US3757117A - Earrangement for the magnification adjustment of an electron microscop - Google Patents

Earrangement for the magnification adjustment of an electron microscop Download PDF

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Publication number
US3757117A
US3757117A US00289531A US3757117DA US3757117A US 3757117 A US3757117 A US 3757117A US 00289531 A US00289531 A US 00289531A US 3757117D A US3757117D A US 3757117DA US 3757117 A US3757117 A US 3757117A
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digital
counter
output
input
converter
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US00289531A
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English (en)
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K Muller
V Rindfleisch
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/02—Details
    • H01J37/24—Circuit arrangements not adapted to a particular application of the tube and not otherwise provided for

Definitions

  • the setting device includes a digital counter, preferably a forwardbackward counter, connected to the input of the control circuit through a digital-to-analog converter.
  • a digital-to-digital converter programmed with a series of predetermined control settings, is connected between the output of the digital counter and the input to the digital-to-analgo converter to serve as a read-only memory for supplying a programmed magnification setting in response to address signals from the counter.
  • a pulse source preferably pushbutton-controlled, provides stepping pulses for adjusting the output voltage of the setting device to achieve desired values of magnification as indicated by a numeric display device connected to the output of the digital counter.
  • electromagnetic coils may be used to provide the desired magnification and focusing.
  • the first three lenses primarily influence the magnification of the microscope, while the objective lens controls the focus.
  • each electromagnetic lens is provided with a control circuit for adjusting the coil current.
  • a conventional setting device for providing variable control voltages to the input of such a control consists of merely a potentiometer, either continuously variable or preferably variable in steps by means of a multi-position selector switch.
  • a proposed circuit that combines the above described control and regulating functions includes a power amplifier with its input connected to the output of a differential amplifier having two inputs, one for a control voltage and the other for a stable reference voltage.
  • the output of the power amplifier is connected in series with the electromagnetic lens coil and a measuring resistor across a current source.
  • Current regulation is obtained by inverse feedback from the measuring resistor to the control input of the differential amplifier.
  • Control voltages related to different coil currents are obtained from a setting device, such as the above mentioned multiposition potentiometer, which is also connected to the input of the difi'erential amplifier.
  • An object of the invention is to provide a setting device capable of simultaneously adjusting the coil currents of a plurality of electromagnetic lenses according to individually programmed values for each lens.
  • Another object of the invention is to provide a setting device having a numeric display, preferably independently resettable, for indicating the value of the function being controlled.
  • a setting device for a control and regulating circuit for the electromagnetic coil current of electron microscope lenses comprises a digital counter having an output connected to a digitalto-analog converter for supplying a broad range of incremental control voltages to the control input of the control and regulating circuit in response to stepping pulses applied to the input of the counter.
  • the digital counter is a forward-backward counter to facilitate either positive or negative adjustment of the lens current.
  • a digital-to-digital converter is connected between the output of the digital counter and the input to the digital-to-analog converter.
  • This device is particularly useful with a control and regulating circuit for adjusting coil current in lenses that determine the magnification of an electron microscope, such as the condenser, diffraction, and intermediate lenses described earlier.
  • the digital-to-digital converter acts as a read-only memory and can be programmed with predetermined setting values for a desired number of magnification powers.
  • the output of the digital counter corresponds to an address for one of the setting values, which is then fed to the digital-to-analog converter.
  • setting values for the lens control circuit which may vary substantially from one magnification power to the next, can be easily and rapidly selected by using only a relatively small number of steps from the digital counter.
  • Another advantage of using the digital-to-digital converter between the counter and the digital-toanalog converter is that more than one lens current can be set simultaneously by operation of a single digital counter, even if the adjustment value for one of the lenses is different than for another. For example, if the electron microscope has three lenses that influence the magnification, adjusting one lens alone causes distortion, even at low magnification powers. It is much better to adjust all three lenses simultaneously.
  • the output of the digital counter is connected to a separate digital-to-digital converter connected to a digital-toanalog converter for each lens.
  • the individual digital-to-digital converters are programmed with the setting values for their respective lenses that correspond to each magnification value called for by the digital counter.
  • the digital-counter used to adjust the magnification of the electron microscope preferably is also connected, through an additional digital-to-digital converter to a setting device for the control circuit of the objective lens of the microscope so as simultaneously to adjust the magnification and the focus.
  • the additional digital-to-digital converter may be connected to means for driving the object stage or other specimen adjustment means to change the focus by moving the specimen instead of changing the objective lens current.
  • the output digital counter used to adjust the magnification preferably is connected through still another digital-to-digital converter to a numeric display device in order to identify the magnification steps selected in each case.
  • the other additional digital-todigital converter is programmed to convert the counter output to signals causing the numeric display to read out a number indicating the magnification or diffraction lengths.
  • FIGURE shows a block diagram of an arrangement for the magnification adjustment of an electron microscope according to the invention.
  • the magnification system of a typical electron microscope includes three electromagnetic lenses, Ll, L2, and L3.
  • Lil may be a condenser lens, L2 a diffraction lens, and L3 an intermediate lens.
  • the current through each of the lenses is adjusted by means of identical control circuits S1, S2, and S3.
  • Each control circuit comprises a power amplifier L preceded by a differential amplifier D.
  • Each lens L1 through L3 is connected in the output circuit of its corresponding power amplifier L in series with a measuring resistor M.
  • An inverse feedback loop from each measuring resistor M transmits a regulating voltage proportional to the currents through lenses L1, L2, and L3 to the inputs Ell, E2, and E3 of the control circuits S1, S2, and S3, respectively. Also connected to the inputs E1 through E3 is a setting device according to the present invention.
  • the setting device includes a digital counter 1, which is designed as a forward-backward counter. Stepping pulses are fed to the forward counting input 2 and backward counting input 3 of digital counter 1 via lines 4 and 5. The stepping pulses are controlled by means of keys 6, 7 of a control panel 8. In the embodiment example shown, the counter 1 has five stages and can therefore be switched in 2 32 steps.
  • the outputs 9 to 13 of the digital counter l are connected to digital-to-digital converters M, 15, 16, which act as read-only memories. In these digital-to-digital converters, individual current control programs associated with the lenses L1 to L3 are set. At the outputs of the digital-to-cligital converters 14 to 16, digital signals according to the correspondingly set step of the counter are available. These are converted into analog voltage values via the succeeding digital-to-analog converters 17, 18 and 19.
  • the output 20 of the digital-toanalog converter 17 is connected to the input E1, the output 21 of the digital-to-analog converter 18 to the input E2, and the output 22 of'the digital-to-analog converter 19 to the input E3.
  • a defnite current value specific for each step of the counter l, is thus fed to each lens L1 through L3 which can be matched optimally to the characteristics of all lenses with a view to most distortion-free imaging.
  • a digital-to-digital converter 23 is also connected with the digital counter I. It serves as a read-only memory and controls a numerical indicating device 24. Digital-to-digital converter 23 contains in digital form the summed program of the digital-to-digital converters 14 to 16 with regard to the magnification of the microscope and controls the indicating device 24, which preferably shows numerals which indicate the magnification or diffraction lengths.
  • Digital-to-digital converter 23 or alternatively an additional read-only memory (not shown) also provides digital signals at its output for controlling the adjustment sensitivity of those parts of the microscope which determine the focusing current or adjust the position of the object.
  • the output signal affects the focusing current of the objective lens
  • the output signal acts on the drive of an object stage or of other specimen-adjustment means.
  • a digital counter having an input and an output for supplying a digital signal equal to the count of stepping pulses fed to the input;
  • a digital-to-analog converter having an input connected to the output of the digital-to-digital converter and an output connected to the input of the control and regulating circuit for one of said lenses.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Electron Sources, Ion Sources (AREA)
US00289531A 1971-09-28 1972-09-15 Earrangement for the magnification adjustment of an electron microscop Expired - Lifetime US3757117A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE2149108A DE2149108C3 (de) 1971-09-28 1971-09-28 Einrichtung zur VergröBerungseinstellung eines Elektronenmikroskops

Publications (1)

Publication Number Publication Date
US3757117A true US3757117A (en) 1973-09-04

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US00289531A Expired - Lifetime US3757117A (en) 1971-09-28 1972-09-15 Earrangement for the magnification adjustment of an electron microscop

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US (1) US3757117A (xx)
JP (1) JPS4843261A (xx)
DE (1) DE2149108C3 (xx)
GB (1) GB1394102A (xx)
NL (1) NL7209350A (xx)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4451737A (en) * 1981-06-24 1984-05-29 Hitachi, Ltd. Electron beam control device for electron microscopes
US4818873A (en) * 1987-10-30 1989-04-04 Vickers Instruments (Canada) Inc. Apparatus for automatically controlling the magnification factor of a scanning electron microscope
US5008536A (en) * 1988-12-05 1991-04-16 Hitachi, Ltd. Electron microscope having electrical and mechanical position controls for specimen and positioning method
US6653634B1 (en) * 1999-05-24 2003-11-25 Hitachi, Ltd. Method of measuring length with scanning type electron microscope

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5354465A (en) * 1976-10-28 1978-05-17 Jeol Ltd Lens control circuit for electromicroscope or the like
JPS563125Y2 (xx) * 1977-09-16 1981-01-23
JPS54107646U (xx) * 1978-01-17 1979-07-28
JPS5814460A (ja) * 1981-07-17 1983-01-27 Internatl Precision Inc 電子顕微鏡の焦点合わせ方法及びこの方法を応用した像撮影方法及び装置
JPS63207612A (ja) * 1987-02-24 1988-08-29 日本碍子株式会社 セラミツク押出法及びそれに用いる装置

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4451737A (en) * 1981-06-24 1984-05-29 Hitachi, Ltd. Electron beam control device for electron microscopes
US4818873A (en) * 1987-10-30 1989-04-04 Vickers Instruments (Canada) Inc. Apparatus for automatically controlling the magnification factor of a scanning electron microscope
EP0314520A2 (en) * 1987-10-30 1989-05-03 Vickers Instruments (Canada) Inc An apparatus for automatically controlling the magnification factor for a scanning electron microscope
EP0314520A3 (en) * 1987-10-30 1990-02-07 Vickers Instruments (Canada) Inc An apparatus for automatically controlling the magnification factor for a scanning electron microscope
US5008536A (en) * 1988-12-05 1991-04-16 Hitachi, Ltd. Electron microscope having electrical and mechanical position controls for specimen and positioning method
US6653634B1 (en) * 1999-05-24 2003-11-25 Hitachi, Ltd. Method of measuring length with scanning type electron microscope

Also Published As

Publication number Publication date
DE2149108A1 (de) 1973-04-05
NL7209350A (xx) 1973-03-30
GB1394102A (en) 1975-05-14
DE2149108C3 (de) 1975-05-15
DE2149108B2 (de) 1974-10-03
JPS4843261A (xx) 1973-06-22

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