GB2089973A - Detection of Defects in Objects - Google Patents

Abstract

An inspection device for an apparatus for and methods of inspecting objects, such as glass bottles for defects includes an interface circuit (18) receiving data signals, typically in digital series form from a photodiode camera (10) which scans the object, and includes a latch (50) for storing one of the digital signals, and a pair of adders (52, 64). Each data signal is compared to the preceding data signal from latch (50) in one of the adders (52, 64) to generate a difference signal. Each difference signal is compared with a selected stored threshold signal in the other adder to generate an event signal representing this difference. Processing means includes master control means (28) for alternately connecting control units (20, 22) to the interface means (18) whereby one unit receives a group of the event signals representing one object while the other is processing a preceding group. Event magnitudes are compared with predetermined values. The event signals are displayed as a two-dimensional representation of the unwrapped surface. <IMAGE>

Description

SPECIFICATION Improvements in and Relating to the Detection of Defects in Objects The present invention concerns apparatus for and a method of detecting defects in objects.

More particularly it relates to sidewall inspection devices for containers and in particular to methods and apparatus for adjusting an inspection device, for detecting defects using event proximity, and for extracting significant data with respect to defects from a sparse object, such as a glass bottle.

The use of optical scanning devices for inspecting the sidewalls of containers is well known. Numerous devices, such as those shown in U.S. Patent Specifications nos. 3,708,680 and 3,716,136, have circuitry including means for receiving and interpreting light passed through or directed onto an item under inspection. Such devices incorporate either a visual display or comparison of the item, or employ a device capable of producing a resistance proportional to the intensity of light directed thereon. Whether the output of such a device is visual or electrical in nature, it is eventually compared against a model or base reference to determine if the item under inspection is suitable as to size and construction and is without flaws, cracks, or foregin objects.

Such devices are each intended to provide an automated inspection means for checking, as in a moving column of bottles, single or multiple objects in that moving column.

U.S. Patent Specification No. 3,877,821 discloses an apparatus having a scanning array that is serially interrogated to generate a train of pulses having amplitudes representing the light transmitted through an object under inspection.

Adjacent pulses are compared to generate pulses having amplitudes which represent the difference in pulse amplitudes. The difference pulses can be utilized to indicate a defect in the object being inspected. U.S. Patent Specification No.

3,942,001 discloses an apparatus for detecting the presence of extraneous matter or cracks in translucent containers. A spot beam of light is projected through the container to generate an inspection signal which is compared with an acceptance signal. The acceptance signal amplitude is varied in accordance with the position of the spot beam with respect to the container.

U.S. Patent Specification No. 2,798,605 is representative of the prior art inspection circuits and utilizes a cathode ray tube to display the object being inspected. A scanning generator subassembly provides a vertical sweep circuit and a horizontal sweep circuit for the scanning element of a cathode ray presentation tube provided in a monitor unit. An iconoscope is provided for receiving a focussed image of the bottle under inspection. The monitor is arranged to receive the video output of a selected camera unit and is controlled in its electrostatic deflection circuits by the same sweep voltage waves employed in the deflection circuits of the selected camera unit, so that it reproduces the picture image focused on the iconoscope.

The present invention concerns a method of and apparatus for performing the setup of an inspection device for objects such as glass bottles and for displaying an output of the inspection device. A digitized video signal representing a point of inspection is generated by a photodiode camera. The digitized video signal is generated to an adder and to a latch in which is stored the digitized video signal from the previous points of inspection. A signal representing the difference between the present digitized signal from the adder and the previous digitized signal from the latch is generated and compared with a stored threshold level for the current point of inspection.

If the threshold level is exceeded, the difference signal is stored as an event signal.

According to the present invention then, an inspection device for an inspection apparatus which detects defects in objects and includes a source of a plurality of data signals representing the magnitude of the amount of light received from an associated point on the objects, comprises an interface circuit connected to the source of data signals, an apparatus for displaying an output of the inspection device, and a control circuit connected between the interface circuit and the display apparatus.

Also according to the present invention, a method for detecting defects in an object being inspected by an apparatus which has a source of data signals each representing the magnitude of the amount of light received from an associated point on the object, comprises the steps of generating an event signal for each one of the data signals representing the difference in magnitudes between said each one of the data signals and another one of the data signals, identifying a predetermined relationship between at least two ofsaid event signals, and indicating a defect in the object in response to an identification of said predetermined relationship.

When the entire object such as a bottle has been scanned, the stored information is generated to a means for displaying the stored signals on a video screen. The signals are displayed in a twodimensional representation of the surface of the inspected object, as if the object has been cut through one side and unwrapped for display. The stored signals include the location of each detected defect, thus enabling the display means to properly position the defect on the video screen relative to the representation of the unwrapped object. By utilizing the apparatus in this manner and varying the threshold levels, the operator can determine what the proper threshold levels should be for inspecting the particular object.

The apparatus can also be utilized to monitor the output of the inspection device. The latch is disabled, the threshold signal is cleared to zero, and only one vertical inspection sweep is made of the object. The data is then transferred to a means for displaying the signals as a two dimensional representation of the signal magnitude on one axis and the location of the point on the other axis. By utilizing the apparatus in this manner, the operator can adjust the sensitivity of the inspection device to the camera signals without using an oscilloscope or other external device.

The present invention also concerns an apparatus for extracting only the significant data from an optical inspection of a sparse object, such as a glass bottle. A digitized video signal representing a point of inspection is generated by a camera and associated light source to an interface circuit including an adder and a latch in which is stored the digitized video signal from the previous point of inspection. A signal representing the difference between the present digitized signal and the stored digitized signal from the latch is generated by the adder and compared with a stored threshold level for the current point of inspection. If the threshold level is exceeded, an event signal is generated and stored in the interface circuit.

After the object has been scanned, the group of event signals is processed to determine if a defect is present A master control unit means alternately connects a pair of control units to the interface, whereby one of the control units is receiving a group of event signals while the other control unit is processing a preceding group of event signals.

The present invention further concerns an apparatus and method for extracting data from a scan of a glass container and utilizing the extracted data to determine the physical size and intensity of localized defects to ascertain the acceptability of the container. A photodiode array and light source are utilized to generate signals representing the amount of light received from points on the container. Event signals are generated when the magnitudes of adjacent diode signals are different by an amount which exceeds a threshold level. The event signal magnitude and position are stored in an inspection device interface and transferred to either a first or second control unit, both of which are responsive to the event signals for determining whether to generate a reject signal.

A master control means alternatively connects one of the first and second control units to the interface, whereby the connected control unit receives the event signals from the interface while the other control unit determines whether to generate a reject signal by processing the event signals of a preceding container. In making this determination, each event along a vertical sweep is checked to see if it can be linked to a preceding event by not exceeding a user-specified separation between the associated points on the container. A string is formed when two or more events are in proximity to each other. The apparatus checks for excess string magnitudes as one basis for bottle rejection. If a bottle is not rejected on a string, the strings are checked to see if they form a blob. A blob is a plurality of strings in proximity to each other.If there is no blob rejection, a final check is made to see if the number of events forming the blob is sufficient to exceed a small defect threshold.

The invention will now be further described by way of example, with reference to the accompanying drawings, in which: Figure 1 is a block diagram of an apparatus for detecting defects in objects according to the present invention; and Figure 2 is a block diagram of the inspection device interface of the apparatus for detecting defects of Figure 1.

Referring now to the drawings, there is illustrated in Figure 1 a block diagram of an apparatus for detecting defects in objects according to the present invention. An object, such as glass bottle (not shown), is scanned by a camera 10. The camera 10 generates a plurality of signals proportional in magnitude to the amount of light received from the glass bottle. In the preferred embodiment of the invention, a light source (not shown) directs a beam of light through the glass bottle under inspection and into the camera 10. The camera 10 includes a plurality of photosensitive devices, such as photodiodes, which are vertically arranged in a linear array. It has been found that a linear array of two hundred and fifty-six photodiodes yields satisfactory results. The photodiode is a variable resistance device that will pass a voltage proportional to the amount of light falling thereon.Each photodiode receives light which has passed through different segments or portions of the bottle under inspection. If a flaw, crack, or foreign object is contained in the bottle, then the light passing through that portion of the bottle will be partially blocked or reflected and the corresponding photodiode will register a lesser intensity of light than had no defect been present.

The signals from the photodiodes of the camera 10 are supplied to a sampler 14 on a plurality of lines 12. Each of the photodiodes is sampled in sequential order, producing a series of pixel signals on a line 1 6 which represent the amount of light which passed through the bottle under inspection along one vertical sequential sweep of the photodiodes. The sampler 14 is a device well known in the art. By rotating the bottle under inspection relative to the camera 10, a plurality of different sweeps can be made, each sweep inspecting a different portion of the bottle.

It has been found that about three hundred and seventy-five to four hundred sweeps will sufficiently cover an average bottle and ensure an accurate inspection. Thus, the sampler 14 generates a plurality of series of pixel signals on line 1 6 representing the amount of light passing through the inspected portions of the entire bottle.

The pixel signals from the sampler 14 on line 1 6 are an input to an inspection device interface 1 8. The interface 1 8 rapidly extracts significant data from the sparse object, such as the glass bottle, in a manner suitable for computer analysis.

When a bottle is ready to be scanned, the interface 1 8 is enabled to receive and store data concerning that bottle. When no bottle is ready to be scanned, the interface 1 8 stores the data concerning the last scanned bottle until a new bottle is ready to be scanned. The operation of the interface 1 8 is more fully explained below.

The interface 1 8 is a means for generating groups of signals representing the characteristics of the bottle under inspection. The output of the interface 1 8 is fed to a control circuit for generating a reject signal whenever a defective bottle is detected. The control circuit includes a first control unit 20 and a second control unit 22, which receive the output signals from the interface 1 8 over lines 24 and 26 respectively.

The first control unit 20 and the second control unit 22 are each responsive to the groups of signals representing the characteristics of the bottles under inspection for determining whether to generate a reject signal.

The first control unit 20 and the second control unit 22 are connected to a master control unit or processor 28 by lines 30 and 32 respectively. The master processor 28 also provides inputs to the interface 18 over a plurality of lines 34 to allow an operator to set certain tolerance limits, as will be more fully described below. The master processor 28 alternately connects one of the first and second control units 20 and 22 to the interface 1 8 to receive groups of signals representing the characteristics of a bottle while the other of the first and second control units 20 and 22 determines whether to generate a reject signal based upon the plurality of signals representing the characteristics of a preceding bottle.Thus, while the first control unit 20 is reading data from the inspection interface 18 concerning a bottle which has just been scanned, the second control unit 22 is processing data obtained in a prior scan to determine whether to generate a reject signal for the preceding bottle.

The master processor 28, the first control unit 20, and the second control unit 22 can all be microprocessors, such as a model 6800 manufactured by Motorola which is conventional and well known in the art. The master processor 28 has an input device 36 by which an operator can program the system and set various tolerance parameters. The input device 36 is connected to the master processor 28 by a line 38. The master processor 28 is also connected by a line 40 to an output device 42, such as a video display, so as to permit an operator to monitor or calibrate the system. Alternatively, the device 42 can be a means responsive to a reject signal generated by the master processor 28 for rejecting a particular bottle which has been determined to be defective.

A further input to the master processor 28 is a gauge 44. The gauge 44 is provided to generate a signal on a line 46 when a bottle is in the proper position to be scanned.

The interface 1 8 can receive data so long as the gauge 44 signals that a bottle is in the proper scanning position. When the gauge 44 ceases to generate such a signal, as during the period when the inspected bottle is removed and an uninspected bottle is moved in, the collected information is stored in the interface 1 8. The master processor 28 prevents interference between the first and second control units 20 and 22 by selecting one of the units to receive the data held in the interface 18. When all of the data has been transferred to the first control unit 20, for example, the interface 1 8 is free to receive new data on the next bottle as soon as the signal from the gauge 44 is restored. The first control unit 20 processes the data in order to determine whether to generate a reject signal.When scanning is completed on the next bottle and the gauge 44 ceases to generate its signal, the accummulated data is stored in the interface 1 8.

The master processor 28 then selects the second control unit 22 to receive the data while the first control unit 20 continues to process the original information. Thus, each of the control units 20 and 22 has two full cycles of the gauge 44 to process the data concerning each bottle to determine whether or not to generate a reject signal. By providing parallel processing paths, the control circuit increases the speed and efficiency of the inspection apparatus.

Referring now to Figure 2, there is illustrated a block diagram of the details of the inspection device interface 1 8. The interface 18 is a means for rapidly extracting significant data from a sparse object, such as a glass bottle, in a manner suitable for computer analysis. The sampler 14 (of Fig. 1) can generate digital signals, or analog signals to an analog-to-digital converter, representing the magnitude of the light received by the camera 10 (also Fig. 1). Line 16 presents the plurality of signals to an event detector 48 including a data latch 50 and an adder 52. The latch is a means for storing one of the plurality of signals. In the illustrated embodiment, the preceding pixel signal is stored in the latch 50 and is presented to the complementary input of adder 52.Thus, the adder 52 is a means for generating a signal which represents the difference between the magnitude of the stored preceding pixel signal in the latch 50 and the successive pixel signal presented on line 1 6. The output of the adder 52 is a signal representing the difference in the magnitudes of adjacent pixel signals. When the difference signal is generated by adder 52, the present pixel signal is stored in latch 50 to be compared with the next pixel signal. A control logic unit 54 of the interface 1 8 generates a command over a LATCH NEXT PIXEL line to cause the latch 50 to store the present pixel signal available on line 16. The contents of the latch 50 can be cleared to zero by a command from the master processor 28 (Fig. 1) over a CLEAR L line.

The difference signal from the adder 52 can be either positive or negative, depending upon the magnitudes of the present and previous pixel signals. Because only the magnitude of the difference between adjacent pixel signals is relevant in the detection of defects, it is convenient to feed the difference signal to a means for generating the absolute magnitude of the difference signal. As illustrated, the output from adder 52 is fed to an absolute magnitude circuit 56. The circuit 56 can be constructed of a plurality of exclusive OR gates, as is well known in the art. The CARRY output of adder 52 controls the absolute magnitude circuit 56 such that the outputs is always positive. Rectification of the difference signal prevents misleading comparison readings in the event detector 48.

The event detector 48 includes a means for storing a threshold signal. In the preferred embodiment, a threshold random access memory (RAM) 58 is provided for storing a plurality of threshold signals. Each threshold signal stored in the threshold RAM 58 corresponds to a specific pixel difference signal generated by the adder 52.

The means for selecting the individual threshold signal from the threshold RAM 58 which corresponds to the present difference signal is a diode counter 60. The diode counter 60 can be cleared to zero by a command from the control logic 54 over a CLEAR DC line and can be incremented by a command over an INCREMENT DC line. The diode counter 60 provides the threshold RAM 58 with the memory address of the proper threshold signal. The desired threshold signals can be loaded into the threshold RAM 58 from the master processor 28 (Fig. 1) over a LOAD DATA line. The output of the diode counter 60 is also connected to an internal data bus 62.

The signal from the threshold RAM 58 is presented to the complementary input of an adder 64 where it is combined with the signal from the absolute magnitude circuit 56. The adder 64 is a means for generating event signals when the difference signal obtained from the absolute magnitude circuit 56 differs from the threshold signal obtained from the threshold RAM 58. Event signals are generated, over an EVENT line to the control logic 54, indicating the detection of a defect, and over a MAGNITUDE line to the internal data bus 62, indicating by how much the difference signal differed from the threshold signal.

Upon receiving a signal from the gauge 44 (Fig.

1) that a bottle is ready to be scanned, the master processor 28 generates a signal over a GAUGE line to the control logic 54. In response to that signal, the control logic 54 generates a signal over a CLEAR SC line to a sweep counter 66. The contents of the sweep counter 66 are thus cleared to zero before each bottle is scanned. The output of the sweep counter 66 is connected to the internal data bus 62.

To initiate a sweep, the master processor 28 generates a signal over a start sweep line to the control logic 54. In response to that signal, the control logic 54 increments the sweep counter 66 by generating a signal over an INCREMENT SC line. The control logic 54 also clears the contents of the diode counter 60 by generating a signal over the CLEAR DC line. The control logic 54 further generates a signal over a CLEAR EC line to clear an event counter 68. These three initialization functions prepare the interface 1 8 for the receipt of data. The output of the event counter 68 is connected to the internal data bus 62. The event counter 68 generates a signal on an overflow line to the data bus 62 when the contents of the register exceed its limits.The event counter 68 is incremented by the control logic 54 over an INCREMENT EC line each time that the event detector 48 signals that an event has occurred.

The interface 1 8 includes a means for storing the event signals. An interface random access memory (RAM) 70 is provided for reading and storing the signals available on the data bus 62.

The first control unit 20 and the second control unit 22 (Fig. 1) alternatively read the accumulated data from the interface RAM 70 through the data bus 62 and lines 24 and 26 respectively. Data is stored in the interface RAM 70 when the control logic 54 generates a signal over a WRITE line. The interface RAM 70 also generates a signal on an OVERFLOW line to the data bus 62 when the contents of the register exceed its limits. A RAM counter 72 provides the interface RAM 'iO with memory address locations. The RAM counter 72 can be cleared to zero by a command from the control logic 54 over a CLEAR RC line and can be incremented by the control logic 54 by a command over an INCREMENT RC line.

The interface 1 8 also includes a means for defining a range for extracting data. In the illustrated embodiment, a window generator 74 is provided to limit the number of sweeps over which data can be extracted. A lower sweep limit is entered by an operator through the input device 36 (Fig. 1) to the master processor 28. The instruction is sent over a LO SET line to a low sweep comparator 76. The output of the sweep counter 66 is also an input to the low sweep comparator 76. When the number in the sweep counter 66 equals or exceeds the number generated over the LO SET line, the low sweep comparator 76 generates a signal over a SET line to a flip-flop 78. The flip-flop 78 generates a signal over an ENABLE line to the control logic 54, instructing it to process the incoming data.

Signals received by the interface 1 8 on sweeps taken of a bottle below the lower sweep limit are ignored to prevent erroneous data associated with the initial sweeps from being processed.

Similarly, the operator can enter a high sweep limit value to cause the interface 18 to stop processing data after a certain number of sweeps.

The master processor 28 sends the instruction over a HI SET line to a high sweep comparator 80.

The output of the sweep counter 66 is also an input to the high sweep comparator 80. When the number in the sweep counter 66 equals or exceeds the number generated over the HI SET line, the high sweep comparator 80 generates a signal over a RESET line to the flip-flop 78. The flip-flop 78 thus ceases to generate the signal over the ENABLE line, causing the control logic 54 to ignore all subsequent data.

Prior to utilizing the apparatus for detecting defects, the operator will enter the parameters under which the machine will operate through the input device 36. The parameters include the low and high sweep limits and the group of threshold signals. The low and high sweep limits define the sweep window, which is the range of sweeps over which data can be accepted by the interface 1 8.

By selecting a particular set of threshold signals to be loaded into the threshold RAM 58, the operator determines the acceptable tolerances of light deviation which will cause an event to be detected. The master processor 28 loads the appropriate data into the interface 1 8.

When a bottle has been moved into a proper position for scanning, the gauge 44 generates a signal to the master processor 28. The signal is relayed along the GAUGE line to the control logic 54, which generates signals to clear the contents of both the sweep counter 66 and the RAM counter 72. These tasks are performed each time a new bottle is ready to be inspected. The interface 1 8 is then prepared to receive data from the camera 10.

At the beginning of each sweep, the master processor 28 generates a signal over the START SWEEP line to the control logic 54. The control logic 54 generates appropriate signals to clear the contents of the diode counter 60, clear the contents of the event counter 68, and increment the contents of the sweep counter 66. These tasks are performed at the beginning of each sweep made by the sampler 14.

The incoming pixel signals are fed to the adder 52 and the latch 50. The latch 50 holds the previous pixel signal at its output, which is then fed to the complementary input of the adder 52.

Thus, the output of the adder 52 represents the difference between the two adjacent pixel signals.

The output of the adder 52 is fed to the absolute magnitude circuit 56, which ensures that the input to adder 64 is always a positive signal.

The threshold RAM 58 holds the programmed plurality of threshold signals, each of which corresponds to a specific difference signal representing a pair of pixels. Since each pixel signal represents a sampled photodiode in the camera 10, the diode counter 60 can be incremented with each incoming pixel signal to select the memory address of the appropriate threshold signal stored in the threshold RAM 58.

That particular threshold signal is fed to the complementary input of adder 64 to be compared with the actual difference signal generated by adder 52 and rectified by the absolute magnitude circuit 56. The output of adder 64 is a plurality of event signals which represent a comparison between the difference signal and the threshold signal. When the magnitude of the difference signal exceeds a predetermined amount, the adder 64 will generate an event signal over the EVENT line to the control logic 54. The magnitude of the event signal as well as the output of the diode counter are gated onto the data bus 62 for storage in the interface RAM 70.

When an event is detected during the sweep window, as defined by the operator using the window generator 74, the control logic 54 generates signals which increment the event counter 68 and increment the RAM counter 72.

The control logic 54 also generates a signal over the WRITE line to the interface RAM 70 to read and store the contents of the diode counter 60 and the magnitude of the output adder 64. This process is repeated with each pair of adjacent pixel signals until a sweep is completed. The signal on the START SWEEP line is removed at the end of each sweep, causing the contents of the sweep counter 66 and the event counter 68 to be written into the interface ram 70 if one or more events have occurred in that particular sweep. Thus, in each sweep where an event is detected, the gathered data includes a series of events denoted by diode number and event magnitude, followed by a final single entry consisting of the sweep number and the numberof events which occurred in that sweep.

When the next sweep of the same bottle begins, the contents of the diode counter 60 are cleared to zero, the contents of the event counter 68 are cleared to zero, and the sweep counter 66 is again incremented. The scanning continues until the window generator 74 disables the interface 18 when the high sweep limit has been reached.

The groups of signals stored in the interface RAM 70 which represent the characteristics of the inspected bottle are then fed to either the first control unit 20 or the second control unit 22, as determined by the master processor 28. The data in the interface RAM 70 is down-loaded into the selected control unit, which determines whether or not to generate a reject signal for that particular bottle. Two checks are made before processing begins to make sure that the interface 1 8 has not overflowed because of an unusually bad bottle. These checks are indicated by status flags on the event counter 68 and the interface RAM 70. If the contents of either unit exceeds the capability of the register, a signal is generated over the respective OVERFLOW lines. When either overflow signal is present, the bottle will be immediately rejected because of a gross defect.

As stated above, the format of the data which is read by the selected control unit includes a series of diode numbers and associated event magnitudes, followed by a sweep number and a number of events. The bottle data is downloaded from the interface RAM 70 to the particular control unit. By checking each event along a sweep to see if it can be linked to a preceding event, the control units 20 or 22 can generate a string. A string is defined as a collection of one or more events in proximity to each other and having four properties which are calculated during generation. These properties include: the beginning of the string, which is the first diode number; the end of the string, which is the last diode number; the magnitude of each string, which is the sum of the magnitudes of each event comprising the string; and the number of events that formed the string.Checking for excess string magnitude occurs during string generation and the decision process will halt if a string magnitude exceeds a user-adjustable threshold. In other words, the selected control unit 20 or 22 links together events within a single sweep to determine if the sum of the magnitudes of the events exceeds a user-specified tolerance. If so, a reject signal is generated and the particular bottle will be removed.

If string checking does not reject the bottle, another processing stage is entered wherein the strings are checked to see if they form blobs. A blob is defined as collection of strings in proximity to each other. The string diode numbers must overlap, or at most be within a user-specified range, for the end of one string on one sweep and the beginning of another string on a different sweep. A blob has three properties which are calculated during formation. These properties include blob width, blob magnitude, and the number of events in the blob. During blob formation, blob width and blob magnitude are checked against user-specified tolerances and processing stops if either threshold is exceeded. If a bottle is not rejected because of blob width or blob magnitude, the number of events contained in the blob is compared to another user-specified number.If the number of events exceeds the specified tolerance, the bottle will also be rejected. If the bottle has not been rejected for any of the above reasons, it is considered a good bottle and no reject signal will be generated.

The apparatus for detecting defects can also be utilized to generate and display a picture of the object under inspection. A bottle is inspected under the normal procedure described above and data is stored in the interface RAM 70. When the bottle has been completely scanned, the master processor 28 instructs either the first control unit 20 or the second control unit 22 to receive the data from the inspection interface 18. The selected control unit 20 or 22 does not process the received information but rather transmits the data in raw form to the master processor 28. The gathered data includes the diode number, the sweep number, and the event magnitude for each event detected by the interface 18. The data is then presented to the output device 42, which can include a two-dimensional graphic module and a video screen.The graphic module and video screen are well known in the art. The data can be displayed in a two-dimensional graphic form, utilizing the sweep number of each event as the horizontal component and the diode number of each event as the vertical component. The video screen will display a dot at each sweep and diode number location where an event was detected.

The resuit is a two-dimensional representation of the inspected bottle showing all of the detected defects, as if the bottle had been cut through one side and unwrapped for display. The event magnitude may be used in conjunction with a synthetic threshold level which can be varied to generate new pictures which show the effect that different threshold levels have. Using the apparatus in this mode, an operator is aided in determining what the appropriate threshold levels for the particular style of bottle should be.

Although the preferred embodiment of the invention provides only a two-dimensional representation of the object under inspection, it will be appreciated that a three-dimensional representation could be generated on the video screen by the use of additional circuitry. Such circuitry is also well known in the art.

The apparatus for detecting defects can also be utilized to monitor the video output of the line scan camera. Such a use permits an operator to calibrate the interface 1 8 without requiring the use of an oscilloscope. When the apparatus is operated in this mode, the master processor 28 continuously clears the contents of the latch 50 to zero by generating a signal over the CLEAR L line.

With the latch 50 cleared, the plurality of pixel signals on lines 1 6 from the sampler 14 pass through the adder 52 unaltered. The master processor 28 also utilizes the LOAD DATA line to load the threshold RAM 58 with all zeros. Thus, every pixel signal is detected as an event and is stored in the interface RAM 70. Since the interface RAM 70 is limited in size, only one sweep of the bottle is taken to prevent memory overflow. The master processor 28 selects either the first control unit 20 or the second control unit 22 to receive the data from the interface RAM 70.

Each event can be stored in the second control unit 22 to receive the data from the interface RAM 70. The data includes the diode number and event magnitude for each pixel of the sweep. The data is transferred from the selected control unit 20 or 22 to the master processor 28. The master processor 28 relays the information to the output device 42, which again can consist of a twodimensional graphic module and a video screen.

The graphic module can utilize the diode number as the horizontal component and the event magnitude as the vertical component. The graph which is thus displayed on the video screen represents the amount of light received by the photodiodes over a single sweep. The procedure can be repeated continuously to simulate an oscilloscope. However, unlike an oscilloscope, no sweep or gain adjustments are necessary since the data is always properly scaled to a specific diode number or event magnitude. Operation of the apparatus in this mode permits an operator to make sensitivity adjustments relating to the event magnitude voltage without requiring the use of an oscilloscope.

It will be understood that the invention may be practiced otherwise than as specifically illustrated and described without departing from the scope of the appended claims.

Claims (43)

Claims

1. An inspection device for an inspection apparatus which detects defects in objects and includes a source of a plurality of data signals representing the magnitude of the amount of light received from an associated point on the objects, the inspection device comprising an interface circuit connected to the source of data signals, an apparatus for displaying an output of the inspection device, and a control circuit connected between the interface circuit and the display apparatus.

2. An inspection device as claimed in claim 1, wherein the interface circuit includes data storage means for storing the data signals as digital signals, difference signal means connected to the data storage means for generating for each one of the digital signals a signal representing the difference in magnitudes between one said digital signal and a preceding one, threshold storage means for storing a plurality of threshold signals, comparison means connected to the threshold storage means and to the difference signal means for comparing each of said difference signals with an associated one of the stored threshold signals and generating an event signal when the difference signal magnitude differs from the associated threshold signal magnitude, and event storage means connected to the comparison means for storing the event signals.

3. An inspection device as claimed in claim 2, wherein the difference signal means includes means for generating the difference signal as the absolute magnitude of the difference in signal magnitude.

4. An inspection device as claimed in claim 2 or 3, wherein the data storage means includes a latch for storing said preceding one of the digital signals.

5. An inspection device as claimed in claim 2, 3 or 4, wherein the difference signal means includes an adder having one input connected to the source of digital signals and a complementary input connected to an output of the data storage means for generating said difference signal.

6. An inspection device as claimed in any one of claims 2 to 5, wherein the threshold storage means includes a random access memory.

7. An inspection device as claimed in any one of claims 2 to 6, including selection means connected to said threshold storage means for selecting said associated one of said stored threshold signals.

8. An inspection device as claimed in any one of claims 2 to 7, wherein the comparison means includes an adder having one input connected to an output of said difference signal means and a complementary input connected to an output of said threshold storage means for generating said event signal.

9. An inspection device as claimed in any one of claims 2 to 8, wherein the event storage means includes a random access memory.

10. An inspection device as claimed in claim 1, including threshold signal means for generating a threshold signal, event signal means connected to the threshold signal means for generating an event signal when the difference in the magnitudes represented by pairs of the data signals representing adjacent points on the object differs from the magnitude of said threshold signal, and event display means connected to the event signal means for displaying the event signal as the output of the inspection device in a twodimensional visual representation of the surface of the inspected object.

11. An inspection device as claimed in claim 1, including event signal means connected to the data signals source for generating an event signal representing the difference in characteristics between said each data signal as a first one of the data signals and a second one of the data signals, identifying signal means connected to the event signal means for generating a signal identifying each of said event signals with respect to the associated said first one of the data signals, and storage means connected to the event signal means and to the identifying signal means for storing the event signals and the identifying signals.

1 2. An inspection device as claimed in claim 11, wherein the data signals source includes a photodiode array, each photodiode generating one of the data signals and wherein the event signals means is connected to the photodiode array and compares a pair of the data signals from adjacent ones of the photodiodes to generate each one of the event signals.

1 3. An inspection device as claimed in claim 11 or 12, wherein the storage means includes a random access memory.

14. An inspection device as claimed in claim 11, 12 or 13, wherein the event signal means generates an event signal representing the difference in magnitudes between said each one data signals and another one of the data signals, and including processing means connected to the event signal means for summing the magnitudes of the event signals and comparing the sum of the magnitudes with a predetermined value to detect a defect.

15. An inspection device as claimed in claim 14, wherein the processing means includes means for counting the number of the event signals generated and comparing the count with a predetermined value to detect a defect.

1 6. An inspection device as claimed in claim 14 of 15, including random access memory means connected between the event signals means and the processing means for receiving and storing the event signals and the identifying signals and for transmitting the event and identifying signals to the processing means.

1 7. An inspection device as claimed in claim 16, including reject signal means connected to the random access memory means for generating a reject signal for the object when the storage capacity of the random access memory means is exceeded.

1 8. An inspection device as claimed in any one of claims 14 to 1 7, wherein the plurality of data signals includes sweep groups of the data signals, each sweep group representing the data signals from an associated portion of the object, and the control circuit includes means for counting said sweep groups of the data signals.

1 9. An inspection device as claimed in claim 18, wherein the groups of data signals are generated in series and the control circuit includes selecting means for selecting one or more of those groups for processing by said processing means, said selecting means including a low sweep comparator means for selecting one of said groups in said series as the group at which said processing will begin, and a high sweep comparator means for selecting one of said groups in said series as the group at which said processing will end.

20. An inspection device as claimed in any one of the claims 14 to 19, wherein processing means includes counter means for counting a number of said event signals representing associated points on the object having a predetermined spatial relationship, and reject signal means for generating a reject signal for the object when said number of said event signals exceeds a predetermined value.

21. An inspection device as claimed in any one of claims 1 to 20, wherein the interface circuit generates the data signals as digital signals each representing the magnitude of the amount of light received from an associated point on an associated point on an object under inspection, and the control circuit includes event signal means connected to the data signals source and responsive to the digital signals for generating an event signal for each one of the digital signals representing the difference in the amounts of light represented by said each one of the digital signals and another one of the digital signals, and indicating means connected to the event signal means and responsive to the event signals for indicating a defect in the object in response to the identification of a predetermined relationship between at least two of said signals.

22. An inspection device as claimed in claim 21, including means for generating, a signal to said indicating means identifying each of said event signals with respect to the associated point of said corresponding one of the digital signals, and wherein the indicating means includes counter means for counting a number of said event signals representing associated points on the object having a predetermined spatial relationship, wherein said event signals represent points along a line on the object, and said indicating means includes identifying means responsive to said event signals for identifying a string of said event signals in proximity, and wherein the indicating means includes summing means for summing the magnitudes of said event signals in said string and comparing said sum to a predetermined value to identify a defect in the object.

23. An inspection device as claimed in claim 22, wherein the event signals represent points along a plurality of lines on the object and the indicating means includes identifying means responsive to said event signals and associated ones of said identifying signals for identifying a string of said event signals in proximity as a defect and for identifying a plurality of said strings in proximity as a defect in the object, and summing means for summing the magnitudes of said event signals in said strings and comparing said sum to a predetermined value to identify a defect in the object.

24. An inspection device as claimed in claim 1, wherein the interface circuit connected to the signal source selects pairs of the data signals and generates an event signal for each of said pairs of the data signals wherein the difference in the magnitudes of the data signals exceeds a predetermined threshold value; and including a pair of control units, each control unit processing a group of the event signals associated with one of the objects being inspected and for generating a reject signal when a defect is detected, and a master control connected to the control units for alternately connecting an input of each of said control units to the interface whereby one of the control units is loading a group of the event signals from the interface while the other is processing a preceding group of the event signals.

25. An inspection device as claimed in claim 24, wherein the source of the data signals generates the data signals as a series of digital signals and wherein the interface circuit includes a latch means for storing one of said digital signals, first comparing means for comparing one of said digital signals with a preceding one of said digital signals stored in said latch means to generate a difference signal representing the difference in magnitudes of said digital signals, threshold storage means for storing a plurality of threshold signals, and second comparing means connected to said first comparing means and said threshold storage means for comparing an associated one of said stored threshold signals with each of said difference signals to generate one of said event signals when the magnitude of said difference signal exceeds the magnitude of said associated threshold signal.

26. An inspection device as claimed in claim 1, including data storage means for storing the data signals, difference signal means connected to the data signal means for generating signals representing the difference in the magnitudes between each of said data signals and a preceding one of the data signals threshold signal means for storing a plurality of threshold signals, event signal means connected to said difference signal means and said threshold signals means for generating an event signal for each of said difference signals which differs from one of said threshold signals, and display means connected to said event signal means for displaying said event signals as a two-dimensional visual representation of the surface of the object being inspected.

27. An inspection device as claimed in claim 26, including disabling means for disabling said data storage means and wherein said threshold signals have a zero magnitude, whereby the data signals pass through said difference signal means and said event signal means to be displayed by said display means, and wherein said display means displays the data signals with respect to a pair of orthogonal axes, one of said axes representing the magnitude of the data signals and the other one of said axes representing the locations of the associated inspection points along one axis of the object.

28. A method for detecting defects in an object being inspected by an apparatus which has a source of data signals each representing the magnitude of the amount of light received from an associated point on the object, comprising the steps of generating an event signal for each one of the data signals representing the difference in magnitudes between said each one of the data signals and another one of the data signals, identifying a predetermined relationship between at least two of said event signals, and indicating a defect in the object in response to an identification of said predetermined relationship.

29. A method as claimed in claim 28, wherein the event signals each have a magnitude representing said difference in magnitudes and the identification is performed by summing said magnitudes of said event signals and comparing said sum with a predetermined value to identify a predetermined relationship.

30. A method as claimed in claim 28, wherein the identification is performed by counting said event signals and comparing the count with a predetermined value to identify a predetermined relationship.

31. A method as claimed in claim 28, wherein said event signals represent points along a line on the object, said event signals each have a magnitude representing said difference in magnitudes, and the identification is performed by summing the magnitudes of said event signals in proximity and comparing said sum with a predetermined value to identify a predetermined relationship.

32. A method as claimed in claim 31, wherein the identification also includes counting said event signals in proximity and comparing said count with a predetermined value to identify a predetermined relationship.

33. A method as claimed in claim 28, wherein said event signals represent points along a plurality of lines on the object, said event signals each have a magnitude representing said difference in magnitudes, and the identification is performed by summing the magnitudes of strings of said event signals in proximity along said lines and comparing said sum with a predetermined value to identify a predetermined relationship.

34. A method as claimed in claim 33, wherein the identification also includes counting said event signals in said strings and comparing said count withna predetermined value to identify a predetermined relationship.

35. A method as claimed in claim 28, wherein said event signal represents points along a plurality of lines on the object, and the identification is performed by identifying strings of said event signals in proximity along said lines, counting said lines having said strings in proximity to form a blob, and comparing said count with a predetermined value to identify a predetermined relationship.

36. A method as claimed in claim 28, wherein said data signals are digital signals, each representing the magnitude of the amount of light received from an associated point on the object, wherein the generation of an event signal is performed by storing a plurality of threshold signals, generating for each one of the digital signals a signal representing the difference in magnitudes between said one digital signal and a preceding one of the digital signals, comparing each of said difference signals with an associated one of said threshold signals, and generating an event signal when said difference signal magnitude differs from said associated threshold signal magnitude, and storing the event signal.

37. A method as claimed in claim 28, including extracting from the data signals significant data representing defects and storing said significant data as groups representing said event signals for an associated object, loading alternate ones of said groups of event signals into each of a pair of control units, and enabling said control units to process said stored groups in sequence whereby one of said control units is being loaded with one of said stored groups while the other one of said control units is processing a preceding one of said stored groups.

38. A method as claimed in claim 37, wherein the data signals are generated in sequence and the extracting step includes the steps of generating for each one of the data signals a signal representing the difference in magnitudes between the one data signal and a preceding one of the data signals, storing a plurality of threshold signals, and comparing each of said difference signals with an associated one of said threshold signals and generating one of said event signals when said difference signal magnitude differs from said associated threshold signal magnitude.

39. A method as claimed in claim 37 or 38, including a step of generating a reject signal in response to the processing of a predetermined number of said event signals in one of said groups.

40. A method as claimed in claim 28, wherein the generation of event signals is performed by comparing the magnitude represented by each of the data signals with the magnitude represented by one of the data signals representing an adjacent point on the object, and generating an event signal when the difference in the magnitudes resulting from each of said comparisons differs from the magnitude of a threshold signal; and the indication of a defect is performed by displaying said event signals as a two-dimensional representation of the surface of the object.

41. A method as claimed in claim 40, wherein the generation of event signals further includes storing a plurality of threshold signals each associated with one of the inspection points on the object and comparing each of the differences in the magnitudes with the magnitude of the one of said threshold signals associated with the inspection point corresponding to one of the data signals involved in the difference.

42. A method as claimed in claim 40 or 41, wherein the step of displaying is performed by displaying said event signals with respect to a pair of orthogonal axes, and wherein each of said event signals represents the magnitude of the amount by which the difference in the magnitudes represented by the data signals differs from the magnitude of said threshold signals, one of said axes represents the magnitude of said event signals, and the other one of said axes represents the locations of the associated point along one axis of the object.

43. A method as claimed in claim 40, 41, or 42, wherein each of said event signals represents the location of the associated point on the surface of the object, one of said axes represents a vertical axis of the object, and the other one of said axes represents a horizontal axis of the object.