Laser projector and laser transmission cable thereof

Abstract

To provide a laser transmission cable.SOLUTION: A laser transmission cable includes: at least one first optical fiber that receives laser light from a laser light source and transmits it; a second optical fiber that is arranged in parallel to the first optical fiber and has opposing first and second ends; an optical signal transmitting device that is provided at the first end of the second optical fiber and arranged to input a monitor signal to the second optical fiber; and an optical signal receiving unit that is provided at the second end of the second optical fiber and arranged to receive the monitor signal and that is coupled to a switch provided in a power supply circuit connected to the laser light source, and arranged to turn off the switch when the monitor signal is not received.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a laser projector and a laser transmission cable therefor. [Background technology]

[0002] Optical fibers can be used for laser transmission, but they are easily damaged and can break, for example, if they are bent too frequently or too frequently. When an optical fiber is damaged, laser energy can leak from the damaged area, potentially heating surrounding objects and causing danger. Therefore, a mechanism for detecting damage to the optical fiber is necessary. Current industry practice is to use linear heat detection cables (LHDCs) for optical fiber damage detection. Linear heat detection cables have the characteristic of shorting out when the temperature reaches a certain upper limit. By detecting this short circuit, optical fiber damage can be identified. However, linear heat detection cables have many drawbacks, including (1) high cost, (2) difficulty in threading due to their large outer diameter and hard material, which may damage the optical fiber during threading, and (3) heavy weight due to their metal construction. Therefore, the development of new optical fiber damage detection technologies is needed. Summary of the Invention [Problem to be solved by the invention]

[0003] In view of this, one object of the present disclosure is to provide an improved laser projector and a laser transmission cable therefor in order to solve the above-mentioned problems of the prior art. [Means for solving the problem]

[0004] In order to achieve the above object, according to some embodiments of the present disclosure, a laser transmission cable includes at least one first optical fiber that receives and transmits laser light from a laser light source, a second optical fiber arranged in parallel to the first optical fiber and having opposing first and second ends, an optical signal transmitter provided at the first end of the second optical fiber and arranged to input a monitor signal to the second optical fiber, and an optical signal receiver provided at the second end of the second optical fiber and arranged to receive the monitor signal, coupled to a switch provided in a power supply circuit connecting the laser light source, and arranged to turn off the switch when the monitor signal is not received.

[0005] In one or more embodiments of the present disclosure, the first optical fiber is made of glass and the second optical fiber is made of plastic.

[0006] In one or more embodiments of the present disclosure, the laser transmission cable further includes a stopper coating over the first optical fiber and the second optical fiber.

[0007] In one or more embodiments of the present disclosure, the stopper coating has a heat resistance of at least 120°C.

[0008] In one or more embodiments of the present disclosure, the stopper coating has a smooth inner surface.

[0009] In one or more embodiments of the present disclosure, the laser transmission cable further includes a metal hose jacket over the stopper jacket.

[0010] In one or more embodiments of the present disclosure, an optical signal transmission device includes a pulse generator and an optical transmitter, wherein the pulse generator is configured to generate a pulse signal, and the optical transmitter is electrically connected to the pulse generator and configured to transmit a monitor signal based on the pulse signal.

[0011] In one or more embodiments of the present disclosure, the optical signal receiving device includes a pulse detector and an optical receiver, the optical receiver is arranged to generate an optical response signal, the pulse detector is electrically connected to the optical receiver and arranged to output a detection signal based on the optical response signal, the detection signal indicates whether the optical receiver has received a monitor signal, and a switch is coupled to the pulse detector and arranged to switch states based on the detection signal.

[0012] In one or more embodiments of the present disclosure, the laser transmission cable further includes a first connector including a first housing and a second connector including a second housing, wherein opposing ends of the first optical fiber are covered by the first and second housings, respectively; the optical signal transmitting device includes a first circuit board assembly provided in the first housing, wherein the first circuit board assembly includes the first circuit board and a pulse generator and an optical transmitter provided on the first circuit board; and the optical signal receiving device includes a second circuit board assembly provided in the second housing, wherein the second circuit board assembly includes the second circuit board and a pulse detector and an optical receiver provided on the second circuit board.

[0013] According to some embodiments of the present disclosure, a laser projector includes a first connector, a second connector, a light source system, a video distribution unit, and the above-mentioned laser transmission cable. Opposing ends of a first optical fiber are covered by the first connector and the second connector, respectively, and an optical signal transmitter and an optical signal receiver are provided in the first connector and the second connector, respectively. The light source system includes a laser light source and a switch, and is connected to the second connector. The video distribution unit is connected to the light source system via the laser transmission cable and the first connector. (Effects of the Invention)

[0014] In summary, the laser transmission cable of the present disclosure includes one or more optical fibers for transmitting laser light and an additional optical fiber for transmitting a monitor signal, arranged in parallel. If the optical fiber for transmitting the laser light is damaged, laser energy will leak out from the damaged area, burning the optical fiber transmitting the monitor signal and causing an interruption in transmission of the monitor signal. In this case, the optical signal receiving device for receiving the monitor signal detects the interruption in transmission of the monitor signal and turns off a switch provided in the power circuit of the laser light source, thereby automatically turning off the laser light source and avoiding any danger. In some embodiments, the optical fiber for transmitting the monitor signal can be a plastic optical fiber. Plastic optical fiber is lightweight, flexible, resistant to low temperatures, and inexpensive, making the production and use of the laser transmission cable more convenient and reducing the production cost of the laser transmission cable. [Brief explanation of the drawings]

[0015] To make the above and other objects, features, advantages and embodiments of the present disclosure more clearly comprehensible, the description of the accompanying drawings is as follows: [Figure 1] FIG. 1 is a schematic diagram illustrating a laser projector according to an embodiment of the present disclosure. [Figure 2] 2 is an enlarged view showing a laser transmission cable of the laser projector shown in FIG. 1. [Figure 3] FIG. 2 is a functional block diagram showing the laser projector shown in FIG. [Figure 4] 3 is an exploded view showing a first connector of the laser transmission cable shown in FIG. 2. [Figure 5] 3 is an exploded view showing a second connector of the laser transmission cable shown in FIG. 2. [Figure 6] FIG. 10 is a schematic plan view illustrating a laser transmission cable according to another embodiment of the present disclosure. [Figure 7] 7 is a schematic cross-sectional view showing the portion marked by line segment 7-7' of the laser transmission cable shown in FIG. 6. FIG. [Figure 8] FIG. 10 is a schematic plan view illustrating a laser transmission cable according to another embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present disclosure can be more fully described by reference to the accompanying drawings and various embodiments described below. The elements in the drawings are not drawn to scale and are provided merely to explain the present disclosure. Many practical details described below are for the purpose of providing a thorough understanding of the present disclosure, and those skilled in the art will understand that the present disclosure can be practiced without one or more of the practical details. Therefore, these details should not be construed as limiting the present disclosure.

[0017] Please refer to FIG. 1. FIG. 1 is a schematic diagram illustrating a laser projector 12 according to an embodiment of the present disclosure. The laser projector 12 includes at least one light source system 21, at least one image distribution unit 22 (also referred to as a projection head), and at least one laser transmission cable 30. The laser projector 12 adopts a design in which the light source system 21 and the image distribution unit 22 are separated and connected to each other via the laser transmission cable 30. Specifically, the light source system 21 is arranged to provide laser light, and the image distribution unit 22 is movably connected to the light source system 21 via the laser transmission cable 30 and arranged to project an image using the laser light supplied from the light source system 21. The laser transmission cable 30 is arranged to transmit the laser light supplied from the light source system 21 to the image distribution unit 22. The laser transmission cable 30 is a flexible cable that allows the image distribution unit 22 to be positioned appropriately for easy projection.

[0018] 1, the laser transmission cable 30 includes a first connector 31 and a second connector 32, which are provided at opposite ends of the laser transmission cable 30, respectively, and are arranged to connect the video distribution unit 22 and the light source system 21, respectively. For example, the video distribution unit 22 and the light source system 21 may have slots for connecting the laser transmission cable 30, and the first connector 31 and the second connector 32 may be inserted into the slots of the video distribution unit 22 and the light source system 21, respectively.

[0019] 1, the light source system 21 includes a laser light source 23, which is configured to generate laser light and input the generated laser light into the laser transmission cable 30 via the second connector 32. Specifically, the laser light source 23 is configured to generate high-energy laser light that projects an image. The laser transmission cable 30 may include one or more optical fibers for transmitting the laser light, and the optical fibers of the laser transmission cable 30 will be described in detail later.

[0020] 1, the light source system 21 is connected to a power supply 90 arranged to power the laser light source 23 or other power-consuming components. In some embodiments, the laser light source 23 includes at least one laser diode. In some embodiments, the light source system 21 may further include one or more optical elements (not shown, including, for example, lenses, mirrors, spectroscopic elements, etc.) for directing laser light generated from the laser light source 23 to the laser transmission cable 30.

[0021] 1 , the light source system 21 and the image distribution unit 22 are arranged in a one-to-one relationship, i.e., a single light source system 21 provides laser light to a single image distribution unit 22. However, the laser projector is not limited to adopting a one-to-one relationship. For example, the light source system 21 and the image distribution unit 22 may be arranged in a one-to-many relationship, i.e., a single light source system 21 provides laser light to multiple image distribution units 22. Alternatively, the light source system 21 and the image distribution unit 22 may be arranged in a many-to-one relationship, i.e., multiple light source systems 21 provide laser light to a single image distribution unit 22.

[0022] Please refer to Figure 2. Figure 2 is an enlarged view showing the laser transmission cable 30 of the laser projector shown in Figure 1, with the internal structure indicated by dashed lines. Specifically, the laser transmission cable 30 includes at least one first optical fiber 51, which extends from a first connector 31 to a second connector 32, and both ends of the first optical fiber 51 are covered by the first connector 31 and the second connector 32, respectively. The first optical fiber 51 is positioned to receive and transmit laser light from the laser light source 23 (see Figure 1) of the light source system 21. In some embodiments, the laser transmission cable 30 includes a plurality of first optical fibers 51, and ends of the plurality of first optical fibers 51 can be fused to each other to form an optical fiber bundle.

[0023] 2, the laser transmission cable 30 further includes at least one second optical fiber 52, which extends from the first connector 31 to the second connector 32 and is arranged in parallel with the first optical fiber 51. The second optical fiber 52 may be provided on one side of the first optical fiber 51, or, if the laser transmission cable 30 includes multiple first optical fibers 51 to form an optical fiber bundle, the second optical fiber 52 may be provided on one side of the optical fiber bundle or within the optical fiber bundle.

[0024] As shown in FIG. 2, in some embodiments, the laser transmission cable 30 further includes a metal hose jacket 35 that is placed over the first optical fiber 51 and the second optical fiber 52 to provide protection for the first optical fiber 51 and the second optical fiber 52.

[0025] Please also refer to Figure 3, which is a functional block diagram of the laser projector 12 shown in Figure 1. As shown in Figures 2 and 3, the light source system 21 further includes a power supply circuit 28 and a switch 29. The power supply circuit 28 connects the laser light source 23 and a power supply 90, and the power supply 90 may supply power to the laser light source 23 via the power supply circuit 28. The switch 29 is provided in the power supply circuit 28 and can be switched between a blocking state and a pass state. When the switch 29 is in the blocking state, the power supply 90 does not supply power to the laser light source 23, and when the switch 29 is in the pass state, the power supply 90 is configured to supply power to the laser light source 23.

[0026] 2 and 3, the laser transmission cable 30 further includes an optical signal transmitting device 60 and an optical signal receiving device 70. The second optical fiber 52 has opposing first and second ends 53 and 54, and the optical signal transmitting device 60 and the optical signal receiving device 70 are provided at the first and second ends 53 and 54 of the second optical fiber 52, respectively. The optical signal transmitting device 60 is configured to input a monitor signal 96 (indicated by an arrow) into the second optical fiber 52. The monitor signal 96 is an optical signal that is configured to be transmitted through the second optical fiber 52 and received by the optical signal receiving device 70 when the monitor signal 96 is transmitted to the second end 54. The optical signal receiving device 70 is coupled to the switch 29 and configured to turn off the switch 29 when the monitor signal 96 is not received.

[0027] With the above arrangement, if the first optical fiber 51 for transmitting the laser light 97 (indicated by the arrow) is damaged, laser energy will leak from the damaged area and burn out the second optical fiber 52 located next to the first optical fiber 51 for transmitting the monitor signal 96, causing an interruption in the transmission of the monitor signal 96. In this case, the optical signal receiving device 70 detects that the transmission of the monitor signal 96 has been interrupted and turns off the switch 29 provided in the power supply circuit 28 of the laser light source 23, thereby automatically powering down the laser light source 23 and avoiding any danger.

[0028] 2 and 3 , in some embodiments, the optical signal transmitting device 60 and the optical signal receiving device 70 are provided in the first connector 31 and the second connector 32, respectively. When the second connector 32 is connected to the light source system 21, the optical signal receiving device 70 provided in the second connector 32 is coupled to the switch 29 of the light source system 21 (e.g., electrically connected to a corresponding electrical contact provided in a slot of the light source system 21 via an electrical contact provided in the second connector 32), and the optical signal receiving device 70 contributes to switching the switch 29 to a blocking state at an appropriate time. Note that when the second connector 32 is connected to the light source system 21, the power source 90 may supply power to the optical signal receiving device 70.

[0029] In some embodiments, the first optical fiber 51 is made of glass. In some embodiments, the first optical fiber 51 includes a glass optical fiber. In some embodiments, the second optical fiber 52 is made of plastic. In some embodiments, the second optical fiber 52 includes a plastic optical fiber. Compared to the LHDC used in currently commercially available cables, the plastic optical fiber has the following advantages: (1) it is inexpensive, costing approximately one-seventh the cost of the LHDC; (2) it is relatively flexible and easy to bend, which makes it less likely to damage the first optical fiber 51 during threading (e.g., threading the plastic optical fiber through the metal hose jacket 35), thereby improving production yield; and (3) it is lightweight, weighing approximately one-fifth the weight of the LHDC. However, the second optical fiber 52 is not limited to a plastic optical fiber and may include a glass optical fiber in other embodiments.

[0030] 2 and 3, in some embodiments, the optical signal transmission device 60 includes a pulse generator 63 and an optical transmitter 65. The pulse generator 63 is configured to generate a pulse signal (e.g., a pulsed current), and the optical transmitter 65 is electrically connected to the pulse generator 63 and configured to receive the pulse signal. The optical transmitter 65 is configured to transmit a monitor signal 96 based on the pulse signal. Thus, in this embodiment, the monitor signal 96 is a pulsed optical signal. In some embodiments, the optical transmitter 65 may include a light-emitting diode (LED) or a laser diode.

[0031] It should be noted that since the optical transmitter 65 is used only to transmit the monitor signal 96, the energy of the light from the optical transmitter 65 is less than the energy of the laser light 97 from the laser light source 23; in other words, the energy transmitted by the second optical fiber 52 is less than the energy transmitted by the first optical fiber 51.

[0032] As shown in FIGS. 2 and 3 , in some embodiments, the optical signal receiving device 70 includes a pulse detector 73 and an optical receiver 75. The optical receiver 75 is configured to generate an optical response signal in response to receiving light of a specific wavelength (e.g., light of the wavelength of the monitor signal 96). The pulse detector 73 is electrically connected to the optical receiver 75 and configured to receive the optical response signal. The pulse detector 73 is configured to output a detection signal based on the optical response signal, and the detection signal indicates whether the optical receiver 75 has received the monitor signal 96. The switch 29 is coupled to the pulse detector 73 and configured to switch its state based on the detection signal from the pulse detector 73. Specifically, if the detection signal indicates that the optical receiver 75 has received the monitor signal 96, the switch 29 is maintained in a pass state. Conversely, if the detection signal indicates that the optical receiver 75 has not received the monitor signal 96, the switch 29 is switched to a block state, and the laser light source 23 is powered off. In some embodiments, the optical receiver 75 may include a photodiode.

[0033] Please refer to Figure 4. Figure 4 is an exploded view showing the first connector 31 of the laser transmission cable 30 shown in Figure 2. In some embodiments, the optical signal transmission device 60 may actually function as a circuit board assembly and be attached to the first connector 31. In some embodiments, the first connector 31 includes a first housing 36, and the optical signal transmission device 60 includes a first circuit board assembly provided in the first housing 36, and the first circuit board assembly includes a first circuit board 67, and a pulse generator 63 and an optical transmitter 65 provided on the first circuit board 67. The pulse generator 63 and the optical transmitter 65 may be electrically connected to each other via conductive lines routed on or inside the first circuit board 67.

[0034] 4, the end of the first optical fiber 51 (only a portion of the segment is depicted) is covered by the first housing 36, i.e., the first optical fiber 51 extends inside the first housing 36 and passes through one side of the optical signal transmission device 60. The first optical fiber 51 is connected to the output port 33 of the first housing 36 and outputs laser light through the output port 33.

[0035] Please refer to Figure 5. Figure 5 is an exploded view showing the second connector 32 of the laser transmission cable 30 shown in Figure 2. In some embodiments, the optical signal receiving device 70 actually functions as a circuit board assembly and is attached to the second connector 32. In some embodiments, the second connector 32 includes a second housing 37, and the optical signal receiving device 70 includes a second circuit board assembly provided in the second housing 37, and the second circuit board assembly includes a second circuit board 77, a pulse detector 73 provided on the second circuit board 77, and an optical receiver 75. The pulse detector 73 and the optical receiver 75 may be electrically connected to each other via conductive lines routed on or inside the second circuit board 77.

[0036] 5, the end of the first optical fiber 51 (only a portion of the segment is depicted) is covered by the second housing 37, i.e., the first optical fiber 51 extends inside the second housing 37 and passes through one side of the optical signal receiving device 70. The first optical fiber 51 is connected to the input port 34 of the second housing 37 and receives laser light through the input port 34.

[0037] Please refer to Figures 6 and 7. Figure 6 is a schematic plan view showing a laser transmission cable 40 according to another embodiment of the present disclosure, with the internal structure indicated by dashed lines. Figure 7 is a schematic cross-sectional view showing the portion marked by line 7-7' of the laser transmission cable 40 shown in Figure 6. Compared with the above embodiment, the laser transmission cable 40 of this embodiment further includes a stopper coating 48, which covers the outside of the first optical fiber 51 and the second optical fiber 52. The stopper coating 48 has an internal passage 49, and the first optical fiber 51 and the second optical fiber 52 extend through the internal passage 49 of the stopper coating 48.

[0038] The stopper coating 48 has a function of limiting the distance between the first optical fiber 51 and the second optical fiber 52, ensuring that the first optical fiber 51 and the second optical fiber 52 are sufficiently close to each other, so that if the first optical fiber 51 for transmitting laser light is damaged, the second optical fiber 52 can be immediately burned out to activate a protection mechanism (i.e., a process of turning off the power to the laser light source 23). When the first optical fiber 51 and the second optical fiber 52 are covered by the stopper coating 48, the distance between the first optical fiber 51 and the second optical fiber 52 is limited so as not to exceed the diameter of the internal passage 49 of the stopper coating 48. The stopper coating 48 is flexible, which allows the laser transmission cable 40 to be easily bent.

[0039] In some embodiments, the stopper coating 48 has a heat resistance of at least 120°C (for example, the stopper coating 48 does not melt or burn at temperatures below 120°C). Thus, in addition to the function of limiting the position, the stopper coating 48 prevents laser energy leaking from the first optical fiber 51 from diffusing to the outside if the first optical fiber 51 is damaged, thereby preventing objects around the laser transmission cable 40 from heating up and causing burns to workers or burning and starting a fire. In some embodiments, the stopper coating 48 includes polytetrafluoroethylene (PTFE).

[0040] In some embodiments, the stopper coating 48 has a smooth inner surface coating with a low coefficient of friction, allowing the first optical fiber 51 and the second optical fiber 52 to be inserted smoothly through the stopper coating 48.

[0041] 6 and 7, in some embodiments, the laser transmission cable 40 further includes a metal hose jacket 35 that covers the outside of the stopper jacket 48, i.e., the stopper jacket 48 is located between the metal hose jacket 35 and the first optical fiber 51 and the second optical fiber 52. The metal hose jacket 35 can provide protection for the stopper jacket 48 to prevent abrasion of the stopper jacket 48.

[0042] Please refer to FIG. 8. FIG. 8 is a schematic plan view showing a laser transmission cable 80 according to another embodiment of the present disclosure, with the internal structure indicated by dashed lines. The laser transmission cable 80 of this embodiment is a Y-type cable and is applicable to a laser projector with a 2:1 configuration, that is, a laser projector designed in which two light source systems provide laser light to a single video distribution unit. The laser transmission cable 80 includes a first connector 31 and two second connectors 32A and 32B, where the first connector 31 is arranged to be connected to a video distribution unit (e.g., the video distribution unit 22), and the two second connectors 32A and 32B are each arranged to be connected to one light source system (e.g., the light source system 21).

[0043] 8, the laser transmission cable 80 further includes at least one first optical fiber 51A and at least one first optical fiber 51B, where the first optical fiber 51A extends from the first connector 31 to the second connector 32A and is used to transmit laser light from one of the light source systems to the video distribution unit, and the first optical fiber 51B extends from the first connector 31 to the second connector 32B and is used to transmit laser light from the other light source system to the video distribution unit. The laser transmission cable 80 further includes at least one second optical fiber 52A and at least one second optical fiber 52B, where the second optical fiber 52A extends from the first connector 31 to the second connector 32A and is used to transmit a monitor signal from the first connector 31 to the second connector 32A, and the second optical fiber 52B extends from the first connector 31 to the second connector 32B and is used to transmit a monitor signal from the first connector 31 to the second connector 32B.

[0044] 8, the laser transmission cable 80 further includes an optical signal transmitting device 60' and two optical signal receiving devices 70A and 70B, where the optical signal transmitting device 60' is provided in the first connector 31, and the two optical signal receiving devices 70A and 70B are provided in the second connectors 32A and 32B, respectively. In some embodiments, the optical signal transmitting device 60' may include two optical transmitters, one connected to the second optical fiber 52A and the other connected to the second optical fiber 52B, and arranged to input monitor signals to the second optical fibers 52A and 52B, respectively.

[0045] In summary, the laser transmission cable of the present disclosure includes one or more optical fibers for transmitting laser light and an additional optical fiber for transmitting a monitor signal, arranged in parallel. If the optical fiber for transmitting the laser light is damaged, laser energy will leak from the damaged area, burning the optical fiber transmitting the monitor signal and causing an interruption in transmission of the monitor signal. In this case, the optical signal receiving device for receiving the monitor signal detects the interruption in transmission of the monitor signal and turns off a switch provided in the power circuit of the laser light source, automatically turning off the laser light source and avoiding any danger. In some embodiments, a plastic optical fiber can be used as the optical fiber for transmitting the monitor signal. Plastic optical fiber is lightweight, flexible, resistant to low temperatures, and inexpensive, making the production and use of the laser transmission cable more convenient and reducing the manufacturing cost of the laser transmission cable.

[0046] Although the present disclosure has been disclosed above in the embodiments, the above embodiments are not intended to limit the present disclosure, and any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, the scope of protection of the present disclosure should be based on that defined by the scope of the patent application to be attached later. [Explanation of symbols]

[0047] 12: Laser projector 21: Light source system 22: Video Distribution Department 23: Laser light source 28: Power supply circuit 29: Switch 30, 40, 80: Laser transmission cable 31: First connector 32, 32A, 32B: Second connector 33: Output port 34: Input port 35: Metal hose covering 36: First cabinet 37: Second cabinet 48: Stopper coating 49: Internal passage 51, 51A, 51B: First optical fiber 52, 52A, 52B: Second optical fiber 53: 1st end 54: 2nd end 60, 60': Optical signal transmitting device 63: Pulse generator 65: Optical transmitter 67: Circuit board 70, 70A, 70B: Optical signal receiving device 73: Pulse detector 75:Receiver 77: Circuit board 90: Power supply 96: Monitor signal 97: Laser light

Claims

1. at least one first optical fiber for receiving and transmitting laser light from a laser light source; a second optical fiber arranged in parallel with the at least one first optical fiber and having opposing first and second ends; an optical signal transmitter provided at the first end of the second optical fiber and arranged to input a monitor signal into the second optical fiber; an optical signal receiving device provided at the second end of the second optical fiber and configured to receive the monitor signal, the optical signal receiving device being coupled to a switch provided in a power supply circuit connecting the laser light source and configured to turn off the switch when the monitor signal is not received; a laser transmission cable comprising:

2. 10. The laser transmission cable of claim 1, wherein the at least one first optical fiber is made of glass and the second optical fiber is made of plastic.

3. 2. The laser transmission cable of claim 1, further comprising a stopper coating over the at least one first optical fiber and the second optical fiber.

4. 4. The laser transmission cable according to claim 3, wherein the stopper coating has a heat resistance of at least 120°C.

5. 4. The laser transmission cable of claim 3, wherein the stopper coating has a smooth inner surface.

6. 4. The laser transmission cable according to claim 3, further comprising a metal hose covering over the stopper covering.

7. 2. The laser transmission cable of claim 1, wherein the optical signal transmitting device includes a pulse generator and an optical transmitter, the pulse generator being arranged to generate a pulse signal, and the optical transmitter being electrically connected to the pulse generator and arranged to transmit the monitor signal based on the pulse signal.

8. 8. The laser transmission cable of claim 7, wherein the optical signal receiving device includes a pulse detector and an optical receiver, the optical receiver configured to generate an optical response signal, the pulse detector electrically connected to the optical receiver and configured to output a detection signal based on the optical response signal, the detection signal indicating whether the optical receiver has received the monitor signal, and the switch coupled to the pulse detector and configured to switch states based on the detection signal.

9. 9. The laser transmission cable of claim 8, further comprising: a first connector including a first housing; and a second connector including a second housing, wherein opposing ends of the at least one first optical fiber are covered by the first housing and the second housing, respectively; the optical signal transmitting device includes a first circuit board assembly provided in the first housing, the first circuit board assembly including a first circuit board and the pulse generator and the optical transmitter provided on the first circuit board; and the optical signal receiving device includes a second circuit board assembly provided in the second housing, the second circuit board assembly including a second circuit board and the pulse detector and the optical receiver provided on the second circuit board.

10. A laser transmission cable according to any one of claims 1 to 8; a first connector and a second connector, each covering opposite ends of the at least one first optical fiber, and in which the optical signal transmitting device and the optical signal receiving device are respectively provided; a light source system including the laser light source and the switch, and to which the second connector is connected; a video distribution unit to which the light source system is connected via the laser transmission cable and the first connector; A laser projector comprising:

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