JPH0379816B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides light from a sample irradiated with an electron beam,
The present invention relates to an electron beam scanning sample image display device that includes a signal generation system including a detector that detects so-called cathodoluminescence, a signal processing system, and a scanning signal system that scans signals on a video screen.

Among the detectors used in X-ray microanalyzers and scanning electron microscopes, there are some, such as infrared semiconductor detectors, in which the temperature drift signal exceeds the normal signal change amount. When using such a detector, it is difficult to form an image to clearly display a sample image using a conventional image display system. To solve this problem, in the past, for example, a lock-in amplifier was used to modulate the signal at a constant frequency and amplify it independently of the signal scanning system, and then perform synchronous detection. Since it was less than 1/10, it was difficult to observe the image.

In view of the above, the present invention makes it possible to easily obtain a wide frequency band including frequencies as low as the DC level, so that a sample image can be clearly displayed on a video screen even when a detector with a large drift is used. The purpose is to make it easier to observe images.

In the present invention, the signal generation system is provided with a means for cutting off the electron beam or the light entering the detector in synchronization with the blanking signal in the scanning signal system, while the signal processing system is provided with a means for cutting off the electron beam or the light entering the detector in synchronization with the blanking signal in the scanning signal system, while the signal processing system is provided with a means for cutting off the electron beam or the light entering the detector in synchronization with the blanking signal in the scanning signal system. The present invention is characterized by providing means for clamping the DC level of the output signal.

EMBODIMENT OF THE INVENTION Hereinafter, the structure of this invention will be specifically explained about an Example based on drawing.

FIG. 1 is a configuration diagram of an embodiment of the present invention, and FIG.
The figure is a signal waveform diagram for explaining the operation. In the apparatus of the present invention, the signal generation system includes an electron beam generation circuit 1, electron beam deflection coils 2 and 3, and a sample 4.
and a detector 5 that has a lot of drift, such as an infrared semiconductor detector. When the sample 4 is irradiated with an electron beam from the electron beam generation circuit 1, light is generated from the sample 4, and this light is input to the detector 5. The detector 5 detects this light and outputs an output signal from the detector obtained by detecting the light to a signal processing system as a video signal. A detector 5 is located between the sample 4 and the detector 5.
Shutter 6 as a means of blocking light entering the
This shutter 6 is provided with a light shielding part 6.
a, 6a. This shutter 6 is connected to a synchronous motor 9 driven by a motor drive circuit 8 which operates in response to a blanking signal from an X-axis sweeper 7. The output of the detector 5 is connected via a preamplifier 10 to one input of a pulse clamp circuit 11 as a signal processing system. In addition, the scanning signal system includes an X-axis sweeper 7 and a Y-axis sweeper 1.
2, the X-axis sweeper 7 is connected to the other input of the motor drive circuit 8 and the pulse clamp circuit 11, while the Y-axis sweeper 12 is also connected to the other input of the pulse clamp circuit 11. It is connected to the. An output section of the pulse clamp circuit 11 is connected to a luminance signal input terminal of a video display 14 via a video amplifier 13. Note that 15 is a magnification adjuster, 16 and 17 are X-axis and Y-axis deflection coils, respectively, and 18 is an electron beam.

Next, the operation will be explained.

An electron beam 18 from the electron beam generation circuit 1 is scanned over a sample 4 by electron beam deflection coils 2 and 3. Light is generated from the sample 4 in response to the scanning of the electron beam 18, and this light is input to the detector 5. Then, the output section of the detector 5 outputs an output signal a having a waveform as shown in FIG. 2a. Figure 2a
In addition to this output signal a, there is a drift signal
a' is also shown, which indicates that the output signal a also contains a drift signal a' at the level shown. By the way, sample 4 and detector 5
A shutter 6 is provided between the shutter 6 and the shutter 6, and the light shielding portions 6a, 6a of the shutter 6 are positioned to block light from the sample 4 in synchronization with the blanking signal. Therefore, the level of the output signal a of the detector 5 varies between times _t1 and _t2 , and between times t3 and _t3 .
_t4 , that is, while the blanking signal is being output from the X-axis sweeper 7, it is at the level of the drift signal a'. By the way, the output signal a from the detector 5 whose waveform changes as shown in FIG. The pulse clamp circuit 11 clamps the input video signal a and converts it into a video signal b having a waveform as shown in FIG. 2b. The video signal b shown in Figure 2b is clamped to the DC level indicated by the drift signal contained therein, and as a result, the above-mentioned drift signal a' is removed from the video signal b. . The video signal b from which the drift signal has been removed is amplified by the video amplifier 13 and then input to the luminance signal input terminal of the video display 14. In the video display 14,
A video signal is generated in response to a deflection voltage applied to the deflection coils 16 and 17 by a scanning signal c having a waveform as shown in FIG. 2c from the axis sweeper 7 and a scanning signal (not shown) from the Y-axis sweeper 12. A sample image is displayed by a scanning signal system that scans the image on the video screen. In this embodiment, the sample image is displayed in this manner, but the scanning speed of the X-axis is generally about 10 milliseconds to 2 seconds per scanning line due to the necessity of observing the image on the video screen. However, the drift signal a' of the detector 5 has a time constant of several tens of seconds or more. Therefore, by reducing the optical signal to the detector 5 to zero by the shutter 6 every cycle of the X-axis scan, the necessary low frequency signal level can also be captured from the detector 5 into the signal. Further, the light shielding operation by the shutter 6 in this embodiment is performed during blanking during image scanning on the video display 14, so it does not affect image formation. Furthermore, in this embodiment, the drift of the preamplifier 10 system is also compensated for at the same time.

Note that a beam blanking coil may be provided between the electron beam generating circuit 1 and the sample 4 instead of the shutter 6 etc. in the above embodiment, and this beam blanking coil may be driven in synchronization with the X-axis scanning. good. Further, in the above embodiment, the synchronous motor 9 is driven by the X-axis scanning signal, but conversely, the motor drive system is made independent, and the signal from the motor drive system is sent to the X-axis sweeper 7 as a synchronous signal. You may give.

As explained above, according to the present invention, by blocking the electron beam or the light incident on the detector, only the drift signal is output from the detector, and the output signal from the detector at the time of blocking is By clamping the DC level, it is possible to remove drift signals contained in the output signal. As a result, signal removal for drift removal is performed during blanking, which does not affect image formation.Furthermore, even with a detector with large drift, the drift can be sufficiently removed to reduce the DC level. It is possible to obtain a signal over a wide frequency band, including a wide range of frequencies, and a clear sample image can be easily obtained on a video screen.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, and FIG. 2 is a signal waveform diagram for explaining its operation. DESCRIPTION OF SYMBOLS 1... Electron beam generation circuit, 4... Sample, 5... Detector, 6... Shutter, 6a... Light shielding part, 7...
X-axis sweeper, 8...Motor drive circuit, 9...Synchronous motor, 11...Pulse clamp circuit, 14...
Video display.

Claims (1)

[Claims] 1. A signal generation system having a detector that detects light generated from a sample upon irradiation with an electron beam;
An electronic device comprising a signal processing system that inputs an output signal from a detector obtained by detecting light as a video signal to a luminance signal input terminal of a video display, and a scanning signal system that scans the video signal on a video screen. In a line scanning sample image display device, the signal generation system is provided with means for blocking the electron beam or light incident on the detector in synchronization with the blanking signal in the scanning signal system, while the signal processing system is provided with a means for blocking the electron beam or light incident on the detector. What is claimed is: 1. An electron beam scanning sample image display device comprising means for clamping a DC level of an output signal from a detector at a certain time.