Strobe device, camera system, and light source control method

Abstract

A single strobe unit should be able to effectively serve as a light source for both rolling shutter and global shutter cameras. [Solution] The strobe device 10 has a resistor 68 provided in the circuit connecting a pair of discharge electrodes 24, 26 and a main capacitor 48, a bypass circuit 69 that bypasses the resistor 68, and a thyristor 70 that opens and closes the bypass circuit 69. When the camera 12 connected to the strobe device 10 is a rolling shutter, the thyristor 70 is turned off, and when it is a global shutter, the thyristor 70 is turned on.

Description

Technical Field

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[0005]

[0001] The present invention relates to a strobe device, a camera system, and a light source control method, and more particularly to a strobe device, a camera system, and a light source control method used in an electronic shutter type camera.

Background Art

[0002] Electronic shutter type cameras are known to include those of the rolling shutter method and those of the global shutter method (for example, Patent Document 1). As a strobe device for an electronic shutter type camera, there is known one that emits light in accordance with the reading timing of pixel values of an image pickup device having a plurality of pixels (for example, Patent Documents 2 and 3).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the rolling shutter method, batch reading of simultaneous exposure is performed, and in the global shutter method, sequential reading of line exposure is performed. Therefore, the light emission patterns required for a strobe device for an electronic shutter type camera are different between the rolling shutter method and the global shutter method. <00,000,31> As a result, a strobe device for an electronic shutter type camera requires a dedicated one for each of the rolling shutter method and the global shutter method.

[0006] In view of the above background, the present invention aims to provide a single strobe device that can effectively serve as a light source for both rolling shutter and global shutter cameras. [Means for solving the problem]

[0007] To solve the above problems, one aspect of the present invention provides a strobe device comprising: a flash discharge tube having a pair of discharge electrodes and a trigger electrode; a high-voltage power supply unit that generates a DC high voltage; a main capacitor that stores the charge of the DC high voltage output by the high-voltage power supply unit and applies the discharge voltage to the pair of discharge electrodes; and a trigger circuit that generates a trigger voltage to be applied to the trigger electrode, wherein the device comprises a resistor provided in a circuit connecting the pair of discharge electrodes and the main capacitor; a bypass circuit that bypasses the resistor; a switching element that opens and closes the bypass circuit; and a control device that controls the opening and closing of the switching element, wherein the control device has a signal input unit that inputs a shutter identification signal that identifies whether the camera connected to the strobe device is a rolling shutter or a global shutter, and controls the switching element to an OFF state when the shutter identification signal indicates a rolling shutter, and to an ON state when the shutter identification signal indicates a global shutter.

[0008] To solve the above problems, one aspect of the present invention provides a camera system comprising: a camera having an electronic shutter; a flash discharge tube having a pair of discharge electrodes and a trigger electrode; a high-voltage power supply unit that generates a DC high voltage; a main capacitor that stores the charge of the DC high voltage output by the high-voltage power supply unit and applies the discharge voltage to the discharge electrodes; a trigger circuit that generates a trigger voltage to be applied to the trigger electrode; a resistor provided in a circuit connecting the pair of discharge electrodes and the main capacitor; a bypass circuit that bypasses the resistor; and a switching element that opens and closes the bypass circuit, wherein the strobe device turns the switching element off when the electronic shutter of the camera is a rolling shutter, and turns the switching element on when the electronic shutter of the camera is a global shutter.

[0009] To solve the above problems, one aspect of the present invention is a light source control method for a camera having an electronic shutter, wherein a flash discharge tube connected to a main capacitor is used as the light source, and when the electronic shutter of the camera is a rolling shutter, the main capacitor and the flash discharge tube are connected with a resistor in between, and when the electronic shutter of the camera is a global shutter, the main capacitor and the flash discharge tube are connected without the resistor in between. [Effects of the Invention]

[0010] According to the above embodiment, a single strobe device can effectively serve as a light source for both rolling shutter and global shutter cameras. [Brief explanation of the drawing]

[0011] [Figure 1] Electrical circuit diagram showing an embodiment of the strobe device and camera system according to the present invention. [Figure 2] Time chart of the signal controlling the strobe light emission of the strobe device according to this embodiment [Figure 3]A graph showing the light emission pattern of the strobe device according to this embodiment. [Modes for carrying out the invention]

[0012] Embodiments of the strobe device and camera system according to the present invention will be described below with reference to the figures.

[0013] As shown in Figure 1, the camera system according to this embodiment includes an electronic shutter camera 12 (hereinafter referred to as camera 12) and a strobe device 10 that is communicatively connected to camera 12 and serves as the light source for camera 12.

[0014] The camera 12 includes an imaging unit 14 using a CCD, CMOS, etc., a frame memory 16, and a control unit 18 that controls the imaging unit 14 and the frame memory 16 to configure an electronic shutter. The frame memory 16 includes a DRAM, etc., and stores the image signal from the imaging unit 14 for each frame.

[0015] Camera 12 has at least one of a rolling shutter and a global shutter as an electronic shutter. Alternatively, camera 12 may have both a rolling shutter and a global shutter, and the rolling shutter and global shutter may be switched between.

[0016] The strobe device 10 may be integrated into the camera 12 or be a separate unit from the camera 12, and in either case, it is connected to the camera 12 in a way that allows for bidirectional communication. Communication between the strobe device 10 and the camera 12 may be performed by wire or wireless means.

[0017] When the strobe device 10 is connected to the camera 12, the camera 12 outputs a shutter identification signal to the strobe device 10 that identifies whether the operating electronic shutter is a rolling shutter or a global shutter. The output of the shutter identification signal may be done by plugging it in.

[0018] The strobe device 10 includes a xenon discharge tube 20, a battery unit 30, and a high-voltage power supply unit 32.

[0019] The xenon discharge tube 20 is a flash discharge tube, and includes an elongated tubular glass tube 22, a pair of discharge electrodes 24 and 26 formed by an anode and a cathode provided at both longitudinal ends of the glass tube 22, and a trigger electrode 28 provided outside the middle portion of the glass tube 22.

[0020] The battery unit 30 includes a rechargeable battery 31 that is a DC power source. The high-voltage power supply unit 32 includes a boost transformer 34 including a low-voltage side connected to the battery unit 30 and a switching element 36 formed by a field-effect transistor, capacitors 38 and 40 connected in parallel to the battery unit 30, and protection resistors 42 and 44, and generates a required DC high voltage on the high-voltage output side of the boost transformer 34. The switching element 36 controls the on-time (on period) of the boost transformer 34 to control the capacitance of a main capacitor 48 described later.

[0021] The high-voltage output side of the high-voltage power supply unit 32 is connected to the main capacitor 48 via a diode 46. The main capacitor 48 is a large-capacity capacitor and accumulates the charge of the DC high voltage output by the high-voltage power supply unit 32. That is, the main capacitor 48 is charged by the high-voltage power supply unit 32 over the on-time of the switching element 36.

[0022] The positive side of the main capacitor 48 is connected to one discharge electrode 24 of the xenon discharge tube 20 via a choke coil 50 and a special parallel circuit 52 connected in series to the choke coil 50. The other discharge electrode 26 of the xenon discharge tube 20 is grounded via a diode 54 and a switching element 56 (IGBT) formed by an insulated gate bipolar transistor. Thereby, the discharge voltage of the high voltage due to the charge accumulated in the main capacitor 48 is applied to the pair of discharge electrodes 24 and 26. The switching element 56 (second switching element) controls the time (period) of voltage application to the xenon discharge tube 20.

[0023] A trigger circuit 60 is connected to the high-voltage output side of the high-voltage power supply unit 32 via a protective resistor 58. The trigger circuit 60 includes a step-up transformer 62, a capacitor 64, and a thyristor 66(Q) which is a trigger output switching element. The trigger circuit 60 applies a trigger voltage to the trigger electrode 28 of the xenon discharge tube 20 at the timing when the thyristor 66 turns on.

[0024] When a trigger voltage is applied to the trigger electrode 28, the xenon discharge tube 20 starts discharging due to the discharge voltage applied to the pair of discharge electrodes 24 and 26, generating a flash in the glass tube 22.

[0025] The special parallel circuit 52 is provided in the circuit connecting the discharge electrode 24 of the xenon discharge tube 20 and the main capacitor 48, and includes a resistor 68, a bypass circuit 69 that bypasses the resistor 68, and a thyristor 70 (first switching element) that opens and closes the bypass circuit 69. In other words, the special parallel circuit 52 includes a parallel circuit of the resistor 68 and the thyristor 70, and when the thyristor 70 is in the off state (non-conductive state), the bypass circuit 69 is opened, making the resistor 68 effective and connecting the discharge electrode 24 and the main capacitor 48 including the resistor 68. When the thyristor 70 is in the on state (conductive state), the bypass circuit 69 is closed, making the resistor 68 ineffective and connecting the discharge electrode 24 and the main capacitor 48 without including the resistor 68. The special parallel circuit 52 is connected to ground via a capacitor 73.

[0026] The resistance value of resistor 68 is greater than the resistance value of the bypass circuit 69 including thyristor 70, and is set according to the number of pixels of the imaging unit 14 in the rolling shutter of camera 12, the reading performance of the image signal from the imaging unit 14 to the frame memory 16, etc.

[0027] The control device 80 is an electronically controlled device including a microcomputer, and has a signal input unit 82 and a signal output unit 84. The signal input unit 82 is connected to a manually operated shutter mode switch 86 and a camera 12 provided on the strobe device 10. The shutter mode switch 86 is operated by the user and outputs a shutter identification signal to the signal input unit 82 that identifies whether the user setting is a rolling shutter or a global shutter.

[0028] The control device 80 sets the strobe device 10 to rolling shutter mode or global shutter mode according to the shutter identification signal from the shutter mode switcher 86 or camera 12 input to the signal input unit 82. The setting of the shutter mode by the shutter mode switcher 86 or the shutter identification signal from camera 12 may be performed according to the latest shutter identification signal input to the signal input unit 82, or according to the shutter identification signal from camera 12 via plug-in.

[0029] The signal output unit 84 is connected to the gate terminals of the switching elements 36, 56 and the thyristors 66, 70 via protective resistors 42, 57, 67, and 71. As a result, the switching elements 56, 36 and the thyristors 66, 70 are individually controlled on and off by the control device 80.

[0030] It should be noted that the control device 80, based on the output signal of the signal output unit 84, turns on the thyristor 70 when in global shutter mode and turns off the thyristor 70 when in rolling shutter mode.

[0031] As a result, in global shutter mode, the thyristor 70 is ON, effectively disabling the resistor 68, and the discharge electrode 24 and the main capacitor 48 are connected by the thyristor 70 without the resistor 68. In other words, in global shutter mode, the main capacitor 48 and the xenon discharge tube 20 are connected without the resistor 68 in between.

[0032] In this case, as shown in Figure 2(A), when the thyristor 66(Q) turns on at time T1, the thyristor 70(SCR) and the second switching element 56 simultaneously turn on for a first predetermined time Tg until time T2. As a result, the voltage applied to the discharge electrodes 24 and 26 by the accumulated charge of the main capacitor 48 is performed for a relatively short first predetermined time Tg without being affected by the resistor 68, and the xenon discharge tube 20 flashes for a relatively short first predetermined time Tg, as shown by line G in Figure 3. As a result, the strobe device 10 functions effectively as a light source suitable for a global shutter.

[0033] In a global shutter, a suitable charging voltage for the strobe device 10 is an ultra-high voltage of about 1000V, and a suitable pulse emission may be an ultra-short pulse emission of about 100μsec.

[0034] In rolling shutter mode, the thyristor 70 is in the off state, so the resistor 68 becomes active and the discharge electrode 24 and the main capacitor 48 are connected, including the resistor 68. In other words, in rolling shutter mode, the main capacitor 48 and the xenon discharge tube 20 are connected with the resistor 68 in between.

[0035] In this case, as shown in Figure 2(B), the thyristor 70 (SCR) remains in the off state, and when the thyristor (Q) turns on at time T1, the second switching element 56 simultaneously turns on for a relatively long second predetermined time Tr until time T3. As a result, the voltage applied to the discharge electrodes 24 and 26 by the accumulated charge of the main capacitor 48 is carried out for a relatively long second predetermined time Tr under the action of the resistor 68, and the xenon discharge tube 20 flashes for a relatively long second predetermined time Tr, as shown by the line R in Figure 3. As a result, the strobe device 10 functions effectively as a light source suitable for rolling shutter.

[0036] When the exposure conditions are the same for both rolling shutter and global shutter photography, the area (light intensity) of the region defined inside line G in Figure 3 and the area (light intensity) of the region defined inside line R will be the same.

[0037] In this way, the strobe device 10 can effectively function as a light source for both a rolling shutter camera 12 and a global shutter camera 12, and can be used interchangeably with both a rolling shutter camera 12 and a global shutter camera 12.

[0038] Although the present invention has been described above in terms of preferred embodiments, it will be easily understood by those skilled in the art that the present invention is not limited to these embodiments. For example, the switching element in the special parallel circuit 52 is not limited to the thyristor 70, but may be a switching transistor such as a power transistor. The strobe device 10 can be used in both consumer digital cameras and industrial cameras used in measuring devices, inspection devices, etc.

[0039] The above embodiments may also be described as follows:

[0040] In one embodiment, the switching element of the bypass circuit 69 may include a thyristor 70 provided in the bypass circuit 69.

[0041] Furthermore, one embodiment includes a switching element 56 (second switching element) provided in a circuit connecting a pair of discharge electrodes 24, 26 and a main capacitor 48, and the control device 80 controls the conduction time of the switching element 56 so as to turn off the switching element 56 for a first predetermined time Tg when the identification signal of the electronic shutter indicates a global shutter, and turn on the switching element 56 for a second predetermined time Tr which is longer than the first predetermined time Tg when the identification signal of the electronic shutter indicates a rolling shutter.

[0042] Furthermore, not all of the components shown in the above embodiments are necessarily essential, and they can be appropriately selected and omitted as long as they do not deviate from the spirit of the present invention. [Explanation of symbols]

[0043] 10: Strobe device 12: Electronic shutter camera (camera) 14: Imaging Unit 16: Frame memory 18: Control Unit 20: Xenon discharge tube 22: Glass tube 24:Discharge electrode 26:Discharge electrode 28: Trigger electrode 30: Battery section 31: Battery 32: High-voltage power supply unit 34: Step-up transformer 36: Switching element 38: Capacitor 40: Capacitor 42:Protection resistor 44:Protection resistor 46: Diode 48: Main capacitor 50: Choke coil 52:Special parallel circuit 54: Diode 56: Second switching element (switching element) 57:Protection resistor 58:Protection resistor 60: Trigger Circuit 62: Step-up transformer 66: Thyristor (switching element for trigger output) 67:Protection resistor 68:Resistor 69: Bypass Circuit 70: Thyristor (switching element) 71:Protection resistor 73: Capacitor 80: Control device 82: Signal input section 84: Signal output section 86: Shutter mode switch

Claims

1. A flash discharge tube comprising a pair of discharge electrodes and a trigger electrode, A high-voltage power supply unit that generates DC high voltage, A main capacitor that stores the DC high voltage charge output by the high-voltage power supply unit and applies the discharge voltage to the pair of discharge electrodes, A strobe device having a trigger circuit that generates a trigger voltage to be applied to the trigger electrode, A resistor is provided in the circuit connecting the pair of discharge electrodes and the main capacitor, A bypass circuit that bypasses the resistor, A switching element that opens and closes the bypass circuit, It includes a control device that controls the opening and closing of the switching element, The control device has a signal input section that inputs a shutter identification signal to identify whether the camera connected to the strobe device is a rolling shutter or a global shutter, and controls the switching element to turn off when the shutter identification signal indicates a rolling shutter, and to turn on when the shutter identification signal indicates a global shutter.

2. The strobe device according to claim 1, wherein the switching element includes a thyristor provided in the bypass circuit.

3. The circuit connecting the pair of discharge electrodes and the main capacitor includes a second switching element, The strobe device according to claim 1 or 2, wherein the control device turns on the second switching element for a first predetermined time when the shutter identification signal indicates a global shutter, and controls the conduction time of the second switching element to turn on the second switching element for a second predetermined time longer than the first predetermined time when the shutter identification signal indicates a rolling shutter.

4. A camera with an electronic shutter, A flash discharge tube comprising a pair of discharge electrodes and a trigger electrode; a high-voltage power supply unit that generates a DC high voltage; a main capacitor that stores the charge of the DC high voltage output by the high-voltage power supply unit and applies the discharge voltage to the discharge electrodes; a trigger circuit that generates a trigger voltage to be applied to the trigger electrode; a resistor provided in the circuit connecting the pair of discharge electrodes and the main capacitor; a bypass circuit that bypasses the resistor; and a switching element that opens and closes the bypass circuit; and a strobe device connected to the camera. A camera system in which the strobe device turns off the switching element when the electronic shutter of the camera is a rolling shutter, and turns on the switching element when the electronic shutter of the camera is a global shutter.

5. A method for controlling a light source for a camera having an electronic shutter, Using a flash discharge tube connected to the main capacitor as the light source, If the electronic shutter of the camera is a rolling shutter, the main capacitor and the flash discharge tube are connected with a resistor in between. A light source control method in which, when the electronic shutter of the camera is a global shutter, the main capacitor and the flash discharge tube are connected without the resistor in between.

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