FR2736235A1 - Image and monitoring mode combination method for thermal camera - Google Patents

Abstract

The method involves use of an objective lens (L1) to provide an image at infinity for a horizontal linear mosaic of detectors (DA). A first mirror (M1) lies on the optical axis in a plane at 45 degrees to it and oscillates about an axis (OY) parallel to the mosaic to give a vertical sweep of the scene in image mode. The system elements rotate about a vertical axis to operate a panoramic sweep of the scene in monitoring or standby mode. The optical axis in a vertical direction (OZ) is deflected by the first mirror to a horizontal direction in monitoring mode and the linear mosaic is turned through 90 degrees in a horizontal plane. The optical axes for both modes merge in the horizontal direction.

Description

DESCRIPTION ZAthermal chamber for the implementation of a process combining iodines for observation, imagery and surveillance1.

 The invention relates to a method combining the iodine observation imaging and surveillance of a thermal camera comprising, among other elements, a linear mosaic of detectors arranged horizontally, an objective giving an infinite image of said mosaic, a first inclined plane mirror. of 45 on the optical axis of said objective and oscillating on either side of said inclination around an axis parallel to said linear mosaic in order to carry out the vertical scanning of the landscape according to the iodine called Zd'inagerie ", the horizontal image of said linear mosaic of detectors then being placed in a vertical direction, the oscillating object of said first mirror being stopped and all of said elements rotating in a uniform rotational movement around an optical axis arranged in a vertical direction perform a panoramic sweep of the landscape according to the so-called standby or 'surveillance' mode.

 In thermal cameras designed according to the so-called imaging observation mode, different types of scanning can be used - parallel scanning with vertical detector, - parallel scanning with horizontal detector, - series and series-parallel scanning.

 The vertical detector parallel scanning cameras have a linear mosaic of detectors arranged parallel to the vertical side of the image and an optico-mechanical scanning device driving the detector image on the scene in the vertical direction.

 These cameras require the use of a menorisation device (electronic or optical) before being able to present the image on a television viewer whose lines are naturally horizontal because the image is analyzed from left to right (or from right to left) as it is played from top to bottom.

 The horizontal detector parallel scanning cameras have a linear mosaic of detectors arranged parallel to the horizontal side of the image and an optico-mechanical scanning device driving the detector image on the scene in the vertical direction.

 These cameras do not require intermediate storage because the image is analyzed in the same direction as it is rendered. In addition, the number of mosaic detectors and the number of lines of the television standard are mutually independent.

 Serial or series-parallel scanning cameras have a small mosaic associated with an opto-co-mechanical device which draws their image on the scene so as to describe the regularly arranged lines from top to bottom of the image.

 These cameras generally require the use of a small memorization in order to be able to present the image on a conventional television viewer.

 The cameras designed according to the iodine observation observation or panoramic or sectoral surveillance generally have a linear mosaic of detectors placed perpendicular to the direction of the optico-mechanical scanning, this generally horizontal (in azimuth) causing the image of detectors on a full turn or on a fraction of a turn.

 Morphologically, surveillance cameras are therefore close to cameras of the vertical scanning parallel scanning type. In both cases, the scanning is horizontal and the detector vertical: it suffices to rotate a camera with vertical detector, around a vertical axis, scanning stopped, so that the image of the mosaic describes the horizon.

 However, cameras of the parallel scanning type with horizontal detector and those of the serial or series-parallel scanning type have advantages which often make them prefer to cameras of the parallel scanning type with vertical detector: independence between the number of lines and the number of detectors, absence of significant memory 1 smaller volume of electronics.

 The method described in the preamble makes it possible, starting from a camera of the type with parallel scanning with horizontal detector or from a camera of the type with series-parallel scanning, to also produce a monitoring device with scanning in field, the two functions, imagery and standby which can be used alternately.

In known methods of the same kind, the transformation of the image obtained in a horizontal direction (iodine imaging) into an image arranged in a vertical direction (iodine monitoring) is usually carried out by means of an image rotation element which can be a conventional optical element such as a Pechan prism or
Rantch.

 Such image rotation elements are bulky and expensive; they are more difficult to center and their use in the infrared field requires their realization in very absorbent materials (germaniui). It is possible to minimize the dimensions by placing them in the image plane of the pupil of the optical system, but this arrangement increases the complexity of the system.

 The object of the invention is to provide means for rotating the image by 90 without the interposition of an additional element of rotation.

 The invention is remarkable in that the change in direction of said linear image of detectors is obtained by a simple change in the position of an appropriate element of said camera.

 In a first alternative embodiment, the optical axis of said objective disposed in a vertical direction is folded by said first mirror in a horizontal direction for observation in imaging mode. Said change of position consists in rotating said mosaic of detectors 90. in the horizontal plane. The optical axes of surveillance and imaging are then merged. So when a target is detected in iodine monitoring, the device must make a complete revolution to observe the target again in imaging mode, unless it makes a return movement.

 In a second variant embodiment, the optical axis of said objective disposed in a horizontal direction is folded down by said first mirror in a vertical direction. Said device further comprises, aligned on said vertical optical axis, an afocal system followed by a second plane mirror inclined at 45 which folds the optical axis again in a horizontal direction parallel to the optical axis of said objective for observation in iodine imaging. Said change of position consists in rotating said second mirror 90 about the vertical optical axis so that the optical imaging and surveillance axes are perpendicular to each other in the same horizontal plane. So when a target is detected in iodine monitoring, the device should only perform a quarter turn to observe the target again in iodine imaging.

 In this case the observations in iodine monitoring and in iodine imaging can be brought in the same direction in the same direction or in opposite directions by means of a suitably arranged mirror system.

 The following description next to the Anne xis drawings, all given by way of example, will make it clear how. the invention can be realized.

 Figure 1 illustrates the three main types of scans used in thermal imaging cameras.

 Figure 2 shows the block diagram of observation systems in standby or monitoring mode.

 FIGS. 3 and 4 represent the diagrams of known devices of cameras associating the modes of observation in imagery and in surveillance.

 Figures 5 and 6 show respectively the diagrams of a first and a second variant of devices for implementing the invention.

For the device shown in Figure 6, said observation iodines are located in perpendicular directions. In this case, FIGS. 7 to 10 show various diagrams of mirror assemblies making it possible to bring the direction and the direction of observation of said iodines according to any one of the positions below.
Figure 7 same direction and same direction,
Figure 8: same direction and opposite direction,
Figures 9 and 10: any directions.

 In FIG. 1a, a detector Dv consisting of a linear mosaic of elementary detectors is placed in a vertical position and an optico-mechanical device not shown drives the image of the detector in the horizontal direction h to carry out the line scanning.

 In FIG. 1b, a detector of the same type Dh is placed in a horizontal position and its image is drawn in the same way in the vertical direction v to carry out the trane scan.

 In FIG. 1c, a detector Dhv is made up of three rows and three columns of elementary detectors.

A more complex optico-mechanical device not shown successively drives the image of this detector according to the arrows h and v to perform the line scanning and the frame scanning.

 Figure 2 shows the block diagram of a so-called standby or monitoring device.

 An optic L forms an image D'v of a linear number of detectors Dv positioned parallel to a vertical axis w '. The detector-optical assembly rotating around the axis vv 'with a uniform angular movement, the image D'v describes the horizon along the contour C over a complete revolution or over a fraction of a revolution.

 Two devices are described below which make it possible, from a imaging observation node (campera with vertical scanning in FIG. 1b or with series-parallel scanning in FIG. 1c), to also carry out the standby or monitoring iodine in a known manner. scanning in deposit, the two types of observation can be carried out alternately.

FIG. 3 schematically represents the general optical arrangement in the system 0, X, Y, Z, OZ being the vertical direction. This device comprises - a linear mosaic of detectors D arranged in parallel
to the OY axis, or the image of a line given by an op system
tico-mechanical line scanning, - an L1 objective giving an infinity image of line D, - a vertical scanning mirror Mi oscillating around the axis
Oy, i.e. around an axis parallel to that of the li
gne D. The movements of this mirror bring about the image of the
line D perpendicular to its horizontal direction and the
device then operates in iodine imaging - An image rotation element R placed in front of the mirror M1
in the direction of OX. This rotation element allows
re rotate the line image around the OX axis.

- A means not shown ensuring the rotation of the assembly
D, L1 and Mi around the vertical axis OZ at an angular velocity
laire w constant in case the device operates in
iodine monitoring The image rotation element R places
then the image of the line in the vertical position, the
movements of the mirror Mi are stopped and the movement of ro
tation of all of the above elements around the axis
vertical results in the vertical image of the panoramic line
lying on the landscape.

 Thanks to the image rotation element R, the line D, lens L1 and scanning mirror M1 assembly can occupy any position in the OYZ plane.

 This rotation element is a conventional optical element (Péchan, Rantch prism, etc.), the dimensions of which can be minimized by inserting it into an optical system such as that shown in FIG. 4.

The elements D, L1 and M1 remaining positioned co-precEdex ent in the OXYZ coordinate system, the rotation element R is reduced to its minimum dimensions if it is placed in the plane of the image of the pupil of the system constituted by the groups of lenses G1 and G2 arranged at the front of the element R. These two groups of lenses form an afocal system whose exit pupil is in the element
A. At the rear of this element, another group of lenses G3 remakes the image of the pupil on the scanning mirror M1 so as to also minimize its dimensions.

 The afocal system G1 and G2 can have several possible magnifications so as to give, for example, different fields for monitoring and imaging.

 If the device is devoid of rotation element R, the rotation of the image must be obtained by other means, in accordance with the invention.

 A first means is indicated in FIG. 5. In FIG. 5a, the same set of elements (linear horizontal detector DA, objective L1 and scanning mirror Mr) positioned previously in the OXYZ axis system, gives a horizontal image of line DA.

 If by a mechanical device not shown, the line of detectors DA which is positioned in DB in FIG. 5b is rotated by 90 around OZ, when we pass from "imaging" mode to surveillance mode, the image D ' B then occupies a vertical position on the stage, the optical axes of said observation modes being combined.

A second means of rotating the horizontal image of the linear detector so as to bring it into the vertical position without the intervention of a rotating element is illustrated by the device shown diagrammatically in FIG. 6 and which comprises (FIG. 6a) - a linear mosaic of detectors D (or the image of a li
(analyzed by optico-mechanical means), - an objective L1 whose optical axis is horizontal, - a frame scanning mirror M1 centered in Oi whose axis of
rotation is parallel to the axis of the mosaic or to the line, - an afocal system with two magnifications and optical axis 02Z
vertical, consisting of the fixed elements LZ and L3 corresponding
at maximum magnification and moving elements Ls and
L5 fitting between elements L2 and L3 (Figures 6a
and 6b) and giving the assembly the minimum magnification, - an MzA mirror (FIG. 6a) centered in 02, inclined by 45 in
rough, folding the optical axis 0102 along 02X so as to
make it close to a horizontal direction in the plane con
holding the optical axis of L1, in the imaging position. The image of
detector on the landscape is then horizontal. The same half
black M2A, always tilted at around 45, rotates 90
around the 02Z axis so as to come in MzB (Figure 6b).

The optical axis is then directed along 02Y in position on
monitoring and the image of the detector on the landscape is verti
hold.

- an imaging window H1 on the 02X axis - a Hz monitoring window on the 02Y 'axis - a general drive device not shown in rotation
tion around the 2Z axis allows in imaging, observation
panoramic and standby, circular analysis of the landscape.

 The mirror n2 is also movable around the axis perpendicular to 2Z contained in the plane of the mirror so as to orient the optical axis in azimuth.

 In this version, the two optical axes of surveillance and imaging are perpendicular to each other which can have advantages. Indeed, in surveillance, the device rotates at a certain speed (of the order of one revolution per second). If a target is detected, the device can enter imaging mode. If the two axes are merged (case of the previous version), the device must then make a complete revolution before being placed again in the direction of the target, unless making a return movement. In the case where the two axes are separated by 90, only a quarter turn is necessary between the detection of a target and the possibility of observation.

 If the two observation axes must be parallel (with an angle equal to 0. or 180 ") variants are shown in Figures 7 and 8.

 In FIG. 7, the two axes make an angle of 0 One of the two axes (monitoring for example) is folded by a mirror M3 contained in a vertical plane, inclined by 45 in the opposite direction relative to the axis OY . These two monitoring windows H1 and H2 can be combined into one. FIGS. 7a and 7b correspond respectively to the iodine observation in imaging and in surveillance.

 In FIG. 8, the two observation axes make an angle of 180 The surveillance axis is folded by the vertical mirror M3 inclined by 45 in the direct direction relative to the axis OY. The monitoring window H2 is then parallel to the window H1. Figures 8a and 8b respectively correspond to the observation modes in imagery and surveillance.

 FIGS. 9 and 10 illustrate variants where the observation axes form any angle between them.

 In FIG. 9, the vertical mirror Hs is inclined in the direct direction of any acute angle relative to the axis OY. This observation node under surveillance is done through the H2 window.

 In FIG. 10, the vertical mirror Ms is inclined in the opposite direction by any acute angle relative to the axis OY. In this case the two observation modes are made through the same window H1.

Claims (5)

 1 Method combining the modes of observation, imagery and surveillance of a thermal camera comprising, among other elements, a linear mosaic of detectors arranged horizontally, an objective giving an infinite image of said mosaic, a first plane mirror inclined at 45 by 1 optical axis of said objective and oscillating on either side of said inclination around an axis parallel to said linear mosaic in order to carry out the vertical scanning of the landscape according to the so-called "imaging" iodine, the horizontal image of said linear mosaic of detectors then being placed in a vertical direction, the oscillating movement of said first mirror being stopped and all of said elements rotating in a uniform rotational movement around an optical axis arranged in a vertical direction in order to effect the panoramic sweep of the landscape according to the so-called standby or "surveillance" iodine, characterized in that the change in direction of said linear image of detectors is obtained by a simple change in the position of an appropriate element of said camera. 2. Method according to claim 1 in which the optical axis of said objective disposed in a vertical direction is folded by said first mirror in a horizontal direction for observation in iodine imaging, characterized in that said change of position consists in rotating said linear mosaic of detectors of 90 in the horizontal plane, the optical axes of imaging and monitoring then being merged following said horizontal direction. 3. The method of claim 1 wherein the optical axis of said objective disposed in a horizontal direction is folded by said first mirror in a vertical direction, said camera further comprising, aligned on said optical axis in vertical direction, an afocal system followed a second plane mirror inclined at 45 which again folds the optical axis in a horizontal direction parallel to the optical axis of said objective for observation in iodine imaging, characterized in that said change of position consists in rotating 900 said second mirror around said vertical optical axis so that the optical imaging and surveillance axes are perpendicular to each other in the same horizontal plane, which reduces the rotation of the camera to a quarter turn between the detection of a target in surveillance mode and its observation in iodine image. 4. Method according to claim 3, characterized in that a third plane mirror arranged vertically is inclined by 45 in the opposite direction (or in the direct direction) relative to the direction perpendicular to the optical axis of imaging so fold the optical surveillance axis 90 "to bring the two observation modes in the same direction in the same direction (or in opposite directions). 5. Method according to claim 3, characterized in that a fourth plane mirror arranged vertically is inclined at any acute angle in the opposite direction (or in the direct direction) relative to the direction perpendicular to the optical axis d imagery so as to fold back the optical axis of surveillance by an angle such that the two observation modes are brought in two different directions in the same direction (or in opposite directions).