GB2478903A

GB2478903A - A combined infra-red camera/image projector viewing system for heat emission visualisation.

Info

Publication number: GB2478903A
Application number: GB1003109A
Authority: GB
Inventors: Brian Michael Harper; William Forrest Fagan
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-02-24
Filing date: 2010-02-24
Publication date: 2011-09-28
Also published as: GB201003109D0

Abstract

The combination of an infra-red camera and an image projector makes easier the examination of an an object or surface emitting heat as it allows the actual surface to be illuminated directly by a visible representation of the heat emissions from different areas of the surface e.g, wall of a building projected onto the surface of the real object as opposed to viewing these emissions on a monitor screen. A beam splitter may be used to remove the difference in viewing angle between camera and projector. False colour projection or contour lines may be used to delineate areas of different heat emission. The technique may be applied to millimentric radar viewing security systems, in ultrasonic, medical, and non-destructive testing systems and other visualisation measurement systems that would benefit from a projected visual overlay on the object being examined.

Description

This invention relates to the creation of a combined infra-red/visible imaging system where a visible spectrum TV projector is mounted on an infra-red camera so that the projected visible image corresponds to the field of view and magnification of the infra-red camera.

This allows, for example, the heat emissions of an object, under investigation, to be visualised directly on the surface of the real object where the projected image is derived from the infra-red camera that views the the same field of view as the projected image.

Using false colour encoding of the infra-red image, the object, being studied, will now show the appropriate heat emissions as various colours, depending on the temperature of the surface, that are directly visible on its surface thereby facilitating the location of temperature variations of its surface.Different colour palettes may be used in the false colour projection to suit the colour and reflectivity of the surface under investigation in order to maximise the visibility of the heat emissions.

Figure 1 illustrates the layout of the system.The infra-red camera records the heat emissions on a wall located inside a building.The image recorded by this camera is then fed into the image projector mounted on top of the camera which is tilted so that the fields of view of the camera coincides with that of the projector.The projector then projects this image back onto the wall so that it is superimposed over the field of view registered by the infra-red camera.It may be necessary to compensate for this shift in perspective as there is an angle between the viewing directions of the camera and the projector resulting in a linear magnification of the projected image along the axis defined by the plane in which the projector is tilted relative to the camera.Image processing of the camera's image can introduce the required optical magnification shift before it is relayed to the image projector in order that effects of perspective can be cornpensated.This ensures that an accurate overlay of the heat emissions on the wall are projected onto the correct geometric location from which they were emitted.

It is important that the field of view of the infra-red camera corresponds accurately with the field of view of the projected image and that the projected image precisely overlays the object's surface geometry, registered by the infra-red camera, in order that the projected local heat emission image be exactly mapped onto the object's surface.This may be implemented by manual adjustment or by means of a servo motor control link between a sensor on the infra-red camera lens and a motor on the projection camera lens assembly that adjusts the field of view and the magnification of the projector to correspond to that of the infra-red camera.In the case of a laser projector, only the magnification adjustment is necessary as the projected image is always in focus for all imaging distances.It is also important to consider the effects of parallax on the projected image.These effects occur if the optical axis of the infra-red camera lens is not coincident with the optical axis of the projector lens.This effect causes a linear magnification mis-alignment of the projected image on the objects surface.

Figure 2 shows the optical arrangement that compensates for the shift in perspective of the fields of view of the infra-red camera and the image projector that was described in Figure 1.

Here a beam splitter is placed at an angle of 45 degrees between the camera and the projector.The heat emissions being investigated are transmitted through a suitable beam splitter to the infra-red camera lens.The visible image produced by this camera is then projected by the projector onto the same beam splitter and then reflected exactly along the same direction as the field of view of the camera.This ensures that there is a one to one relationship between the fields of view of both the camera and the projector without the need for perspective compensation.It should be noted that the material of this beam splitter should allow the infra-red and the visible spectrum of light to be transmitted and reflected.

The system application is not exclusively linked to an infra-redlvisible camera combination as, for example, millimetric radar systems used in airport security for concealed weapons or explosive devices detection and the visualisation of objects or people in buildings or behind walls may exploit this capability.

The system could be used to make the information more readily available to a wider group of inspectors not being limited to a display on a monitor screen.The availability of larger, life-sized, images would be especially useful for rapid and accurate evaluation Furthermore, this invention could be used in any application where a projected image onto an object's surface could provide useful information by being on the actual object's surface.e.g ultrasonic, ultraviolet, and x-ray fault detection in engineering structures such as turbine blades and in medical imaging scanner data where non visible data could be displayed.

Claims

Claims 1. The combination of an infra-red camera with an image projector to facilitate the visual inspection of an object, with regards to the object's heat emissions, by projecting a visible representation of these emissions onto the surface of the object such as the interior wall of a building.
2. The use of a beam splitter to remove the difference in the viewing angle between the field of view of the infra-red camera and the the field of view of the image projector thereby eliminating the need for compensating for different viewing angles of the said camera and the projector by, effectively, making these angles identical.
3. The use of false colour projection techniques to delineate areas of different heat emissions on the object's surface and the use of different coloured palettes to optimise the projected image's visibility on the surface, the choice of which will be governed by the surface's colour and reflectivity. The heat emissions may be also projected onto the surface as a series of contour lines, each line of which represents a constant heat emission.
4. The use of the techniques, as described in claims 1 and 2, in millimetric radar viewing security systems, in ultrasonic, medical, and non-destructive testing systems and other visualisation measurement systems that would benefit from a projected visual overlay, on the object being examined, derived from non visible data generated by the respective inspection system.