JP2006105861A - X-ray inspection apparatus and tube voltage/tube current regulation method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray inspection apparatus which can easily set the tube voltage and the tube current, even with respect to an unknown specimen. <P>SOLUTION: The X-ray inspection apparatus comprises an X-ray tube, an X-ray control section for controlling the tube voltage and current of the X-ray tube, and an X-ray detector for detecting X rays through the specimen. The X-ray inspection apparatus creates a transmission image from the transmission data of the specimen obtained by the X-ray detector. The X-ray inspection apparatus comprises a tube voltage/tube current setting section for setting the tube voltage and current of the X-ray tube; and a gradation holding means for holding the gradation of the transmission image, displayed at a display section in animation in real time, constant substantially in real time for display, when the setting of the tube voltage or the tube current is changed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an X-ray inspection apparatus that creates a transmission image, a cross-sectional image, or a three-dimensional image of a subject using X-rays.

  Conventionally, X-ray fluoroscopic inspection apparatuses for inspecting the inside of industrial products such as electronic parts and aluminum castings are provided on the market.

  In such an X-ray inspection apparatus, the operator can manually change the tube voltage V and tube current I of the X-ray tube. For this reason, the operator performs the setting according to the subject while observing the transmission image, and obtains the optimum image.

  Specifically, when the tube voltage V is increased, the energy E of each X-ray photon increases and the number N of photons increases. When the tube current is increased, the energy E of each X-ray photon does not change, and the photon number N increases.

  In the X-ray inspection apparatus, the X-ray detector detects X-rays with two-dimensional resolution, but the output of each detection element is proportional to the total amount of X-ray energy (E × N) received by each element. Therefore, the transmission image is generated by assigning light and dark according to the output of each detection element.

  The transmission ability of X-rays increases as the energy E of each X-ray photon increases. Therefore, when manually changing the tube voltage V and the tube current I, first, the energy E of each X-ray photon that is proportional to the tube voltage V that can be transmitted through the subject is determined. However, if the energy E proportional to the tube voltage V is too high, the contrast of the image is lowered and the best image cannot be obtained.

  Therefore, the tube voltage V is lowered, but since the image becomes dark at this time, the tube current I is increased to supplement the output. However, when the tube voltage V is lowered too much, the obtained image is too high in contrast and becomes an overexposed or undercut image.

  For this reason, conventionally, with respect to a known subject, the tube voltage V or the tube current I is adjusted using the previously used data of the tube voltage V or the tube current I.

On the other hand, there is a technique that can automatically set the tube voltage V and the tube current I, which are optimum X-ray conditions, for an unknown subject based on the transmission image (for example, Patent Documents 1 and 2). . In the techniques described in Patent Documents 1 and 2, an X-ray with an optimum tube voltage V or tube current I in which a range in which a subject is to be observed in a transmission image is in a brightness range suitable for visual observation. It is assumed that this is a condition, and this condition is automatically set.
JP 2002-14059 A JP 2003-173895 A

  However, as described above, when the tube voltage V or the tube current I is automatically set for the brightness adjustment, the sharing with the gradation adjustment of the image becomes arbitrary, and the optimum tube voltage V or tube current is obtained. There arises a problem that I cannot be determined. Specifically, for example, when the image is brightened, whether to increase the tube voltage V or lower the window level is arbitrarily selected and set.

  Here, since the brightness and contrast can be adjusted freely by adjusting the gradation of the image, it can be considered that the tube voltage V or the tube current I should not be used for the brightness adjustment. Therefore, it is considered that the tube voltage V or the tube current I should be set so as to give the maximum SN ratio (signal-to-noise ratio) for the structure of the observation portion.

  SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an X-ray inspection apparatus capable of setting a tube voltage V and a tube current I that give the maximum S / N ratio even to an unknown subject. To do.

  In order to solve the problem that the optimum tube voltage V and tube current I cannot be determined due to the occurrence of arbitraryness in the sharing with the gradation adjustment of the image, the inventor has earnestly studied to obtain the following knowledge.

  First, the tube voltage V and the tube current I, which are physically optimum X-ray conditions, are conditions that give the maximum S / N ratio (signal-to-noise ratio) to the structure of the observation portion. Further, the tube voltage V and the tube current I are irrelevant to the gradation adjustment that makes the transmission image easy to see. For this reason, the tube voltage V and the tube current I are mainly set so as to give the maximum S / N ratio to the structure of the observation portion, and the gradation conversion is performed so that the image determined in this way can be easily seen visually. It is subordinate to do.

  Secondly, the biggest problem in manually setting the physically optimum tube voltage V and tube current I is that the structure of the observation portion cannot be tracked. Specifically, when the tube voltage V and the tube current I are changed so that, for example, a void in the casting that is the structure of the observation portion is visible at the maximum SN ratio, the gradation changes due to the VI change. This makes it impossible to track the appearance of the void. Therefore, it is necessary to perform VI adjustment, and it is necessary to evaluate the S / N ratio by relying on the memory, which is time-consuming, cumbersome, and accuracy is lowered.

  In order to solve the above-mentioned problem, the invention according to claim 1 detects an X-ray tube, an X-ray controller for controlling a tube voltage and a tube current of the X-ray tube, and an X-ray transmitted through the subject. A tube voltage tube for setting a tube voltage and a tube current of an X-ray tube in an X-ray examination apparatus having an X-ray detector and creating a transmission image from transmission data of a subject obtained by the X-ray detector A current setting unit; and a gradation holding unit configured to display the gradation of a transmission image displayed in a moving image in real time on the display unit when the setting of the tube voltage or the tube current is changed, and to display substantially constant in real time. This is the gist.

  According to the first aspect of the present invention configured as described above, it is possible to easily set the tube voltage V and the tube current I by adjusting the transmission image so that the gradation is maintained in real time.

  According to a second aspect of the present invention, there is provided the X-ray inspection apparatus according to the first aspect, wherein the gradation holding means has a predetermined maximum brightness of the transmission image of the subject obtained by the X-ray detector. The gist is to perform gradation conversion so as to maintain the value of 1 and to maintain the substantially minimum brightness of the transmission image of the subject obtained by the X-ray detector at a predetermined second value.

  According to the second aspect of the present invention configured as described above, a transmission image in which gradation is maintained in real time can be transmitted to an unknown subject by adjusting the tube voltage V and the tube current I. It is possible to easily set the tube voltage V and the tube current I for the structure of the observation part based on the data.

  Further, the invention described in claim 3 is a transmission obtained by controlling the tube voltage and the tube current to generate X-rays from the X-ray tube and irradiating the subject, and detecting the X-rays transmitted through the subject. When a transmission image of the subject is created from the data and the tube voltage or tube current changes, the gradation is kept substantially constant in real time on the display unit. The gist is to adjust the tube voltage and tube current of the X-ray tube with the maximum S / N ratio with respect to the structure of the observed portion of the displayed transmission image.

  According to the third aspect of the present invention configured as described above, a transmission image in which gradation is maintained in real time can be transmitted to an unknown subject by adjusting the tube voltage V and the tube current I. It is possible to easily set the tube voltage V and the tube current I that give the maximum S / N ratio to the structure of the observation portion based on the data.

  According to a fourth aspect of the present invention, in the tube voltage tube current adjusting method according to the third aspect, when the gradation correction is performed, the substantially maximum brightness of the transmitted image of the created subject is predetermined. The X-ray tube voltage and tube current are adjusted while maintaining the value and gradation correction so that the substantially minimum brightness of the transmission image of the subject obtained by the X-ray detector is maintained at a predetermined second value. It is characterized by the following.

  According to the present invention of claim 4 configured as described above, a transmission image in which gradation is maintained in real time can be transmitted to an unknown subject by adjusting the tube voltage V and the tube current I. It is possible to easily set the tube voltage V and the tube current I that give the maximum S / N ratio to the structure of the observation portion based on the data.

  The invention described in claim 5 is an X-ray tube, an X-ray controller for controlling the tube voltage and tube current of the X-ray tube, and an X-ray detector for detecting X-rays transmitted through the subject. In the X-ray inspection apparatus for creating a transmission image from the transmission data of the subject obtained by the X-ray detector, the gradation of the transmission image when the tube voltage or tube current of the X-ray tube changes Gradation holding means for keeping the image constant, and the X-ray controller changes the tube voltage or the tube current. At this time, the image noise of the transmission image in which the gradation is maintained by the gradation holding means is calculated. The gist is to have automatic tube voltage tube current setting means for selecting and setting a tube voltage or tube current that minimizes image noise.

  According to the present invention of claim 5 configured as described above, by changing the tube voltage and the tube current while calculating the image noise of the transmission image in which the gradation is maintained, the tube voltage and the tube that minimize the image noise are obtained. The current can be selected and set, and the tube voltage and the tube current that give the maximum S / N ratio to the structure of the observation portion can be automatically set even for an unknown subject based on the transmission data. .

  As described above, according to the present invention, it is possible to provide an X-ray inspection apparatus that can easily set a tube voltage and a tube current even for an unknown subject.

  The present invention will be described below with reference to the drawings.

[First Embodiment]
As shown in FIG. 1, the X-ray inspection apparatus 1 according to the first embodiment includes an X-ray tube 11, an X-ray detector 12, a computer 13, a display unit 14, an X-ray control unit 15, and a high-pressure generation unit 16. have.

  The X-ray tube 11 generates an X-ray beam 22 that is used to transmit a subject 21 and obtain a transmission image.

  The X-ray detector 12 detects X-rays transmitted by the X-ray beam 22 generated from the X-ray tube 11 through the subject 21 with a two-dimensional resolution. The X-ray detector 12 is, for example, an X-ray I.D. I. (Image Intensifier) and a television camera, and the detected X-ray image is transmitted to the connected computer 13 as a 12-bit digital signal.

  The computer 13 is a normal computer and includes a CPU, a memory, a disk, a keyboard, a mouse, various interfaces, and the like. In addition, as shown in FIG. 1, the computer 13 realizes the X-ray inspection apparatus 1 according to the first embodiment of the present invention, as an image ROI (region of interest) setting unit 13a, It has a gradation holding unit 13b and a VI (tube voltage tube current) setting unit 13c.

  The ROI setting unit 13a sets an area designated by the operator using an input means such as a mouse as an ROI in the transparent image.

  The gradation holding unit 13b converts a 12-bit transmission image obtained by detection by the X-ray detector 12 into an 8-bit transmission image. Further, the gradation holding unit 13b sends the converted 8-bit transmission image to the display unit 14. Although the detected transmission image is 12 bits and the converted transmission image is 8 bits, the present invention is not necessarily limited to this.

  The VI setting unit 13c sets the tube voltage V and the tube current I based on an input from an input device such as a mouse from the operator. Further, the VI setting unit 13 c transmits the tube voltage V and the tube current I to the X-ray control unit 15.

  The display unit 14 displays the transmission image converted by the gradation holding unit 13b as a display image.

  The X-ray control unit 15 controls the high voltage generation unit 16 so that the tube voltage V and the tube current I in the X-ray tube 11 become set values based on the input from the VI setting unit 13c.

  The high voltage generator 16 generates a high voltage for generating X-rays based on the control of the X-ray controller 15.

  FIG. 1 is a schematic diagram of the X-ray inspection apparatus 1. Therefore, a table on which the subject is placed, a mechanism unit that moves the table to change the field of view and the magnification of the image, a shielding box that prevents X-ray leakage, and the like are omitted.

  The optimum setting of the tube voltage V and the tube current I will be described below. When starting the observation, the operator sets the subject 21 and turns on the X-ray switch. When the X-ray switch is turned on, X-rays are generated from the X-ray tube, and the computer 13 displays the transmission image of the subject 21 on the display unit 14 in real time as a moving image. At this time, since the tube voltage V and the tube current I are not optimal, the obtained image is not easy to see.

  The operator adjusts a mechanism (not shown) so that the observation site of the subject 21 enters the visual field, and sets the ROI (region of interest) so as to include, for example, the void 21a in the sample as the observation site. These operations are performed using input means such as a mouse. When the operator inputs, for example, a square figure, the ROI setting unit 13a stores this input and displays the ROI so as to overlap the displayed transparent image. The gradation holding unit 13b displays the moving image by gradation conversion so that the gradation in the ROI is always unchanged even when the tube voltage V and the tube current I change.

  Next, the gradation conversion process will be specifically described with reference to the drawings. FIG. 2 is a flowchart for explaining gradation holding processing in the gradation holding unit 13b.

  First, the gradation holding unit 13b acquires a transmission image for one frame, which is an X-ray image detected by the X-ray detector 12 (S01).

  Next, the gradation holding unit 13b applies a low-pass filter to the image in the ROI (S02). An example of this low-pass filter is a process of averaging density values of four adjacent pixels.

  Subsequently, the gradation holding unit 13b obtains the maximum value Bmax and the minimum value Bmin of the pixel value for the image in the ROI subjected to the low pass filter (S03).

  Next, the gradation holding unit 13b performs gradation conversion from the pixel value B to the pixel value B 'for the transmission image before being subjected to the low-pass filter obtained in step S01 (S04). For example, as shown in FIG. 3, the maximum value Bmax is set to the pixel value 180, the minimum value Bmin is set to the pixel value 80, and the 12-bit pixel value B is converted to the 8-bit pixel value B ′. Here, for example, the following formula (1) is used as the conversion formula.

B ′ = (B−Bmin) / (Bmax−Bmin) · (180−80) +80 (1)
Here, the conversion is performed for the entire screen, but may be performed only within the ROI.

  Thereafter, the 8-bit transmitted image subjected to gradation conversion is sent as a display image to the display unit 14 to update the display image (S05).

  Subsequently, the gradation holding unit 13b determines whether or not an end command has been issued (S06). Here, when a termination command is given, the gradation conversion process is terminated. On the other hand, if there is no termination command, the process returns to step S01, and the same processing of steps S01 to S05 is repeated for the next transmission image.

  In parallel with the state of the moving image where the image continues to be updated, the VI setting unit 13c, when the tube voltage V and the tube current I are input to the operator using input means such as a mouse or a keyboard, the tube voltage V The value of the tube current I is sent to the X-ray control unit 15. The X-ray control unit 15 controls the tube voltage V and tube current I of the X-ray tube 11 to be set values via the high voltage generation unit 16. Here, when VI is changed, the displayed image is held so that the gradation is between 80 and 180.

  Generally, when an image is updated at 30 frames per second, it can be observed as a moving image. However, if a slight flicker is allowed, the image can be updated at about 15 frames per second to be a moving image.

  The operator adjusts the tube voltage V and the tube current I so as to obtain the best image while viewing the transmission image of the display unit 14 that is a moving image. Specifically, the tube voltage V and the tube current I are set so that the SN ratio of the observation site such as the void 21a is maximized.

  FIG. 4 is a schematic diagram for explaining changes in the SN ratio when the tube voltage V and the tube current I are changed at the upper limit of the tube current. Here, the X-ray control unit 15 sets an upper limit of the tube current I for each tube voltage V in order to protect the X-ray tube 11 as usual. Here, it is assumed that the tube voltage V and the tube current I are changed along the predetermined upper limit line of the tube current I. The upper limit of the tube current I is usually limited by isowatts. The isowatt limit is to limit the value of V × I to a certain value. Note that the method of changing VI is not limited to this.

  4A and 4B show changes in the profile of the void 21a with the tube voltage V as the horizontal axis when the tube voltage V is excessive, (b) when it is optimal, and (c) when it is excessive. ing. Even when the tube voltage V and the tube current I are changed, gradation is maintained in real time. Specifically, since the pixel value becomes the pixel value 80 to the pixel value 180 that is a brightness range suitable for visual observation, the optimum tube voltage V and tube current I that easily maximize the SN ratio while viewing the image are determined. Can be set.

  Here, most of the noise appearing in the profile is noise caused by fluctuations in X-ray photons. If the tube voltage V is too small, the transmittance is lowered, and the S / N ratio is lowered by reducing the number of X-ray photons. On the other hand, if the tube voltage V is too large, the contrast is lowered, the signal S is reduced, and the SN ratio is lowered.

  Note that in step S02 of the gradation conversion process shown in FIG. 2, the low-pass filter is applied so that the maximum value Bmax and the minimum value Bmin are less affected by image noise and the flicker of the display image is reduced. Because.

  According to the X-ray inspection apparatus 1 according to the first embodiment described above, an unknown subject can be obtained by adjusting the tube voltage V and the tube current I while viewing a transmission image in which gradation is maintained in real time. On the other hand, the tube voltage V and the tube current I that give the maximum S / N ratio to the structure of the observation portion can be easily set based on the transmission data.

[Second Embodiment]
FIG. 5 is a schematic configuration diagram of the X-ray inspection apparatus 2 according to the second embodiment. The same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

  The X-ray inspection apparatus 2 includes an X-ray tube 11, an X-ray detector 12, a computer 13, a display unit 14, an X-ray control unit 15, and a high pressure generation unit 16. The X-ray inspection apparatus 2 is different from the X-ray inspection apparatus 1 in that it has a capture board 17. The computer 13 of the X-ray inspection apparatus 2 is different in that it has a gradation holding unit 13d instead of the gradation holding unit 13b.

  The capture board 17 converts an analog transmission image which is an X-ray image detected by the X-ray detector 12 into an 8-bit digital transmission image for each frame. The capture board 17 sends the converted digital signal to the gradation holding unit 13 d and the display unit 14. The capture board 17 changes the gradation of the transmission image by changing the offset value Of and the gain value g based on the input from the gradation holding unit 13d.

  The gradation holding unit 13 d is a software function block of the computer 13. The gradation holding unit 13d is different from the gradation holding unit 13b described above. Specifically, when an 8-bit transmission image is input, the gradation holding unit 13d controls the offset value Of and the gain value g of the capture board 17 so as to hold the gradation of the ROI unit.

  FIG. 6 is a flowchart for explaining the gradation holding process in the gradation holding unit 13d. First, the gradation holding unit 13d acquires a transmission image for one frame, which is an X-ray image detected by the X-ray detector 12 (S11). Next, the gradation holding unit 13d applies a low-pass filter to the image in the ROI (S12). Subsequently, the gradation holding unit 13d obtains the maximum value Bmax and the minimum value Bmin of the pixel value for the image in the ROI subjected to the low pass filter (S13). The processing so far is the same as in the first embodiment.

  Next, the gradation holding unit 13d obtains a corrected offset value Of 'and gain value g' from the current offset value Of and gain value g (S14). As a specific method of obtaining, there is a method shown in FIG. The horizontal axis is an analog pixel value P, and the vertical axis is an 8-bit pixel value B. The analog pixel value P is an input (volt value) to the capture board 17, and the 8-bit pixel value B is an output. Further, the offset value Of and the gain value g represent the characteristics of the capture board 17.

  The pixel value B and the pixel value P have the following relationship (2).

B = g · (P−Of) (2)
Here, the maximum value Bmax and the minimum value Bmin are known with respect to the current offset value Of and gain value g. Using this, the corrected offset value Of ′ and gain value g ′ are calculated so that the maximum value is 180 and the minimum value is 80. Although derivation is omitted, specifically, the offset value Of ′ and the gain value g ′ are obtained by calculating the following equations (3) to (6).

Pmax = Bmax / g + Of (3)
Pmin = Bmin / g + Of (4)
g ′ = (180−80) / (Pmax−Pmin) (5)
Of ′ = (180 · Pmin−80 · Pmax) / (180−80) (6)
Thereafter, the gradation holding unit 13d sends the obtained offset value Of ′ and gain value g ′ to the capture board 17 to update the offset value and gain value (S15).

  Subsequently, the gradation holding unit 13d determines whether or not there is an end command (S16), and ends when the end command is issued. On the other hand, if there is no termination command, the process returns to step S11, and the same processing is repeated for the next transmission image.

  In the next frame, the pixel value Bmax is adjusted to the pixel value 180, and the pixel value Bmin is adjusted to the pixel value 80. When the operator changes the tube voltage V and the tube current I, the level is delayed by one frame. Key is maintained. As long as the tube voltage V and the tube current I are not rapidly changed, the gradation is kept constant.

  According to the X-ray inspection apparatus 2 according to the second embodiment described above, an unknown subject can be obtained by adjusting the tube voltage V and the tube current I while viewing a transmission image in which gradation is maintained in real time. On the other hand, the tube voltage V and the tube current I that give the maximum S / N ratio to the structure of the observation portion can be easily set based on the transmission data.

[Modification]
The gradation conversion is not limited to the above-described embodiment. For example, the converted value of the maximum value Bmax is set to the pixel value 180, and the converted value of the minimum value Bmin is set to the pixel value 80. Good.

  Further, although the maximum value is Bmax and the minimum value is Bmin, it may be determined by another method. FIG. 8 shows an example of obtaining Bmax and Bmin by another method. The example shown in FIG. 8 is a histogram in the ROI, and shows the frequency of each pixel value with the horizontal axis as the pixel value B and the vertical axis as the number of pixels. In the histogram shown in FIG. 8, the position of 10% from the top in the area is Bmax, and the position of 10% from the bottom is Bmin. In the example shown in FIG. 8, an arbitrary value can be set instead of 10%. According to this method, Bmax and Bmin can be obtained stably without being affected by image noise, and the flicker of the display image can be further reduced.

  The gradation conversion is linear conversion in the embodiment, but may be non-linear conversion. In particular, logarithmic conversion is preferable because brightness is displayed in proportion to the thickness of the subject.

  Furthermore, the gradation conversion processing range is not limited to the full screen, but only the ROI, and the processing speed can be increased. The ROI can be set freely, and the entire screen can be set as the ROI.

  In the first and second embodiments, the VI is adjusted manually, but can be automatic. In this case, the computer 5 is provided with an automatic VI setting unit 13e instead of the VI setting unit 13c as a software function block.

  The automatic VI setting unit 13e inputs a transmission image (tone holding image) obtained by converting the tone from the tone holding unit 13b or 13d. The automatic VI setting unit 13 e transmits the voltage V and current I to the X-ray control unit 15.

  FIG. 9 is a flowchart for explaining the VI setting process in the automatic VI setting unit 13e.

  First, when X-rays are generated from the X-ray tube 11 (S21), the automatic VI setting unit 13e operates the X-ray control unit 15 to set the tube voltage V and the tube current I to predetermined initial values ( S22).

  When the tube voltage V and the tube current I are set to initial values in step S22, the automatic VI setting unit 13e acquires an N-frame gradation holding image from the gradation holding unit 13b or 13d (S23). The acquired gradation holding image is stored (S24).

  Here, the N frame image is, for example, an image of 10 frames, but is not limited to this, and is set to an arbitrary number. At this time, the N-frame transmission image is subjected to the same gradation conversion in the gradation holding unit 13b and is input to the automatic VI setting unit 13e. Specifically, tone conversion is performed by the process shown in steps S01 to S05 in the first frame, but the processes in steps S02 and S03 are omitted from the second frame, and the maximum values Bmax and Bmax obtained in the first frame are omitted. The minimum value Bmin is used. Similarly, in the gradation holding unit 13d, N frames are subjected to the same gradation conversion. Specifically, the offset value and gain value are set by the processing shown in steps S11 to S15 at the 0th frame, and the processing of S12 to S15 is omitted for the images of 1 to N frames, and sent to the automatic VI setting unit 13e as they are. .

  When the automatic VI setting unit 13e acquires N-frame gradation holding images (S25), noise is calculated from these images (S26).

  This noise is calculated by, for example, the following expressions (7) and (8).

Pixel ij noise
= √ {(B ′ (ij) −B ′ (ij) average between frames) ² Average between frames} (7)
Average within ROI of image noise = (noise of pixel ij) (8)
Here, B ′ (ij) is a pixel value at the pixel ij. In S23, the voltage V value and current I value and the obtained image noise are stored.

  When noise is calculated in step S26, it is confirmed whether or not the process is terminated (S27), the next voltage V and current I are set, and the process from step S23 is repeated (S28).

  As a method of setting the next voltage V and current I in step S28, for example, a method in which the voltage V is stepped up at regular intervals and the current I is changed to take an upper limit value for each voltage V can be considered. However, it is not limited to this.

  When it is confirmed in step S27 that the process is completed, the voltage V and current I with the smallest noise are selected, and the values of the voltage V and current I are set to the optimum voltage V value and current I value. (S29).

  In the example shown in FIG. 9, noise is calculated in order for all combinations of a predetermined voltage V and current I, and the voltage V and current I at which the noise is minimized are set as the optimum voltage V and current I. However, the method for obtaining the optimum voltage V and current I is not limited to such a method. For example, first, noise is calculated for several combinations of voltage V and current I at a rough step interval, and a region of voltage V value and current I value with low noise is selected. A method may be used in which noise is calculated by changing the voltage V value and the current I value to obtain the optimum voltage V and current I step by step. In addition, if a calculation method for obtaining changes in voltage V and current I using generally well-known calculated noise is used, the optimum voltage V and current I can be obtained in a shorter time. is there.

  In the example shown in FIG. 9, N frames of image storage are performed in steps S24 and S25, but N frames of image storage are not required. For example, as is generally well known, even if the configuration is such that one frame is overwritten one after another, image noise equivalent to equations (7) and (8) can be calculated by the one-pass method. It is.

  Furthermore, the ROI used in Expression (8) may be the same ROI used in the gradation holding process, or may be another newly set ROI.

  According to the above-described modification, the tone (N in FIG. 4) can be minimized while the signal (S in FIG. 4) is kept constant by maintaining the gradation, and the unknown object can be detected. On the other hand, the voltage V and the current I that give the maximum S / N ratio to the structure of the observation site can be automatically set based on the transmission data.

  The adjustment of the optimum tube voltage V and tube current I of the X-ray inspection apparatus according to the first and second embodiments can be applied to other apparatuses such as a tomography apparatus. When applied to a tomography apparatus, the tomography apparatus may use any method such as a circular orbit, an arc orbit, a linear orbit, and a multi-orbit. Moreover, a computer tomography apparatus (CT) may be used. In this case, the optimum VI adjustment may be performed for the X-ray path that is most difficult to transmit during scanning.

  It goes without saying that the present invention includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

1 is a schematic configuration diagram of an X-ray inspection apparatus according to a first embodiment of the present invention. It is a flowchart explaining the gradation holding | maintenance process which concerns on the 1st Embodiment of this invention. It is a figure explaining the gradation conversion which concerns on the 1st Embodiment of this invention. It is a schematic diagram of the SN ratio change when the tube voltage V and the tube current I are changed by isowatts. It is a schematic block diagram of the X-ray inspection apparatus which concerns on the 2nd Embodiment of this invention. It is a flowchart explaining the gradation holding | maintenance process which concerns on the 2nd Embodiment of this invention. It is a figure explaining how to obtain | require offset value Of 'and gain value g'. It is a figure explaining the gradation conversion which concerns on the modification of this invention. It is a flowchart of the automatic VI setting which concerns on the modification of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 ... X-ray inspection apparatus 11 ... X-ray tube 12 ... X-ray detector 13 ... Computer 13a ... ROI setting part 13b, 13d ... Gradation holding part 13c ... VI setting part 14 ... Display part 15 ... X-ray control part 16 ... High-pressure generator 17 ... Capture board 21 ... Subject 22 ... X-ray beam 21a ... Void

Claims (5)

An X-ray tube, an X-ray controller that controls the tube voltage and tube current of the X-ray tube, and an X-ray detector that detects X-rays transmitted through the subject. In an X-ray inspection apparatus that creates a transmission image from transmission data of the obtained subject,
A tube voltage tube current setting unit for setting a tube voltage and a tube current of the X-ray tube;
A gradation holding means for causing the gradation of a transmission image displayed in a moving image in real time to be displayed in real time on the display unit when the setting of the tube voltage or the tube current is changed;
An X-ray inspection apparatus characterized by comprising: The X-ray inspection apparatus according to claim 1,
The gradation holding means maintains the substantially maximum brightness of the transmission image of the subject obtained by the X-ray detector at a predetermined first value, and the transmission image of the subject obtained by the X-ray detector. An X-ray inspection apparatus characterized in that gradation conversion is performed so as to keep the substantially minimum brightness at a predetermined second value. Control the tube voltage and tube current, generate X-rays from the X-ray tube, irradiate the subject, and create a transmission image of the subject from transmission data obtained by detecting the X-rays transmitted through the subject When the tube voltage or tube current changes, the display unit displays a moving image of the gradation corrected with the gradation kept substantially constant in real time.
A tube voltage tube current adjusting method for an X-ray inspection apparatus, which adjusts the tube voltage and tube current of the X-ray tube that maximizes the SN ratio with respect to the structure of the observation part of the transmission image displayed on the display unit. In the tube voltage tube current adjustment method of the X-ray inspection apparatus according to claim 3,
When the gradation correction is performed, the substantially maximum brightness of the transmission image of the created subject is maintained at a predetermined first value, and the substantially minimum brightness of the transmission image of the subject obtained by the X-ray detector is set in advance. A tube voltage tube current adjusting method for an X-ray inspection apparatus, characterized in that the tube voltage and tube current of the X-ray tube are adjusted while correcting a gradation so as to maintain a predetermined second value. An X-ray tube, an X-ray controller that controls the tube voltage and tube current of the X-ray tube, and an X-ray detector that detects X-rays transmitted through the subject. In an X-ray inspection apparatus that creates a transmission image from transmission data of the obtained subject,
Gradation holding means for maintaining the gradation of the transmission image substantially constant when the tube voltage or tube current of the X-ray tube changes;
The X-ray controller changes the tube voltage or the tube current, calculates the image noise of the transmission image in which the gradation is maintained by the gradation holding means at this time, and the tube voltage or the tube current that minimizes the image noise Automatic tube voltage tube current setting means to select and set,
An X-ray inspection apparatus characterized by comprising:

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