US3493744A

US3493744A - Specimen-adjusting structure for corpuscular ray devices

Info

Publication number: US3493744A
Application number: US688505A
Authority: US
Inventors: Karl-Heinz Herrmann; Hans-Joachim Kempien
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1967-05-22
Filing date: 1967-12-06
Publication date: 1970-02-03
Anticipated expiration: 1987-02-03
Also published as: GB1224644A

Description

Feb. 3 1970 KARL-HEINZ HERRMANN ETAL 3,493,744

SPECIMEN-ADJUSTING STRUCTURE FOR CORPUSCULAR RAY DEVICES Filed Dec. 6, 1967 5 Sheets-Sheet 1 Inventors: {WI/A2112 W M '9? cim 4?:

Feb. 3, 1970 KARL-HEINZ HERRMANN AL 3,493,744 SPECIMEN-ADJUSTING STRUCTURE FOR CORPUSCULAR RAY DEVICES Filed Dec. 6, 1967 5 Sheets-Sheet 2 Fig.3

Inventors I il uz shi ma h. m

' Filed Dec. 6. 1967 Feb. 3, 1970 KARL-HEIYNZ HERRMANN ET AL? 3,

SPECIMEN-ADJUSTING STRUCTURE FOR coRPUscuLAR RAY DEVICES '5 Sheets-Sheet a Feb. 3 1970 KARL-HEINZ HERRMA'NN E L 3, 93,

SPECIMEN'ADJUSTING STRUCTURE FOR CORPUSCULAR RAY DEVICES 5 Sheets-Sheet 4 Filed Dec.

Fig. 7

l-n ventors:

L1 L lr Feb. 3,1970 KAR.L.-HE|NZ' HERRMANN ET AL 3,493,744

SPECIMEN-ADJUSTING STRUCTURE FOR CORPUSCULAR RAY DEVICES Filed Dec. 6, 1967 Sheets-Sheet 5 Fig.9

lnventors= 50m!- fif m ma M United States Patent U.S. Cl. 250-49.5 25 Claims ABSTRACT OF THE DISCLOSURE Structure for adjusting a specimen in the interior of a corpuscular ray device such as an electron microscope. The adjustment of the position of the specimen which is to be investigated is brought about by way of a control motor capable of being remotely controlled and situated at the exterior of the corpuscular ray device. This control motor takes the form of a stepping motor which is actuated by pulses received from a pulse transmitter. The number of pulses transmitted to the stepping motor from the pulse transmitter will determine the magnitude of the adjustment of the specimen while the speed with which it is moved is determined by the frequency of the pulses. The extent of movement of the stepping motor provided by each pulse is determined by the smallest required movement of the specimen.

Our invention relates to a structure for adjusting a specimen which is situated in the evacuated interior of a corpuscular ray device such as an electron microscope.

The specimen which is to be investigated is carried, for example, by a specimen stage which is shiftable in a plane normal to the corpuscular ray by way of a pair of rods which extend in a vacuum-tight manner between the interior and exterior of the housing of the device. These rods extend perpendicularly with respect to each other and with respect to the corpuscular ray, and in response to axial shifting of these rods by way of a control motor which can be remotely actuated, the specimen has its location within the device adjusted.

A construction of this latter type is disclosed in copending application Ser. No. 652,586, filed July 11, 1967.

The number of ways in which this structure can be used is relatively limited, and the adjustments cannot always be conveniently carried out by the operator. In addition, it is difficult to reproduce positions of the specimen so that it is not always possible to return precisely to a previously investigated part of a specimen to carry out further investigations of such a previously investigated part. Furthermore, the cost of the structure at the present time is quite high and its precise adjustment with respect to the corpuscular ray device is difiicult to carry out.

It is accordingly a primary object of our invention to avoid the above drawbacks.

In particular, it is an object of our invention to provide a wide range of use for structures of the above general type as well as a specialized utility therefor.

Thus, it is an object of our invention to provide a structure which can be remotely controlled by suitable motors and which at the same time can be manually actuated, if desired.

Furthermore, it is an object of our invention to provide a structure which includes unitary assemblies which can be manufactured as separate units and which can be mounted as such units on the corpuscular ray device, so as to reduce the cost of the structure.

Furthermore, it is an object of the invention to provide a construction which will be capable of precise mounting 3,493,744 Patented Feb. 3, 1970 r. CC

on the corpuscular ray device, compensating for any tolerances which are encountered in the manufacture of the parts.

Also, it is an object of the invention to provide a construction of this type which is very convenient to operate.

Furthermore, it is an object of the invention to provide a structure which lends itself to a system of coordinates in the determination of the location of the specimen, so that with such a system of coordinates it becomes possible to reproduce in a highly accurate manner any location of the specimen within the device.

Our invention is capable of use with corpuscular ray devices in the form of electron microscopes or ion microscopes, as well as with electron difiraction devices or other types of devices of this nature wherein a given specimen is to be investigated with the possibility of adjusting the position of the specimen by Way of control motors.

In accordance with our invention the control motors take the form of stepping motors which are actuated by way of pulse transmitters. Thus, in accordance with the number of pulses transmitted to the stepping motors from the pulse transmitter it is possible to determine the magnitude of travel of the specimen, and the speed of movement of the specimen is determined by the frequency of the pulses. The extent to which the stepping motor is actuated in response to a single pulse is determined by the smallest required movement of the specimen.

Thus, the stepping motors of our invention can be operatively connected with rods of the type referred to above which extend in a vacuum-tight manner through the wall of the housing of the device so as to adjust the specimen in the interior thereof. Our invention is not limited, however, to actuation of such adjusting rods. It is also possible to use our invention with rod-shaped specimen holders which can also provide an adjustment of the position of a specimen with respect to the corpuscular ray by way of stepping motors. Furthermore, it is possible to use our invention in connection with adjustment of the specimen along the axis of the device, as may be required to bring about predetermined focusing.

Our invention also can be used to adjust the position of a specimen holder in the form of a tiltable cartridge whose angle with respect to the corpuscular ray can be adjusted by way of the stepping motors of our invention. Thus, in this case instead of bringing about shifting movement of a specimen stage there is an angular tilting of a cartridge which carries the specimen, and such a tiltable cartridge may be received in a specimen stage. Such a specimen stage can be provided with additional stepping motors or clutches which provide the connection with the stepping motors for carrying out the tilting movements of the tiltable cartridge, so that with such a construction the movement of the specimen stage transversely with re spect to the corpuscular ray can also be carried out by way of stepping motors.

Our invention also can be used to bring about rotary movement of the specimen by means of stepping motors in a reproducable manner.

Thus, our invention relates quite generally to structures for bringing about specimen movements with the structure of our invention being specialized to the extent that it makes special use of stepping motors. This selection of special motors and the control thereof by way of pulses results in substantial advantages. As will be apparent from the description below, it is possible by using a preliminary adjustable pulse counter to construct the device in such a way that even during movement of the specimen the hands of the operator are free to carry out other adjustments at the corpuscular ray device, such as, for example, focusing of the lenses thereof. Furthermore, the movement of the specimen by discrete steps provides the possibility of scanning the specimen practically according to a system of coordinates wherein the coordinate graduations or divisions are determined in a reproducable manner by way of the individual steps. Thus, the individual specimen positions can be provided with coordinate values and thus these positions can be investigated repeatedly after other positions of the specimen have been considered.

One of the advantageous properties of stepping motors of this type, namely the possibility of controlling the stepping speed within a large range, for example, between 1 and 300 steps per second, is of particularly favorable significance in connection with acorpuscular ray device since it is possible in this way to adapt the speed of travel of the specimen to the different degrees of enlargement provided, for example, in an electron microscope without requiring any gear switching structures or the like. Thus, in the case Where a relatively large degree of enlargement is provided, the speed of travel of the specimen which is under investigation must be smaller than in the case of a relatively small degree of enlargement, since one step of the stepping motor at a high degree of enlargement results in an even larger movement of the specimen in the final image which is observed by the operator.

As will be apparent from the description below, it is possible to construct the driving components for the stepping motors at relatively low cost, these components bringing out in a relatively short time the positioning of predetermined specimen points according to a system of coordinates. More particularly, with the structure of our invention, it is possible to bring about simultaneous movement in the directions of both coordinates.

According to a preferred construction of our invention the specimen holder, which may, for example take the form of a. specimen stage or a tiltable cartridge, is under the influence of a pair of mutually perpendicular rods which are perpendicular to the corpuscular ray and which are capable of being adjusted in accordance with our invention independently and separately from each other by way of the stepping motors. Thus it is possible by way of such stepping motors to move the specimen either in any desired direction in agiven plane transversely with respect to the corpuscular ray or within a given angular region about the axis of the corpuscular ray.

Our invention is illustrated by way of example in the accompanying drawings which form part of our application and in which:

FIG. 1 is an elongated sectional elevation of one possible embodiment of a structure according to our invention;

FIG. 2 shows an elevation of the structure of FIG. 1 taken in a plane perpendicular to that of FIG. 1 with part of the corpuscular ray device being shown in phantom lines in FIG. 2;

FIG. 3 is a schematic partly sectional illustration of a structure for controlling the stepping motors;

FIG. 4 is a schematic top plan view fragmentarily illustrating the structure shown at the right of FIG. 3;

FIG. 5 is a schematic representation of another type of adjustable structure for controlling the stepping motors;

FIG. 6 schematically illustrates one type of specimencarrying structure which can be adjusted with the structure of the invention;

FIG. 7 is a schematic representation of another type of specimen adjusting structure which can be used with the present invention;

FIG. 8 is a schematic elevation of another embodiment of an adjusting structure; and

FIG. 9 is a schematic top plan view of the transmission of FIG. 8.

The structure which is shown partly in section in FIGS. 1 and 2 includes an adjusting spindle which forms part of an adjusting means, this spindle being adjustable from the stepping motor through an electromagnetic clutch. The structure shown in FIGS. 1 and 2 is to be considered as turned through from its actual position so that the upper end of the actual structure is located at the left of FIGS. 1 and 2, while the lower end thereof is situated at the right of FIGS. 1 and 2.

The upper end of the structure is shown only in FIG. 1 and includes an inclined end face 2 situated at the upper end of the adjusting spindle 1. This inclined end face 2 engages a correspondingly inclined end face at the lower end of an unillustrated vertically extending spindle component which acts on a rod which is also unillustrated. The pair of inclined faces which engage each other are coupled to each other by means of a cap nut 3 which maintains the parts assembled together and pressing against each other.

As may be seen from FIG. 1, the adjusting spindle 1 is made up of four components 4, 5, 6, and 7, and the first three of these components are interconnected with each other by way of

universal joints

8 and 9. In this way any manufacturing tolerances encountered in the individual components are compensated with respect to the hollow column 10 which forms the housing of the electron microscope and which is shown in dot-dash lines in FIG. 2, with the adjusting spindle 1 being mounted on the housing 10 at the exterior thereof in the manner indicated in FIG. 2.

The component 7 however, has a special construction at its ends. At the lower end of component 7 shown in FIG. 1 this component is connected to the output shaft 11 of an electromagnetic clutch 12 so as to be constrained to rotate with the shaft 11 while at the same time being capable of moving axially with respect thereto. For this purpose the output shaft 11 is formed with an axially extending slot 13 which is traversed by a pin 14 which is connected with the spindle component 7.

The connection between the spindle components 6 and 7 is also brought about by way of a pin 15 received in an opening 16 of the component 7.

A bridging member 17 is provided for maintaining the components 7 and 12 axially aligned with respect to each other. Thus, the upper end of the bridging member 17 carries a bearing 18 in the form of a sleeve in which the spindle component 6 is supported for rotary movement. At its lower end the U-shaped bridging member 17 is fixed to the electromagnetic clutch 12. This bridging member 17 extends around the handwheel 19 which serves to provide manual adjustment of the specimen. The clutch 12 provides the possibility of actuating the handwheel 19 without requiring simultaneous movement of the stepping motor 21 which is of a known construction and which is connected to the clutch 12 through the stepup gearing transmission 20.

The primary components of the electromagnetic clutch 12 are the

clutch bodies

22 and 23 which are made of magnetically acting material and which are provided with brass bushings 24 and 25. The

clutch bodies

22 and 23 are surrounded by a coil 26 for generating the magnetic flux which flows at the instant when current flows through the winding 26 over the clutch bodies 23 and the small air gap between the

clutch components

22 and 23.

As is apparent from FIGS. 1 and 2, the housing 27 of the clutch 12 is fixed to the bridging member 17 by way of screws 28.

Also, by way of screws 29 the step-up transmission 20 which is of a conventional known construction is connected by a flange to the housing 27. Screws 30 also hold the transmission 20 fixed to a flange of the stepping motor 21. Thus, with this construction all of the parts shown in FIGS. 1 and 2 form a unitary assembly which after it is assembled can be fixed to the column or housing of a device such as an electron microscope, for example, simply by threading of the cap nut 3 onto a cooperating member and by fixing the unit to the corpuscular ray device for example in the manner shown at 31 in FIG. 2.

In the example which is illustrated in the drawings and described above a stepping motor is provided for each adjusting spindle. Thus, an additional adjusting spindle can be situated at a location displaced by 90 with respect to the spindle 1 and can coact with another adjusting rod, so that in this case both adjusting rods can be used to bring about adjusting movements of a specimen stage in a plane which is normal to the corpuscular ray. Furthermore, adjusting structures of this type can be provided so as to bring about tilting movements of a tiltable cartridge which has been inserted into the speci men stage.

FIG. 3 shows the important components of an actuating mechanism which may be used for actuating the stepping motor while FIG. 4 shows parts of the structure of FIG. 3 in a plan view. The primary components of this assembly are formed by a pair of axially shiftable rods 40 and 41, the rod 41 being visible only in FIG. 4. Furthermore, only the rod 40 is illustrated to an extent which shows how an end thereof carries contacts. The other rod 41 is constructed in the same way but moves perpendicularly to the rod 40. These rods 40 and 41 are axially shiftable in bearing structures 42 and 43 situated, for example, at the control panel of an electron micro scope. As is shown in FIGS. 3 and 4, a spring means in the form of compression springs 44 and 45 extend around the rods 40 and 41, respectively, and urge the latter at their end faces 46 and 47, respectively, against a spherical surface portion 48 of a manually operable lever 49 so that the ends 46 and 47 of the rods 40 and 41 are pressed against the spherical portion 48 of the lever 49. This lever 49 has an upper end which serves as a handgrip to be manually engaged by the operator, while the lower end of the lever 49 carries a spherical member 50 which is supported in a support means 51 which resiliently grips the spherical component 50 so that the latter is clamped in order to maintain the lever 49 at any angular position to which it is moved by the operator such as the angular displacement at from the vertical position, as indicated schematically in FIG. 3.

The left part of FIG. 3 indicates the controls brought about by adjustment through a predetermined angle a for those coordinates with respect to which adjustments are made by way of the axially shiftable rod 40. A corresponding contact arrangement is provided for the axially shiftable rod 41, but this latter structure is not illustrated.

The axially shiftable rod 40 carries at its left end which is shown in FIG. 3 a pair of contacts 52 and 53, and the contact 52 forms a contact means which coacts with and slides along a pair of

stationary contacts

54 and 55. The movable contacts 52 which moves axially with the rod 40 will engage and slide along one or the other of the

stationary counter-contacts

54, 55 depending upon whether the rod 40 is moved from its zero position shown in FIG. 3 to the left or to the right through a distance determined by the magnitude of the particular angle of adjustment 0:. The

contacts

54 and 55 are respectively connected into electrical circuits which will respectively provide opposed directions of movement for the unillustrated stepping motor which is of a known construction, the contact 54 being connected, for example, into a circuit which will result in movement to the left while the contact 55 is connected, for example, into a circuit which will provide for movement to the right. Thus, when the lever 49 is swung to the left in FIG. '3 the circuit for a correspond ing movement derived from the stepping motor is closed, while when the lever 49 is moved to the right a circuit for providing a corresponding movement from the stepping motor is closed. A pulse transmitter means 56 delivers pulses to the stepping motor through a preliminarily adjustable pulse counter 57 and the switch 58, with the result that an adjustment of the specimen is brought about by the steps of the motor. Thus, the magnitude of the adjustment of the specimen depends upon the number of pulses transmitted to the stepping motor and the speed of adjustment of the specimen depends upon the frequency of the pulses. The number of pulses is determined in the illustrated example by the preliminary setting of the pulse counter 57 to which a predetermined number of pulses are supplied for example, this pulse counter permitting as many pulses generated by the pulse transmitter 56 to reach the motor by way of the contact 52 and the motor terminals A and B as are equal to the difference between the capacity of the pulse counter and its preliminary adjustment. After the predetermined number of pulses have been transmitted to the stepping motor in this way the switch 58 opens. The other terminals of the motor are indicated at A and B. The pulses may have, for example, an amplitude of 10 v., and their frequency can range, for example, between 1 and 300 per second.

The adjustment of the frequency is provided in the illustrated example by way of a frequency control means in the form of a variable resistor of the pulse transmitter means, this variable resistor being shown in the form of a potentiometer 59 which in the illustrated example is a wire potentiometer. The winding of the potentiometer is symmetrical wit-h respect to the central, zero position 60, so that when the movable component of the variable resistor, formed by the tap 53, moves from its illustrated zero position either to the left or to the right the pulse frequently increases from a low value up to higher values. In this way it is possible by actuating the lever 49 to change not only the direction but also the speed of movement of the specimen by way of the stepping motor.

The potentiometer 59 is situated in the frequency-determining circuit of the pulse transmitter means 56, this circuit also including the source of potential 61.

As may be seen from FIG. 4, the lever 49, because of its spherical form at the end 50 thereof which is resiliently clamped by the support means 51, is capable of providing simultaneous movement of both axially shiftable rods 40 and 41 and thus a pair of stepping motors can be simultaneously actuated so that the specimen stage of tiltable cartridge can be displaced in a pair of mutually perpendicular directions simultaneously at speeds which are independent of each other. The magnitude of the angle of inclination a of the lever in the direction of both of the rods 40 and 41 determines and speed of movement of the specimen in both of these directions, while the direction in which this angular movement of the lever 49 extends determines the direction of the adjustable movement of the specimen. In the event that the angle a is situated in the quadrant 1 shown in FIG. 4, then with the above described connections to the terminals A and B according to which the circuit of terminal A provides movement to the left and a circuit of terminal B provides movement to the right, both of the rods 40 and 41 will provide movement to the right by way of the stepping motors operatively connected thereto, respectively. If the lever 49 is situated in quadrant II, then the stepping motor controlled by way of the rod 40 will have a movement in the right direction while the stepping motor controlled by the rod 41 will have a movement in the left direction. When the lever 49 is moved into quadrant III, both of the stepping motors will have movement to the left, while when the lever 49 is in quadrant IV, the rod 40 will bring about movement to the left and the rod 41 will bring about movement to the right.

The arrangement of the quadrants with respect to the image screen can be brought about so as to take into account rotary movement of the image in the corpuscular ray device, so that movement of the lever 49 in a given direction brings about movement of the image of the specimen as observed at the corpuscular ray device in the same direction. With electromagnetic imaging lenses there will occur, as is well known, a turning of the image which if additional compensating measures are not provided depends upon the excitation of the lenses and thus their extent of enlargement. In order to maintain a position for the quadrants corresponding to the particular position of the image, the assembly at the control panel which includes the support means 51 and the bearings 42 and 43 for the rods 40 and 41 can be turnably mounted at the control panel for rotary movement about the axis of the lever 49 for adjusting the structure when the angular position of the image changes so as to maintain the desired relationship between the quadrants and the image.

FIG. shows another embodiment of our invention for controlling the pulse frequency and thus the speed of adjusting movement. In this case a variable resistor in the form of a rotary potentiometer 70 is provided, this variable resistor being located in the frequency-determining electrical circuit of the pulse transmitter means 72 which is also provided with a source of potential supply 71, and the sliding tap 73 of the variable resistor is actuated by way of a movable component 74 of the resistor, this component 74 taking the form of a cord or the like which is guided by rollers 75 and which is fixed at one end to an elongated rod 76 which corresponds to either of the rods 40 and 41 of FIGS. 3 and 4. This rod 76 also carries a contact 77 which will select the direction of adjustment.

When the rod 76 of FIG. 5 moves to the left or to the right, the rollers 75 will coact with the cord 74 so as to provide through the latter, irrespective of the direction of movement of the rod 76, a displacement of the slider 73 in opposition to an unillustrated spring which seeks to maintain the slider 73 in the illustrated zero position. Thus, the extent of displacement of the slider 73 will be determined by the magnitude of the angle or through which the lever 49 is turned by the operator. In this way a predetermined pulse frequency for the pulse transmitter means 72 is provided.

Thus, with our invention it becomes possible to scan a specimen in a stepwise manner in different directions, and the structure of our invention has the possibility of providing a scanning or adjustment of a predetermined region of the specimen automatically upon actuation of a key. The coordinate type of division of the specimen by way of one or more stepping motors brings about the advantage of achieving reproducibility of the position of interesting parts of the specimen with a simple structure.

While with the above-described structure separate stepping motors are provided for the separate spindles which are respectively connected to the rods which bring about the adjustment of the specimen, it is also possible to adjust both of these rods from a single stepping motor which by Way of a suitable clutch can be connected selectively to one or the other of the rods.

With the structure described above the rotary movement of the adjusting spindles will bring about translational movement of the rods which extend into the interior of the device. The use of such spindles which act on the adjusting rods in this way is in itself known, and a particular advantage of our invention resides in the possibility of using this proven and successful construction with our invention.

Various possibilities of structures for adjusting a specimen are schematically indicated in FIGS. 6-9.

Referring to FIG. 6, there is schematically illustrated therein a specimen stage 80 which is situated within an electron microscope so as to be transversely shiftable at the objective thereof. During transverse shifting the stage 80 is guided by arrangement of

peripheral rollers

81 and 82 thereof with a suitable guiding member. In order to bring about transverse shifting in one of the pair of mutually perpendicular directions a shiftable stop member 83 is provided, this member 83 acting through

rollers

84 and 85 on the specimen stage 80.

Within the stage 80 there is a known tiltable specimen cartridge, and FIG. 6 shows a type of cartridge which is used to carry out stereo-investigations. This specimen cartridge is primarily composed of a tapered tubular element 86 and the component 87 which is swingably carried by this tapered element 86. The component 87 carries at 88 the specimen which is to be investigated, this specimen being held, for example, by means of a cap member which surrounds and can be pushed onto the nozzlelike projection of component 87. It is known that 1 n order to carry out stereo-investigations, the speclmen is required to be swung about an axis passing through the specimen into a pair of different angular positions with respect to the electron ray 89 which coincides witl 1 the principal axis. In both of these latter angular positions the specimen is photographed, and both of these photographs provide the stereoscopic.

In order to carry out the swinging movement the component 87 is supported for swinging movement at 90 in the tapered tubular cartridge 86.

Within the stage there is a threaded portion 91 of the actuating rod 92 which at its left end, as viewed in FIG. 6, presses against the region of component 87 and presses the latter to the left, as viewed in FIG. 6, in opposition to an unillustrated counterspring. In this way the region 90 assumes the dotted-line position indicated in FIG. 6. The specimen is now situated in one of the predetermined angular positions for making one of the photographs, and the other position is indicated by the solid lines in FIG. 6.

In accordance with our invention, the actuating rod 92 is mechanically coupled at its right end, as viewed in FIG. 6, which extends in a known Way in a vacuumtight manner through an unillustrated wall of the housing of the microscope, to a stepping motor 93 as schematically indicated in phantom dot-dash lines in FIG. 6.

With an arrangement as schematically shown in FIG. 7, the specimen stage 101 carries a conventional specimen cartridge 102 and is supported for shifting movement in a pair of mutually perpendicular directions on the component 105 of the objective assembly.

Guide rollers

106 and 107 are carried by the stage 101 to guide the latter for movement in the mutually perpendicular directions, these rollers engaging suitable guide members. A pair of actuating

rods

103 and 104 coact with the stage 101 to shift the latter in the mutually perpendicular directions with respect to the principal axis a. These

rods

103 and 104 extend in a vacuum-tight manner through the wall of the housing of the electron microscope. At the exterior of the latter the

rods

103 and 104 are respectively engaged by

bell cranks

112 and 113 which are swingable at the

pivots

110 and 111. These bell cranks 112 and 113 are in turn angularly adjusted by way of the

rods

108 and 109 Which are vertically displaceable and which are actuated through suitable transmissions driven from the stepping

motors

114 and 115, respectively. The bell cranks 112 and 113 coact with

suitable limit switches

119 and 120 respectively connected into the circuits of the

motors

114 and 115 so as to limit the extent of adjustment.

While with the embodiment of FIG. 7 a pair of stepping motors are provided for bringing about the adjustments in the pair of mutually perpendicular directions. FIGS. 8 and 9 show an arrangement where a single stepping motor can through suitable clutches be connected either with the structure for providing adjustment of the specimen in one direction or with the structure for providing adjustment of the specimen in the other direction which is perpendicular with respect to this one direction. Thus, referring to FIGS. 8 and 9 it will be seen that the stepping motor 130 drives the shaft 131 which in turn drives the bevel gear 132. The bevel gear 132 is adapted to coact with one of a pair of

additional bevel gears

134 and 152. The bevel gear 134 has a non-circular bore which supports it for sliding movement along a shaft 137 which is of a matching non-circular cross section and which extends through the bore of bevel gear 134 so that the latter must rotate with the shaft 137 but is axially shiftable therealong. Suitable bearings carried by a pedestal 138 support the shaft 137 for rotary movement. A collar fixed to the left free end of the shaft 137, as viewed in FIGS. 8 and 9, engages one end of the spring which is coiled about the shaft 137 so as to urge the bevel gear 134 to the position illustrated in FIG. 9 where it is out of engagement with the bevel gear -132. A collar 145 which is fixed to the shaft 137 limits the movement of the gear 134 by the spring 135 away from the gear 132. A clutch sleeve which is freely turnable with respect to the shaft 137, so that the latter can rotate freely within this clutch sleeve, carries a handle 136 enabling the operator to shift the clutch sleeve and thus the gear 134 to the left, as viewed in FIGS. 8 and 9, into engagement with the bevel gear 132, so that in this way the operator can whenever desired transmit the drive from the stepping motor 130 to the shaft 137. This shaft 137 drives a bevel-

gear transmission

139, 140 which serves to rotate a shaft 141 which has a threaded portion 142 extending threadedly through the tapped bore of a sleeve 143 which is thus vertically displaceable with respect to the mechanism 144 which is schematically indicated in FIG. 8. This mechanism 144 provides, for example, a rod similar to the rod 109 of FIG. 7 which is vertically displaced with the sleeve 143 so as to actuate components such as the rod 104 and the bell crank 113 in order to shift a specimen stage such as the stage 101 of FIG. 7 to the right and left, for example, as shown by the doubleheaded arrow adjacent the roller 107 in FIG. 7. The shaft 137 is of course restrained in any suitable way against axial displacement.

In the same way the operator can shift the handle 153 to the right, as viewed in FIGS. 8 and 9, so as to displace the bevel gear 152 along the shaft 149 into engagement with the teeth 133 of the gear 132, and now the rotation of the stepping motor will be transmitted from the shaft 149 through the bevel-gear transmission 151 to a rod -146 which is thus rotated. This rod 146 has a threaded portion 147 extending threadedly through a tapped bore of an element 148 which is thus displaced vertically with respect to the unit 149 which includes, for example, a rod 108 which moves vertically with the element 148 and which actuates a structure such as that shown in FIG. 7 actuated by the rod 108 to displace the specimen stage 101 forwardly and rearwardly as indicated by the double-headed arrow adjacent the roller 106 in FIG. 7. The components shown in FIGS. 8 and 9 to the left of the shaft 131 are identical with those situated to the right of this shaft and operate in the same way to provide the second transmission from the single stepping motor 130. Thus, the pedestal 150 corresponds to the pedestal 138.

It will be noted that the manually operable structure such as the handwheel 19 is readily accessible to the operator so that manual adjustments can be very conveniently carried out. Because the magnetic clutch 12 is situated between the handwheel 19 and the stepping motor 21 it is possible to carry out the manual adjustment while exerting relatively small forces since it is not required to simultaneously turn the stepping motor.

The provision of a structure as shown in FIGS. 1 and 2 which forms a single unitary assembly greatly simplifies the mounting of the structure on the corpuscular ray device. The use of the universal joints to compensate for manufacturing tolerances are of particular significance with a corpuscular ray device similar to an electron microscope because when the manually engageable structure such as the handwheel 19 is located at an elevation which is convenient for the operator, the structure must extend all the way up to the specimen holder, and the structure, particularly where the device has multiple stage type of construction, must bridge parts whose sizes have noticeable tolerances.

Since the end component of the spindle 1 which is situated adjacent the electromagnetic clutch must in any event undergo certain operations during the manufacture of the structure, it is of advantage for this reason also to situate the handwheel for manual actuation of the specimen adjustment at this component of the spindle -1.

As has already been pointed out above, a particular advantage of the use of a stepping motor for adjusting the specimen resides in the fact that the speed of adjustment can be adapted to the particular special relationships of the corpuscular ray device, primarily the particular degree of enlargement, and this adaptation can be brought about in an exceedingly simple manner. Furthermore, as was indicated above, only a single adjusting lever 49 is required to bring about adjustment of the speed of movement of the specimen as well as the direction of movement thereof, the adjustments resulting from the symmetrical arrangement of the electrical switching elements with respect to the zero position. This zero position can be defined by a suitable detent structure which is not illus- \trated.

Of course, the adjustable electrical structure can take the form not only of a potentiometer but also of adjustable capacitors or another type of adjustable electrical element. The adjusting structure shown in FIG. 3 is preferably arranged at the control panel of the electron microscope in such a way that the lever 49 with its upper manually engageable end extends from the cover plate of the control panel while the remaining elements of the drive are situated beneath this plate.

While it is possible to situate the adjusting rods such as the rods 40 and 41 in a common plane which contains the axis of the adjusting lever, such an arrangement would not provide any independence of the movements of the rods with respect to each other since when the adjusting lever extends vertically the adjusting rods would be situated one over the other at the same side of the adjusting lever. The preferred construction which is shown in the drawing and described above has the pair of rods extending perpendicularly with respect to each other and pressing against the adjusting lever so that simultaneous but independent adjustments can be provided in this way. Thus, with this construction it is possible to provide movement of the specimen stage or tiltable specimen cartridge within a given plane in any desired direction with movements in a pair of different coordinates being carried out simultaneously. It will be noted that the ends 46 and 47 of the rods 40 and 41 are large enough to maintain these rods in engagement with the spherical portion 48 of the lever 49 irrespective of the extent of adjustment of the latter. Therefore the surfaces of engagement between the lever 49 and the rods 40 and 41 will never become displaced to a location where they do not engage each other.

The pulse counter 57 referred to above is an electronic pulse counter and the pulse transmitter 57 is also of an electronic or an electrical-mechanical construction well known to those skilled in the art. The pulse transmitter can, for example, take the form of a device of the type used for deflection impulses of electron ray-oscillographs.

The use of a preliminarily adjustable pulse counter provides the possibility of directly controlling details of the specimen whose coordinates are fed to the pulse counter during the preliminary setting thereof, so that in this way it is only required to actuate a key, for example, in order to bring about the desired adjustment.

Such adjustment of the specimen can be used not only to bring about a predetermined positioning of another region of the specimen or to produce a predetermined angular position of the specimen, but also this construction can be used to compensate for undesired wandering of the specimen. Such wandering can, for example, take place during tilting of the specimen when the tilting axis is not precisely situated at the specimen, as is the case, for example, when stereo-investigations are required. In this case it is possible by way of the stepping motors and in particular by the use of preliminarily adjustable pulse counters which permits only one predetermined number of pulses to be transmitted to the stepping motors as a result of the preliminary adjustment of the pulse counter,

to bring about a compensation. Furthermore, undesired wandering of the specimen as a result of temperature influences can occur. In the event that such a temperature influence, which will in general become noticeable within a certain period of time, is quantitatively known, then such an influence can be fed to the pulse counter and in a corresponding manner the number of pulses can be used to provide a predetermined movement of the specimen by way of the stepping motor which will be opposed to the undesired movement resulting from the temperature influence.

We claim:

1. In a corpuscular ray device which has an evacuated interior for receiving a specimen which is to be investigated and which is to be adjusted in the evacuated interior of the device by way of control apparatus situated substantially at the exterior thereof, said control apparatus comprising adjusting means situated in part at the exterior of the device for adjusting the position of a specimen therein, stepping motor means mechanically engageable with said adjusting means for actuating the latter, and pulse transmitter means electrically connected to said stepping motor means for transmitting thereto a predetermined number of control pulses which determine the magnitude of the adjustment of the specimen at a frequency which determines the speed of movement of the specimen, said pulse transmitter means actuating said stepping motor means at each pulse to an extent determined by the smallest required adjustment of the specimen, said pulse transmitter means including a frequencydetermining circuit, frequency control means located in said circuit for providing a selectable pulse frequency, said frequency control means including a movable component movable from a zero position where no pulse is transmitted to said stepping motor means in a pair of opposed directions for adjusting the impedance provided by said frequency control means in the same way in each of said directions, and contact means connected with said movable component for movement therewith and connected electrically with said stepping motor means to provide through the circuit thereof operation of said stepping motor means in one direction when said movable component moves in one direction and operation of said stepping motor means in an opposed direction when said movable component moves in the other of said directions of movement thereof.

2. The combination of claim 1 and wherein a specimen holder is situated within the corpuscular ray device to hold the specimen therein, said adjusting means including rods which respectively extend in a vacuum-tight manner from the interior to the exterior of the device, and said stepping motor means actuating said rods to move the specimen relative to the corpuscular ray.

3. The combination of claim 2 and wherein said specimen holder includes a tiltable cartridge, and said stepping motor means providing adjustment of the angle between the specimen and the corpuscular ray.

4. The combination of claim 2 and wherein said specimen holder includes a specimen stage, and said stepping motor means providing movement of said stage perpendicularly with respect to the corpuscular ray.

5. The combination of claim 2 and wherein a pair of mutually perpendicular rods coact with the specimen holder to adjust the latter, said rods also extending perpendicularly with respect to the corpuscular ray, and said stepping motor means coacting with said rods for independently adjusting the latter separately from each other.

6. The combination of claim 5 and wherein said stepping motor means includes a plurality of stepping motors respectively mechanically connected with said rods.

7. The combination of claim 5 and wherein a single stepping motor is mechanically engageable with said rods for adjusting the latter, and clutch means situated between and coacting with said rods and stepping motor for selectively connecting the latter mechanically with one or the other of said rods.

8. The combination of claim 2 and wherein said stepping motor means includes a stepping motor and said ad justing means includes an adjusting spindle mechanically connected to said stepping motor to be rotated thereby, and the rotary movement of said spindle being converted into translational movement of a rod which adjusts the position of the specimen holder.

9. The combination of claim 1 and wherein a manually operable means is mechanically connected with said adjusting means for manually actuating the latter.

10. The combination of claim 9 and Wherein said adjusting means includes an adjusting spindle, said stepping motor means including a stepping motor, and magnetic clutch means situated between said stepping motor and said spindle for establishing a mechanical connection between the latter and said stepping motor.

11. The combination of claim 1 and wherein an axially shiftable rod carries said movable component of said frequency control means and said contact means for adjusting the impedance provided by said frequency control means during shifting of said rod to determine the frequency of the pulses, and stationary contact means situated along the path of movement of said contact means carried by said rod and along which the latter contact means slides during axial movement of said rod for controlling the circuit of said stepping motor means.

12. The combination of claim 11 and wherein a manually swingable lever extends substantially perpendicularly to said rod, spring means urging said rod at one end thereof into engagement with said lever, said lever having a pair of opposed ends one of which is to be manually engaged, and support means engaging the other end of said lever to support the latter for swinging movement axially of said rod.

13. The combination of claim 12 and wherein said stepping motor means includes a plurality of stepping motors controlled by said lever, a plurality of said axially movable rods respectively extending in difierent directions and a plurality of spring means respectively urging said rods into engagement with said lever, said support means supporting said lever for swinging movement in different directions axially of said rods.

14. The combination of claim 13 and wherein said rods respectively have axes situated in a common plane through which said lever extends.

15. The combination of claim 13 and wherein a pair of said rods are situated at with respect to each other and respectively press against said lever, and said support means supporting said lever for swinging movement in all directions.

16. The combination of claim 15 and wherein said lever has a spherical portion engaged by said support means.

17. The combination of claim 16 and wherein said lever also has a spherical portion engaged by said rods, and the ends of said rods which respectively engage said lever being large enough to have the positions of both rods determined by the position of said lever.

18. The combination of claim 1 and wherein a preliminarily adjustable pulse counter means is electrically connected between said pulse transmitter means and said stepping motor means.

19. The combination of claim 1 and wherein said adjusting means includes an elongated adjusting spindle while said stepping motor means includes a stepping motor forming a unitary assembly with said adjusting spindle, and electromagnetic clutch means and transmission means situated between said spindle and stepping motor.

20. The combination of claim 19 and wherein said spindle includes a plurality of components and universal joints interconnecting said components.

21. The combination of claim 20 and wherein a handwheel is carried by one of said components.

22. The combination of claim 21 and wherein said magnetic clutch means has an output shaft situated adjacent an end of said spindle and said spindle having at said end thereof a pin-and-slot connection with said out put shaft constraining said spindle to rotate with the latter shaft while freeing said spindle for axial movement with respect to said shaft.

23. The combination of claim 22 and wherein one of said components of said spindle is adjacent said electromagnetic clutch means and carries said handwheel.

10 24. The combination of claim 23 and wherein a sec-- ond component of said spindle is situated adjacent said component which is adjacent said clutch means, and a bridging member extending around said handwheel and said component adjacent said clutch means, said bridging member connecting said second component of said spindle with said clutch means and stepping motor.

25. The combination of claim 13 and wherein said rods are adjustable about the axis of said lever to compensate for changes in the position of an image of a specimen in the corpuscular ray device so as to provide through said rods adjustments providing an image movement corresponding to the movement of said lever in a given direction irrespective of other influences on the image movement in the device.

References Cited UNITED STATES PATENTS 2,496,051 1/1950 Hillier 25049.5

3,099,777 7/1963 Davis 318-39 FOREIGN PATENTS 1,035,811 8/1958 Germany.

ARCHIE R. BORCHELT, Primary 'Examiner S. C. SHEAR, Assistant Examiner