Patent Publication Number: US-6212962-B1

Title: Hot bottle inspection apparatus and method

Description:
This is a divisional of application Ser. No. 08/914,984, filed Aug. 20, 1997, now U.S. Pat. No. 6,089,108, which is a continuation-in-part of application Ser. No. 08/509,049, filed Jul. 31, 1995, now U.S. Pat. No. 5,734,467, and of application Ser. No. 08/526,897, filed Sep. 12, 1995, now U.S. Pat. No. 6,025,910, which are all hereby specifically incorporated by reference for all that is disclosed therein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to glass bottle production and, more particularly, to a glass bottle inspection apparatus adapted for use at the hot end of a glass bottle production line. 
     BACKGROUND OF THE INVENTION 
     The manufacture of glass bottles begins with the preparation of raw materials. Sand and soda ash are measured in precise quantities, mixed together and conveyed to storage silos located over large melting furnaces. The mixed materials are continuously metered into the furnaces to replace molten glass which is dispensed from the furnaces after melting. 
     The furnaces are heated by a combination of natural gas and electricity and are operated at a temperature of over 2500 degrees Fahrenheit. The melted mixture of raw materials forms molten glass which flows from the furnaces through refractory channels, also known as forehearths, to a position over bottle forming machines. 
     A bottle forming machine known in the industry as an “I.S. machine” draws the glass into individual gobs and drops each gob into a blank mold. The blank mold forms a bottle preform, also referred to as a parison. The preform is transferred to a blow mold where it is blown by compressed air into a bottle. Each blow mold cavity typically contains indicia provided on a bottom wall thereof which embosses each bottle with code characters indicating the mold cavity in which it was formed. 
     The molds are lubricated by oil-borne carbon. The hot mold vaporizes the oil and some of the carbon immediately upon contact, leaving most of the carbon deposited upon the mold. Thus, the area around the mold is an extremely dirty environment filled with oil and carbon vapors and condensate. 
     An I.S. machine typically has between six and sixteen individual sections, with each section having from one to four blow mold cavities. Each section may be capable of manufacturing one to four bottles at a time. A typical eight section, triple gob, I.S. machine used in the production of beer bottles may produce 270 beer bottles per minute. 
     After the bottles have been blown, they are transferred from the respective blow mold cavities onto a moving conveyor belt. The bottles are positioned on the moving conveyor belt in a single line in a sequence corresponding to the sequence of the blow mold cavities in which the bottles were formed. The finished bottles transferred onto the conveyor from the blow mold are still red hot (approximately 1,000 degrees Fahrenheit). These hot bottles are conveyed by the conveyor belt through a hot end coating hood where they are chemically treated with a stannous chloride compound for strengthening. Vapors from the hot end coating hood also contribute significantly to the harsh environment found at the “hot end” of the bottle production line. 
     After passing through the hot end coating hood, the hot bottles are conveyed through an annealing oven or lehr where they are reheated and then cooled in a controlled manner to eliminate stresses in the glass. This annealing process typically takes from 20 to 30 minutes. The annealing process is the last process which takes place at the hot end of the production line. The portion of the production line downstream from the annealing oven is referred to as the “cold end” of the production line. In contrast to the hot end, the cold end is neither hot nor dirty. At the cold end of the production line, bottles are conveyed through a series of inspection devices. Typical prior art inspection devices include a squeezer which physically squeezes each bottle to check its sidewall strength. Another prior art cold end inspection device is referred to in the industry as a total inspection machine or T.I.M. which is sold by Emhart Glass having a business address of 123 Day Hill Road, Windsor, Conn. 06095. The total inspection machine physically engages each bottle and checks the size of the bottle neck opening and the thickness of the bottle sidewall and reads the code on the bottle bottom wall to determine the mold of origin. On a statistical sampling basis, the T.I.M. also sends bottles off line to be tested for burst strength, weighing, and measuring. Reports generated from the T.I.M. correlate bottle defects with the mold of origin. Another typical prior art inspection device is known as a “super scanner” sold by Inex, 13327 U.S. 19 North, Clearwater, Fla. 34624. The super scanner operates on each bottle on line. It initially scans a bottle, then engages and rotates the bottle approximately 90 degrees and scans it again. The super scanner uses image analysis to perform certain dimensional parameter checks of the bottle. 
     At both the T.I.M. and the super scanner inspection stations, defective bottles may be rejected by a cold end rejection device. After passing through the cold end inspection stations, bottles are transferred to a case packer machine, placed into a cardboard carton and conveyed to a palletizer machine for being placed in pallets. Loaded pallets are then shipped to a filling facility, such as a brewery. 
     A problem experienced with traditional glass bottle manufacturing operations as described above results from the fact that the bottle inspection stations are located at the cold end of the bottle production line. If a particular blow mold cavity begins producing defective bottles, e.g. as a result of a foreign object in the mold, the first defective bottle produced will not be detected until 30 to 40 minutes after its formation in the blow mold. As a result of this detection delay, the defective mold cavity will have continued to produce hundreds of defective bottles during the period between the first defective production and discovery of the first defective bottle. Furthermore, unless the defect is a defect of the type discovered by the T.I.M. machine which also identifies each bottle with a blow mold, the mold causing the problem will not be immediately apparent to the operator. As a result, the production operation must be shut down and each of the mold cavities of the I.S. machine must be inspected to detect the origin of the problem. Such shut down and inspection may be very time consuming and results in significant production loss in addition to the scrap produced by the defective mold cavity. Locating an inspection machine at the hot end of the bottle production line is difficult for a number of reasons: (1) as a result of the elevated temperature of the bottles at the hot end of the line, any engagement of the bottles by an inspection machine as is conventional with cold end inspectors would result in deformation of the bottle surface producing an ascetically unacceptable bottle; (2) the heat of the bottles at the hot end causes the bottles to glow and would thus make reading of mold origin indicating characters on the base of the bottle extremely difficult or impossible; (3) the contaminants in the atmosphere at the hot end of the line tend to coat the surface of any optical device used to image the bottles rendering imaging difficult or impossible; (4) the extreme heat and contamination at the hot end of the line is damaging to any electronics used on inspection devices positioned at the hot end. 
     A solution to these problems is addressed in U.S. Pat. No. 5,437,702 of Burns et al. for HOT BOTTLE INSPECTION APPARATUS AND METHOD, which is hereby specifically incorporated by reference for all that is disclosed therein. The Burns et al. patent discloses a non-contacting optical imaging inspection system that is located at the hot end of a bottle line. The optics and electronics employed are shielded from the harsh environment at the hot end of the production line by a fluid cooled housing. Clear panels in one of the housing walls enable the imaging devices within the housing to image passing bottles without the optics thereof being exposed to the harsh environment of the hot end. Fluid jets are provided adjacent to these clear panels in order to prevent contaminants from building up on the outer surface of the panels. Monitoring signals from the I.S. machine and the bottle conveyor are processed by data processing apparatus to determine the mold of origin of each bottle which is being imaged, thus obviating the need to read indicia on the surface of a glowing bottle. The image data from each bottle is analyzed to determine whether or not the bottle is defective. 
     Although this machine generally works well, it has been found that the clear panels of the fluid cooled housing still occasionally become dirtied, requiring maintenance and/or resulting in degradation of performance. 
     A solution to these problems associated with clear panels has been addressed in U.S. Pat. No. 6,025,910 of Lucas, as previously referenced. 
     The Lucas application discloses fluid cooled housings in which the clear panels discussed above have been replaced with unobstructed openings which allow pressurized cooling fluid contained in the fluid cooled housing to escape therethrough. Although this arrangement effectively eliminates the problems associated with dirty panels discussed above, it has been found that the unobstructed openings generally allow cooling air to escape the housing at too great a rate, thus making it difficult to maintain positive pressure within the housing. It has further been found that eddy currents sometimes form around the edges of the unobstructed openings, causing contaminated air from the exterior of the housing to be drawn into the housing. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an improved housing for imaging devices and associated electronics. An imaging device within the housing may be focused at a target area through an unobstructed window opening formed in a wall of the housing. The housing includes a sleeve member which may be attached to the housing in the vicinity the unobstructed window opening. The sleeve member is positioned in close proximity to the imaging device contained within the housing, thus creating a restricted air path between the sleeve member and the imaging device which restricts the flow of cooling air exiting the housing. The imaging device may be mounted on a slide mount system such that it is adjustably moveable toward and away from the sleeve. In this manner, the air restriction formed between the sleeve and the imaging device may be varied in order to adjustably control the amount of air restriction imposed and, thus, adjustably control the rate at which cooling air exits the housing. 
     The present invention is also directed to a laser triggering system in which the laser trigger device is mounted in a location such that the laser beam generated by the laser triggering system intersects the target area at a steep angle. This arrangement prevents interference with the laser beam by human operators who, from time to time, may be located near the target area. 
     The present invention is also directed to the use of an electronically shuttered imaging device and an associated light source. The light source may be a conventional AC powered halogen light source which is operated at a wattage lower than its rated wattage in order to prevent the detrimental effects of AC induced light fluctuations. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     An illustrative and presently preferred embodiment of the invention is shown in the accompanying drawing in which: 
     FIG. 1 is a schematic diagram of a glass bottle production line; 
     FIG. 2 is a schematic top plan view of a hot bottle inspection apparatus with its top member removed for clarity and a portion of an associated conveyor belt; 
     FIG. 3 is a schematic top plan view of another embodiment of the hot bottle inspection apparatus shown in FIG. 2; 
     FIG. 4 is a schematic front elevation view of a defective bottle; 
     FIG. 5 is a schematic front elevation view of a non-defective bottle; 
     FIG. 6 is a schematic front elevation view illustrating the process used to analyze a bottle that is randomly oriented; 
     FIG. 7 is a flow chart illustrating the steps taken to compensate for randomly oriented bottles. 
     FIG. 8 is a plan view of the imaging device of FIG. 2 schematically illustrating a bottle that is transversely misaligned. 
     FIGS. 9A-9C schematically illustrate a bottle image from a first imaging device, a bottle image from a second imaging device and a combined bottle image, respectively, when the bottle being imaged is transversely misaligned closer to the imaging devices. 
     FIGS. 10A-10C schematically illustrate a bottle image from a first imaging device, a bottle image from a second imaging device and a combined bottle image, respectively, when the bottle being imaged is transversely aligned. 
     FIGS. 11A-11C schematically illustrate a bottle image from a first imaging device, a bottle image from a second imaging device and a combined bottle image, respectively, when the bottle being imaged is transversely misaligned further from the imaging devices. 
     FIG. 12 is a schematic top plan view of another embodiment of a hot bottle inspection apparatus with its top member removed for clarity and a portion of an associated conveyor belt; 
     FIG. 13 is a cross-sectional elevation view of a hot bottle inspection apparatus housing taken along the line  13 — 13  in FIG.  12 . 
     FIG. 14 is front elevation partial cutaway view of the hot bottle inspection apparatus housing of FIG.  13 . 
     FIG. 15 is a cross-sectional elevation view of a bottle conveyor and an associated laser triggering device. 
     FIG. 16 is a cross-sectional elevation view of a bottle conveyor and another embodiment of a laser triggering device. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In general, the invention may pertain to an apparatus  64  for measuring at least one unknown characteristic of objects  52 ,  54 ,  56  being conveyed along an object pathway on a conveyor  12 . The apparatus includes an enclosure  350  located adjacent the conveyor  12 . The enclosure  12  has an enclosure interior located within the enclosure  350  and an enclosure exterior located outside of the enclosure  350 . The enclosure  350  also has an opening  372  which extends between the enclosure exterior and the enclosure interior and a sleeve member  390  having a first end  398  and a second end  400 . The sleeve member first end  398  is located proximate the enclosure opening  372 . An image generating device  104  is located in the enclosure interior and aimed through the sleeve member  390  at a location  50  within the object pathway. The sleeve member second end  400  is located proximate the image generating device  104 . 
     The invention may also include a method of measuring at least one unknown characteristic of objects  52 ,  54 ,  56  being conveyed along an object pathway on a conveyor  12 . The method includes the steps of providing an enclosure assembly  350  located adjacent the conveyor  12  which includes an enclosure assembly interior located within the enclosure assembly  350  and an enclosure assembly exterior located outside of the enclosure assembly  350 ; pressurizing the enclosure assembly interior to a pressure higher than that of the enclosure assembly exterior; providing a passageway  396  extending between the enclosure assembly exterior and the enclosure assembly interior; providing a flow of air  502 ,  504  from the enclosure assembly interior to the enclosure assembly exterior through the passageway  396 ; providing an image generating device  104  in the enclosure assembly interior; aiming the image generating device  104  through the passageway  396  at a location  50  within the object pathway; and restricting the flow of air through the passageway  396  by locating the image generating device  104  in proximity to a portion  390  of the enclosure assembly adjacent the passageway  396 . 
     The invention may also pertain to an apparatus  64  for measuring at least one unknown characteristic of objects  52 ,  54 ,  56  being conveyed along an object pathway on a conveyor  12 . The apparatus  64  includes a first enclosure  300  located adjacent the conveyor  12  and a second enclosure  350  located adjacent the conveyor  12 . Each of the first and second enclosures  300 ,  350  include: an enclosure interior located within the enclosure  300 ,  350  and an enclosure exterior located outside of the enclosure  300 ,  350 ; an opening  372  in the enclosure, the opening  372  extending between the enclosure exterior and the enclosure interior; a sleeve member  390  having a first end  398  and a second end  400 , the sleeve member first end  398  located proximate the enclosure opening  372 ; an image generating device  104  located in the enclosure interior and aimed through the sleeve member  390  at a location  50  within the object pathway; and the sleeve member second end  400  located proximate the image generating device  104 . 
     The invention may also pertain to an apparatus for imaging objects  52 ,  54 ,  56  being conveyed along an object pathway located on a conveyor  12 . The apparatus may include a substantially planar conveyor upper surface  13 , FIG. 16, located on the conveyor  12  and upon which the objects  52 ,  54 ,  56  are supported while being conveyed along the object pathway; at least one image acquisition device  102 ,  104  located adjacent the conveyor  12  and aimed at a location within the object pathway; and a laser triggering system including a laser emitting device  510 , a laser reflecting device  514  and a laser sensing device  510 . The plane of the substantially planar conveyor upper surface  13  defines a first space located on one side of the plane and a second space located on the opposite side of the plane from the first space. The laser emitting device  510  is located in the first space and the laser reflecting device  514  is located in the second space. 
     Having thus described the method and apparatus for measuring unknown characteristics of an object in general, further features thereof will now be specifically described. 
     FIG. 1 is a schematic illustration of a glass bottle production line  10 . The production line comprises a conveyor  12  which defines a bottle conveyance path. The conveyor moves bottles downstream in direction  14 . A conveyor monitor assembly  16  which may be, for example, a conventional electronic encoder mounted on a conveyor motor shaft, monitors the conveying movement of conveyor  12  and produces a conveyor displacement signal  18  representative thereof. In most bottle production lines the conveyor  12  is mechanically linked to the drive mechanism of the blow mold such that conveyor speed is always directly proportional to the speed of operation of the blow mold. In such a case any device which monitors mold displacement, for example, an incremental encoder mounted on the shaft of the mold drive unit, would also indicate conveyor displacement and is to be considered a conveyor monitor. 
     A blow mold assembly  30  comprises a plurality of mold cavity portions  32 ,  34 ,  36 , etc. The blow mold assembly  30  may comprise a portion of a conventional I.S. machine. The blow mold assembly  30  is positioned at an upstream end  38  of conveyor  12 . A mold monitor assembly  42  generates a mold transfer signal  44  each time the blow mold  30  transfers bottles onto conveyor  12 . Bottles  52 ,  54 ,  56 , etc. are produced by mold cavity portions  32 ,  34 ,  36 , etc. and are transferred to conveyor  12  in single file in a sequence corresponding to the sequence of their respective blow mold cavities of origin. The bottles  52 ,  54 ,  56  may be formed with indicia thereon indicative of the blow mold cavity of origin. The bottles  52 ,  54 ,  56 , etc. are transferred onto the conveyor  12  at an elevated temperature which may be approximately 1000 degrees Fahrenheit such that the bottles are glowing. 
     A hot coating hood  62  is positioned at a station along the conveyor  12  a short distance downstream, e.g. 10 feet, from the blow mold  30 . 
     A hot bottle inspection apparatus, also referred to herein as a hot bottle inspector  64 , is positioned at a fixed station along the conveyor which may be a short distance, e.g. two feet, downstream from the hot coating hood  62 . The hot bottle inspector  64  may thus be located in an extremely hot and dirty environment at the hot end  80  of the production line. A remote computer  66  removed from the harsh environment at the hot end of the production line is operably connected to the hot bottle inspector  64  and is accessible to a production line operator. A rejection device  68  may be positioned immediately downstream from the hot bottle inspector  64  and is operable to remove bottles from the conveyor in response to commands from the hot bottle inspector  64 . 
     An annealing oven  70  of a conventional type may be positioned downstream of the rejection device  68  and defines, at its downstream end portion  72 , the terminal end portion of the “hot end”  80  of the bottle production line  10 . In a typical production line used for producing glass beer bottles, the period of time elapsing from the transfer of a bottle onto the conveyor  12  by the blow mold  30  to the exit of that bottle from the downstream end  72  of annealing oven  70  may be thirty minutes. 
     The portion of the production line  10  located downstream of the annealing oven exit  72  constitutes the “cold end”  82  of the production line. The cold end of the production line may comprise conventional cold end inspection devices  84 ,  86 ,  88  such as a squeezer, a T.I.M. machine, and a super inspector machine such as previously described in the “Background of the Invention” section of this application. The first of these cold end inspectors  84  may be positioned, e.g. 100 feet, downstream from the exit  72  of annealing oven  70 . A conventional packing assembly  92 , such as described above, may be provided downstream from the cold end inspection devices  84 ,  86 ,  88 . 
     As best illustrated by FIG. 2, the hot bottle inspection apparatus  64  comprises a housing  100 . This housing contains a first imaging device  102  and a second imaging device  104 . 
     Housing  100  may comprise front wall  109 , first side wall  111 , second side wall  113  and rear wall  115 . The housing  100  may also include a top wall member, not shown. Housing  100  may have a length “a” of about 4′, a width “b” of about 2′ and a height of about 4′. 
     A data connection  106  is provided for transmitting the images acquired by first imaging device  102  and second imaging device  104  to remote computer  66 . Housing  100  may be insulated in order to withstand the intense heat of the hot end area  80 . Pressurized cooling fluid is supplied to the housing  100  via fluid line  108 . Fluid line  108  may supply a flow of pressurized filtered air to the housing for cooling purposes in a manner as described in the previously referenced U.S. Pat. No. 5,437,702. 
     Opening  110  is provided in the front wall  109  of housing  100  to allow a line of sight  103  between the bottle  52  and first imaging device  102 . Opening  112  is provided in the front wall  109  of housing  120  to allow a line of sight  105  between bottle  52  and second imaging device  104 . Leaving these areas open, rather than covering them with clear panels, obviates the problem previously described regarding the panels becoming dirty. Openings  110  and  112  may each measure about 1 inch by 1 inch. 
     FIG. 2 shows a series of bottles such as bottles  52 ,  54  and  56  moving along conveyor  12  past housing  100  in the direction indicated by the arrow  14 . As a bottle, such as bottle  52  in FIG. 2, moves into the target site  50 , strobe light  94  is energized thus causing the imaging devices  102  and  104  to produce images of the bottle  52 . The computer  66  then combines the images to arrive at a composite image as is well-known. 
     As previously described, the bottle forming “I.S. machine” generates signals in a well-known manner. Since the number of bottle molds within the I.S. machine is known, computer  66  can use these pulses to determine when each bottle is formed and thus when to energize the strobe light  94 . Since the order of bottles on the conveyor  12  corresponds to the mold order in the I.S. machine, the computer  66  is also able to correlate acquired image data to the I.S. machine mold which formed the bottle being imaged. In this manner, bottle conditions detected by the hot bottle inspection apparatus can be correlated to a specific mold. 
     In one example, the I.S. machine may generate one pulse per revolution and may produce 10 bottles per revolution. In this case, computer  66  would know that 10 bottles are produced per I.S. machine pulse. The use of this type of bottle tracking system obviates the need for photosensors or other physical detectors which would be adversely affected by exposure to the harsh environment of the hot end. 
     In operation, cooling fluid is introduced through fluid line  108  at a rate great enough to prevent dirt and outside air from the bottle hot end  80  from entering the housing  64 . The fluid entering the housing  100  maintains the interior of the housing at a pressure higher than that of the outside atmosphere. Although fluid will escape through the openings  110  and  112 , new cooling fluid is introduced through fluid line  108  at a rate great enough to compensate for this escaping fluid. This arrangement eliminates the need for a discharge orifice in the housing as disclosed in the previously referenced U.S. Pat. No. 5,437,702. This arrangement also eliminates the need for the maintenance previously required for cleaning the clear panels. The cooling fluid may be in the form of compressed air. 
     FIG. 3 illustrates an alternative embodiment of the invention in which a single opening  122  is provided in a housing  120  to accommodate both lines of sight  103  and  105 . Providing only one opening is advantageous since less cooling air escapes from one opening than escapes from two openings. Since less cooling air escapes, less cooling air needs to be supplied to the housing  120 . 
     Housing  120  contains a first imaging device  102  and a second imaging device  104 . Housing  120  may comprise front wall  121 , first side wall  123 , second side wall  125  and rear wall  127 . The housing  120  may also include a top wall member, not shown. Housing  120  may have a length “c” of about 2′, a width “d” of about 2′ and a height of about 4′. A data connection  106  is provided for transmitting the images acquired by first imaging device  102  and second imaging device  104  to remote computer  66 . Housing  120  may be insulated in order to withstand the intense heat of the hot end area  80 . Pressurized cooling fluid is supplied to the housing  120  via fluid line  108 . Fluid line  108  may supply a flow of pressurized filtered air to the housing for cooling purposes as described in the previously referenced U.S. Pat. No. 5,437,702. 
     An opening  122  is provided in the front wall  121  of housing  120  to allow a line of sight  103  between the first imaging device  102  and target site  134  located on conveyor  12 . Opening  122  also allows a line of sight  105  between second imaging device  104  and target site  132  located on the conveyor  12 . The imaging devices  102  and  104  are configured within housing  120  so that their lines of sight  103  and  105  cross in the vicinity of the opening  122  as shown in FIG.  3 . Configuring the imaging devices in this manner allows the use of one relatively small opening  122  in housing  120 , thus reducing the loss of cooling air from housing  120 . 
     Because of the configuration of imaging devices  102  and  104  described above, each imaging device will image a different bottle at any given time. In order to combine the proper images from imaging devices  102  and  104 , the remote computer  66  stores image data for a particular bottle from imaging device  104  until the same bottle moves into a position where it is imaged by imaging device  102 . The computer then assembles the image data from the two imaging devices  102  and  104  to obtain complete data for each bottle. 
     FIG. 3 shows a series of bottles such as bottles  124 ,  126 ,  128 , and  130  moving along conveyor  12  past housing  120  in the direction indicated by the arrow  136 . As a bottle, such as bottle  124  in FIG. 3, moves into the target site  132 , strobe light  138  is energized thus causing imaging device  104  to produce an image of the bottle  124 . This image is stored by the computer  66  until the bottle  124  moves into the target site  134  and strobe light  140  is energized, thus causing imaging device  102  to produce an image of the bottle  124 . The computer then combines the stored image from imaging device  104  with the newly acquired image from imaging device  102  to arrive at a complete image of bottle  124 . This process is repeated for each bottle conveyed by the conveyor  12 . Bottles are tracked by the computer  66  using I.S. machine pulses in a manner as previously described. 
     Opening  122  may measure about 1″ inch by 1 inch. In operation, cooling fluid is introduced through fluid line  108  at a rate great enough to prevent dirt and outside air from the bottle hot end  80  from entering the housing  120 . The fluid entering the housing  120  maintains the interior of the housing at a pressure higher than that of the outside atmosphere. Although fluid will escape through the opening  122 , new cooling fluid is introduced through fluid line  108  at a rate great enough to compensate for this escaping fluid. It has been found that supplying cooling fluid in the form of compressed air at a rate of about 2 standard cubic feet per minute is sufficient given the size of the housing  120  and the opening  122  as described above. The compressed air may be supplied to housing  120  at a temperature of about 30 degrees Celsius. 
     With respect to either housing  100  or housing  120 , the imaging devices  102  and  104  may be located so that the center of their lenses are vertically aligned with the plane of the top of the conveyor  12 . This results in the imaging devices being located substantially below the plane of the conveyor. Since heat rises, this location is cooler and thus less damaging to the imaging devices. This location also allows the plane of the conveyor to be conveniently used as a reference plane when analyzing bottle image data. 
     In another embodiment, the hot bottle inspection system housing may actually comprise two separate housing units, one for each imaging device  102 ,  104 , as generally shown, for example, in FIG.  12 . The use of two separate housings may make personnel access to the bottle line easier in some situations. 
     Air Loss Reduction 
     As previously described with reference to FIGS. 2 and 3, the housings  100  and  120  are pressurized via cooling air supplied through the fluid line  108 . Pressurized air within the housings is then allowed to escape through the unobstructed housing openings ( 110  and  112  in the housing  100 , FIG. 2, and  122  in the housing  120 , FIG.  3 ). This escaping air prevents dirt and other contaminants from entering the housings  100 ,  120  through the openings  110 ,  112  and  122 . 
     Although the pressurized housings described above generally function well, it has been found that, due to the size of the openings  110 ,  112  and  122 , a relatively large amount of compressed cooling air must be supplied to the housings via the line  108  in order to maintain an adequate pressure differential and air flow through the openings. It has also been found that eddy currents sometimes form near the edges of the openings  110 ,  112  and  122 , causing a small amount of outside air, dirt and other contaminants to be drawn into the housings  100 ,  120 . 
     Another embodiment of the hot bottle inspection system which addresses the problems described above is illustrated in FIGS. 12-14. Referring now to FIG. 12, it can be seen that two separate housings  300 ,  350  may be provided to house the image generating devices  102 ,  104 , respectively. The housings  300 ,  352  may be arranged near the hot bottle conveyor  12  as shown. A line of sight  302  may extend between the imaging device  102 , housed withing the housing  300 , and a target sight  50  located on the conveyor  12  in a manner similar to that previously described. A line of sight  352  may extend between the imaging device  104 , housed within the housing  350 , and the target sight  50 . The lines of sight  302 ,  352  may form an angle “e” of about 90 degrees with respect to each other. Each housing  300 ,  352  may be located at a distance “f” from the target area  50  of about twelve inches, measured along the respective line of sight  302 ,  352 , as shown in FIG.  12 . 
     Each of the image generating devices  102 ,  104  may be connected to a data connection line  306 ,  356 , respectively, in order to connect the image generating devices to a remote computer, in a similar manner to that previously described with respect to the data connection line  106 . 
     The housings  300 ,  350  may be substantially identical to one another. Accordingly, only the housing  350  will be described in further detail herein, it being understood that the housing  300  may be constructed in a substantially identical manner. 
     Referring to FIG. 12, it can be seen that the housing  350  may comprise a two-piece assembly comprising a unitarily formed box portion  360  and a cover member  366  which, when assembled, together form a generally parallelepiped shaped structure. The box portion  360  may include a bottom wall  362 ; a front wall  370  extending upwardly from the bottom wall  362  at a substantially right angle thereto; a rear wall  368  extending upwardly from the bottom wall  362  and being substantially parallel to the front wall  370 ; a side wall  364  connecting the bottom wall  362 , the front wall  370  and the rear wall  368  and being substantially perpendicular to the bottom wall  362 , the front wall  370  and the rear wall  368 ; and a top wall  380 , FIG. 13, substantially parallel to the bottom wall  362  and connecting the front wall  370 , the side wall  364  and the rear wall  368 . 
     The cover member  366  may attach to the box portion  360  via screws (not shown) or via any conventional attachment method. An O-ring gasket (not shown) may be provided between the box portion  360  and the cover member  336  in order to provide an airtight seal between the box portion  360  and the cover member  366  in a conventional manner. In this manner, the cover member  366  may be removed to provide access to the imaging device  104  and to the other contents of the housing  350  and replaced in order to provide an airtight housing. When the cover member  336  is attached to the box portion  360 , a seam  361  is formed between the cover member  336  and the box  360  as shown in FIGS. 12 and 13. 
     As best shown in FIGS. 13 and 14, a hole  372  may be formed through the housing front wall  370 . The hole  372  may be generally circular and have a diameter “g” of about 1.0 inch, FIG.  13 . 
     Referring again to FIG. 13, the housing  350  may be provided with a cooling fluid supply line  354  in order to supply pressurized cooling air in a manner as previously described with respect to the cooling fluid supply line  108 . The fluid supply line  354  may terminate in a fitting  355  which may be threadingly engaged within a threaded hole  363  formed in the housing bottom wall  362 . The hole  363  terminates at the inner surface of the housing bottom wall  362  to form an orifice  365  through which compressed cooling air enters the interior of the housing  350 . 
     The data connection lines  356  may pass through a hole  367  formed in the housing bottom wall  362 . Exteriorly of the housing  350 , the data connection lines  356  may be carried within a protective conduit  358  as shown in a conventional manner. The hole  367  may be sealed at the inner surface of the housing bottom wall  362  by applying a quantity of sealant material  369  as shown in order to prevent pressurized cooling air within the interior of the housing  350  from escaping through the hole  367  around the data connection lines  356 . The sealant material  369  may be a sealant material such as a high temperature rubber or may be any other conventional type of sealant material. 
     The housing  350  may be constructed of cast aluminum, with the walls  362 ,  364 ,  368 ,  370 ,  380  and the lid member  366  each having a wall thickness of about {fraction (3/16)} inch. With the exception of the opening  372  formed in the front wall  370  and the openings  363  and  367  in the bottom wall  362  to accommodate the various connections, as previously described, the housing  350  may be of the type known generally in the industry as a “NEMA 12 rated enclosure” and generally available from The Hoffman Engineering Company of Anoka, Minn. and sold as Model No. PX12. The housing  350  may have an overall height “i” of about 6.0 inches, an overall length “j” of about 12.0 inches, FIG. 13, and an overall width “k” of about 3.0 inches, FIG.  12 . 
     Referring again to FIG. 13, an annular sleeve member  390  may be attached to the housing front wall  370  in the vicinity of the opening  372  as shown. The sleeve member  390  may be formed as an annular cylinder having an outer surface  392  and an inner surface  394  forming a cylindrical passageway  396  therewithin. A front annular surface  398  extends between the sleeve member outer and inner surfaces  392 ,  394  at a forward end of the sleeve member  390 . In a similar manner, a rear annular surface  400  extends between the sleeve member outer and inner surfaces  392 ,  394  at a rearward end of the sleeve member  390 . The cylindrical passageway  396  terminates at a forward open end  402  which is surrounded by the sleeve member front annular surface  398  and at a rear open end  404  which is surrounded by the sleeve member rear annular surface  400 . The sleeve member outer surface  392  may have a diameter which is substantially equal to the housing front wall opening  372  diameter “g” as previously described. The sleeve member inner surface  394  may have a diameter “h” of about ⅞ inch. Accordingly, with the example dimensions set forth above, the annular sleeve member  390  may have a wall thickness of about 0.0625 inches. The sleeve member  390  may have a length “l” of about 1.0 inch, extending between the front surface  398  and the rear surface  400 . The sleeve member  390  may be constructed of a phenolic material and may be formed in any conventional manner such as by machining. 
     The sleeve member  390  may be attached to the housing front wall  372  in any suitable manner which provides an air-tight seal between the sleeve member and the front wall. In a preferred method, however, as shown in FIGS. 12 and 13, attachment may be accomplished by press-fitting the sleeve member  390  into the housing front wall opening  372 . 
     Turning again to FIG. 13, the imaging device  104  may be mounted within the housing  350  via an adjustable mounting assembly  410 . Adjustable mounting assembly  410  generally includes an upper L-shaped bracket  420  and a lower L-shaped bracket  460 . Upper bracket  420  is formed from a first, generally horizontally disposed leg portion  422  and an integrally formed generally vertically disposed leg portion  430 . A pair of through holes  424  (only one is shown) are formed in the upper bracket horizontal leg  422  as shown. A pair of bolts  426  (only one is shown) may be passed through the holes  424  and threadingly engaged with a lower portion of the imaging device body portion  119 , as shown, in order to securely attach the imaging device  104  to the upper bracket  420 . The upper bracket vertical leg  430  may include a pair of threaded holes  432  (only one is shown) for a purpose as will be described hereafter. 
     Lower bracket  460  is formed from a first, generally horizontally disposed leg portion  462  and an integrally formed generally vertically disposed leg portion  470 . A pair of slotted holes  472  and  476 , FIGS. 13 and 14, may be provided in the lower bracket vertical leg  470  as shown. A pair of bolts  474  and  478  may be passed through the lower bracket slotted holes  472 ,  476 , respectively, and threadingly engaged within the upper bracket threaded holes  432  in order to securely attach the upper bracket vertical leg  430  to the lower bracket vertical leg  470 . 
     Lower bracket horizontal leg  462  may include a pair of threaded holes  464  (only one is shown). A pair of bolts  466 ,  467 , FIGS. 13,  14 , are passed through a pair of slots  371 ,  373  formed in the housing lower wall  362  as shown in FIGS. 13 and 14. The bolts  466 ,  467  threadingly engage within the lower bracket horizontal leg threaded holes  464  in order to securely attach the lower bracket  460  to the housing lower wall  362 . 
     In the manner described above, the image generating device  104  is securely attached to the housing  350  via the adjustable mounting assembly  410 . The adjustable mounting assembly  410  allows the position of the image generating device  104  to be adjusted relative to the housing  350  in several degrees of movement as will now be described in detail. 
     As can be appreciated, when the bolts  474 ,  478  are sufficiently loosened, the slotted holes  472 ,  476  allow the upper bracket  420 , along with the attached imaging device  104 , to be vertically adjusted with respect to the housing  350  and attached lower bracket  460 , i.e., adjusted in the directions indicated by the arrow  490  in FIG.  13 . Due to the clearance between the slotted holes  472 ,  476  and the bolts  474 ,  478 , respectively, loosening the bolts  474 ,  478  also allows limited rotational adjustment of the image generating device  104  in the directions indicated by the arrow  492  in FIG.  14 . 
     As can further be appreciated, when the bolts  466 ,  467  are sufficiently loosened, the slotted holes  371 ,  373 , respectively, allow the entire adjustable mounting assembly  410 , along with the attached imaging device  104 , to be horizontally adjusted with respect to the housing  350 , i.e., adjusted in the directions indicated by the arrow  494  in FIG.  13 . Due to the clearance between the slotted holes  371 ,  373  and the bolts  466 ,  467 , respectively, loosening the bolts  466 ,  467  also allows limited rotational adjustment of the adjustable mounting assembly  410  and the attached image generating device  104  relative to the housing  350  in the directions indicated by the arrow  496  in FIG.  12 . 
     The adjustable mounting assembly  410 , thus, allows the imaging device  104  to easily be aligned with the sleeve member  390 . It is noted that, although a preferred adjustable mounting assembly has been described in detail above, the imaging device  104  may, alternatively, be mounted to the housing  350  via any type of adjustable mounting assembly which allows for adjustable movement of the imaging device  104  relative to the housing  350 . 
     In a similar manner to the housings  100 , FIG. 2, and  120 , FIG. 3, previously described, the housing  350  may be supplied with pressurized cooling air in order to maintain the interior of the housing at relatively low temperature and, thus, protect the image generating device  104  from the heat of the hot end of the bottle manufacturing production line. Air entering the housing  350  through the cooling fluid supply line orifice  365  maintains the interior of the housing  350  at a higher pressure than the exterior of the housing. In a similar manner to the housings  100  and  120 , air escapes from the interior of the housing  350  through the opening  372  formed in the front wall  370  of the housing. Unlike the housings  100  and  120 , however, the housing  350  includes a mechanism for controlling the amount of air which escapes and for preventing the formation of eddy currents which sometimes occur in the vicinity of air flow openings. 
     Referring again to FIG. 13, it can be seen that the image generating device  104  may include a body portion  119  and a lens assembly  107  located at the forward end of the housing portion  119 , in a conventional manner. The lens assembly  107  may be formed as an annular cylinder having an outer surface  133  and an inner surface  135  forming a cylindrical passageway  137  therewithin. A front annular surface  131  extends between the lens assembly outer and inner surfaces  133 ,  135  at a forward end of the lens assembly  107 . The lens assembly outer surface  133  may have a diameter “n” of about 1.0 inch. The lens assembly inner surface  135  may have a diameter “m” of about {fraction (15/16)} inches. Accordingly, with the example dimensions set forth above, the lens assembly cylinder may have a wall thickness of about {fraction (1/32)} inch. The lens assembly  107  may also include a lens  118 . The lens  118  may be located within the lens assembly cylindrical passageway  137  in a conventional manner, and may be spaced a distance “o” of about ¼ inch from the lens assembly front annular surface  131  as shown. A photoelectric device  129  may also be located within the housing portion  119 . Photoelectric device  129  may be operatively associated with the lens  118  in a conventional manner and may, for example, be a charge couple device as described herein. 
     As can be appreciated with reference to FIG. 13, a restricted airflow opening  500  is formed between the sleeve member rear annular face  400  and the imaging device lens assembly forward annular surface  131 . In operation, pressurized air within the housing  350  passes through the restricted opening  500  and enters the sleeve member cylindrical passageway  396  through the sleeve member rear open end  404  as indicated by the airflow arrows  502 . Once within the cylindrical passageway  396 , the air then moves in a direction as indicated by the airflow arrows  504  and subsequently exits the housing  350  through the sleeve member forward open end  402 . 
     The amount of restriction imposed upon the exiting air may be controlled by adjusting the distance “p” between the lens assembly forward annular surface  131  and the sleeve member rear annular surface  400 . As can be appreciated, the distance “p” may be easily varied by loosening the bolts  466 ,  467  and sliding the adjustable mounting assembly  410  and attached image generating device  104  in the directions  494  in a manner as previously described. 
     Preferably, the sleeve member  390  is sized such that the sleeve member rear annular surface  400  fully encompasses the lens assembly forward annular surface  131 . In other words, the sleeve member  390  is preferably sized such that the sleeve member inside diameter “h” is less than the lens assembly inside diameter “m” and the sleeve member outside diameter “g” is greater than the lens assembly outside diameter “n”. When so configured, the effective area of the restricted opening  500  will be equal to the circumference of the lens assembly inner surface  135  (i.e., the circumference dictated by the diameter “m”) multiplied by the distance “p”. Accordingly, the effective area of the restricted opening  500  may be calculated according to the following equation: 
     
       
         
           m×Π×p 
         
       
     
     In one example, the distance “p” may be set to about 0.02 inches. According to the above equation, with the exemplary dimension “m”, of about {fraction (15/16)} inches, as set forth previously, this distance “p” of about 0.02 inches yields an effective area of about 0.059 square inches. It has been found that this arrangement provides satisfactory air flow through the housing  350  when air is supplied at a pressure of about 25 psi. Of course, with the novel design set forth above, the distance “p”, and thus the effective area of the restricted opening  500 , may easily be varied in order to compensate for variables such as cooling fluid supply pressure and external heat. 
     Like the housings  100  and  120 , previously described, the housing  350  provides an unobstructed line of sight  352  between the imaging device lens  118 , FIG. 13, and the target site  50 , FIG. 12, located along the conveyor  12 . This arrangement eliminates window panels made of glass or other materials which are prone to dirtying from the contaminated hot-end environment of a bottle production line. The housing  350 , however, differs from the housings previously described in that it provides a mechanism for controlling the amount of air which escapes from the housing. 
     The annular sleeve  390  not only provides air restriction to control the amount of air escaping from the housing  350 , but also serves to space the imaging device lens  118  from the contaminated environment exterior to the housing  350 . As can be appreciated from an examination of FIG. 13, increasing the length “l” of the sleeve member  390  will cause the imaging device lens  118  to be further spaced from the exterior environment. Increasing the distance “l” too much, however, may cause the sleeve member inner surface  394  to interfere with the imaging ability of the lens  118 . It has been found that the exemplary distance “l” of about 1.0 inch, as set forth above, provides adequate spacing of the lens  118  from the exterior environment while causing little if any interference with the optical ability of the lens. 
     It has further been found that use of the sleeve member  390 , as described above, also eliminates eddy currents which have sometimes been found to form around the openings of the housings  100 ,  120 . These eddy currents cause a small amount of contaminated air from the exterior environment to be drawn into the housings  100 ,  120 , thus exposing the imaging device or devices housed within to be exposed to the contaminated air. Thus, by eliminating such eddy currents, the sleeve member  390  serves to maintain the imaging device housed within the housing  350  in a cleaner fashion. 
     Correction for Orientation 
     The general technique of imaging of bottles onto photoelectric devices such as CCDs (charge couple devices) and the subsequent analysis of the data signal to measure various bottle parameters is well known in the art. It has been found, however, that measuring bottles at the hot end  80  of a bottle production line  10  presents problems which have not previously been solved. 
     As a result of the elevated temperature of the bottles at the hot end  80  of the production line  10 , any engagement of the bottles by an inspection machine, as is conventional with cold end inspectors, would result in deformation of the bottle surface producing an ascetically unacceptable bottle. This, along with the relatively high speed of bottle production line conveyors means that the bottles are often bouncing when a hot end inspection process is being carried out. Due to this bouncing, the exact orientation of a bottle when it is being inspected cannot be accurately determined. 
     The present invention overcomes this difficulty by first analyzing the bottle image to find a known feature of the bottle. The orientation of this feature, and thus the entire bottle, is then determined. The desired bottle measurements are then made and adjusted relative to the orientation of the known feature. This allows true measurements to be achieved even on randomly oriented bottles, such as bouncing bottles. 
     One example of a particular physical parameter which may be determined by the imaging device of the present invention is the degree to which the sidewalls of a bottle are perpendicular to its base. 
     FIG. 4 schematically illustrates a bottle  150 , the sidewalls  154 ,  156  of which are not perpendicular to its base  160 . This defective condition is commonly referred to as “lean” and bottles exhibiting this condition are commonly referred to as “leaners”. It should be noted that the lean depicted in FIG. 4 has been greatly exaggerated for purposes of illustration. FIG. 5 shows a non-defective bottle  170  exhibiting no perceptible lean. 
     The lean measured by the hot bottle inspection apparatus  64  may be compared with pre-determined values and any bottle having parameters exceeding a fixed tolerance from this value is determined by the system to be defective. It is noted, however, that, in the case of leaners, detecting even a slight lean that is within tolerance can be useful to bottle line process control. Leaners generally occur when the bottle formation temperature becomes too high. This high temperature causes the glass to be too soft and, thus, leaners occur. Accordingly, early detection of in-tolerance leaners can provide the bottle line operators with information indicating that the bottle formation process is becoming too hot. Adequate corrective action can then be taken to prevent further overheating and the occurrence of reject-level leaners. 
     Referring again to FIG. 2, it can be seen that first imaging device  102  and second imaging device  104  image the bottle  52  from different directions. This ensures that a leaner will be detected even if it is leaning directly toward or away from one of the imaging devices. In such a case, the other imaging device would still detect the lean. 
     The method employed to compensate for bottle orientation will now be described in detail. FIG. 6 illustrates an image of a bottle  138  generated, for example, by first imaging device  102 . The bottle  138  was imaged while it was bouncing and thus is shown in a random orientation in FIG.  6 . 
     Bottle lean may be characterized by the deviation of the center line AA of a bottle from vertical. In other words, deviation may be described as the difference between the horizontal location of the bottle centerline AA near the base  140  of the bottle and the horizontal location of the bottle centerline AA near the top of the bottle. If these horizontal locations are identical, then the bottle exhibits no lean. If they are different, however, then the bottle is a leaner and the magnitude of this horizontal difference characterizes the amount of lean. 
     A specific method for measuring lean will now be described in detail with reference to FIG.  6 . FIG. 7 is a block diagram illustrating this method. 
     First, the image is analyzed to determine if there is any light showing beneath the base  140  of the bottle image  138 . If no light is showing, this means that the bottle is setting flat on the conveyor  12  and is not bouncing. If light is showing, as in the case of FIG. 6, this means that the bottle is not setting flat on the conveyor and compensation must be made for the orientation of the bottle due to bouncing. 
     If the bottle is bouncing, then the “dynamic offset” is calculated. The dynamic offset is the amount of measured lean caused by the orientation of the bottle. To calculate the dynamic offset, the base  140 , left edge  142  and right edge  144  of the bottle are first located. Next a point “BL” is located on the base  140  of the bottle. The point BL is defined as a point located along the base  140  of the bottle at a predetermined distance in from the left edge  142  of the bottle. It is not desirable to use the actual corner of the bottle for the point BL since bottle corners are often rounded, making a precise location in this area difficult. 
     A point “BR” is then located on the base  140  of the bottle. The point BR is defined as a point located along the base  140  of the bottle at a predetermined distance in from the right edge  144  of the bottle. Both of the points BL and BR may be located the same distance in from their respective edges. This distance may, for example, be about 0.5 inches. 
     The dynamic offset is then calculated as: 
     
       
         ( BLx−BRx )/( BLy−BRy )×(2 y −1 y ) 
       
     
     where BLx is the location along the x-axis of point BL, BRx is the location along the x-axis of point BR, BLy is the location along the y-axis of point BL, BRy is the point along the y-axis of point BR and 2y and 1y are predetermined heights above the plane of the conveyor  12  used to measure bottle lean as further described below. 
     After the dynamic offset is calculated (or if no dynamic offset is calculated because the bottle was not bouncing when imaged), points  1 L and  1 R are located. Point  1 L is the point where the left edge  142  of the bottle image is found at a predetermined height 1y above the plane of the conveyor  12 . Point  1 R is the point where the right edge  144  of the bottle image is found at the same height 1y above the plane of the conveyor  12 . For purposes of example, the height 1y may be about 1.25 inches. 
     The location of the horizontal center  1 C of points  1 L and  1 R is then calculated as the point having a y location equal to 1y and an x location equal to: 
     
       
         ( 1   Lx+   1   Rx )/2 
       
     
     where  1 L x  is the location along the x-axis of point  1 L and  1 R x  is the location along the x-axis of point  1 R. 
     Next, points  2 L and  2 R are located. Point  2 L is the point where the left edge  142  of the bottle image is found at a predetermined height 2y above the plane of the conveyor  12 . Point  2 R is the point where the right edge  144  of the bottle image is found at the same height 2y above the plane of the conveyor  12 . For purposes of example, the height 2y may be about 6 inches. 
     The location of the horizontal center  2 C of points  2 L and  2 R is then calculated as the point having a y location equal to 2y and an x location equal to: 
     
       
         ( 2   Lx+   2   Rx )/2 
       
     
     where  2 L x  is the location along the x-axis of point  2 L and  2 R x  is the location along the x-axis of point  2 R. 
     The points  1 C x  and  2 C x  lie along the centerline AA of the bottle and, thus, together define the centerline AA. The measured lean is then calculated as the difference in horizontal location of the center points  1 C x  and  2 C x:   
     
       
           2   Cx − 1   Cx   
       
     
     Next, the dynamic offset, if any, is subtracted from the measured lean to arrive at the true bottle lean. Since the dynamic offset represents the lean attributable to the bottle&#39;s orientation on the conveyor, subtracting out this lean will result in the lean that is inherent in the bottle itself. 
     The above method is carried out for each of the imaging devices  102  and  104 . The bottle lean calculated for each imaging device is then combined to arrive at a combined true bottle lean as will now be described. 
     Imaging devices  102  and  104  are arranged such that their lines of sight  103  and  105 , respectively cross at right angles to one another, FIGS. 2 and 3. Since each imaging device can only measure lean perpendicular to its line of sight, this means that the lean measured by imaging device  102  will always be at a right angle to the lean measured by imaging device  104 . Since two right angle components of the true lean are known, the Pythagorean theorem can be used to calculate the combined true lean as: 
     
       
         ( L   1   2   +L   2   2 ) ½   
       
     
     where L 1  is the true lean calculated based on the image from first imaging device  102  and L 2  is the true lean calculated based on the image from second imaging device  104 . 
     The combined true bottle lean is then compared to the allowable specification. If the combined true lean exceeds the allowable lean, then the bottle is rejected by rejection device  68 . If, however, the combined true lean is within acceptable limits, the bottle is allowed to continue on the conveyor  12  toward the cold end  82  of the bottle production line. 
     The combined true lean information may be made available to the bottle production line operators even in cases where the lean is found to be within allowable limits. This allows the operators to observe and to react to any trend in the combined true lean measurements. Increasing lean, for example, may indicate that the bottle forming process is becoming too hot. An operator, observing such an increase, can take appropriate steps to lower the temperature of the bottle forming process before bottles having rejection level defects are formed. Such feedback of bottle lean information, thus, allows avoidance of potential rejects. Alternatively, a computer may be used to observe and automatically react to such trend information. 
     In addition to the dynamic offset described above, a static offset may also be subtracted from the measured lean to arrive at the true bottle lean. Static offset is the offset measured when an in-specification bottle is placed flat on the conveyor  12 , while the conveyor is not moving. Static offset accounts for errors in the hot bottle inspection system itself that do not change from bottle to bottle. For example, static offset may account for any mis-alignment between the imaging devices  102 ,  104  and the bottle conveyor  12 . 
     Static offset may also account for lens aberration. Each imaging device  102 ,  104  contains a lens as is well-known. All lenses display some degree of aberration, or distortion in some areas of the lens. Static offset accounts for such aberration. Subtracting the static offset in this manner also allows less expensive lenses to be employed. Less expensive lenses tend to exhibit more aberration than do more costly lenses. Since this aberration is static and predictable, however, using a static offset, as described above, allows less expensive lenses to be used while still ensuring that accurate bottle lean information can be obtained. 
     Although the bottle inspection method has been described with respect to obtaining two center points  1 C and  2 C, it is noted that a greater number of points can be evaluated if desired. If a greater number of points are used, the lean can be calculated by taking the average of the individual leans calculated between each of the points. Using a greater number of points also facilitates the detection of other bottle abnormalities such as bulges. If a bulge exists in the sidewall of a bottle, this will cause the center point at this location to be offset from the other center points thus indicating that a problem exists in this area. 
     In addition to bottle lean information, the procedure described above may also be used to measure actual bottle dimensions at various locations. Once the bottle lean is known, the true bottle width, e.g., may be calculated using trigonometry. An example of such a calculation is described below with respect to FIG.  6 . 
     For purposes of this example, the “lean angle” is the angle formed between the base  140  of the bottle and the conveyor  12 . The lean angle may be calculated using any number of trigonometric functions and the bottle measurement data which has been collected as previously described. The lean angle may, for example, be calculated as follows: 
     
       
         lean angle=tan −1 (( BLy−BRy )/( BLx−BRx )) 
       
     
     Once calculated, the lean angle may then be used to derive the true bottle dimensions from the measured image data. For example, the true bottle width at the point  1 L may be calculated as follows: 
     
       
         true width=cos(lean angle)×( 1   Lx−   1   Rx ) 
       
     
     Other true bottle dimensions may be calculated in a similar manner once the lean angle is known. 
     Correction for Longitudinal Misalignment 
     It has been found that the position of a bottle such as bottle  52  on conveyor  12  can vary from bottle to bottle. This is because, as bottles are placed onto the conveyor by the blow mold  30 , they are not always placed in exactly the same position on the conveyor. Accordingly, the position of a particular bottle can vary both in a transverse direction  114  (in a direction perpendicular to the direction of conveyor movement) and also in a longitudinal direction  116 , perpendicular to the transverse direction as shown in FIG.  2 . 
     Referring to FIG. 2, when a bottle  52  is perfectly aligned longitudinally, it will be located at the target site  52  when the strobe  94  is energized. In this case, the bottle  52  will be longitudinally equidistant from the imaging devices  102 ,  104 . When a bottle  52  varies in longitudinal direction  116 , however, it will either be downstream (in the direction of the arrow  14 ) or upstream (in the direction opposite the arrow  14 ) of the target site  50  when the strobe  94  is energized. If the bottle  52  is downstream, it will be closer to imaging device  104  and further from imaging device  102 . Conversely, if the bottle  52  is upstream, it will be closer to imaging device  102  and further from imaging device  104 . 
     When the bottle  52  is closer to one imaging device than the other, the image of the bottle acquired by the closer imaging device will be larger than the image of the bottle acquired by the further imaging device. When this condition is detected by the computer  66 , the bottle being imaged is longitudinally misaligned. By measuring the amount of difference in bottle image size, the computer  66  can determine the amount of longitudinal misalignment and correct the image size accordingly. 
     Correction for Transverse Misalignment 
     Referring to FIGS. 2 and 8, when a bottle  52  is perfectly aligned in a transverse direction  114 , it will be located at the target site  50  when the strobe  94  is energized. When a bottle  52  varies in transverse direction  114 , however, it will either be closer to, e.g., position  202 , or further from, e.g., position  200 , the imaging devices  102 ,  104 , FIG.  8 . 
     FIGS. 9A-11A schematically illustrate the image  194  acquired by the imaging device  104  which includes the bottle image  204 . FIGS. 9B-11B illustrate the image  192  acquired by the imaging device  102  which includes the bottle image  202 . To determine transverse location, the computer  66  combines the image  192  and the image  194  from the imaging devices  102 ,  104  into one image  206 , FIGS. 9C-11C. If the bottle  52  is perfectly aligned transversely, as shown in FIGS. 2 and 10, the image of the bottle acquired from each imaging device  102 ,  104  will overlap. The combined image will, thus result in only one bottle image as seen in FIG.  10 C. 
     If, however, the bottle  52  is transversely misaligned closer to the imaging devices  102 ,  104 , e.g. at the position  202 , FIG. 8, the bottle image  202  acquired by imaging device  102  will be shifted to the left (since the bottle has shifted to the left in the field of view of imaging device  102 ). This is best illustrated in FIG.  9 B. 
     In a similar manner, the bottle image  204  acquired by imaging device  104  will be shifted to the right (since the bottle has shifted to the right in the field of view of imaging device  104 ). This is best illustrated in FIG.  9 A. 
     In such a misaligned configuration, the combined image  206 , FIG. 9C will result in the individual bottle images  202 ,  204  not overlapping. In other words, the edges of the bottle images  202 ,  204  acquired from imaging devices  102 ,  104  will not overlap. Specifically, the bottle image  202  acquired by the imaging device  102  will be shifted to the left relative to the bottle image  204  acquired by the imaging device  104  as shown in FIG.  9 C. 
     If the bottle  52  is transversely misaligned further from the imaging devices  102 ,  104 , e.g., at the position  200 , FIG. 8, the bottle image  202  acquired by imaging device  102  will be shifted to the right (since the bottle has shifted to the right in the field of view of imaging device  102 ). This is best illustrated in FIG.  11 B. 
     In a similar manner, the bottle image  204  acquired by imaging device  104  will be shifted to the left (since the bottle has shifted to the left in the field of view of imaging device  104 ). This is best illustrated in FIG.  11 A. 
     In such a misaligned configuration, the combined image  206 , FIG. 11C will result in the individual bottle images  202 ,  204  not overlapping. In other words, the edges of the bottle images  202 ,  204  acquired from imaging devices  102 ,  104  will not overlap. Specifically, the bottle image  202  acquired by the imaging device  102  will be shifted to the right relative to the bottle image  204  acquired by the imaging device  104  as shown in FIG.  11 C. 
     Accordingly, the computer  66  can detect that a transverse misalignment condition exists and can determine in which direction the misalignment occurs. By measuring the distance between the bottle images  202 ,  204 , the computer  66  can also measure the amount of misalignment. Once the amount of misalignment is known, the computer  66  may align the images  202 ,  204  and adjust the size of the image to compensate for the transverse misalignment. In other words, if the computer  66  detects that the bottle  52  is transversely misaligned further from the imaging devices  102 ,  104 , e.g. at the position  200 , the combined bottle image may be enlarged in accordance with the amount of transverse misalignment. In a similar manner, if the computer  66  detects that the bottle  52  is transversely misaligned closer to the imaging devices  102 ,  104 , e.g. at the position  201 , the combined bottle image may be reduced in accordance with the amount of transverse misalignment. 
     Upon initial start-up of the inspection apparatus  64 , it may be calibrated by running bottles of known dimensions and characteristics through the inspection apparatus. The computer  64  can then correlate the actual size of these bottles to the size of their images generated by the inspection apparatus  64 . The computer  66  may then use this relationship to measure characteristics of unknown bottles as described above. 
     Although the above methods for correction of orientation and position have been described with respect to bottle inspection, these methods could be used for any inspection task in which the objects being inspected are not uniformly oriented and/or positioned. 
     Laser Trigger 
     As described previously, the computer  66 , FIG. 1, may detect pulses from the I.S. machine in order to determine when to energize the strobe light  94 ,  138  and  140 , FIGS. 2,  3  and  12 , and to correlate each bottle being imaged to the mold which created the bottle. As an alternative to using the I.S. machine pulses to determine when to energize the strobe light, a laser trigger device may, alternatively, be used as will now be described in detail. 
     Referring to FIG. 15, a laser device  510  may be located adjacent the conveyor  12  in the vicinity of the image generating device housings  100 ,  120  or  300  and  350 . It is noted that, for the sake of clarity, the housing(s) has been omitted from FIG.  15 . The laser device  510  may be located so as to direct a laser beam  512  across the top of the conveyor  12  and onto a reflector  514  located on the opposite side of the conveyor  12 . The height of the laser device  510  is set so that the laser beam  512  will be interrupted by a bottle  52  being transported by the conveyor  12  when the bottle passes between the laser device  510  and the reflector  514 . Both the laser device  510  and the reflector  514  may be mounted to the production facility floor  524  in any conventional manner. 
     When no bottle is located between the laser device  510  and the reflector  514 , the laser beam  512  is reflected by the reflector  514  back to a detector located on the laser device  510 . The detector is, thus, able to detect the reflected laser beam, indicating that no bottle is present in the target area. When a bottle passes between the laser device  510  and the reflector  514 , however, the laser beam  512  is blocked and the detector located on the laser device  510  is not able to detect the reflected laser beam, thus indicating that a bottle is located within the target area. 
     The laser device  510  may include a data connection  516  which connects with the computer  66  in a conventional manner. In this fashion, the laser device is able to signal the computer  66  when a bottle is within the target area and, thus, cause the strobe light or lights to fire, enabling an image of the bottle to be acquired in a manner as previously described. 
     It has been found that the laser triggering arrangement described above more accurately indicates when a bottle has entered the target area than does the I.S. machine pulse detection method previously described. It is noted that, even when using the laser triggering method, the I.S. machine pulses may still be monitored in order to provide correlation between the particular bottle being imaged and its mold of origin in the I.S. machine. 
     Laser device  510  may be a conventional laser triggering device, such as the type commercially available from The Allen Bradley Company of Milwaukee, Wis. and sold as Model No. SX 12L. 
     One problem with the laser triggering arrangement described above is that it is sometimes necessary for human operators to enter the area  518  between the conveyor  12  and the laser device  510 . Such entry into the area  518  often results in the human operator&#39;s body blocking the laser beam  512 . This, in turn, indicates to the detector in the laser device  510  that a bottle is in the target area and, thus, results in an erroneous signal being sent to the computer  66  via the data connection  516 . 
     FIG. 16 illustrates an improved laser trigger arrangement in which a human operator  520  standing in the area  518  will not interfere with the laser beam  512 . As can be seen from FIG. 16, the laser device  510  may be mounted at an elevated location such that the laser beam  512  will pass above an operator  520  standing near the conveyor  12  in the area  518  and the operator  520  will not cause interference with the laser beam  512 . To achieve this result, the laser device  510  is located and aimed such that the laser beam  512  forms a relatively steep angle “u” with respect to the plane of the upper surface  13  of the conveyor  12 . The laser device  510  may be located a vertical distance “q” of about 20.0 feet above the upper neck area  22  of the bottle  52 . With an exemplary bottle height “r” of about 9.0 inches, the laser device  510  will be located approximately 20 feet, 9 inches (“q” plus “r”) above the upper surface  13  of the conveyor  12 . With the upper surface  13  of the conveyor  12  located an exemplary distance “s” of about 3.0 feet above the floor  524 , the laser device  510  will be located about 23 feet, 9 inches (“q” plus “r” plus “s”) above the floor  524 . The laser device  510  may be located a horizontal distance “t” of about 15.0 feet from the centerline  526  of the conveyor. With the exemplary dimensions set forth above, the angle “u” formed between the laser beam  512  and the conveyor upper surface  13  will be about 60 degrees. The laser device may, for example, be mounted either directly or indirectly to the ceiling of the production facility. 
     As previously noted, the relatively steep angle “u” allows the laser beam  512  to intersect the upper portion  522  of a bottle in the target area while avoiding interference by a human operator  520  standing near the conveyor  12  adjacent the target area. The steep angle “u” also results in the reflector  514  being located below the plane of the conveyor upper surface  13 . This is advantageous since, located below the conveyor upper surface  13  in this manner, the reflector  514  is exposed to much less heat than it is when located above the conveyor upper surface  13  as shown in FIG.  15 . Preferably, the angle “u” should be from about 60 to about 70 degrees. 
     The reflector  514  may be located a horizontal distance “v” of about 10.0 inches from the conveyor centerline  526  and a vertical distance “w” of about 14.0 inches below the conveyor upper surface  13 . 
     Electronically Shuttered Imaging Device 
     The imaging apparatus and methods set forth previously have been described in conjunction with a strobe light or lights. Such strobe lights may be used in a conventional manner to “freeze” the moving target bottle and fix an image thereof on the applicable image generating device. Although strobe lights generally function well for this purpose, there are some disadvantages associated with the use of strobe lights. For example, flashing strobe lights are often found to be irritating to human operators in the area. Strobe lights create “electrical noise” which may interfere with computers and other electronic systems, such as the computer  66  previously described. Strobe lights also take up space near the bottle production line which might otherwise be used for other purposes. Finally, strobe lights represent relatively expensive, high maintenance items. 
     Strobe lights may be eliminated, and the disadvantages discussed above avoided, by utilizing an electronically shuttered imaging device. Such devices are commonly used to image moving objects. An electronically shuttered imaging device may be a CCD device, similar to the imaging devices  102 ,  104  previously described. An electronically shuttered imaging device, however, also includes electronic circuitry which enables the device to “freeze” an image of a moving target without using a strobe light. 
     Accordingly, in all of the apparatus and methods previously described, electronically shuttered imaging devices may be used in place of the imaging devices  102  and  104  and the previously described strobe lights may be eliminated. The electronically shuttered imaging device used may be of the type commercially available from Hitachi Benshi Ltd. of Tokyo, Japan and sold as Model No. KPf1. The electronically shuttered imaging devices may be triggered either by pulses from the I.S. machine or by the a laser trigger device, in a manner as previously described. In all other aspects, the electronically shuttered imaging device may operate in a similar manner to that previously described with respect to the imaging devices  102 ,  104 . 
     When using an electronically shuttered imaging device, although no strobe light is required, the bottle  52  being imaged must still be adequately illuminated. Although any conventional illumination source may generally be used, one specific and preferred type of illumination source will now be described in detail with reference to FIGS. 15 and 16. 
     FIGS. 15 and 16 illustrate a conventional bottle visual inspection station  530  of the type that is commonly used in bottle manufacturing plants. The station  530  generally includes a light source  532  which may be, for example, an AC powered halogen light source, and a reflector board  534 . Light from the light source  532  illuminates the bottles as they pass beneath the light source. This light is then reflected off of the bottles, allowing an operator  520  to visually inspect the bottles. Further, light from the light source is reflected by the reflector board  534  and passes through the walls of the bottles, allowing the operator  520  to view light which is transmitted through the bottles. 
     It has been found that the existing halogen light source  532 , described above, adequately illuminates the bottles, allowing the electronically shuttered image generating devices to acquire images of the bottles in a manner as previously described. This is advantageous since use of the existing light source eliminates the need to provide separate or additional light sources for the imaging system. It has been found, however, that the intensity of light provided by AC light sources, such as the halogen light source described above, tends to fluctuate over time. This fluctuation is believed to be due to the sinusoidal characteristic of the AC power supply. Although such fluctuation generally occurs at too high a frequency to permit detection by the human eye, it may readily be detected by a high-speed imaging device, such as the electronically shuttered imaging devices described above. 
     In order to reduce the effect on acquired images of the fluctuations described above, it has been found to be beneficial to operate the halogen light source at a wattage lower than its rated wattage. In one example, a 500 watt halogen bulb located in the light source  532  may be operated at about 300 watts. In order to accomplish this wattage reduction, the voltage supplied to the halogen bulb may be reduced accordingly. It has been found that operating the light source in this manner significantly reduces the effect of AC power induced light fluctuations. Accordingly, operating a conventional AC light source in this manner allows an existing AC-powered halogen light source to be used to acquire high quality images with an electronically shuttered imaging device. 
     While an illustrative and presently preferred embodiment of the invention has been described in detail herein, it is to be understood that the inventive concepts may be otherwise variously embodied and employed and that the appended claims are intended to be construed to include such variations except insofar as limited by the prior art.