JPS6024534B2 - Electromagnetic lens current variable device for electron microscopes and similar devices - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electron microscopes and similar devices, and in particular to an electromagnetic lens, in which a pulsating wave signal is applied as a repetitive signal to the electromagnetic lens in order to adjust the focus or to perform fusion. The present invention relates to an electromagnetic lens current variable device for use in electron microscopes and similar devices, which is capable of superimposing and combining a reference signal with a reference signal.

Generally, electromagnetic lenses are used as lenses for electron microscopes and similar devices, and have traditionally been used for focusing adjustment (focusing) and fusion (separation of the lens and directing the electron beam to the center of the lens). For adjustment), a reference signal (DC) from a reference signal source is superimposed with a pulsating wave signal (for example, a sine wave signal or a sawtooth signal) as a repetitive signal, and then the reference signal (DC) is supplied as a reference signal (DC) from a reference signal source. After adjusting the signal value appropriately and completing focus adjustment and axis alignment,
An operator opens a switch to stop the supply of the pulsating wave signal to the electromagnetic lens.

Here, when focusing the lens, a signal is repeatedly superimposed on the reference signal, and these signals are supplied to the electromagnetic lens to be focused, and the search for the focal current is performed by changing the reference signal as appropriate. In this case, changing the reference signal value causes the in-focus image portion appearing on the CRT to move across the screen.

Then, for example, when this focused image portion is aligned with the center position of the screen, it is determined that the image is in focus. Also, when fusing lenses, a signal is repeatedly superimposed on the reference signal and supplied to the electromagnetic lens to be fusing, but in this case, C
The image appearing on RT is rotated. Then, when the reference signal value is changed, the rotation center of the image moves on the screen, so when the image rotation center is aligned with, for example, the screen center position, axis alignment has been performed. However, this type of secondary pulsating wave signal supply/stop means stage has the following problems.

In other words, as shown in Figure 1, the characteristics of magnetic flux density B (hysteresis ring line ) This is a problem caused by. To explain this more specifically using Fig. 2, when the coil current is 1^ and the magnetic flux density of the electromagnetic lens is B^, a pulsating wave signal (1^→18→1^→lc→1^) is generated in the coil. ), a hysteresis loop connecting points AI, B, A2, C, and AI is drawn, but at this time, the pulsating wave signal is connected to points AI-B-A2.
When it is turned off between, it stops at point A2 and the magnetic flux density becomes B^
2 and turns off between points A2-C-AI, AI
It stops at a point, and the magnetic flux density becomes B^.

Since the value of the magnetic flux density in the electromagnetic lens differs depending on the timing of turning on and off the pulsating wave signal, there is a problem in that it becomes difficult to perform focus adjustment operations and axis alignment operations.

The present invention aims to solve such problems, and by superimposing a pulsating wave signal as a repetitive signal on a reference signal whose output value can be adjusted and supplying it to an electromagnetic lens, focus adjustment and axis adjustment can be performed. When searching for alignment, regardless of the timing of turning on and off the pulsating wave signal,
By ensuring that the value of the magnetic flux density in the electromagnetic lens remains constant before supplying the pulsating wave signal and after stopping the supply, thereby avoiding the influence of hysteresis, focus adjustment operations and It is an object of the present invention to provide an electromagnetic lens current variable device for electron microscopes and similar devices, which allows axis alignment operations to be performed easily and reliably. Therefore, in the electromagnetic lens current variable device of the present invention, a reference signal source whose output value can be adjusted is connected to the electromagnetic lens, and a pulsating wave signal as a repetitive signal is superimposed on the reference signal from the reference signal source. In an electron microscope or similar device in which a pulsating wave signal source is connected to the electromagnetic lens via a first switch, a reference value in the pulsating wave signal from the pulsating wave signal source is detected and the same pulsating wave signal is detected. A reference value detection means outputs a synchronous trigger pulse train signal that turns on when the reference value is reached, and a second switch instructs supply and stop of the pulsating wave signal, and the second switch commands the supply and stop of the pulsating wave signal. Based on the signal and the synchronized trigger pulse train signal from the reference value detection means, the pulsating wave signal is started to be supplied to the electromagnetic lens from the reference value state, and the supply of the pulsating wave signal is stopped at the reference value state. In order to turn on and off the first switch, an edge trigger synchronization circuit has its input side connected to the reference value detection means and the second switch, and its output side connected to the first switch. It is characterized by being

Hereinafter, an electromagnetic lens current variable device for an electron microscope and its similar devices as an embodiment of the present invention will be explained with reference to the drawings.
Figures a to g are waveform diagrams for explaining the effect.

As shown in FIG. 3, a lens power supply 2 is connected to the lens coil of the electromagnetic lens L.
A reference voltage source 3 whose output value can be adjusted is connected to the reference voltage source 3 , and a pulsating wave signal source 5 is connected via a first switch 4 .

As a result, before the first switch 4 is turned on, the reference voltage signal (DC) from the reference voltage source 3 as a reference signal source is
is amplified by the amplifier of the lens power supply 2 and supplied to the lens coil, and when the first switch 4 is turned on, a reference voltage signal from the reference voltage source 3 and a pulsating wave signal as a repetitive signal from the pulsating wave signal source 5 are generated. is added by the lens power supply, amplified by the amplifier, and then supplied to the lens coil 1. In this embodiment, a sine wave signal Sp as shown in FIG. 4a is used as the signal from the pulsating wave signal source 5, but other signals such as those shown in FIG. 4b,
An appropriate repetitive signal such as a mirror-tooth wave signal Sp' or a pulse train signal Sp'' as shown in c can be used.

By the way, the pulsating wave signal Sp from the pulsating wave signal source 5 is also input to a comparator circuit 6 as a reference value detection means, and this comparator circuit 6 is connected to the pulsating wave signal Sp and the reference power source. 7, the pulsating wave signal Sp is compared with the signal corresponding to the reference value in the pulsating wave signal Sp.
It is possible to detect a reference value at and output a synchronized trigger pulse train Ss signal as shown in FIG. 4d, which turns on when the pulsating wave signal Sp reaches the reference value.

Furthermore, in order to command the supply and stop of the pulsating wave signal Sp to the electromagnetic lens L, a command signal Sc as shown in FIG.
A second switch 8 capable of outputting a signal is provided, and a command signal Sc from this second switch 8 is input to the input side of an edge trigger synchronization circuit 9.

In addition, on the other input side of this edge trigger synchronization circuit 9,
A synchronous trigger pulse train signal Ss from the comparison circuit 6 is input.

When this edge trigger synchronization circuit 9 receives signals Ss and Sc as shown in FIG. 4d and e from its two input terminals, it first rises after the command signal Sc shown in FIG. 4e turns on. Taking the pulse SS of Fig. 4 d, this pulse S
A signal is emitted by the rise of s, and the signal shown in Fig. 4 e
4d, which first rises after the command signal Sc turns off as shown in FIG.
The device captures the pulse Ss2 and emits another signal according to the rise of this pulse Ss2.Receiving this signal from the edge trigger synchronization circuit 9, the switching power supply 10
A control signal Sco as shown in FIG. f is supplied to the control end of the first switch 4. This allows the second
The switch 8 changes the pulsating wave signal S from the reference value state as shown in FIG.
The supply of p is started, and the pulsating wave signal Sp is generated at the above reference value.
supply can be stopped.

Therefore, the value of the magnetic flux density in the electromagnetic lens L can always be kept constant before the supply of the pulsating wave signal Sp and after the supply is stopped (for example, B^, in Fig. 2), thereby eliminating hysteresis. It is possible to eliminate the effects of
As a result, focus adjustment operations, enemy alignment operations, etc. can be performed extremely easily and with high reliability.

Note that the timing at which the second switch 8 is turned off is based on the reference voltage source 3.
A pulsating wave signal as a repetitive signal from the pulsating wave signal source 5 is superimposed on the reference voltage from the pulsating wave signal source 5, and the reference voltage value is changed as appropriate while the pulsating wave signal is being supplied to the electromagnetic lens L to be focused and aligned. By doing this, it is possible to complete the movement of the in-focus image portion appearing on the CRT to a predetermined position (for example, the center position) on the CRT screen, or to move the center of rotation of the image appearing on the CRT to a predetermined position on the screen as well. (for example, after the movement to the center position) is completed.

As described in detail above, according to the electromagnetic lens current variable device for an electron microscope and similar devices of the present invention, a reference signal source whose output value can be adjusted is connected to the electromagnetic lens, and a reference signal source whose output value is adjustable is connected to the electromagnetic lens. In an electron microscope or similar device in which a pulsating wave signal source is connected to the electromagnetic lens via a first switch in order to superimpose a pulsating wave signal as a repetitive signal on a reference signal, the pulsating wave signal from the pulsating wave signal source is a reference value detection means for detecting a reference value in the wave signal and outputting a synchronized trigger pulse train signal that turns on when the pulsating wave signal reaches the reference value; and a second means for instructing supply and stop of the pulsating wave signal. and starts supplying the pulsating wave signal to the electromagnetic lens from the reference value state based on the command signal from the second switch and the synchronized trigger pulse train signal from the reference value detection means. In order to stop supplying the pulsating wave signal in the state of the reference value, an edge trigger synchronization circuit that turns on and off the first switch has its input side connected to the reference value detection means and the second switch. In addition, with a simple configuration in which the output side is connected to the first switch, it is possible to eliminate the effects of hysteresis during focus adjustment operations, axis alignment operations, etc. It has the advantage that it can be performed extremely easily, efficiently, and with high reliability.

[Brief explanation of the drawing]

Both Figures 1 and 2 are hysteresis curve diagrams for explaining a general magnetic hysteresis loop, and Figures 3 and 4 are hysteresis curve diagrams for explaining a general magnetic hysteresis loop.
The figure shows an electromagnetic lens current variable device in an electron microscope and similar devices as an embodiment of the present invention.
The figure is a block system diagram thereof, and each of FIGS. 4a to 4g is a waveform diagram for explaining its operation. 1... Lens coil, 2... Lens power supply, 3... Reference voltage source as a reference signal source, 4
. . . First switch, 5 . . . Pulsating wave signal source, 6 . . . Comparison circuit as reference value detection means, 7
...Reference power supply, 8...Second switch, 9
...Edge trigger synchronous circuit, 10... Switching power supply, L... Electromagnetic lens. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. A reference signal source whose output value can be adjusted is connected to the electromagnetic lens, and a pulsating wave signal as a repetitive signal is superimposed on the reference signal from the reference signal source by connecting the electromagnetic lens with a first switch. In an electron microscope or similar device to which a pulsating wave signal source is connected, a synchronization device that detects a reference value in the pulsating wave signal from the pulsating wave signal source and turns on when the pulsating wave signal reaches the reference value. A reference value detection means for outputting a trigger pulse train signal and a second switch for commanding supply and stop of the pulsating wave signal are provided, and a synchronized trigger is provided by a command signal from the second switch and a synchronous trigger from the reference value detection means. The first switch is turned on and off in order to start supplying the pulsating wave signal to the electromagnetic lens from the reference value state based on the pulse train signal and to stop supplying the pulsating wave signal at the reference value state. An electron microscope characterized in that an edge trigger synchronization circuit has an input side connected to the reference value detection means and the second switch, and an output side connected to the first switch. An electromagnetic lens current variable device in a similar device.