WO2001004605A1

WO2001004605A1 - Clear pedestal for an inspection apparatus

Info

Publication number: WO2001004605A1
Application number: PCT/US2000/018879
Authority: WO
Inventors: Mark Shires
Original assignee: Systemation Engineered Products, Inc.
Priority date: 1999-07-12
Filing date: 2000-07-11
Publication date: 2001-01-18
Also published as: AU6343600A

Abstract

An apparatus for inspecting an object of manufacture. The apparatus includes a pedestal made from a material. The pedestal has a generally horizontal top surface for supporting thereon the object to be inspected.

Description

CLEAR PEDESTAL FOR AN INSPECTION APPARATUS

BACKGROUND OF THE INVENTION

The invention relates to an apparatus for inspecting objects during a manufacturing process, and particularly, to a pedestal for supporting the object during inspection.

Electronic semiconductor devices and other objects of manufacture are often visually inspected by a machine as a form of quality control. In the case of electronic components and semiconductor devices, it is particularly important that the leads of the devices be accurately measured and located in three-dimensional space to ensure that proper electrical contact is made when the device is soldered to a printed circuit board. Camera-based inspection systems require stereo views of a lead to determine the three-dimensional location of the lead. Moreover, the object of the inspection must be appropriately backlit in order to silhouette the device. Silhouetting the device ensures accurate measurement of the leads.

During the inspection process, the object of the inspection is placed on a pedestal where it rests while being inspected. Known pedestals are made of a light diffusing material, such as white plastic. The white plastic pedestal is backlit so that the light diffuses through the pedestal in all directions.

SUMMARY OF THE INVENTION

There are disadvantages attendant to the use of a diffusing material such as white plastic as the pedestal in such an inspection device. First, the light passing through the pedestal is not collimated, but rather diffuses in all directions. Moreover, the brightness of the light in all directions is typically the same, is not controllable, and does not allow focusing of the light on the features of interest of the object under inspection. Third, semiconductor devices have different types of leads. In particular, "J" leaded devices are difficult to measure because the leads always have some front lighting due to the geometry of the leads. As a result, different pedestals are required for "J" leaded devices than for "gull wing" devices of the same size.

Accordingly, the invention provides an optically clear supporting pedestal, or stage, upon which the object under inspection rests as the image of the object is being acquired. The clear pedestal allows transmission of the backlight through the pedestal from precisely defined locations. As a result, the light passing through the clear pedestal is collimated and the light intensity can be independently controlled. Thus the angles at which light exits the pedestal can be precisely defined by the geometry of the pedestal.

The invention further provides an apparatus for inspecting an object, the apparatus including a pedestal made from a clear transparent material. The pedestal has a generally horizontal top surface for supporting thereon the object to be inspected. The pedestal also includes a generally vertical side surface, and an angled surface portion extending between the top surface and the side surface. In one embodiment of the invention, the angled surface portion extends from the side surface to the top surface at an angle of approximately 35° from horizontal.

A principal advantage of the invention is the provision of a pedestal that collimates the light passing through the pedestal to produce more accurate measurements of the object under inspection.

It is another advantage of the invention to provide an apparatus for inspecting an object wherein the light intensity passing through the pedestal can be controlled for different directions of light. In this way, inefficiencies of the optical elements, such as mirrors and prisms that are less than 100 percent efficient, can be compensated for. For example, mirrors and prisms that are not optically perfect can be used and compensated for by using a brighter light source.

It is yet another advantage of the invention to provide an apparatus for inspecting an object wherein the apparatus allows for more effective imaging of "J" leaded devices and wherein both "J" leaded devices and "gull wing" devices can be inspected using the same pedestal.

Other features and advantages of the invention are set forth in the following drawings, detailed description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a perspective view showing the inspecting station of the semiconductor inspection apparatus. Figure 2 is a cutaway perspective view of a semiconductor device on the pedestal within the inspection ring.

Figure 3 is a cross-sectional view of the semiconductor inspection apparatus taken along line 3-3 in Fig. 1, including one example of the paths light can take through a pedestal, and additionally showing a camera lens for viewing the device.

Figure 4 is a cross-sectional view of the semiconductor inspection apparatus taken along line 4-4 in Fig. 1.

Figure 5 is a view taken along line 5-5 in Fig. 3. Figure 6 is a view taken along line 6-6 in Fig. 3.

Figure 7 is a schematic cross-sectional view showing another example of the paths light can take through a pedestal.

Figure 8 is a schematic cross-sectional view showing another example of the paths light can take through an elongated pedestal with a central aperture. Figure 9 is a schematic cross-sectional view showing another example of the paths light can take through an elongated pedestal.

Figure 10 is a perspective view of a semiconductor device on another example of an elongated pedestal.

Figure 11 is a perspective view of a semiconductor device on another example of an elongated pedestal.

Figure 12 is a perspective view of a semiconductor device on another example of an elongated pedestal.

Figure 13 is a cross-section view of the pedestal shown in Figure 11 within another example of an inspection ring. Figure 14 is a cross-sectional perspective view of another example of an inspection ring similar to that of Fig. 2, but with cutouts to accommodate side lights.

Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including" and "comprising" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The use of "consisting of and variations thereof herein is meant to encompass only the items listed thereafter. The use of letters to identify steps of a method or process is simply for identification and is not meant to indicate that the steps should be performed in a particular order.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Figure 1 illustrates the inspecting station of a semiconductor inspection apparatus. The station includes a base and four sidewalls extending upward from the base to form a rectangular enclosure. The base is fastened to the sidewalls and the sidewalls are fastened to each other using bolts or any other known fastening methods including screws and glue. A generally rectangular collar tops the sidewalls. Control and power cables run through an aperture in the sidewall of the station. An inspection hardware unit and a front light source are located within the collar of the station.

Key components of the inspection hardware unit, as illustrated in Figures 1 and 2, include an inspection ring, a pedestal, and mirrors. The inspection ring is generally rectangular in cross-section when viewed from above and includes an aperture with a generally rectangular cross-section when viewed from above. Each aperture sidewall includes an angled surface extending between the inspection ring top surface and an aperture sidewall. An inspection ring lip is formed at the lower end of each aperture sidewall. The pedestal, which is described in more detail below, is mounted within the aperture of the inspection ring and rests on the inspection ring lip. Mirrors are mounted on each angled surface of the inspection ring.

The pedestal is substantially rectangular in cross-section when viewed from above and includes a generally horizontal top surface, generally vertical side surfaces, a generally horizontal bottom surface, and angled surface portions. These angled surface portions are preferably at approximately 35 degrees from horizontal, but may be angled at other angles depending on the overall geometry of the pedestal and the object to be inspected. The pedestal is made from a transparent material, such as glass, plastic, etc.

The front light source includes a plurality of individual front lights that are preferably light emitting diodes but may also be any other appropriate lights known in the art.

The interior structure of the inspecting station is further illustrated in Figures 3 and 4. Power and control cables supply a back light source including a plurality of individual back lights that are preferably light emitting diodes but may also be any other appropriate lights known in the art. The individual back lights are mounted on a back light source shelf in a rectangular pattern along the periphery of the back light source shelf as illustrated in Figure 6. The back light source shelf is mounted to the sidewalls within the rectangular enclosure elevationally between the base and the collar. In other embodiments, the back light source may be one or more incandescent, fluorescent, or other lights. A diffuser plate is mounted to the sidewalls within the rectangular enclosure elevationally above the back light source shelf. An inspection hardware support plate is mounted to the tops of the sidewalls using fasteners such as bolts. The inspection hardware support plate includes a central aperture sized slightly smaller than the horizontal dimensions of the pedestal. A front light support ring is anchored to the upper face of the inspection hardware support ring using fasteners such as bolts. Front light mounting plates are anchored to the outer face of the front light support ring using fasteners such as bolts. A plurality of front lights is mounted on the front light mounting plates. The inspection hardware unit as shown in Figure 2 is anchored to the inspection hardware support plate, interior to the front light support ring, by the use of fasteners such as bolts between the inspection hardware support plate and the inspection ring. The collar encloses the inspection hardware unit and front light source and is anchored to the inspection hardware support plate. The collar is formed with an aperture of roughly the same dimensions as the horizontal outside dimensions of the inspection ring.

The general purpose of the inspection station is to light the pins of a semiconductor such that the pins may be inspected. The clear pedestal allows such an inspection to be closely controlled because the clear pedestal allows transmission of light through the pedestal in precisely the same path in which it entered. Thus, the path of any particular light will be known by its source in a precisely defined location. As a result, light passing through the clear pedestal is collimated. This is in contrast to light that diffuses as it travels through a pedestal that is not clear. Choosing the number, type, and placement of light sources can independently control the light intensity that is transmitted to a given location. The geometry of the pedestal and the placement of the light sources can precisely define the angles at which light exits the pedestal. Precision in the control of light intensity and geometry produces more accurate measurements of the object under inspection. Examples of controlling light intensity and geometry are described below.

This precision in the control of light intensity and geometry allows compensation for inefficiencies of the optical elements, such as mirrors and prisms that are less than 100 percent efficient. For example, mirrors and prisms that are not optically perfect can be used and compensated for by using a brighter light source.

The control inherent in the inspecting station of a semiconductor inspection apparatus allows for more effective imaging of " J" leaded devices and wherein both "J" leaded devices and "gull wing" devices can be inspected using the same pedestal.

In operation of the inspection station, a semiconductor device of roughly the same horizontal dimensions as the top surface of the pedestal is placed on the pedestal such that the pins of the semiconductor extend beyond the top surface of the pedestal, thus overhanging the angled surface portions of the pedestal. Figure 2 shows a semiconductor to be inspected resting on the top surface of the pedestal with the semiconductor pins overhanging the angled surface portions of the pedestal.

Once the semiconductor is properly positioned, backlight, as represented by arrows in Figure 3, is emitted by the back light source and passes through the diffuser plate where it is diffused so that the backlight is uniform. The backlight then passes through the central aperture of the inspection hardware support plate and enters the pedestal through the bottom surface of the pedestal. As described above, backlight travels through the pedestal and exits the pedestal in the same path it entered the pedestal.

A portion of the light exits the pedestal through the angle surface portions and bypasses the pins of the semiconductor, thus backlighting the pins and sending a silhouetted image of the pins to a camera or other imaging device. The light might pass directly to the camera, or it may be reflected to the camera off the mirrors.

Light is also emitted by the front light source and illuminates the pins of the semiconductor. The frontlight then reflects off of the mirrors to the pins and back to the camera or other imaging device.

Figures 7-12 illustrate in schematic form other embodiments of the invention including various light patterns available in these embodiments of the invention. These embodiments employ white diffuser plates, black shield plates, alternative light source locations, varying number of light sources, and mirrored surfaces in different combinations to produce varying images of semiconductor pins. These variables may be altered to control the direction and intensity of light reaching the pins to be examined. These embodiments are merely exemplary and are not inclusive of the range of combinations possible.

In the embodiment shown in Figure 7, translucent white diffuser plates are mounted to the pedestal adjacent the side surfaces and bottom surfaces of the pedestal. Additionally, the front light source is removed and a side light source is installed such that the side light source is adjacent to the side surfaces of the pedestal, outside of the white diffuser plates.

The light from both light sources that passes through the diffuser plates and into the pedestal is diffused rather than collimated. Light from the back light source passes through the diffuser plate and pedestal, illuminating the pins of the semiconductor and sending a silhouetted image of the pins to the camera or other imaging device. Concurrently, light from the side light source passes through the diffuser plate and the pedestal and illuminates the same pins. The silhouetted image produced by this light, however, reflects off of a mirror before reaching the camera, thus producing an image of the pins offset from the first image produced by the back light source.

In the embodiment shown in Figure 8, an elongated pedestal with a central aperture takes the place of the previously-described pedestal. The central aperture is formed vertically through the center of the elongated pedestal, leaving a pedestal internal surface. The central aperture is sized to allow for the introduction of a vacuum nozzle within the elongated pedestal to secure the object under inspection in place. Opaque black shields are mounted adjacent the side surfaces of the elongated pedestal, and translucent white diffuser plates are mounted adjacent the side surfaces and bottom surfaces of the elongated pedestal. A back light source is mounted below the elongated pedestal, and side light sources are mounted adjacent the sides of the elongated pedestal.

This embodiment produces an offset image of the semiconductor pins. Light from the back light source passes through the diffuser plate mounted adjacent the bottom surface of the elongated pedestal and through the pedestal. This light reflects off of the pedestal internal surface within the pedestal, and illuminates the pins of the semiconductor, sending a silhouetted image of the pins to the camera or other imaging device. Opaque black shields are mounted adjacent the first portion of the pedestal side surface to prevent extraneous light from entering the pedestal. As in the previous embodiment, light from a light source located adjacent the side surface of the pedestal concurrently passes through the diffuser plate mounted adjacent the second portion of the pedestal side surface and through the pedestal, including crossing the pedestal aperture, and illuminates the same pins. The silhouetted image produced by this light reflects off of a mirror before reaching the camera, thus producing an image of the pins offset from the first image produced by the back light source.

In the embodiment shown in Figure 9, an elongated solid pedestal takes the place of the previously-described pedestal. The bottom surface of the pedestal is internally mirrored to reflect light within the pedestal. Translucent white diffuser plates are mounted to the pedestal adjacent the pedestal side surfaces. Opaque black shields are also mounted to the pedestal adjacent the pedestal side surfaces. A lower side light source and an upper side light source are mounted adjacent the sides of the elongated pedestal. The pedestal angle surface portions, the mirrors, the semiconductor, the semiconductor pins, and the camera or other imaging device are as previously described.

Light emitted from the lower side light sources and the upper side light sources passes through the diffuser plates. As in the previous embodiments, light from the lower side light sources passes through the diffuser plates and pedestal, illuminating the pins of the semiconductor and sending a silhouetted image of the pins to the camera or other imaging device. Concurrently, light from the upper side light sources passes through the diffuser plates and the pedestal and illuminates the same pins. The silhouetted image produced by this light, however, reflects off of the mirror before reaching the camera, thus producing an image of the pins offset from the first image produced by the back light source.

In the embodiment shown in Figure 10, an elongated and tapered solid pedestal is employed. The bottom surface of the pedestal is covered by a diffuser block of translucent white material. Opaque black shields are mounted to the pedestal adjacent the pedestal side surfaces to keep extraneous light out of the pedestal. Translucent white diffuser plates are also mounted to the pedestal adjacent the pedestal side surfaces. The pedestal top surface in this embodiment is divided into two sections. Centered on the top surface is a frustoconical raised portion. A flat surface of the raised portion is thus circular with its diameter approximately equal in measurement to that of a side of a semiconductor to be inspected. The remainder of the pedestal top surface not covered by the raised portion is covered by a black shield. The pedestal in this embodiment does not have angled surface portions. A side light source is mounted adjacent the sides of the elongated pedestal. The mirrors, the semiconductor, the semiconductor pins, and the camera or other imaging device are as previously described.

Light emitted from the side light sources passes through the diffuser plates, and light emitted from the back light sources passes through the diffuser block. As in the previous embodiments, light from the back light sources passes through the diffuser block and pedestal, illuminating the pins of the semiconductor and sending a silhouetted image of the pins to the camera or other imaging device. Concurrently, light from the side light sources passes through the diffuser plates and the pedestal and illuminates the same pins. The silhouetted image produced by this light, however, reflects off of the mirror before reaching the camera, thus producing an image of the pins offset from the first image produced by the back light source.

In the embodiment shown in Figures 11 and 13, an elongated and tapered solid pedestal is employed. The bottom surface of the pedestal is covered by a diffuser block of translucent white material. The area of the bottom surface illustrated in Figure 11 is larger than the area of the bottom surface illustrated in Figure 10 to gather more light to allow inspection of larger semiconductors. Opaque black shields are mounted to the pedestal adjacent the pedestal side surfaces to keep extraneous light out of the pedestal. Translucent white diffuser plates are also mounted to the pedestal adjacent the pedestal side surfaces. The pedestal top surface in this embodiment is divided into two sections. Centered on the top surface is a frustoconical raised portion. A flat surface of the raised portion is thus circular with its diameter approximately equal in measurement to that of a side of a semiconductor to be inspected. The diameter of the raised portion illustrated in Figure 11 is larger than the diameter of the raised portion illustrated in Figure 10 to allow inspection of larger semiconductors. The remainder of the pedestal top surface not covered by the raised portion is covered by a black shield. The pedestal in this embodiment does not have angled surface portions. A side light source is mounted adjacent the sides of the elongated pedestal. The mirrors, the semiconductor, the semiconductor pins, and the camera or other imaging device are as previously described. Figure 13 illustrates the tapered pedestal in cross-section to show the relations of the various components. The pedestals shown in Figures 10 and 12 are of a similar construction to that shown in Figure 13.

Light emitted from the side light sources passes through the diffuser plates, and light emitted from the back light sources passes through the diffuser block. As in the previous embodiments, light from the back light sources passes through the diffuser block and pedestal, illuminating the pins of the semiconductor and sending a silhouetted image of the pins to the camera or other imaging device.

Concurrently, light from the side light sources passes through the diffuser plates and the pedestal and illuminates the same pins. The silhouetted image produced by this light, however, reflects off of the mirror before reaching the camera, thus producing an image of the pins offset from the first image produced by the back light source.

In the embodiment shown in Figure 12, an elongated and tapered solid pedestal is employed. The bottom surface of the pedestal is covered by a diffuser block of translucent white material. The area of the bottom surface illustrated in

Figure 12 is larger than the area of the bottom surface illustrated in Figure 11 to gather more light. This allows inspection of larger semiconductors. Opaque black shields are mounted to the pedestal adjacent the pedestal side surfaces.

Translucent white diffuser plates are also mounted to the pedestal adjacent the pedestal side surfaces. The diffuser plates are trapezoidal to prevent their ends from appearing in the camera image.

The pedestal top surface in this embodiment is a generally curved surface with a flat circular center portion. The flat center portion has its diameter approximately equal in measurement to that of a side of a semiconductor to be inspected. The diameter of the flat center portion illustrated in Figure 12 is larger than the diameter of the raised portion illustrated in Figure 11 to allow inspection of larger semiconductors. The remainder of the pedestal top surface not covered by the raised portion is covered by a black shield. The pedestal in this embodiment does not have angled surface portions. A side light source is mounted adjacent the sides of the elongated pedestal. The mirrors, the semiconductor, the semiconductor pins, and the camera or other imaging device are as previously described. Light emitted from the side light sources passes through the diffuser plates, and light emitted from the back light sources passes through the diffuser block. As in the previous embodiments, light from the back light sources passes through the diffuser block and pedestal, illuminating the pins of the semiconductor and sending a silhouetted image of the pins to the camera or other imaging device.

Figure 14 illustrates another embodiment of the inspection stand, which differs from that described above in the design of its inspection hardware unit. The inspection ring is also generally rectangular in cross-section when viewed from above, and also includes an aperture with a generally rectangular cross- section when viewed from above. Each aperture sidewall includes an angled surface extending between the inspection ring top surface and an aperture sidewall. Each sidewall of the inspection ring includes a rectangular cutout that extends through the sidewall to the aperture. These cutouts are designed to accommodate side lights mounted on the inspection hardware support ring, and allow light from the side lights to reach the pedestal located within the inspection ring. An inspection ring lip is formed at the lower end of the corner of each aperture sidewall. The rest of the inspection hardware unit is similar to that of the earlier embodiment. In this embodiment, the vertical position of the diffuser plate (not shown) can be adjusted to accommodate pedestals of different heights, and to assist the placement of a pedestal within the inspection station.

Claims

CLAIMSWhat is claimed is:

1. An apparatus for inspecting an object, said apparatus comprising: a transparent pedestal having a generally horizontal top surface for supporting thereon the object to be inspected.

2. An apparatus for inspecting an object as set forth in claim 1 , wherein said apparatus is a semiconductor inspection apparatus.

3. An apparatus as set forth in claim 1 , and further comprising an optical detector for receiving an image of the object.

4. An apparatus as set forth in claim 3, wherein said optical detector is a camera.

5. An apparatus as set forth in claim 1, wherein said pedestal includes a side surface and said apparatus further comprises a light source adjacent said side surface.

6. An apparatus as set forth in claim 1 , wherein said pedestal includes a side surface having a first portion and said apparatus includes a white diffuser mounted on said side surface adjacent said first portion.

7. An apparatus as set forth in claim 6, wherein said pedestal side surface includes a second portion and said apparatus includes a black shield mounted on said side surface adjacent said second portion.

8. An apparatus as set forth in claim 1, wherein said pedestal includes a side surface having a first portion and said apparatus includes a black shield mounted on said side surface adjacent said first portion.

9. An apparatus as set forth in claim 1 , wherein said pedestal has an internally mirrored bottom surface.

10. An apparatus as set forth in claim 1, wherein said pedestal includes a generally vertical side surface, and an angled surface portion extending between said top surface and said side surface.

11. An apparatus as set forth in claim 10, wherein said angled surface portion extends from said side surface to said top surface at an angle of approximately 35 degrees from horizontal.

12. An apparatus as set forth in claim 10, said apparatus further comprising an optical detector for receiving an image of the object, and wherein said apparatus includes a light source mounted adjacent said side surface, and a reflective element mounted adjacent said angled surface to reflect light from said light source to said optical detector.

13. An apparatus as set forth in claim 1, and further comprising a reflective element mounted adjacent said pedestal to reflect light passing through said pedestal.

14. A semiconductor inspection apparatus comprising: a transparent pedestal having a generally horizontal top surface for supporting thereon an object to be inspected, a generally vertical side surface, and an angled surface portion extending between said top surface and said side surface; an optical detector for receiving an image of the object; a light source mounted adjacent said side surface; and a mirror mounted adjacent said angled surface to reflect light from said light source to said optical detector.

15. An apparatus as set forth in claim 14, wherein said optical detector is a camera.

16. An apparatus as set forth in claim 14, wherein said pedestal side surface includes a first portion, and said apparatus includes a white diffuser mounted on said side surface adjacent said first portion.

17. An apparatus as set forth in claim 16, wherein said pedestal side surface includes a second portion, and said apparatus includes a black shield mounted on said side surface adjacent said second portion.

18. An apparatus as set forth in claim 14, wherein said pedestal side surface has a first portion, and said apparatus includes a black shield mounted on said side surface adjacent said first portion.

19. An apparatus as set forth in claim 14, wherein said pedestal has an internally mirrored bottom surface.

20. An apparatus as set forth in claim 14 wherein said angled surface portion extends from said side surface to said top surface at an angle of approximately 35 degrees from horizontal.

21. A semiconductor inspection apparatus comprising: a transparent pedestal having a generally frustoconical top surface for supporting thereon an object to be inspected and a generally vertical side surface; an optical detector for receiving an image of the object; a light source mounted adjacent said side surface; and a mirror mounted adjacent said angled surface to reflect light from said light source to said optical detector.

22. An apparatus as set forth in claim 21, wherein said optical detector is a camera.

23. An apparatus as set forth in claim 21, wherein said pedestal side surface includes a first portion, and said apparatus includes a white diffuser mounted on said side surface adjacent said first portion.

24. An apparatus as set forth in claim 23, wherein said pedestal side surface includes a second portion, and said apparatus includes a black shield mounted on said side surface adjacent said second portion.

25. An apparatus as set forth in claim 21, wherein said pedestal side surface has a first portion, and said apparatus includes a black shield mounted on said side surface adjacent said first portion.

26. An apparatus as set forth in claim 21 , wherein said pedestal includes a bottom surface and a white diffuser mounted adjacent said bottom surface.

27. A semiconductor inspection apparatus comprising: a transparent pedestal having a generally curved top surface including a generally horizontal center portion for supporting thereon an object to be inspected and a generally vertical side surface; an optical detector for receiving an image of the object; a light source mounted adjacent said side surface; and a mirror mounted adjacent said angled surface to reflect light from said light source to said optical detector.

28. An apparatus as set forth in claim 27, wherein said optical detector is a camera.

29. An apparatus as set forth in claim 27, wherein said pedestal side surface includes a first portion, and said apparatus includes a white diffuser mounted on said side surface adjacent said first portion.

30. An apparatus as set forth in claim 29, wherein said pedestal side surface includes a second portion, and said apparatus includes a black shield mounted on said side surface adjacent said second portion.

31. An apparatus as set forth in claim 27, wherein said pedestal side surface has a first portion, and said apparatus includes a black shield mounted on said side surface adjacent said first portion.

32. An apparatus as set forth in claim 27, wherein said pedestal includes a bottom surface and a white diffuser mounted adjacent said bottom surface.