Dec. 19, 1961
`
`M. MINSKY
`MICROSCOPY APPARATUS
`
`Filed Nov. 7, 1957
`
`3,013,467
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`28
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`FIG. I.
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`ft
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`FIG. 2.
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`48
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`INVENTOR.
`MAR.VIN Ml NSIKY
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`BY~°±,!:::r
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`United States Patent Office
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`3,013,467
`Patented Dec. 19, 1961
`
`1
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`3,013,467
`MICROSCOPY APPARATUS
`Marvin Minsky, 44 Bowdoin St., Cambridge, Mass.
`Filed Nov. 7, 1957, Ser. No. 695,107
`(CI. 88-14)
`4 Claims.
`
`My invention relates to a new and improved electronic
`microscope apparatus and to a novel apparatus for mi(cid:173)
`croscopy.
`According to my invention, ·I utilize an optical system
`including a means for producing a point source of light.
`Light from this point source is focused upon a specimen
`to be enlarged to illuminate a point observation field in(cid:173)
`cluded in the specimen. The illuminated point is then
`focused as an image of the point upon a pinhole aperture,
`and the light intensity of the image measured by a photo(cid:173)
`sensitive device. While the optical system remains fixed,
`means are provided to move the specimen in a selected
`pattern across the focal point of illumination so that a
`selected area of the specimen traverses and is examined by
`the point of light. This scanning pattern traversed by
`the specimen is reproduced by an identical scanning pat(cid:173)
`tern or raster upon a display device, such as a cathode ray
`tube, to which is also fed the signal from the photo(cid:173)
`sensitive device. The raster area greatly exceeds the se- 25
`lected area of the specimen. As a result, an image of the
`second specimen area is reproduced on a highly enlarged
`scale in the raster of the cathode ray tube.
`An object of the invention is to provide a microscope
`system in which simple objectives may be used, at the
`same time resulting in a resolving power unattainable in
`conventional microscopic apparatus and by conventional
`microscopy methods.
`Another object of the invention is the provision of a
`microscopic optical system capable of rejecting all scat(cid:173)
`tered light except that emanating from the central focal
`point, i.e. the illuminated point of the specimen. Such
`high selectivity of light reduces blurring, increases effec(cid:173)
`tive resolution, and permits unusually clear examination
`of thick and scattered specimens.
`A further object of the invention is the provision of
`a microscopic optical system which permits the use of
`new and simplified techniques in the application of vari,
`abie aperture stops and optical contrast methods.
`Additional objects and advantages of the invention will
`be apparent in the course of the following specification
`when taken in conjunction with the accompanying draw(cid:173)
`ings, in which:
`FIG. 1 is a diagrammatic view of an optical system
`arranged in accordance with my invention;
`FIG. 2 is an elevational view of the apparatus utilized
`in scanning the specimen, portions of said apparatus be(cid:173)
`ing broken away to reveal inner construction, and the
`electrical components being shown 'diagrammatically; and,
`FIG. 3 is a diagrammatic view of a modified form of
`optical system in accordance with my invention.
`In its broad aspects, the invention herein comprises two
`novel systems: ( 1) the optical system, which may be
`designated as a "double focusing" system illuminating a
`point on the specimen and for reproducing an image of
`an illuminated point of the specimen at a pinhole aper(cid:173)
`ture; and (2) the mechanical-electrical system for moving
`the specimen in a scanning pattern to traverse the focal
`point of illumination and to produce a synchronized, iden(cid:173)
`tical scanning pattern on the display device. This sec(cid:173)
`ond system may be termed a "stage scanning" system.
`For clarity, each of these systems will be separately dis(cid:173)
`cussed.
`
`Double focusing optical system
`FIGS. 1 and 3 respectively show two embodiments of
`the optical system of the microscope both of which func-
`
`2
`tion in an identical manner and can produce identical
`results.
`FIG. 1 shows, by way of illustration, a light somce 10
`which may be in the form of an electric light bulb, or
`5 other light source suitable for use in microscopy. The
`bulb 10 has the usual reflector 12.
`Mounted in front of the light source 10 is a screening
`device, which; in its simplest form may be a plate or wall
`1,t having a pinhole aperture 16 in registry with the light
`10 source 10. TI1e structure described above is shown for
`clarity of illustration, it being understood that any suit(cid:173)
`able means for producing light from a point source may
`be utilized according to the invention.
`It is desirable,
`however, to obtain the closest possible approximation of
`15 a point source of light, the power of resolution of the
`microscope depending upon the degree to which a geo(cid:173)
`metric point can be approximated.
`The "double focusing" system in this embodiment of
`the invention is provided by a pair of objective lenses 18
`20 and 20. The lens 18 focuses the light emanating from the
`pinhole aperture 16 upon the specimen 22 to produce an
`illuminated point on said specimen, and the lens 20 focuses
`this illuminated specimen point upon a second pinhole
`aperture 26.
`The objective lens 18 is shown as a symmetric double-
`convex lens (but may be any simple or complex focusing
`device) located between the plate or wall 14 and the
`specimen 22. The second lens 20 is of similar shape and
`is located on the opposite side of the specimen 22, be-
`30 tween said specimen and a second plate or wall 24. The
`plate or wall 24 contains a pinhole aperture 26 which is
`in alignment with the aperture 16 of plate 14.
`Located behind the plate or wall 24, in registry with
`the pinhole aperture 26, is a photo-sensitive device 28,
`35 which may be a photo-electric cell. The device 28 is
`capable of measuring the intensity of the light passing
`through the pinhole aperture 26.
`The point source of light A, produced at the pinhole
`aperture 16 becomes a divergent beam indicated by the
`40 extreme rays B, B in the path of which the lens 18 is
`In passing through the lens 18, the divergent
`located.
`beam becomes a convergent beam indicated by ·the ex(cid:173)
`treme rays C, C, this beam converging to its focal point
`D. Expressed in different terms, the lens 18 produces an
`45 axial cone of light B, B having an apex D. The apex or
`focal point D, approximates a point of light, depending
`upon the size of the light source 16. The part of the
`specimen 22 to be examined is located at this focal point
`D, so that there is produced a point of illumination on the
`50 desired part of the specimen 22.
`The illuminated point D of specimen 22 becomes a
`divergent beam defined by extreme rays E, E, which passes
`through the second objective lens 20 to become a con(cid:173)
`vergent beam defined by extreme rays F, F. The beam
`55 F, F converges to a focal point G, which may be regarded
`as the apex of the axial cone of light F, F. The pinhole
`aperture 26 of plate 24 is located at this focal point G, and
`the light passing through the aperture 26 is received by the
`photo-electric cell 28 and converted to an electrical cur-
`60 rent which is fed to the cathode ray tube. The intensity of
`the point of light D on the specimen 22 is therefore repro(cid:173)
`duced as a light spot of the same relative intensity on the
`cathode ray tube, as described hereinafter.
`Under the heading "Stage Scanning System" below, I
`65 shall describe means for scanning an area of the specimen
`with the point of illumination D. This is accomplished
`by moving the specimen 22 relative to the light spot D
`in a designated scanning pattern, all other portions of the
`70 optical system remaining fixed and immovable. Means are
`also provided for producing an identical scanning pat(cid:173)
`tern or raster on the cathode ray tube, so that a point•
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`by-point image of the scanned specimen area is repro(cid:173)
`duced on the cathode ray raster.
`The optical axis of the system shown in FIG. 1 is rep(cid:173)
`resented by the line O A. The pinhole apertures 16 and
`26, and the centers of lenses 18 and 20, all lie upon 5
`the optical axis O A. Thus, the point source of light A,
`and the specimen point of illumination D both originate
`on the optical axis O A, while the point image G tenni(cid:173)
`It will therefore be observed
`nates on the optical axis.
`that all of the light rays accepted by the photo-electric cell
`28 must pass through the specimen 22 at point D on the
`optical axis, and pass again through the optical axis at
`point G. Light scatterend from points other than the
`point of specimen illumination D is rejected from the
`optical system to an extent never heretofore realized.
`Such scattered rays may pass through and be refracted
`by Jens 20, but will not be directed to the pinhole aper(cid:173)
`ture. Rather, the defracted rays will strike the body of
`plate 24, and be rejected from the optical system. Such
`rays can reenter the optical system only by again being
`scattered, and the possibility of thc!ir being scattered
`along a line through point D on the optical axis O A is
`exceedingly remote. The second pinhole aperture 26
`increases the optical resolution of the system by its action
`of squaring the intensity pattern distribution of the im(cid:173)
`age diffraction.
`It can be shown that this results in a
`sharpened central diffraction zone with reduced high order
`zones.
`This high degree of selectivity afforded by the optical
`system results in a minimum of blurring, increase in sig(cid:173)
`nal-to-noise ratio, increase in effective resolution, and the
`possibility of high resolution light microscopy through
`unusually thick and highly-scattered specimens.
`It will also be apparent to those skilled in the art that
`the double focusing feature of the optical system enables
`the use of extremely simple lenses as compared to the
`usual microscopic objectives.
`In conventional micro(cid:173)
`scopy, each lens is required to bring into focus simultane(cid:173)
`ously every point in the field of view. Such a require(cid:173)
`ment has never been fully realized when the field of view
`comprises an area.
`In the optical system of the instant
`invention, however, the lenses are merely required to bring
`the light originating at a single point on the optical axis
`into focus at another point on the optical axis. The lens
`design is thus relatively simple and the lenses need only
`be corrected for spherical abberation and possibly for
`longitudinal chromatic abberation. The usual micro(cid:173)
`scope lens corrections for coma, astigmatism, curvature of
`field, field distortion, and lateral chromatic abberation
`may be dispensed with.
`Because of the simple design of the lenses, microscopic
`objectives for the optical system may be constructed with
`considerably higher relative apertures and with higher re(cid:173)
`solving power than has hitherto been attainable. The
`lenses can be made of larger size than conventional micro(cid:173)
`scope lenses with greater working distances.
`Since the entire field of view of the optical system con(cid:173)
`stitutes a single point, the system has the novel advan(cid:173)
`tage of affording a potential aperture stop location at
`every position along the optical axis. Thus a continu-
`ously variable aperture stop can be provided by merely
`moving an annulus of fixed size along the optical axis.
`This eliminates the necessity of using an annulus of ad(cid:173)
`justable size, in the nature of an iris diaphragm, such as is
`utilized in conventional systems, and allows for continu(cid:173)
`ous variation in the effective aperture of the annulus with(cid:173)
`out interruption of work.
`Many of the techniques for microscopic investigation
`may be materially simplified in accordance with the pres-
`ent invention, as will occur to those skilled in the art. In
`that the present system involves the use of only one set of
`rays, that is the rays passing through any one point on
`the optic axis, it is possible to produce complex contrast
`effects with comparatively simple equipme.nt. Any con(cid:173)
`trast techniques which will work on the very small region 75
`
`4
`can be used to investigate an extended specimen. This
`is in marked contrast to the use of conventional systems
`which require special techniques and equipment to in-
`vestigate a large area.
`Specifically, in conventional techniques the contrast sys-
`tem is to operate in exactly the same manner simultane•
`ously in all points of the field of view wherein optical
`conditions vary markedly. This often requires great pre(cid:173)
`cision and in many systems necessitates the use of special
`10 stops situated at inconvenient and often inaccessible lo(cid:173)
`cations of the optical system.
`Illustrative of the advan(cid:173)
`ta oes realized by the present system are the facility for
`da;k field microscopy. For example, in the system illus(cid:173)
`trated in FIG. I, dark field investigation may be achieved
`15 by placing an appropriately shaped stop anywhere be(cid:173)
`tween the pinhole aperture 16 and the objective 18 and
`a complementary aperture at a corresponding position be(cid:173)
`tween the objective 20 and the pinhole aperture 26.
`Those skilled in the art will appreciate that the optical
`20 system of my invention has the property that every p!ane
`across the optical axis is a potential pure aperture stop,
`whereas in a conventional system, there are never more
`than a very few such locations. Now in a conventional
`system, if it is desired to introduce special purpose aper-
`25 ture stops, such as are used for phase-contrast or dark(cid:173)
`field microscopy, it is required that said special purpose
`stops be introduced in one of the very few pure aperture
`piane locations, and this imposes severe requirements of
`precision on the manufacture of the stops, and in some
`30 cases results in inconvenient or impossible requirements
`on the lens designs. If more than a few different stops
`are required, then there are simply not enough such loca(cid:173)
`tions in a conventional microscopic system for place(cid:173)
`ment of the stops. In the system of this invention, it is
`35 possible to provide for any number of stops by simply
`lengthening the distance between the elements of the sys(cid:173)
`tem. This results in an instrument of unprecedented flexi(cid:173)
`bility and convenience.
`Because of the fact that the optical system is identical
`40 for each point of the field of view being scanned, this
`system is especially well suited for making quantitative
`studies of the optical properties of the specimen.
`In a
`conventional system, the optical properties of the system
`may vary from point to point of the field of view. This
`45 makes it necessary to calibrate separately the optical prop(cid:173)
`erties of the microscope for many points of the field of
`view, if accurate measurements are to be made. In my
`system, the identical system is used at each point of the
`specimen, making point-to-point calibration unnecessary.
`50 Still other advantages will occur to those skilled in the art.
`FIG. 3 shows a modified arrangement of the optical
`system in which a single objective 11 is used, instead of
`the two objectives 18 and 20. In this arrangement, the
`specimen 22 is mounted upon the reflective surface of a
`55 mirror 15. A beam-splitting plate 17 is interposed between
`the collimating plate or wall 14 and the lens 11. The
`reflective surface of the beam-splitting plate 17 faces the
`lens 11, while the transparent surface of plate 17 faces
`the pinhole aperture 16.
`The light reflected from bulb 10 by reflector 12 is
`colimated by the pinhole aperture 16 of plate 14 to pro(cid:173)
`vide the point source of light A. The divergent beam B,
`B passes through the beam splitting plate 17 and then
`through lens 11, becoming convergent beam C, C. The
`65 focal point D of the beam C, C is located on the specimen
`22, and becomes the divergent beam E, E which is re(cid:173)
`flected from the mirror 15 back through the Jens 11.
`Lens 11 forms the convergent beam F, F which is re(cid:173)
`flected perpendicularly from the beam-splitting plate 17
`70 as indicated by beams F', F' which converge to their focal
`point G at the pinhole aperture 26 of plate 24. The photo(cid:173)
`electric cell 28 is located in alignment with the aperture
`26 to measure the intensity of the light passing there-
`through.
`While the beam-splitting plate is positioned at a 45 •
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`angle to the vertical in order to reflect the beam Jl', F'
`perpendicularly to the beam B, B it may still be con(cid:173)
`sidered that the ultimate focal point or image point G is
`located on the optical axis of the system, and the pinhole
`aperture 26 operates as previously described to prevent
`scattered rays not originating at point D from being re(cid:173)
`ceived by the photoelectric cell 28.
`Stage scanning system
`FIG. 2 shows the structure for producing the "stage
`scanning," in which the specimen 22 is moved in a scan(cid:173)
`ning pattern relative to the optical system. While the
`invention herein contemplates the use of many and varied
`types of scanning patterns, the simplest and most conven(cid:173)
`ient form appears to be the usual form of oscilloswpe 15
`raster composed of parallel horizontal lines. The struc(cid:173)
`ture shown in FIG. 2 is therefore illustrated as a preferred
`embodiment capable of producing a scanning pattern of
`the point of light on the specimen which corresponds to
`this raster. That is to say, the specimen is moved rapidly 20
`in both a horizontal and vertical direction in such a
`manner that it traverses the light beam focal point in
`synchronization with the oscilloscope raster.
`In FIG. 2, the specimen 22 is shown mounted on a
`tuning fork 30 or other plate or member capable of vi- 25
`brating at an ascertained frequency upon being excited.
`The tuning fork 30 is suspended at its nodes from depend-
`ing arms 36, 38 of a frame 40. The frame 40 is L-shaped
`as shown, having terminal legs 42, 44. An electromagnet
`46 is fixedly mounted on frame 40, adjacent to and above 30
`the center of the tuning fork. 30, the electromagnet 46
`being connected by leads 48, 50 to an oscillator 52.
`The electromagnet 46· is operable under the influence
`of the oscillator 52 to excite the metal plate 30 at its
`natural frequency causing the specimen 22 to vibrate in a 35
`vertical direction. However excitation of the plate 30 at
`the natural frequency is not essential and in some instances
`it may be desirable to adjust the frequency of excitation.
`A second electromagnet 54 is mounted on the frame 40,
`as on the frame leg 44 shown in FIG. 2, closely proxi- 40
`mate to, and facing one end of the plate 30. The energizing
`circuit for this electromagnet 54 is fed through a saw-tooth
`oscillator 56 by leads 58 and 60. The saw-tooth oscillator
`56 functions to reciprocate the entire plate 30 horizontally,
`this horizontal movement combining with the vertical 45
`vibratory movement of plate 30 to produce a scanning
`pattern over a selected area of the specimen 22. This
`scanned area is indicated schematically and on an en(cid:173)
`larged scale as numeral 22a in FIG. 2. The horizontal
`motion of plate 30 is dampened by the action of viscous 50
`damping material 32 which lines the areas of the depend-
`ing frame arms 36 and 38 upon which the member 30 is
`suspended.
`The energizing circuit between the oscillator 52 and
`electromagnet 46 is connected by leads 70, 72 in parallel 55
`to the vertical input terminals 62, 64 of an oscilloscope
`66 having a cathode ray tube 68. Similarly, the ener(cid:173)
`gizing circuit for the electromagnet 154 is connected in
`parallel to the horizontal input terminals 74, 76 of oscil(cid:173)
`loscope 66 by leads 78, 80. There is thus produced on 60
`the face of cathode ray tube 68 a raster 82, the vertical
`and horizontal components of which are synchronized
`to the vertical and horizontal movement of the specimen
`22. The vertical and horizontal scanning amplitudes of
`the cathode ray tube raster can be made very much 65
`greater than the corresponding scanning amplitudes of
`the illuminated point field, as may be appreciated by
`comparing the dimensions of raster 82 with those of the
`specimen area 122a. This results in great magnification
`of the specimen area when an image thereof is reproduced 70
`within the boundaries of the raster.
`To supply the signal to the raster 82, the leads 84, 86
`of the photo-electric cell 28 are connected through an
`amplifier 83 to the terminals 90, 92 of the cathode ray
`tube grid circuit. Thus, the intensity of the point of 75
`
`6
`light at any particular part of the scanned specimen area
`is reproduced by the cathode ray spot at the correspond(cid:173)
`ing position on the raster 82, and · a highly magnified
`image of the specimen area is thereby reproduced on the
`cathode ray tube.
`In the "stage-scanning" system described, there is no
`necessity that the plane of the specimen being examined
`be perpendicular to the optical axis of the instrument or
`In fact, the motion of scanning may be
`to the mount.
`IO made to include a component along or parallel to the
`optical axis, limited only to the working distance of the
`objectives. This is a feature not found in conventional
`microscopes.
`The scanning structure should also include adjustment
`means for selecting an area of the specimen to be
`scanned. Such adjustment means may be of any type
`suitable to move the frame 40 vertically and horizontally.
`One such means is shown in FIG. 2, as including a verti(cid:173)
`cal adjustment member 94 and a horizontal adjustment
`member 96, both mounted on a flat base 98.
`The vertical adjustment member 94 is in the form of
`an elongated horizontal member 100 having at one end
`a pointed depending leg 102 resting upon the base 98,
`and an adjusting screw 104 turnably mounted at the
`other end. The adjusting screw 104 has a pointed end
`106 which engages the base 98. The bottom end of
`frame leg 44 is shaped to receive a ball 108 which is
`mounted to roll along a slot 110 in the top surface of
`the horizontal member 100. The screw 104 may be
`turned in either direction to raise or lower its adjacent
`end of the horizontal member 100 and thereby to raise
`or lower the frame 40.
`The horizontal adjustment member 96 includes a link
`112 which is pivoted at its lower end to a fixed base ex(cid:173)
`tension U4 by pivot 116. The top end of the link 112
`is connected to the bottom of frame leg 42 by pivot 118.
`The link 112 has a central perpendicular arm 120 in
`which an adjusting screw 122 is vertically mounted. The
`bottom pointed end of screw 122 rests upon the base 98.
`Turning of the screw 122 upwardly or downwardly in
`the arm 120 will cause the link 112 to pivot angularly,
`which pivoting movement causes horizontal movement
`of the frame 40. This horizontal movement of frame
`40 is permitted by the rolling movement of ball 108 in
`the slot 110.
`The term "light" in this description and in the appended
`claims is intended to be broadly construed since my
`device may employ ultra-violet light, :provided, of course,
`that appropriate objective lenses capable of focusing such
`radiation upon an irradiated point of the specimen are
`employed.
`In this manner it is contemplated that the
`present invention may be used to examine an internal
`portion of a specimen which is opaque to visible radiation.
`While preferred embodiments of the invention have
`been shown and described herein, it is obvious that nu(cid:173)
`merous additions, changes and omissions may be made
`in these embodiments without departing from the spirit
`and scope of the invention as defined by the claims.
`What I claim is:
`1. In a picture-producing device including means for
`focusing a beam of radiation on a specimen, a radiation
`detector adapted to receive said beam of radiation after
`the latter impinges on said specimen and to produce an
`output proportional to the intensity of radiation thus
`received, means for tracing images on a raster pattern
`having mutually transverse tracing components, and means
`connecting said image-tracing means to receive the out(cid:173)
`put of said radiation detector to reproduce images propor(cid:173)
`tional in intensity to the output of said radiation detector,
`a support for said specimen, means mounting said speci(cid:173)
`men support for movement in two mutually transverse
`directions, a pair of means each adapted to vibrate said
`specimen support in a separate one of said mutually
`transverse directions for scanning said beam of radiation
`over an area of said specimen, means connecting one of
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`said vibrating means for synchronization with one of
`said tracing components and the other of said vibrating
`means for synchronization with the other of said tracing
`components to synchronize the scanning vibrations of
`said specimen support with said raster pattern.
`2. A picture-producing device comprising a support for
`a specimen, means for focusing a beam of radiation on
`said specimen, a radiation detector adapted to receive
`said beam of radiation after the latter impinges on said
`specimen and to produce an electrical output proportional
`to the intensity of radiation thus received, an oscilloscope
`having horizontal and vertical inputs, means connecting
`said oscilloscope to the output of said radiation detector
`to reproduce images proportional in intensity to the out(cid:173)
`put of said radiation detector, means mounting said spe(cid:173)
`cimen support for movement in two mutually transverse
`directions, a pair of electrically driven means each adapted
`to vibrate said specimen support in a separate one of said
`mutually transverse directions for scanning said beam of
`radiation over an area of said specimen, means connecting
`one of said vibrating means to said horizontal input and
`the other of said vibrating means to said vertical input
`in a manner to synchronize the scanning vibrations of
`said specimen support with the raster pattern of said os(cid:173)
`cilloscope.
`3. A picture-producing device comprising a support for
`a specimen, means for focusing a beam of radiation on
`said specimen, a radiation detector adapted to receive said
`beam of radiation after the latter impinges on said speci(cid:173)
`men and to produce an electrical output proportional to
`the intensity of radiation thus received, an oscilloscope
`having horizontal and vertical inputs, means connecting
`said oscilloscope to the output of said radiation detector
`to reproduce images proportional in intensity to the output
`of said radiation detector, means mounting said specimen 35
`support for movement in two mutually transverse direc(cid:173)
`tions, a pair of electrically driven means each adapted to
`vibrate said specimen support in a separate one of said
`mutually transverse directions for scanning said beam of
`radiation over an area of said specimen, means connect- 40
`ing one of said vibrating means to said horizontal input
`
`8
`and the other of said vibrating means to said vertical
`input in a manner to synchronize the scanning vibrations
`of said specimen support with the raster pattern of said
`oscilloscope, and electrical driving means adapted to drive
`5 said vibrating means at frequencies high enough to pro(cid:173)
`duce a sustained image of the scanned area of said speci(cid:173)
`men on said oscilloscope.
`4. A picture-producing device comprising a support for
`a specimen, means for focusing a beam of radiation on
`10 said specimen, a radiation detector adapted to receive said
`beam of radiation after the latter impinges on said speci(cid:173)
`men and to produce an electrical output proportional to
`the intensity of radiation thus received, an oscilloscope
`having horizontal and vertical inputs, means connecting
`15 said oscilloscope to the output of said radiation detector to
`reproduce images proportional in intensity to the output
`of said radiation detector, means mounting said specimen
`support for movement in two mutually transverse direc(cid:173)
`tions, said specimen support being fabricated of a mag-
`20 netically susceptible material, a pair of electromagnets
`each positioned to vibrate said specimen support in a sep(cid:173)
`arate one of said mutually transverse directions for scan(cid:173)
`ning said beam of radiation over an area of said speci(cid:173)
`men, means connecting one of said electromagnets to said
`25 horizontal input and the other of said electromagnets to
`said vertical input in a manner to synchronize the scan(cid:173)
`ning vibrations of said specimen support with the raster
`pattern of said oscilloscope, and electrical oscillator means
`connected to drive said electromagnets and capable of
`30 frequencies high enough to produce a sustained image of
`the scanned area of said specimen on said oscilloscope.
`References Cited in the file of this patent
`UNITED STATES PATENTS
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`Von Ardenne _____________ Oct. 7, 1941
`Wolff et al. ______________ Dec. 8, 1953
`Pike ___________________ Jan. 17, 1956
`Frommer ______________ Dec. 25, 1956
`Dell -------------------- May 7, 1957
`Meyer _________________ Aug. 12, 1958
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`3SHAPE 1009 3Shape v Align IPR2021-01383
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