US3651370A - Charged-particle-beam focusing and deflecting system utilizing a plurality of electronic lenses for focusing the beam - Google Patents

Abstract

This invention relates to a system for focusing and deflecting a beam of charged particles comprising a charged particle gun, means for generating a beam of charged particles and electromagnetically deflecting the emitting direction of the beam and a surface or screen to be illuminated with said beam, characterized by the fact that at least two sets of means for deflecting the charged beam are provided between said beam generating means and said screen, so that the position and direction of incidence of said beam upon said lens or group of lenses can be controlled independently of each other to focus said beam on a desired minute region on said screen. This novel system makes it possible to reduce the size of the focal spot of the beam on the screen and improve the deflection accuracy of such beam.

Description

[451 Mar. 21, 1972 [54] CHAGED-PARTICLE-BEAM IFOQUSING AND DEF LECTING SYSTEM UTILIZING A PLURALITY OF ELECTRONIC LENSES F OR F OCUSING THE BEAM [72] Inventor: Eiichi Goto, Fujisawa-shi, Japan [73] Assignee: Rikagaku Kenkyusho Hirowasa, Yamatomachi, Kitaadachi-gun, Saitama-ken, Japan [22] Filed: July 18, 1969 [21] App]. No.: 843,128

[30] Foreign Application Priority Data June 12, 1969 Japan ..44/46258 July 19, 1968 Japan ..43/5l06l [52] U.S.C1 ..3l5/18,3l5/31 [51] lrlt.Cl. ..H01j 29/70 [58] Field otSearch ..3l5/12,13, 18, 31; 313/92 PD [56] Reterences Cited UNITED STATES PATENTS 2,793,317 5/1 97 7 Lawrence ..3 13/9 2 PD 2,879,444 3/1959 Nunan ..315/14 2,943,230 6/ 1960 Lawerence et a1 3,448,316 6/1969 Yoshida et a]. 3,417,199 12/1968 Yoshida et a1. ..3l5/14X 5 7] ABSTRACT This invention relates to a system for focusing and deflecting a beam of charged particles comprising a charged particle gun, means for generating a beam of charged particles and electromagnetically deflecting the emitting direction of the beam and a surface or screen to be illuminated with said beam, characterized by the fact that at least two sets of means for deflecting the charged beam are provided between said beam generating means and said screen, so that the position and direction of incidence of said beam upon said lens or group of lenses can be controlled independently of each other to focus said beam on a desired minute region on said screen. This novel system makes it possible to reduce the size of the focal spot of the beam on the screen and improve the deflection accuracy of such beam.

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CHARGEDTARTICLE-BEAM FOCUSING AND DEFLECTING SYSTEM UTILIZING A PLURALITY OF ELECTRONIC LENSES FOR FOCUSING THE BEAM SUMMARY OF THE INVENTION This invention relates to improvements of a system for focusing and deflecting electron beam. The invention has for its object to reduce the diameter of the focal spot of the electron beam on the surface to be illuminated and attain an improved accuracy in the deflection of the electron beam as compared with those of ordinary systems.

A fine beam of electrons deflected two-dimensionally up and down and left to right has a very extensive range of applications, for example, in cathode-ray tubes of television sets and instruments for waveform monitoring, television image pickup tubes such as vidicons and orthicons, electron beam memories, electron beam working apparatus, and electron scanning microscopes. These applications for electron beam invariably make use of scanning of two-dimensional patterns by electron beam. To increase the accuracy of the scanned patterns, it is desirable to minimize the size of the spot on which the electron beam focuses and it is also essential that the position of the electron beam for deflected surface scanning be designated with a high precision and good reproducibility. The present invention is directed to the provision of an electron beam focusing and deflecting system which meets the above requirements by forming an electron lens sector of a short focal length very close to the surface to be illuminated with electron rays and moving the electron lens sector synchronously with the deflection of the electron beam or by deflecting the input angle of beam to the lens sector of short focal length.

BRIEF DESCRIPTION OF THE DRAWING The above and further features, advantages and objects of the present invention will become more apparent from the following description of an exemplary embodiment thereof, illustrated in the accompanying drawings.

FIG. I is a schematic view illustrating an electron-optical system of a conventional design for irradiation of an electron beam;

FIG. 2 is a schematic view illustrating an optical system wherein the electron beam of FIG. 1 is replaced by a light beam for explanation;

FIGS. 3 and 4 are schematic views explanatory ofthe principles of the present invention in terms of an optical system, FIG. 3 showing an arrangement with a single lens, and FIG. 4 an arrangement with a plurality of lenses;

FIGS. 5 and 6 are schematic views explanatory of an embodiment of the present invention, FIG. 5 showing an arrangement with electrostatic lens sectors and FIG. 6 with electromagnetic lens sectors;

FIG. 7 is a view explanatory of the operation of the system of FIG. 6;

FIG. 8 is a view explanatory of the operation of the system of FIG. 5;

FIG. 9 is a view explanatory of the deflection accuracy according to the present invention as expressed in connection with an optical system;

FIG. I0 is a schematic view explanatory of an embodiment ofthe present invention using two deflection systems;

FIG. I1 is a partly enlarged view of FIG. 10 explanatory of the deflection accuracy;

FIG. I2 is a view explanatory of an arrangement using three deflection systems;

FIG. 13 is a view explanatory of an arrangement wherein deflection systems are used in common; and

FIG. 14 is a sectional side elevation of a double-deflection cathode-ray tube embodying the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The principles of the present invention will now be explained by comparing the electron-optical lens system to an ordinary optical lens system.

Referring to FIG. 1, showing the structure of a conventional electron gun, the symbol K indicates an electron-emitting cathode. G is an electrode having a slit S. GAl and GA2 are accelerating electrodes, GL is an electronic static lens electrode, and SC is the screen to be illuminated with a beam of electron rays. DP is a deflecting electrode. Ifit is assumed, for simplicity, that the potential at the cathode K in this electron gun is zero, a positive voltage is applied to the accelerating electrodes GAl and GA2, and a positive voltage lower than the voltage for the accelerating electrodes GA] and GA2 is applied to the lens electrode GL. To the electrode G having the slit S is usually applied a slightly negative voltage. An electron beam EBa or EBb that has been shot out of the cathode K is focused on the screen SC by virtue of the lens actions of the electrode systems GAl, GL, and GA2, the position of the beam on the screen being controlled by a deflecting voltage applied to the deflecting electrode DP. Aside from the electron beam focusing system using a static lens as above described, a system is also in wide use in which a magnetic lens serves as a focusing lens as indicated at PC in FIG. 1 and the electron beam is thereby focused. For the deflection of the electron beam, another known process depends on electromagnetic deflection whereby a deflecting current is caused to flow through a deflecting coil as indicated at DC in FIG. 1. Whichever method be used to for focusing, an image SPa or 5% of the slit S will be produced on the screen SC by the electron optic system.

The size d of the spot of electron beam to be formed on the screen and the diameter 11 of the slit are in the relation d =d,6,/0 u where 0 represents the angle of emergence from the slit of the electron beam and 0 represents the angle of incidence of the beam on the screen. The magnification of the electron lens system is M 0 /0 and if this magnification is reduced the spot diameter d will be decreased accordingly. In order to deflect the electron beam, however, the distance I between the electron lens and the screen SC is required to be equal to or more than the deflecting distance D of the electron beam. To maintain the intensity of the electron beam, the distance 1 between the electron lens and the slit S cannot be increased beyond a certain limit. Thus, between the image magnification M and the distances I and 1 the following relationship holds:

M (L/0 (1 /1,) ,{VJV 1;. (where V represents the accelerating potential of electrons in the vicinity of the slit, and V represents the accelerating potential of electrons in the vicinity of the screen). The voltage in Equation (2) above is substantially dictated by the intended use, and the ratio of distances to 1,, Le, 1 /1,, cannot be very small in ordinary electron guns. For this reason, the magnification M is usually chosen from the range of l to 10, and considerable difficulty is encountered in reducing the spot diameter d In FIG. 1, the symbols SP0 and SP1: represent two spots on the deflection surface, indicating that the deflection angle between the two spots is a.

For the convenience of explanation, the electron beam of FIG. 1 has been replaced by a light beam in FIG. 2.

In this figure, the symbol LA is a light source, S is a slit for light emission, and LE is a lens. The three together constitute a light projector. A beam of light rays LBa or LBb emerging through the lens LE is focused on a screen SC to form a spot image SPzz or SPb thereon. By way of illustration, the deflection of light is accomplished by deflecting the projector (LE, S and LA) by an angle of deflection a with respect to a supporting point D which is imaginary, thereby obtaining spot SPa or SPb. Let the magnification of the optical system in this case be M and the slit diameter 11,, and then the spot diameter d will be d, Md, and, if the magnification is M, the distance between the lens LE and the slit 5 is 1 the distance between the screen SC and the lens LE is 1 and an angle of emergence of light from the slit is 0,, and the angle ofincidence on the screen is 6 then but in the arrangement as shown in FIG. 2 wherein I is very substantial the magnification M is increased and makes it impossible to decrease the spot diameter d on the screen,

The present invention is an improvement over these prior arrangements in that it makes possible the successful reduction of the spot diameter d FIG. 3 is a view explanatory of the principles of the present invention in terms of an optical system.

The symbols D, LA, S, LE, LB, and SC in FIG. 3 designate parts corresponding to those in FIG. 2. In accordance with this invention a lens LM ofa short focal length is located at a point in front of the screen. By dint of this lens LM the light beam LBa is sharply converged and the angle of incidence of the light beam on the screen is increased, with the result that the magnification M is decreased by the relationship M 6,/6 Hence the diameter of the light beam spot d Md, 5 is decreased.

The position x of the optical axis OX of this lens LM must be moved synchronously with the angle of deflection a of the light beam. In other words, if the distance between the supporting point D and the screen SC is d, it is simply necessary to move the lens in such a way as to attain the relationship:

X= d tan a (6).

In this case the short-focus lens LM to be provided close to the screen needs not be a single lens as shown but may be replaced by a series oflenses LMF as shown in FIG. 4. Assuming that, in the latter case, the multiplicity of lenses are arranged end to end at regular intervals A, the light beam may be allowed to be incident on the vicinity of the optical axis of one of such lenses.

If such is the case the shifting distance x of the multiple lenses has only to be xink=dtanoz 7 (where n is an integer or zero). This means that a shifting distance x of not more than A will suffice.

The essence of the present invention resides in the application of the principles above described in connection with an optical system in the focusing of electron beam.

The present invention will now be described in further details as embodied in FIGS. 5 and 6.

In these figures, the symbol EG stands for an electron gun adapted to produce a deflected electron beam in the usual manner as already described. SC stands for a screen to be illuminated with an electron beam. Referring to FIG. 5, the symbol GPL designates a group of fine conductors placed just before the screen SC. If a suitable voltage is applied to this conductor group, a static lens sector LMP will result and, for the entirely same reason as in the optical system, the spot diameter d will become very small.

In FIG. 6, coils LCP disposed close to the screen SC from a magnetic field H, which in turn constitutes a magnetic lens sector LMP that functions in the same manner as the static lens sector in FIG. 5.

The position x of such electron-optical lens sector LMP of electrostatic or electromagnetic type may be shifted synchronously with the main deflection angle a of the electron beam. As this is carried out electrically, the speed can be greatly increased. Especially where a multiplicity of lens sectors are employed, the circuit for shifting the lens positions can be remarkably simplified. This will be further explained hereunder in connection with magnetic lens sectors.

In FIG. 7- there are shown coils LCP (same as those in FIG. 6) through which currents flow at right angles to the visible plane. Here a current I, is caused to flow through each coil 1 positively upward and through each coil 1 positively downward. Also a current I is caused to flow through each coil 2 positively upward and through each coil 2' positively downward. At this point a current as in a linear motor may be caused to flow to shift the pattern of the magnetic field to a desired position x. If the interval of repetition of the coils is A, the electromagnetic lens sector can be shifted toward x only if currents conforming to the conditions are applied. In this case the center of the optical axis of the lens sector will be positioned where the z component of the magnetic field (in the direction from which the electron beam is incident) is at its peak. Thus, functions are attained as by the multiplicity of convex lens sectors LMP in FIG. 7. For the shifting in position of the lens system it is only necessary to change the two currents I, and I Illustrated in FIG. 7 is a case where I =0 and I, 0.

FIG. 8 illustrates an embodiment using electrostatic lens sectors. If the samepotential is maintained at every four grids GDL (same as GDL in FIG. 5), the intervals of the four grids being A, and further if four different voltages V,, V,, V and V are applied, for example, as

V' V V sin (21rx/A) then the multiplicity of static lens sectors produced as at LMP in FIG. 8 may be shifted toward x. In the position of the senses shown in FIG. 8, V V =0, V, O, and V, 0.

When an ordinary vidicon (for electromagnetic focusing and electromagnetic deflection) was employed for the electron gun EG in the system utilizing electromagnetic lens sectors as shown in FIG. 6, and the system was operated with an accelerating voltage (the voltage applicable between the cathode K and the electrode G) of 300 v., a cycle A of coils LCP of four cm., and a magnetic field H of about 200 G, the result was that the spot size could be reduced to about onefifth of the ordinary size. LB

While it is obvious from the foregoing that the present invention is effective in remarkably decreasing the diameter of the electron beam on the screen as compared with the beam diameters produced by conventional systems, the invention has an additional advantage of a substantial improvement in the deflection accuracy of the electron beam.

In the conventional electron beam deflection system illustrated in FIG. 1, the deflection angle 0: is the direct determinant of the accuracy in beam position on the screen. FIG. 9 illustrates, by contrast, the positional accuracy according to the invention in connection with an optical model. LM, OX, and SC are the same as those in FIG. 3 but are shown here on an enlarged scale, LM standing for a lens, OX for the optical axis thereof, and SC for the screen. Since the light projector is located remotely as in FIG. 3, the light beam enters the lens LM in the form ofa flux of substantially parallel rays of light. Even if the rays oflight are deviated, for example from LB, to LB in FIG. 9 due to deviation accompanying the deflection of the projector, they will form an image on the same point along the optical axis OX on the screen. Thus, the deviation of the light rays from LB, to L8 has no deleterious effect unless the rays deviate beyond the paths leading to the lens sector LM. The same applies to the electron beam, in which case the main deflection accuracy suffices only if the beam is incident on the aperture length A of the lends. On the other hand, the position of the optical axis OX of the lens is such that, when an electromagnetic lens sector is defined by grids or coils as in FIG. 5 or FIG. 6, it is given as a slight displacement from the fixed grids or coils and therefore the OX position is determined with a high precision.

The present invention has so far been described in connection with embodiments thereof in which the position of a short-focus electron lens sector is synchronized with the deflection of the beam to effect the focusing and deflection of the beam. Next, description will be given of embodiments wherein the short-focus lens is fixed and two or more deflection system are provided so as to carry out independent control ofthe position and direction ofincidence of the beam.

Referring to FIG. 10, the symbols LB, LCL, LMPa, LMPb and so forth all represent electron lenses formed by an electromagnetic field. For clarity they are illustrated as optical convex lenses. DPM, DPM, and DPA, DPA' represent deflecting electrodes for causing electrostatic deflection of the electron beam. (Instead of the deflecting plates, coils may be provided for electromagnetic deflection). IMPa to LMPe are a series of lenses having a short focal length f,,, and held in front of a common screen SC. The distance between these lens sectors LM? and the screen SC is set to f,,,. LCL is a collimator lens with a focal distance off and this collimator lens LCL and the short focus lens sectors LMP are spaced apart a distance equivalent to the focal distance f,. The distance between the collimator lens sectors LCL and the deflection center of the deflection system DPM (which is hereinafter called the positioning deflection system) is also set to f LB is a focusing lens with a focal distance of f,,. The deflection center of the positioning deflection system DPM and the focusing lens sector LB are kept apart from each other by a distance equivalent to the focal distance f and the distance between the lens sector LB and the deflection system DPA (which is hereinafter called the directional deflection systems) is also set to f,,.

It should be noted that while in the embodiment of FIG. 10, for simplicity of explanation, the distance between the short focus lens sectors LMP and the collimator lens sector LCL is set tof and the distances between the focusing lens sector LB and the positioning deflection system DPM and between the focusing lens sector LB and the directional deflection system DPA are set to f these distances may be interdependently changed.

With the construction above described, the electron gun shoots an electron beam EB and subjects it to plate deflection by the directional deflection system DPA, so that beyond the focusing lens sector LB the beam is changed to B8,, EB or EH depending on the voltage that is applied between the deflecting plates DPA and DPA. In the absence of any deflecting voltage to be applied to the positional deflection system DPM, the electron beam EB BB or EB will pass through the lens sector IQVIP to focus on the screen SC at the spot SP SP or SP respectively. The function of the directional deflection DPA in this case is such that in the lens sector LMP the incidence position of the electron beam in that lens remains unchanged but the direction of incidence alone is changed. This will be readily appreciated from the definition of the focal length of lens sector in general. Next, if the electron beam is deflected by applying a deflecting voltage between the electrodes DPM and DPM of the positioning deflection system DPM, it can then be incident on a second lens sector other than LMP e.g., LMP,,. In this case again the incidence direction of the beam into the lens sector LMP varies with the voltage applied to the directional deflection system DPA, and the beam is focused on the spot SP SP or SP on the screen depending on whether the electron beam is varied to EB EB or EH respectively. As will be understood from the definition of the focal distance oflens sector and also from the arrangement of the lens sectors, deflection system and screen in FIG. 10, the function of the positioning deflection system DPM is to cause changes in the position of the electron beam to pass through the group of short-focus lens sector LMP to LMP and therefore it is possible to guide the electron beam into a desired lens sector among the group of lens sectors LMP to LIVIP by applying a suitabLe voltage to the positioning deflection system. On the other hand, the function of the directional deflection system DPA is, as already described, to change the direction of incidence of the electron beam in any selected one of the group oflens sectors LMP to LMP...

The deflection accuracy of the positioning deflection system DPM is not critical because the electron beam has only to fall on a desired one of the short-focus lens sectors. FIG. 1] gives a view explanatory of this with an enlarged section of a part of FIG. l0 showing how a beam passes along different passages through the lens sector LMP,,. It is assumed now that a straightly incident beam E13 or an inclinedly incident beam EB passes through the center of the lens sector LMP to focus on the spot SP,, or Sl on the screen. If the deflecting voltage being applied to the positioning deflection system DPM involves an error, the direction of incidence of the electron beam in the lens sector LMP,, remains unchanged and the incidence position is deviated to'EB or EB but the focusing position on the screen undergoes no change. as will be obvious from the character of the focusing plane of the lens sector. The accuracy of the directional deflection system also need not be critical, though the deviation of the focusing position on the screen is given as f A0: when the direction is erroneous by an angle Au radians because the focal distance of the lens group LMP is short. In conventional methods for focusing and deflecting an electron beam, it has been necessary, where it is desired to improve the determined accuracy in position of a row of a finite number N of brightening spots over the intervals of the spots themselves, to control the deflection voltage (or current in the case of electromagnetic deflection) and acceleration voltage precisely within lOO/KN percent wherein the safety coefficient K ranges from about 2 to 5. Here, if N=l,000 and K=2, it means that the accuracy should be as precise as 10.05 percent. In the present invention, by contrast, a row of about fipieces of short-focus lens sectors maybe arranged and therefore the deflection cur rent or voltage is not required to have an accuracy better than i IOO/K N percent. Similarly if N=l ,000 and K=2, it means a tolerance of: 1.6 percent or, in other words, the accuracy required is about one-thirtieth of the values demanded of the conventional arrangement.

In FIG. 12, the focusing lens sector LB of FIG. I0 is replaced by another set of deflection system DPB. In this case the positioning deflecting voltage V,, applied is +V,, to the deflecting plate DPM and V to the plate DPM. The directional deflecting voltage V,, applied is +V to the deflecting plates DPA and DPB and V to the deflecting plates DPA and DPB. The electron beam deflected by the deflection system DPA is deflected by the system DPB in the opposite direction, with the result that the same functional effect as in FIG. 10 is achieved.

FIG. 13 shows an embodiment in which the deflecting plates DPM AND DPB of FIG. 12 are combined in one piece and correspondingly the plates DPM and DPB are combined together. Here the voltage applicable to the combined deflecting plates DPMB and DPMB is a sum of the positioning deflecting voltage V,, and the negative directional deflecting voltage V A comparison of the embodiments of FIGS. 12 and 13 indicates that the latter is similar in construction but the accuracy required of the voltage V,,V to be applied on the combined deflecting plate DPMB is approximately doubled.

For simplicity of explanation the deflection of electron beam has been described up to this point as directed unidimensionally. However, it should be obvious of course that the same principles of the present invention are applicable equally well in bidimensional x-y deflection or may be applied to either the x or y direction and the spots in that particular direction may be reduced in size (to linear spots) so as to improve the deflection accuracy accordingly, or this practice may be resorted to simultaneously in both directions .x and y to attain the same effects. Also, while the foregoing description has dealt with the beam of electrons, it is appreciated that the same principles apply to beams of given charged particles as well.

In FIG. 14 there is illustrated a form of electron beam focusing and deflecting device embodying the invention. The components are generally built in and around a vacuum glass container GL like a usual cathode-ray tube. EG is an electron gun similar to the one used in an ordinary cathode-ray tube. A0 is an accelerating electrode in the form of a film as shown with hatching over the inner wall surface of the glass. SC is a screen coated with a fluorescent material. FMS is a fine mesh electrode (with a mesh pitch of0.l mm. EMS is a fine mesh electrode similar to FMS but is connected to a cylindrical electrode RF. The electrode RF is a hollow cylindrical electrode having an axial length 0.5 to 1.0 times of the radius thereof. As a positive potential is maintained on the electrode RF by the electrode A0, a collimator lens sector LCL is electrostatically formed, and the axial length of the RF minimizes the spherical aberration of the collimator lens sector LCL. LMP is a metallie plate perforated with small holes 1.5 mm. in diameter and which are provided in a square formation at intervals of two mm., numbering 32 X 32 X 1,024 holes in all. By the application ofa voltage (about 40 to 50 percent) from the nearby fine mesh electrodes FMS and EMS, a group of electrostatic lenses each having a focal distance of 30 mm. are formed across the perforated plate. DPMB and DPA represent electromagnetic deflection systems consisting of deflection coils instead of the electrostatic deflection means in FIG. 10, 12 and 13. As shown in FIG. 14, DPA is intended for directional deflection and DPMB is jointly for directional and positional deflection. In either system the deflection is directed to both directions X and Y. When this bulb was operated with an accelerating voltage of two kv. (as applied to RF, EMS and FMS, but with zero voltage to the cathode), a spot 50 LL or less in size was formed on the screen (as compared with spots ranging in size from 300 to 500 ,u in conventional cathode-ray tubes). Thus, on a 64 mm. X 64 mm. screen for 1,024 X 1,024 brightening spots, the reproducibility of the spot positions attained was 1 30,41. even with a deflection current with an allowance of: 0.5 percent and this permitted the brightening spot control with a high precision such as has never been feasible with an ordinary cathode-ray tube.

Where the group of short-focus lens sectors LMP are fixed in position in the manner described above, they may be fabricated from a perforated plate, thus greatly simplifying the manufacturing and enabling a high fabrication accuracy to be achieved with ease to extreme practical advantages.

What is claimed is:

1. A system for focusing an electron beam on an object comprising a source of a beam of electrically charged particles, a series of electron focusing members placed at a predetermined short focal length adjacent the object and intermediate the object and the electron source and establishing a plurality of lens sectors for focusing the beam, a directional deflection system for changing the direction of incidence of the electron beam in any selected one of said lens sectors responsive to a directional deflecting signal and a positioning deflection system for changing the incidence position of the electron beam from one lens sector to another lens sector responsive to a position deflecting signal upon said positioning deflection system.

2. A system according to claim 1, wherein said directional deflection system comprises a focusing lens and a beam deflecting means positioned between said electron source and said positioning deflection system.

3. A system according to claim 1, wherein said directional deflecting system comprises at least two deflecting means provided along the path of the beam between said electron source and said position deflection system, upon one of said means is applied a directional deflecting signal of a given polarity and upon the other of said means is applied a directional deflecting signal of the opposite polarity.

4. A system according to claim 1, wherein said directional and positional deflecting systems comprise at least two deflecting means provided along the path of the beam between said electron source and said series of electron focusing members, upon one of said means is applied a directional deflecting signal in a given polarity, and upon the other of said means is applied the difference between a position deflecting signal and said directional deflecting signal.

5. A system for focusing and deflecting an electron beam on an object according to claim 1, comprising a series of shortfocus electronic lenses placed at their focal length from said object, a collimater lens spaced along the electron path between said lens and a positioning deflection system, said positioning deflection system being spaced along said electron path a distance equal to the focal length ofsaid collimater lens and serving to change the incidence position of said electron beam from one of said short-focus electronic lenses to another.

6. A system according to claim 1 which is provided with a collimater electron lens located between said plurality of lens sectors and said positioning deflection system.

7. A system according to claim 1 wherein said deflection system comprises a plurality of electrostatic deflectors, each being composed ofa pair of deflecting electrodes in respect of a given deflecting dimension.

8. A system according to claim 1 wherein said deflection system comprises a plurality of magnetic deflectors, each being composed of an electric coil in respect of a given deflecting dimension.

lOl028 0431 ENTTEE STATES PATENT @EETEE QERHHQATE @F (MRREQHN Patent NO. 3,651,370 Dated March 21, 1972 Inventor(s) Eiiohi GOCO It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown' below:

On the cover sheet {73] the name of the assignee should read Rikagaku Kenkyusho, saitama ken, Japan Signed and sealed this 9th day of December 1972 (SEAL) Attest:

EDWARD M.FLETCHER,JR, ROBERT GOTTSCHALK Attesting Officer 7 Commissioner" of Patents USCOMM-DC 50376-P59 U.S4 GOVERNMENT PRINTING OFFICE: I959 0-366-334,

FORM PO-105O (10-69) UNITED STATES PATENT OFFICE CERTWECATE 9F (IORREQ'HQN Patent No. 3,651, 370 Dated March 21, 1972 Inventor(s) Eiifihi GOtO It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the cover sheet {73] the name of the assigneeshould read Rikagaku Kenkyusho, Saitama-ken, Japan Signed and sealed this 9th day of December 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM PC4050 (0439) USCOMM-DC e0376-i= e9 U.S. GOVERNMENT PRlNTING OFFICE 1 i969 O366334,

Claims (8)

1. A system for focusing an electron beam on an object comprising a source of a beam of electrically charged particles, a series of electron focusing members placed at a predetermined short focal length adjacent the object and intermediate the object and the electron source and establishing a plurality of lens sectors for focusing the beam, a directional deflection system for changing the direction of incidence of the electron beam in any selected one of said lens sectors responsive to a directional deflecting signal and a positioning deflection system for changing the incidence position of the electron beam from one lens sector to another lens sector responsive to a position deflecting signal upon said positioning deflection system.

2. A system according to claim 1, wherein said directional deflection system comprises a focusing lens and a beam deflecting means positioned between said electron source and said positioning deflection system.

3. A system according to claim 1, wherein said directional deflecting system comprises at least two deflecting means provided along the path of the beam between said electron source and said position deflection system, upon one of said means is applied a directional deflecting signal of a given polarity and upon the other of said means is applied a directional deflecting signal of the opposite polarity.

4. A system according to claim 1, wherein said directional and pOsitional deflecting systems comprise at least two deflecting means provided along the path of the beam between said electron source and said series of electron focusing members, upon one of said means is applied a directional deflecting signal in a given polarity, and upon the other of said means is applied the difference between a position deflecting signal and said directional deflecting signal.

5. A system for focusing and deflecting an electron beam on an object according to claim 1, comprising a series of short-focus electronic lenses placed at their focal length from said object, a collimater lens spaced along the electron path between said lens and a positioning deflection system, said positioning deflection system being spaced along said electron path a distance equal to the focal length of said collimater lens and serving to change the incidence position of said electron beam from one of said short-focus electronic lenses to another.

6. A system according to claim 1 which is provided with a collimater electron lens located between said plurality of lens sectors and said positioning deflection system.

7. A system according to claim 1 wherein said deflection system comprises a plurality of electrostatic deflectors, each being composed of a pair of deflecting electrodes in respect of a given deflecting dimension.

8. A system according to claim 1 wherein said deflection system comprises a plurality of magnetic deflectors, each being composed of an electric coil in respect of a given deflecting dimension.

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