US 3742238 A
A radiant energy display system incorporating a reflecting surface mounted for rotation about scan and interlace axes, said scan and interlace axes positioned less than 90 DEG from one another. Incoming radiant energy is scanned by the reflecting surface and reflected to a detector which is responsive to that energy. Video processing circuitry interconnecting the detector with a light source array modulates the light source array which thereby emits a modulated visible beam. This beam causes modulation of a visible light source that in turn impinges upon the back portion of the reflecting surface. The back portion of the reflecting surface provides a scan identical to the front portion and by the above process produces a visible display.
Description (OCR text may contain errors)
Hoifmal 'June 26, 1973 TW '....,.mmu Primary Examiner-Archie R. Borchelt SCANNING DISPLAY Attorney-James 0. Dixon, Andrew M. Hassell, Harold Richard G. Hoffman, II, Allen, Tex.
Levine and Ren E. Grossman  Inventor:
 Assignee: Texas Instruments Incorporated,
Dallas, Tex  ABSTRACT A radiant energy display system incorporating a reflect-  Ffled' 1970 ing surface mounted for rotation about scan and inter-  Appl. No.: 97,753 lace axes, said scan and in'terlace axes positioned less than 90 from one another. Incoming radiant energy is scanned by the reflecting surface and reflected to a deg g iyl tector which is responsive to that ene gy. Video Pro. cessing circuitry interconnecting the detector with a  Field of Search 350/1, 6, 7, h d l h h 250/833 HP 836 356/2 1g t source array mo uates t e l g t source array which thereby emits a modulated visible beam. This [5 6] References Cited beam causes modulation of a visible light source that in turn impinges upon the back portion of the reflecting UNITED STATES PATENTS surface. The back portion of the reflecting surface pro- 3,278,7 46 10/1966 Fiat 250/833 HP vides a scan identical to the front portion and by the 2,989,643 6/1961 Scanlon 250/833 HP above process produces a visible display 3,447,852 6/1969 Barlow .l 350/7 7 24 Claims, 12 Drawing Figures I (Scan AXiS 1 1'. Energy from Fargo 1:
Array mt uta 'IO lids-r El ctronics OR IN: 250/3 Scan Axis PATENTEUJUHZS 191s 3.742.238
sum 1 or 1 Detector Array Outputs To Video Electronics Interlace Axis 66 X Ewe ATTORNEY IR Energy from Target 8 CAN ANGLE C HANGE td tdB +7.5 1
..' I Time 00 I I I -7. 5 I I I I v 44 Fly. 3
t I, -t
=oN TIME PATENIED JUN 26 I973 SHEHIHIF? I Scan 0 Axis Interlaca: 6 L Axis t =de ad time t =dead time PATENTED JUN 2 8 I975 SHEEIUBFT EI K Light Source &8
Interlace Axis 66 Optical Axis 24 n a C s f 0 Top Axis
. Fig. 4
Detector Array 36 9E Interlace Axis 1 Scan Axis 64 PAIENIEDmzs ms 3.742.238
SHEET 5 BF 7 Interlace Axis 66 Scan Axis 6 L Interlace Axis 6b Scan Axis PATENTEDJUNZB I975 SHEEI B 8F 7 ll6b Interlace Scan Axis 6 Axis 66 Interlace Axis 66 TWO AXES ANGULARLY INDEXING SCANNING DISPLAY This invention relates to an optical system for collecting and focusing radiant energy and more particularly to a method and apparatus for scanning radiant energy.
Scanning systems heretofore for scanning radiant energy in two dimensions have utilized separate horizontal and vertical scanning mirrors. The h gr izo ntal s canning mirror generates a horizont aljf's'can of the objectl while-the'vertic'al scam'rnirror generates a vertical sweep to produce a raster scan in object or image space. Radiant energy incident on the horizontal scanning mirror is reflected to the vertical scanning mirror which concentrates the energy on a detector which converts the received radiation into an electrical signal for further processing.
As an alternative, a single mirror may be utilized to produce both a horizontal and vertical'scan by having the reflecting surface rotate about two orthogonal axes. f
To produce a raster scan, the mirrorjs rotated about a from a first point to a second point and then, during the retrace time, the mirror is rotated about a second or horizontal axis to produce a predetermined vertical movement prior to the next successive horizontal scan about the first vertical axis. Utilizing a single flat mirror rotating about two orthogonal axes has the disadvantage in that for applications requiring compact systems, the mounting support structures and drivers for the mirror interfere with the optical paths of the incoming radiant energy, if both sides of the mirror are to be used simultaneously.
Accordingly it is an object of the present invention to provide a method and apparatus for scanning radiant energy about two axes which are positioned less than 90 from one another to allow a compact system to be obtained.
Another object of this invention is to provide a scanning system which produces a unique interlace pattern.
A further object of this invention is to provide a scanning system which produces an interlace pattern that allows a reduction in the number of detectors and associated electronics required.
A still further object of this invention is to provide a radiant energy display system which utilizes a scanning mirror rotating about two axes which are positioned less than 90 from one another and which utilizes the same mirror for both the scanning of the incoming radiant energy as well as the scanning for the display of the visual representation of that radiant energy.
A still further object is to provide a display system which requires no synchronization.
A still further object of this invention is to provide a radiant energy display system which is small in size, weight, power consumption, complexity and is of high reliability.
Other objects and features of the invention will become more readily understood from the following detailed description and appended claims when read in conjunction with the accompany drawing, in which like reference numerals designate like parts throughout the figures thereof, and in which:
FIGS. 1A and 1B show the two perspective cutaway schematics, respectively, of the radiant energy display system according to the present invention;
FIG. 2 is a cross-section of the scanner and drive portion of the display system;
FIG. 3 illustrates the scan angle change as a function of time;
FIG. 4 is a top view of FIG. 2 depicting the relationship between the various axes and the scanner reflecting surface;
FIGS. 5-9 illustrate the scanning and interlace action according to the present invention;
FIG. 10 is the schematic of the scan mirror control and interlace circuits; and
FIG. 11 is the schematic of one video electronic channel.
Referring now to FIGS. IA, 18 and 2, a radiant energy display system in accordance with the present invention is indicated generally by the reference numeral 10 and is packaged within housing 11. This radiant energy display system converts incoming radiant energy into visible light. Thus, if the detector array in the system is sensitive to invisible electromagnetic radiation, such as infrared radiation, and the light source of the display system produces visible light, an invisible infrared image can be converted to a visible light image which can be viewed by the human eye or processed as desired. For purposes of explanation, it will be assumed that the incoming radiant energy is in the infrared region of the spectrum.
The infrared receiver portion of the display system is comprised of a lens assembly 12, a scanning assembly 14 and a detector assembly 16. The lens assembly in FIGS. IA and 1B is comprised of three lens elements which, for operation in the infrared region, may consist of three germanium elements, 18, 20 and 22. Incoming infrared energy from a target (not shown) enters along the optical axis 24 of the system, passes through lens assembly 12 and impinges upon the scanner assembly 14 which is comprised, in part, of a two-sided flat mirror 26 with the front side 28 of the mirror being utilized for the reception of infrared energy while the backside 30 of the mirror is utilized for scanning the modulated visible light from a light source to be described hereinafter. Scan mirror 26 is mounted for rotation on mirror mount 32 and is positioned nominally at an angle of 45 to optical axis 24. The incoming radiant energy is reflected from scan mirror 26 and in turn impinges upon folding mirror 34. Folding mirror 34 reflects the energy and focuses the energy on a linear array of detectors 36 which are located in a Dewar 38 for cooling the individual detector elements. Dewar 38 is located on the infrared side of the scan mirror 26 along the folded optical axis 24.
Detector 36 may comprise a plurality of infrared detectors which may be, for example, in a linear array and made of spaced mercury cadmium telluride (HgCdTe) diodes or indiumantimoide (InSb) diodes. The individual detectors may also be staggered, by further way of example. The particular material used for the detectors will be dependent upon the infrared spectrum to which the system is designed to be responsive. For example, the detector array 36 may be composed of 0.003 X 0.003 inch detector elements in a linear array which are separated by 0.003 inch. These detectors can operate at liquid nitrogen temperatures (77 K). The Dewar is composed of a cryostat 40 which is connected to a source (not shown) of high pressure nitrogen gas. This gas undergoes a pressure change which cools the gas causing the gas to condense to a liquid at 77 K at or near detector array 36. This increases the sensitivity of the detector array 36. A cryostat such as is illustrated in FIG. 1A is manufactured and sold by Air Products Incorporated.
FIG. 1B illustrates the display portion of the system 10. The output from the 174 array 36 is fed to video electronic circuitry 44, the output 46 of which is fed to light source 48. The light source may comprise, for example, a plurality of spaced light emitting diodes. The number of light emitting diodes 48 will correspond in number to the number of detectors in the linear array of detectors 36 with similar spacing therebetween. The video electronics 44 couples each detector channel with the corresponding light emitting diode 48 and provides the signal processing and auxiliary functions to modulate the output from each light emitting diode. The visible light output 50 from light emitting diodes 48 impinges upon folding mirror 52 and is transmitted through collimating lens elements 54 and 56 and is focused upon the back surface 30 of scan mirror 26. The light-emitting diode array 48 may be composed of, for example, gallium arsenide phosphide diode elements such as the type manufactured and sold by Texas Instruments Incorporated. The visible image which may be viewed by an observer along the line of sight axis 58 is a visual representation of the incoming invisible infrared energy from a target (not shown). The utilization of the same scan mirror 26 for both the receiver scan and the display scan allows for cancellation of small perturbations of mirror motion during the scanning cycle. The visual representation of the target reflected from the back portion 30 of scan mirror 26 passes through an aperture 60 in the gimbal or link member 62.
Referring now specifically to FIG. 2, it will be seen that scan mirror 26 moves about a first and second axis, namely the scan axis 64 and the interlace axis 66. Interlace axis 66 is positioned at an angle which is less than 90 from scan axis 64. As mentioned previously, scan mirror 26 is mounted at an angle of approximately 45 to the optical axis 24. The scan mirror provides the scanning for both the receiver portion and the display portion of the system 10. Vertical scan and display are effectively provided by using vertically oriented linear arrays of infrared detectors 36 and light emitting diodes 48. These elements are spaced such that a 2:1 interlace, obtained by tilting the scan mirror a few milliradians about interlace axis 66, allows a 2:1 reduction in the number of channels required in the system 10.
Horizontal scanning of the mirror 26 occurs about scan axis 64. Typically, scan mirror 26 is rotated 7.5 on either'side of scan axis 64 for a total horizontal scan of; The scan mirror may rotate at a constant velocity during the 15 horizontal scan, which will occupy typically 80 percent of the cycle time period. per cent of each time period (referred to as the dead time) may be allotted for reversing the scan mirror direction of rotation. Tilting the mirror for the interlace (to be described in more detail hereinafter) will also occur during the dead time. Mirror 26 is mounted on a gimbal or link member 62. A small, brushless d.c. torque motor provides the drive function around scan axis 64. The torque motor 68 is comprised of a stator 70 and a rotor 72. Integral with the rotor 72 is mirror clamp 74 which clamps mirror 26 to rotor 72. Threaded coupling 76 secures rotor 72 to bearing or flex pivot 78.
The mirror is attached at its upper end by way of mirror clamp 80 to a tachometer 82 which provides a feedback signal which is used for rate sensing (and described further with regard to FIG. 10). Tachometer 82 is comprised of a stator 84 and rotor 86 to which mirror clamp is mounted. Threaded coupling 88 holds rotor 86 in engagement with the bearing or flex pivot 90. Torque motor 68 which provides the horizontal scan motion for mirror 26 may be considered the scan driver. Torque motor 68 may be, for example, Model No. TQ lOY-IOP manufactured and sold by Aeroflex Incorporated.
Gimbal or link member 62 may be moved or tilted at a predetermined time in the scanning cycle (i.e., during the dead time of the scan cycle) around interlace axis 66. Link 62 is mounted to the housing 11 by way of two bearings or flex pivots 92 and 94. These flex pivots, consisting of crossed leaf springs, are characteristically rugged, have low friction and are light weight. Flex pivots 92 and 94 allow link 62 (and therefore mirror 26) to move or tilt around interlace axis 66. Solenoids 96 and 98 provide the interlace drive motion and allow the gimbal or link 62 and mirror 26 to tilt about the interlace axis upon actuation of either solenoid 96 or 98. When solenoid 96 or 98 is actuated, shafts 100 and 102, respectively will pull link 62 thereby causing the link to tilt about the interlace axis a prescribed amount (in the order of a few milliradians). Solenoid 98 is mounted to bracket 104 by bolts 106 while solenoid 96 is mounted in the same manner by bracket and bolts 107 (FIG. 1B). Stops 108 limit the motion of solenoids 96 and 98.
In FIG. 1A, it will be noted, that an extension 110 is attached to mirror mount 32 and is positioned between two tuned restoring springs 112. These restoring springs 1112 provide a significant portion of the torque required to turn around scan mirror 26 with the mirror torque motor driver 68 supplying the remainder and also making up for losses in the bearings and springs.
It should be noted that although a separate scan drive (torque motor 68) and interlace driver (solenoids 96 and 98) are illustrated in FIGS. 1 and 2, in some applications, a single driver may be utilized to obtain the desired scan and interlace motion of scan mirror 26. If a scan driver only is utilized to apply a torque T, to scan axis 64, a component of that torque will be applied to interlace axis 66 related to T by cos 0, where 0 is the angle between the interlace and scan axes. This torque then accomplishes the interlace function. If an interlace driver only is utilized to apply a torque to link member 62 and the link acquires an angular velocity, then the scan axis (which is integral with the scan mirror) will obtain that same angular velocity and the component of that angular velocity along the scan axis appears as a change in the scan rate of the mirror with respect to the housing causing the scan motion. A single driver to accomplish movement of mirror 26 may be obtained without the necessity of additional power transmission devices.
The system illustrated in FIGS. 1 and 2 is essentially an image plane scanner; by that, it is meant that the target in the object plane (not shown) remains fixed with respect to the aperture of the system while the image of that target is scanned across detector array 36. FIG. 3 illustrates the relationship between the scan angle change of mirror 26 with time while FIG. 4 illustrates a top view of FIG. 2 showing the relationship between the three axis, 24, 64 and 66 with scan mirror 26. As will be noted from FIG. 3, scan mirror 26 rotates 7 16 from its 0 position which is nominally at a 45 angle with the optical axis 24. In other words, scan mirror 26 will move through an angle between 37.5 and 52.5 with respect to the optical axis 24 as can be seen in FIG. 4. As designated in FIG. 3, the time required for mirror 26 to move i7.5 corresponds to the on time, t while the time required for scan mirror 26 to index or tilt (interlace) is designated as the dead time t,,. The on time of the scanner may be approximately 80% while the dead time may be on the order of 20% of the total duty cycle of the scanner. It will be noted from FIG. 3 that a linear scan (constant angular velocity or scan rate) is utilized during the on time of the scanner. A sinusoidal scan motion could have been used but the variation in target dwell time (i.e., the time period that the image of a resolution sized target is over an individual detector) with scan angle would result in varying gain across the display image. The dead time (t,,) of each time period is allotted for reversing the direction of rotation of scan mirror 26 and further for tilting mirror 26 for interlace.
FIGS. -9 illustrate in detail the scanning and interlace action according to the present invention. As has been noted previously, detector array 36 consists of a plurality of individual detector elements in a linear array each spaced one detector width away from the next element. The number of light source elements in light source 48 corresponds to the number of elements in detector array 36 with substantially the same spacing therebetween. In other words, by not using a continuous row of elements, that is, using only one-half that number, the number of detector channels is reduced by one-half as well as the associated video electronic circuitry 44, thereby requiring half the number of light source elements 48. FIGS. 5-9 have removed certain elements illustrated in FIGS. 1 and 2 for purposes of clarity. For example, folding mirrors 34 and 52 are not shown and the radiant energy impinging upon mirror 26 is shown in FIGS. 5-9 as impinging directly upon detector array 36.
FIG. 5 illustrates the scanning mirror 26 at nominally a 45 angle to optical axis 24. For purposes of explanation, incoming radiant energy passes through lens elements 18-22 and impinges upon mirror 26 at 114. This energy (which is assumed to be infrared energy) is reflected from mirror 26 and impinges upon detector array 36. The image of the target (not shown) is bounded by the area 116 which partially overlays detector array 36. It will be noted that the area 116 of the target may be broken into two groups of rows of information 116a and l16b. In the position illustrated in FIG. 5, rows 116a will overlay the individual detector elements 36 while rows of information l16b do not overlay any individual detector elements. Accordingly, the information contained in rows 1l6b will not be obtained during the first sweep of mirror 26. The image point on optical axis 24 is shown on a detector as resolution element 118.
Referring now to FIG. 6, it will be seen that mirror 26 is moved 7.5 from its position shown in FIG. 5. The original position of the scan mirror shown in FIG. 5 is dotted in FIGS. 6-9, for reference purposes. This 7.5 excursion of scan mirror 26 corresponds to the time t shown in FIG. 3. The information contained in rows 116a scans over the individual detector elements 36 and the path traversed during the scan by individual resolution element 118 is shown as path 120. As mirror 26 moves to the position shown in FIG. 6, it will impact one of the two restoring springs 112 (FIG. 1A) which will help it to reverse its direction. This reversal of direction, as well as the indexing or interlacing of mirror 26, occurs during the first dead time illustrated in FIG. 3 as m,
FIG. 10 illustrates the scan mirror control and interlace circuit used to drive torque motor 68 and solenoids 96 and 98 (shown in FIGS. 1A). Torque motor 68 drives scan mirror 26 through the i7.5 scan. Tachometer 82 (shown in FIG. 2 and schematically in FIG. 9) is mechanically coupled to torque motor 68 and the tachometer electrical output 122 is fed to an inverting amplifier 124 as well as through resistor 126 back to one input of comparator 128. The output of inverting amplifier 124 is fed through resistor 130 to the same input of comparator 128 as resistor 126 while resistor 132 is also fed to this common terminal. The other side of resistor 132 is connected to the output of comparator 128. Comparator 128 provides a drive and a DC reference voltage whose polarity depends upon the scan direction. Resistor 130 determines the scan velocity and period. In other words, the scan mirror control circuit of FIG. 10 provides the appropriate voltage to torque motor 68 during the on time of the scanner.
FIG. 7 illustrates the index and tilting of mirror 26 during the dead time a, It will be noted from FIG. 7 that target area 116 is effectively moved down, with respect to the individual detectors indexed or interlaced one detector width. In other words, row 116a is no longer in line to pass over one of the detector elements 36 while row ll6b is now in a position to pass over one of detector elements 36. This is shown more clearly by the path 134 traversed by resolution element 118. Mirror 26, to effect this interlace, is moved or tilted a predetermined amount around interlace axis 66. This movement is generated by solenoid 96 activating shaft 100 (FIG. 1A).
The interlace circuit shown in FIG. 10 activates solenoids 96 and 98 at the appropriate time. The interlace circuit electrically activates solenoid 96 during dead time ta, (FIG. 3). A timing signal 136 from amplifier 124 in FIG. 10 is connected to function generators I38 and 140 which, in turn, are respectively connected to solenoid drivers 142 and 144. The timing signal 136 actuates function generator 138 which applies to solenoid 96 an acceleration, deacceleration and hold signal for a predetermined time period. Solenoid 96 pulls shaft 100 which rotates or tilts link member 62 around interlace axis 66.
FIG. 8 illustrates the scan by mirror 26 as it moves through the 15 scan in FIG. 3 shown at time t in the tilted or interlaced position. In this position, resolution element 118 will traverse a path shown at 146. Scan mirror 26 in traversing the path 146 will scan in the opposite direction from path 120.
FIG. 9 illustrates the position of the scan mirror after it has been indexed or interlaced during the dead time 4 (in FIG. 3). During this time period, the row 116a of target information is once again in a position to be scanned across the individual detector elements 36 while the row 1161; of target information will not be scanned across any detector elements. Resolution element 118 traverses a path 148 during the interlacing time period id, During this time period 0.1, the timing signal 136 shown in FIG. 10 actuates function generator 140 which, in turn, excites solenoid 98. Solenoid 98 pulls shaft 100 which tilts link or gimbaled member 62 around interlace axis 66 in the opposite direction than that provided by solenoid 96 and shaft 100.
Thus it can be seen that when mirror 26 completes a full cycle, an exemplary resolution element 118 will traverse essentially a parallelogram whose sides are made up of paths 120, 134, 146 and 148. Paths 120 and 146 are perpendicular to scan axis 64 while paths 134 and 148 are perpendicular to interlace axis 66.
By the interlace method described herein, the total image of the target area 116 is traversed across detector elements 36 when scan mirror 26 completes one cycle of operation. By utilizing this interlacing technique, that is tilting mirror 26 about interlace axis 66 during the dead time t,,, only one-half the number of detector elements are required, compared with the no interlace situation. After the target is scanned across detector array 36 as described hereinabove, appropriate video electronic circuitry 44 (shown in block form in FIG. 1B) processes the detector information and modulates the light source array 48. Video electronic circuitry 44 couples each detector element in array 36 with the corresponding light emitting diode element in light array 48. As shown in FIG. 11, the output of one detector element in array 36 goes through preamplifier circuit 150 and then through an intermediate stage of amplification in amplifier circuit 152. The output from the second stage 152 of amplification is then in turn coupled to the light emitting diode driver circuit 154 which modulates the light output from light emitting diode element 48. Light emitting diode drive circuit 154 will provide a current through light emitting diode element 48 which is a function of the amount of radiant energy impinging upon detector element 36.
As shown in FIG. 1B, the visible light output 50 from light emitting diodes 48 is reflected from folding mirror 52, transmitted through collimating lens elements 54 and 56 and is transmitted to the back portion 30 of scan mirror 26. The visible light transmitted from the back portion 30 of mirror 26 will be scanned and interlaced in the same manner as described hereinabove with regard to the incoming radiant energy impinging on the front portion 28 of mirror 26 to form a visible image. For this reason, no synchronization is required between the receiver scan gathered on the front portion 28 of mirror 26 and the display scan generated upon the back portion 30 of mirror 26. In order words, the utilization of the same scan mirror 26 for both receiver scan and display scan allows for cancellation of small perturbations of mirror motion during the scanning cycle shown in FIG. 3. The visible image which may be viewed by an observer along the line of sight axis 58 in FIG. 1B is a visual representation of the incoming infrared energy. Accordingly, this radiant energy display system will convert invisible radiant energy to a visible analog of that radiant energy.
Although a preferred embodiment of the invention has been described in detail, it is to be understood that various changes, substitutions and modifications of the invention may be suggested to one skilled in the art, and it is intended to encompass such changes, substitutions or modifications which do not depart from the spirit and scope of the invention as is defined by the appended claims.
What is claimed is:
1. An apparatus for scanning radiant energy comprisa. a radiant energy reflecting surface;
b. a first pivotal means supporting said reflecting surface operatively to produce a scan pattern;
0. a second pivotal means supporting said reflecting surface at an angle less than from said first pivotal means operatively to produce an interlace scan; and
d. means for moving said radiant energy reflecting surface about said first and second pivotal means for scanning said radiant energy.
2. An apparatus for scanning radiant energy comprising:
a. a radiant energy reflecting surface;
b. first pivotal support means, said first pivotal support means supporting said reflecting surface in a vertical plane for producing a horizontal scan;
c. second pivotal support means, said second pivotal support means supporting said reflecting surface at an angle less than 90 from said first pivotal support means to produce an interlace horizontal scan;
d. means for rotating said radiant energy reflecting surface about said pivotal support means, and for tilting said radiant energy reflecting surface about said second pivotal support means; and
e. detector means for selectively receiving the radiant energy from said reflecting surface and producing an output signal that varies with the radiant energy incident thereon.
3. A scanning apparatus according to claim 2 wherein said reflecting surface is a flat mirror.
4. A scanning apparatus according to claim 2 wherein said detector means is a linear array.
5. A scanning apparatus according to claim 2 wherein said detector means is a linear array of spaced mercury cadmium telluride detectors.
6. A scanning apparatus according to claim 2 wherein said detector means is a linear array of spaced indium-antimonide detectors.
7. A scanning apparatus for reflecting radiant energy comprising:
a. a radiant energy reflecting surface;
b. first pivotal support means, said first pivotal support means supporting said reflecting surface in a vertical plane for producing a horizontal scan;
c. second pivotal support means, said second pivotal support means supporting said reflecting surface at an angle less than 90 from said first pivotal support means to produce an interlace horizontal scan; and
d. means for rotating said reflecting surface about said first pivotal support to produce a first scan in one direction from one point to another point, and for tilting about said second pivotal support to a second scan position and counter-rotating said refleeting surface about said first pivotal support to produce a second scan to form substantially a parallelogram interlace scan pattern.
8. A radiant energy display system comprising:
a. a radiant energy reflecting means having front and back reflecting surfaces;
b. first pivotal support means, said first pivotal support means supporting said reflecting surfaces in a vertical plane for producing a horizontal scan;
c. second pivotal support means, said second pivotai support means supporting said reflecting surfaces at an angle less than 90 from said first pivotal support means to produce an interlace horizontal scan;
d. means for rotating said reflecting means about said first pivotal means, tilting said reflecting means about said second pivotal means and counterrotating said reflecting means about said first pivotal means to produce an interlaced pattern;
. detector means for receiving the interlace pattern of radiant energy and producing an output signal that varies with the radiant energy incident thereon; and
. light source means responsive to said output signal for producing a visible light beam representative of said radiant energy, said visible light beam being scanned by the back surface of said reflecting means to produce a visible display.
9. An apparatus for scanning infrared energy comprising:
a. a mirror;
b. first pivotal support member, said first pivotal support member supporting said mirror in a vertical plane for producing a horizontal scan;
c. second pivotal support member, said second pivotal support member supporting said mirror at an angle less than 90 from said first pivotal support member to produce an interlace horizontal scan;
(1. means for rotating said mirror about said first pivotal member in first and second directions to produce a reciprocating scan movement;
e. means for tilting said mirror about the second pivotal members during dead time of the scanning movement; and
f. a linear array of spaced infrared detectors positioned so as to have focused thereon said parallelogram scan of said infrared energy and producing an output signal that varies with said energy.
10. An apparatus according to claim 9 further including:
light source means responsive to said detector output signal for producing a visible light beam representative of said infrared energy, said light beam being scanned by the back surface of said mirror to produce a visible display.
11. An apparatus according to claim 9 wherein said means for tilting is a gimbal member.
12. An apparatus according to claim 11 wherein means for rotating is a torque motor and said gimbal member is tilted by solenoid driver means coupled thereto.
13. An apparatus according to claim 9 wherein said scan axis is positioned 90 to the optical axis of said system and said mirror is nominally at 45 to said optical axis.
14. An apparatus according to claim 9 wherein said mirror is flat.
15. An apparatus according to claim 9 wherein said detectors are spaced mercury cadmium telluride.
16. An apparatus according to claim 9 wherein said detector means is a linear array of spaced indiumantimonide.
17. An apparatus according to claim 10 wherein said light source means is a plurality of light emitting diodes.
18. An apparatus according to claim 9 further including spring means which engage said mirror after rotation thereof in said first and second direction.
19. An apparatus for scanning radiant energy comprising:
a. a housing;
b. a mirror;
c. a C-shaped member having first pivots adjacent each end for rotatably supporting said mirror within the C-shaped member, and second pivots spaced less than from the first pivots for tilting said C-shaped member within the housing;
d. driver means in line with said first pivots for rotating said mirror in first and second scan directions; and
e. means for tilting said C-shaped member and said mirror about said second pivots in first and second directions to produce substantially a parallelogram scan pattern.
20. An apparatus according to claim 19 further including a linear array of spaced infrared detector elements positioned so as to have focused thereon said parallelogram scan of said infrared energy and producing an output signal therefrom.
21. An apparatus according to claim 20 wherein said detector elements are spaced one detector element width from the other.
22. An apparatus according to claim 20 further including a linear array of spaced light source elements, each of said light source elements responsive to the output signal from each of the corresponding detector elements, said light source elements producing a visible image of said infrared energy.
23. An apparatus according to claim 22 wherein said C-shaped member has a first aperture in one arm thereof for accommodating said driver means and a second aperture therein for observing the visible image.
24. An apparatus according to claim 22 wherein said driver means is a torque motor and said means for tilting is at least one solenoid coupled to said C-shaped member.