Inspection light irradiation system and drive control device

Abstract

To enable stable and fast light emission from a light irradiation device in a light irradiation system for inspection, regardless of the cable length between a power supply device and the light irradiation device.SOLUTION: The present invention comprises: a light irradiation device 1 equipped with a light source body 12 for emitting light for inspection; a power supply device 2 for supplying a current to the light source body 12; an intermediate device 3 equipped with a current supply line 39 for relaying the current supplied from the power supply device to the light source body 12 and a switching element 33 for turning supply of the current on and off. The power supply device 2 is provided with a control circuit 23 for outputting a control signal to the switching element, and a differential driver 24 for differentially transmitting the control signal output from the control circuit 23. The intermediate device 3 is provided with a capacitor 32 for auxiliary current supply which is installed on the current supply line 39, and a differential receiver 34 for receiving the differentially transmitted control signal and outputting to the switching element 33.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a light irradiation system used for inspections such as surface inspection and mark reading of a workpiece. [Background technology]

[0002] As shown in Patent Document 1, a conventional light irradiation system used for this type of workpiece inspection consists of two devices: a light irradiation device that uses an LED as a light source, and a power supply device that supplies current to the LED of this light irradiation device through a power supply cable, causing it to emit light.

[0003] This power supply device has, within its housing, a DC power supply that supplies current to the LED, a switching element such as an FET that turns the current supply to the LED on and off, and a control circuit that controls this switching element.

[0004] The LED can be made to emit light in a strobe mode (single light emission mode) or a PWM mode (continuous pulse light emission mode) by turning the switching element on and off at high speed.

[0005] However, if the power supply cable connecting the light irradiation device and the power supply device becomes quite long (for example, 5 m or longer) due to reasons such as placement restrictions at the user's site, the stray capacitance and parasitic inductance of the cable will cause delays and noise in the high-speed ON / OFF control of the LED, resulting in problems such as the LED not emitting light at the expected brightness.

[0006] Therefore, the applicant conceived the idea of ​​accommodating the tank capacitor and switching element for supplying auxiliary current, which were previously located in the power supply device, in an intermediate device that can be placed near the light irradiation device, thereby shortening the actual length of the power supply cable, reducing the delay and noise, and enabling high-speed light emission. [Patent Document 1] Japanese Patent Application Publication No. 2017-033736 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0007] However, the inventors discovered that this still did not result in sufficient improvement, and traced the cause to the transmission of the ON / OFF control signal from the control circuit to the switching element via the control cable. Specifically, as the control cable transmitting this ON / OFF control signal became longer, significant noise and delays occurred in the control signal, causing problems with the operation of the switching element.

[0008] The present invention was made only after identifying the above-mentioned causes, and aims to provide an inspection light irradiation system that enables stable, high-speed light emission from the light irradiation device regardless of the distance between the power supply device and the light irradiation device or the length of the cable between them. [Means for solving the problem]

[0009] That is, the inspection light irradiation system according to the present invention includes a light irradiation device having an LED or laser as a light source body that emits inspection light, a power supply device that supplies current to the light source body, and an intermediate device that includes a current supply line that relays the current supplied from the power supply device to the light source body and a switching element that turns the current on and off, the power supply device is provided with a control circuit that outputs a control signal to the switching element, and a differential driver that differentially transmits the control signal output from the control circuit, The intermediate device is characterized by having an auxiliary current supply capacitor provided on the current supply line and a differential receiver that receives the differentially transmitted control signal and outputs it to the switching element.

[0010] In this case, the intermediate device only needs to include small elements such as an auxiliary current supply capacitor and a switching element, which allows for miniaturization and placement of the intermediate device near the light irradiation device, thereby substantially shortening the power supply path from the auxiliary current supply capacitor to the light source, thereby reducing delays and noise.

[0011] On the other hand, the power supply device and the intermediate device may be located far apart, which may result in a long transmission path for the control signal from the control circuit to the switching element. However, even in this case, since the control signal is transmitted differentially, it is possible to improve noise resistance and prevent delays in the control signal, allowing the switching element to operate at high speed.

[0012] In this way, the effects of delay and noise can be significantly reduced compared to conventional methods in both the power supply path and the control signal transmission path, enabling stable, high-speed light emission from the light irradiation device regardless of the relative positions of the power supply device and the light irradiation device.

[0013] If low-voltage differential transmission is used to transmit the ON / OFF control signal, the control signal can be transmitted more reliably at high speed.

[0014] As an embodiment in which the effect of the present invention is remarkable, it is preferable that the intermediate device is arranged closer to the light irradiation device than the power supply device. Similarly, when the control signal is a pulse signal for causing the light source to emit a strobe light, the effect of the present invention is more pronounced. [Effects of the Invention]

[0015] According to the present invention, stable high-speed light emission by the light irradiation device can be achieved regardless of the distance between the power supply device and the light irradiation device or the length of the cable therebetween. [Brief explanation of the drawings]

[0016] [Figure 1]1 is a schematic electrical circuit diagram showing the overall configuration of an inspection light irradiation system according to an embodiment of the present invention. [Figure 2] 10 is experimental data showing the delay and noise suppression effect of the inspection light irradiation system in the embodiment. [Figure 3] FIG. 10 is a schematic electrical circuit diagram showing the overall configuration of an inspection light irradiation system according to another embodiment of the present invention. [Figure 4] FIG. 10 is a schematic electrical circuit diagram showing a connection between an intermediate device and a light irradiation device in still another embodiment of the present invention. [Figure 5] FIG. 10 is a schematic electrical circuit diagram showing a connection between an intermediate device and a light irradiation device in still another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] An embodiment of the present invention will be described below with reference to the drawings.

[0018] 1, the inspection light irradiation system 100 according to this embodiment includes a light irradiation device 1 that emits inspection light used for surface inspection of various workpieces, a power supply device 2 that supplies current to the light irradiation device 1, an intermediate device 3 that is interposed between the power supply device 2 and the light irradiation device 1, and an electric cable that connects them. The power supply device 2 and the intermediate device 3 constitute a drive control device as referred to in the claims. Each part will be explained.

[0019] The light irradiation device 1 includes an LED circuit 1A in which LEDs 12 serving as light sources are connected in series or parallel, and a first housing 11 that holds the LED circuit 1A. There are various types of light irradiation devices 1 depending on the purpose of the inspection, such as a line type in which the LEDs 12 are arranged in a straight line, a ring type in which the LEDs 12 are arranged in a circular ring, and a surface-emitting type in which the LEDs 12 are arranged in a plane. The first housing 11 is provided with a positive terminal 13 that supplies current to the LED circuit 1A and a negative terminal 14 that returns the current that has flowed through the LED circuit 1A to ground.

[0020] The power supply device 2 includes a DC constant voltage power supply 22, a control circuit 23, a differential driver 24, and a second housing 21 that houses the DC constant voltage power supply 22, the control circuit 23, and the differential driver 24.

[0021] The DC constant voltage power supply 22 supplies current to the LED 12, and in this case is a DC / DC converter connected to an AC / DC converter (not shown) that is connected to a commercial power source and converts alternating current into direct current.

[0022] The control circuit 23 outputs a control signal for controlling the current supplied from the DC constant voltage power supply 22 to the LED 12, and is configured using, for example, an FPGA. The control signal is a single pulse signal or a continuous pulse signal that takes two values, ON / OFF, and causes the LED 12 to emit light in strobe mode or PWM mode based on the waveform of this control signal. The rise timing and pulse width of this control signal can be set by an operation panel provided on the second housing 21 or by external communication.

[0023] The differential driver 24 converts the control signal, which is a single-ended signal output from the control circuit 23, into two mutually inverted signals (P signal and N signal) and transmits them at a low voltage differential, and is mainly composed of, for example, an H-bridge circuit.

[0024] The second housing 21 is separate from the first housing 11 and has, for example, a rectangular parallelepiped shape, and its outer surface is provided with a current output terminal 25 to which the output terminal of the DC constant voltage power supply 22 is connected, and a control signal transmission terminal 26 to which the output terminal of the differential driver 24 is connected.

[0025] The intermediate device 3 includes a current supply line 39, a switching element 33, a differential receiver 34, an auxiliary current supply capacitor 32, and a third housing 31 that houses the current supply line 39, the switching element 33, the differential receiver 34, and the auxiliary current supply capacitor 32. Note that reference numeral 9 (shown in FIG. 1) provided between the switching element 33 of the intermediate device 3 and ground is a resistive element for limiting current. The current supply line 39 relays the current supplied from the DC constant voltage power supply 22 to the LED 12 .

[0026] The switching element 33 is, for example, an FET that turns on / off the current supplied from the DC constant voltage power supply 22 to the LED 12 in accordance with a control signal output from the control circuit 23. Specifically, the cathode side of the LED circuit 1A is connected to the drain terminal of this switching element 33, and the ground is connected to the source terminal via a current limiting resistor 9. When the control signal is input to the gate terminal, the current supplied from the DC constant voltage power supply 22 to the LED 12 is turned on / off in accordance with the control signal. The switching element 33 is not limited to an FET and can be configured, for example, by a transistor.

[0027] The differential receiver 34 is configured using a comparator or the like, receives the control signal differentially transmitted from the differential driver 24, converts it into a single-ended signal, and outputs it to the input terminal of the switching element 33. Specifically, the P signal and N signal from the differential driver 24 are input to the plus input terminal and minus input terminal of the differential receiver 34, respectively, and the single-ended control signal is output from the output terminal.

[0028] The auxiliary current supply capacitor 32 supplies auxiliary current when lighting the LED 12, and functions as an accumulator to guarantee the inrush current and to prevent a momentary drop in the output voltage of the DC / DC converter 22. Here, for example, an electrolytic capacitor is used as this capacitor 32, and its capacitance is set to 1000 μF to 3000 μF.

[0029] The third housing 31 is separate from the first housing 11 and the second housing 21 and has, for example, a rectangular parallelepiped shape, and its outer surface is provided with a current relay input terminal 35 connected to one end of the current supply line 39, a current relay output terminal 36 connected to the other end, a current control terminal 37 connected to the drain terminal of the switching element 33, and a current control terminal 38 connected to the positive input terminal and negative input terminal of the differential receiver 34. The power supply device 2, the light irradiation device 1, and the intermediate device 3 are connected by an electric cable as described below.

[0030] As the electric cable, two types are prepared: a current cable through which current supplied to the LED 12 flows, and a control cable C2 through which a control signal for controlling the current is transmitted.

[0031] The current cables include a first current cable C11 connecting the current output terminal 25 of the power supply device 2 and the current relay input terminal 35 of the intermediate device 3, a second current cable C12 connecting the current relay output terminal 36 of the intermediate device 3 and the positive terminal 13 of the light irradiation device 1, and a third current cable C13 connecting the negative terminal 14 of the light irradiation device 1 and the current control terminal 37 of the intermediate device 3. The control cable C2 is a two-wire cable that connects the control signal transmission terminal 26 of the power supply device 2 and the current control terminal 38 of the intermediate device 3.

[0032] However, with such a structure, the intermediate device 3 only needs to be equipped with small elements such as the auxiliary current supply capacitor 32 and the switching element 33, making it possible to miniaturize the device and place the intermediate device 3 near the light irradiation device 1.

[0033] As a result, as shown by the arrow in Figure 1, it is possible to shorten the current supply path that flows from the auxiliary current supply capacitor 32 through the LED circuit 1A to ground, significantly reducing the delay and noise that occurs here.

[0034] On the other hand, if the power supply device 2 and the intermediate device 3 are located far apart, the transmission path of the control signal from the control circuit 23 to the switching element 33 may become long. However, even in this case, since low voltage differential signaling (LVDS) is used to transmit the control signal, high speed transmission of the control signal and improved noise resistance can be achieved, allowing the switching element 33 to operate stably at high speed.

[0035] In this way, the effects of delay and noise can be significantly reduced compared to conventional methods in both the power supply path and the control signal transmission path, enabling stable, high-speed light emission from the light irradiation device 1 regardless of the relative positions of the power supply device 2 and the light irradiation device 1. An example of this is shown in Figure 2, which shows that light emission delay has been significantly improved. The present invention is not limited to the above-described embodiment.

[0036] For example, in the above embodiment, the power supply device 2, the light irradiation device 1, and the intermediate device 3 are each provided with separate housings, but as shown in Fig. 3, the light irradiation device 1 and the intermediate device 3 may share housings 11 and 31. This can further reduce delays and noise in the current supply path. The resistive element 9 may be provided anywhere in the current path from the DC constant voltage power supply 22 through the LED circuit 1A and the switching element 33 to the ground. For example, as shown in FIG. 4, the resistive element 9 may be provided between the LED circuit 1A and the negative terminal 14 of the light irradiation device 1. The switching element 33 may be provided on a current supply line 39 as shown in FIG. The light source may be a laser as well as an LED.

[0037] Furthermore, the present invention is not limited to the above-described embodiments and modifications, and various modifications are possible within the scope of the spirit thereof, such as appropriately combining the respective configurations. [Explanation of symbols]

[0038] 100···Inspection light irradiation system 1...Light irradiation device 12...LED (light source) 2...Power supply device 22 DC constant voltage power supply 23 Control circuit 24 Differential driver 3...Intermediate device 32 Auxiliary current supply capacitor 33. Switching element 34 Differential Receiver 39. Current supply line

Claims

1. a light irradiation device including an LED or a laser as a light source for emitting light for inspection; a power supply device for supplying current to the light source; a current supply line that relays the current supplied from the power supply device to the light source body, and an intermediate device that includes a switching element that turns on / off the supply of the current, the light irradiation device, the power supply device, and the intermediate device are each housed in a separate housing, the power supply device is provided with a control circuit that outputs a control signal to the switching element, and a differential driver that differentially transmits the control signal output from the control circuit, The intermediate device is characterized in that it is provided with an auxiliary current supply capacitor provided on the current supply line and a differential receiver that receives the differentially transmitted control signal and outputs it to the switching element.

2. 2. The inspection light irradiation system according to claim 1, wherein the differential transmission is a low-voltage differential transmission.

3. 3. The light irradiation system for inspection according to claim 1, wherein the intermediate device is disposed closer to the light irradiation device than the power supply device.

4. 4. The inspection light irradiation system according to claim 1, wherein the control signal is a pulse signal for causing the light source to emit a strobe light.

5. A drive control device that drives and controls a light irradiation device having an LED or a laser as a light source that emits light for inspection, a power supply device for supplying current to the light source; a current supply line that relays the current supplied from the power supply device to the light source body, and an intermediate device that includes a switching element that turns on / off the supply of the current, the light irradiation device, the power supply device, and the intermediate device are each housed in a separate housing, the power supply device is provided with a control circuit that outputs a control signal to the switching element, and a differential driver that differentially transmits the control signal output from the control circuit, A drive control device characterized in that the intermediate device is provided with an auxiliary current supply capacitor provided on the current supply line and a differential receiver that receives the differentially transmitted control signal and outputs it to the switching element.

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