JPS5873949A - Displayer of multiplying-factor fo scanning electron microscope - Google Patents

Abstract

PURPOSE:To make the multiplying factor of the image of a final photograph to coincide with the multiplying factor of display constantly, by correcting the multiplying factor of the display according to the photographing multiplying factor when the size of the final photograph is not equal to that of the image surface of a CRT, by continuously constituting a display-multiplying-factor correcting circuit having a correction-coefficient change-over switch between a multiplying-factor displaying circuit and a photographing-multiplying-factor switching equipment. CONSTITUTION:When the resistance value of a correction-coefficient change-over switch 19 is represented by (Rfk) and the resistance value of a feedback loop is represented by (Re), the output voltage (Vo') of the fixed-point part of multiplying-factor display is represented by the equation of Vo=(Re/Rfk).Vo. Therefore, by properly selecting the values (Rfk) and (Re), the multiplying-factor display can be corrected in conformity with the photographing condition, and the multiplying factor of obtained data can be adjusted to an accurate value irrespective of the kind of films. When photographing is performed with a film with the size of 4 inches multiplied by 5 inches, generally, the multiplying factor is supposed to be equal. In such a case, a correction coefficient for a polaroid film with the size of 95mm. multiplied by 72mm. should be adjusted to 0.8; that for a Brownie negative film, to 0.6.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a magnification display device for a scanning electron microscope (hereinafter referred to as SEM).

In a scanning electron beam device such as an SEM, a finely focused electron beam is scanned over the sample surface, and detection signals such as secondary electrons obtained from the sample are detected as brightness modulation signals of a cathode ray tube that deflects and scans in synchronization with this scanning operation. By using this, a sample scanned image is displayed on a cathode ray tube screen. The magnification of the scanned image in this case is determined by the following formula, and is normally displayed on the □ magnification display.

Recently, a device has been developed that can display this magnification value on a cathode ray tube screen and imprint it on the photograph at the same time as the image. In such an apparatus, there is no problem when the developed photograph is the same size as the cathode ray tube screen, but there is a problem when the film size is different from the cathode ray tube screen. For example, if the film size is 4 x 5 inch Polaroid film and the device is adjusted so that it is the same size as the CRT screen, the commonly used 95 x 72
When using Polaroid film (3), the actual magnification on the photograph is 0.8 times the magnification value. Conversely, negative film may be used to enlarge the image to a size larger than that of a cathode ray tube, but in this case a similar situation occurs. That is, if the size of the final photograph is not the same as the screen of a cathode ray tube (hereinafter referred to as CRT), problems arise such as the photographing magnification and display magnification differing.

FIG. 1 is a block diagram of a conventional SEM. The electron beam generated and accelerated by the electron gun 1 is focused by a condenser lens 2 and a final stage lens 4, and is deflected by a deflection coil 3 to irradiate and scan the surface of a sample 5.

Secondary electrons 15 generated from the surface of the sample 5 are detected by a detector 12, and sent via an amplifier 13 to a CRT 14 as a brightness modulation signal. At this time, the CRT 14 is deflected and scanned in synchronization with the electron beam scanning on the sample 5.
A sample image is obtained at RT14.

The above <CRT14. The above image magnification is related to the electron beam scanning width on the CRT screen and the electron beam scanning width on the sample 5, but in general: Since the electron beam scanning width on the screen of the CRT 14 is constant, The magnification is determined by the scanning width above. Further, the scanning width on the sample 5 is proportional to the deflection coil current flowing through the deflection coil 3. This deflection coil current converts the scanning signals generated by the deflection waveform generators 7X and 7Y into the magnification switch 9. It is controlled by passing through deflection current control circuits 6X and 6Y whose amplification degree changes by.

The magnification switch 9 is connected to a magnification display circuit 10, and the magnification display circuit 10 calculates the magnification based on the output signal of the magnification switch 9, and the result is displayed on the display 11 and is displayed on the CRT character display circuit. 16 and is also displayed on CR, T14. Note that 8X and 8Y are CRT deflection circuits that output to the deflection coil of the CRT 14.

FIG. 2 is a circuit diagram showing an example of the magnification calculation circuit surrounded by the broken line in FIG. 1. The magnification switch 9 includes a deflection coil current detection resistor, changeover switches 17X and 17Y, and a variable resistor 18X for continuously varying the deflection coil current.

It is composed of 18Y etc. Modify the current supplied to the deflection current control circuit 6X and the deflection coil 3. .

The deflection coil current detection resistance value is Rt@', and the resistance value of the variable resistor 18X for continuously variable deflection coil current is R1.

L t Re I If the waveform voltage input from the deflection waveform generation circuit 7X is Vl, then Io''((Ro+R++)/R-Rt-)Vl
−(1). However, R” Ro + Rt +
It is R1.

In addition, the resistance of the 1 magnification display board number selection switch 178 is set to Rf.
+m4 The resistance of the variable resistor 188 for continuously variable magnification display is the same value Rt as the variable resistor 18X for continuously variable deflection coil current.
, Rt''-RQ, and the input voltage of several parts of the 1 magnification display board is Vt2
Then, the output electric field v0 is.

Vo”(R-Rt-/(Ro, +Rx))Vt
*=(Vtz /V+)(1/Io) −
(2) becomes. In this case too, R=, Ro +R1+, Rt
It is.

The above V+ and Vl2 are constant values, and the 91 magnification is inversely proportional to Io, so vo is proportional to the magnification. In this embodiment, instead of making Rtwa proportional to the entire range of change in Rta, Rza is set to a value in which the same significant figure is repeated every three steps, for example, 1Ω, 2Ω, and 5Ω.

10Ω, 20Ω, 50Ω, 100Ω...), while Rt
m uses three types of resistance values repeatedly (for example, IKΩ.

2Kg, 5Ω), and the exponent part of the magnification display value is increased every 3 steps using another switch. This is A
This is to ensure the accuracy of /D conversion.

Therefore, the deflection coil current detection resistance changeover switch 17
X, 17Y are operated in conjunction with the magnification display board number changeover switch 178 and the magnification display exponent changeover switch 178', and the variable resistor 18 for continuously variable deflection coil current is operated in conjunction with
A correct magnification value can be obtained by operating X, 18Y in conjunction with the variable resistor 188 for continuously variable magnification display and A/D converting vo with an appropriate conversion coefficient. The magnification value calculated here is displayed on the display 11, or as required, displayed on a CRT character display, or sent to the CRT 14 via the circuit 16.
displayed above. .

However, the size of the final photo is similar to that of a CRT.
If the size of the image plane is not equal to the size of the image plane No. 14, the above-mentioned problem arises in that the photographing magnification and the display magnification become different.

The present invention solves the above drawbacks of the prior art, corrects the display magnification according to the photographing magnification when the size of the final photograph is not the same size as the image plane of the CRT, and always keeps the image magnification and display magnification of the final photograph constant. The purpose is to provide an SEM magnification display device that can be matched.

The feature is that a display magnification correction circuit having a correction coefficient switching switch is connected between the photographing magnification switch and the magnification display circuit.

FIG. 3 is a magnification calculation circuit diagram according to an embodiment of the present invention, and the same parts as in FIG. 2 are given the same reference numerals. In this case, the display magnification correction circuit 2 enclosed by the broken line in the circuit of FIG.
0 is added. If the resistance value of the correction coefficient changeover switch 19 is Rrh%, and the feedback loop resistance is Ro, then 1 magnification display board number output voltage ■. ′ can be expressed by the following equation.

Vo'= (R, / Rt *) ・Vo
(3) Therefore, by appropriately selecting the values of Rlh and Re, the magnification display can be corrected to match the shooting conditions, and the magnification of the obtained data can be set to an accurate value regardless of the type of film. .

In general, when shooting with 4 inch x 5 inch size film, it is often taken at the same magnification, and in this case the correction coefficient is 0.8 for 95s + m x 72 inch size Polaroid film, and 0 for prony version negative film. .6
．． In case of further enlargement, 2, 3, 4.5・
You just need to set a value such as... For that, Rh ”0
．． 6, 0.8, 1, 2, 3°4.5... multiplied by Ro. Furthermore, if the operating knob of the correction coefficient changeover switch 19 is marked with the abbreviation of the applicable film, it will be extremely convenient to change the correction coefficient.

The magnification display device of this embodiment connects a display magnification correction circuit between the 1 magnification switch and the A/D converter and selects the resistance value, thereby adjusting the final photographic magnification and display magnification. Since it is possible to match the values, this method is extremely convenient, especially when printing magnification values on a photograph at the same time.

In the above embodiment, the image magnification M is defined by D/d, but the actual image magnification depends on the acceleration voltage, the distance between the final focusing lens and the sample (wire 73ff, ,.Ella.

These elements are usually incorporated into the circuit, but since they have been widely used in the past, they will be omitted here.

The SEM magnification display device of the present invention has the effect that the image magnification of the final photograph can be matched with the display magnification by adding a relatively simple display magnification correction circuit.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a conventional SEM, Figure 2 is a circuit diagram showing an example of the magnification calculation circuit surrounded by the broken line in Figure 1, and Figure 3
The figure is a magnification calculation circuit diagram that is an embodiment of the present invention. 3... Deflection coil, 5... Sample, 6X, 6Y...
Deflection current control circuit, 7X, '7Y...Deflection waveform generation circuit, 8X, 8Y...CRT deflection circuit, 9...Magnification switch, 10...Magnification display circuit, 11...Display device, 1
2...Detector, 13...Amplifier, 14...CRT
, 15... Secondary electron, 16. CRT character display circuit, 1
7X, 17Y...Deflection coil current detection resistance changeover switch, 178...Magnification display mantissa part changeover switch, 178
'...Magnification display exponent selection switch, 18X, 18Y
... Variable resistor for continuously variable deflection coil current, 18S.
... Variable resistor for continuously variable magnification display, 19... Correction coefficient changeover switch, 20... Display magnification correction circuit, ■.・
...Axis side coil current, Rfa HRltm...Deflection coil current detection 1st port 2n

Claims (1)

[Claims] 1. A deflection current control circuit that supplies current to a deflection coil installed in the path of the electron beam; a cathode ray tube that detects secondary electrons generated from the sample scanned with the electron beam and supplies them as a brightness modulation signal; In a scanning electron microscope, the scanning electron microscope has a cathode ray tube deflection circuit that sweeps the deflection coil of the cathode ray tube in synchronization with the output signal of the writing deflection current control circuit, and a magnification display circuit that displays the imaging magnification of the sample on the cathode ray tube. A magnification display device for a scanning electron microscope, characterized in that a display magnification correction circuit having a correction coefficient changeover switch is connected between a magnification switch and the magnification display circuit.