X-ray apparatus and tube current calculation device

Abstract

To accurately detect a tube current flowing in an X-ray tube even when a tube voltage rises.SOLUTION: A tube voltage detected by a tube voltage detection part of an X-ray apparatus is received and differentiated, and the differentiation result is multiplied by a predetermined first constant to obtain a first value which is a current component flowing into a capacitance between the X-ray apparatus and an X-ray tube. In addition, the tube voltage is divided by a predetermined second constant to obtain a second value which is a current component flowing through the resistor of the X-ray apparatus. The tube current flowing through the X-ray tube of the X-ray apparatus is obtained by subtracting the first value and the second value from the current detected by the current detection unit of the X-ray apparatus.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an X-ray device that supplies a tube current and a tube voltage to an X-ray tube to irradiate X-rays. [Background technology]

[0002] An X-ray high-voltage device is a device that uses a high-voltage generator to boost and rectify AC power to form a desired high-voltage tube voltage and a desired tube current value, and supplies them to an X-ray tube. To obtain a desired X-ray dose, the X-ray high-voltage device detects the tube voltage and tube current supplied to the X-ray tube and performs feedback control of the voltage and current values, as described in Patent Document 1, for example. A tube current detection circuit detects the current flowing from the high-voltage rectifier circuit of the high-voltage generator to the earth. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-289579 Summary of the Invention [Problem to be solved by the invention]

[0004] A smoothing capacitor is placed between the high-voltage rectifier circuit and the X-ray tube, and the two are connected by a high-voltage shielded cable. The high-voltage shielded cable has an insulating structure that can insulate against a tube voltage of approximately 150,000 volts, so it has a non-negligible stray capacitance. The current supplied to the X-ray tube from the high-voltage rectifier circuit, detected by the tube current detection circuit, includes not only the tube current flowing through the X-ray tube, but also the current flowing into the stray capacitance of the smoothing capacitor and the high-voltage shielded cable. The current flowing into the stray capacitance of the smoothing capacitor and the high-voltage shielded cable is generated when electric charge is charged into the stray capacitance of the smoothing capacitor and the high-voltage shielded cable during the rise of the tube voltage. Furthermore, when the tube voltage falls, electric charge is released from the stray capacitance of the smoothing capacitor and the high-voltage shielded cable, causing a current to flow in the opposite direction to that during the rise of the tube voltage. Both of these are difficult to measure accurately.

[0005] As described above, the value of the current flowing through the high-voltage rectifier circuit detected by the tube current detection circuit is not an accurate tube current value, and there is a large error, particularly when the tube voltage rises and falls.

[0006] If an accurate tube current value cannot be obtained, accurate feedback control of the tube current is not possible. For this reason, feedback control is sometimes not performed when the tube voltage rises, and instead the tube is controlled to operate according to a preset value.

[0007] In particular, when irradiating pulsed X-rays, such as in fluoroscopic imaging with an X-ray fluoroscopy device, the tube voltage rises and then falls in a short time with narrow pulse width X-rays, making it difficult to accurately detect the tube current throughout the pulse. As a result, the desired image density may not be obtained.

[0008] On the other hand, if it were possible to directly measure the current flowing through the high-voltage shielded cable near the input terminal of the X-ray tube, it would be possible to actually measure the current flowing through the X-ray tube. However, because the tube voltage supplied to the X-ray tube is high, at over 100,000 V, it is necessary to measure it using a high-voltage isolated circuit, which results in a large and expensive measuring device.

[0009] The present invention aims to accurately detect the tube current flowing through an X-ray tube even when the tube voltage rises. [Means for solving the problem]

[0010] To achieve the above object, the X-ray device of the present invention includes a high-voltage generator that boosts and rectifies input AC power to a DC high voltage of a predetermined voltage value, and an X-ray tube that generates X-rays by receiving a DC high voltage of a predetermined voltage value and a DC current supplied from the high-voltage generator. The high-voltage generator includes a high-voltage transformer that boosts the input AC power, a rectifier circuit that rectifies the AC voltage boosted by the high-voltage transformer to a DC voltage, a smoothing capacitor that smooths the DC voltage rectified by the rectifier circuit, a tube voltage detector that detects the tube voltage across both ends of the X-ray tube, and a tube current detector. The high-voltage transformer, rectifier circuit, and smoothing capacitor are all connected in parallel to the X-ray tube. The rectifier circuit includes a first rectifier circuit and a second rectifier circuit connected in series, with the first rectifier circuit and the second rectifier circuit being grounded. The current detector includes a current detector that detects the current flowing between the first rectifier circuit or the second rectifier circuit and ground, and a calculation unit. The calculation unit differentiates the tube voltage detected by the tube voltage detection unit, and calculates the tube current flowing through the X-ray tube by subtracting the value obtained by multiplying the tube voltage by a predetermined first constant and the value obtained by dividing the tube voltage by a predetermined second constant from the current detected by the current detection unit. [Effects of the Invention]

[0011] According to the present invention, the tube current flowing through the X-ray tube can be detected with high accuracy even when the tube voltage is rising. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a circuit diagram showing the configuration of an X-ray apparatus according to a first embodiment of the present invention. [Figure 2] 6(a) to 6(g) are graphs showing the current or voltage waveforms at each part of the circuit of the X-ray device 100 and the calculated current waveforms. [Figure 3] FIG. 4 is a block diagram showing another example of the calculation unit 82 of the X-ray apparatus according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] An X-ray apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

[0014] FIG. 1 is a diagram showing the circuit configuration of an X-ray device 100 according to an embodiment, and FIGS. 2(a) to 2(g) are graphs showing the current or voltage waveforms at each part of the circuit of the X-ray device 100 and the calculated current waveforms.

[0015] In the X-ray device 100 of this embodiment, the calculation unit 82 of the X-ray high voltage device 101 calculates the value of the current component flowing into the smoothing capacitor 40 and other components other than the X-ray tube 60 based on the detected value of the tube voltage, and calculates an accurate tube current value by subtracting this value from the current value detected by the current detection unit 81. That is, in this embodiment, the value of the tube voltage accurately detected by the tube voltage detection unit connected in parallel to the X-ray tube 60 is used to calculate the current component flowing into the capacitor and other components other than the X-ray tube, and the tube current at the time of tube voltage rise is also accurately determined from the value of the current detection unit.

[0016] The X-ray device 100 according to the embodiment will be specifically described below.

[0017] As shown in FIG. 1, the X-ray device 100 is configured to include an X-ray high voltage device 101, an X-ray tube 60, and a high-voltage shielded cable 50. The X-ray high voltage device 101 includes a high-voltage generator 1 and an X-ray control device (not shown) that controls the high-voltage generator 1. The high-voltage generator 1 boosts and rectifies AC power input from terminal 1a to a DC high voltage of a predetermined voltage value. The X-ray tube 60 is connected to the high-voltage generator 1 by a high-voltage shielded cable 50 that is surrounded by a conductive shielding layer. The X-ray tube 60 generates X-rays when supplied with a DC high voltage of a predetermined voltage value and a DC current from the high-voltage generator 1.

[0018] The high-voltage generator 1 comprises a high-voltage transformer 10 that boosts the input AC power, a rectifier circuit 20 that rectifies the AC voltage boosted by the high-voltage transformer 10 to convert it into a DC voltage, a smoothing capacitor 40 that smooths the DC voltage rectified by the rectifier circuit 20, a tube current detector 80, and a tube voltage detector 30. The high-voltage transformer 10, the rectifier circuit 20, and the smoothing capacitor 40 are all connected in parallel to the X-ray tube.

[0019] The high-voltage transformer 10 includes a primary winding 15 connected to a terminal 1a to which power is input, and secondary windings 11 and 12. The secondary windings 11 and 12 are divided into a first secondary winding 11 and a second secondary winding 12.

[0020] The rectifier circuit 20 has a configuration in which a first rectifier circuit 21 and a second rectifier circuit 21 are connected in series and connected in parallel to the X-ray tube 60. Both the first rectifier circuit 21 and the second rectifier circuit 21 are bridge circuits in which four diodes are connected. The first rectifier circuit 21 is connected to the first secondary winding 11 and rectifies the output voltage thereof. The second rectifier circuit 22 is connected to the second secondary winding 12 and rectifies the output voltage thereof. The wiring 23 connecting the first rectifier circuit 21 and the second rectifier circuit 22 is grounded.

[0021] Smoothing capacitor 40 is configured by connecting an even number of capacitors 41, 42, etc. in series in a circuit, which is connected in parallel to X-ray tube 60. The total capacitance of the multiple capacitors is Cs. The wiring connecting the multiple capacitors is grounded at the midpoint between the multiple capacitors.

[0022] The tube voltage detection unit 30 is disposed between the rectifier circuit 20 and the smoothing capacitor 40. The tube voltage detection unit 30 includes a resistance circuit in which a circuit in which a plurality of resistors 31, 32, 33, 34, etc. are connected in series is connected in parallel to the X-ray tube 60, resistor capacitors 35, 36, 37, 38, etc. are connected in parallel to the plurality of resistors 31, 32, 33, 34, etc., respectively, and a tube voltage detection circuit 70. The circuit in which a plurality of resistors 31, 32, 33, 34, etc. are connected in series and the circuit in which the resistor capacitors 35, 36, 37, 38, etc. are connected in parallel thereto are all grounded at their midpoints. The total resistance value of the plurality of resistors 31, 32, 33, 34, etc. is represented as Rd. The total capacitance of the plurality of resistor capacitors 35, 36, 37, 38, etc. is represented as Cd.

[0023] The tube voltage detection circuit 70 detects the voltage across one of the resistors 31, 32, 33, 34, etc. (resistor 32 closest to the midpoint), calculates the voltage across the entire resistor circuit based on the detection result, and outputs it as the value of the tube voltage Vx across the X-ray tube 60.

[0024] The high-voltage generator 1 and the X-ray tube 60 are connected by a high-voltage shielded cable 50 that is covered with a conductive shielding layer. The high-voltage shielded cable 50 has stray capacitances 51 and 52. Note that in Fig. 1, the stray capacitances 51 and 52 are shown as part of the circuit. The total capacitance of the stray capacitances 51, 52, etc. is represented as Cc.

[0025] The tube current detection unit 80 is configured to include a current detection unit 81 that detects the current flowing between the wiring 23 between the first rectifier circuit 21 or the second rectifier circuit 22 and the ground, and a calculation unit 82.

[0026] The current detection unit 81 is disposed on the wiring 23 and directly detects the current flowing between the wiring 23 and the ground.

[0027] The calculation unit 82 includes a circuit 83 that obtains a value dVx obtained by differentiating the tube voltage Vx detected by the tube voltage detection unit 30, and a circuit 84 that obtains dVx·Kc by multiplying this value by a predetermined first constant Kc. The first constant Kc is the sum of the capacitance components present between the rectifier circuit 20 and the X-ray tube 60. Specifically, in the circuit of FIG. 1, the first constant Kc is the sum Call of the capacitance Cs of the smoothing capacitor 40, the capacitance Cd of the resistor capacitor, and the stray capacitance Cc of the high-voltage shielded cable 50, and is a value obtained in advance.

[0028] Therefore, the value dVx·Kc output by the circuit 84 of the calculation unit 82 is a current component that flows into the sum Call of the capacitance components present between the rectifier circuit 20 and the X-ray tube 60 when the tube voltage Vx rises.

[0029] The calculation unit 82 also includes a circuit 85 that calculates a value Vx / Kr by dividing the tube voltage Vx detected by the tube voltage detection unit 30 by a predetermined second constant Kr. The second constant Kr is the sum of the resistance components present between the rectifier circuit 20 and the X-ray tube 60. Specifically, in the circuit of Fig. 1, the second constant Kr is the sum Rd of the resistance values ​​of the resistance circuit of the tube voltage detection unit 30, and is a value that has been calculated in advance.

[0030] The value Vx / Kr output by the circuit 85 of the calculation unit 82 is a current component flowing into the sum of the resistance components present between the rectifier circuit 20 and the X-ray tube 60.

[0031] The difference circuit 86 of the calculation unit 82 subtracts the current component value dVx·Kc flowing into the sum of the capacitance components Call and the current component value Vx / Kr flowing into the sum of the resistance components Rd from the current Idma detected by the current detection unit 81. This allows the calculation unit 82 to accurately determine the tube current flowing through the X-ray tube 60 even during the rise of the tube voltage Vx.

[0032] A more detailed explanation will be given below using the graphs in FIGS. 2(a) to 2(g).

[0033] As described above, the calculation unit 82 of the tube current detection unit 80 receives the detection value of the tube voltage Vx detected by the tube voltage detection circuit 70 (see FIG. 2(a)), and also receives the current Idma detected by the current detection unit 81 (see FIG. 2(d)). Circuits 83 and 84 of the calculation unit 82 calculate a product dVx·Kc by multiplying the differential value dVx of the tube voltage Vx by a value (Kc) proportional to the sum Call of the capacitance components (see FIG. 2(e)). Circuit 85 of the calculation unit 82 calculates a quotient Vx / Kr of the tube voltage Vx and a value (Kr) proportional to the resistance component (see FIG. 2(f)). The differential circuit 86 outputs the tube current Ixma (see Figure 2(g)) obtained by subtracting the product dVx·Kc, which is the current component flowing into the sum of the capacitance components Call, and the quotient Vx / Kr, which is the current component flowing into the resistance component Rd, from the current Idma detected by the current detection unit 81.

[0034] The detected current Id detected by the current detection unit 81 is the current flowing through the rectifier circuit 20, and is the total current of the tube current Ixma (FIG. 2(b)) flowing through the X-ray tube 60, the current Icc flowing through the high-voltage shielded cable 50 (capacity Cc), the current Icd flowing through the capacitance Cd of the resistive capacitors 35, 36, 37, 38, etc. of the tube voltage detection unit 30, the current Ics flowing through the capacitance Cs of the smoothing capacitor 40, and the current Ird flowing through the resistors Rd of the resistors 31, 32, 33, 34, etc. of the tube voltage detection unit 30.

[0035] The current Ird flowing through the resistor Rd can be calculated by dividing the tube voltage Vx by the resistance value Rd. Ird=Vx / Rd It is difficult to directly measure the currents Icc, Icd, and Ics that flow through the capacitance Cc of the high-voltage shielded cable 50, the capacitance Cd of the resistor capacitor 35 of the tube voltage detection unit 30, and the capacitance Cs of the smoothing capacitor 40, as well as the sum of these, the current Icma (Figure 2(c)). Icma=(Icc+Icd+Ics) However, Icma can be calculated by multiplying the differential value of the tube voltage Vx by Call, which is the sum of the capacitances Cc, Cd, and Cs. Icma(t)=dVx(t)·Call Call=Cc+Cd+Cs Therefore, based on the above, by setting in advance a constant Kr corresponding to the resistance Rd of the resistors 31, 32, 33, 34, etc., and determining in advance a constant Kc corresponding to the sum Call of the capacitance Cc of the high-voltage shielded cable 50, the capacitance Cd of the resistor capacitors 35, etc. of the tube voltage detection unit 30, and the capacitance Cs of the smoothing capacitor 40, an accurate tube current Ixma can be calculated by calculation in the calculation unit 82 of the tube current detection unit 80 based on the tube voltage Vx output by the tube voltage detection circuit 70 and the detection current Idma of the current detection unit 81.

[0036] That is, circuits 83 and 84 of the calculation unit 82 calculate a current Icma flowing through the sum of capacitances Call as shown in Fig. 2(e) from the tube voltage Vx and constant Kc shown in Fig. 2(a). A circuit 85 of the calculation unit 82 calculates a current Ird flowing through resistor Rd as shown in Fig. 2(f) from the tube voltage Vx and constant Kr shown in Fig. 2(a).

[0037] The circuit 85 subtracts the current Icma (FIG. 2(e)) and the current Ird (FIG. 2(f)) from the detected current Idma (FIG. 2(d)) of the current detection unit 81, thereby calculating a waveform as shown in FIG. 2(g) that is extremely close to the waveform of the actual tube current Ixma in FIG. 2(b).

[0038] As is clear from a comparison of the detected current Idma of the current detection unit 81 in Figure 2(d) with the actual tube current Ixma in Figure 2(b), the detected current Idma (Figure 2(d)) of the current detection unit 81 contains large errors at the rise and fall times.

[0039] In contrast, in the waveform of FIG. 2(g) calculated in this embodiment, errors at the rising and falling edges are removed, and the tube current can be calculated with high accuracy.

[0040] <Another example of the calculation unit 82> The calculation unit 82 of the tube current detection unit 80 shown in FIG. 1 is an analog calculation circuit in the example shown, but may be realized by a digital calculation circuit or software that performs calculations using a CPU or the like.

[0041] FIG. 3 shows an example of a digital arithmetic circuit that realizes the arithmetic unit 82. In FIG. 3, circuits corresponding to the analog circuits in FIG. 1 are assigned the same reference numerals. The arithmetic unit 82 in FIG. 3 includes an A / D converter 87 that samples the detection current Idma received from the current detection unit 81 and converts it into a digital signal, and an A / D converter 88 that samples the tube voltage Vx output by the tube voltage detection circuit 70 and converts it into a digital signal. A differential circuit is provided as circuit 83 that differentiates the tube voltage Vx output by the A / D converter 87. The differential circuit 83 outputs a difference dVx(t) between the current output Vx(t) of the tube voltage detection circuit 70 and the previous output Vx(t-1) (one sampling cycle before). A multiplication circuit 84 multiplies the output of the differential circuit 84 by a constant Kc and outputs dVx(t)·Kc.

[0042] Meanwhile, a multiplication circuit 85 is provided as a circuit 85 that multiplies the tube voltage Vx output by the A / D converter 88 by 1 / Kr. A difference circuit 86 subtracts Vx / Kr output by the multiplication circuit 85 and dVx(t)·Kc output by the multiplication circuit 84 from the detection current Idma output by the A / D converter 87, and outputs the result as the tube current Ixma.

[0043] Furthermore, when the calculation unit 82 of the tube current detection unit 80 is realized by software, the calculation unit 82 is configured by a processor such as a CPU and a memory. The processor reads and executes a program stored in advance in the memory, thereby realizing the functions of the circuits 83 to 86 in Fig. 3 by software.

[0044] <Variation 1> Although the X-ray device 100 of the above-described embodiment has only one X-ray tube 60, it is also possible to configure the device such that multiple types of X-ray tubes 60 are connected in parallel to the high-voltage generator 1 via high-voltage shielded cables 50, and one of the multiple X-ray tubes 60 is selected for use using a high-voltage switch.

[0045] In a configuration in which multiple types of X-ray tubes 60 are connected, the length of the high-voltage shielded cable 50 will differ depending on the selected X-ray tube 60. Therefore, since the first constant Kc is the sum Call of the capacitance Cs of the smoothing capacitor 40, the capacitance Cd of the resistive capacitor, and the stray capacitance Cc of the high-voltage shielded cable 50, the stray capacitance Cc of the high-voltage shielded cable 50 will differ depending on the selected X-ray tube 60, and will therefore have a different value.

[0046] Therefore, in the case of the X-ray device 100 to which multiple types of X-ray tubes 60 are connected, a constant Kc is prepared in advance for each X-ray tube 60, taking into consideration the difference in length of the high-voltage shielded cable 50, and is stored in a memory (not shown) in the calculation unit 82. The control unit (not shown) is configured to select the constant Kc from the memory and set it in the circuit 84 so that the circuit 84 uses the constant Kc corresponding to the selected X-ray tube 60.

[0047] <Variation 2> In the X-ray device 100 of the above-described embodiment, the high-voltage generator 1 may be configured to include a smoothing capacitor switch that can switch whether or not to use the smoothing capacitor 40. In this case, as the constant Lc, Kc when a smoothing capacitor is used and Kc when a smoothing capacitor is not used are prepared in advance and stored in a memory (not shown), and the control unit (not shown) selects Lc from the memory according to the selection status of the smoothing capacitor switch and sets it in the circuit 84. [Explanation of symbols]

[0048] 1. High voltage generator 1a terminal 10. High-Voltage Transformer 11,12 Secondary winding 15 Primary winding 20 Rectifier circuit 23 Wiring 81 Current detection section 30 Tube voltage detection unit 31, 32, 33, 34 Resistance 35, 36, 37, 38 Resistor capacitors 40 Smoothing capacitor 41,42 Capacitor 50 High Voltage Shielded Cable 51,52 Stray capacitance 60 x-ray tube 70 Tube voltage detection circuit 80 Tube current detection unit 81 Current detection section 82 Arithmetic section 83 circuits 84 circuits 85 circuits 86 circuits 87 A / D converter 88 A / D converter 100 X-ray equipment 101 X-ray high voltage device

Claims

1. a high-voltage generator that boosts and rectifies input AC power to a DC high voltage of a predetermined voltage value, and an X-ray tube that receives the DC high voltage of the predetermined voltage value and DC current from the high-voltage generator and generates X-rays; the high voltage generator includes a high voltage transformer that boosts the AC power input, a rectifier circuit that rectifies the AC voltage boosted by the high voltage transformer to generate a DC voltage, a smoothing capacitor that smoothes the DC voltage rectified by the rectifier circuit, a tube voltage detector that detects a tube voltage across both ends of the X-ray tube, and a tube current detector; a high-voltage transformer, the rectifier circuit, and the smoothing capacitor are all connected in parallel to the X-ray tube; the rectifier circuit includes a first rectifier circuit and a second rectifier circuit connected in series, and a ground is connected between the first rectifier circuit and the second rectifier circuit; the current detection unit includes a current detection unit that detects a current flowing between the first rectifier circuit or the second rectifier circuit and the ground, and a calculation unit; the calculation unit differentiates the tube voltage detected by the tube voltage detection unit, multiplies the differentiated tube voltage by a predetermined first constant, and subtracts the differentiated tube voltage divided by a predetermined second constant from the current detected by the current detection unit, thereby determining the tube current flowing through the X-ray tube.

2. 2. The X-ray device according to claim 1, wherein the first constant is a sum of capacitance components present between the rectifier circuit and the X-ray tube, and a value obtained by differentiating the tube voltage and multiplying the result by the first constant is a current component flowing into the capacitance components present between the rectifier circuit and the X-ray tube, an X-ray device characterized in that the second constant is the sum of resistance components existing between the rectifier circuit and the X-ray tube, and a value obtained by dividing the tube voltage by a predetermined second constant is a current component flowing into the resistance components existing between the rectifier circuit and the X-ray tube.

3. 2. The X-ray apparatus according to claim 1, wherein the high voltage generator and the X-ray tube are connected by a shielded cable covered with a conductive shield layer, the tube voltage detection unit includes a resistance circuit in which a plurality of resistors connected in series are connected in parallel to the X-ray tube, resistor capacitors connected in parallel to each of the plurality of resistors, and a tube voltage detection circuit that detects a voltage across both ends of any one of the plurality of resistors and determines a voltage across both ends of the entire resistance circuit based on the detection result, thereby determining a tube voltage across the X-ray tube; the first constant is a predetermined capacitance corresponding to the sum of the capacitance of the smoothing capacitor, the capacitance of the resistor capacitor, and the stray capacitance of the shielded cable, The X-ray device according to claim 1, wherein the second constant is a sum of resistance values ​​of the resistor circuits of the tube voltage detection unit.

4. 2. The X-ray device according to claim 1, wherein the X-ray tube is a plurality of X-ray tubes, the plurality of X-ray tubes being connected in parallel, a switch for selecting an X-ray tube to which a tube voltage and a tube current are supplied is connected to the plurality of X-ray tubes; the value of the first constant is prepared in advance for each of the plurality of X-ray tubes, and the calculation unit selects the value of the first constant corresponding to the X-ray tube selected by the switch and uses it for calculation.

5. 2. The X-ray apparatus according to claim 1, wherein a smoothing capacitor switch is connected to the smoothing capacitor to separate the smoothing capacitor from the rectifier circuit, The value of the first constant is prepared in advance for each of the cases where the smoothing capacitor is not disconnected and where it is disconnected, and the calculation unit selects the value of the first constant to use in calculations depending on whether the smoothing capacitor is disconnected by the smoothing capacitor switch.

6. A tube current calculation device for an X-ray device, a tube current calculation device for calculating a tube current flowing through an X-ray tube of the X-ray device by receiving and differentiating a tube voltage detected by a tube voltage detection unit of the X-ray device, multiplying the differentiated result by a predetermined first constant to obtain a first value, dividing the tube voltage by a predetermined second constant to obtain a second value, and subtracting the first value and the second value from a current detected by a current detection unit of the X-ray device.

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