Imaging system, control device, and method for measuring power supply voltage

Abstract

According to the present invention, an imaging device has a camera device, and a control device connected to the camera device by a power supply line. The camera device has an image sensor, and a capacitor connected in parallel to the image sensor. The control device has a voltage output circuit, a measurement wave output circuit, a measurement circuit, a storage circuit, and a voltage calculation circuit. After a power supply voltage is output to the power supply line by the voltage output circuit, the measurement wave output circuit outputs a measurement wave to the power supply line. After the measurement wave is output to the power supply line, the measurement circuit measures a difference between a physical quantity of the measurement wave and a physical quantity of the reflected wave. The voltage calculation circuit calculates a bias voltage on the basis of the difference, and information stored in the storage circuit.

Description

Imaging system, control device, and power supply voltage measurement method

[0001] The present disclosure relates to an imaging system, a control device, and a method for measuring a power supply voltage.

[0002] The endoscope system includes a scope (camera device) and a control unit (control device). The scope and control unit are connected to each other by a power cable. An image sensor is mounted at the tip of the scope. The control unit outputs a first power supply voltage to the power cable for driving the image sensor. The first power supply voltage is transferred to the scope via the power cable and input to the scope as a second power supply voltage. A voltage drop occurs in the power cable due to the current flowing through the power cable and the resistance value of the power cable. Therefore, the second power supply voltage at the image sensor is lower than the first power supply voltage output from the control unit.

[0003] The magnitude of the current flowing through the power cable varies depending on the operating state of the image sensor. Therefore, the control unit needs to output a high first power supply voltage to the power cable, taking into account the voltage drop caused by changes in current. However, a high first power supply voltage increases the power consumption of the image sensor and the amount of heat generated in the power cable. Therefore, it is necessary to monitor the value of the second power supply voltage in the image sensor and output an optimal first power supply voltage to the power cable.

[0004] In order to monitor the value of the second power supply voltage, a method is being considered in which the resistance value of the power cable is calculated and the value of the second power supply voltage is calculated according to the following equation (1): Vcis=Vout-Rc*Ic (1)

[0005] In equation (1), the voltage value Vcis represents the value of the second power supply voltage, the voltage value Vout represents the value of the first power supply voltage, the resistance value Rc represents the resistance value of the power cable, and the current value Ic represents the value of the current flowing through the power cable.

[0006] The technology disclosed in Patent Document 1 provides a function for adjusting the power supply voltage based on the voltage at the tip of the scope (tip voltage). This technology uses a dedicated cable for detecting the tip voltage to constantly monitor the tip voltage, and adjusts the power supply voltage so that the tip voltage is at an appropriate value.

[0007] Japanese Patent Application Publication No. 2011-206333

[0008] However, when a dedicated cable for detecting the tip voltage is used, it is difficult to miniaturize the endoscope.

[0009] An object of the present disclosure is to provide an imaging system, a control device, and a method for measuring a power supply voltage that are capable of monitoring a power supply voltage supplied to an image sensor and are suitable for miniaturizing a camera device.

[0010] According to a first aspect of the present disclosure, an imaging system includes a camera device and a control device connected to the camera device via a power line. The camera device includes an image sensor and a capacitor. The image sensor generates a video signal based on a power supply voltage input from the power line. The capacitor is connected in parallel to the image sensor. The control device includes a voltage output circuit, a measurement wave output circuit, a measurement circuit, a memory circuit, and a voltage calculation circuit. The voltage output circuit outputs the power supply voltage to the power line. After the power supply voltage is output to the power line, the measurement wave output circuit outputs a measurement wave to the power line to measure a bias voltage applied to the image sensor and the capacitor. After the measurement wave is output to the power line, the measurement circuit receives a reflected wave from the power line and measures the difference between the physical quantity of the measurement wave and the physical quantity of the reflected wave. The memory circuit stores information indicating the relationship between the difference and the bias voltage. The voltage calculation circuit calculates the bias voltage based on the difference and the information.

[0011] According to a second aspect of the present disclosure, in the first aspect, the information may be information in a table indicating a relationship between the difference between each of two or more of the bias voltages and the bias voltage.

[0012] According to a third aspect of the present disclosure, in the second aspect, before the image sensor generates the video signal, the voltage output circuit may sequentially output two or more of the power supply voltages to the power supply line. When each of the two or more power supply voltages is output to the power supply line, the measurement wave output circuit may output the measurement wave to the power supply line. The measurement circuit may measure the difference, may regard the two or more power supply voltages as the two or more bias voltages, and may record information indicating the relationship between the difference between each of the two or more bias voltages and the bias voltage in the table.

[0013] According to a fourth aspect of the present disclosure, the imaging system of the first aspect may further include a splitter electrically connected to the power supply line, the voltage output circuit, the measurement wave output circuit, and the measurement circuit, and the splitter may be disposed between the power supply line and the voltage output circuit, and between the power supply line and a connection point to which the measurement wave output circuit and the measurement circuit are commonly connected.

[0014] According to a fifth aspect of the present disclosure, the camera device of the first aspect may further include a temperature sensor for measuring a temperature of the image sensor. The memory circuit may store information indicating a relationship between the difference between two or more temperatures and the bias voltage. The voltage calculation circuit may calculate the bias voltage based on the difference, the information, and the temperature measured by the temperature sensor.

[0015] According to a sixth aspect of the present disclosure, in the first aspect, the measurement circuit may measure a difference between a phase of the measurement wave and a phase of the reflected wave.

[0016] According to a seventh aspect of the present disclosure, a control device is connected via a power line to an image sensor connected in parallel with a capacitor and generating a video signal based on a power supply voltage input from the power line. The control device includes a voltage output circuit, a measurement wave output circuit, a measurement circuit, a memory circuit, and a voltage calculation circuit. The voltage output circuit outputs the power supply voltage to the power line. After the power supply voltage is output to the power line, the measurement wave output circuit outputs a measurement wave to the power line for measuring a bias voltage applied to the image sensor and the capacitor. After the measurement wave is output to the power line, the measurement circuit receives a reflected wave from the power line and measures the difference between the physical quantity of the measurement wave and the physical quantity of the reflected wave. The memory circuit stores information indicating the relationship between the difference and the bias voltage. The voltage calculation circuit calculates the bias voltage based on the difference and the information.

[0017] According to an eighth aspect of the present disclosure, a method for measuring a power supply voltage includes: outputting a power supply voltage to a power supply line connected to an image sensor connected in parallel to a capacitor and configured to generate a video signal based on the power supply voltage input from the power supply line; outputting a measurement wave to the power supply line after the power supply voltage has been output to the power supply line to measure a bias voltage applied to the image sensor and the capacitor; receiving a reflected wave from the power supply line after the measurement wave has been output to the power supply line; measuring a difference between a physical quantity of the measurement wave and a physical quantity of the reflected wave; and calculating the bias voltage based on the difference and information indicating a relationship between the difference and the bias voltage.

[0018] According to the above aspects, the imaging system, the control device, and the method for measuring the power supply voltage are capable of monitoring the power supply voltage supplied to the image sensor, and are suitable for miniaturizing the camera device.

[0019] FIG. 1 is a schematic diagram showing the configuration of an endoscope system according to an embodiment. FIG. 2 is a block diagram showing the configurations of a camera unit and a control unit included in the endoscope system according to the embodiment. FIG. 3 is a graph showing the relationship between the voltage applied to a capacitor and the amount of change in the capacitance value of the capacitor in the endoscope system according to the embodiment. FIG. 4 is a diagram showing an equivalent circuit for an AC signal in the embodiment. FIG. 5 is a graph showing the voltage of an AC signal in the embodiment. FIG. 6 is a graph showing the voltage of an AC signal in the embodiment. FIG. 7 is a flowchart showing the procedure of processing executed by the control unit included in the endoscope system according to the embodiment. FIG. 8 is a timing chart showing example waveforms of a measurement wave and a reflected wave in the embodiment. FIG. 9 is a graph showing the temperature characteristics of the capacitance value of a capacitor in an endoscope system according to a modified embodiment. FIG. 10 is a block diagram showing the configurations of a camera unit and a control unit included in the endoscope system according to a modified embodiment.

[0020] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an endoscope system having an imaging device will be described below with reference to the accompanying drawings.

[0021] Fig. 1 shows the configuration of an endoscope system 1 according to an embodiment. The endoscope system 1 shown in Fig. 1 includes an endoscope insertion section 2, a transmission cable 3, an operation section 4, a connector section 5, a control unit 6, and a display device 7. The endoscope insertion section 2, the transmission cable 3, the operation section 4, and the connector section 5 constitute a scope 8 (endoscope).

[0022] The endoscope insertion section 2 has an insertion section 2a. The insertion section 2a is part of the transmission cable 3. The insertion section 2a is inserted into a living body, which is a subject. The endoscope insertion section 2 generates a video signal by capturing an image of the inside of the subject. The endoscope insertion section 2 outputs the generated video signal to the control unit 6. A camera unit 9 shown in FIG. 2 is disposed at the tip 2b of the insertion section 2a. An operation section 4 is connected to the end of the insertion section 2a opposite to the tip 2b. The operation section 4 receives various operations for the endoscope insertion section 2 from the user.

[0023] The transmission cable 3 connects the camera unit 9 and the connector section 5. A video signal generated by the camera unit 9 is output to the connector section 5 via the transmission cable 3.

[0024] The connector section 5 is connected to the transmission cable 3 and the control unit 6. The connector section 5 performs predetermined processing on the video signal output from the endoscope insertion section 2. The connector section 5 outputs the video signal to the control unit 6.

[0025] The control unit 6 performs image processing on the video signal output from the connector section 5. Furthermore, the control unit 6 controls the entire endoscope system 1 in an integrated manner.

[0026] The display device 7 displays an image based on the video signal processed by the control unit 6. The display device 7 also displays various information related to the endoscope system 1.

[0027] The endoscope system 1 has a camera unit 9 (camera device) and a control unit 6 (control device) shown in Fig. 2. Fig. 2 shows the configurations of the camera unit 9 and the control unit 6. The camera unit 9 is disposed at the tip 2b of the scope 8. The operation unit 4, connector unit 5, and display device 7 are not shown in Fig. 2. The transmission cable 3 shown in Fig. 1 has a power supply line 20, a reference line 21, and a video signal line 22 shown in Fig. 2. The camera unit 9 and the control unit 6 are connected to each other by the power supply line 20, the reference line 21, and the video signal line 22.

[0028] The endoscope system 1 includes a light source device that generates illumination light to be irradiated onto the subject (not shown in FIG. 2).

[0029] The camera unit 9 has an image sensor 10 and a capacitor (capacitor) 11. The control unit 6 has a voltage output circuit 12, a measurement wave output circuit 13, a phase difference measurement circuit 14, a memory circuit 15, a voltage calculation circuit 16, a voltage adjustment circuit 17, a splitter 18, a video signal processing circuit 19, and a resistor Rh.

[0030] For example, the voltage output circuit 12 is a voltage regulator. The voltage output circuit 12 is electrically connected to a power supply line 20 via a splitter 18. The voltage output circuit 12 generates a power supply voltage, which is a direct current (DC) voltage, and outputs the power supply voltage to the power supply line 20. For example, the power supply voltage is 3.3 V. The power supply line 20 is a signal line arranged in the transmission cable 3. The power supply line 20 transfers the power supply voltage to the camera unit 9. The power supply voltage transferred by the power supply line 20 is input to the image sensor 10 and capacitor 11 of the camera unit 9.

[0031] The reference line 21 is a signal line disposed in the transmission cable 3. The reference line 21 transfers a reference voltage lower than the power supply voltage from the control unit 6 to the camera unit 9. For example, the reference voltage is a ground voltage (0 V). The reference voltage transferred by the reference line 21 is input to the image sensor 10 and capacitor 11 of the camera unit 9.

[0032] The image sensor 10 and the capacitor 11 are connected to a power supply line 20 and a reference line 21. The image sensor 10 and the capacitor 11 are connected in parallel with each other between the power supply line 20 and the reference line 21. The image sensor 10 generates a video signal based on the power supply voltage and the reference voltage, and outputs the video signal to a video signal line 22. The capacitor 11 is disposed near the image sensor 10. For example, the capacitor 11 is a ceramic capacitor. The capacitor 11 functions as a bypass capacitor.

[0033] The measurement wave output circuit 13 is electrically connected to the power supply line 20 via a resistor Rh and a splitter 18. The measurement wave output circuit 13 generates a measurement wave for measuring the bias voltage applied to the image sensor 10 and the capacitor 11, and outputs the measurement wave to the power supply line 20. For example, the measurement wave is an alternating current (AC) signal. The measurement wave is applied to the image sensor 10 and the capacitor 11 and is reflected by the image sensor 10 and the capacitor 11. The reflected wave of the measurement wave is input to the phase difference measurement circuit 14 via the power supply line 20.

[0034] The phase difference measurement circuit 14 is electrically connected to the power line 20 via a splitter 18. The phase difference measurement circuit 14 receives the reflected wave and measures the difference between the phase of the measurement wave and the phase of the reflected wave. In other words, the phase difference measurement circuit 14 measures the phase difference between the measurement wave and the reflected wave.

[0035] The memory circuit 15 is a memory that stores in advance information indicating the relationship between the phase difference and the bias voltage. For example, the memory circuit 15 stores table information in which two or more phase differences are associated with two or more bias voltages. The voltage calculation circuit 16 calculates the bias voltage based on the phase difference measured by the phase difference measurement circuit 14 and the information stored in the memory circuit 15. The bias voltage indicates the power supply voltage applied to the image sensor 10 and the capacitor 11.

[0036] Through the above processing, the relationship between the power supply voltage output from the voltage output circuit 12 and the bias voltage applied to the image sensor 10 and the capacitor 11 is obtained. The voltage adjustment circuit 17 adjusts the power supply voltage generated by the voltage output circuit 12 based on this relationship.

[0037] The splitter 18 is electrically connected to the power supply line 20, the voltage output circuit 12, the measurement wave output circuit 13, and the phase difference measurement circuit 14. The splitter 18 is disposed between the power supply line 20 and the voltage output circuit 12. The splitter 18 is also disposed between the power supply line 20 and a connection point P1 to which the measurement wave output circuit 13 and the phase difference measurement circuit 14 are commonly connected. The splitter 18 is disposed to separate DC signals from AC signals. The splitter 18 includes a coil component connected to the voltage output circuit 12 and a capacitance component connected to the measurement wave output circuit 13 and the phase difference measurement circuit 14.

[0038] Splitter 18 outputs the power supply voltage output from voltage output circuit 12 to power supply line 20 and blocks the input of power supply voltage from voltage output circuit 12 to measurement wave output circuit 13 and phase difference measurement circuit 14. Splitter 18 outputs the measurement wave output from phase difference measurement circuit 14 to power supply line 20 and blocks the input of the measurement wave from phase difference measurement circuit 14 to voltage output circuit 12. Splitter 18 outputs the reflected wave output from power supply line 20 to phase difference measurement circuit 14 and blocks the input of the reflected wave from power supply line 20 to voltage output circuit 12.

[0039] The video signal line 22 is a signal line arranged in the transmission cable 3. The video signal line 22 transfers the video signal to the control unit 6. The video signal processing circuit 19 receives the video signal transferred by the video signal line 22. The video signal processing circuit 19 performs predetermined signal processing on the video signal and outputs the video signal to the display device 7.

[0040] The voltage calculation circuit 16 may be configured as a digital circuit including at least one of a processor and a logic circuit. For example, the processor is a CPU (Central Processing Unit). For example, the logic circuit is at least one of an ASIC (Application Specific Integrated Circuit) and an FPGA (Field-Programmable Gate Array). The voltage calculation circuit 16 may include one or more processors. The voltage calculation circuit 16 may include one or more logic circuits.

[0041] The computer of the control unit 6 may load a program and execute the loaded program. The program includes instructions that define the operation of the voltage calculation circuit 16. In other words, the functions of the voltage calculation circuit 16 may be realized by software. The program may be transmitted from a computer storing the program to the control unit 6 via a transmission medium or by transmission waves in the transmission medium. A "transmission medium" that transmits the program is a medium that has the function of transmitting information. Media that have the function of transmitting information include networks (communication networks) such as the Internet and communication lines (communication lines) such as telephone lines. The above-mentioned program may realize part of the above-mentioned functions. Furthermore, the above-mentioned program may be a difference file (difference program). The above-mentioned functions may be realized by combining a program already recorded on the computer with the difference program.

[0042] The relationship between the bias voltage applied to the image sensor 10 and the capacitor 11 and the phase difference between the measurement wave and the reflected wave will be described with reference to FIGS.

[0043] Fig. 3 shows the relationship between the voltage applied to capacitor 11 and the amount of change in the capacitance value of capacitor 11. The horizontal axis of the graph shown in Fig. 3 represents the voltage [V] applied to capacitor 11. The vertical axis of the graph shown in Fig. 3 represents the amount of change [%] in the capacitance value of capacitor 11 caused by the application of that voltage.

[0044] 3, as the voltage applied to the capacitor 11 increases, the capacitance value of the capacitor 11 decreases. That is, the capacitance value of the capacitor 11 changes in response to changes in the voltage applied to the capacitor 11. Therefore, the capacitance value of the capacitor 11 and the voltage of the capacitor 11 can be correlated with each other.

[0045] 4 shows an equivalent circuit for an AC signal. The endoscope system 1 is represented as an RC integrator circuit having resistors Rh, Z1, and a capacitor 11. Resistor Z1 represents the resistance component of the power supply line 20. The AC signal output from the measurement wave output circuit 13 is input to input terminal IN1. The AC signal is also output from output terminal OUT1 and input to the phase difference measurement circuit 14.

[0046] The capacitor 11 has a capacitance value Co. As described above, the capacitance value of the capacitor 11 changes in response to changes in the power supply voltage. The change in the capacitance value of the capacitor 11 changes the transfer function of the equivalent circuit shown in FIG. 4, and changes the phase of the AC signal output from the output terminal OUT1. Therefore, the capacitance value of the capacitor 11 and the phase difference between the measurement wave and the reflected wave can be correlated.

[0047] When the voltage of the AC signal input to the input terminal IN1 is represented as ACin and the voltage of the AC signal output from the output terminal OUT1 is represented as ACout, the relationship between the voltage ACin and the voltage ACout is expressed by the following equation (2).

[0048]

[0049] The impedance Zc in equation (2) is expressed by the following equation (3) including the capacitance value Co of the capacitor 11. The capacitance value Co changes depending on the voltage applied to the capacitor 11.

[0050]

[0051] The voltage ACout is expressed by equation (4) obtained by modifying equation (2).

[0052]

[0053] On the other hand, the phase difference θ between the voltage ACin and the voltage ACout is expressed by the following equation (5).

[0054]

[0055] As shown in equation (5), when the impedance component Zc changes, the phase difference θ changes. Also, as shown in equation (3), when the capacitance value Co changes, the impedance component Zc changes. Therefore, when the capacitance value Co changes, the phase difference θ changes.

[0056] 5 shows an example of the waveforms of the voltage ACin and the voltage ACout. The horizontal axis of the graph shown in Fig. 5 represents time [microseconds]. The vertical axis of the graph shown in Fig. 5 represents voltage [mV].

[0057] Line L1 shows the waveform of voltage ACin. The frequency of voltage ACin is 100 kHz. Line L2 shows the waveform of voltage ACout when capacitance value Co is at a normal value. Line L3 shows the waveform of voltage ACout when capacitance value Co is 80% of the normal value.

[0058] Figure 6 shows an enlarged view of range R1 in Figure 5. Arrow PD1 indicates the phase difference between voltages ACin and ACout when capacitance value Co is at its normal value. Arrow PD2 indicates the phase difference between voltages ACin and ACout when capacitance value Co is 80% of its normal value. The length of arrow PD2 is different from the length of arrow PD1. In other words, when capacitance value Co changes, the phase difference between voltages ACin and ACout changes.

[0059] As shown in FIG. 3, the capacitance value of capacitor 11 and the voltage of capacitor 11 can be correlated with each other. Furthermore, as shown in equation (5) and FIG. 5, the capacitance value of capacitor 11 and the phase difference can be correlated with each other. Therefore, the phase difference and the voltage of capacitor 11 can be correlated with each other. By measuring the phase difference between the measurement wave and the reflected wave, control unit 6 can measure the voltages applied to image sensor 10 and capacitor 11.

[0060] The process executed by the control unit 6 to adjust the power supply voltage will be described with reference to Fig. 7. Fig. 7 shows the procedure of the process executed by the control unit 6.

[0061] Immediately after the image sensor 10 is started up, the voltage output circuit 12 generates a power supply voltage for initial measurement and outputs the power supply voltage to the power supply line 20 (step S100).

[0062] When image sensor 10 is activated and before image sensor 10 generates a video signal, the voltage drop in power supply line 20 is approximately zero. At this time, image sensor 10 stops generating a video signal, and the current consumption of image sensor 10 is approximately zero. Therefore, the bias voltage applied to image sensor 10 and capacitor 11 is approximately the same as the power supply voltage output from voltage output circuit 12. The capacitance value of capacitor 11 changes depending on the power supply voltage.

[0063] After the power supply voltage is output to the power supply line 20, the measurement wave output circuit 13 outputs a measurement wave to the power supply line 20 (step S105).

[0064] After the measurement wave is output to the power supply line 20, the phase difference measurement circuit 14 receives the reflected wave from the power supply line 20 (step S110).

[0065] After the reflected wave is received, the phase difference measurement circuit 14 measures the phase of the reflected wave. The phase of the measurement wave generated by the measurement wave output circuit 13 is known. The phase difference measurement circuit 14 receives information about the phase of the measurement wave from the measurement wave output circuit 13. The phase difference measurement circuit 14 measures the phase difference between the measurement wave and the reflected wave based on the measured phase of the reflected wave and the phase of the measurement wave indicated by the information received from the measurement wave output circuit 13 (step S115).

[0066] The voltage calculation circuit 16 receives the phase difference information from the phase difference measurement circuit 14 and records the phase difference and the bias voltage as table information in the memory circuit 15 (step S120). The bias voltage is the voltage value of the power supply voltage generated by the voltage output circuit 12.

[0067] After the phase difference and bias voltage are recorded in the memory circuit 15, a control circuit (not shown in FIG. 2) determines whether to end the initial measurement (step S125). In the initial measurement, two or more power supply voltages are sequentially output to the power supply line 20, and the phase difference corresponding to each power supply voltage is measured. Therefore, steps S100 to S120 are executed two or more times in the initial measurement. When the number of times steps S100 to S120 have been executed is the same as a preset number, the control circuit determines that the initial measurement should be ended.

[0068] If the number of times steps S100 to S120 have been executed is less than a predetermined number, the control circuit determines not to end the initial measurement. In this case, step S100 is executed. The voltage output circuit 12 generates a power supply voltage having a voltage value different from the voltage value of the power supply voltage generated last time, and outputs the power supply voltage to the power supply line 20.

[0069] When the control circuit determines that the initial measurement is to be completed, the voltage output circuit 12 generates a power supply voltage and outputs the power supply voltage to the power supply line 20 (step S130). At this time, the image sensor 10 may start generating a video signal.

[0070] After the power supply voltage is output to the power supply line 20, the measurement wave output circuit 13 outputs a measurement wave to the power supply line 20 (step S135).

[0071] After the measurement wave is output to the power supply line 20, the phase difference measurement circuit 14 receives the reflected wave from the power supply line 20 (step S140).

[0072] After the reflected wave is received, the phase difference measurement circuit 14 measures the phase difference between the measurement wave and the reflected wave by using the same method as in step S115 (step S145).

[0073] After the phase difference between the measurement wave and the reflected wave is measured, the voltage calculation circuit 16 receives information about the phase difference from the phase difference measurement circuit 14. The voltage calculation circuit 16 references the table information stored in the memory circuit 15 and obtains the bias voltage corresponding to the measured phase difference from the table information (step S150). The same phase difference as the measured phase difference is not necessarily recorded in the table information. The voltage calculation circuit 16 may obtain the bias voltage corresponding to the phase difference closest to the measured phase difference from the table information. Alternatively, the voltage calculation circuit 16 may interpolate the information recorded in the table information to calculate the bias voltage corresponding to the measured phase difference.

[0074] After the bias voltage is calculated, the voltage adjustment circuit 17 acquires information about the bias voltage from the voltage calculation circuit 16. If the bias voltage value is smaller than a preset reference voltage value, the voltage adjustment circuit 17 increases the value of the power supply voltage set in the voltage output circuit 12. If the bias voltage value is larger than the reference voltage value, the voltage adjustment circuit 17 decreases the value of the power supply voltage set in the voltage output circuit 12. This causes the voltage adjustment circuit 17 to adjust the power supply voltage (step S155).

[0075] While the image sensor 10 is operating, the control unit 6 may repeat steps S135 to S155. The control unit 6 may execute steps S135 to S155 during a video output period in which the image sensor 10 outputs a video signal to the video signal line 22. Alternatively, the control unit 6 may execute steps S135 to S155 during a blanking period in which the image sensor 10 stops outputting a video signal.

[0076] The measurement wave output by the measurement wave output circuit 13 is not limited to an AC signal. The measurement wave may have any voltage value that changes over time. The measurement wave may be a sine wave, a square wave, a triangular wave, a sawtooth wave, a single pulse wave, or two or more consecutive pulse waves.

[0077] In the above example, the phase difference measuring circuit 14 measures the phase difference between the measurement wave and the reflected wave. The difference between the physical quantity of the measurement wave and the physical quantity of the reflected wave is not limited to the phase difference.

[0078] 8 shows an example of the waveforms of the measurement wave and the reflected wave. The horizontal direction in FIG. 8 represents time. The vertical direction in FIG. 8 represents voltage.

[0079] A measurement wave VIN is output from the control unit 6 to the power supply line 20, and a reflected wave VOUT is output from the power supply line 20 to the control unit 6. The measurement circuit of the control unit 6 may measure the difference DF1 between the amplitude of the measurement wave VIN and the amplitude of the reflected wave VOUT. If the measurement wave VIN is a pulse wave, a square wave, or the like, the measurement circuit may measure a slew rate indicating the amount of change A1 of the reflected wave VOUT per unit time T1. If the measurement wave VIN is a pulse wave, a square wave, or the like, the measurement circuit may measure the amount of delay DL1 of the reflected wave VOUT relative to the measurement wave VIN. If the measurement wave VIN is a pulse wave, a square wave, or the like, the measurement circuit may measure the degree of deterioration of the waveform of the reflected wave VOUT relative to the waveform of the measurement wave VIN. The equivalent equations for the amplitude ratio G of ACout to ACin are expressed by equations (6), (7), and (8), and, similar to the phase difference, the amplitude ratio |G| changes depending on the change in capacitance (Zc).

[0080]

[0081] The control unit 6 may have a coil instead of the resistor Rh.

[0082] An imaging system (endoscopic system 1) according to each aspect of the present disclosure includes a camera unit 9 (camera device) and a control unit 6 (control device) connected to the camera unit 9 via a power line 20. The camera unit 9 includes an image sensor 10 and a capacitor 11 (capacitor). The image sensor 10 generates a video signal based on a power supply voltage input from the power line 20. The capacitor 11 is connected in parallel to the image sensor 10. The control unit 6 includes a voltage output circuit 12, a measurement wave output circuit 13, a phase difference measurement circuit 14, a memory circuit 15, and a voltage calculation circuit 16. The voltage output circuit 12 outputs a power supply voltage to the power line 20. After the power supply voltage is output to the power line 20, the measurement wave output circuit 13 outputs a measurement wave to the power line 20 to measure the bias voltage applied to the image sensor 10 and the capacitor 11. After the measurement wave is output to the power line 20, the phase difference measurement circuit 14 receives a reflected wave from the power line 20 and measures the difference between the physical quantity of the measurement wave and the physical quantity of the reflected wave. The memory circuit 15 stores information indicating the relationship between the difference and the bias voltage. The voltage calculation circuit 16 calculates the bias voltage based on the difference and the information.

[0083] Each aspect of the present disclosure may include the following modifications: The information stored in the storage circuitry 15 is information in a table indicating the relationship between the bias voltage and the difference in the physical quantity described above for each of two or more bias voltages.

[0084] Each aspect of the present disclosure may include the following modifications. Before the image sensor 10 generates a video signal, the voltage output circuit 12 sequentially outputs two or more power supply voltages to the power supply line 20. When each of the two or more power supply voltages is output to the power supply line 20, the measurement wave output circuit 13 outputs a measurement wave to the power supply line 20. The phase difference measurement circuit 14 measures the difference between the above physical quantities, regards the two or more power supply voltages as two or more bias voltages, and records information in a table indicating the relationship between the difference between the physical quantities for each of the two or more bias voltages and the bias voltage.

[0085] Each aspect of the present disclosure may include the following modifications: The endoscope system 1 has a splitter 18 electrically connected to a power supply line 20, a voltage output circuit 12, a measurement wave output circuit 13, and a phase difference measurement circuit 14. The splitter 18 is disposed between the power supply line 20 and the voltage output circuit 12, and also between the power supply line 20 and a connection point P1 to which the measurement wave output circuit 13 and the phase difference measurement circuit 14 are commonly connected.

[0086] Each aspect of the present disclosure may include the following modifications: The phase difference measuring circuit 14 measures the difference between the phase of the measurement wave and the phase of the reflected wave.

[0087] As described above, the voltage calculation circuit 16 calculates the bias voltage based on the phase difference measured by the phase difference measurement circuit 14 and the information stored in the memory circuit 15. The bias voltage indicates the power supply voltage applied to the image sensor 10 and the capacitor 11. Therefore, the endoscope system 1 can monitor the power supply voltage supplied to the image sensor 10. No dedicated cable is required to transfer the power supply voltage from the camera unit 9 to the control unit 6. Therefore, the endoscope system 1 is suitable for miniaturizing the camera device.

[0088] (Modification) A modification of the embodiment will be described below. Since the capacitor 11 is disposed near the image sensor 10, the temperature of the capacitor 11 also rises as the temperature of the image sensor 10 rises.

[0089] FIG. 9 shows the temperature characteristics of the capacitance value of capacitor 11. The horizontal axis of the graph shown in FIG. 9 represents the temperature [°C] of capacitor 11. The vertical axis of the graph shown in FIG. 9 represents the rate of change [%] of the capacitance value of capacitor 11. As shown in FIG. 9, when the temperature of capacitor 11 increases, the capacitance value of capacitor 11 decreases. Below, a method for suppressing a decrease in the measurement accuracy of the bias voltage due to changes in the temperature of capacitor 11 will be described.

[0090] First, the first method will be described. In the first method, the camera unit 9 is preheated so that the temperature of the capacitor 11 becomes approximately the same as the temperature of the image sensor 10 in an operational state. With the camera unit 9 in a heated state, steps S105 to S120 shown in FIG. 7 are executed.

[0091] Next, a second method will be described. The endoscope system 1 shown in Fig. 2 is changed to an endoscope system 1A shown in Fig. 10. Fig. 10 shows the configuration of the endoscope system 1A. The same components as those shown in Fig. 2 will not be described.

[0092] The camera unit 9 shown in Fig. 2 is changed to a camera unit 9A shown in Fig. 10. In the camera unit 9A, the image sensor 10 is changed to an image sensor 10A. A temperature sensor 23 is disposed inside the image sensor 10A. The temperature sensor 23 measures the temperature of the image sensor 10A and generates temperature data indicating the temperature.

[0093] The image sensor 10A outputs the temperature data to the video signal line 22. When the image sensor 10A generates a video signal, the temperature data may be added to the video signal. The video signal processing circuit 19 receives the temperature data transferred via the video signal line 22 and outputs the temperature data to the voltage calculation circuit 16.

[0094] The memory circuit 15 stores table information in which two or more phase differences at each of two or more temperatures are associated with two or more bias voltages. The voltage calculation circuit 16 calculates the bias voltage based on the phase difference measured by the phase difference measurement circuit 14, the temperature data output from the video signal processing circuit 19, and the information stored in the memory circuit 15.

[0095] 7 , image sensor 10A outputs temperature data to video signal line 22. In step S120, voltage calculation circuit 16 receives information about the phase difference from phase difference measurement circuit 14 and temperature data from video signal processing circuit 19. Voltage calculation circuit 16 records the phase difference, bias voltage, and temperature in memory circuit 15 as table information.

[0096] Steps S100 to S120 are executed two or more times while the camera unit 9 is heated. For example, the temperature measured by the temperature sensor 23 at this time is a first temperature, and two or more phase differences and two or more bias voltages at the first temperature are recorded in the table information.

[0097] Furthermore, steps S100 to S120 are executed two or more times while the camera unit 9 is heated. For example, the temperature measured by the temperature sensor 23 at this time is a second temperature different from the first temperature, and two or more phase differences and two or more bias voltages at the second temperature are recorded in the table information. Furthermore, steps S100 to S120 may be executed two or more times at one or more temperatures different from the first temperature and the second temperature.

[0098] 7 , image sensor 10A outputs temperature data to video signal line 22. In step S150, voltage calculation circuit 16 receives phase difference information from phase difference measurement circuit 14 and temperature data from video signal processing circuit 19. Voltage calculation circuit 16 refers to table information stored in memory circuit 15 and obtains, from the table information, a bias voltage corresponding to the measured phase difference and temperature.

[0099] Each aspect of the present disclosure may include the following modifications. The camera unit 9A has a temperature sensor 23 that measures the temperature of the image sensor 10. The memory circuit 15 stores information indicating the relationship between the bias voltage and the difference between the physical quantity of the measurement wave and the physical quantity of the reflected wave at two or more temperatures. The voltage calculation circuit 16 calculates the bias voltage based on the difference, the information about the difference, and the temperature measured by the temperature sensor 23.

[0100] According to the first and second methods described above, even when the temperature of the capacitor 11 changes, the measurement accuracy of the bias voltage is prevented from decreasing.

[0101] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments and their modifications. Addition, omission, substitution, and other modifications of the configuration are possible within the scope of the spirit of the present invention. Furthermore, the present invention is not limited by the above description, but is limited only by the scope of the appended claims.

[0102] According to the present disclosure, an imaging system, a control device, and a method for measuring a power supply voltage are capable of monitoring the power supply voltage supplied to an image sensor, and are suitable for miniaturizing a camera device.

[0103] 1, 1A Endoscope system 2 Endoscope insertion section 2a Insertion section 2b Tip 3 Transmission cable 4 Operation section 5 Connector section 6 Control unit 7 Display device 8 Scope 9, 9A Camera unit 10, 10A Image sensor 11 Capacitor 12 Voltage output circuit 13 Measurement wave output circuit 14 Phase difference measurement circuit 15 Memory circuit 16 Voltage calculation circuit 17 Voltage adjustment circuit 18 Splitter 19 Video signal processing circuit 20 Power supply line 21 Reference line 22 Video signal line 23 Temperature sensor

Claims

1. An imaging system comprising: a camera device; and a control device connected to the camera device by a power line, wherein the camera device comprises an image sensor that generates a video signal based on a power supply voltage input from the power line; and a capacitor connected in parallel to the image sensor, and wherein the control device comprises: a voltage output circuit that outputs the power supply voltage to the power line; a measurement wave output circuit that outputs a measurement wave to the power line after the power supply voltage has been output to the power line, the measurement wave being used to measure a bias voltage applied to the image sensor and the capacitor; a measurement circuit that receives a reflected wave from the power line after the measurement wave has been output to the power line, and measures the difference between the physical quantity of the measurement wave and the physical quantity of the reflected wave; a memory circuit that stores information indicating the relationship between the difference and the bias voltage; and a voltage calculation circuit that calculates the bias voltage based on the difference and the information.

2. The imaging system according to claim 1, wherein the information is information in a table showing the relationship between the difference and each of two or more bias voltages.

3. The imaging system of claim 2, wherein before the image sensor generates the video signal, the voltage output circuit sequentially outputs two or more of the power supply voltages to the power supply line, and when each of the two or more power supply voltages is output to the power supply line, the measurement wave output circuit outputs the measurement wave to the power supply line, and the measurement circuit measures the difference, regards the two or more power supply voltages as the two or more bias voltages, and records information in the table indicating the relationship between the difference and the bias voltage for each of the two or more bias voltages.

4. The imaging system according to claim 1, further comprising a splitter electrically connected to the power supply line, the voltage output circuit, the measurement wave output circuit, and the measurement circuit, the splitter being disposed between the power supply line and the voltage output circuit, and between the power supply line and a connection point to which the measurement wave output circuit and the measurement circuit are commonly connected.

5. The imaging system according to claim 1, wherein the camera device has a temperature sensor that measures the temperature of the image sensor, the memory circuit stores information indicating the relationship between the difference at two or more temperatures and the bias voltage, and the voltage calculation circuit calculates the bias voltage based on the difference, the information, and the temperature measured by the temperature sensor.

6. The imaging system according to claim 1, wherein the measurement circuit measures the difference between the phase of the measurement wave and the phase of the reflected wave.

7. A control device connected by a power supply line to an image sensor connected in parallel with a capacitor and generating a video signal based on a power supply voltage input from the power supply line, the control device comprising: a voltage output circuit that outputs the power supply voltage to the power supply line; a measurement wave output circuit that outputs a measurement wave to the power supply line after the power supply voltage has been output to the power supply line in order to measure a bias voltage applied to the image sensor and the capacitor; a measurement circuit that receives a reflected wave from the power supply line after the measurement wave has been output to the power supply line and measures the difference between the physical quantity of the measurement wave and the physical quantity of the reflected wave; a memory circuit that stores information indicating the relationship between the difference and the bias voltage; and a voltage calculation circuit that calculates the bias voltage based on the difference and the information.

8. A method for measuring a power supply voltage, comprising: a step of outputting the power supply voltage to a power supply line connected to an image sensor that is connected in parallel with a capacitor and that generates a video signal based on the power supply voltage input from the power supply line; a step of outputting a measurement wave to the power supply line after the power supply voltage has been output to the power supply line to measure a bias voltage applied to the image sensor and the capacitor; a step of receiving a reflected wave from the power supply line after the measurement wave has been output to the power supply line; a step of measuring a difference between a physical quantity of the measurement wave and a physical quantity of the reflected wave; and a step of calculating the bias voltage based on the difference and information indicating the relationship between the difference and the bias voltage.

Images