the light incident portion 431a satisfies the condition of b > a within the range of 50 degrees from the optical axis L, there is no great difference between the light orientation angle distributions when the upper center of the light emission surface is formed to have a flat surface and when the upper center of the light emission surface is formed to have a convex surface.

FIGS. 30a and 30b illustrate a light diffusing lens and its orientation angle distribution curve according to a first comparative example.

In the light diffusing lens illustrated in FIG. 30a, within the range of 50 degrees from the optical axis, the shortest distance "b" from an arbitrary point on the optical axis to the apex point of the light incident portion is greater than the shortest distance "a" from the same point to the side of the light incident portion, and, at the same time, the light diffusing lens includes a concave portion in the upper center of the light emission surface. The light orientation angle distribution in the above-described condition can be seen from FIG. 8b. It can be seen that the light orientation angle distribution is not almost different from the light orientation angle distribution of the previous embodiment. Under the condition of b > a, the concave portion located in the upper center of the light emission surface hardly contributes to changing the light orientation angle distribution.

FIGS. 31a and 31b illustrate a light diffusing lens and its orientation angle distribution curve according to a second comparative example.

In the light diffusing lens illustrated in FIG. 31a, within the range of 50 degrees from the optical axis, the shortest distance "b" from an arbitrary point on the optical axis to the apex point of the light incident portion is less than the shortest distance "a" from the same point to the side of the light incident portion, and, at the same time, the light diffusing lens includes a concave portion in the upper center of the light emission surface. The light orientation angle distribution in the above-described condition can be seen from FIG. 31b. It can be seen that the light orientation angle distribution is not almost different from the light orientation angle distributions of the first comparative example and the above-described embodiments. This represents that, under the condition of b > a, the concave portion existing in the upper center of the light emission surface functions to widely diffuse light within 50 degrees from the optical axis.

Claims

A light emitting unit array, comprising:

a plurality of light emitting units arranged under a target surface in a matrix form,

wherein each of the light emitting units comprises a light diffusing lens with a central axis and an LED disposed under the light diffusing lens,

wherein each of the light emitting units form light patterns having different illuminance distributions in at least one direction from the central axis,

wherein each of the light patterns comprises a central region and peripheral regions having an illuminance lower than the central region,

wherein the central region depends on a single light pattern, and

a plurality of light patterns overlap one another in each of the peripheral regions.
The light emitting unit array of claim 1, wherein the light pattern has different illuminance distributions of two axis directions on the same plane, and the light pattern comprises first to third regions,

wherein the first region has a single light pattern,

wherein the second region comprises two adjacent light patterns overlapped with each other, and

wherein the third region comprises four adjacent light patterns overlapped with one another.
The light emitting unit array of claim 2, wherein the first region comprises a central region of each of the light patterns,

wherein the second region comprises lateral regions, which are symmetric to each other in an x-axis direction or a y-axis direction with respect to the central region, and

wherein the third region comprises corner regions, which are symmetric in a 45-degree diagonal-axis with respect to the central region.
The light emitting unit array of claim 2, wherein an illuminance by a single light pattern in the first region, an illuminance by the overlapping of the two light patterns in the second region, an illuminance by the overlapping of the four light patterns in the third region are identical or similar to one another.
The light emitting unit array of claim 1, wherein the light diffusing lens comprises a concave light incident portion in a lower portion and a light emission surface in an upper portion, and an outer shape of the light emission surface is 90-degree rotational symmetric with respect to the central axis of the light diffusing lens.
The light emitting unit array of claim 1, wherein a difference between shortest distances from the central axis of the light diffusing lens to a light emission surface of the light diffusing lens decreases from a lower portion toward an upper portion of the light diffusing lens.
The light emitting unit array of claim 6, wherein the light diffusing lens comprises a concave surface in a center of a top surface, and a shape of the concave surface is rotated by 45 degrees with respect to a shape of a bottom surface.
The light emitting unit array of claim 1, wherein the light diffusing lens comprises a concave light incident portion in a lower portion and a light emission surface in an upper portion, and the light incident portion has a shape that is 90-degree rotational symmetric with respect to the central axis of the light diffusing lens.
The light emitting unit array of claim 1, wherein, in each of the light patterns, an illuminance distribution in an x-axis direction is identical to an illumination distribution in a y-axis direction, and an illuminance distribution in a 45-degree diagonal-axis direction between x-axis and y-axis is different from the illuminance distributions in the x-axis and y-axis directions.
The light emitting unit array of claim 1, wherein the light pattern has a rectangular shape in one axis direction perpendicular to the central axis.
The light emitting unit array of claim 1, wherein the peripheral regions include a pair of first lateral regions that are symmetric to each other in a major-axis direction, a pair of second lateral regions that are symmetric to each other in a minor-axis direction, and four corner regions that are symmetric to one another in a θ-axis (θ = tan^-1(y/x)) direction,

each of the first and second lateral regions comprises two adjacent light patterns overlapped with each other, and

each of the corner regions comprises four adjacent light patterns overlapped with one another.
The light emitting unit array of claim 1, wherein an illuminance by the overlapping of the light patterns in each of the peripheral regions is 70 to 130% of an illuminance by the single light pattern of the central region.
The light emitting unit array of claim 1, wherein the light diffusing lens comprises a concave light incident portion in a lower portion and a light emission surface in an upper portion, and an outer shape of the light emission surface or the light incident portion has a major-axis perpendicular to the central axis and is 180-degree rotational symmetric with respect to the central axis.
The light emitting unit array of claim 1, wherein the light diffusing lens comprises a concave light incident portion in a lower portion and a light emission surface in an upper portion,

an outer shape of the light emission surface and the light incident portion have a major-axis perpendicular to the central axis and are 180-degree rotational symmetric, and

the major axis of the outer shape and the major axis of the light incident portion intersect with each other at a right angle.
The light emitting unit array of claim 10, wherein the LED comprises a major-axis parallel to the major-axis of the light incident portion, and comprises a rectangular light emitting surface formed along the major axis.
The light emitting unit array of claim 7, wherein the LED comprises a pair of LED chips that are symmetric to each other with respect to the central axis and disposed along a major-axis of the LED.
The light emitting unit array of claim 16, wherein the LED comprises a pair of LED chips that are symmetric to each other with respect to the central axis and disposed along the major-axis of the LED.
The light emitting unit array of claim 13 or 14, wherein an incident region of the light incident portion has a rectangular shape, an oval shape, or a rounded rectangular shape.
The light emitting unit array of claim 13 or 14, wherein a cross-section of the concave portion of the light incident portion according to a one-axis direction has a trapezoidal shape that is symmetric with respect to the central axis and sides of which have a straight-line or curved structure.
The light emitting unit array of claim 19, wherein a cross-section of the concave portion of the light incident portion according to a direction perpendicular to the one-axis direction has a trapezoidal shape that is symmetric with respect to the central axis and sides of which have a straight-line or curved structure.
The light emitting unit array of claim 13 or 14, wherein an outer shape of the light emission surface has a structure that is axis-symmetric with respect to the central axis.
The light emitting unit array of claim 13 or 14, wherein the light emission surface has a shape defined by overlapping two semispheres.
The light emitting unit array of claim 1, wherein the light diffusing lens comprises a concave light incident portion in a lower portion and a light emission surface in an upper portion,

an upper center of the light emission surface is formed to have a flat surface or a convex curved surface and has an optical axis in a central portion thereof, and

the light incident portion has a structure in which a shortest distance from one point on the optical axis to an apex point of the light incident portion is greater than a shortest distance from the same point to sides of the light incident portion within a range of 50 degrees from the optical axis.
The light emitting unit array of claim 23, wherein the light incident portion has a bell shape.
The light emitting unit array of claim 23, wherein the light incident portion has a circular lower incident adjacent to the LED, and is shaped to be gradually convergent toward the apex point while maintaining a circular shape.
The light emitting unit array of claim 23, wherein a height of the light incident portion is greater than a diameter of the lower incident by 1.5 times or more.
The light emitting unit array of claim 1, wherein the light diffusing lens comprises a concave light incident portion in a lower portion and a light emission surface in an upper portion, and a central region of the light emission surface and an upper surface of the light incident portion are substantially a flat plane.
The light emitting unit array of claim 27, wherein the central region of the light emission surface has a structure of a flat surface or a convex surface.
The light emitting unit array of claim 27, wherein the upper surface of the light incident portion has a structure of a flat surface or a convex surface.
A light diffusing lens suitable for each light emitting unit of a light emitting unit array, wherein the light diffusing lens receives light from an LED and forms light patterns having different illuminance distributions in at least one direction with respect to a central axis,

each of the light patterns comprises a central region and peripheral regions each having an illuminance lower than that of the central region,

the central region depends on a single light pattern, and

a plurality of light patterns overlaps one another in each of the peripheral regions.
The light diffusing lens of claim 30, wherein the peripheral regions of the light pattern comprises lateral regions and corner regions, the central region has highest illuminance, and each of the corner regions has lowest illuminance.
The light diffusing lens of claim 30, wherein the light pattern has a square shape or a similar shape thereto.
The light diffusing lens of claim 30, wherein the light diffusing lens comprises a concave light incident portion in a lower portion and a light emission surface in an upper portion.
The light diffusing lens of claim 30, wherein the outer shape of the light emission surface is 90-degree rotational symmetric with respect to the central axis of the light diffusing lens.
The light diffusing lens of claim 31, wherein the light diffusing lens has an outer shape of the light emission surface having different shortest distances in a bottom surface, and the shortest distances are shortest distances from the central axis of the light diffusing lens to the light emission surface of the light diffusing lens.
The light diffusing lens of claim 35, wherein a difference between the shortest distances decreases from the lower portion toward the upper portion of the light diffusing lens.
The light diffusing lens of claim 33, wherein the light diffusing lens comprises a concave surface in a center of a top surface, and a shape of the concave surface is rotated by 45 degrees with respect to a shape of a bottom surface.
The light diffusing lens of claim 30, wherein the light incident portion is 90-degree rotational symmetric with respect to the central axis of the light diffusing lens.
The light diffusing lens of claim 38, wherein an outer shape of the light emission surface has a structure that is axis-symmetric with respect to the central axis.
The light diffusing lens of claim 30, wherein, in each of the light patterns, an illuminance distribution in an x-axis direction is identical to an illuminance distribution in a y-axis direction on the same plane, and an illuminance distribution in a 45-degree diagonal-axis direction between x-axis and y-axis is different from the illuminance distributions in the x-axis and y-axis directions.
The light diffusing lens of claim 30, wherein the light diffusing lens comprises a light incident portion and a light emission surface, and at lease one of the light incident portion and the light emission surface has a shape that is 180-degree rotational symmetric with respect to the central axis.
The light diffusing lens of claim 41, wherein the outer shape of the light emission surface has a major-axis perpendicular to the central axis, and is 180-degree rotational symmetric with respect to the central axis.
The light diffusing lens of claim 41, wherein the light incident portion has a major-axis perpendicular to the central axis, and is 180-degree rotational symmetric with respect to the central axis.
The light diffusing lens of claim 41, wherein the light incident portion and an outer shape of the light emission surface have a major-axis perpendicular to the central axis, and are 180-degree rotational symmetric, and

the major axis of the outer shape and the major axis of the light incident portion intersect with each other at a right angle.
The light diffusing lens of claim 41, wherein an incident region of the light incident portion has a rectangular shape, an oval shape, or a rounded rectangular shape.
The light diffusing lens of claim 41, wherein a cross-section of the concave portion of the light incident portion according to a one-axis direction has a trapezoidal shape that is symmetric with respect to the central axis and sides of which have a straight-line or curved shape.
The light diffusing lens of claim 46, wherein a cross-section of the concave portion according to a direction perpendicular to the one-axis direction has a trapezoidal shape that is symmetric with respect to the central axis and sides of which have a straight-line or curved structure.
The light diffusing lens of claim 43, wherein an outer shape of the light emission surface has a structure that is axis-symmetric with respect to the central axis.
The light diffusing lens of claim 41, wherein the light emission surface has a shape defined by overlapping two semispheres.
The light diffusing lens of claim 30, wherein the light diffusing lens comprises a concave light incident portion in a lower portion and a light emission surface in an upper portion,

an upper center of the light emission surface is formed to have a flat surface or a convex curved surface and has an optical axis in a central portion thereof, and

the light incident portion has a structure in which a shortest distance from one point on the optical axis to an apex point of the light incident portion is greater than a shortest distance from the same point to sides of the light incident portion within a range of 50 degrees from the optical axis.
The light diffusing lens of claim 50, wherein the light incident portion has a bell shape.
The light diffusing lens of claim 50, wherein the light incident portion has a circular lower incident, and is shaped to be gradually convergent toward the apex point while maintaining a circular shape.
The light diffusing lens of claim 52, wherein a height of the light incident portion is greater than a diameter of the lower incident by 1.5 times or more.
The light diffusing lens of claim 30, wherein the light diffusing lens comprises a concave light incident portion in a lower portion and a light emission surface in an upper portion, and a central region of the light emission surface and an upper surface of the light incident portion are substantially a flat surface.
The light diffusing lens of claim 54, wherein the central region of the light emission surface has a structure of a flat surface or a convex surface.
The light diffusing lens of claim 54, wherein the upper surface of the light incident portion has a structure of a flat surface or a convex surface.