GB2196206A - Superimposition in a video display system - Google Patents

Description

GB2196206A 1 SPECIFICATION which source is indicative of a position of in

vestigation of the associated detector system, Superimposition in a video display system and which source produces light, or other ra diation to which the camera responds, having The invention relates to apparatus for provid- 70 a distinguishing characteristic, the camera pro ing a video display in which an image derived ducing, when trained upon an area including from one or more detector systems is super- the said position of investigation, a video im imposed upon a visual image derived from a age signal including that produced by the light camera. or other radiation from the said source on the In this way a user of the apparatus can be 75 probe, a memory system, means for scanning assisted by relating the output of a non-visual of the memory system in synchronism with signal detector device to the visual appearance the video image signal, means responsive to of the image produced by the camera of an the said distinguishing characteristic for pro object under test. viding identification of the address in the 1 15 Whilst highly sophisticated image processing 80 memory system of the position of the probe, and handling techniques are available using means operative independently of the said dis computers or microprocessors, a problem with tinguishing characteristic under control of the the type of image superimposition referred to detector system for causing the memory sys above is that of registering one image in its tem to store at the said identified address a proper relationship and scale with the other. 85 representation of detector system output at One solution to this problem is disclosed in the position of the probe corresponding with GB 2 136 242 according to which apparatus the said identified address, and means for is provided for generating a video display sig- combining video image signals from the cam nal capable of driving a suitable imaging sys- era with video signal elements derived from tem to produce superimposed images from 90 the memory system so that the combined sig two or more detector systems, which appara- nals when fed to an imaging system are dis tus comprises a camera, one or more detector played as the visual image seen by the cam systems, the or at least one of the detector era with superimposed picture elements repre systems including a movable probe, a source sentative of detector system output at posi on the probe, the position of which source is 95 tions of investigation of the probe.

indicative of the position of investigation of The said means under control of the detec- the associated detector system, and which tor system may trigger the memory system source produces light, or other radiation to whenever output from the detector system which the camera responds, in excess of a has a predetermined characteristic to store at predetermined intensity whenever the detected 100 the said identified address in the memory sys signal of the said associated detector system tem corresponding with the position of the has a predetermined characteristic, the camera probe data representing a predetermined video producing, when trained upon an area includ- signal element, so that the said combined sig ing the said position of investigation, a video nals when fed to an imaging system are dis signal including that produced by the light or 105 played as the visual image seen by the cam other radiation from the said source on the era with superimposed predetermined picture probe, a threshold detector for detecting elements at all positions of investigation of whenever light or said other radiation received the probe at which the detector system has by the camera exceeds the said predetermined produced output having the said predeter intensity, a memory system scanned in syn- 110 mined characteristic.

chronism with the video signal from the cam- In this way, using a camera which responds era and arranged to store the video signal at to visible light and a light source on the all positions where the said predetermined in- probe, it is possible to scan the probe over tensity is exceeded, and means for mixing vi- an object and build up an array of bright deo signals from the memory system with the 115 points superimposed upon the ordinary visual video signals from the camera so that the image of the object, the bright points corre mixed signals when fed to an imaging system sponding with some predetermined character are displayed as the visual image seen by the istic under investigation. Thus for example, the camera with superimposed bright points at all detector system may be as described in Brit positions on the image where the said predet- 120 ish Patent Specification No 2044198 in which ermined intensity has been exceeded. backscattered penetrating radiation is de- The present invention is a development of tected, for example neutrons to reveal low that described in GB 2 136 242 and provides atomic number material concealed behind apparatus for generating a video display signal steel.

capable of driving a suitable imaging system 125 There may be additional detector systems to produce superimposed images, which appa- each including a probe with a light source ratus comprises a video camera, one or more thereon. In this case it is desirable to distin detector systems, the one or at least one of guish one detector system from another by the detector systems including a movable using different coloured light sources on the probe, a source on the probe, the position of 130 probes. Further, the indication of the response 2 GB2196206A 2 of a single detector system may be sub-div- posing on an image of a visual scene an im ided by providing on the probe a plurality of age produced using a detector of non-visual light sources distinguishable from one another signals, in this example an ultrasonic inspec by differences in colour. It is also possible for tion system.

certain applications that display may be 70 A sample under inspection is represented at wanted of only the images produced by 11. A conventional ultrasonic inspection sys- scanning the probes of two or more detectors tem 12 has a probe 13 and provides an out without including display of the visual scene. put signal on line 14. In a simple arrangement, In this case the camera would be set to re- this output signal is digital having one level (1) spond only to the brightness of the light 75 when the system detects a defect within the sources on the probes and to produce no imregion of inspection and another level (0) age from other sources of light. when no defect is detected.

In one arrangement according to the inven- The probe 13 is modified for the purpose of tion the said distinguishing characteristic is the present example by mounting thereon a provided by an intensity of the light, or said 80 point source of light 15 which is switched other radiation, in excess of a predetermined permanently on for the duration of a test.

intensity. In this case, the said means respon- A monochrome video camera 16 is provided sive to the distinguishing characterstic includes with synchronising signals on line 17 from a a threshold detector. It will be appreciated microcomputer 18. The output signal from the -20 that, to avoid false indications of probe posi- 85 camera 16 representing the intensity of each tion, the intensity of the light, or said other pixel in the raster scan sequence is fed via radiation, from the source has to exceed that line 19 to a threshold detector 21 and to a from any other object within the scene ob- network 22 by which the monochrome inten served by the camera. sity signal is applied via solid state switches In another arrangement according to the in- 90 23, 24, 25 to three lines 26, 27, 28 con- vention the said distingishing characteristic is nected respectively to the RGB (red, green, provided in that the light, or said other radia- blue) inputs of colour monitor 31, As will be tion, from the source is flashing or modulated come clearer from the following description, in a predetermined manner, and the said the synchronising signal from line 17 together means responsive to the distinguishing charac- 95 with RGB on lines 26, 27, 28 all connected to teristic responds to the said flashing or modu- the colour monitor 31 provide a composite lation. colour video image signal input in a standard Conveniently, the said predetermined video format to the colour monitor 31.

signal element has one characteristic, for The solid state switches 23, 24, 25 are example for a green coloration, when the out- 100 controlled respectively by the RGB output put from the detector system has one charac- from the microcomputer, shown as lines 32, teristic, for example indicative of no defect, 33, 34. The associated switch 23, is closed and the said predetermined video signal ele- when the line 32, carries a signal and open ment has another characteristic, for example when the signal is at a predetermined low for a red coloration, when the output from the 105 level. Switches 24, 25 operate in the same detector system has another characteristic, for way from the signal levels on lines 33 and 34 example indicative of the presence of a de- respectively.

fect. Where a detector system is capable of A television to X-Y converter 35 is provided providing a range of output signals indicative for generating X,Y coordinates representing of a corresponding range in the property to 110 position for the microcomputer memory sys which the detector system responds, then a tem from the television raster scan signal. A corresponding range of characteristics, for synchronising signal for the converter 35 is example in the form of a grey scale, of said provided on line 17 and output signals on line predetermined video signal element may be 36 to the microcomputer 18 combined with generated. 115 those on line 14 from the ultrasonic inspection Preferably the memory system and the said system provide data input to the microcompu- -means for scanning of the memory system ter 18. Operation of the converter 35 is under compromise a microcomputer. Synchronism control of the threshold detector 21.

with the video camera is achieved by connect- In operation, the intensity of light from the _5 ing a synchronising signal output from the misource 15 is set at a level exceeding that crocomputer to a synchronising signal input on from any other object in the field of view of the camera, so as to drive the camera scan in the camera 16.

synchronism with the video display signal gen- Initially, all the solid state switches 23, 24, erator of the microcomputer. 25 are closed so that the monitor 31 displays A specific construction of apparatus embo- 125 a black and white picture corresponding with dying the invention will now be described by the visual scene observed by the camera 16.

way of example and with reference to the However, as the camera scan takes in the drawing filed herewith, which is a block circuit image of the point source 15, the light inten diagram of the apparatus. sity is such that the signal level on line 19 The drawing shows a system for superimexceeds the threshold set in threshold detec- 3 1 GB2196206A 3 tor 21. This triggers converter 35 to supply puter RGB output with that from the video to the microcomputer 18 on line 36 the ad- camera.

dress of the computer memory location corre- One problem met on occasion with the sponding to the position in the image at that apparatus of this example is that the threshold instant of the point source 15. 70 level in the threshold detector 21 is exceeded In this example, the microcomputer 18 is by the appearance of a bright object, uncon- programmed to store at that address data nected with the probe 13, in the field of view from line 14 in such a form that output sig- of the camera 16. A solution is to provide nals on the RGB lines 32, 33, 34 from the periodic automatic detection of the maximum microcomputer will have the following effect 75 intensity in the image when the point source at all subsequent scans until the data at that 15 is switched off and to reset the intensity memory address is changed or reset: of the point source 15, on switching it on 1. if there is no defect signal on line 14, again, to a level in excess of that maximum.

switches 23 and 25 are opened, switch 24 is The threshold detector 21 has, of course, to closed 80 be reset simultaneously to a level above that 2. if there is a defect signal on line 14, maximum and below the new level of the po- switches 24 and 25 are opened, switch 23 is int source 15.

closed. Another solution is provided by a modifica- The consequence is that the pixel(s) in the tion in which the point source 15 is made to display corresponding to the position of the 85 flash on and off in synchronism with each point source 14 is (are) turned green if there successive frame scan. The threshold detector is no defect signal and red if there is a defect 21 is omitted and the microcomputer 18 is signal. If the probe 13 is now moved to programmed to register pixels which switch make, for example, a scanned inspection of on and off in phase with the frame scan.

the sample 11, each new position is -painted 90 The invention is not restricted to the details in- on the display, green showing where in- of the foregoing example. Other detector sys spection has been carried out and no defect tems can be used such as, for example, use found, red showing where defects have been penetrating radiation or eddy currents. Indeed, found. the apparatus can be used with any detector In this example the computer is programmed 95 system for which response can be confined to so that if the probe 13 is scanned over a limited areas defined by a probe position or region more than once, green display can be probe and associated point source position.

changed to red, but not vice versa. Thus, de- It may be convenient, as described in GB 2 tection of a defect shows as red on the dis- 136 242 to use one or more lenses and/or play even although a previous scan of the 100 mirrors to provide a desired apparent or vir same area revealed no defect. However, once tual position of the point source.

a defect has been detected, the associated The arrangement is readily adapted for use red display cannot be changed back to green. with a camera which responds to other than It will be appreciated that the arrangement visual radiation. Thus, a camera sensitive to as described will operate with any form of 105 infra-red radiation, for example may be used.

detector system having a binary or on/off out- Where the camera, as is usual, also responds put signal characteristic. to visible light, an infra-red emitting diode However, the flexibility of a microcomputer could be used as the source on the probe.

is readily harnessed to give a more sophisti- The intensity of the infrared emitted by the cated capability. Thus a detector system giv- 110 diode would have to be such as to exceed a ing a range of six different output signal char- predetermined reference level. Alternatively, an acteristics is readily accommodated in the ar- infra-red camera would clearly enable a general rangement described by switching to generate image to be formed of a scene (eg at night) green, red, blue, red/green, red/blue, green/- which is not illuminated with visible light but blue according to which detector signal char- 115 which is emitting infra- red. In that case the acteristic is received. source on the probe could also be an infra-red For example the ultrasonic inspection sys- emitting diode or alternatively could be a tem 12 has a facility for providing an indica- source of visible light.

tion of whether or not the coupling between The composite video signal output may be the probe 13 and the sample 11 is satisfac- 120 recorded on a video recorder for subsequent tory. A signal indicating poor coupling can display via a monitor. The composite video thus be arranged to produce a particular col- signal may be transmitted over long distances our as a warning to the operator showing re- by cable or radio transmission if desired.

gions of the sample where the scan should be In a development, initial setting up of the repeated. 125 camera iris and intensity of the source on the For still greater sophistication in which a lar- probe is made easier by additional camera sig- ger number of detector output signal charac- nal output level detectors and software con teristics is accommodated, then it is neces- trol. Thus, for example, under software con sary to introduce, rather than simple switch- trolled instructions displayed on the screen, ing, a mixing of signal intensity from the corn- 130 the operator is required to adjust the camera 4 GB2196206A 4 iris, with the probe source off, until the maxi- claim 2, wherein the said distinguishing char mum image signal intensity (the brightest ob- acteristic is provided by an intensity of the ject in the visual scene) is greater that 50% light, or said other radiation, in excess of a and less than 70% of the maximum (satura- predetermined intensity and the said means tion) output of which the camera is capable. 70 responsive to the distinguishing characteristic The probe source is then switched on and its includes a threshold detector.

intensity increased stepwise until it produces 4. An apparatus as claimed in claim 1 or an- output signal intensity at 95% of the cam- claim 2, wherein the said distinguising charac era maximum. teristic is provided in that the light, or said 75 other radiation, from the source is flashing or

Claims (3)

CLAIMS modulated in a predetermined manner, and the

1. An apparatus for generating a video dis- said means responsive to the distinguishing play signal capable of driving a suitable imagcharacteristic responds to the said flashing or ing system to produce superimposed images, modulation.

which apparatus comprises a video camera, 80 5. An apparatus as claimed in claim 2, one or more detector systems, the one or at wherein the said predetermined video signal least one of the detector systems including a element has one characteristic, when the out movable probe, a source on the probe, the put from the detector system has one charac position of which source is indicative of a po- teristic, and the said predetermined video sig- sition of investigation of the associated detec- 85 nal element has another characteristic, when tor system, and which source produces light, the output from the detector system has or other radiation to which the camera re- another characteristic.

sponds, having a distinguishing characteristic, 6., An apparatus as claimed in claim 2, the camera producing, when trained upon an wherein a detector system is capable of pro- area including the said position of investiga- 90 viding a range of output signals indicative of a tion, a video image signal including that pro- corresponding range in the property to which duced by the light or other radiation from the the detector system responds, and a corre said source on the probe, a memory system, sponding range of characteristics of said pre means for scanning of the memory system in determined video signal element is generated.

synchronism with the video image signal, 95 7. An apparatus as claimed in any of the means responsive to the said distinguishing preceding claims, wherein the memory system characteristic for providing identification of the and the said means for scanning of the mem address in the memory system of the position ory system comprise a microcomputer and of the probe, means operative independently synchronism with the video camera is of the said distinguishing characteristic under 100 achieved by connecting a synchronising signal control of the detector system for causing the output from the microcomputer to a synchron memory system to store at the said identified ising signal input on the camera, so as to address a representation of detector system drive the camera scan in synchronism with the output at the position of the probe corre- video display signal generator of the micro- sponding with the said identified address, and 105 computer.

means for combining video image signals from 8. An apparatus substantially as hereinbe- the camera with video signal elements derived fore described with reference to, and illus from the memorypystem so that the com- trated in, the drawing filed herewith.

bined signals when fed to an imaging system - are displayed as the visual image seen by the Published 1988 at The Patent Office, State House, 66/71 HighHolborn, London WC 1 R 4TP. Further copies may be obtained from camera with superimposed picture elements The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD.

representative of detector system output at Printed by Burgess & Son (Abingdon) Ltd. Con. 1/87.

positions of investigation of the probe.

2. An apparatus as claimed in claim 1, wherein the said means under control of the detector system trigger the memory system whenever output from the detector system has a predetermined. characteristic to store at the said identified address in the memory sys tem corresponding with the position of the probe data representing a -predetermined video signal element, so that the said combined sig nals when fed to an imaging system are dis played as the visual image seen by the cam era with superimposed predetermined picture elements at all positions of investigation of the probe at which the detector system has produced output having the said predeter mined characteristic.

3. An apparatus as claimed in claim 1 or