Charged particle beam apparatus

1. A charged particle beam apparatus that irradiates a sample with charged particle beams, detects a charged particle signal generated from the sample, converts the charged particle signal into an electrical signal, and forms an image from the electrical signal, comprising:

a plurality of noise removal filters that remove noise of an electrical signal;

a measurement unit that measures a contrast-to-noise ratio after applying one of the noise removal filters; and

a determination unit that determines a magnitude relationship between the contrast-to-noise ratio measured by the measurement unit and a threshold value set in advance; wherein the determination unit determines whether to perform automatic brightness/contrast control according to the measured contrast-to-noise ratio.

2. The charged particle beam apparatus according to claim 1 , further comprising:

a filter change unit that changes the noise removal filter,

wherein the determination unit determines whether to perform automatic brightness/contrast control according to the measured contrast-to-noise ratio, and the filter change unit changes the noise removal filter when it is determined that the automatic brightness/contrast control is not performed.

3. The charged particle beam apparatus according to claim 2 ,

wherein the measurement unit measures a contrast-to-noise ratio again after changing the noise removal filter.

4. A charged particle beam apparatus that irradiates a sample with charged particle beams and detects a charged particle signal generated from the sample to form an image, comprising:

a plurality of image processing filters that remove noise of the image;

a histogram calculation unit that calculates an image histogram after applying one of the image processing filters; and

a determination unit that determines a magnitude relationship between a width of the histogram and a threshold value set in advance; wherein the determination unit determines whether to perform automatic brightness/contrast control according to the determination result.

5. The charged particle beam apparatus according to claim 4 , further comprising:

a filter change unit that changes the image processing filter,

wherein the determination unit determines whether to perform automatic brightness/contrast control according to the determination result, and the filter change unit changes the image processing filter when it is determined that the automatic brightness/contrast control is not performed.

6. The charged particle beam apparatus according to claim 5 ,

wherein the histogram calculation unit calculates an image histogram again after changing the image processing filter.

7. A charged particle beam apparatus that irradiates a sample with charged particle beams and detects a charged particle signal generated from the sample to form an image, comprising:

an image integration unit that acquires a plurality of frame images for the same field of view of the image and integrates the frame images;

a histogram calculation unit that calculates an image histogram after integrating a plurality of frames; and

a determination unit that determines a magnitude relationship between a width of the histogram and a threshold value set in advance; wherein the determination unit determines whether to perform automatic brightness/contrast control according to the calculated histogram.

8. The charged particle beam apparatus according to claim 7 ,

wherein the determination unit determines whether to perform automatic brightness/contrast control according to the calculated histogram, and the image integration unit changes the number of integrated frames when it is determined that the automatic brightness/contrast control is not performed.

9. The charged particle beam apparatus according to claim 8 ,

wherein the histogram calculation unit calculates an image histogram again after changing the number of integrated frames.