Patent Publication Number: US-2021190290-A1

Title: Illumination device and exhibition apparatus

Description:
FIELD 
     The present invention relates to an illumination device including a light guide plate and an exhibition apparatus including the illumination device. 
     BACKGROUND 
     Vending machines commonly include illumination devices that illuminate multiple samples of commercial products for easy visibility. For example, illumination units each including a transparent body containing two differently-oriented light-emitting diodes (LEDs) may be installed in multiple upper and lower sample shelves on which product samples are displayed. The samples are illuminated from above and below (refer to, for example, Patent Literature 1). 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2012-22482 
     SUMMARY 
     Technical Problem 
     Although the technique described in Patent Literature 1 can illuminate the product samples from above and below, users of vending machines usually view the product samples from the front. The front of the product samples is thus to be illuminated. Light emitters, such as LEDs, may be installed in front of the product samples for illuminating the samples from the front. In this case, the product samples may be partially hidden by, for example, the light emitters and the substrate on which the light emitters are mounted. 
     One or more aspects of the present invention are directed to an illumination device that can emit light in multiple directions. 
     Solution to Problem 
     One aspect of the present invention provides an illumination device. The illumination device includes a transparent light guide plate having an end face being an incident surface, and a bend located between the incident surface and a distal end face opposite to the incident surface, and a light source facing the incident surface. The light guide plate includes a plurality of first prisms on a first surface of the light guide plate extending from the incident surface to the bend to reflect light emitted from the light source and entering the light guide plate through the incident surface and emit the light through a second surface opposite to the first surface, and a plurality of second prisms on a third surface of the light guide plate extending from the distal end face to the bend to reflect light emitted from the light source and entering the light guide plate through the incident surface and emit the light through a fourth surface opposite to the third surface. 
     The illumination device with the above structure can emit light in multiple directions. 
     In the illumination device, the distal end face of the light guide plate may include a slope facing toward the incident surface. 
     The illumination device with the structure can illuminate an object located near the incident surface with light emitted through the distal end face of the light guide plate in addition to light emitted through the second surface or the fourth surface. 
     In the illumination device, the third surface of the light guide plate may include a surface of the light guide plate curved outward at the bend, and the light guide plate may further include a plurality of third prisms arranged in a predetermined pattern on the fourth surface. The plurality of third prisms may reflect light entering the light guide plate and emit the light through the third surface to display the predetermined pattern. 
     The illumination device with the structure can display a pattern with a glowing appearance, in addition to emitting light in multiple directions. In particular, when the viewer views an illumination target facing the fourth surface from in front of the third surface, the illumination device can display a pattern with a glowing appearance in a manner superimposed on the illumination target. 
     In the illumination device, the light guide plate may have a second incident surface on one of side surfaces of the light guide plate extending from the bend to the distal end face and adjacent to the distal end face. The illumination device may further include a second light source facing the second incident surface. Each of the plurality of third prisms may have a reflection surface facing the second light source to reflect light emitted from the second light source and entering the light guide plate through the second incident surface and emit the light through the third surface. 
     The illumination device with the structure uses different light sources for pattern display and illumination, and can increase the brightness of both the illumination light and the pattern. 
     In the illumination device, the light source may emit light having a color different from a color of light emitted from the second light source. 
     The illumination device with the structure can thus show different light colors between the pattern with a glowing appearance and the illumination. 
     In the illumination device, the third surface of the light guide plate may include a surface of the light guide plate curved inward at the bend, and the plurality of second prisms may be arranged in a predetermined pattern. 
     The illumination device with the structure can display the pattern with light emitted through the fourth emission surface, while illuminating the illumination target with light emitted through the second surface. 
     In the illumination device, the first surface may include a surface of the light guide plate curved inward at the bend. 
     The illumination device with the structure can emit light in different directions. 
     Another aspect of the present invention provides an exhibition apparatus. The exhibition apparatus includes a mount on which an exhibition target is mountable, and an illumination device that illuminates the exhibition target. The illumination device includes a transparent light guide plate having a back end face being an incident surface, a bend between the incident surface and a distal end face opposite to the incident surface, a section from the incident surface to the bend extending from back to front, and a section from the distal end face to the bend located in front of the exhibition target, and a light source facing the incident surface. The light guide plate includes a plurality of first prisms on a first surface of the light guide plate extending from the incident surface to the bend to reflect light emitted from the light source and entering the light guide plate through the incident surface and emit the light through a second surface opposite to the first surface, and a plurality of second prisms on a third surface of the light guide plate not facing the exhibition target and extending from the distal end face to the bend to reflect light emitted from the light source and entering the light guide plate through the incident surface and emit the light through a fourth surface opposite to the third surface. 
     The exhibition apparatus with the above structure can illuminate the exhibition target in multiple directions. The exhibition apparatus can also illuminate the exhibition target from the front without hiding the exhibition target with a part of the illumination device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic perspective view of a vending machine incorporating illumination devices according to one embodiment of the present invention. 
         FIG. 2  is a cross-sectional side view of the vending machine showing a part including display shelves. 
         FIG. 3  is a schematic front view of a light guide plate. 
         FIG. 4  is a schematic bottom view of the light guide plate. 
         FIG. 5  is a schematic cross-sectional side view of the light guide plate taken along a line indicated by arrows AA′ in  FIG. 3 . 
         FIG. 6  is a partial schematic perspective view of a light guide plate according to a modification. 
         FIG. 7  is a schematic cross-sectional side view of the light guide plate according to the modification. 
     
    
    
     DETAILED DESCRIPTION 
     An illumination device according to one or more embodiments of the present invention will now be described with reference to the drawings. The illumination device includes a light guide plate formed from a material transparent to light from a light source. Light from the light source facing an incident surface, which is one of the side surfaces of the light guide plate, enters the light guide plate through the incident surface and propagates within the light guide plate. The light guide plate has a bend at a predetermined distance away from the incident surface. The light guide plate has a section extending from the incident surface to the bend and a section extending from the bend to a distal end face that is an end face opposite to the incident surface. Each section of the light guide plate includes multiple prisms on its surface not facing an illumination target to reflect light from the light source propagating within the light guide and emit the light through the other surface facing the illumination target. The illumination device can thus emit light in multiple directions. In the examples described below, for ease of explanation, the term front refers to a direction toward the viewer and the term back refers to the opposite direction. 
       FIG. 1  is a schematic perspective view of a vending machine incorporating illumination devices according to one embodiment of the present invention. A vending machine  100 , which is an example of an exhibition apparatus, includes a housing  110  and illumination devices  121 . The housing  110  includes three display shelves  111  on the upper half of the front surface, multiple selection buttons  112  located in the lower portion of each display shelf  111 , a money slot  113  in the front surface, and a product outlet  114  and a coin return slot  115  located in the lower portion of the front surface. The illumination devices  121  each extend from the bottom to the front surface of the corresponding display shelf  111 . Each display shelf  111  is an example of a mount on which an exhibition target is mounted. Each display shelf  111  receives product samples  131 . Each product sample  131  is an example of an exhibition target to be displayed in the exhibition apparatus, and also an example of an illumination target to be illuminated by the illumination device  121 . The vending machine  100  also includes, inside the housing  110 , a storage (not shown) that stores the same products as those represented by the product samples  131  mounted on the display shelves  111 , a transporting mechanism (not shown) that transports products from the storage to the product outlet  114 , and a control circuit (not shown) that centrally controls the vending machine  100 . The control circuit is connected to a sensor for recognizing money inserted through the money slot  113 , and controls the transporting mechanism to transport a product from the storage to the product outlet  114  when the amount of inserted money is equal to or greater than the price of the product corresponding to a selection button selected from the selection buttons  112  and pressed by a viewer (a user of the vending machine  100  in this example). When the amount of inserted money is greater than the price of the product corresponding to the pressed selection button, the control circuit returns the difference between the amount of inserted money and the product price to the coin return slot  115 . 
       FIG. 2  is a cross-sectional side view of the vending machine  100  showing a part including the display shelves  111 . The illumination devices  121  have the same structure, and one of the illumination devices will now be described. 
     As shown in  FIG. 2 , each display shelf  111  includes the illumination device  121 . Each illumination device  121  includes a light guide plate  11  and a light source  12 . 
     The light guide plate  11  is transparent to light emitted from the light source  12 . The light guide plate  11  is a molded plate formed from a resin transparent to visible light, such as polymethyl methacrylate (PMMA), polycarbonate, or a cyclic olefin polymer. The light guide plate  11  extends along and substantially parallel to the bottom surface of the display shelf  111  from the back to the front of the display shelf  111 . The light guide plate  11  has an upward, substantially right angle bend near the front of the display shelf  111 . The light guide plate  11  extends substantially parallel to the front surface of the housing  110  in front of the product samples  131  mounted on the display shelf  111 . The light guide plate  11  has a back end face serving as an incident surface. Light emitted from the light source  12  facing the incident surface enters the light guide plate  11  through the incident surface and propagates within the light guide plate  11  while being totally internally reflected between the surfaces. The light guide plate  11  includes multiple prisms on each surface not facing the product samples  131 . As indicated by arrows  201  to  203 , light propagating within the light guide plate  11  is emitted toward the product samples  131  as reflected by each prism or through the distal end face of the light guide plate  11 , which is the end face opposite to the incident surface. The illumination device  121  can thus illuminate the product samples  131  in multiple directions. The light guide plate  11  will be described in detail later. 
     The light source  12  includes multiple light emitters that emit visible light. The light emitters each have a light-emitting surface facing the incident surface of the light guide plate  11 , and are arranged in a row in the longitudinal direction of the incident surface. The light emitters in the light source  12  are turned on or off in response to a control signal from the control circuit (not shown) in the vending machine  100 . While the light source  12  is on as controlled by the control circuit, light emitted from the light source  12  enters the light guide plate  11  through the incident surface. 
     The light emitters in the light source  12  are, for example, light-emitting diodes, incandescent lamps, or fluorescent lamps. The light emitted from the light emitters in the light source  12  may be white light, or may be light with a specific color such as red, blue, or yellow. 
     The light guide plate  11  will now be described in detail. 
       FIG. 3  is a schematic front view of the light guide plate  11 .  FIG. 4  is a schematic bottom view of the light guide plate  11 .  FIG. 5  is a schematic cross-sectional side view of the light guide plate  11  taken along a line indicated by arrows AA′ in  FIG. 3 . As shown in  FIGS. 4 and 5 , the back end surface of a section of the light guide plate  11  extending along the bottom surface of the display shelf  111  serves as an incident surface  11   a  facing the light source  12 . The light guide plate  11  has an upward bend  11   c . In the present embodiment, the incident surface  11   a  and the bend  11   c  are substantially parallel to each other in their longitudinal directions. In some embodiments, the incident surface  11   a  and the bend  11   c  are not substantially parallel to each other in their longitudinal directions. For example, the light guide plate  11  may have the incident surface  11   a  at a greater distance to the bend  11   c  toward the left as viewed from the front. The light guide plate  11  includes multiple prisms  13  on the upper surface of its section extending from the incident surface  11   a  to the upward bend  11   c , or more specifically, on a first diffusion surface  11   d  not facing the product samples  131  mounted on the lower display shelf  111 . The light guide plate  11  also includes multiple prisms  14  on the front surface of its section extending from the bend  11   c  to a distal end face  11   b , which is the surface not facing the product samples  131  mounted on the display shelf  111  located above the section from the incident surface  11   a  to the bend  11   c , or more specifically, a second diffusion surface  11   e  including a surface of the light guide plate  11  curved outward at the bend  11   c . The prisms  13  may be arranged on the entire first diffusion surface  11   d , or may be arranged in a part of the first diffusion surface  11   d . Similarly, the prisms  14  may be arranged on the entire second diffusion surface  11   e , or may be arranged in a part of the second diffusion surface  11   e . The positions and the areas where the prisms  13  and the prisms  14  are located may be determined in accordance with the position of the illumination device  121  with respect to the illumination target (product samples  131  in this example). 
     The bend  11   c  of the light guide plate  11  is chamfered at 45° with the second diffusion surface  11   e  and a first emission surface  11   f , which is opposite to the first diffusion surface  11   d  and faces the product samples  131  on the lower display shelf  111 . Near the chamfered bend  11   c , light propagating within the light guide plate  11  bounces off each surface of the light guide plate  11  at smaller angles, thus reducing the likelihood that the light propagating within the light guide plate  11  leaks outside the light guide plate  11  at the bend  11   c . Instead of being chamfered, the bend  11   c  may be outwardly rounded on the lower, front surface continuous with the first emission surface  11   f  and the second diffusion surface  11   e . Near the rounded bend  11   c , light propagating within the light guide plate  11  bounces off each surface of the light guide plate  11  at even smaller angles, thus further reducing the likelihood that the light propagating within the light guide plate  11  leaks outside the light guide plate  11  at the bend  11   c . The upper, back surface at the bend  11   c  continuous with the first diffusion surface  11   d  may also be chamfered or rounded inwardly. 
     The distal end face  11   b  of the light guide plate  11  opposite to the incident surface  11   a  may have smaller heights in a part nearer the back surface than in a part nearer the front surface. The distal end face  11   b  may thus be a slope facing toward the incident surface  11   a  or backward. The slope allows more light to be emitted through the distal end face  11   b  toward the product samples  131  after propagating within the light guide plate  11  and reaching the distal end face  11   b.    
     Light from the light source  12  enters the light guide plate  11  through the incident surface  11   a . A part of the light from the light source  12  propagating within the light guide plate  11  by total internal reflection is first totally internally reflected at the prisms  13  on the first diffusion surface  11   d  located on the upper surface of the section of the light guide plate  11  extending from the incident surface  11   a  to the bend  11   c , and then emitted through the first emission surface  11   f , which is opposite to the first diffusion surface  11   d  and faces the product samples  131  on the lower display shelf  111 . The emitted light illuminates the product samples  131  mounted on the lower display shelf  111  from above. 
     Another part of the light from the light source  12  entering the light guide plate  11  through the incident surface  11   a  passes through the bend  11   c  while being totally internally reflected within the light guide plate  11  and reaches the section extending between the bend  11   c  and the distal end face  11   b . The light reaching the section between the bend  11   c  and the distal end face  11   b  is first totally internally reflected at the prisms  14  on the second diffusion surface  11   e  located on the front surface of the light guide plate  11 , and then emitted through a second emission surface  11   g , which is opposite to the second diffusion surface  11   e  and faces the product samples  131  mounted on the display shelf  111  located above the section extending from the incident surface  11   a  to the bend  11   c . The emitted light illuminates the product samples  131  mounted on the display shelf  111  from the front. 
     At least a part of the light reaching the distal end face  11   b  without emitted through the light guide plate  11  is emitted through the distal end face  11   b . A part of the light emitted through the distal end face  11   b  illuminates, from the front, the product samples  131  on the display shelf  111  located above the section extending from the incident surface  11   a  to the bend  11   c . The light emitted through the distal end face  11   b  illuminates a higher area than the light emitted through the second emission surface  11   g.    
     Each prism  13  is, for example, a substantially triangular groove having a predetermined length on the first diffusion surface  11   d . The predetermined length is, for example, about several tens to several hundreds of micrometers. Each prism  13  has a reflection surface  13   a  at a predetermined angle (hereafter, slope angle) with the first diffusion surface  11   d . The reflection surface  13   a  provides total internal reflection of the light from the light source  12  entering the light guide plate  11  to emit the light through the first emission surface  11   f.    
     Each prism  13  has the reflection surface  13   a  facing toward the light source  12 . More specifically, the reflection surface  13   a  is substantially parallel to the longitudinal direction of the incident surface  11   a  on a plane parallel to the first diffusion surface  11   d . In some embodiments, to illuminate the product samples  131  located below the first emission surface  11   f  in different directions, the angle between the direction in which the reflection surface  13   a  of each prism  13  directly faces and the normal to the incident surface  11   a  may be set randomly for each prism  13 . 
     The prisms  13  are arranged on the first diffusion surface  11   d  in a staggered manner, latticed, or randomly at a uniform density. To vary the brightness of the illumination depending on the position, the prisms  13  at different positions may be arranged at different densities on the first diffusion surface  11   d , or more specifically, may be more densely arranged in brighter areas. For example, the product samples  131  may be illuminated at the front rather than at the back. The prisms  13  may thus be arranged more densely nearer the bend  11   c.    
     Similarly, each prism  14  is, for example, a substantially triangular groove having a predetermined length on the second diffusion surface  11   e . The predetermined length is, for example, about several tens to several hundreds of micrometers. Each prism  14  has a reflection surface  14   a  at a predetermined slope angle with the second diffusion surface  11   e . The reflection surface  14   a  provides total internal reflection of light from the light source  12  entering the light guide plate  11  to emit the light through the second emission surface  11   g.    
     Each prism  14  has the reflection surface  14   a  substantially parallel to the longitudinal direction of the bend  11   c  on a plane parallel to the second diffusion surface  11   e . In some embodiments, to illuminate the product samples  131  located behind the second emission surface  11   g  in different directions, the angle between the direction in which the reflection surface  14   a  of each prism  14  directly faces and the vertically downward direction from the reflection surface  14   a  may be set randomly for each prism  14 . 
     The prisms  14  are arranged on the second diffusion surface  11   e  in a staggered manner, latticed, or randomly at a uniform density. To vary the brightness of the illumination depending on the position, the prisms  14  at different positions may be arranged at different densities on the second diffusion surface  11   e , or more specifically, may be more densely arranged in brighter areas. For example, to illuminate the top of the product samples  131  more intensely than the bottom, the prisms  14  may be arranged more densely nearer the distal end face  11   b . The density of the prisms  13  on the first diffusion surface  11   d  and the density of the prisms  14  on the second diffusion surface  11   e  are adjusted in accordance with the ratio between the amount of light emitted through the first emission surface  11   f  and that emitted through the second emission surface  11   g . For example, to have more light emitted through the second emission surface  11   g  than through the first emission surface  11   f , the prisms  14  on the second diffusion surface  11   e  are arranged more densely than the prisms  13  on the first diffusion surface  11   d.    
     In  FIGS. 4 and 5 , the sizes of the prisms  13  and  14  and the thickness of the light guide plate  11  and other dimensions are exaggerated for ease of viewing. 
     In the illumination device described above, the light guide plate has the bend in the middle, the section extending from the incident surface to the bend, and the section extending from the bend to the distal end face. The light guide plate includes multiple prisms on each section to reflect light propagating within the light guide plate toward the illumination target. The illumination device can thus emit light in various directions. In particular, the illumination device can illuminate the illumination target from the front with the section extending from the bend to the distal end face located in front of the illumination target. The illumination device using the transparent light guide plate does not hide the illumination target from the viewer viewing the illumination target from the front. 
     In one modification, a light guide plate may display a pattern that appears to be glowing frontward, and include multiple prisms arranged in the pattern. 
       FIG. 6  is a partial schematic perspective view of a light guide plate according to the modification.  FIG. 7  is a schematic cross-sectional side view of the light guide plate according to the modification. The modification differs from the above embodiment in that the second emission surface  11   g  of the light guide plate  11  includes multiple prisms arranged in a pattern to be displayed. The difference will now be described. 
     In the modification, the light guide plate  11  displays a pattern  21  that appears to be glowing when viewed from the front. The second emission surface  11   g  has multiple prisms  15  arranged in the pattern  21 . A part of the light from the light source  12  propagating within the light guide plate  11  by total internal reflection is first totally internally reflected by the prisms  15 , and then emitted frontward through the second diffusion surface  11   e . The viewer can thus visually recognize, together with the product samples  131 , the pattern  21  that appears to be glowing in front of the product samples  131  on the second diffusion surface  11   e  of the light guide plate  11  while the light source  12  is on. 
     The prisms  15  are arranged along the pattern  21  in a staggered manner, latticed, or randomly at a uniform density. To provide bright and dark sections in the pattern  21 , the prisms  15  at different positions within the pattern  21  may be arranged at different densities, or more specifically, may be more densely arranged in the brighter section in the pattern  21 . 
     Similarly to the prisms  13  and  14 , each prism  15  is, for example, a substantially triangular groove having a predetermined length on the second emission surface  11   g . The predetermined length is set to allow the pattern  21  to include the multiple prisms  15  and is set to, for example, about several tens to several hundreds of micrometers. Each prism  15  has a reflection surface  15   a  at a predetermined slope angle with the second emission surface  11   g . The reflection surface  15   a  provides total internal reflection of light from the light source  12  propagating within the light guide plate  11  to emit the light through the second diffusion surface  11   e . In one example, each prism  15  has the reflection surface  15   a  facing vertically downward. In another example, to have the pattern  21  viewable in various directions, the angle between the direction in which the reflection surface  15   a  directly faces and the vertically downward direction from the reflection surface  15   a  may be set randomly for each prism  15 . 
     The density of the prisms  14  on the second diffusion surface  11   e  and the density of the prisms  15  on the second emission surface  11   g  are adjusted in accordance with the ratio between the amount of light emitted through the second emission surface  11   g  and that emitted through the second diffusion surface  11   e  for displaying the pattern  21 . For example, to have more light emitted through the second diffusion surface  11   e  than through the second emission surface  11   g , the prisms  15  on the second emission surface  11   g  are arranged more densely than the prisms  14  on the second diffusion surface  11   e . For easy viewing of the pattern  21 , no prism  14  may be arranged in an area on the second diffusion surface  11   e  overlapping the pattern  21  when the light guide plate  11  is viewed from the front. 
     The illumination device according to the modification displays a pattern that appears glowing to the viewer while emitting light in various directions with a single light source. In particular, in front of the illumination target, the illumination device can emit light for illuminating the target from one surface of the light guide plate and can display a pattern that appears glowing to the viewer on the other surface of the light guide plate. The illumination device can thus illuminate the illumination target while displaying a pattern superimposed on the target. 
     In the modification, the pattern  21  may use a light source different from the light source  12  for illumination. For example, one of the side surfaces of the section of the light guide plate  11  from the bend  11   c  to the distal end face  11   b  may serve as a second incident surface, and a second light source  16  may be located to face the second incident surface. The second light source  16  may include multiple light emitters arranged in a row in the longitudinal direction of the second incident surface. Similarly to the light emitters in the light source  12 , the light emitters in the second light source  16  are, for example, light-emitting diodes, incandescent lamps, or fluorescent lamps. 
     In this modification, the light emitted from the second light source  16  and entering the light guide plate  11  through the second incident surface propagates in a direction different from the direction in which the light emitted from the first light source  12  and entering the light guide plate  11  propagates. In this case, the prisms  15  may be arranged to have the reflection surfaces  15   a  facing the second light source  16 . The prisms  15  can thus direct the light emitted from the second light source  16  and entering the light guide plate  11  frontward, or more specifically, can emit light toward the viewer through the second diffusion surface  11   e.    
     In this modification, the light source used for the pattern to appear glowing is separate from the light source for illumination. The illumination device can thus increase both the amount of light for illumination emitted through the second emission surface  11   g  and the amount of light for pattern display emitted through the second diffusion surface  11   e.    
     The light emitters in the light source  12  may emit light having the same or a different color as or from the light emitted from the light emitters in the second light source  16 . When the light emitters in the light source  12  emits light having a different color from the light emitted from the light emitters in the second light source  16 , the illumination device may show, to the viewer, a pattern having a different color from the illumination light superimposed on the illumination target. 
     In the modification, the prisms  14  may be eliminated. In this case, no light is emitted toward the product samples  131  through the second emission surface  11   g . The area behind the pattern is thus darker to allow the viewer to visually recognize the pattern easily. In this case as well, the illumination device can illuminate the lower product samples  131  with light emitted through the first emission surface  11   f , while displaying the pattern viewable from the front. 
     In another modification, a collimator lens may be located between the incident surface  11   a  of the light guide plate  11  and the light source  12  to collimate light emitted from the light source  12 . In this case, the light emitted from the light source  12  and collimated through the collimator lens propagates within the light guide plate  11  without greatly spreading in the longitudinal direction of the incident surface  11   a . Each prism  13  may have the reflection surface  13   a  substantially parallel to the longitudinal direction of the incident surface  11   a  on the plane parallel to the first diffusion surface  11   d . Similarly, each prism  14  is arranged to have the reflection surface  14   a  substantially parallel to the first diffusion surface  11   d  on the plane parallel to the second diffusion surface  11   e.    
     In another modification, the light guide plate  11  may have a downward bend, in place of the upward bend  11   c . In this modification, the illumination device  121  can illuminate the product samples  131  on the lower display shelf  111  from the front and the above. In another modification, the first diffusion surface  11   d  and the first emission surface  11   f  may be exchanged with each other. More specifically, the light guide plate  11  may have the lower surface being the first diffusion surface  11   d  on which the first prisms  13  are located, and the upper surface being the first emission surface  11   f . In this modification, the illumination device  121  can illuminate the product samples  131  from the front and the bottom when the display shelves  111  are formed from a transparent material. 
     In another modification, a flat light guide plate may be used. In this modification, the light guide plate may be, for example, placed substantially parallel to the front face of the housing  110  and in front of the display shelves  111  and the product samples  131 . For example, the lower end face of the light guide plate serves as an incident surface, and a light source may be located to face the incident surface. In the same manner as the prisms on the second diffusion surface in the embodiment and the modifications described above, multiple prisms may be arranged on the surface of the light guide plate not facing the product samples to emit light from the light source propagating within the light guide plate toward the product samples through the surface facing the produce samples. In the same manner as the prisms on the second emission surface in the modifications described above, another set of multiple prisms may be arranged in a display pattern to emit light from the light source propagating within the light guide plate toward the viewer through the surface not facing the product samples on the surface facing the product samples. The illumination device according to this modification can also display the pattern that appears glowing to the viewer while illuminating the product samples with a single light source. 
     As described above, those skilled in the art can make various changes in accordance with embodiments implemented within the scope of the present invention.