JP2009181863A - Image signal processing method and apparatus, and charged particle beam apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a contrast/brightness adjusting method for the purpose of measuring an amount of noise of a display image and keeping it constant from the measured amount of noise, and to provide its apparatus. <P>SOLUTION: The amount of noise is calculated from the display image, and the contrast and the brightness are adjusted on the basis of the measured amount of noise and a reference value on the amount of noise. When setting the reference value on the amount of noise, the contrast and the brightness can be adjusted, the display image can be obtained as correspondent to the reference value on the amount of noise, and the amount of noise can be set constant in the display image. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image signal processing method and apparatus capable of adjusting an image noise amount, and a charged particle beam apparatus.

  In recent years, charged particle beam apparatuses are actively used in many industrial fields such as semiconductor manufacturing. For example, when a scanning electron microscope (hereinafter referred to as SEM (Scanning Electron Microscope)) is used for industrial use, it is often used mainly in an inspection process for measuring pattern dimensions. In the SEM used for such applications, it is required to reduce the difference in measurement characteristics between a plurality of apparatuses. Therefore, when observing the same sample, it is desirable to align the image quality of the display image among a plurality of apparatuses.

  One of the adjustments necessary to align the image quality is the contrast adjustment of the display image. In the sample, there may be a portion with extremely high luminance or a portion with low luminance locally due to adhered dust or the like, and the contrast may not be an appropriate value.

  Therefore, for example, as disclosed in Patent Document 1, a contrast adjustment method that can cope with locally high or low luminance may be used. In this method, first, a plurality of combinations of a reference histogram for luminance and parameters for determining a gain and a DC level to be set are prepared in advance. The contrast is adjusted by comparing the histogram created from the display image of the sample with the reference histogram, selecting the reference histogram that is the closest to the form, and setting the parameters corresponding to the reference histogram.

JP-A-4-328234 (paragraphs 0003 to 0016) J. Immerkaer, “Fast Noise Variance Estimation” Proc. Of Computer Vision and Image Understanding, Vol.64, No.2, pp. 300-302, Sep. 1996. S.I.Olsen, “Noise Variance in Images,” In 8th. Scandinavian Conf. On Image Analysis, Norway, 1993.

  However, in the conventional technology such as Patent Document 1, since the display image of the charged particle beam apparatus including the SEM always includes noise, depending on the pattern or material to be inspected, the contrast and brightness can be adjusted from the luminance information. Even if it is implemented, the amount of noise in the display image increases and decreases, and the image quality may not be uniform, and there is a problem that appropriate sample observation cannot be performed.

  The present invention has been made in view of such a situation, and provides a contrast / brightness adjustment function capable of keeping the amount of noise of a display image constant.

  In order to solve the above problems, in the present invention, for example, a calculated noise amount is given so as to calculate a noise amount from a display image to be displayed on the display unit and to keep the calculated noise amount constant. The contrast and brightness of the display image are adjusted so as to match the noise amount reference value. More specifically, the calculated noise amount is adjusted to match the given noise amount reference value by changing the width and position of the histogram of the display image.

  In the present invention, the amount of noise is calculated from the display image to be displayed on the display unit, and an image control signal for adjusting the contrast and brightness of the display image so as to make the calculated noise amount constant is generated. . The signal amplifier controls the detection signal of the charged particle beam device by this image control signal. More specifically, the image control signal is generated by changing the signal amplification degree and the signal bias value of the display image from the calculated noise amount and noise amount reference value.

  Thus, in the present invention, if the noise amount reference value is set, the contrast and brightness are adjusted by contrast / brightness adjustment, and a display image that matches the noise amount reference value can be obtained. That is, the noise amount of the display image can be made constant, and the image quality of the display image can be made uniform.

  Further features of the present invention will become apparent from the best mode for carrying out the present invention and the accompanying drawings.

  ADVANTAGE OF THE INVENTION According to this invention, while measuring the noise amount of a display image, the image signal processing apparatus which can adjust the noise amount of a display image uniformly is provided. As a result, the image quality of the display image including noise can be made uniform.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be noted that this embodiment is merely an example for realizing the present invention, and does not limit the technical scope of the present invention. In each drawing, the same reference numerals are assigned to common components.

<First Embodiment>
FIG. 1 is a diagram showing a schematic configuration of an image signal processing apparatus according to a first embodiment of the present invention. The image signal processing apparatus 10 includes a noise amount calculation unit 12, a noise amount reference value setting unit 13, and a contrast / brightness adjustment unit 14 that adjusts a display image. The image signal processing apparatus 10 is assumed to be configured by a computer having a CPU (Central Processing Unit) and a memory, and in which signal processing is executed by digital processing. May be.

  The noise amount calculation unit 12 receives the display image 11, calculates the noise amount of the display image, and outputs a noise amount calculation value 15.

  The noise amount reference value setting unit 13 outputs a noise amount reference value 16 that is referred to when the contrast / brightness adjusting unit 14 adjusts the noise amount. This noise amount reference value 16 becomes a target value for adjusting the amount of noise included in the display image.

  The contrast / brightness adjustment unit 14 receives the noise amount calculation value 15 calculated by the noise amount calculation unit 12, the noise amount reference value 16 set by the noise amount reference value setting unit 13, and the display image 11 as inputs. Then, the display image 17 after adjustment in which the contrast and brightness of the display image are changed and the noise amount is adjusted is output.

  Next, the details of the noise amount calculation unit will be described using FIG. 2 showing the internal configuration of the noise amount expenditure unit 12. The noise amount calculation unit 12 includes a filter execution unit 21, a difference image generation unit 22, and a standard deviation calculation unit 23, and has a function of calculating a noise amount calculation value 15 from the display image 11.

  The filter execution unit 21 filters the display image 11 and generates an image from which noise has been removed. The filter to be used can be configured by a method such as a median filter or an average filter.

  The difference image generation unit 22 generates a difference image from the display image 11 before the noise is removed and the image after the noise is removed by the filter execution unit 21.

  The standard deviation calculation unit 23 calculates the standard deviation by squaring and accumulating each pixel of the difference image generated by the difference image generation unit 22, dividing by the number of pixels of the display image, and obtaining the square root. To do. This standard deviation becomes a noise amount calculation value of the display image, and it becomes possible to grasp the noise amount of the display image.

  Note that the noise amount calculation unit 12 can also apply the noise amount calculation method described in Non-Patent Documents 1 and 2. As an example, a case where the noise amount calculation method proposed by Immerkaer is applied to a noise amount calculation unit will be described with reference to FIG.

  In this case, as shown in FIG. 3, the noise amount calculation unit 12 can be configured by a filter execution unit 31 and a standard deviation calculation unit 32. The filter execution unit 31 generates an image obtained by applying a 3 × 3 filter to the display image 11. Further, the standard deviation calculation unit 32 obtains the square sum of each pixel from the generated image (filtered image), divides by the number of pixels of the display image, and obtains the square root of the obtained value, thereby obtaining the standard deviation of the noise amount. Is calculated. This standard deviation becomes a noise amount calculation value of the display image, and it becomes possible to grasp the noise amount of the display image.

  Next, a contrast / brightness adjustment method in the contrast / brightness adjustment unit 14 will be described. The contrast / brightness adjustment unit 14 calculates a noise amount calculation value 15 calculated by the noise amount calculation unit 12 and a noise amount reference value set by the noise amount reference value setting unit 13 for the input display image. Image processing is performed so that 16 matches, and contrast and brightness are adjusted.

  Here, image processing used to adjust contrast and brightness will be described with reference to FIG. First, a histogram is created for the gradation value of the brightness of each pixel from the display image (histogram 40 before adjustment). The horizontal axis is the gradation value, and the vertical axis is the number of pixels having the gradation value.

  First, in the contrast adjustment, the width of the histogram is changed. The gradation value of each pixel of the display image is multiplied by (noise amount reference value 16) / (noise amount calculation value 15) times, and the histogram width (maximum value to minimum value of brightness of the display image) ) To change the ratio of the white and black parts on the image and adjust the amount of noise. Also, in the brightness adjustment, the position of the histogram is changed. After adjusting the contrast, by changing the position of the histogram so that the average value of the histogram of the display image is at the center of the gradation value set on the horizontal axis (or a preset gradation value), Adjust the brightness level of the entire image.

  An example of the histogram obtained by these is the adjusted histogram 43. In this way, the contrast / brightness adjustment unit 14 adjusts the contrast and brightness of the display image by changing the width and position of the histogram, and brings the noise amount of the display image closer to the noise amount reference value.

  Next, the operation at the time of adjusting the noise amount of the display image in the image signal processing apparatus 10 will be described with reference to FIG. The noise amount reference value (RN) is set in advance by the noise amount reference value setting unit 13. First, a display image is acquired (step S50). Next, the noise amount calculation unit 12 calculates a noise amount calculation value (σN) (standard deviation) from the acquired display image (step S51).

  Next, the contrast / brightness adjusting unit 14 determines whether or not the difference between the noise amount reference value RN and the noise amount calculated value σN is equal to or less than δn which is a value very close to 0 (step S52). Here, δn is a value set in advance in accordance with the characteristics of the display image.

  If it is determined in step S52 that the difference between the noise amount reference value RN and the noise amount calculated value σN is not less than δn, the width and position of the histogram of the display image are changed, and the contrast and brightness are adjusted (step S53). ).

  On the other hand, after acquiring the display image and calculating the amount of noise from the acquired display image, if the difference between RN and σN is δn or less in the determination of RN−σN ≦ δn, the contrast and brightness are adjusted. do not do.

  FIG. 6 is a diagram illustrating an example in which the image signal adjustment device 10 is applied to a charged particle beam device. The charged particle beam device 60 includes a signal amplifier 70 that amplifies a detection signal output from the detector in a mirror body 61 that houses a beam source 64, a focusing lens 62, an objective lens 65, a detector 69, an XY stage 68, and the like. A display image generation unit 71 that generates an observation image signal 73 output from the signal amplifier as a display image, an image signal processing device 10, and an image display 72.

  In the mirror 61, when the charged particle beam 63 emitted from the beam source 64 is irradiated onto the sample 66, secondary electrons and reflected electrons are emitted from the sample portion irradiated with the charged particle beam 63, and the detector. 69 detects them. The detected signal is amplified by the signal amplifier 70 and output to the display image generation unit 71 as an observation image signal 73. At this time, the deflection of the charged particle beam 63 is controlled so as to scan the observation region of the sample 66. The sample 66 is fixed to a sample holder 67 installed on the XY stage 68, and the center position of the observation region of the sample 66 is determined by horizontal movement control of the XY stage 68.

The display image generation unit 71 receives the observation image signal 73 output from the signal amplifier 70 as an input, generates a bitmap display image 11, and stores it in an image memory constituted by a RAM (Random Access Memory) or the like.
In the display image 11 stored in the image memory, the amount of noise is adjusted to be constant by the image signal processing device 10.

  In the noise amount adjustment procedure in the image signal processing apparatus 10, first, the noise amount calculation unit 12 calculates the noise amount of the display image 11 generated by the display image generation unit 71. The contrast / brightness adjustment unit 14 checks whether the calculated noise amount of the display image 11 calculated by the noise amount calculation unit 12 matches the noise amount reference value set by the noise amount reference value setting unit 13. To do. If the calculated noise amount of the display image 11 does not match the noise amount reference value, the contrast / brightness adjustment unit 14 adjusts the contrast and brightness by changing the width and position of the histogram of the display image 11. Adjust the amount of noise in the displayed image. Then, the adjusted display image 17 is displayed on the image display 72.

<Second Embodiment>
FIG. 7 shows the configuration of an image signal processing apparatus according to the second embodiment of the present invention. The image signal processing device 80 includes a noise amount calculation unit 12, a noise amount reference value setting unit 13, and a contrast / brightness adjustment unit 81 whose adjustment target is a signal amplifier. It is assumed that the image signal processing device 80 is generally configured by a computer having a CPU (Central Processing Unit) and a memory, and executes signal processing therein by digital processing. You may comprise with a wire. Further, the configurations of the noise amount calculation unit 12 and the noise amount reference value setting unit 13 can be those of the first embodiment.

  The contrast / brightness adjustment unit 81 receives the noise amount calculation value 15 calculated by the noise amount calculation unit 12 and the noise amount reference value 16 set by the noise amount reference value setting unit 13 as inputs, and the next noise amount. A signal amplifier control signal 82 for outputting the calculated value close to the noise amount reference value is output. The control signal of this signal amplifier means the amplification degree and bias value of the signal amplifier used for adjusting the observation image signal.

  The configuration of the contrast / brightness adjustment unit will be described with reference to FIG. The contrast / brightness adjustment unit 81 includes an amplification degree determination unit 85 and a bias value determination unit 86.

  The amplification degree determination unit 85 receives the noise amount calculation value 15 and the noise amount reference value 16 as inputs, and outputs the amplification degree of the control signal 82 of the signal amplifier. The output amplification degree is determined in advance by measuring the relationship between the noise amount of the display image and the amplification degree of the signal amplifier and inputting the calculated noise amount value and the noise amount reference value.

  The bias value determination unit 86 receives the noise amount calculation value 15 and the noise amount reference value 16 as inputs, and outputs a bias value of the control signal 82 of the signal amplifier. The output bias value is determined in advance by measuring the relationship between the noise amount of the display image and the bias value of the signal amplifier and inputting the calculated noise amount and the noise amount reference value.

  Then, the control signal 82 (amplification degree / bias value) of the signal amplifier determined by the contrast / brightness adjusting unit 81 is output to the signal amplifier, and the signal amplifier uses the control signal of the signal amplifier to observe the image signal. To adjust the contrast and brightness of the displayed image.

  Next, a method for controlling the observation image signal used for adjusting the contrast and brightness will be described with reference to FIG.

  First, in contrast adjustment, the maximum value of the observation image signal is changed. By multiplying the observation image signal (FIG. 9A) by the amplification factor (gain) of the control signal of the signal amplifier (FIG. 9B) and changing the maximum value of the observation image signal, the white portion and the black portion on the image are changed. Adjust the ratio. In the brightness adjustment, the average value of the observation image signal is changed. The brightness value of the entire image is adjusted by adding the bias value of the control signal of the signal amplifier to the observation image signal (FIG. 9C) and changing the average value of the observation image signal. An example of the observation image signal obtained by these is the adjusted observation image signal (FIG. 9D).

  As described above, the contrast / brightness adjustment unit 81 determines the control signal 82 (amplification degree / bias value) of the signal amplifier from the input of the noise amount calculation value of the display image and the noise amount reference value, and outputs the control signal 82 to the signal amplifier. . Then, in the signal amplifier, processing of (amplification degree) × (observation image signal) + (bias value) is performed, and the observation image signal is controlled to adjust the contrast and brightness of the display image, and the noise amount of the display image To the noise amount reference value.

  Next, the operation at the time of adjusting the noise amount of the display image in the image signal processing device 80 will be described with reference to FIG. The noise amount reference value (RN) is set in advance by the noise amount reference value setting unit 13. First, a display image is acquired (step S60). Next, the noise amount calculation unit 12 calculates a noise amount calculation value (σN) (standard deviation) from the acquired display image (step S61). Next, the contrast / brightness adjustment unit 81 determines whether or not the difference between the noise amount reference value RN and the noise amount calculated value σN is equal to or less than δn, which is a value extremely close to 0 (step S62). Here, δn is a value set in advance in accordance with the characteristics of the display image.

  When the difference between the noise amount reference value RN and the noise amount calculated value σN is not equal to or less than δn in the determination in step S62, the amplification and bias values of the signal amplifier are changed and the measurement image signal is controlled to display the difference. The contrast and brightness of the image are adjusted (step S63).

  On the other hand, after acquiring the display image and calculating the amount of noise from the acquired display image, if the difference between RN and σN is δn or less in the determination of RN−σN ≦ δn, the contrast and brightness are adjusted. do not do.

  FIG. 11 is a diagram showing an example in which the image signal adjustment device 80 is applied to a charged particle beam device. The charged particle beam apparatus 100 includes a signal amplifier 70 that amplifies a detection signal output from the detector in a mirror body 61 that houses a beam source 64, a focusing lens 62, an objective lens 65, a detector 69, an XY stage 68, and the like. A display image generation unit 71 that generates an observation image signal 73 output from the signal amplifier as a display image, an image signal processing device 80 according to the present invention, and an image display 72.

  In the mirror 61, when the charged particle beam 63 emitted from the beam source 64 is irradiated onto the sample 66, secondary electrons and reflected electrons are emitted from the sample portion irradiated with the charged particle beam 63, and the detector. 69 detects them. The detected signal is amplified by the signal amplifier 70 and output to the display image generation unit 71 as an observation image signal 73. At this time, the deflection of the charged particle beam 63 is controlled so as to scan the observation region of the sample 66. The sample 66 is fixed to a sample holder 67 installed on the XY stage 68, and the center position of the observation region of the sample 66 is determined by horizontal movement control of the XY stage 68.

  The display image generation unit 71 receives the observation image signal 73 output from the signal amplifier 70 as an input, generates a bitmap display image 11, and stores it in an image memory constituted by a RAM (Random Access Memory) or the like.

  Using the display image 11 stored in the image memory as an input, the image signal processing device 80 determines the control signal 82 of the signal amplifier for bringing the calculated noise amount value of the display image closer to the set noise amount reference value.

  In the determination procedure of the control signal of the signal amplifier in the image signal processing device 80, first, the noise amount calculation unit 12 calculates the noise amount of the display image 11 generated by the display image generation unit 71. In the contrast / brightness adjustment unit 81, whether or not the noise amount calculation value of the display image 11 calculated by the noise amount calculation unit 12 matches the noise amount reference value set by the noise amount reference value setting unit 13. Check. When the calculated noise amount value of the display image and the noise amount reference value do not match, the contrast / brightness adjustment unit 81 causes the control signal of the signal amplifier so that the calculated noise amount value of the display image approaches the noise amount reference value. (Amplification degree / bias value) is determined and output to the signal amplifier 70.

  The signal amplifier 70 adjusts the observation image signal from the control signal of the signal amplifier. The adjusted observation image signal is generated again in the display image 11 of the bitmap by the display image generation unit 71, and the display image after the contrast / brightness adjustment is displayed on the image display 72.

<Third Embodiment>
FIG. 12 shows a charged particle 1000 device according to the third embodiment, in which both an image signal adjustment device 10 whose display image is to be adjusted and an image signal processing device 80 whose signal amplifier is to be adjusted are charged particles. It is a figure which shows the example applied to the wire device.

  The charged particle beam device 110 amplifies a detection signal output from the detector to a mirror body 61 that houses a beam source 64, a focusing lens 62, an objective lens 65, a detector 69, an XY stage 68, and the like. , A display image generation unit 71 that generates an observation image signal 73 output from the signal amplifier as a display image, an image signal processing device 10 and an image signal processing device 80 according to the present invention, and an image display 72 Are connected and configured.

  In the mirror 61, when the charged particle beam 63 emitted from the beam source 64 is irradiated onto the sample 66, secondary electrons and reflected electrons are emitted from the sample portion irradiated with the charged particle beam 63, and the detector. 69 detects them, the detected signal is amplified by a signal amplifier, and is output to the display image generation unit 71 as an observation image signal 73. At this time, the deflection of the charged particle beam 63 is controlled so as to scan the observation region of the sample 66. The sample 66 is fixed to a sample holder 67 installed on the XY stage 68, and the center position of the observation region of the sample 66 is determined by horizontal movement control of the XY stage 68.

  The display image generation unit 71 receives the observation image signal 73 output from the signal amplifier 70 as an input, generates a bitmap display image 11, and stores it in an image memory constituted by a RAM (Random Access Memory) or the like.

  When both the image signal adjustment device 10 for adjusting the display image and the image signal processing device 80 for adjusting the signal amplifier are applied to the charged particle beam device, the noise amount of the display image is adjusted in two stages. It becomes possible to do.

  First, the image signal processing device 80 whose adjustment target is a signal amplifier controls the observation image signal. Using the display image 11 stored in the image memory as an input, the image signal processing device 80 determines a control signal 82 of the signal amplifier for bringing the noise amount calculation value of the next display image close to the noise amount reference value.

  In the determination procedure of the control signal 82 of the signal amplifier in the image signal processing device 80, first, the noise amount calculation unit 12 calculates the noise amount of the display image 11 generated by the display image generation unit 71. In the contrast / brightness adjustment unit 81, whether or not the noise amount calculation value of the display image 11 calculated by the noise amount calculation unit 12 matches the noise amount reference value set by the noise amount reference value setting unit 13. Check. When the calculated noise amount value of the display image and the noise amount reference value do not match, the contrast / brightness adjustment unit 81 causes the control signal of the signal amplifier so that the calculated noise amount value of the display image approaches the noise amount reference value. (Amplification degree / bias value) is determined and output to the signal amplifier 70. The signal amplifier 70 adjusts the observation image signal from the control signal of the signal amplifier.

  The adjusted observation image signal 73 is again generated in the bitmap display image 11 by the display image generation unit 71 and stored in the image memory.

  Next, the image signal processing apparatus 10 whose display image is to be adjusted uses the display image 11 adjusted by the signal amplifier as an input to adjust the noise amount of the display image.

  In the noise amount adjustment procedure in the image signal processing apparatus 10, first, the noise amount calculation unit 12 calculates the noise amount of the display image 11 generated by the display image generation unit 71. The contrast / brightness adjustment unit 14 checks whether the calculated noise amount of the display image 11 calculated by the noise amount calculation unit 12 matches the noise amount reference value set by the noise amount reference value setting unit 13. To do. If the calculated noise amount of the display image 11 does not match the noise amount reference value, the contrast / brightness adjustment unit 14 adjusts the contrast and brightness by changing the width and position of the histogram of the display image 11. Adjust the amount of noise in the displayed image. Then, the adjusted display image 17 is displayed on the image display 72.

  As described above, in a charged particle beam apparatus having different detection sensitivity of the detector and amplification factor of the signal amplifier of the detection signal, even if the noise amount of the display image increases or decreases, the noise amount of the display image is controlled to be constant. It is possible to align the image quality.

  In all the above embodiments, an SNR (Signal-to-Noise Ratio) index may be used instead of the noise amount.

It is a figure which shows schematic structure of the image signal processing apparatus by the 1st Embodiment of this invention. It is a figure which shows schematic structure of a noise amount calculation part. It is a figure which shows schematic structure of a noise amount calculation part (Immerkaer application). It is a figure explaining the image processing for adjusting contrast and brightness. It is a flowchart for demonstrating the noise amount adjustment process to which the contrast and brightness adjustment part which makes display image an adjustment object is applied. It is a figure which shows schematic structure of the charged particle beam apparatus to which the image signal processing apparatus by 1st Embodiment is applied. It is a figure which shows schematic structure of the image signal processing apparatus by the 2nd Embodiment of this invention. It is a figure which shows the structure of the contrast brightness adjustment part (signal amplifier) of the image signal processing apparatus by 2nd Embodiment. It is a figure for demonstrating the control method of the observation image signal for adjusting contrast brightness. It is a flowchart for demonstrating the noise amount adjustment process to which contrast and brightness adjustment which makes signal amplifier adjustment object is applied. It is a figure which shows schematic structure of the charged particle beam apparatus to which the image signal processing apparatus by 2nd Embodiment is applied. It is a figure which shows schematic structure of the charged particle beam apparatus by 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Image signal processing apparatus (display image), 11 ... Display image, 12 ... Noise amount calculation part, 13 ... Noise amount reference value setting part, 14 ... Contrast brightness adjustment part ( Display image), 15 ... Noise amount calculation value, 16 ... Noise amount reference value, 17 ... Display image after adjustment, 21 ... Filter execution unit, 22 ... Difference image generation unit, 23 ... Standard deviation calculation section, 31 ... Filter implementation section, 32 ... Standard deviation calculation section, 40 ... Histogram before adjustment, 41 ... Histogram width adjustment (contrast), 42 ... Histogram position adjustment (brightness), 43 ... Histogram after adjustment, 60 ... Charged particle beam device (adjustment target: display image), 61 ... Mirror body, 62 ... Focusing lens, 63 ...・ Charged particle beam, 64 ... Bi Source, 65 ... objective lens, 66 ... sample, 67 ... sample holder, 68 ... XY stage, 69 ... detector, 70 ... signal amplifier, 71 ... display image Generation unit 72... Image display unit 73... Observation image signal 80... Image signal processing device (signal amplifier) 81 .. Contrast / brightness adjustment unit (signal amplifier) 82. Signal amplifier control signal (amplification / bias value), 85... Amplification determination unit, 86... Bias value determination unit, 90... Observation image signal before adjustment, 91. Maximum value adjustment by contrast (contrast), 92 ... Average value adjustment (brightness) by adding bias values, 93 ... Observation image signal after adjustment, 100 ... Charged particle beam device (target to be adjusted: signal amplifier) 110 ... charged particle beam device Adjustment target: display image + signal amplifier)

Claims (13)

An image signal processing method for adjusting a display image to be displayed on a display unit, comprising:
The noise calculation unit calculates the amount of noise from the display image,
An image signal processing method, wherein the image adjustment unit adjusts contrast and brightness of the display image so that the calculated noise amount is constant.   The image signal processing method according to claim 1, wherein the image adjustment unit adjusts contrast and brightness of the display image so that the calculated noise amount matches a given noise amount reference value. .   The image adjustment unit adjusts the calculated noise amount to match a given noise amount reference value by changing a width and position of a histogram of the display image. The image signal processing method as described. An image signal processing method for adjusting a display image to be displayed on a display unit, comprising:
The noise calculation unit calculates the amount of noise from the display image,
An image signal processing method, wherein the signal control unit generates an image control signal for adjusting contrast and brightness of the display image so that the calculated amount of noise is constant.   The signal control unit generates the image control signal by changing a signal amplification degree and a signal bias value of the display image from the calculated noise amount and the noise amount reference value. Item 5. The image signal processing method according to Item 4. An image signal processing device for adjusting a display image to be displayed on a display unit,
A noise calculation unit for calculating a noise amount from the display image;
An image adjusting unit for adjusting the contrast and brightness of the display image so as to make the calculated noise amount constant;
An image signal processing apparatus comprising:   The image signal processing apparatus according to claim 6, wherein the image adjustment unit adjusts contrast and brightness of the display image so that the calculated noise amount matches a given noise amount reference value. .   The image adjustment unit adjusts the calculated noise amount so as to match a given noise amount reference value by changing a width and a position of a histogram of the display image. The image signal processing apparatus described. An image signal processing device for adjusting a display image to be displayed on a display unit,
A noise calculation unit for calculating a noise amount from the display image;
A signal control unit that generates an image control signal for adjusting the contrast and brightness of the display image so as to make the calculated noise amount constant;
An image signal processing apparatus comprising:   The signal control unit generates the image control signal by changing a signal amplification degree and a signal bias value of the display image from the calculated noise amount and the noise amount reference value. Item 10. The image signal processing device according to Item 9. A charged particle beam apparatus for irradiating a surface of a sample with a charged particle beam and observing the sample,
A detector for detecting a signal emitted from the sample surface by irradiation of the charged particle beam;
An image generation unit for generating a display image to be displayed on the display unit from a detection signal by the detector;
An image signal processing device according to any one of claims 6 to 8,
A display unit for displaying an image whose contrast and brightness are adjusted by the image signal processing device;
A charged particle beam apparatus comprising: A charged particle beam apparatus for irradiating a surface of a sample with a charged particle beam and observing the sample,
A detector for detecting a signal emitted from the sample surface by irradiation of the charged particle beam;
A signal amplifier for controlling a detection signal by the detector;
An image generation unit that generates a display image to be displayed on the display unit from the detection signal controlled by the signal amplifier;
The image signal processing device according to claim 9 or 10,
A display unit for displaying the display image,
The charged particle beam device, wherein the signal amplifier adjusts an amplification degree and / or a bias value of the detection signal based on an image control signal generated by the image signal processing device. A charged particle beam apparatus for irradiating a surface of a sample with a charged particle beam and observing the sample,
A detector for detecting a signal emitted from the sample surface by irradiation of the charged particle beam;
A signal amplifier for controlling a detection signal by the detector;
An image generation unit that generates a display image to be displayed on the display unit from the detection signal controlled by the signal amplifier;
The image signal processing device (first image signal processing device) according to claim 9 or 10,
The image signal processing device (second image signal processing device) according to any one of claims 6 to 8,
A display unit for displaying the display image,
The signal amplifier adjusts an amplification degree and / or a bias value of the detection signal based on an image control signal generated by the first image signal processing device;
The image generation unit generates a first adjusted display image from the detection signal in which the amplification degree and / or bias value is adjusted,
The second image signal processing device generates a second adjusted display image by adjusting contrast and brightness of the first adjusted display image;
The charged particle beam apparatus, wherein the display unit displays the second adjusted display image.

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