Projection device and AR optical waveguide detection system

Abstract

The utility model discloses a projection device and an AR optical waveguide detection system, the projection device comprises a light source part, a relay lens group and an imaging lens group, the relay lens group is arranged on the light emitting side of the light source part, and the relay lens group is used for receiving first light emitted by the light source part and emitting second light; the imaging lens group is arranged on the light emitting side of the relay lens group and comprises a lens group and a light reflecting element, the light reflecting element is provided with a light incident end, a light emitting end and a reflecting surface, the optical axis of the lens group coincides with the optical axis of the relay lens group, and the lens group is used for receiving second light emitted from the relay lens group and emitting third light to the light reflecting element; an acute angle is formed between the normal of the reflecting surface and the optical axis of the lens group, and the reflecting surface is used for changing the transmission path of the third light and emitting the third light from the light emitting end. According to the embodiment, the size of the front end of the lens of the projection device can be reduced, and the probability that the front end of the projection device structurally interferes with the detection device is reduced.

Description

Technical Field

[0001] This application relates to the field of lens technology, and in particular to a projection device and an AR optical waveguide detection system for AR optical waveguide detection. Background Technology

[0002] Augmented Reality (AR) technology is a technique that projects virtual images as real images to enhance the user's perception. In AR technology, optical waveguides are key components, which transmit virtual images through optical waveguides and project them in front of the user to form virtual images.

[0003] In related technologies, the image transmission performance testing system of optical waveguide consists of two parts: a projection optical engine and a testing device. Since the input and output ends of the optical waveguide in AR glasses are on the same side, and the front end of the lens of the projection optical engine is relatively large, it is easy for structural interference to occur with the testing device during debugging. Utility Model Content

[0004] This application provides a projection device and an AR optical waveguide detection system for AR optical waveguide detection, which can reduce the size of the front end of the projection device lens and reduce the probability of structural interference between the front end of the projection device and the detection device.

[0005] In a first aspect, embodiments of this application provide a projection device for AR optical waveguide detection, the projection device comprising:

[0006] The light source is used to output the first ray of light;

[0007] A relay lens group is disposed on the light-emitting side of the light source, and the relay lens group is used to receive the first light and emit the second light.

[0008] An imaging lens group is disposed on the light-emitting side of the relay lens group. The imaging lens group includes a lens group and a light-reflecting element. The light-reflecting element has a light-incident end, a light-emitting end, and a reflecting surface. The optical axis of the lens group coincides with the optical axis of the relay lens group. The lens group is used to receive the second light ray incident from the relay lens group and to emit a third light ray towards the light-incident end. The normal of the reflecting surface is set at an acute angle with the optical axis of the lens group. The reflecting surface is used to change the transmission path of the third light ray and to make the third light ray exit from the light-emitting end.

[0009] In some embodiments of this application, the light reflecting element is a reflecting prism.

[0010] In some embodiments of this application, the light incident end is a first light-transmitting surface, the light emitting end is a second light-transmitting surface, the first light-transmitting surface is disposed facing the lens group, the third light ray passes through the first light-transmitting surface and is emitted to the reflecting surface, and the reflecting surface reflects the third light ray to the second light-transmitting surface, and the third light ray is emitted in a direction perpendicular to the second light-transmitting surface.

[0011] In some embodiments of this application, the reflecting prism and the lens group are spaced apart.

[0012] In some embodiments of this application, the first light-transmitting surface is perpendicular to the optical axis of the lens group.

[0013] In some embodiments of this application, the projection device further includes a macro resolution plate, which is disposed between the light source and the relay lens group, and the first light rays pass through the macro resolution plate and are emitted to the light-inlet side of the relay lens group.

[0014] In some embodiments of this application, the relay lens group includes nine lenses with optical power. The nine lenses are arranged sequentially from the light-inlet side to the light-outlet side of the relay lens group along the optical axis as a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens. The third lens is cemented to the fourth lens, and the fifth lens is cemented to the sixth lens.

[0015] The lens group includes four lenses with optical power. The four lenses are arranged sequentially from the light-inlet side to the light-outlet side along the optical axis as the tenth lens, the eleventh lens, the twelfth lens, and the thirteenth lens, wherein the eleventh lens and the twelfth lens are cemented together.

[0016] In some embodiments of this application, the projection device further includes a virtual aperture, wherein a portion of the first light ray passes through the relay lens group and the imaging lens group to form the virtual aperture on one side of the light emitting end, and the third light ray emitted from the light emitting end exits through the virtual aperture.

[0017] In some embodiments of this application, the aperture of the virtual aperture does not exceed 4 mm.

[0018] Secondly, embodiments of this application provide an AR optical waveguide detection system for detecting image transmission in an optical waveguide, wherein the optical waveguide has a coupling-in region and a coupling-out region located on the same side, and the AR optical waveguide detection system includes:

[0019] As described in any of the above embodiments, the projection device is used to couple with the coupling region to output the third light ray to the coupling region;

[0020] A detection device, which is coupled to the coupling region to receive a fourth light beam output from the coupling region.

[0021] Based on the projection device and AR optical waveguide detection system in this application embodiment, this embodiment sets a light reflection element in the imaging lens group and sets the normal of the reflecting surface at an acute angle with the optical axis of the lens group. After the light is emitted, it can be reversed and transmitted through the light reflection element. In other words, by changing the structure of all the lens groups in the projection device from a coaxial structure to a non-coaxial structure, the light path can be turned, thereby reducing the size of the front end of the lens of the projection device and meeting the detection requirements of the entire imaging device. This achieves flexible configuration of the projection device under strict space constraints. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the projection device in one embodiment of this application;

[0024] Figure 2 This is a schematic diagram of the structure of some projection devices in one embodiment of this application;

[0025] Figure 3 This is a field curvature curve diagram and a distortion curve diagram of the projection device in one embodiment of this application;

[0026] Figure 4 This is a graph showing the optical transfer function of a projection device in one embodiment of this application;

[0027] Figure 5 This is a schematic diagram of the light path of the third light ray passing through the first light-transmitting surface in one embodiment of this application;

[0028] Figure 6 This is a schematic diagram of the AR optical waveguide detection system and the optical waveguide in one embodiment of this application.

[0029] Figure label:

[0030] 100. Projection device;

[0031] 10. Light source; 11. First ray; 12. Second ray; 13. Third ray;

[0032] 20. Relay lens group; L1, first lens; L2, second lens; L3, third lens; L4, fourth lens; L5, fifth lens; L6, sixth lens; L7, seventh lens; L8, eighth lens; L9, ninth lens;

[0033] 30. Imaging lens group; 31. Lens group; 32. Light reflecting element; 321. Reflecting surface; 33. Reflecting prism; 331. Light incident end; 332. Light emitting end; 333. First light-transmitting surface; 334. Second light-transmitting surface; L10. Tenth lens; L11. Eleventh lens; L12. Twelfth lens; L13. Thirteenth lens;

[0034] 40. Macro resolution panel; 50. Virtual aperture;

[0035] 200. Optical waveguide; 61. Coupled-in region; 62. Coupled-out region;

[0036] 300. AR optical waveguide detection system; 70. Detection device. Detailed Implementation

[0037] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, a clear and complete description will be provided below with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0038] In related technologies, the image transmission performance testing system of optical waveguide consists of two parts: a projection optical engine and a testing device. Since the input and output ends of the optical waveguide in AR glasses are on the same side, the projection optical engine and the testing device often face the problem of insufficient space during debugging. In addition, since the front end of the lens of the projection optical engine is large, the two are prone to mutual interference in structure, which increases the complexity of debugging the testing system.

[0039] Regarding the above situation, firstly, please refer to [link / reference needed]. Figures 1-2 This application proposes a projection device 100 for detecting AR (Augmented Reality) optical waveguide 200, including a light source 10, a relay lens group 20 and an imaging lens group 30. The light source 10 is used to output a first light ray 11, which carries image information. The relay lens group 20 and the imaging lens group 30 can be used to transmit the first light ray 11, that is, the relay lens group 20 and the imaging lens group 30 can transmit image information to facilitate subsequent projection of the image.

[0040] The relay lens group 20 is disposed on the light-emitting side of the light source 10. The relay lens group 20 is used to receive the first light ray 11 and emit the second light ray 12. The relay lens group 20 is used to flip the light path and correct aberrations, such as reducing the field curvature of the projection device 100.

[0041] The imaging lens group 30 is disposed on the light-emitting side of the relay lens group 20. The imaging lens group 30 includes a lens group 31 and a light-reflecting element 32. The light-reflecting element 32 has a light-incident end 331 and a light-exit end 332. The second light ray 12 emitted from the light-emitting side of the relay lens group 20 enters the lens group 31. The optical axis of the lens group 31 coincides with the optical axis of the relay lens group 20. The lens group 31 is used to receive the second light ray 12 and emit a third light ray 13 to the light-incident end 331 of the light-reflecting element 32. That is, the light-reflecting element 32 is located on the side of the lens group 31 away from the relay lens group 20.

[0042] Among them, such as Figure 2 As shown, the light reflecting element 32 also has a reflecting surface 321. The normal of the reflecting surface 321 is set at an acute angle with the optical axis of the lens group 31. The reflecting surface 321 is used to change the transmission path of the third light ray 13 and make the third light ray 13 exit from the light emitting end 332. That is, after the third light ray 13 is incident on the reflecting surface 321 from the light incident end 331, the third light ray 13 will be reflected so that the third light ray 13 enters and exits from the same side of the reflecting surface 321. The normal of the reflecting surface 321 is a straight line perpendicular to the reflecting surface 321. When designing the projection device 100, the light can be emitted in reverse. For example, the light can be emitted sequentially from the virtual aperture 50 (described in detail below) to the light reflecting element 32, the lens group 31, and the relay lens group 20. During this process, after the light passes through the imaging lens group 30, a curved intermediate image plane is formed between the imaging lens group 30 and the relay lens group 20. The relay lens group 20 can correct the aberrations of this intermediate image plane, such as reducing field curvature and reducing the height of the intermediate image to the imaging height of the target, thereby facilitating the evaluation of image quality. Finally, after the projection device 100 is designed, it can be used to emit light from the light source 10, which then passes sequentially through the relay lens group 20 and the imaging lens group 30 before being emitted again.

[0043] It should be noted that the light reflecting element 32 may include plane mirrors, prisms, beam splitters, or curved reflectors. In this embodiment, by setting the light reflecting element 32 in the imaging lens group 30 and setting the angle between the normal of the reflecting surface 321 and the optical axis of the lens group 31 at an acute angle, the light can be reversed and transmitted through the light reflecting element 32 after it is emitted. That is, by changing the structure of all the lens groups in the projection device 100 from a coaxial structure to a non-coaxial structure, the light path can be deflected, thereby reducing the size of the front end of the lens of the projection device 100 and meeting the detection requirements of the entire imaging device. This achieves a flexible configuration of the projection device 100 under strict space constraints.

[0044] Specifically, the projection device 100 also includes a lens barrel, a light source 10, a relay lens group 20, and an imaging lens group 30. The relay lens group 20 and the imaging lens group 30 are installed in the lens barrel to form a projectable lens structure. The lens barrel provides a base and installation space for the relay lens group 20 and the imaging lens group 30. The light source 10 may include an integrating sphere light source, LED, OLED, or LCD, etc., for projecting various test images on the test card.

[0045] Please see Figure 1 In some embodiments of this application, the projection device 100 further includes a macro resolution plate 40 (i.e., a chart plate). The macro resolution plate 40 is disposed between the light source 10 and the relay lens group 20. The first light 11 passes through the macro resolution plate 40 and is emitted to the light-inlet side of the relay lens group 20. The light is then coupled into the optical waveguide 200 by the imaging lens group 30. The imaging quality of the optical waveguide 200 is measured by an external detection device.

[0046] Please continue reading Figure 1 In some embodiments of this application, the relay lens group 20 includes nine lenses with optical power. The nine lenses are arranged sequentially from the light-inlet side to the light-outlet side of the relay lens group 20 along the optical axis as a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, and a ninth lens L9. The third lens L3 is cemented to the fourth lens L4, and the fifth lens L5 is cemented to the sixth lens L6, for correcting chromatic aberration.

[0047] like Figure 1 As shown, the lens group 31 includes four lenses with optical power. The four lenses are arranged along the optical axis from the light-inlet side to the light-outlet side as the tenth lens L10, the eleventh lens L11, the twelfth lens L12, and the thirteenth lens L13. The eleventh lens L11 and the twelfth lens L12 are cemented together to correct chromatic aberration.

[0048] The projection device 100 will be described in detail below with reference to specific parameters.

[0049] The data in Table 1 below are the optical parameter data of each optical element in the projection device 100 when the full field of view of the projection device 100 is ±27°, the light reflecting element 32 is a reflecting prism 33, and the reflection angle of the reflecting surface 321 of the reflecting prism 33 to the light is 60°. The specific data are as follows:

[0050] Table 1

[0051]

[0052] in, Figure 3 The two figures in the diagram are, in order, the field curvature curve and the distortion curve from the above embodiment.

[0053] In the field curvature diagram, the horizontal axis represents the focal offset distance, and the vertical axis represents the field of view. Figure 3 The field curvature curves given in the figure indicate that the focal offset distances of the sagittal and meridional image planes are both within ±0.1 mm, which shows that the field curvature of the projection device 100 in this embodiment is small and the imaging quality is good.

[0054] In the distortion curve diagram, the horizontal axis represents the distortion rate, and the vertical axis represents the field of view. Figure 3 The given distortion curve shows that the optical distortion of this embodiment is less than 0.67%, indicating that the distortion of the projection device 100 in this embodiment has been well corrected and the imaging quality is good.

[0055] Figure 4 The figure in the figure is the optical transfer function curve of this embodiment. The optical transfer function (OTF) is greater than 0.3 at 130 lp / mm and is close to the diffraction limit, indicating that the imaging quality of the projection device 100 in this embodiment is good.

[0056] Therefore, according to Figures 3-4 As can be seen, the projection device 100 given in this embodiment can achieve good imaging effect.

[0057] Please see Figure 2 In some embodiments of this application, the light reflecting element 32 is a reflecting prism 33. The reflecting prism 33 has multiple surfaces, at least one of which is a reflecting surface 321, and the other surfaces can be light-transmitting surfaces, so that the third ray 13 can enter the interior of the reflecting prism 33 through the light-transmitting surface and finally exit the prism under the reflection of the reflecting surface 321. In the embodiments of this application, the shape of the reflecting prism 33 can be regular or irregular. At the same time, this embodiment does not limit the refractive index of the reflecting prism 33 or the reflection angle of the reflecting surface 321 on the third ray 13, and both can be selected according to the actual situation.

[0058] Further reading is available upon request. Figure 2 In some embodiments of this application, on the reflecting prism 33, the light incident end 331 is the first light-transmitting surface 333, and the light emitting end 332 is the second light-transmitting surface 334. The first light-transmitting surface 333 is disposed facing the lens group 31. After the third light ray 13 is emitted from the lens group 31, it first passes through the first light-transmitting surface 333 and enters the interior of the reflecting prism 33. Then it hits the reflecting surface 321, and the reflecting surface 321 reflects the third light ray 13 to the second light-transmitting surface 334. The third light ray 13 is emitted in a direction perpendicular to the second light-transmitting surface 334.

[0059] like Figure 2 As shown, the first light-transmitting surface 333 is perpendicular to the optical axis of the lens group 31, allowing the third ray 13 emitted from the optical axis of the lens group 31 to enter the reflecting prism 33 perpendicularly and be reflected in the middle of the reflecting prism 33. The second light-transmitting surface 334 can be positioned opposite to the reflecting surface 321, so that all light reflected from the reflecting surface 321 can exit from a direction perpendicular to the second light-transmitting surface 334, thereby improving the utilization rate of the third ray 13.

[0060] Further, please see Figure 2 In some embodiments of this application, the reflecting prism 33 and the lens group 31 are spaced apart. It is easy to understand that the third ray 13 emitted from the lens group 31 first contacts the air and then enters the reflecting prism 33 from the air. According to the optical theorem: when light enters a plane perpendicularly from air (or other medium), the direction of propagation does not change. When light enters water or other medium obliquely from air, the angle of refraction is less than the angle of incidence. The angle of incidence is the angle between the incident ray and the normal to the incident surface, and the angle between the refracted ray and the normal is called the angle of refraction. That is to say, before the third ray 13 obliquely enters the first light-transmitting surface 333, the angle of incidence of the third ray 13 relative to the first light-transmitting surface 333 is α. After the third ray 13 obliquely enters the first light-transmitting surface 333, the angle of refraction of the third ray 13 relative to the first light-transmitting surface 333 is β, and α>β.

[0061] Therefore, as Figure 5 As shown, after the third ray 13 obliquely enters the first light-transmitting surface 333 from the air, the angle between the third ray 13 and the normal of the first light-transmitting surface 333 will decrease. Therefore, after all the third rays 13 enter the reflecting prism 33, the effective area of ​​the light reaching the reflecting surface 321 is reduced. Thus, the size of the reflecting prism 33 can be appropriately reduced, which means the size of the front end of the lens of the projection device 100 can be reduced to meet the detection requirements of the entire imaging device.

[0062] Please see Figure 6In some embodiments of this application, the projection device 100 also has a virtual aperture 50. After a portion of the first light ray 11 passes through the relay lens group 20 and the imaging lens group 30, a virtual aperture 50 is formed on one side of the light emitting end 332. That is, the virtual aperture 50 is formed between the projection device 100 and the coupling region 61 of the optical waveguide 200. The third light ray 13 can enter the coupling region 61 of the optical waveguide 200 after passing through the virtual aperture 50. The virtual aperture 50 is used to limit the beam or limit the size of the field of view (imaging range). The virtual aperture 50 is formed by the projection of the first light ray 11 and the lens group, and has no physical structure, which can reduce the space occupied in the projection device 100 and reduce the size of the projection device 100.

[0063] Furthermore, the aperture of the virtual aperture 50 does not exceed 4mm, and the size of the projection device 100 is reduced as much as possible while ensuring the imaging range of the projection device 100.

[0064] Secondly, please see Figure 6 This application embodiment also provides an AR optical waveguide detection system 300. The performance of the optical waveguide 200 directly affects the image display quality of AR glasses. A high-quality optical waveguide 200 can ensure that the image remains clear and has its original contrast during transmission. The optical waveguide 200 has a coupling-in region 61 and a coupling-out region 62 located on the same side. External image information is input into the optical waveguide 200 through the coupling-in region 61, and after transmission, it is output from the coupling-out region 62. The AR optical waveguide detection system 300 in this embodiment can be used to detect the image transmission quality of the optical waveguide 200.

[0065] The AR optical waveguide testing system 300 includes a testing device 70 and a projection device 100 as described in any of the above embodiments. The projection device 100 is used to couple with the coupling region 61 to output a third ray 13 to the coupling region 61. The testing device 70 is used to couple with the coupling region 62 to receive a fourth ray output from the coupling region 62. The testing device 70 can receive the fourth ray output from the coupling region 62 and measure the quality of the transmitted test image.

[0066] Specifically, coupling generally refers to the interdependence, mutual influence, and mutual constraint between various parts within a system, that is, the interactive connection relationship between two or more components or parts. The projection device 100 is used to couple with the coupling zone 61, that is, the projection device 100 can transmit the third light 13 into the coupling zone 61; the detection device 70 is coupled with the coupling zone 62, that is, the coupling zone 62 can transmit the fourth light 13 into the detection device 70. Among them, the third light 13 can carry information of the test image. Multiple test images can correspond to different optical performances of the optical waveguide 200. For example, the test images can include a checkerboard image (for contrast testing), a line pair image (for resolution testing), and a cross or beveled image (for MTF curve measurement).

[0067] It should be noted that by setting a light reflecting element 32 (reflecting prism 33) in the imaging lens group 30, the structure of all the lens groups in the projection device 100 is changed from a coaxial structure to a non-coaxial structure, so as to facilitate the reversal of the light path, thereby reducing the light angle and reducing the size of the lens front end of the projection device 100, which meets the detection requirements of the entire imaging device. In other words, it reduces the probability of structural interference between the projection device 100 and the detection device 70, and increases the flexibility and adaptability of the AR optical waveguide detection system 300.

[0068] In the accompanying drawings of this embodiment, the same or similar reference numerals correspond to the same or similar components. In the description of this application, it should be understood that if terms such as "upper," "lower," "left," and "right" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the components or elements referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting this application. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0069] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A projection device for AR optical waveguide detection, characterized in that, The projection device includes: The light source is used to output the first ray of light; A relay lens group is disposed on the light-emitting side of the light source, and the relay lens group is used to receive the first light and emit the second light. An imaging lens group is disposed on the light-emitting side of the relay lens group. The imaging lens group includes a lens group and a light-reflecting element. The light-reflecting element has a light-incident end, a light-emitting end, and a reflecting surface. The optical axis of the lens group coincides with the optical axis of the relay lens group. The lens group is used to receive the second light ray incident from the relay lens group and to emit a third light ray towards the light-incident end. The normal of the reflecting surface is set at an acute angle with the optical axis of the lens group. The reflecting surface is used to change the transmission path of the third light ray and to make the third light ray exit from the light-emitting end.

2. The projection device according to claim 1, characterized in that, The light-reflecting element is a reflective prism.

3. The projection device according to claim 2, characterized in that, The light incident end is a first light-transmitting surface, and the light emitting end is a second light-transmitting surface. The first light-transmitting surface is arranged facing the lens group. The third light ray passes through the first light-transmitting surface and is emitted to the reflecting surface. The reflecting surface reflects the third light ray to the second light-transmitting surface. The third light ray is emitted in a direction perpendicular to the second light-transmitting surface.

4. The projection device according to claim 3, characterized in that, The reflecting prism is spaced apart from the lens group.

5. The projection device according to claim 3, characterized in that, The first light-transmitting surface is perpendicular to the optical axis of the lens group.

6. The projection device according to claim 1, characterized in that, The projection device also includes a macro resolution plate, which is disposed between the light source and the relay lens group. The first light rays pass through the macro resolution plate and are emitted to the light-inlet side of the relay lens group.

7. The projection device according to claim 1, characterized in that, The relay lens group includes nine lenses with optical power. The nine lenses are arranged sequentially from the light-inlet side to the light-outlet side of the relay lens group along the optical axis as a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens. The third lens is cemented to the fourth lens, and the fifth lens is cemented to the sixth lens. The lens group includes four lenses with optical power. The four lenses are arranged sequentially from the light-inlet side to the light-outlet side along the optical axis as the tenth lens, the eleventh lens, the twelfth lens, and the thirteenth lens, wherein the eleventh lens and the twelfth lens are cemented together.

8. The projection device according to claim 1, characterized in that, The projection device also has a virtual aperture. After a portion of the first light ray passes through the relay lens group and the imaging lens group, the virtual aperture is formed on one side of the light emitting end. The third light ray emitted from the light emitting end exits through the virtual aperture.

9. The projection device according to claim 8, characterized in that, The aperture of the virtual aperture does not exceed 4mm.

10. An AR optical waveguide detection system, characterized in that, For detecting image transmission in an optical waveguide, the optical waveguide having an input region and an output region located on the same side, the AR optical waveguide detection system includes: The projection device as described in any one of claims 1 to 9, wherein the projection device is configured to couple with the coupling region to output the third ray to the coupling region; A detection device, which is coupled to the coupling region to receive a fourth light beam output from the coupling region.

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