IL178321A

IL178321A - Optical inspection system

Info

Publication number: IL178321A
Application number: IL178321A
Authority: IL
Original assignee: Orbotech Ltd
Priority date: 2006-09-26
Filing date: 2006-09-26
Publication date: 2014-08-31
Also published as: KR20080028278A; CN101153854A; IL178321A0; TW200815746A; CN101153854B; JP2008083044A

Description

OPTICAL INSPECTION SYSTEM J 09IN np'ia roiyn Orbotech Ltd.

Our Ref: 1362 OPTICAL INSPECTION SYSTEM FIELD OF THE INVENTION

[0001] The present invention relates to the inspection of electrical circuits during manufacture generally and more particularly to the reduction of misdetection of defects during the inspection of printed circuit boards.

BACKGROUND OF THE INVENTION

[0002] Automated optical inspection (AOI) systems are well known, and are available from various vendors, including Orbotech Ltd. of Yavne, Israel. Conventionally, candidate defects detected by AOI systems need to be verified as actual or false defects, typically by a human operator viewing an image of a candidate defect. The present Applicant has additionally developed processing systems for automatically verifying candidate defects as being real defects or false alarms.

SUMMARY OF THE INVENTION

[0003] The present invention seeks to provide an optical inspection system useful in reducing the number of misdetections of defects during the inspection of printed circuit boards.

[0004] There is thus provided in accordance with an embodiment of the present invention an optical inspection system for electrical circuit devices including optical inspection functionality which provides an optical inspection output of at least one region on an electrical circuit device being inspected, algorithmic inspection functionality which provides an algorithmic inspection output of the at least one region, the algorithmic inspection output indicating the presence of a possible defect at the at least one region, a display which provides a visually sensible display of the at least one region to an operator based on the optical inspection output and a display controller which is responsive to sensed operator behavior, indicating non-identification of a defect at the at least one region, and to the algorithmic inspection output, indicating the presence of a possible defect at the at least one region, for causing the display to provide a suitable indication of inconsistency between the presence of a defect as learned from the sensed operator behavior and the algorithmic inspection output for the at least one region. A suitable indication of inconsistency includes providing, a second time, a visually sensible display of the at least one region.

[0005] In accordance with an embodiment of the present invention the algorithmic inspection functionality includes fluorescence inspection functionality, for example employing deep violet or UV illumination that triggers fluorescence of an inspected substrate. Additionally or alternatively, the algorithmic inspection functionality includes at least one inspection functionality which is different from that employed in the optical inspection functionality. Preferably, the at least one inspection functionality includes at least one of a fluorescence inspection functionality, a dark field inspection functionality, a bright field inspection functionality, a UV inspection functionality and a height inspection functionality.

[0006] In accordance with another embodiment of the present invention the optical inspection functionality includes a reflectance inspection functionality. Additionally or alternatively, the optical inspection system also includes a defect analyzer operative to receive the optical inspection output of the at least one region and at least one reference image of the at least one region, and to provide to at least one of the algorithmic inspection functionality and the optical inspection functionality output indications of locations of candidate defects in the electrical circuit device being inspected. Preferably, the at least one reference image is derived from at least one computer file reference.

[0007] In accordance with yet another embodiment of the present invention the at least one computer file reference includes at least one binary image. Preferably, the at least one reference image is acquired from a CAD or CAM file employed in the design or manufacture of the electrical circuit device. Optionally, the at least one computer file reference is acquired from at least one printed circuit board which is known to be not defective.

[0008] In accordance with still another embodiment of the present invention the visually sensible display includes at least one reflectance image of the at least one region. Preferably, the sensed operator behavior includes viewing the visually sensible display for less than a predetermined time duration. Additionally, the predetermined time duration is less than five seconds, and may be less than two seconds. Alternatively, the sensed behavior includes a classification operation such as pressing a suitable computer key.

[0009] There is also provided in accordance with another embodiment of the present invention a method for optical inspection of electrical circuit devices including providing an optical inspection output of at least one region on an electrical circuit device being inspected, providing an algorithmic inspection output of the at least one region, the algorithmic inspection output indicating the presence of a possible defect at the at least one region, providing a visually sensible display of the at least one region to an operator based on the optical inspection output and responsive to sensed operator behavior, indicating non-identification of a defect at the at least one region, and to the algorithmic inspection output, indicating the presence of a possible defect at the at least one region, causing the display to provide a suitable indication of inconsistency between the presence of a defect as learned from the sensed operator behavior and the algorithmic inspection output for the at least one region. A suitable indication of inconsistency includes providing, a second time, a visually sensible display of the at least one region.

[0010] In accordance with an embodiment of the present invention the providing an algorithmic inspection output includes providing a fluorescence inspection output; for example in response to deep violet or UV illumination that triggers a suitable sensible fluorescence response. Additionally or alternatively the providing an algorithmic inspection output includes providing at least one inspection output which is different from that provided in the optical inspection output. Preferably, the providing at least one inspection output includes providing at least one of a fluorescence inspection output, a dark field inspection output, a bright field inspection output, a UV inspection output and a height inspection output.

[0011] In accordance with another embodiment of the present invention the providing an optical inspection output includes providing a reflectance inspection output. Preferably, the method also includes receiving the optical inspection output of the at least one region, receiving at least one reference image of the at least one region and providing output indications of locations of candidate defects in the electrical circuit device being inspected.

[0012] In accordance with yet another embodiment of the present invention the receiving the at least one reference image includes deriving the at least one reference image from at least one computer file reference. Additionally or alternatively, the receiving the at least one reference image includes acquiring the at least one reference image from at least one printed circuit board which is known to be not defective.

[0013] In accordance with still another embodiment of the present invention the providing a visually sensible display includes providing at least one reflectance image of the at least one region. Preferably, the sensed operator behavior includes viewing the visually sensible display for less than a predetermined time duration. Additionally, the predetermined time duration is less than five seconds and may be less than two seconds. Alternatively, the sensed operator behavior includes clarifying a defect, for example by applying a suitable marker, such as pressing a suitable computer key.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which:

[0015] Fig. 1 is a simplified partly pictorial partly block diagram illustration of an optical inspection system constructed and operative in accordance with an embodiment of the present invention; and

[0016] Fig. 2 is a simplified flow-chart showing a method of optical inspection employing the optical inspection system of Fig. 1, operative in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0017] Reference is made to Fig. 1, which is a simplified partly pictorial partly block diagram illustration of an optical inspection system constructed and operative in accordance with an embodiment of the present invention.

[0018] In accordance with an embodiment of the invention, an optical inspection system for electrical circuit devices includes an optical inspection functionality which provides optical inspection output of at least one region on an electrical circuit device being inspected, algorithmic inspection functionality which provides an algorithmic inspection output of the at least one region, the algorithmic inspection output indicating the presence of a possible defect at the at least one region, a display which provides a visually sensible display of the at least one region to an operator based on the optical inspection output and a display controller which is responsive to sensed operator behavior, indicating non-identification of a defect at the at least one region, and to the algorithmic inspection output, indicating the presence of a possible defect at the at least one region, for causing the display to provide a suitable indication of inconsistency between the sensed operator behavior and the algorithmic inspection output for the at least one region. A suitable indication of inconsistency includes providing, a second time, a visually sensible display of the at least one region. The sensed operator behavior is indicative of the presence or absence of a real defect.

[0019] As seen in Fig. 1, an optical inspection system 100 includes at least a first inspection station 110 acquiring an image including one or more reflectance images 112 of one or more regions of a first electrical circuit to be inspected, designated by reference numeral 114. The reflectance image 112 may be acquired, for example, by scanning first electrical circuit 114. The inspection station 110 is preferably a Discovery™ optical inspection system, commercially available from Orbotech Ltd. of Yavne, Israel, though any other suitable inspection station may be employed.

[0020] Reflectance images 112 are provided to a defect analyzer subsystem 120 which includes detection processing functionality and verification processing functionality. The detection processing functionality and verification processing functionality may be supported by separate CPUs or they may employ the same CPU. The detection processing functionality receives the reflectance image 112 and additionally receives a reference image 122 corresponding to first electrical circuit 114. Suitable reference images may be derived from computer file references (not shown), which may in turn be derived from CAM files and images acquired from printed circuit boards which are known to be not defective. In accordance with an embodiment of the invention, the computer file reference comprises a binary image. Optionally, the computer file reference includes a map of contours, namely edges between conductor and substrate, corresponding to an electrical circuit to be inspected.

[0021] The detection processing functionality of defect analyzer subsystem 120 is operative to automatically optically inspect a reflectance image 112, to compare the reflectance image 112 with reference image 122, and to output indications of candidate defects 126 on first electrical circuit 114. Upon completion of optical inspection, each electrical circuit is passed down stream to a verification station 130, such as a VeriSmart™ defect verification system, commercially available from Orbotech Ltd. of Yavne, Israel, whereat defect verification and/or correction is performed. It is appreciated that in Fig. 1, first electrical circuit 114 undergoing optical inspection is located at inspection station 110, while a second, previously inspected electrical circuit 132 is located at verification station 130. Though verification station 130 is shown as a stand-alone verification station, this need not necessarily be the case.

[0022] Previously inspected electrical circuit 132 has already been automatically optically inspected at inspection station 110, and at least one candidate defect thereon has been identified by detection processing functionality of defect analyzer subsystem 120. The locations of candidate defects on electrical circuit 132 typically are different from those found on other inspected electrical circuits of the same type, although some of the candidate defects may be similar and may recur at the location on successive electrical circuits of the same type.

[0023] The indications of candidate defects 126, corresponding to candidate defects identified on previously inspected electrical circuit 132, are received by a verification controller (not shown) which is in operative communication with verification station 130.

[0024] Inspection station 110 and verification station 130 may be separate units, as seen in Fig. 1. An example of a standalone verification station 130 is a VeriSmart™ defect verification system, commercially available from Orbotech Ltd. of Yavne, Israel.

An example of a standalone optical inspection system, is a Discovery™ optical inspection system, also commercially available from Orbotech Ltd. of Yavne, Israel. Some configurations of the Discovery™ optical inspection system are additionally provided with a video image acquisition system operative to acquire selected video images of suspected defects which images may be used to manually filter some suspected defects prior to correction at a suitable downstream correction station. Alternatively, the Inspection station 110 and verification station 130 may be integrally formed, for example as in the Spiron™ optical inspection system, also commercially available from Orbotech Ltd. of Yavne, Israel.

[0025] Verification station 130 preferably includes a camera 140 and a camera positioner 142 operative to sequentially position camera 140 to sequentially view locations of candidate defects 146 according to an output of the verification controller. The output of the verification controller provides an indication of the geometric location of candidate defects as identified by detection processing functionality of defect analyzer subsystem 120, and the positioner 142 moves the camera 140 to the indicated position. In the embodiment seen in Fig. 1, camera positioner 142 is operative to independently control an X-Y positioning of camera 140, though this need not necessarily be the case. For example, positioner 142 may alternatively control positioning of the camera 140 in a polar coordinate system.

[0026] In accordance with an embodiment of the present invention, at each sequentially viewed candidate defect location 146 on electrical circuit 132, the location 146 is illuminated with light suitable to provide an optical inspection output which is preferably displayed to an operator as a visually sensible image of candidate defect location 146. Additionally, candidate defect location 146 is illuminated with a different illumination configuration, for example light in at least one other wavelength or provided at different angles of incidence, suitable to provide an image suitable for algorithmic analysis thereof.

[0027] In an embodiment of the present invention, camera 140 acquires a reflectance image 150 of the candidate defect location 146 and a fluorescence image 152 of a fluorescence response to light at suitable wavelength thereat, for example, an image showing a response to deep violet or UV illumination. The camera 140 may acquire one or more of a dark field image, a bright field image, a UV image, an IR image, an image in a different spectrum and an image acquired employing a height sensor, in addition to or as an alternative to a fluorescence image 152. The fluorescence image 152 and reflectance image 150 typically are acquired during nearly coincident time intervals.

[0028] In the embodiment seen in Fig. 1, upon acquisition of verification images 150 and 152 at a first defect location 146, the verification processing functionality of defect analyzer subsystem 120 performs algorithmic evaluation of a fluorescence image 152, in the background for example. Camera 140 is repositioned at a next candidate defect location, the location of which is provided by the output of the verification controller, and one or more verification images are acquired at the next location while an operator is evaluating a suitable image of location 146, for example a reflectance image 150 thereof. In an embodiment of the invention, acquisition of verification images 150 and 152 proceeds at a given rate of image acquisition, independently of evaluation by an operator which typically proceeds at a slower pace. Thus verification images 150 are acquired for each location, stored in a memory (not shown) and then supplied to the operator upon demand. Fluorescent verification images 152 are acquired for selected locations and algorithmically inspected in the background with algorithmic inspection results being employed as needed to confirm defect verification by the operator.

[0029] The reflectance image 150 of a candidate defect location 146 is preferably displayed to an operator located adjacent defect analyzer subsystem 120 for her review. Typically, the operator examines the reflectance image 150, and decides whether the image includes an actual defect. If so, the operator typically repairs the defect in electrical circuit 132 or if the defect cannot be repaired, the electrical circuit 132 is suitably marked. Where image 150 shows a misdetection corresponding to a non-defect, the operator typically proceeds to examine an image of the next candidate defect location 146 shortly after reviewing the current candidate defect location, typically within 1-2 seconds and usually less than 5 seconds, although the system can be set to provide a longer or shorter time interval for manual review of a candidate defect location. In an embodiment of the invention, upon concluding that a first suspected defect location is a misdetection, the operator presses a computer key instructing the computer to display an image of the next suspected defect location, thereby providing, through behavior, a functional indication that the first suspected defect location is a misdetection.

[0030] Concurrently with analysis of reflectance images 152 by the operator, or prior thereto, the fluorescence images 152 of the candidate defect locations are provided to the verification processing functionality of the defect analyzer subsystem 120. Subsystem carries out automatic algorithmic analysis of each fluorescence image 152 to algorithmically verify whether a candidate defect included therein is an actual defect or rather a misdetection of a non-defect. Algorithmic inspection typically is carried out on a given defect location concurrently with or prior to manual defect verification performed by the operator, and is utilized once verification by the operator is completed to confirm correctness of the operator verification. A suitable automatic verification algorithm is presently implemented in the Spiron™ system, commercially available from Orbotech Ltd. of Yavne, Israel. Other suitable algorithmic verification systems and methods are described in Applicant's copending Patent Application Nos. 10/793,224 and 11/254,756, the disclosures of which are hereby incorporated by reference.

[0031] In accordance with an embodiment of the present invention, defect analyzer subsystem 120 includes a display controller (not shown), which is responsive to sensed operator behavior, such as examining an image of an actual defect for less than two seconds, indicating non-identification of an actual defect at candidate defect location 146, and to the algorithmic inspection output, indicating the presence or absence of a possible defect at candidate defect location 146. In the event of inconsistency between an algorithmic result and a verification indication corresponding to behavior of the operator, such inconsistency is noted and typically displayed. In an embodiment of the invention, in the event of inconsistency between the algorithmic and operator result, the reflectance image 150 of candidate defect location 146 is displayed a second time to the operator. Redisplaying of the image may be either with or without a particular indication that the defect location had been previously reviewed by the operator.

[0032] As seen in Fig. 1, a candidate defect location A is displayed to the operator, who briefly examines it. Location A is not indicated by the operator as including a real defect resulting in a next candidate defect location, shown as candidate defect location B, being displayed within several seconds following the display of candidate defect location A. At candidate location B, a real defect is present which the operator corrects.

When the operator completes examination and correction of the actual defect at candidate defect location B, here shown as requiring forty seconds after the display of defect candidate location B, although it is appreciated that different time periods may be required to affect correction or repair of a defect, a next candidate location C is displayed. After review of location C, which is not indicated as containing a defect by the, a next image is displayed within several seconds. In this case, the next image corresponds to candidate defect A, which is displayed a second time.

[0033] It is noted that in an embodiment of the invention, concurrently with the operator's examination of the candidate defect locations, the display controller receives outputs of the algorithmic analysis of candidate defect locations A, B and C, which are performed in the background and which indicate, according to inspection algorithms, whether a candidate defect location is an actual defect. In the embodiment seen in Fig. 1, the algorithmic analysis indicates that location A is a defect, which initially is not detected by the operator; that location B is a real defect corresponding to the detection result of the operator; and that location C is a misdetection which is also detected by the operator as being a misdetection. In an embodiment of the present invention , the inconsistency between the algorithmic result and the operator result (as sensed by the operator behavior of evaluating location A for merely a few seconds) causes the reference image of candidate defect location A to be displayed to the operator. It is appreciated that methods for indicating an inconsistency between an operator result and an algorithmic result, other than redisplaying a reflectance image for a location corresponding to the inconsistency, may be employed. For example, an inconsistency may be indicated by producing a report of inconsistencies and giving the operator a choice to return and reanalyze selected defect locations, for example. Likewise, it is appreciated that the sensed operator behavior correspond to a sensed time interval for evaluating a location as being defective, or other sensed behavior such as pressing a computer key to classify a particular location as including a defect or mis-detection.

[0034] Reference is now made to Fig. 2, which is a simplified flow-chart of a method of optical inspection employing the optical inspection system of Fig. 1, operative in accordance with an embodiment of the present invention.

[0035] In accordance with an embodiment of the invention, a reflectance image of an electrical circuit being inspected is acquired, for example at inspection station 110 (Fig. 1). The reflectance image is automatically optically inspected and analyzed, for example at defect analyzer subsystem 120 (Fig. 1), to identify candidate defects in the electrical circuit being inspected. At this stage, various candidate defects have been identified, and verification of the candidate defects as actual defects or as misdetections of non-defects is required.

[0036] In accordance with an embodiment of the invention, an output indicating each of the candidate defects on the electrical circuit being inspected optionally is processed to filter out repetitive candidate defects. These include, for example, geometric candidate defects, which recur on a series of like electrical circuits. Recurring candidate defects, which recur at the same location, panel after panel, in a series of like panels of electrical circuits, may be filtered if they have been determined not to constitute an actual defect, despite a recurring geometric malformation, for example as described in greater detail in applicant's / assignee's copending U.S. Patent Application No. 11/072,235.

[0037] An output indicating each of the candidate defects requiring verification is provided to a verification station, for example verification station 130 (Fig. 1). For each candidate defect location, a reflectance image is acquired and is provided to an operator of the verification station for examination.

[0038] A second image, typically a fluorescence image of the candidate defect location, is also acquired, for example at verification station 130 (Fig. 1). The second image is preferably acquired generally shortly prior to, or following, or simultaneously with acquiring the reflectance image. Preferably, the fluorescence image includes the candidate defect and a small part of the area surrounding the candidate defect. A corresponding portion of a reference map, such as reference map derived from a CAM file, is also identified. The fluorescence image is algorithmically analyzed in the background to determine whether the candidate defect included therein is an actual defect or a misdetection of a non-defect. Suitable automatic analysis algorithms are described in one or more of the applicant's/assignee's copending U.S. Patent Application Nos. 10/793,224 and 11/254,756 the disclosures of which are incorporated herein by reference. An output of the analysis algorithm, indicating whether the candidate defect is an actual defect or a misdetection of a non-defect is preferably provided to a verification display control which preferably forms part of the defect analyzer subsystem 120 (Fig. 1).

[0039] If the candidate defect was identified by the algorithmic analysis to be an actual defect, the verification display control checks whether the operator also identified the candidate defect as an actual defect. This is achieved for example by ascertaining whether the operator positively identified a defect, for example by pressing a designated computer key, or by checking the time duration during which the operator viewed or examined the image of the candidate defect. If, for example, this time duration was relatively short, for example less than five seconds and typically less than two seconds, the verification display control decides that the operator did not identify the candidate defect as an actual defect. If there is an inconsistency between the algorithmic result and the result of verification by the operator, a suitable indication is provided. The suitable indication may simply be a redisplay of the reflectance image of the candidate defect to the operator to enable further operator examination of the defect. Redisplay of the reflectance image may be essentially seamless and unknown to the operator. Optionally, a warning of the inconsistency may be provided and optionally recorded, for example for the purpose of quality control.

[0040] Following this procedure, verification is completed for each of a desired set of candidate defects. Upon completion of verification, electrical circuits are passed on for further processing. For example, an electrical circuit, in which all of the defects have been confirmed as being false defect detection, may be passed on to a further electrical circuit fabrication operation, for example, via micro-machining.

[0041] Electrical circuits in which some of the candidate defects have been verified as being actual defects, or in which automatic verification was inconclusive, may require additional defect verification or a repair operation.

[0042] It is appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the present invention includes both combinations and subcombinations of various features described hereinabove as well as variations and modifications thereto which would occur to a person of skill in the art upon reading the above description and which are not in the prior art.

Claims

1. An optical inspection system for electrical circuit devices comprising: an optical inspection functionality which provides an optical inspection output of at least one region on an electrical circuit device being inspected; an algorithmic inspection functionality which provides an algorithmic inspection output of said at least one region, said algorithmic inspection output indicating the presence of a possible defect at said at least one region; a display which provides a visually sensible display of said at least one region to an operator based on said optical inspection output; and a display controller which is responsive to sensed operator behavior, indicating non-identification of a defect at said at least one region, and to said algorithmic inspection output indicating the presence of a possible defect at said at least one region, for providing an indication of an inconsistency between said sensed operator behavior and said algorithmic inspection output for said at least one region.

2. An optical inspection system according to claim 1 and wherein said display controller is further operative to cause said display to provide an additional visually sensible display of said at least one region to said operator.

3. An optical inspection system according to claim 1 and wherein said algorithmic inspection functionality includes a fluorescence inspection functionality.

4. An optical inspection system according to claim 3 and wherein said fluorescence inspection functionality includes a deep violet inspection functionality.

5. An optical inspection system according to claim 3 and wherein said fluorescence inspection functionality includes a UV inspection functionality.

6. An optical inspection system according to claim 1 and wherein said algorithmic inspection functionality includes at least one inspection functionality which is different from that employed in said optical inspection functionality.

7. An optical inspection system according to claim 6 and wherein said at least one inspection functionality comprises at least one of a fluorescence inspection functionality, a dark field inspection functionality, a bright field inspection functionality, a UV inspection functionality and a height inspection functionality.

8. An optical inspection system according to claim 1 and wherein said optical inspection functionality comprises reflectance inspection functionality.

9. An optical inspection system according to claim 1 and also comprising a defect analyzer operative to receive said optical inspection output of said at least one region and at least one reference image of said at least one region, and to provide to at least one of said algorithmic inspection functionality and said optical inspection functionality output indications of locations of candidate defects in said electrical circuit device being inspected.

10. An optical inspection system according to claim 9 and wherein said at least one reference image is derived from at least one computer file reference.

11. An optical inspection system according to claim 9 and wherein said at least one reference is derived from at least one of: a CAD file and a CAM file.

12. An optical inspection system according to claim 11 and wherein said at least one computer file reference comprises at least one binary image.

13. An optical inspection system according to claim 9 and wherein said at least one reference image is acquired from at least one printed circuit board which is known to be not defective.

14. An optical inspection system according to claim 1 and wherein said visually sensible display comprises at least one reflectance image of said at least one region.

15. An optical inspection system according to claim 1 and wherein said sensed operator behavior comprises viewing said visually sensible display for less than a predetermined time duration.

16. An optical inspection system according to claim 15 and wherein said predetermined time duration is less than five seconds.

17. An optical inspection system according to claim 17 and wherein said predetermined time duration is less than two seconds.

18. An optical inspection system according to claim 1 and wherein said sensed operator behavior comprises receiving an indication from a pressed computer key.

19. A method for optical inspection of electrical circuit devices comprising: providing an optical inspection output of at least one region on an electrical circuit device being inspected; providing an algorithmic inspection output of said at least one region, said algorithmic inspection output indicating the presence of a possible defect at said at least one region; providing a visually sensible display of said at least one region to an operator based on said optical inspection output; and responsive to sensed operator behavior indicating non-identification of a defect at said at least one region, and to said algorithmic inspection output indicating the presence of a possible defect at said at least one region, providing an indication of an inconsistency between said sensed operator behavior and said algorithmic inspection output for said at least one region.

20. A method according to claim 19 and wherein said providing an indication of a consistency comprises causing said display to provide an additional visually sensible display of said at least one region to said operator.

21. A method according to claim 19 and wherein said providing an algorithmic inspection output includes providing a fluorescence inspection output.

22. A method according to claim 21 and wherein said providing said fluorescence inspection output includes providing a deep violet inspection output.

23. A method according to claim 21 and wherein said providing said fluorescence inspection output includes providing a UV inspection output.

24. A method according to claim 19 and wherein said providing an algorithmic inspection output includes providing at least one inspection output which is different from that provided in said optical inspection output.

25. A method according to claim 24 and wherein said providing at least one inspection output comprises providing at least one of a fluorescence inspection output, a dark field inspection output, a bright field inspection output, a UV inspection output and a height inspection output.

26. A method according to claim 19 and wherein said providing an optical inspection output comprises providing a reflectance inspection output.

27. A method according to claim 19 and also comprising: receiving said optical inspection output of said at least one region; receiving at least one reference image of said at least one region; and providing output indications of locations of candidate defects in said electrical circuit device being inspected.

28. A method according to claim 27 and wherein said receiving said at least one reference image comprises deriving said at least one reference image from at least one computer file reference.

29. A method according to claim 28 and wherein said receiving at least one reference comprises deriving said at least one reference image from at least one of: a CAD file and a CAM file.

30. A method according to claim 27 and wherein said receiving said at least one reference image comprises acquiring said at least one reference image from at least one printed circuit board which is known to be not defective.

31. A method according to claim 19 and wherein said providing a visually sensible display comprises providing at least one reflectance image of said at least one region.

32. A method according to claim 19 and wherein said sensed operator behavior comprises viewing said visually sensible display for less than a predetermined time duration.

33. A method according to claim 32 and wherein said predetermined time duration is less than five seconds.

34. A method according to claim 33 and wherein said predetermined time duration is less than two seconds.

35. A method according to claim 19 and wherein said sensed operator behavior comprises receiving an indication from a pressed computer key.