Abstract:
Provided is a backlight unit ( 49 ) which includes a plurality of LEDs ( 11 ). The LEDs ( 11 ) are two-dimensionally disposed, thereby having the collection of light emitted from the LEDs ( 11 ) in a state of planar light. Furthermore, the backlight unit ( 49 ) has the planar light divided into a plurality of sections, and includes a luminance variable system (for instance, a system having disposition which a difference in the density of LEDs ( 11 )), which can change luminance, corresponding to each section.

Description:
TECHNICAL FIELD 
     The present invention relates to illuminating apparatus for incorporation in display apparatus such as liquid crystal display apparatus, and to display apparatus themselves. 
     BACKGROUND ART 
     A liquid crystal display apparatus (display apparatus) that incorporates a non-luminous liquid crystal display panel (display panel) commonly also incorporates a backlight unit (illuminating apparatus) that supplies light to the liquid crystal display panel. As light sources for use in backlight units, there are many kinds. For example, the backlight unit disclosed in Patent Document 1 listed below employs an LED (light-emitting diode) as a backlight. 
     In the backlight unit disclosed in Patent Document 1, as shown in  FIG. 31 , a plurality of LEDs (point light sources)  111  are in a matrix-like lattice arrangement at equal intervals, and the light emitted from them is mixed to produce planar light (in a plan view like  FIG. 31 , no planar light is illustrated; it should still be interpreted that planar light having a shape similar to the shape around the edge of the group of LEDs  111  in a lattice arrangement is produced). The produced planar light is supplied to the entire surface of a liquid crystal display panel. 
     LIST OF CITATIONS 
     Patent Literature 
     
         
         Patent Document 1: JP-A-2006-128125 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     Nowadays, liquid crystal display panels are becoming increasingly large. The growing size of liquid crystal display panels has to be coped with by increasing the planar size of planar light. Accordingly, the backlight unit disclosed in Patent Document 1 has to use an increased number of LEDs  111 , inconveniently resulting in higher cost of the backlight unit and hence the liquid crystal display apparatus. 
     To reduce cost, a backlight unit may be, as shown in  FIG. 32 , so deigned as to use less LEDs  111  in a peripheral part of the LEDs  111  in a lattice arrangement in  FIG. 31 . Inconveniently, however, such a backlight unit suffers from a large difference in luminance between a region including the planar center of the planar light and a peripheral region of the planar light, resulting in lowered uniformity in the luminance of the planar light and hence the image displayed on the liquid crystal display panel. 
     The present invention has been made to overcome the inconveniences discussed above, and aims to provide an illuminating apparatus etc. that are less costly, through the use of a smaller number of point light sources such as LEDs or through the use of inexpensive LEDs, but that nevertheless can form planar light with high uniformity. 
     Solution to Problem 
     In an illuminating apparatus including a plurality of point light sources, the plurality of point light sources are arranged two-dimensionally so that the light therefrom gathers to form planar light. Moreover, in this illuminating apparatus, the planar light is divided into a plurality of sections, and there is provided a luminance-varying system that can vary luminance section by section. 
     The luminance-varying system is, for example, an arrangement involving a difference in the density of the point light sources. With this design, the density of the plurality of point light sources that produce the planar light is varied appropriately, and thereby the luminance distribution of the planar light is varied (which makes it possible to enhance the uniformity of the planar light). In particular, without increasing the number of point light sources, simply by varying the density of point light sources, it is possible to obtain an illuminating apparatus that produces planar light with enhanced uniformity. 
     In the illuminating apparatus, preferably, when, of two intersecting directions, one is referred to as the X direction and another is referred to as the Y direction, the illuminating apparatus includes point light sources arranged side by side along the X and Y directions, and there are a plurality of kinds of intervals among the intervals between the point light sources arranged side by side along at least one of the X and Y directions. 
     More specifically, in one example, X-direction rows in which the point light sources are arranged at same positions with respect to the Y direction and side by side along the X direction are arranged side by side in the Y direction so that the plurality of point light sources are in a lattice-like planar arrangement, and there are a plurality of kinds of intervals among the intervals between the point light sources arranged side by side along at least one of the X and Y directions. 
     The positions of the point light sources with respect to the X direction between adjacent X-direction rows may be the same from one X-direction row to the next, or the positions of the point light sources with respect to the X direction between adjacent X-direction rows may differ from one X-direction row to the next. 
     When the rows which are formed as a result of the X-direction rows being arranged side by side in the Y direction and in which the point light sources are arranged at same positions with respect to the X direction and side by side along the Y direction are referred to as the Y-direction rows (for example, when the point light sources are arranged like a matrix), the illuminating apparatus may further include a point light source that is not along either the X-direction rows or the Y-direction rows. With this design, the luminance distribution of the planar light can be varied finely. 
     In another example, in a backlight unit, one row of the point light sources arranged side by side along the X direction and one row of the point light sources arranged side by side along the Y direction are arranged to form, for example, an L shape, and emit light in different directions so that the light overlaps to form the planar light. In this backlight unit, preferably, there are a plurality of kinds of intervals among the intervals between the point light sources arranged side by side along at least one of the X and Y directions. 
     Examples in which there are a plurality of kinds of intervals among the intervals between the point light sources include the following two. In a first example, the interval at which a plurality of the point light sources that produce the light near the planar center of the planar light are arranged is shorter than the interval at which a plurality of the point light sources that produce light at periphery elsewhere than near the planar center of the planar light are arranged. 
     In a second example, the interval at which a plurality of the point light sources that produce light near the planar center of the planar light are arranged is longer than the interval at which a plurality of the point light sources that produce light at periphery elsewhere than near the planar center of the planar light are arranged. 
     There are still other examples of planar arrangements of a plurality of point light sources. For example, the arrangement surface of the planar arrangement may include a plurality of divided regions divided like a lattice, the point light sources being allocated among those divided regions. Preferably, to produce a difference in the density of the point light sources, there are a plurality of kinds of numbers among the numbers of point light sources located within the divided regions respectively. 
     For example, when the divided regions in which the point light sources that produce light near the planar center of the planar light are located are referred to as the central divided regions, and the divided regions in which the point light sources that produce light at periphery elsewhere than near the planar center of the planar light are located are referred to as the peripheral divided regions, then the number of point light sources included in each of the central divided regions may be greater than the number of point light sources included in each of the peripheral divided regions, or the number of point light sources included in the peripheral divided regions may be greater than the number of point light sources included in the central divided regions. 
     The point light sources mentioned above are mounted on a mounting board, and there is no particular restriction on the number of such mounting boards. For example, a plurality of mounting boards may be arranged such that, whereas the intervals at which the point light sources are arranged within each of the mounting boards are equal, the intervals at which the point light sources are arranged differ among the mounting boards. 
     Also with such mounting boards, incorporating a plurality of them in the illuminating apparatus produces a difference in the density of the point light sources. In addition, these mounting boards each have the same arrangement of point light sources, and can thus be mass-produced extremely easily. This helps reduce the cost of the mounting boards and hence the cost of the illuminating apparatus. Moreover, the mounting boards have a comparatively small size, and are thus easy to handle in the manufacturing process of the illuminating apparatus. Incorporating such mounting boards, the illuminating apparatus can be manufactured easily at reduced cost. Moreover, the size of the illuminating apparatus no longer limits the application of the mounting boards. 
     Preferably, the plane of the planar light is divided into a plurality of areas by an imaginary line lying on the planar center of the planar light, and the arrangement of a plurality of the point light sources that produce light of the planar light in one of the divided areas and the arrangement of a plurality of the point light sources that produce light of the planar light in another of the divided areas are line-symmetric about the imaginary line. 
     With this design, in a case where the point light sources are controlled in various ways according to a given algorism, the same sequence of control is repeated, and this helps alleviate the burden of control. Moreover, it is easy to produce the program for the control of the light emission of the point light sources, which affects the luminance distribution of the planar light. 
     The illuminating apparatus includes a current controller that controls the current values supplied to the point light sources. Preferably, in a case where the point light sources are arranged some at a longer interval and other at a shorter interval, the current controller makes different the current value supplied to the point light sources arranged at a longer interval and the current value supplied to the point light sources arranged at a shorter interval. With this design, it is possible to vary the light emission luminance specific to the point light sources. 
     Preferably, the current supplied to the point light sources arranged at a longer interval is higher than current supplied to the point light sources arranged at a shorter interval. 
     With this design, even if a difference in the density of the point light sources (for example, as produced by a group of point light sources arranged at a longer interval) may leave a region with slightly less than sufficient luminance in the luminance distribution of the planar light, the luminance specific to the light from those point light sources that produce light in that region is high. This makes the planar light less likely to have a region with insufficient luminance, and helps reliably enhance the uniformity of the planar light. 
     The current values supplied to the point light sources need not be relied upon; instead, a difference in the light emission efficiency of the point light sources may be exploited to enhance the uniformity of the planar light. For example, in a case where the point light sources are arranged some at a longer interval and other at a shorter interval, preferably, the light emission efficiency of the point light sources differs between the point light sources arranged at a longer interval and the point light sources arranged at a shorter interval. 
     When the light emission efficiency of the point light sources arranged at a longer interval is higher than the light emission efficiency of the point light sources arranged at a shorter interval, even if a group of the point light sources arranged at a longer interval may produce a region with less then sufficient luminance in the luminance distribution of the planar light, the light in that region has increased luminance owing to the light of the point light sources with higher light emission efficiency, and this helps reliably increase the uniformity of the planar light. 
     The luminance-varying system mentioned above is not limited to an arrangement involving a difference in the density of point light sources. For example, even with an arrangement involving no difference in the density of point light sources, if the illuminating apparatus includes a current controller that varies the luminance distribution of the planar light by a difference in the current values supplied to the point light sources, the uniformity of the planar light is enhanced (i.e., the current controller can be said to be a luminance-varying system). 
     Also, even with an arrangement involving no difference in the density of point light sources, using point light sources with different light emission efficiency among the point light sources that produce the planar light produces a change in the luminance distribution of the planar light. Thus, producing planar light with a group of such point light sources with different light emission efficiency can also be said to be a luminance-varying system. 
     Display apparatus including an illuminating apparatus as described above and a display panel that receives light emanating from the illuminating apparatus can also be said to be within the scope of the invention. 
     Advantageous Effects of the Invention 
     With lighting apparatus according to the present invention, for example, by appropriately varying the density of a plurality of point light sources that produce planar light, the luminance distribution of the planar light is varied, and thereby the uniformity of the planar light can be enhanced. Moreover, enhancing the uniformity of the planar light can be achieved simply by varying the density of point light sources without increasing the number of point light sources, and this suppresses the cost of lighting apparatus. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       [ FIG. 1 ] is a plan view showing an arrangement of LEDs in Example 1; 
       [ FIG. 2 ] is a plan view showing an arrangement of LEDs in Example 2; 
       [ FIG. 3 ] is a plan view showing an arrangement of LEDs in Example 3; 
       [ FIG. 4 ] is a plan view showing an arrangement of LEDs in Example 4; 
       [ FIG. 5 ] is a plan view showing an arrangement of LEDs in Example 5; 
       [ FIG. 6 ] is a plan view showing an arrangement of LEDs in Example 6; 
       [ FIG. 7 ] is a plan view showing an arrangement of LEDs in Example 7; 
       [ FIG. 8 ] is a plan view showing an arrangement of LEDs in Example 8; 
       [ FIG. 9 ] is a plan view showing an arrangement of LEDs in Example 9; 
       [ FIG. 10 ] is a plan view showing an arrangement of LEDs in Example 10; 
       [ FIG. 11 ] is a plan view showing an arrangement of LEDs in Example 11; 
       [ FIG. 12 ] is a plan view showing an arrangement of LEDs in Example 12; 
       [ FIG. 13 ] is a plan view showing an arrangement of LEDs in Example 13; 
       [ FIG. 14 ] is a plan view showing an arrangement of LEDs in Example 14; 
       [ FIG. 15 ] is a plan view showing an arrangement of LEDs in Example 15; 
       [ FIG. 16 ] is a plan view showing an arrangement of LEDs in Example 16; 
       [ FIG. 17 ] is an exploded perspective view of a liquid crystal display apparatus; 
       [ FIG. 18 ] is a perspective view showing how planar light is produced; 
       [ FIG. 19 ] is a block diagram showing various members included in a liquid crystal display apparatus; 
       [ FIG. 20 ] is a perspective view showing how planar light is produced; 
       [ FIG. 21 ] is an exploded perspective view of a liquid crystal display apparatus; 
       [ FIG. 22 ] is a plan view showing an arrangement of LEDs in Example 17; 
       [ FIG. 23 ] is a plan view showing an arrangement of LEDs in Example 18; 
       [ FIG. 24 ] is a plan view showing an arrangement of LEDs in Example 19; 
       [ FIG. 25 ] is a plan view showing an arrangement of LEDs in Example 20; 
       [ FIG. 26 ] is a plan view showing an arrangement of LEDs in Example 21; 
       [ FIG. 27 ] is a plan view showing an arrangement of LEDs in Example 22; 
       [ FIG. 28 ] is a plan view showing an arrangement of LEDs in Example 23; 
       [ FIG. 29 ] is a plan view showing an arrangement of LEDs in Example 24; 
       [ FIG. 30 ] is a plan view showing an arrangement of LEDs in Example 25; 
       [ FIG. 31 ] is a plan view showing an arrangement of LEDs incorporated in a conventional backlight unit; and 
       [ FIG. 32 ] is a plan view showing an arrangement of LEDs incorporated in a conventional backlight unit. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     [Embodiment 1] 
     An embodiment of the present invention will be described below with reference to the accompanying drawings. For convenience&#39; sake, hatching and reference signs are occasionally omitted, in which case any other relevant drawings are to be referred to. Also for convenience&#39; sake, hatching is occasionally used elsewhere than in sectional views. A black dot appearing on arrows indicates the direction perpendicular to the plane of paper. 
       FIG. 17  is an exploded perspective view of a liquid crystal display apparatus. As shown there, the liquid crystal display apparatus  69  includes a liquid crystal display panel  59  and a backlight unit (illuminating apparatus)  49  which supplies light to the liquid crystal display panel  59 . 
     The liquid crystal display panel  59  includes an active matrix substrate  51  and a counter substrate  52 , between which liquid crystal (not shown) is filled (these substrates  51  and  52  are fit in a frame-like bezel BZ). On the active matrix substrate  51 , gate signal lines and source signal lines (not shown) are arranged to intersect (cross) each other, and at the intersections between those signal lines, switching devices (for example, thin-film transistors) are arranged for adjustment of the voltage applied to the liquid crystal. 
     A polarizing film  53  is fitted on the light-input side of the active matrix substrate  51 , and another polarizing film  53  is fitted on the light-output side of the counter substrate  52  The liquid crystal display panel  59  described above displays an image by exploiting the variation of transmittance resulting from the inclination of liquid crystal molecules. 
     Next, a description will be given of the backlight unit  49 , which is located directly under the liquid crystal display panel  59  and which supplies light (backlight BL) to the liquid crystal display panel  59 . The backlight unit  49  includes an LED module (light-emitting module) MJ, a backlight chassis  41 , a diffusive sheet  44 , a prism sheet  45 , and a prism sheet  46 . 
     The LED module MJ includes a mounting board  12  and an LED (light-emitting diodes)  11 . 
     The mounting board  12  is, for example, a rectangular board, and has a plurality of electrodes (not shown) arranged on a mounting surface  12 U. On these electrodes, LEDs  11 , as light-emitting devices, are fitted. The electrodes are arranged along two intersecting (for example, mutually perpendicular) directions (that is, they are in a lattice arrangement) on the mounting surface  12 U of a single mounting board  12 . 
     Thus, the LEDs  11  are fitted on the electrodes as shown in  FIG. 18 , and when the LEDs  11  emit light, the light from the plurality of LEDs  11  gathers to form planar light PL. With respect to the arrangement of the electrodes (and hence the LEDs  11 ), of the two intersecting directions, the one along which the larger number of electrodes are arranged side by side will be referred to as the X direction, and the other along which the smaller number of them are arranged will be referred to as the Y direction; the direction intersecting both the X and Y directions will be referred to as the Z direction (the X direction corresponds to the longer sides of the screen of the liquid crystal display panel  59 , and the Y direction corresponds to the shorter sides of the screen of the liquid crystal display panel  59 ). 
     The LED  11  is a light sources (light-emitting device, point light source), and emits light by receiving electric current via the electrodes on the mounting board  12 . The LED  11  may be of any of many various types. For example, the LED  11  may be one including a blue-light-emitting LED chip (light-emitting chip) combined with a phosphor (fluorescent substance) receiving the light from the LED chip and emitting yellow light by fluorescence (there is no particular restriction on the number of LED chips). This LED  11  produces white light by mixing the light from the blue-light-emitting LED chip with the fluorescent light (an LED  11  emitting white light is occasionally referred to as an LED  11 W). 
     The LED  11  may include no phosphor at all. In that case, the LED  11 W includes a red LED chip emitting red light, a green LED chip emitting green light, and a blue LED chip emitting blue light, and produces white light by mixing together the light from all those LED chips. 
     The LED  11  does not necessarily have to be a white-light LED  11 W; it may instead be, for example, a combination of a red-light-emitting LED  11 R, a green-light-emitting LED  11 G, and a blue-light-emitting LED  11 B. In that case, it is preferable that these red-light-emitting, green-light-emitting, and blue-light-emitting LEDs  11 R,  11 G, and  11 B be arranged comparatively close together so that the light from them may mix to produce white light. 
     As shown in  FIG. 17 , the backlight chassis  41  is a box-like member, and accommodates the LED module MJ on its bottom surface  41 B. The bottom surface  41 B of the backlight chassis  41  and the mounting board  12  of the LED module MJ are fastened together, for example, by rivets (not shown). 
     The diffusive sheet  44  is a flat optical sheet which is laid over the mounting surface  12 U over which the LEDs  11  are mounted. The diffusive sheet  44  receives the light emitted from the LED module MJ and diffuses it. That is, the diffusive sheet  44  diffuses the planar light formed by the LED module MJ to illuminate the entire area of the liquid crystal display panel  59 . 
     The prism sheets  45  and  46  are optical sheets which have prism shapes within the sheet plane and which deflect the radiation characteristics of light, and are so located as to cover the diffusive sheet  44 . Thus, the prism sheets  45  and  46  condense the light emanating from the diffusive sheet  44  and increase its luminosity. The directions in which the light condensed by the prism sheets  45  and  46 , respectively, is made to diverge are in an intersecting relationship. 
     The backlight unit  49  described above shines the planar light formed by the LED module MJ through the plurality of optical sheets  44  to  46  to supply it to the liquid crystal display panel  59 . Thus, receiving backlight BL from the backlight unit  49 , the non-luminous liquid crystal display panel  59  provides enhanced display performance. 
     As shown in a block diagram in  FIG. 19 , the liquid crystal display apparatus  69  described above includes a control unit  21 , and the control unit  21  comprehensively controls the liquid crystal display apparatus  69  (that is, the liquid crystal display panel  59  and the backlight unit  49 ). 
     More specifically, the control unit  21  includes a video signal processor  22 , a liquid crystal panel controller (LCD controller)  23 , and an LED controller  24  (the liquid crystal display apparatus  69  includes a gate driver  31 , a source driver  32 , and an LED driver  33 , which will be described later) 
     The video signal processor  22  receives an initial image signal (initial image signal F-VD) from an external signal source. The initial image signal F-VD is, for example, a television signal, and includes a video signal and a synchronizing signal synchronous with the video signal (the video signal is composed of, for example, a red video signal, a green video signal, a blue video signal, and a luminance signal). 
     From the synchronizing signal, the video signal processor  22  generates new synchronizing signals (a clock signal CLK, a vertical synchronizing signal VS, a horizontal synchronizing signal HS, etc.) for image display on the liquid crystal display panel  59 . The video signal processor  22  then transmits the generated new synchronizing signals to the LCD controller  23  and the LED controller  24 . 
     The video signal processor  22  splits the received initial image signal F-VD into a signal VD-Sp suitable for the driving of the liquid crystal display panel  59  and a signal VD-Sd suitable for the driving of the backlight unit  49  (more specifically, the LEDs  11 ). The video signal processor  22  then transmits the separator signal VD-Sp to the LCD controller  23  and the separator signal VD-Sd to the LED controller  24 . 
     From the clock signal CLK, the vertical synchronizing signal VS, the horizontal synchronizing signal HS, etc. transmitted from the video signal processor  22 , the LCD controller  23  generates timing signals for controlling the gate driver  31  and the source driver  32  (the timing signal corresponding to the gate driver  31  will be referred to as the timing signal G-TS, and the timing signal corresponding to the source driver  32  will be referred to as the timing signal S-TS). 
     On one hand, the LCD controller  23  transmits the timing signal G-TS to the gate driver  31 ; on the other hand, the LCD controller  23  transmits the timing signal S-TS and the separator signal VD-Sp to the source driver  32 . 
     Thus, by using the two timing signals G-TS and S-TS and the separator signal VD-Sp, the source driver  32  and the gate driver  31  control the image on the liquid crystal display panel  59 . 
     The LED controller  24  includes an LED driver controller  25  and a pulse width modulator  26 . 
     The LED driver controller  25  transmits the separator signal VD-Sd received from the video signal processor  22  to the pulse width modulator  26 . The LED driver controller  25  also generates from the synchronizing signals (the clock signal CLK, the vertical synchronizing signal VS, the horizontal synchronizing signal HS, etc.) a lighting timing signal L-TS for the LEDs  11  and transmits it to the LED driver  33 . 
     Based on the received separator signal VD-Sd, the pulse width modulator  26  adjusts the light emission duration of the LEDs  11  by a pulse width modulation (PWM) method (a signal used in such pulse width modulation is referred to as a PWM signal). More specifically, the pulse width modulator  26  transmits a PWM signal suitable for the light emission control of the LEDs  11  to the LED driver  33 . 
     Thus, based on the signals (the PWM signal and the timing signal L-TS) from the LED controller  24 , the LED driver  33  controls the lighting of the LEDs  11 . 
     Now, a description will be given of the arrangement of the LEDs  11  included in the liquid crystal display apparatus  69 , in particular the backlight unit  49 , described above (the control unit  21 , which controls the light emission of the LEDs  11 , can not only control all the LEDs  11  collectively but also control them individually; that is, it has a so-called local dimming function). 
     As shown in  FIG. 18 , simply arranging the plurality of LEDs  11  two-dimensionally permits the light from them to gather into planar light. Here, the LEDs  11  can be arranged two-dimensionally in many ways.  FIG. 1  shows one example of how the LEDs  11  are arranged (in a plan view like  FIG. 1 , no planar light is illustrated; it should still be interpreted that planar light having a shape similar to the shape around the edge of the group of LEDs  11  in a lattice arrangement is produced). 
     More specifically, in the backlight unit  49  shown in  FIG. 1  (Example 1), rows (X-direction rows) in which LEDs  11  are arranged at the same positions with respect to the Y direction and side by side along the X direction are arranged side by side in the Y direction so that a plurality of LEDs  11  are in a lattice-like (like a lattice forming a matrix) planar arrangement. In other words, rows (Y-direction rows) in which LEDs  11  are arranged at the same positions with respect to the X direction and side by side along the Y direction are arranged side by side in the X direction so that a plurality of LEDs  11  are in a lattice-like planar arrangement. 
     Moreover, whereas the intervals between the Y-direction rows are equal, namely Px-s 1 , the intervals between the X-direction rows are not equal (that is, there are a plurality of kinds of intervals among the intervals between the X-direction rows). Specifically, the interval between the X-direction rows corresponding to near the planar center of the planar light is shorter than the interval between the X-direction rows corresponding to other than near the planar center of the planar light. 
     For example, as shown in  FIG. 1 , in a group of LEDs  11  in a lattice arrangement with 16 of them in the X direction and 8 of them in the Y direction, the two X-direction rows located fourth from the two outermost rows in the Y direction produce the light near the planar center of the planar light (whereas the other X-direction rows than those two produce the light elsewhere than near the planar center of the planar light). Thus, the interval Py-a between those two X-direction rows is shorter than the intervals Py-b and Py-c between the other adjacent X-direction rows (the intervals having the relationship interval Py-a&lt;interval Py-b&lt;interval Py-c). 
     With this lattice arrangement, the planar light has higher luminance near the planar center than in a region elsewhere than near the center (“near the planar center” denotes “an arbitrary region including the center of the plane of the planar light”). With this planar light, owing to the characteristics of the human visual sense, almost no lowering in luminance is perceived in a region elsewhere than at the planer center of the planar light (and hence the liquid crystal display panel  59  receiving the planar light). That is, the entire planar light is perceived to have uniform luminance (the planar light has comparatively high uniformity). 
     This helps reduce the number of LEDs  11  corresponding to the region other than the planar center of the planar light. Specifically, for example, consider a case where such planar light is needed as would be obtained when LEDs  11  were arranged at equal intervals in the X and Y directions, with 18 of them in the X direction and 10 of them in the Y direction. Providing a plurality of kinds of intervals among the intervals between the LEDs  11  in the Y direction makes it less likely for humans to perceive a significant difference in the luminance of the planar light even when the LEDs  11  are in a lattice arrangement with 16 of them in the X direction and 8 of them in the Y direction as shown in  FIG. 1 . 
     That is, in the backlight unit  49 , the LEDs  11  are so arranged that humans perceive the entire planar light to have uniform luminance. Accordingly, in the backlight unit  49 , the planar light is divided into a plurality of sections, and a plurality of LEDs  11  are arranged on such a principle that luminance is varied section by section (an arrangement of LEDs  11  that divides planar light into a plurality of sections and that permits luminance to be varied for each of those sections will be referred to as a luminance-varying system, which can thus produce planar light in many ways to suite various purposes). 
     For example, when the LEDs  11  are arranged as shown in  FIG. 1 , the planar light is divided into a section (central section) in a region extending in the X direction and a section (peripheral section) in the region other than that region. Here, the interval Py-a between the X-direction rows that produce the light corresponding to the central region is made shorter than the intervals Py-b and Py-c between the other X-direction rows. That is, the plurality of LEDs  11  are arranged with a difference in density (the distribution density of the LEDs  11 ). This permits humans to perceive the entire planar light to have uniform luminance. 
     In a case where the planar light is divided into a central section in a region including the planar center and a peripheral section in the other region, the peripheral section may be further divided into a plurality of subsections. The intervals between the LEDs  11  that produce the light in the divided subsections may differ from one peripheral subsection to another (for example, when the LEDs  11  are arranged as shown in  FIG. 1 , the interval Py-b between the X-direction rows corresponding to the peripheral subsection near the central section is shorter than the interval Py-c between the X-direction rows corresponding to the other peripheral subsection). 
     Arranging the LEDs  11  in this way makes flexible the luminance distribution of the planar light within the plane, and thus more reliably permits humans to perceive the entire planar light to have uniform luminance. 
     For the purpose of permitting humans to perceive the entire planar light to have uniform luminance, the LEDs  11  may be arranged not only as shown in  FIG. 1 , which shows Example 1 (EX 1), but in many other ways. For one example, the LEDs  11  may be arranged as shown in  FIG. 2  (Example 2). 
     More specifically, whereas the intervals between the X-direction rows are equal, namely Py-s 1 , the intervals between the Y-direction rows are not equal (that is, there are a plurality of kinds of intervals among the intervals between the Y-direction rows). Specifically, the interval between the Y-direction rows corresponding to near the center of the planar light is shorter than the interval between the Y-direction rows corresponding to elsewhere than near the center of the planar light. 
     For example, as shown in  FIG. 2 , in a group of LEDs  11  in a lattice arrangement with 16 of them in the X direction and 8 of them in the Y direction, the four Y-direction rows located seventh and eighth from the two outermost rows in the X direction produce the light near the planar center of the planar light (whereas the other Y-direction rows than those four produce the light elsewhere than near the planar center of the planar light). Thus, the interval Px-a between those four Y-direction rows is shorter than the intervals Px-b and Px-c between the other adjacent Y-direction rows (the intervals having the relationship interval Px-a&lt;interval Px-b&lt;interval Px-c). 
     That is, when the LEDs  11  are arranged in this way, the planar light is divided into a section (central section) in a region extending in the Y direction and a section (peripheral section) in the region other than that region. Here, the interval Px-a between the Y-direction rows that produce the light corresponding to the central region is made shorter than the intervals Px-b and Px-c between the other Y-direction rows, and this permits humans to perceive the entire planar light to have uniform luminance. 
     The LEDs  11  may be arranged as shown in  FIG. 3  (Example 3). More specifically, the intervals between the X-direction rows are not equal, nor are the intervals between the Y-direction rows (that is, there are a plurality of kinds of intervals among the intervals between the X-direction rows, and there are a plurality of kinds of intervals among the intervals between the Y-direction rows). 
     Specifically, the interval between the X-direction rows corresponding to near the center of the planar light is shorter than the interval between the X-direction rows corresponding to elsewhere than near the center of the planar light, and in addition the interval between the Y-direction rows corresponding to near the center of the planar light is shorter than the interval between the Y-direction rows corresponding to elsewhere than near the center of the planar light. 
     Thus, the arrangement of the LEDs  11  in  FIG. 3  is, so to speak, a mixture of the arrangements of the LEDs  11  in  FIGS. 1 and 2 . Accordingly, in a group of LEDs  11  in a lattice arrangement with 16 of them in the X direction and 8 of them in the Y direction, the two X-direction rows located fourth from the two outermost rows in the Y direction and the four Y-direction rows located seventh and eighth from the two outermost rows in the X direction produce the light near the planar center of the planar light (whereas the LEDs  11  in the rows other than those just mentioned produce the light elsewhere than near the planar center of the planar light). 
     Here, the interval Py-a between the two X-direction rows located fourth from the two outermost rows in the Y direction is shorter than the intervals Py-b and Py-c between the other adjacent X-direction rows. In addition, the interval Px-a between the four Y-direction rows located seventh and eighths from the two outermost rows in the X direction is shorter than the intervals Px-b and Px-c between the other adjacent Y-direction rows. 
     That is, in a case where LEDs  11  are arranged in intersecting X and Y directions, there may be a plurality of kinds of intervals among the intervals between the LEDs  11  arranged in the two, X and Y, directions (i.e., there need to be a plurality of kinds of intervals among the intervals between the LEDs  11  arranged in at least one of the X and Y directions). Also this arrangement of the LEDs  11  permits, like those of Examples 1 and 2, humans to perceive the entire planar light to have uniform luminance. 
     In the lattice arrangements of the LEDs  11  shown in  FIGS. 1 to 3 , the positions of the LEDs  11  with respect to the X direction between adjacent X-direction rows are the same from one X-direction row to the next (in other words, the positions of the LEDs  11  with respect to the Y direction between adjacent Y-direction rows are the same from one Y-direction row to the next). Thus, the shape of the sections defined by the dash-and-dot lines indicating the X- and Y-direction rows (the shape of each segment of the lattice) is rectangular. 
     The arrangement of the LEDs  11  is, however, not limited to matrix-like lattice arrangements as shown in  FIGS. 1 to 3 . The LEDs  11  may instead be arranged, for example, in a staggering lattice arrangement as shown in  FIG. 4  (Example 4). That is, the positions of the LEDs  11  with respect to the X direction between adjacent X-direction rows may differ from one X-direction row to the next (in other words, the positions of the LEDs  11  with respect to the Y direction in adjacent Y-direction rows may differ from one Y-direction row to the next). 
     More specifically, whereas the intervals between the Y-direction rows are equal, namely Px-s 2 , the intervals between the X-direction rows are not equal. Specifically, as in  FIG. 1 , the interval between the X-direction rows corresponding to near the planar center of the planar light is shorter than the interval between the X-direction rows corresponding to elsewhere than near the planar center of the planar light. 
     For example, as shown in  FIG. 4 , starting at one outermost row in the Y direction, X-direction rows with 14 LEDs  11  and X-direction rows with 15 LEDs  11  are arranged alternately side by side in the Y direction to form a lattice arrangement composed of a total of nine X-direction rows. In this group of LEDs  11  in a lattice arrangement, the three X-direction rows located fourth, fifth, and sixth from one outermost row in the Y direction produce the light near the planar center of the planar light (whereas the X-direction rows other than those three produce the light elsewhere than near the planar center of the planar light). Thus, the interval Py-d between those three X-direction rows is shorter than the intervals Py-e, Py-f, and Py-g between the other adjacent X-direction rows (the intervals having the relationship interval Py-d&lt;interval Py-e&lt;interval Py-f&lt;interval Py-g). 
     That is, when the LEDs  11  are arranged as shown in  FIG. 4 , the planar light is divided into a section (central section) in a region including the planar center and extending in the X direction and a section (peripheral section) in the region other than that region. The interval Py-d between the X-direction rows that produce the light corresponding to the central section is made shorter than the intervals between the other X-direction rows (intervals Py-e, Py-f, and Py-g). This permits humans to perceive the entire planar light to have uniform luminance. 
     The LEDs  11  may be arranged as shown in  FIG. 5  (Example 5). More specifically, whereas the intervals between the X-direction rows are equal, namely Py-s 2 , the intervals between the Y-direction rows are not equal. Specifically, the interval between the Y-direction rows corresponding to near the center of the planar light is shorter than the interval between the Y-direction rows corresponding to elsewhere than near the center of the planar light. 
     For example, as shown in  FIG. 5 , starting at one outermost row in the X direction, Y-direction rows with four LEDs  11  and Y-direction rows with five LEDs  11  are arranged alternately side by side in the X direction to form a lattice arrangement composed of a total of 29 Y-direction rows. In this group of LEDs  11  in a lattice arrangement, the seven Y-direction rows located 12th to 18th from one outermost row in the X direction produce the light near the planar center of the planar light (whereas the Y-direction rows other than those seven produce the light elsewhere than near the planar center of the planar light). Thus, the interval Px-d between those seven Y-direction rows is shorter than the intervals Px-e, Px-f, Px-g, and Px-h between the other adjacent X-direction rows (the intervals having the relationship interval Px-d&lt;interval Px-e&lt;interval Px-f&lt;interval Px-g&lt;interval Px-h). 
     That is, when the LEDs  11  are arranged in this way, the planar light is divided into a section (central section) in a region including the planar center and extending in the Y direction and a section (peripheral section) in the region other than that region. The interval Px-d between the Y-direction rows that produce the light corresponding to the central section is made shorter than the intervals between the other Y-direction rows (intervals Px-e, Px-f, Px-g, and Px-h). This permits humans to perceive the entire planar light to have uniform luminance. 
     The LEDs  11  may be arranged as shown in  FIG. 6  (Example 6). More specifically, the LEDs  11  are arranged in a lattice arrangement in which the positions of the LEDs  11  with respect to the X direction between adjacent X-direction rows differ from one X-direction row to the next and in addition the positions of the LEDs  11  with respect to the Y direction between adjacent Y-direction rows differ from one Y-direction row to the next. Thus, the intervals between the X-direction rows are not equal, nor are the intervals between the Y-direction rows. 
     Specifically, the interval between the X-direction rows corresponding to near the center of the planar light is shorter than the interval between the X-direction rows corresponding to other than near the center of the planar light, and in addition the interval between the Y-direction rows corresponding to near the center of the planar light is shorter than the interval between the Y-direction rows corresponding to elsewhere than near the center of the planar light. 
     Thus, the arrangement of the LEDs  11  in  FIG. 6  is, so to speak, a mixture of the arrangements of the LEDs  11  in  FIGS. 4 and 5 . More specifically, X-direction rows with 14 LEDs  11  and X-direction rows with 15 LEDs  11  are arranged alternately side by side in the Y direction to form a lattice arrangement composed of a total of nine X-direction rows (in other words, Y-direction rows with four LEDs  11  and Y-direction rows with five LEDs  11  are arranged alternately side by side in the X direction to form a lattice arrangement composed of a total of 29 Y-direction rows). 
     In this group of LEDs  11  in a lattice arrangement, the three X-direction rows located fourth, fifth, and sixth from one outermost row in the Y direction and the seven Y-direction rows located 12th to 18th from one outermost row in the X direction produce the light near the planar center of the planar light (whereas the LEDs  11  in the rows other than those just mentioned produce the light elsewhere than near the planar center of the planar light). 
     Thus, the interval Py-d between the three X-direction rows located at fourth, fifth, and sixth from one outermost row in the Y direction is shorter than the intervals Py-e, Py-f, and Py-g between the other adjacent X-direction rows. In addition, the interval Px-d between seven Y-direction rows located at 12th to 18th from one outermost row in the X direction is shorter than the intervals Px-e, Px-f, Px-g, and Px-h between the other adjacent X-direction rows. 
     That is, in a case where LEDs  11  are arranged in intersecting X and Y directions, there may be a plurality of kinds of intervals among the intervals between the LEDs  11  arranged in the two, X and Y, directions. Also this arrangement of the LEDs  11  permits, like those of Examples 5 and 6, humans to perceive the entire planar light to have uniform luminance. 
     As shown in  FIG. 7  (Example 7), a group of LEDs  11  in a staggered arrangement may further include one or more LEDs (hatched by dots) that are not included in any X- or Y-direction row. Even a group of LEDs  11  in a matrix-like arrangement as shown in  FIGS. 1 to 3  may include one or more LEDs that are not included in any X- or Y-direction row. Providing such irregularly arranged LEDs  11  increases flexibility in the adjustment of the luminance of the planar light (i.e., makes finer luminance adjustment possible). 
     For a liquid crystal display apparatus  69  with a 52-inch screen, comparing the number of LEDs  11  arranged at irregular pitches in the Y direction as in Example 1 with the number of LEDs arranged at equal intervals in both X and Y directions reveals that the number of LEDs  11  in Example 1 is as small as approximately 83% of the number in the compared arrangement. 
     In one specific example, whereas, in the compared arrangement, 24 LEDs in the X direction and 12 LEDs in the Y direction, and thus a total of 288 LEDs, are arranged, in Example 1, the LEDs in each outermost X-direction row (and thus a total of two X-direction rows) are eliminated and the remaining 240 (24×10) LEDs are arranged unequally. 
     When the intervals at which the LEDs are arranged in the compared arrangement is compared with the shorter intervals (for example, the interval Py-a) at which the LEDs  11  are arranged in Example 1, the latter is shorter. 
     [Embodiment 2] 
     A second embodiment of the invention will now be described. Such members as have similar functions to those used in Example 1 are identified by the same reference signs, and no overlapping descriptions will be repeated. 
     The arrangement of the LEDs  11  in Embodiment 1 has as its purpose to permit humans to perceive the entire planar light to have uniform luminance. It may be for another purpose, for example to obtain increased luminance in a particular region in planar light, that the LEDs  11  are arranged so as to divide planar light into a plurality of sections to permit luminance to be varied section by section. Examples are arrangements of the LEDs  11  as shown in  FIGS. 8 to 14 . 
     In the arrangement of the LEDs  11  in  FIG. 8  (Example 8), as in the arrangement of the LEDs in Example 1 shown in  FIG. 1 , rows (X-direction rows) in which LEDs  11  are arranged at the same positions with respect to the Y direction and side by side along the X direction are arranged side by side in the Y direction so that a plurality of LEDs  11  are in a lattice-like (also the arrangements of the LEDs  11  in Examples 9 and 10 shown in  FIGS. 9 and 10 , respectively, described later, like that of Example 8, are matrix-like lattice arrangements in which the positions of the LEDs  11  with respect to the X direction between adjacent X-direction rows are the same from one X-direction row to the next). 
     Moreover, in the arrangement of the LEDs  11  in  FIG. 8 , as in the arrangement of the LEDs in  FIG. 1 , whereas the intervals between the Y-direction rows are equal, namely Px-s 1 , the intervals between the X-direction rows are not equal (that is, there are a plurality of kinds of intervals among the intervals between the X-direction rows). In the arrangement of the LEDs  11  in  FIG. 8 , however, unlike in the arrangement of the LEDs in  FIG. 1 , the interval between the X-direction rows corresponding to near the planar center of the planar light is longer than the interval between the X-direction rows corresponding to elsewhere than near the planar center of the planar light. 
     For example, as shown in  FIG. 8 , in a group of LEDs  11  in a lattice arrangement with 16 of them in the X direction and 8 of them in the Y direction, the two X-direction rows located fourth from the two outermost rows in the Y direction produce the light near the planar center of the planar light (whereas the other X-direction rows than those two produce the light elsewhere than near the planar center of the planar light). Thus, the interval Py-c′ between those two X-direction rows is longer than the intervals Py-b′ and Py-a′ between the other adjacent X-direction rows (the intervals having the relationship interval Py-c′&gt;interval Py-b′&gt; interval Py-a′). 
     With the LEDs  11  in such a lattice arrangement, the planar light has higher luminance in a peripheral region elsewhere than near the planar center than in a region near the center. Thus, it is possible to prevent insufficient luminance in a peripheral region of the planar light while retaining the uniformity of the planar light. 
     That is, with this arrangement of the LEDs  11 , the planar light is divided into a section (central section) in a region including the planar center and extending in the X direction and a section (peripheral section) in the region other than that region. Here, the intervals Py-a′ and Py-b′ between the X-direction rows that produce the light corresponding to the peripheral section is made smaller than the interval Py-c′ between the X-direction rows that produce the light corresponding to the central section, and this makes it possible to prevent insufficient luminance in a peripheral region of the planar light while retaining the uniformity of the planar light. 
     As in Embodiment 1, in a case where the planar light is divided into a central section in a region including the planar center and a peripheral section in the region other than that region, the peripheral section may be further divided into a plurality of subsections. The intervals of the LEDs  11  that produce the light in the divided peripheral subsections may differ from one peripheral subsection to another (for example, in the arrangement of the LEDs  11  in  FIG. 8 , the interval Py-a′ between the X-direction rows corresponding to the peripheral subsection far from the central section is shorter than the interval Py-b′ between the X-direction rows corresponding to the peripheral subsection near the central section). 
     This arrangement of the LEDs  11  makes flexible the luminance distribution of the planar light within the plane, and thus helps more reliably prevent humans from perceiving insufficient luminance in a peripheral region of the planar light. 
     The LEDs  11  may be arranged as shown in  FIG. 9  (Example 9). In the arrangement of the LEDs  11  in  FIG. 9 , as in the arrangement of the LEDs in Example 2 shown in  FIG. 2 , whereas the intervals between the X-direction rows are equal, namely Py-s 1 , the intervals between the Y-direction rows are not equal (that is, there are a plurality of kinds of intervals among the intervals between the Y-direction rows). In the arrangement of the LEDs  11  in  FIG. 9 , however, unlike in the arrangement of the LEDs in  FIG. 2 , the interval between the Y-direction rows corresponding to near the planar center of the planar light is longer than the interval between the Y-direction rows corresponding to other than near the planar center of the planar light. 
     For example, as shown in  FIG. 9 , in a group of LEDs  11  in a lattice arrangement with 16 of them in the X direction and 8 of them in the Y direction, the four Y-direction rows located seventh and eights from the two outermost rows in the X direction produce the light near the planar center of the planar light (whereas the other Y-direction rows than those four produce the light elsewhere than near the planar center of the planar light). Thus, the interval Px-c′ between those four Y-direction rows is longer than the intervals Px-b′ and Px-a′ between the other adjacent Y-direction rows (the intervals having the relationship interval Px-c′&gt;interval Px-b′&gt;interval Px-a′). 
     That is, with this arrangement of the LEDs  11 , the planar light is divided into a section (central section) in a region including the planar center and extending in the Y direction and a section (peripheral section) in the region other than that region. Here, the intervals Px-a′ and Px-b′ between the Y-direction rows that produce the light corresponding to the peripheral section is made smaller than the interval Px-c′ between the X-direction rows that produce the light corresponding to the central section, and this makes it possible to prevent insufficient luminance in a peripheral region of the planar light while retaining the uniformity of the planar light. 
     The LEDs  11  may be arranged as shown in  FIG. 10  (Example 10). More specifically, in the arrangement of the LEDs  11  in  FIG. 10 , as in the arrangement of the LEDs in  FIG. 3 , the intervals between the X-direction rows are not equal, nor are the intervals between the Y-direction rows (that is, there are a plurality of kinds of intervals among the intervals between the X-direction rows, and in addition there are a plurality of kinds of intervals among the intervals between the Y-direction rows). 
     Here, however, the interval between the X-direction rows corresponding to near the center of the planar light is longer than the interval between the X-direction rows corresponding to elsewhere than near the center of the planar light, and in addition the intervals between the Y-direction rows corresponding to near the center of the planar light is longer than the intervals between the Y-direction rows corresponding to elsewhere than near the center of the planar light. 
     Thus, the arrangement of the LEDs  11  in  FIG. 10  is, so to speak, a mixture of the arrangements of the LEDs  11  in  FIGS. 8 and 9 . Accordingly, in a group of LEDs  11  in a lattice arrangement with 16 of them in the X direction and 8 of them in the Y direction, the two X-direction rows located fourth from the two outermost rows in the Y direction and the four Y-direction rows located seventh and eighth from the two outermost rows in the X direction produce the light near the planar center of the planar light (whereas the LEDs  11  in the rows other than those just mentioned produce the light elsewhere than near the planar center of the planar light). 
     Here, the interval Py-c′ between the two X-direction rows located fourth from the two outermost rows in the Y direction is longer than the intervals Py-b′ and Py-a′ between the other adjacent X-direction rows. In addition, the interval Px-c′ between the four Y-direction rows located seventh and eighths from the two outermost rows in the X direction is longer than the intervals Px-b′ and Px-a′ between the other adjacent Y-direction rows. 
     That is, in a case where LEDs  11  are arranged in intersecting X and Y directions, there may be a plurality of kinds of intervals among the intervals between the LEDs  11  arranged in the two, X and Y, directions (i.e., there need to be a plurality of kinds of intervals among the intervals between the LEDs  11  arranged in at least one of the X and Y directions). Also this arrangement of the LEDs  11 , like those of Examples 8 and 9, makes it possible to prevent insufficient luminance in a peripheral region of the planar light while retaining the uniformity of the planar light. 
     The LEDs  11  may be arranged as shown in  FIG. 11  (Example 11). In the arrangement of the LEDs  11  in  FIG. 11 , as in the arrangement of the LEDs in Example 4 shown in  FIG. 4 , the positions of the LEDs  11  with respect to the X direction in adjacent X-direction rows differ from one X-direction row to the next. In other words, the positions of the LEDs  11  with respect the Y direction in adjacent Y-direction rows differ from one Y-direction row to the next (also in Examples 12 and 13 shown in  FIGS. 12 and 13  described later, as in Example 11, the LEDs  11  are arranged in a staggered lattice arrangement). 
     More specifically, whereas the intervals between the Y-direction rows are equal, namely Px-s 2 , the intervals between the X-direction rows are not equal. In the arrangement of the LEDs  11  in  FIG. 11 , however, unlike in the arrangement of LEDs in  FIG. 4 , the intervals between the X-direction rows corresponding to near the planar center of the planar light is longer than the intervals between the X-direction rows corresponding to elsewhere than near the planar center of the planar light. 
     For example, as shown in  FIG. 11 , starting at one outermost row in the Y direction, X-direction rows with 14 LEDs  11  and X-direction rows with 15 LEDs  11  are arranged alternately side by side in the Y direction to form a lattice arrangement composed of a total of nine X-direction rows. In this group of LEDs  11  in a lattice arrangement, the three X-direction rows located fourth, fifth, and sixth from one outermost row in the Y direction produce the light near the planar center of the planar light (whereas the X-direction rows other than those three produce the light elsewhere than near the planar center of the planar light). Thus, the interval Py-g′ between those three X-direction rows is longer than the intervals Py-f′, Py-e′, and Py-d′ between the other adjacent X-direction rows (the intervals having the relationship interval Py-d′&lt;interval Py-e′&lt;interval Py-f′&lt;interval Py-g′). 
     That is, with this arrangement of the LEDs  11 , the planar light is divided into a section (central section) in a region including the planar center and extending in the X direction and a section (peripheral section) in the region other than that region. The intervals Py-d′, Py-e′, and Py-f′ between the X-direction rows that produce the light corresponding to the peripheral section is made shorter than the interval Py-g′ between the X-direction rows that produce the light corresponding to the central section, and this makes it possible to prevent insufficient luminance in a peripheral region of the planar light while retaining the uniformity of the planar light. 
     The LEDs  11  may be arranged as shown in  FIG. 12  (Example 12), In the arrangement of the LEDs  11  in  FIG. 12 , as in the arrangement of the LEDs in Example 5 shown in  FIG. 5 , whereas the intervals between the X-direction rows are equal, namely Py-s 2 , the intervals between the Y-direction rows are not equal. In the arrangement of the LEDs  11  in  FIG. 12 , however, unlike in the arrangement of the LEDs in  FIG. 5 , the intervals between the Y-direction rows corresponding to near the planar center of the planar light is longer than the intervals between the Y-direction rows corresponding to elsewhere than near the planar center of the planar light. 
     For example, as shown in  FIG. 12 , starting at one outermost row in the X direction, Y-direction rows with four LEDs  11  and Y-direction rows with five LEDs  11  are arranged alternately side by side in the X direction to form a lattice arrangement composed of a total of 29 Y-direction rows. In this group of LEDs  11  in a lattice arrangement, the five Y-direction rows located 13th to 17th from one outermost row in the X direction produce the light near the planar center of the planar light (whereas the Y-direction rows other than those five produce the light elsewhere than near the planar center of the planar light). Thus, the interval Px-h′ between those five Y-direction rows is longer than the intervals Px-d′, Px-e′, Px-f′, and Px-g′ between the other adjacent Y-direction rows (the intervals having the relationship interval Px-d′&lt;interval Px-e′&lt;interval Px-f′&lt;interval Px-g′&lt;interval Px-h′). 
     That is, with this arrangement of the LEDs  11 , the planar light is divided into a section (central section) in a region including the planar center and extending in the Y direction and a section (peripheral section) in the region other than that region. The intervals Px-d′, Px-e′, Px-f′, and Px-g′ between the Y-direction rows that produce the light corresponding to the peripheral section are made shorter than the interval Px-h′ between the Y-direction rows that produce the light corresponding to the central section. This makes it possible to prevent insufficient luminance in a peripheral region of the planar light while retaining the uniformity of the planar light. 
     The LEDs  11  may be arranged as shown in  FIG. 13  (Example 13). More specifically, the arrangement of the LEDs  11  in  FIG. 13  is, like the arrangement of the LEDs  11  in Example 6 shown in  FIG. 6 , a lattice arrangement in which the positions of the LEDs  11  with respect to the X direction in adjacent X-direction rows differ from one X-direction row to the next, and in addition the positions of the LEDs  11  with respect to the Y direction in adjacent Y-direction rows differ from one Y-direction row to the next. 
     Here, however, the interval between the X-direction rows corresponding to near the center of the planar light is longer than the interval between the X-direction rows corresponding to elsewhere than near the center of the planar light, and in addition the intervals between the Y-direction rows corresponding to near the center of the planar light is longer than the intervals between the Y-direction rows corresponding to elsewhere than near the center of the planar light. 
     Thus, the arrangement of the LEDs  11  in  FIG. 13  is, so to speak, a mixture of the arrangements of the LEDs  11  in  FIGS. 11 and 12 . More specifically, X-direction rows with 14 LEDs  11  and X-direction rows with 15 LEDs  11  are arranged alternately side by side in the Y direction to form a lattice arrangement composed of a total of nine X-direction rows (in other words, Y-direction rows with four LEDs  11  and Y-direction rows with five LEDs  11  are arranged alternately side by side in the X direction to form a lattice arrangement composed of a total of 29 Y-direction rows). 
     In this group of LEDs  11  in a lattice arrangement, the three X-direction rows located fourth, fifth, and sixth from one outermost row in the Y direction and the five Y-direction rows located 13th to 17th from one outermost row in the X direction produce the light near the planar center of the planar light (whereas the LEDs  11  in the rows other than those just mentioned produce the light elsewhere than near the planar center of the planar light). 
     Thus, the interval Py-g′ between the three X-direction rows located at fourth, fifth, and sixth from one outermost row in the Y direction is longer than the intervals Py-d′, Py-e′, and Py-f′ between the other adjacent X-direction rows. In addition, the interval Px-h′ between five Y-direction rows located at 13th to 17th from one outermost row in the X direction are longer than the intervals Px-d′, Px-e′, Px-f′, and Px-g′ between the other adjacent Y-direction rows. 
     That is, in a case where LEDs  11  are arranged in intersecting X and Y directions, there may be a plurality of kinds of intervals among the intervals between the LEDs  11  arranged in the two, X and Y, directions. Also this arrangement of the LEDs  11 , like those of Examples 11 and 12, makes it possible to prevent insufficient luminance in a peripheral region of the planar light while retaining the uniformity of the planar light. 
     As shown in  FIG. 14  (Example  14 ), a group of LEDs  11  in a staggered arrangement may further include one or more LEDs (hatched by dots) that are not included in any X- or Y-direction row. Even a group of LEDs  11  in a matrix-like arrangement as shown in  FIGS. 8 to 10  may include one or more LEDs that are not included in any X- or Y-direction row. Providing such irregularly arranged LEDs  11  increases flexibility in the adjustment of the luminance of the planar light (i.e., makes finer luminance adjustment possible). 
     Specific values for the intervals at which the LEDs  11  are arranged in Embodiment 2 can be set as desired. To prevent an excessive lowering of luminance near the center of the planar light, it is preferable to set those value, for example, close to the intervals at which the LEDs  11  that produce the light near the center of the planar light are arranged in Embodiment 1 (the LEDs  11  need to be arranged, however, with consideration given to the cost balance of the backlight unit  49 , the balance of power consumption, and the balance of the uniformity of the planar light). 
     [Embodiment 3] 
     A third embodiment of the invention will now be described. Such members as have similar functions to those used in Examples 1 and 2 are identified by the same reference signs, and no overlapping descriptions will be repeated. 
     In Examples 1 to 6 and Examples 8 to 13 according to Embodiments 1 and 2, on the mounting surface  12 U of the mounting board  12 , the X- and Y-direction rows, which extend over its entire area in the X and Y directions respectively, include all the LEDs  11 . This, however, is not meant as any limitation. Specifically, the LEDs  11  may be arranged on any principle other than the regularity of X- and Y-direction rows. For example, the LEDs  11  may be arranged as shown in  FIG. 15  (Example 15). 
     As shown in  FIG. 15 , a plurality of LEDs  11  are in a planar arrangement, and the arrangement surface of this planar arrangement includes a plurality of divided regions  13  divided like a lattice (see the regions divided by dotted lines). The LEDs  11  are so arranged as to be located within those divided regions  13 . There are a plurality of kinds of numbers among the numbers of LEDs  11  located within the divided regions  13 . This permits the LEDs  11  to be arranged with a difference in density. 
     Specifically, in a case where, as in Embodiment 1, the purpose is to permit humans to perceive entire planar light to have uniform luminosity, as shown in  FIG. 15 , preferably, the number of LEDs  11  included in divided regions  13  near the center of the mounting surface  12 U is made greater than the number of LEDs  11  included in divided regions  13  near the periphery of the mounting surface  12 U. More specifically, when the divided regions  13  in which the LEDs  11  that produce the light near the planar center of the planar light are located are referred to as the central divided regions  13 C, and the divided regions  13  in which the LEDs  11  that produce the peripheral light elsewhere than near the planar center of the planar light are located are referred to as the peripheral divided regions  13 T, then, preferably, the number of LEDs  11  included in the central divided regions  13 C is greater than the number of LEDs  11  included in the peripheral divided regions  13 T. 
     On the other hand, in a case where, as in Embodiment 2, the purpose is to prevent insufficient luminance in a peripheral region of the planar light while retaining the uniformity of the planar light, as shown in  FIG. 16  (Example 16), preferably, the number of LEDs  11  included in divided regions  13  near the periphery of the mounting surface  12 U is made greater than the number of LEDs  11  included in divided regions  13  near the center of the mounting surface  12 U. More specifically, preferably, the number of LEDs  11  included in the peripheral divided regions  13 T is greater than the number of LEDs  11  included in the central divided regions  13 C. 
     [Embodiment 4] 
     A fourth embodiment of the invention will now be described. Such members as have similar functions to those used in Examples 1 to 3 are identified by the same reference signs, and no overlapping descriptions will be repeated. 
     In Embodiments 1 to 3, all the LEDs  11  in a lattice arrangement emit light in the same direction, and the light gathers to produce planar light (see  FIG. 18 ). This, however, is not meant to limit how planar light is produced. For example, as shown in  FIG. 20 , it is also possible to arrange LEDs  11  in one row along the X direction (a single LED module MJx) and in one row along the Y direction (a single LED module MJy) and make them emit light in different (for example, intersecting) directions so that the light overlaps to form planar light. 
     The planar light shown in  FIG. 20 , however, does not tend to travel toward the optical sheers  44  to  46  and hence toward liquid crystal display panel  59 . As a remedy, preferably, as shown in  FIG. 21 , an LED module MJx in which LEDs  11  arranged side by side along the X direction are mounted on a mounting board  12  and an LED module MJy in which LEDs  11  arranged side by side along the Y direction are mounted on a mounting board  12  are arranged at intersecting side edges of a light guide plate  42  (i.e., preferably, one row of LEDs  11  arranged along the X direction and one row of LEDs  11  arranged along the Y direction intersect such that LEDs  11  are arranged two-dimensionally). 
     With this design, the light from the two LED modules MJ (MJx and MJy) is reflected repeatedly inside the light guide plate  42  and planar light emerges through the top face  42 U of the light guide plate  42 . Thus, in the structure shown in  FIG. 21  where the optical sheets  44  to  46  and the liquid crystal display panel  59  are stacked on top of the top face  42 U of the light guide plate  42 , these are supplied with planar light (the light that leaks through the bottom face  42 B of the light guide plate  42  is reflected on a reflective sheet  43  to travel back into the light guide plate  42 ). 
     In a case where, as in Embodiment 1, the purpose is to permit humans to perceive entire planar light to have uniform luminance, preferably, for example as shown in  FIG. 22  (Example 17), among the LEDs  11  arranged in a row in the LED module MJx, the interval between the LEDs  11  near the center is made shorter than the interval between the LEDs  11  near the periphery, and among the LEDs  11  arranged in a row in the LED module MJy, the interval between the LEDs  11  near the center is made shorter than the interval between the LEDs  11  near the periphery. 
     This, however, is not meant to be any limitation. The backlight unit  49  may incorporate an LED module MJx having LEDs  11  arranged with a difference in density as shown in  FIG. 22  in combination with an LED module MJy having LEDs  11  arranged with uniform density (i.e., an LED module MJy having LEDs  11  arranged at equal intervals). Reversely, the backlight unit  49  may incorporate an LED module MJy having LEDs  11  arranged with a difference in density as shown in  FIG. 22  in combination with an LED module MJx having LEDs  11  arranged with uniform density. 
     On the other hand, in a case where the purpose is to prevent insufficient luminance in a peripheral region of planar light while retaining the uniformity of the planar light, preferably, for example as shown in  FIG. 23  (Example 18), among the LEDs  11  arranged in a row in the LED module MJx, the interval between the LEDs  11  near the center is made longer than the interval between the LEDs  11  near the periphery, and among the LEDs  11  arranged in a row in the LED module MJy, the interval between the LEDs  11  near the center is made longer than the interval between the LEDs  11  near the periphery. 
     This, however, is not meant to be any limitation. The backlight unit  49  may incorporate an LED module MJx having LEDs  11  arranged with a difference in density as shown in  FIG. 23  in combination with an LED module MJy having LEDs  11  arranged with uniform density (i.e., an LED module MJy having LEDs  11  arranged at equal intervals). Reversely, the backlight unit  49  may incorporate an LED module MJy having LEDs  11  arranged with a difference in density as shown in  FIG. 23  in combination with an LED module MJx having LEDs  11  arranged with uniform density. 
     Although the LED modules MJ are arranged in an L shape in  FIGS. 22 and 23 , this is not meant as any limitation. For example, as shown in  FIG. 24  (Example 19), two LED modules MJx may be arranged opposite each other across the light guide plate  42  (i.e., LED modules MJx may be arranged one at each of opposite side edges of the light guide plate  42 ). 
     Also with this arrangement of the LEDs  11 , light is emitted in different directions and the light overlaps to form planar light. In addition, as a result of the light from the two opposite LED modules MJx entering the light guide plate  42 , planar light is supplied to the optical sheets  44  to  46  and to the liquid crystal display panel  59 . 
     In Example 19, with a view to permitting humans to perceive the entire planar light to have uniform luminance, among the LEDs  11  in a row in each of the two LED modules MJx, the interval between the LEDs  11  near the center is made shorter than the interval between the LEDs  11  near the periphery. This arrangement, however, is not meant as any limitation. For example, of the two LED modules MJx, one alone may be an LED module MJx having LEDs arranged with a difference in density. 
     With a view to preventing insufficient luminance in a peripheral region of the planar light while retaining the uniformity of the planar light, two LED modules MJx in which the interval between the LEDs  11  near the center is longer than the interval between the LEDs  11  near the periphery may be arranged opposite each other (needless to say, of the two LED modules MJx, one alone may be an LED module MJx having LEDs arranged with a difference in density). 
     Although, in Example 19, LED modules MJx along the X direction are arranged opposite each other, this is not meant to be any limitation; instead, two LED modules MJy along the Y direction may be arranged opposite each other across the light guide plate  42  (i.e., LED modules MJy may be arranged one at each of opposite side edges of the light guide plate  42 ). Needless to say, among the LEDs  11  in a row in each of the two LED modules MJy, the interval between the LEDs  11  near the center may be shorter, or longer, than the interval between the LEDs  11  near the periphery. 
     As shown in  FIG. 25  (Example 20), four LED modules MJ (that is, two LED modules MJx and two LED modules MJy) may be arranged in a loop around the light guide plate  42 . That is, LED modules MJ may be arranged one at each of all—two pairs of mutually opposite—side edges of the light guide plate  42 . 
     The LEDs  11  in the LED modules MJ may be arranged at any intervals. For example, with a view to permitting humans to perceive the entire planar light to have uniform luminance, LED modules MJx and MJy may be arranged in which the intervals between LEDs  11  near the center is shorter than the interval between LEDs  11  near the periphery. For another example, with a view to preventing insufficient luminance in a peripheral region of the planar light, LED modules MJx and MJy may be arranged in which the intervals between LEDs  11  near the center is longer than the interval between LEDs  11  near the periphery. 
     As shown in  FIG. 26  (Example 21), with a view to reliably enhancing the uniformity of the planar light, LEDs  11  may be arranged with different kinds of density between opposite LED modules MJ. 
     Specifically, of the LED modules MJx located opposite each other, in one LED module MJx, the interval between LEDs  11  near the center is shorter than the interval between LEDs  11  near the periphery; in the other LED module MJx, the interval between LEDs  11  near the center is longer than the interval between LEDs  11  near the periphery. Likewise, of the LED modules MJy located opposite each other, in one LED module MJy, the interval between LEDs  11  near the center is shorter than the interval between LEDs  11  near the periphery; in the other LED module MJy, the interval between LEDs  11  near the center is longer than the interval between LEDs  11  near the periphery. 
     Also in a backlight unit  49  (see  FIG. 24 ) in which two LED module MJx are arranged opposite each other, in one LED module MJx, the interval between LEDs  11  near the center may be shorter than the interval between LEDs  11  near the periphery; in the other LED module MJx, the interval between LEDs  11  near the center may be longer than the interval between LEDs  11  near the periphery. 
     Also in a backlight unit  49  in which two LED module MJy are arranged opposite each other, in one LED module MJy, the interval between LEDs  11  near the center may be shorter than the interval between LEDs  11  near the periphery; in the other LED module MJy, the interval between LEDs  11  near the center may be longer than the interval between LEDs  11  near the periphery. 
     Also in a backlight unit  49  (see  FIGS. 22 and 23 ) in which LED modules MJx and MJy are in an intersecting arrangement, in one LED module MJ (MJx or MJy), the interval between LEDs  11  near the center may be shorter than the interval between LEDs  11  near the periphery; in the other LED module MJ (MJy or MJx), the interval between LEDs  11  near the center may be longer than the interval between LEDs  11  near the periphery. 
     That is, irrespective of whether LED modules MJ are arranged in an intersecting, opposite, or loop-forming arrangement, arranging LEDs  11  at irregular pitches in at least one LED module MJ produces an effect commensurate with the arrangement. 
     There is no particular restriction on the number of LEDs  11  included in each LED module MJ. For example, in a case where, as shown in  FIG. 24 , LED modules MJx are arranged opposite each other, the number of LEDs  11  in the LED module MJx in which the interval between LEDs  11  near the center is shorter than the interval between LEDs  11  near the periphery may be greater than the number of LEDs  11  in the LED module MJx in which the interval between LEDs  11  near the center is longer than the interval between LEDs  11  near the periphery. This is because the number of LEDs  11  may be varied as necessary with consideration given to the cost balance of the backlight unit  49 , the balance of electric power consumption, and the balance of the uniformity of the planar light. 
     [Embodiment 5] 
     A fifth embodiment of the invention will now be described. Such members as have similar functions to those used in Examples 1 to 4 are identified by the same reference signs, and no overlapping descriptions will be repeated. 
     In cases where, as in Embodiments 1 to 3, all LEDs  11  in a lattice arrangement emit light in the same direction and the light from them gathers to form planar light, there is provided a single mounting board  12 . This, however, is not meant as any limitation. For example, as shown in  FIG. 27  (Example 22), the backlight unit  49  may incorporate smaller mounting substrates  12   s , as if obtained by dividing the mounting board  12  in Example 2 (see  FIG. 2 ) into two parts, with LEDs  11  in the same lattice arrangement on each of the mounting boards  12   s.    
     With this design, the mounting boards  12   s  have a comparatively small size, and this facilitates the handling of the mounting boards  12   s  in the manufacturing process of the backlight unit  49 . Moreover, the mounting board  12   s  are of the same type, having the same electrode arrangement (and hence the same arrangement of LEDs  11 ), are accordingly easy to mass-produce, and thus help reduce the cost of the mounting board  12   s . Thus, a backlight unit  49  incorporating such mounting boards  12   s  can be manufactured easily and at reduced cost. Moreover, the size of the backlight unit  49  (and hence the size of the liquid crystal display panel  59 ) does not limit the application of the mounting boards  12   s.    
     Although  FIG. 27  shows smaller mounting boards  12   s  as if obtained by dividing the mounting board  12  in Example 2 into two parts, the number of mounting boards  12   s  is not limited to two. For example, four smaller mounting boards  12   s  as if obtained by dividing the mounting board  12  in Example 2 into four parts may be incorporated in the backlight unit  49 . 
     That is, in a backlight unit  49  in which a plurality of mounting boards  12  having LEDs  11  mounted on them are arranged, a desired arrangement of LEDs  11  may be achieved by incorporating a plurality of mounting boards  12  having the same arrangement of LEDs  11 . 
     The mounting boards  12  may be designed as shown in  FIG. 28  (Example 23). Specifically, in Example 2 (see  FIG. 2 ), the backlight unit  49  may incorporate five mounting boards  12  on each of which the interval between the Y-direction rows, which each have LEDs  11  arranged in a row, is equal. 
     More specifically, this backlight unit  49  incorporates one mounting board  12   a  on which the interval between four Y-direction rows is equal, namely Px-a. On both sides of this mounting board  12   a  in the X direction, two mounting boards  12   b  are arranged on which the interval between three Y-direction rows is equal, namely Px-b. Further on the outer sides of these mounting boards  12   b  in the X direction, mounting boards  12   c  are arranged on which the interval between three Y-direction rows is equal, namely Px-c (with the intervals between the individual mounting boards  12   a  to  12   c  set appropriately). 
     That is, in a backlight unit  49  in which a plurality of mounting boards  12  ( 12   a ,  12   b ,  12   b ,  12   c , and  12   c ) having LEDs  11  mounted on them are arranged, while the intervals between LEDs  11  are equal on each mounting board (for example, interval Px-a on the mounting board  12   a ), the intervals between LEDs  11  differ among the mounting boards ( 12   a ,  12   b ,  12   b ,  12   c , and  12   c ). Even though a plurality of mounting boards  12  ( 12   a ,  12   b ,  12   b ,  12   c , and  12   c ) with LEDs  11  arranged at different intervals are incorporated, the LEDs  11  are in a desired arrangement. 
     In this backlight unit  49 , on each single mounting board  12 , the LEDs  11  are arranged at equal intervals. This makes the mounting boards  12  extremely easy to mass-produce, and thus helps reduce the cost of the mounting boards  12 . Moreover, the mounting boards  12  ( 12   a ,  12   b ,  12   b ,  12   c , and  12   c ) have comparatively small sizes, and this facilitates the handling of the mounting boards  12  in the manufacturing process of the backlight unit  49 . Thus, a backlight unit  49  incorporating such mounting boards  12  can be manufactured easily and at reduced cost. Moreover, the size of the backlight unit  49  does not limit the application of the mounting boards  12 . 
     Although the description given above with reference to  FIG. 27  (Example 22) and  FIG. 28  (Example 23) deals with examples in which the LED modules MJ in Example 2 are used, similar designs are possible by use of any other LED modules MJ described in connection with Embodiments 1 to 4. 
     [Other Embodiments] 
     The present invention may be carried out in any manners other than specifically described by way of embodiments above, and allows many modifications and variations. 
     For example, in a case where LEDs  11  are arranged as shown in  FIG. 27 , an imaginary line ILy may be set. The imaginary line ILy lies on the planar center of the planar light, and can divide the plane of the planar light into a plurality of areas. The arrangement of a plurality of LEDs  11  that produce the light in one of the so divided areas and the arrangement of a plurality of LEDs  11  that produce the light in the other of the so divided areas are line-symmetric about the imaginary line ILy. 
     As shown in  FIG. 27 , apart from the imaginary line ILy along the Y direction, an imaginary line ILx along the X direction my be set (this imaginary line ILx also lies on the planar center of the planar light). The arrangement of a plurality of LEDs  11  that produce the planar light in one of the areas so divided by the imaginary line ILx and the arrangement of a plurality of LEDs  11  that produce the planar light in the other of the areas so divided by the imaginary line ILx are line-symmetric about the imaginary line ILx (that is, about the imaginary line ILy, the LEDs  11  are arranged symmetrically between left and right and, about the imaginary line ILx, the LEDs  11  are arranged symmetrically between top and bottom). 
     Also in many arrangements of LEDs  11  other than that shown in  FIG. 27  (for example, those shown in  FIGS. 1 to 6 ,  8  to  13 ,  15 ,  16 ,  22  to  25 , and  28 ), at least one imaginary line IL that lies on the planar center of the planar light and that can divide the planar light into a plurality of parts can be set. Then, the arrangement of a plurality of LEDs  11  that produce one of the so divided parts of the planar light and the arrangement of a plurality of LEDs  11  that produce the other of the so divided parts of the planar light are line-symmetric about the imaginary line IL. 
     With these designs, when the control unit  21  shown in  FIG. 19  controls the LEDs  11  in various ways according to a given algorism, the same sequence of control is repeated, and this alleviates the burden of control. It is also easy to produce the program for the control of the light emission of the LEDs  11 , which affects the luminance distribution of the planar light. 
     The control unit  21 , more specifically the pulse width modulator  26 , may have the function of varying the current value (value of electric current) supplied to the LEDs  11  on an LED  11  by LED  11  basis. That is, the control unit  21  then controls the light emission luminance of the LEDs  11  by increasing and decreasing the current value supplied to the LEDs  11  (i.e., the control unit  21  varies the light emission luminance specific to the LEDs  11  on an LED  11  by LED  11  basis). 
     With a control unit  21  having that function, for example, as shown in  FIG. 29  (Example 24), which shows an arrangement of LEDs  11  similar to that in Example 3, the current value supplied to the LEDs  11  indicated by diagonal-line hatching may be made different from the current value supplied to the other LEDs  11 . 
     In a case where, as described above, the control unit (current controller)  21  varies the current value supplied to the LEDs  11  between LEDs  11  arranged at longer intervals and LEDs  11  arranged at shorter intervals, more specifically, in a case where the current value supplied to LEDs  11  arranged at longer intervals is higher than the current value supplied to LEDs  11  arranged at shorter intervals, the following applies. 
     In the backlight unit  49  of Example 3 in Embodiment 1, with a view to suppressing the number of LEDs  11  but nevertheless permitting humans to perceive the planar light to have uniform luminance, the arrangement of the LEDs  11  is so devised that the luminance near the center of the planar light is higher than the luminance in the region elsewhere than near the center. 
     However, as shown in  FIG. 29 , which shows Example 24, even in an arrangement of LEDs  11  similar to that in  FIG. 3  (Example 3), the control unit  21  controls the current value such that the current value supplied to LEDs  11  arranged at longer intervals (the LEDs  11  hatched with slant lines) is higher than the current value supplied to LEDs  11  arranged at shorter intervals (the LEDs  11  without hatching). This makes the luminance in the region elsewhere than near the planar center close to the luminance near the center of the planar light. 
     Thus, compared with the backlight unit  49  of Example 3, the backlight unit  49  incorporating the LEDs  11  of Example 24, despite a comparatively small number of LEDs  11 , reliably enhances the uniformity of the planar light. 
     For example as shown in  FIG. 30  (Example 25), which shows an arrangement of LEDs  11  similar to that in Example 10, the control unit  21  may vary the current value supplied to the LEDs  11  indicated by diagonal-line hatching from the current value supplied to the other LEDs  11 . 
     Specifically, in the backlight unit  49  of Example 10 in Embodiment 2, with a view to suppressing the number of LEDs  11  but nevertheless preventing insufficient luminance in a peripheral region of the planar light while retaining the uniformity of the planar light, the arrangement of the LEDs  11  (see  FIG. 10 ) is so devised that the luminance in a region elsewhere than near the center of the planar light is higher than the luminance near the center of the planar light. 
     However, as shown in  FIG. 30 , which shows Example 25, even in an arrangement of LEDs  11  similar to that in  FIG. 10  (Example 10), the control unit  21  controls the current value such that the current value supplied to LEDs  11  arranged at longer intervals (the LEDs  11  hatched with slant lines) is higher than the current value supplied to LEDs  11  arranged at shorter intervals (the LEDs  11  without hatching). This makes the luminance near the center of the planar light close to the luminance in the region elsewhere than near the planar center. 
     Thus, compared with the backlight unit  49  of Example 10, the backlight unit  49  incorporating the LEDs  11  of Example 25, despite a comparatively small number of LEDs  11 , reliably enhances the uniformity of the planar light. 
     In Examples 24 and 25, through the control by the control unit  21  of the current supplied to the LEDs  11 , the light emission luminance specific to the LEDs  11  is varied on an LED  11  by LED  11  basis to enhance the uniformity of the planar light. This, however, is not meant as any limitation; the uniformity of the planar light can be enhanced by relying on a difference in light emission efficiency among LEDs  11  (i.e., by use of LEDs  11  that emit light at different luminance when supplied with a given current). That is, the light emission efficiency of LEDs  11  arranged at longer intervals may be higher than the light emission efficiency of LEDs  11  arranged at shorter intervals. 
     For example, in  FIGS. 29 and 30 , the light emission efficiency of LEDs  11  arranged at longer intervals (the LEDs  11  hatched by slant lines) may be higher than the light emission efficiency of LEDs  11  arranged at shorter intervals (the LEDs  11  without hatching). This design permits the use of comparatively inexpensive LEDs  11  with low light emission luminance, and thus helps reduce the cost of the backlight unit  49 . 
     A control unit  21  that varies the luminance distribution of planar light by varying the current value supplied to LEDs  11  as described above can be called a luminance-varying system. Using LEDs  11  with different light emission efficiency as the plurality of LEDs  11  that produce planar light can also be called a luminance-varying system (varying the luminance distribution of planar light encompasses, for example, varying planar light with a non-uniform luminance distribution in such a way as to make it uniform, and varying planar light with a uniform luminance distribution in such a way as to give it a non-uniform luminance distribution to a degree negligible in terms of the characteristics of the human visual sense). 
     Although the above description deals with cases where the control unit  21  supplies electric current to LEDs  11  in an unequal arrangement, this is not meant as any limitation. Even in a backlight unit  49  in which all LEDs  11  are in a lattice arrangement at equal pitches, the control unit  21  can vary the luminance distribution of planar light. 
     For example, in a case where LEDs  11  in an equal arrangement is in a lattice arrangement, within the group of those LED  11  in a lattice arrangement, the current value supplied to LEDs  11  near the center may differ from the current value supplied to LEDs  11  near the periphery. With a backlight unit  49  like this, it is possible both to permit humans to perceive the entire planar light to have uniform luminance and to prevent insufficient luminance in a peripheral region of the planar light while retaining the uniformity of the planar light. 
     Likewise, although the above description deals with examples where LEDs  11  with varying light emission efficiency are in an unequal arrangement, this is not meant as any limitation. Specifically, even in a backlight unit  49  in which LEDs with varying light emission efficiency are in an equal arrangement like a lattice, the luminance distribution of the planar light can be varied. 
     For example, in a case where LEDs  11  in an equal arrangement is in a lattice arrangement, within the group of the LEDs  11  in a lattice arrangement, the light emission efficiency of LEDs  11  near the center may differ from the light emission efficiency of LEDs  11  near the periphery. With a backlight unit  49  like this, it is possible both to permit humans to perceive the entire planar light to have uniform luminance and to prevent insufficient luminance in a peripheral region of the planar light while retaining the uniformity of the planar light. 
     The LEDs  11  in a lattice arrangement do not all have to emit light of the same color (for example, white) (that is, the LEDs  11  do not all need to be white-light-emitting LEDs  11 W). For example, while the light near the periphery of the planar light is produced by white-light-emitting LEDs  11 W, the light near the center of the planar light may be produced by mixing light from red-light-emitting LEDs  11 R, green-light-emitting LEDs  11 G, and blue-light-emitting LEDs  11 B. 
     In one specific example, for example, of the LEDs  11  in Example 15 shown in  FIG. 15 , the four LEDs  11  located within the central divided regions  13 C may be an LED  11 R, LED  11 G, LED  11 G, and LED  11 B, and the one LED  11  located within the peripheral divided regions  13 T may be an LED  11 W. 
     With this design, near the center of the planar light, white light is produced by mixing together light of different colors unlike that near the periphery, and thus is more vividly white than white light emitted singly. This affords vividness in the principal part (near the center of the liquid crystal display panel  59 ) of the image displayed on the liquid crystal display panel  59  which receives such planar light. 
     Although the above description deals with examples where LEDs  11  as light-emitting devices are used as point light sources, this is not meant as any limitation. Instead, for example, light-emitting devices such as laser devices, or light-emitting devices formed of a self-luminous substance, such as organic or inorganic EL (electroluminescence) light-emitting devices, may be used. Instead of light-emitting devices, point light sources such as lamps may be used. 
     The control unit  21  shown in  FIG. 19  may be incorporated in the liquid crystal display panel  59  or in the backlight unit  49 . That is, such members need to be incorporated in the liquid crystal display apparatus  69 . 
     Backlight units  49  as described above are particularly useful in attempting to enhance the quality of the image displayed on the liquid crystal display panel  59  by use of planar light (that is, backlight BL). 
     LIST OF REFERENCE SIGNS 
       11  LED (light-emitting device) 
       12  mounting board 
       12 U mounting surface 
     MJ LED module (light-emitting module) 
       13  divided region 
       13 C central divided region 
       13 T peripheral divided region 
       21  control unit 
       22  video signal processor 
       23  liquid crystal display panel controller 
       24  LED controller 
       25  LED driver controller 
       26  pulse width modulator 
       31  gate driver 
       32  source driver 
       33  LED driver 
       41  backlight chassis 
       42  light guide plate 
       43  reflective sheet 
       44  diffusive sheet 
       45  prism sheet 
       46  prism sheet 
       49  backlight unit (illuminating apparatus) 
       59  liquid crystal display panel (display panel) 
       69  liquid crystal display apparatus (display apparatus) 
     X direction in which LEDs are arranged side by side 
     Y direction in which LEDs are arranged side by side