Optical system for optical wireless communication

Abstract

The position sensing device is positioned separate from a focal plane on which a portion of the incident beam is focused. A position sensing signal generated by the position sensing device is used to steer the incident beam relative to the lens arrangement for focusing portions of the incident beam.

Description

Technical Field

[0001] This invention relates to the field of optical wireless communication, and particularly to optical systems for optical wireless communication. Background Technology

[0002] Wireless communication using modulated light is becoming increasingly common and is often referred to as optical wireless communication (OWC).

[0003] Optical wireless communication refers to the technology of transmitting information in the form of signals embedded in light emitted by a light source. In this context, light can include any visible or invisible light (such as infrared light). Depending on the specific wavelength used, this technology may also be referred to as coded light, optical fidelity (LiFi), visible light communication (VLC), or free-space optical communication (FSO).

[0004] Optical wireless communication can be performed using a focused or collimated beam. In this method, the transceivers on both sides need to be properly aligned to allow communication in both directions.

[0005] Therefore, it is desirable to improve the mechanism used to align a beam generated by an optical wireless communication device with its communication partner.

[0006] An example of a method for aligning a beam generated by an optical wireless communication device with its communication partner is provided in: "Control of fast steering mirror for accurate beam positioning in FSO communication system" by Lahari Sreerama Aamrutha et al., published in the 2021 INTERNATIONAL CONFERENCEON SYSTEM, COMPUTATION, AUTOMATION AND NETWORKING (ICSCAN), IEEE, July 30, 2021. This paper discloses a method for beam positioning using a PID controller, a fuzzy logic controller, and a four-quadrant detector. The four-quadrant detector is used as a position sensor and consists of four photodiodes capable of detecting the laser beam on its surface and determining the offset position of the laser spot from its center.

[0007] Another approach for beam manipulation and adaptive beam control is provided in Mai Vuong et al.'s paper, "Non-Mechanical Beam Steering and Adaptive Beam Control Using Variable Focus Lenses for Free-Space Optical Communications," published on June 8, 2021, in the Journal of Lightwave Technology, IEEE, USA, Vol. 39, No. 24. In this paper, the authors investigated the possibility of using variable focus lenses to achieve beam manipulation and adaptive beam control for FSOC. To this end, they employed three variable focus lenses: one coaxial lens for adaptive beam divergence control and two eccentric lenses for two-dimensional beam manipulation, and they demonstrated the ability of this variable focus lens-based system to simultaneously perform beam manipulation and adaptive beam control over a 104 m long free-space optical link. Summary of the Invention

[0008] This invention is defined by the claims.

[0009] According to an example of one aspect of the invention, an optical system is provided for generating a data signal in response to embedded information carried by an incident light beam.

[0010] The optical system includes: a beam manipulation device configured to controllably manipulate the direction of an incident beam; a beam splitter configured to split the incident beam into a first beam and a second beam at an angle relative to each other after being manipulated by the beam manipulation device; a lens arrangement configured to focus the first beam to a first focal point located in a first focal plane and to focus the second beam to a second focal point in a second focal plane; a position-sensitive device configured to generate a position sensing signal in response to the position of the first beam incident on a receiving surface of the position-sensitive device, wherein the receiving surface of the position-sensitive device is positioned to receive the first beam and separated from the first focal plane by a non-zero distance; and a light-sensing module positioned to receive the second beam and configured to generate a data signal in response to embedded information carried by the second beam, wherein the beam manipulation device is configured to manipulate the direction of the incident beam in response to the position sensing signal generated by the position-sensitive device.

[0011] The output of the position-sensitive device provides a feedback signal that allows the direction of the beam manipulated by the beam manipulation device to be adjusted by means of a control loop. The control loop is designed to guide the incident beam through the optical axis of the lens arrangement, and a deviation from the optimal direction will cause the first beam to change its position on the photosensing module, thereby generating a feedback signal for adjusting the control signal used for the beam manipulation device.

[0012] Preferably, a non-zero distance (between the receiving surface of the position-sensitive device and the first focal plane) is selected so that the control loop converges for the target detection range of the optical system. This avoids the control loop from going out of control.

[0013] Preferably, the non-zero distance is not less than 0.05 mm, for example, not less than 0.1 mm.

[0014] The lens arrangement can be positioned between the beam manipulation device and the beam splitter.

[0015] Alternatively or additionally, the lens arrangement includes: a first lens sub-arrangement positioned between the beam splitter and the position-sensitive device; and a second lens sub-arrangement positioned between the beam splitter and the photosensitive module.

[0016] In some examples, the first focal plane is positioned between the lens arrangement and the position-sensitive device.

[0017] In some examples, the non-zero distance between the first focal plane and the position-sensitive device is no greater than the value calculated by the following formula: , where f is the distance between the first focal plane and the lens arrangement (i.e., the effective focal length), L is the target detection distance of the optical system, and k is the distance the first beam travels between the beam manipulation device and the lens arrangement.

[0018] In some examples, the position-sensitive device includes one or more dark areas with a width, and the non-zero distance between the first focal plane and the position-sensitive device is not less than a value calculated by the following formula: Where W is the width of one or more dark areas, and D B f is the diameter of the incident beam; and f is the distance between the first focal plane and the lens arrangement.

[0019] In a preferred example, the light sensing module is positioned to receive the second light beam at the second focal plane.

[0020] The optical system may also include a positioning system configured to facilitate controllable adjustment of the distance between the first focal plane and the position-sensitive device in response to at least one target detection distance of the optical system. This method allows adjustment of the lens arrangement and the distance between the position-sensitive device to adapt the optical system to different target detection distances.

[0021] The positioning system may include, for example, an actuator configured to controllably move a lens arrangement (or a portion thereof) and / or a position-sensitive device to facilitate control of the distance between the first focal plane and the position-sensitive device.

[0022] The beam manipulation device can be a rotatable mirror.

[0023] A beam splitter can be a partial transmission mirror.

[0024] A position-sensitive device can be a two-dimensional position-sensitive device, meaning it can monitor or detect the position of the first beam of light incident on a light-receiving surface in a two-dimensional manner. A suitable example of a two-dimensional position-sensitive device is a four-quadrant photodetector.

[0025] The beam splitter can be configured such that the first beam includes at least 5% (e.g., at least 10%) of the incident beam and / or the second beam includes at least 5% (e.g., at least 10%) of the incident beam. In a preferred example, the beam splitter is configured such that the second beam includes at least 25% (e.g., at least 50%) of the incident beam for improved intensity of the data signal.

[0026] An optical wireless communication device is also provided, including any optical system disclosed herein; and a processing system configured to receive data signals and extract embedded information from the data signals.

[0027] An optical wireless communication system is also provided, comprising: an optical wireless communication device as disclosed herein; and a second optical wireless communication device configured to generate a light beam carrying embedded information and to transmit the generated light beam to the optical wireless communication device, wherein the transmitted light beam serves as the incident light beam of the optical system of the optical wireless communication device.

[0028] When both optical wireless communication devices include beam manipulation devices, beam splitters, lens arrangements and position-sensitive devices as described in the reference optical wireless communication device, and beam generators as described in the reference second optical wireless device, bidirectional communication is facilitated, which uses the beam manipulation devices and beam splitters as integral parts of the receiving and transmission paths of the optical wireless communication devices.

[0029] These and other aspects of the invention will become apparent from the embodiments described below, and will be explained with reference to the embodiments described below. Attached Figure Description

[0030] To better understand the invention and to more clearly illustrate how to implement it, reference will now be made to the accompanying drawings by way of example only, wherein: Figure 1An optical wireless communication system is shown; Figure 2 The light spot on the position sensing device at the first focal plane is shown; Figure 3 The light spot on the position sensing device, located away from the first focal plane, is shown; Figure 4 Various parameters are shown; Figure 5 Various relationships between the target detection distance and the distance between the first focal plane and the position sensing device are shown; Figure 6 An alternative optical system is shown; and Figure 7 The positioning system is shown. Detailed Implementation

[0031] The invention will be described with reference to the accompanying drawings.

[0032] It should be understood that while the detailed description and specific examples indicate exemplary embodiments of the devices, systems, and methods, they are intended for illustrative purposes only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the devices, systems, and methods of the present invention will become better understood from the following description, the appended claims, and the accompanying drawings. It should be understood that the drawings are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the drawings to indicate the same or similar parts.

[0033] This invention provides an optical system for an optical wireless communication device. A position sensing device is positioned separate from the focal plane to which a portion of an incident light beam is focused. A position sensing signal generated by the position sensing device is used to manipulate the incident light beam relative to a lens arrangement for focusing a portion of the incident light beam.

[0034] Optical wireless communication (OWC) devices can be configured or designed to communicate with another OWC device within a specific range of target detection distance. Example ranges may include, for example, the following: 1 m to 2 m; 10 m to 20 m; 100 m to 250 m, etc. Other suitable ranges will be apparent to those skilled in the art.

[0035] Figure 1 An optical wireless communication system 100 is illustrated, in which embodiments may be employed for improved context understanding. The optical wireless communication system 100 includes a first optical wireless communication device 110 and a second optical wireless communication device 120 configured to communicate with each other.

[0036] The first optical wireless communication device 110 includes an optical system 150 and a processing system 160. The optical system 150 is configured to generate a data signal S in response to embedded information (e.g., generated by the second optical wireless communication device 120) carried by the incident light beam 125. D .

[0037] The optical system 150 includes a beam manipulation device 151 configured to controllably manipulate the direction of an incident beam. In the example shown, the beam manipulation device 151 includes a tiltable or rotatable mirror. The direction of the incident beam is controlled by a processing system 160. In other words, the operation of the beam manipulation device can be controlled by the processing system 160, for example, via a control signal S. C control.

[0038] By way of example only, a beam manipulation device can be a reflective beam manipulation device, such as a 1D or 2D rotatable mirror or mirror assembly. In alternative examples, a beam manipulation device can include an active element surface reflector or a reflective optical phase array device, such as an LCoS spatial light modulator (SLM), which can have phase-only modulation (also known as a phase light modulator or PLM) or a combination of phase and amplitude modulation.

[0039] As other examples, beam manipulation devices may include transmission devices such as 1D or 2D addressable transmission twisted nematic liquid crystal cells (as transmission PLMs), transmission 1D or 2D active element surface elements, liquid wedges, or deformable liquid lens systems.

[0040] Other suitable forms and structures for the beam manipulation device 151 will be apparent to those skilled in the art.

[0041] The optical system 150 also includes a beam splitter 152, which is configured to split the incident beam into a first beam and a second beam at an angle to each other after being manipulated by the beam manipulation device.

[0042] The optical system 150 also includes a lens arrangement 153 configured to focus a first beam to a first focal point located in a first focal plane P1 and to focus a second beam to a second focal point in a second focal plane P2.

[0043] In the example shown, lens arrangement 153 includes a first lens sub-arrangement 153A (e.g., a first lens) for focusing a first beam and a second lens sub-arrangement 153B (e.g., a second lens) for focusing a second beam. More specifically, the first lens sub-arrangement 153A is positioned between the beam splitter and the position-sensitive device. The second lens arrangement 153B is positioned between the beam splitter and the photosensing module.

[0044] The optical system 150 also includes a position-sensitive device 154, which is configured to generate a position sensing signal S in response to the position of the first light beam incident on the receiving surface 154A of the position-sensitive device. P The receiving surface 154A of the position-sensitive device is positioned to receive the first light beam and is separated from (at least) the first focal plane, and preferably from any focal line of the first lens sub-arrangement 153A, by a non-zero distance dx. The lens sub-arrangement may include a single focal line or multiple focal lines, for example, two orthogonal focal lines resulting from astigmatism of the lens sub-arrangement.

[0045] Examples of suitable position-sensitive devices are well known in the art and include segmented photodetectors (e.g., four-quadrant photodetectors), photodiode arrays, CMOS sensors, CCD arrays, other image sensors, etc.

[0046] Another alternative could be a staring array or focal plane array (FPA), which is (effectively) an image sensor with very limited or no dark space between pixels. Although more expensive, such an array sensor would provide more direct identification of the source location over a very large field of view, and thus significantly reduce acquisition time.

[0047] The optical system 150 also includes a light sensing module 155, which is positioned to receive the second light beam and configured to generate a data signal in response to embedded information carried by the second light beam. Preferably, the light sensing module is positioned to receive the second light beam at a second focal plane.

[0048] The light sensing module may include, for example, a photoelectric light sensor and a transimpedance amplifier. Other suitable configurations for forming the light sensing module will be apparent to those skilled in the art, such as including one or more photodiodes (e.g., a photodiode array) or a camera.

[0049] In one example, the light sensing module includes an optical fiber with an optical opening positioned to receive a second beam of light (for coupling the light received therein). The optical fiber can then guide the coupled light to a dedicated light sensor.

[0050] Then, the data signal S generated by the light sensing module D It can be output from the optical system to, for example, a processing system. Of course, it should be understood that the data signal S... D It does not need to be provided to the receiving position sensing signal S P (And the same processing system that controls the beam manipulation device 151). Conversely, the data signal can be provided to a completely independent processing system, such as a data processor.

[0051] The beam manipulation device 151 is configured to manipulate the direction of the incident beam in response to a position sensing signal generated by a position-sensitive device. In this way, the position sensing signal (generated by the position-sensitive device 154) effectively serves as an error signal, which can be used (e.g., via a control loop) to manipulate the beam manipulation device 151.

[0052] More specifically, the position sensing signal can provide an indication of the distance and / or direction of the first beam relative to the center point of the receiving surface 154A (which may alternatively be marked as a reference point). The beam manipulation device 151 can be configured to manipulate or guide the incident beam such that the first beam is positioned at a known location relative to the center point of the receiving surface, for example, centered on the center point of the receiving surface. Suitable methods for performing such control are known in the art.

[0053] The center point does not need to be precisely at the center of the receiving surface. Instead, the center point identifies the position of the first focused beam, for which the corresponding focused second beam provides the maximum usable light intensity to the photosensing module. This can be achieved through proper calibration, configuration, and / or positioning of the position-sensitive device and the photosensing module relative to the lens arrangement.

[0054] Specifically, the incident test beam (carrying embedded test information) can be guided toward the optical system and manipulated using a beam manipulation device until the data signal S is obtained. D The center point is defined by the intensity being at its maximum. The position of the light spot generated on the receiving surface 154A of the position sensing device 154 by the focused first beam (which is the focused portion of the incident test beam) can define the center position or can be the center position.

[0055] The processing system 160 can be configured to receive data signals and extract embedded information from the data signals. The extracted embedded information can then be output from the processing system, or further processed by the processing system, for performing any task for which the optical wireless communication device is designed (e.g., displaying embedded information, storing embedded information, etc.). Further use of the embedded information is not critical for the purposes of the proposed invention.

[0056] Another possible feature of the first optical wireless communication device is a beam generating device 170 for generating a beam 175 for communicating with the second optical wireless communication device 120.

[0057] The generated beam 175 can be used with the same beam manipulation device 151 to provide an outgoing beam (not shown) carrying modulation information for transmission to a second optical wireless communication device. In such a method, changing the direction of the incident beam (using the beam manipulation device 151) will similarly result in a change in the direction of the outgoing beam.

[0058] In the example shown, beam generating device 170 includes a beam generator 171 and a mirror 172. The mirror is configured to guide the beam 175 generated by the beam generator 171 toward the beam manipulation device 151. The mirror 172 may be located in the path taken by the incident beam 125, but is suitably configured to avoid reflection of the incident beam. This can be performed, for example, by performing wavelength-selective reflection and / or polarization-selective reflection. Other suitable methods are known to those skilled in the art.

[0059] The structure and operation of the second optical wireless communication device 120 may be similar to / identical to the structure and operation of the first optical wireless communication device, and will not be repeated for the sake of simplicity. Of course, it should be understood that the beam generator and / or position-sensitive device of the second optical wireless communication device may be configured to complement the beam generator and / or position-sensitive device of the first optical wireless communication device (which may be important if the beam generator and / or position-sensitive device is wavelength-dependent).

[0060] for Figure 1 In the system shown, if the beam manipulation device has been properly controlled or manipulated in response to a position sensing signal, the first beam will be positioned parallel to the optical axis of the first lens arrangement 153A and centered on the optical axis of the first lens arrangement 153A. This will result in the first beam (after being focused by the first lens arrangement) being positioned at the center point on the receiving surface 154A of the position-sensitive device 154.

[0061] The position and / or configuration of the light sensing module 155 are calibrated using the position sensing device 154 such that when the position sensing device receives the first light beam at the center point on its receiving surface 154A, the light sensing module will similarly receive the maximum available or potential intensity of the second light beam.

[0062] Therefore, if the beam manipulation device is controlled to position the first beam at the center point on the receiving surface, this will similarly aim to maximize the amount of the second beam incident on the light sensing module 155 (i.e., the light intensity and therefore the signal strength).

[0063] As previously described, the receiving surface 154A of the position-sensitive device is positioned to receive the first beam and is separated from the first focal plane by a non-zero distance dx. The first focal plane is the plane containing the focal point to which the first beam is focused. If astigmatism and / or other optical distortions are present, this focal point is preferably the farthest focal point among all the focal points that can be distinguished relative to the first beam.

[0064] The advantages of the proposed method are achieved by moving the position sensing device 154, more specifically the receiving surface, away from the first focal plane.

[0065] More specifically, it has been recognized that an incident beam laterally displaced (but parallel to) the optical axis (i.e., the "ideal incident direction") of an "ideal" incident beam will similarly produce a first beam and a second beam laterally displaced from the lens arrangement. Thus, in the example shown, the first beam will be displaced from the first lens arrangement, and the second beam will be laterally displaced from the second lens arrangement. If manipulated in the same way as the ideal incident beam, the laterally displaced incident beams will cause all light that is not from the first / second beam to fall onto the lens arrangement, and thus be practically lost. This, of course, is under the assumption that the radius of the first / second beam at the lens arrangement is equal to or less than the radius of the lens arrangement.

[0066] However, when focused, the laterally shifted first beam will be located at the same position on the receiving surface in the focal plane as the (focused) first beam generated by the ideal incident beam. This will hinder accurate correction of the direction of the incident beam, resulting in reduced light intensity at the photosensing module.

[0067] Figure 2 and Figure 3 The light spots (as a result of laterally displaced incident beams) generated on the receiving surface 134A of the position sensing device 134 at different distances from the first focal plane are shown. In the example shown, the position sensing device is a quadrant detector, whose quadrants are schematically shown using dashed lines.

[0068] Figure 2 The diagram shows the case where the receiving surface 134A is located at the first focal plane. The light spot 200 generated by the laterally shifted incident beam will be centered on the center of the receiving surface 134A.

[0069] Figure 3 The diagram illustrates a scenario where the receiving surface 134A is a certain distance from the first focal plane. The light spot 300, generated due to the laterally shifted incident beam, will not be centered on the center of the receiving surface 134A. Therefore, a position sensing signal (acting as an error signal) can be generated to correct or move the light spot 300 to be centered on the center point of the receiving surface 134A.

[0070] Therefore, by moving the receiving surface away from the first focal plane, a portion (center or average value) of the laterally displaced beam incident on the receiving surface will move away from the center point. This allows the beam manipulation device to be corrected to achieve improved light intensity at the light sensing module 155.

[0071] As mentioned earlier, the first optical wireless communication device 110 may include a beam generating device 170 utilizing the same beam manipulation device, and the second optical wireless communication device 120 may include features corresponding to the first optical wireless communication device 110.

[0072] Therefore, the first optical wireless communication device 110 can generate an incident beam for the second optical wireless communication device, and the second optical wireless communication device 120 can generate an incident beam for the first optical wireless communication device.

[0073] The proposed optical system is particularly advantageous for use in such examples because the directions of the two incident beams will be manipulated such that for each optical wireless communication device 110, 120, the first beam converges at the center point of the receiving surface, even taking into account the change in the direction of the incident beam when the other optical wireless communication device manipulates its corresponding beam manipulation device.

[0074] Reference Figure 1 The beam splitter can be configured such that the first beam includes fewer incident beams than the second beam. This recognizes that the need for high-intensity signals for communication is more advantageous than for high-intensity signals for manipulating beams.

[0075] In certain examples, the beam splitter can be configured such that the first beam includes at least 25% of the incident beam. In some examples, the beam splitter can be configured such that the first beam includes less than 50% of the incident beam.

[0076] The second beam may include not less than 25% of the incident beam, for example, not less than 50% of the incident beam.

[0077] Other embodiments recognize specific design techniques for selecting an appropriate distance between the first focal plane and the receiving surface to achieve preferred characteristics. In the examples described below, it is assumed that the beam manipulation device includes a tiltable mirror.

[0078] A non-zero distance between 0.15 mm and 0.8 mm provides good design flexibility for optical systems designed to receive incident beams from distances between 0.02 m and 2 m. A non-zero distance between 0.05 mm and 0.30 mm provides good design flexibility for optical systems designed to receive incident beams from distances between 0.5 m and 50 m. A non-zero distance between 0.05 mm and 0.20 mm provides good design flexibility for optical systems designed to receive incident beams from distances between 2.5 m and 250 m. Other suitable variations will be apparent based on the techniques described herein for selecting or defining non-zero distances.

[0079] Figure 4 Various terms are shown for understanding the parameters used in mathematical formulas to derive the appropriate distance.

[0080] In particular, Figure 4The following terms are shown: focal length f (distance between the lens arrangement and the first focal plane F); target detection distance L (target distance between the first and second optical wireless communication devices); travel distance K (distance traveled by the first beam from the beam manipulation device 151 to the lens arrangement); beam angle α (angle between the first beam and the optical axis of the first lens arrangement); beam diameter D. B Pupil diameter D P (Optical transmission diameter of the first lens arrangement); mirror rotation MR; beam displacement d BP (Displacement or distance at the first lens arrangement, between the first beam and the first lens arrangement); and the non-zero distance dx between the first focal plane F and the receiving surface 134 of the position sensing device.

[0081] The mirror step size value ΔMR is also defined, which defines the minimum step size that can be achieved in mirror rotation when rotating a tiltable mirror.

[0082] Note the values ​​of the beam angle α and the beam displacement d. BP The value of will change in response to the direction of the incident beam manipulated by the beam manipulation device. Therefore, there will be a beam angle α and a beam displacement d. BP The combination of these factors will cause the first focused beam to be incident on the center point of the receiving surface of the position sensing device. This occurs when the following equation holds (assuming D). B =D P ): Considering all possible combinations of angle and beam displacement, and representing the beam displacement according to the finite basic step size of the mirrors and the distances L and k and the focal length f, there exists a value for dx that marks the interval between the convergence and potential divergence of the control loop, i.e., the beam runaway due to mirror adjustments far from ideal conditions. This critical dx value (dx c ) can be expressed as follows under the condition that (L + 2k) > 4f: More specifically, equation (2) can be effectively used to define the convergence conditions for a pair of optical wireless communication devices (i.e., to avoid runaway of the first beam and / or undefined final lateral offset).

[0083] More specifically, equation (2) can define an upper bound on the value of the non-zero distance dx to achieve or ensure convergence.

[0084] Therefore, one method for determining the value of the distance dx between the first focal plane and the receiving surface of the position sensing device is to select a critical dx value dx located between 0 and the maximum target detection distance designed or to be designed for the optical system. c The distance between them.

[0085] However, an improved approach to determining the value of distance dx is to further consider residual beam offset, which will occur after the control of the beam manipulation device has stabilized or entered a steady or quasi-steady state (because in some cases, the control of the beam manipulation device can oscillate infinitely around the time-averaged residual beam offset).

[0086] More specifically, residual beam offset is a value representing the relative offset of the steady-state beam (i.e., after the control of the beam manipulation device has stabilized or become steady) relative to the idealized beam position (i.e., the distance between the optical axis of the lens arrangement and the central axis of the first beam).

[0087] The minimum usable residual beam offset is defined at an ideal non-zero distance dx ideal At this point, under the condition (L+2*k)>[6 -√(20)]*f, it can be defined by the following equation: The value of the residual beam offset will vary with the difference between the non-zero distance dx and the ideal non-zero distance dx. ideal It increases as the difference between them increases.

[0088] Equation (3) makes it possible to determine the ideal value of a non-zero distance, such as a known target detection distance, focal length, and lens arrangement.

[0089] The maximum residual beam displacement d that may still exist for a steady-state beam (i.e., after the beam manipulation device has stabilized or become steady-state). BP_MAX Under the conditions that 0 < dx < f / [(L+2*k) / (4*f)-1] and (L+2*k) > 4*f, it can be expressed as: The maximum residual beam displacement represents the maximum possible beam displacement of the steady-state beam.

[0090] In L>4*f-2*kd BP_MAX Under the condition of / ΔMR, the minimum non-zero distance dx of the maximum allowable residual beam displacement that meets the requirements is dx. min It is given by the following formula: The maximum value of the non-zero distance dx of the maximum allowable residual beam displacement that meets the requirements. max It is given by the following formula: Equations (5) and (6) can be used to control or define the value of dx, which falls within the desired target detection distance L and / or the desired target detection distance range.min and dx max Between. For example, the value of dx can be identified as falling equidistant from dx. min and dx max The value between, i.e., dx min and dx max The average value. However, other suitable techniques can be used, such as selecting dx. min or dx max .

[0091] There exists a range of desired target detection distances (within the minimum target detection distance L). min and maximum target detection distance L max Between), then when applying equation (5): L = L min And when equation (6) is applied, L = L max .

[0092] Therefore, by using equation (5) to process the minimum target detection distance L min It is possible to calculate the minimum value of the non-zero distance dx min The maximum target detection distance L is processed using equation (6). max The maximum value of the non-zero distance dx can be calculated. max .

[0093] It is evident that the lines for the minimum and maximum dx values ​​intersect at a certain L value, which signifies the longest possible detection distance L under given boundary conditions.

[0094] For example, consider an optical wireless communication device with the following characteristics: a mirror step angle ΔMD of 50 μrad, a focal length f of 20 mm, a travel distance k of 40 mm, and a maximum permissible residual beam displacement d. BP_MAX The value is 0.6 mm. This is equivalent to 10% for an incident beam with a beam diameter of 6 mm. According to equations (4) and (5), we can determine that for the desired target detection range between 0.1 m and 2 m, then: dx min = 0.13 mm, and dx max = 0.66 mm.

[0095] In one variation, the maximum permissible residual lateral beam displacement d is considered. BP_MAX The case where it is 1.8 mm (i.e., 30% for an incident beam with a beam diameter of 6 mm). In this variation, dx min = 0.04 mm, and dx max = 0.75mm.

[0096] As another example, consider an optical wireless communication device with the following characteristics: a mirror step angle ΔMD of 25 μrad, a focal length f of 80 mm, a beam diameter of 23 mm, a travel distance k of 40 mm, and a maximum permissible residual beam displacement d. BP_MAX The value is 10 mm. According to equations (4) and (5), we can determine that for the desired target detection range between 50 m and 150 m, then: dx min = 0.06 mm, and dx max = 0.11 mm.

[0097] The dx provided above min and dx max The example values ​​are rounded to the nearest two decimal places.

[0098] Figure 5 The illustration presents a method for determining the allowable range of dx values ​​for a desired range of target detection distance L. In this case, the mirror step angle ΔMR, focal length f, travel distance k, and maximum permissible residual beam displacement d are known. BP_MAX .

[0099] The first line 510 shows the critical dx values ​​for different target detection distances. c This is calculated using equation (2).

[0100] The second line 520 shows the ideal non-zero distance dx for different values ​​of the target detection distance. ideal This is calculated using equation (3).

[0101] The third line 530 shows the minimum value of the non-zero distance dx. min The maximum residual beam displacement that meets the requirements or is permissible is calculated using equation (5).

[0102] The fourth line, 540, shows the maximum value of the non-zero distance dx. max The maximum residual beam displacement that meets the requirements or is permissible is calculated using equation (6). It can be seen that for all values ​​of the target detection distance L, the maximum value dx is... max Below the critical dx value dx c .

[0103] from Figure 5 It can be clearly seen that the minimum value of the non-zero distance decreases as the distance L increases. Similarly, the maximum value of the non-zero distance decreases as the distance L increases.

[0104] For all target detection distances within the range of target detection distances L1-L2, it is possible to determine the minimum dx1 and maximum dx2 values ​​of the non-zero distance dx falling between the third and fourth lines. Specifically, the minimum dx1 value of the non-zero distance can be calculated by processing the minimum target detection distance L using equation (5). The maximum dx2 value of the non-zero distance dx can be calculated by processing the maximum target detection distance L using equation (6).

[0105] It is evident that the lines with the minimum and maximum dx values ​​intersect at some value L. This signifies the longest possible detection distance L under given boundary conditions.

[0106] In one embodiment, the non-zero distance dx that minimizes the maximum residual offset is identified by using equation (4) (in the case of the minimum value dx). min up to the maximum value dx max Within the range), find the one used for the selected L min and L max The optimized dx value.

[0107] The optimized value of non-zero dx opt The following can be calculated: in as well as Figure 6 An alternative configuration of the optical system 650 of the first optical wireless communication device is shown.

[0108] Specifically, the lens arrangement here includes a single lens 653 positioned between the beam manipulation device 151 and the beam splitter 152. Thus, the beam splitter separates the already converged incident beam into first and second beams. This reduces the number of components required for the optical system, for example, avoiding the use of multiple lens sub-arrangements.

[0109] However, the use of a beam splitter can introduce astigmatism into the converging first beam. More specifically, the focal plane can be conceptually viewed as effectively splitting into two orthogonal focal lines. This effect is particularly pronounced if the beam splitter is a planar beam splitter (which is advantageous for minimizing or mitigating the effects of Fresnel reflections). A cube beam splitter will introduce spherical aberration, which can be corrected with a collimating lens.

[0110] Therefore, as a result of using a beam splitter, the method for determining the non-zero distance dx may be affected, especially if the goal is to generate the minimum dx for the non-zero distance dx. min and maximum dx max If it's worth it.

[0111] Effectively dividing the focal plane into two orthogonal focal lines (located at a distance between the focal lines) means that the usable area for placing position-sensitive devices should be reduced by the same amount (i.e., the same distance between the focal lines). More specifically, if the focal line closest to the lens arrangement is at position F1 = F + dF, and the second (orthogonal) focal line is at position F2 = F1 + ΔF, then dx min It should be defined relative to F2, while dx max It should be defined relative to F1.

[0112] Mathematically, this can be represented as: Where ΔF = F2 - F1, and Δdx represents dx changing from F2 + dx min The range of (L1).

[0113] The amount of astigmatism (i.e., the magnitude of ΔF) depends on the thickness of the beam splitter plate. The precise relationship can depend on, for example, the material of the beam splitter plate, such as its refractive index. Based on this understanding, suitable methods for selecting materials and thicknesses to maintain a sufficient (i.e., at least non-negative and non-zero) range of Δdx for non-zero distances dx will be apparent to those skilled in the art.

[0114] In other words, assuming the size of ΔF is less than Δdx (L1, L2), a solution for placing position-sensitive devices is available.

[0115] In some examples, the minimum value of the non-zero distance dx can be further limited or defined by part constraints (i.e., in addition to any of the methods described above).

[0116] For example, a position-sensitive device may include a dark area or region surrounding a central point, for which the position of light cannot be determined if light falls only on that dark area (i.e., the interval between the corresponding detectors of the quadrant detector). A minimum non-zero distance can be selected such that at least some light falls outside the dark area or region. For example, the minimum can be selected to be not less than 0.1 mm (e.g., in addition to any other limitations illustrated by the examples above).

[0117] For example, a quadrant detector with a width W separating each quadrant from the others will have a dimension W at the center. 2 mm 2 The dark area. For such an example, the minimum value dx of such a quadrant detector can be defined using the following equation. min,W : To avoid confusion, note that for a quadrant detector, the minimum value of the non-zero distance dx is dx.min It can be the maximum of any minimum value calculated using any of the previously described methods, such as calculated using equation (5) or equation (9).

[0118] Table 1 shows some example values ​​for parameters in the optical system according to an embodiment. The parameter values ​​represent parameters that cannot be modified (e.g., L). min L max Example values ​​of f, k, ΔMR and W, and appropriate values ​​of parameters including the ideal, minimum and maximum values ​​of the non-zero distance dx. Table 1 In any of the above examples of optical systems and / or devices utilizing an optical system, the optical system may also include a positioning system configured to facilitate controllable adjustment of the distance between the first focal plane and the position-sensitive device.

[0119] In some examples, the positioning system is partially integrated into the lens arrangement. For example, the lens arrangement may be adjustable to control its focal length (e.g., including liquid-filled lenses). This facilitates adjustment of the position of the first focal plane, and thus facilitates adjustment of the distance between the first focal plane and the position-sensitive device.

[0120] In other examples, the positioning system is configured to manipulate or change the position of the position-sensitive device relative to the lens arrangement (and thus relative to the first focal plane) by moving the position-sensitive device.

[0121] Figure 7 A working example of a portion of an optical system with positioning system 700 is shown.

[0122] The positioning system 700 can be configured to control the distance between the first focal plane and the position-sensitive device in response to at least one target detection distance of the optical system.

[0123] Therefore, the positioning system may include an actuator 710 configured to move the position of a position-sensitive device and a control system 720 configured to control the operation of the actuator. The actuator 710 may be configured or calibrated to facilitate precise control of the distance between the position-sensitive device and the first focal plane.

[0124] Actuator 710 herein includes a linear actuator, which, in the form of a worm gear, is configured to controllably adjust the position of the position-sensitive device, and thereby controllably adjust the distance between the first focal plane and the position-sensitive device. Other suitable linear actuators and / or positioning systems will be apparent to those skilled in the art, such as pistons, hydraulic devices, pneumatic devices, screw-based actuators, cam-based actuators, etc.

[0125] In some examples, the positioning system 700 includes a feedback system (not shown) configured to determine the distance between the actuator 710 and the first focal plane. This can be determined, for example, by determining the distance between the actuator 710 and the lens (arrangement). The distance between the lens arrangement and the first focal plane can be established based on the focal length associated with the lens. This facilitates easy identification of the distance dx. Any suitable distance determination tool can be used.

[0126] The control system 720 can be configured to use one or more target detection distances, employing the previously described method, to identify a value of the distance between the first focal plane and the position-sensitive device. The control system can then use the determined value to control the actuator to obtain or achieve the distance value.

[0127] For example, if the detection distance of a single target is identified, equation (3) can be applied to determine the value of the distance (other values ​​are defined by device-specific knowledge, such as stored in the memory or storage unit of an optical system or optical wireless communication device).

[0128] As another example, if two target detection distances are identified (e.g., maximum and minimum target distances), equations (5) and (6) can be used to determine the maximum and minimum values ​​of the distance dx. Specifically, the minimum target distance can be used to determine the minimum value of the distance dx, and the maximum target distance can be used to determine the maximum value of the distance dx. Any value falling between these two values ​​(e.g., the average value) can be used for the distance dx.

[0129] The target detection range (one or more) can be user-defined. Therefore, the optical system may include an input interface configured to receive a signal carrying the target detection range (one or more) defined at the user interface. This allows the user to (re)configure the optical system for a desired target detection range or range.

[0130] As another example, target detection range(s) can be determined based on a defined distance between an optical wireless communication device (carrying an optical system) and another optical wireless communication device that generates an incident beam for the optical system. This distance can be determined by a distance determination system, for example, by performing a time-of-flight measurement on the received incident beam or by performing some other mechanism for determining the distance. For instance, the distance determination system can determine the distance between the other optical wireless communication device and the optical wireless communication device by determining the difference between a timestamp carried by embedded information carried by the incident beam and the current timestamp.

[0131] More specifically, the target detection distance can be set or defined as a predetermined distance between two optical wireless communication devices.

[0132] In an alternative embodiment, the control system 720 is used to configure, adjust, or modify the position of a position-sensitive device with reduced residual beam offset (e.g., as indicated in equation (4)) without directly knowing the actual value of the target detection distance. Instead, the modification can be based on signals S(s) from one or more of the position-sensitive device as it moves. P and / or from data sensor S D The signal strength is fed back. In this way, for any detection distance L (provided that L is within a feasible range of given other system parameter values), the optimal detection configuration with minimum residual beam offset and maximum data signal strength is dynamically established.

[0133] When practicing the claimed invention, those skilled in the art can understand and implement variations of the disclosed embodiments by studying the accompanying drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality.

[0134] The mere fact that certain measures are described in mutually different dependent claims does not imply that a combination of these measures cannot be used advantageously.

[0135] If the term "suitable" is used in the claims or description, it should be noted that the term "suitable" is intended to be equivalent to the term "configured as". If the term "arrangement" is used in the claims or description, it should be noted that the term "arrangement" is intended to be equivalent to the term "system", and vice versa.

[0136] Any reference numerals in the claims should not be construed as limiting the scope.

Claims

1. An optical system (150) for generating a data signal in response to embedded information carried by an incident light beam (125), the optical system comprising: A beam manipulation device (151) is configured to controllably manipulate the direction of the incident beam; A beam splitter (152) is configured to split the incident beam into a first beam and a second beam at an angle relative to each other after being manipulated by the beam manipulation device. A position-sensitive device (154) is configured to generate a position sensing signal (S) in response to the position of the first light beam incident on the receiving surface (154A) of the position-sensitive device. P The receiving surface of the position-sensitive device is positioned to receive the first light beam. as well as A light sensing module (155) is positioned to receive the second light beam and configured to generate a data signal (S) in response to embedded information carried by the second light beam. D ), The beam manipulation device is configured to manipulate the direction of the incident beam in response to a position sensing signal generated by the position-sensitive device. The optical system is further characterized in that it includes: Lens arrangements (153, 653) are configured to focus the first beam to a first focal point located in a first focal plane (F) and to focus the second beam to a second focal point in a second focal plane. The receiving surface of the position-sensitive device is positioned at a non-zero distance (dx) from the first focal plane.

2. The optical system according to claim 1, wherein, The lens arrangement is positioned between the beam manipulation device and the beam splitter.

3. The optical system according to claim 1 or 2, wherein, The lens arrangement includes: A first lens element is arranged and positioned between the beam splitter and the position-sensitive device; and A second lens is arranged and positioned between the beam splitter and the photosensitive module.

4. The optical system according to any one of claims 1 to 3, wherein, The first focal plane is positioned between the lens arrangement and the position-sensitive device.

5. The optical system according to any one of claims 1 to 4, wherein, The non-zero distance between the first focal plane and the position-sensitive device is no greater than the value calculated by the following formula: Where f is the distance between the first focal plane and the lens arrangement, L is the target detection distance of the optical system, and k is the distance the first beam travels between the beam manipulation device and the lens arrangement.

6. The optical system according to claim 5, wherein, The non-zero distance between the first focal plane and the position-sensitive device is a value falling within ±10% of a first calculated value, wherein the first calculated value is calculated using the following formula: .

7. The optical system according to any one of claims 1 to 5, wherein, The position-sensitive device includes one or more dark areas with a width, and the non-zero distance between the first focal plane and the position-sensitive device is not less than a value calculated by the following formula: Where W is the width of one or more dark areas, and D B f is the diameter of the incident beam; and f is the distance between the first focal plane and the lens arrangement.

8. The optical system according to any one of claims 1 to 7, wherein, The light sensing module is positioned to receive the second light beam at the second focal plane.

9. The optical system according to any one of claims 1 to 8, further comprising a positioning system configured to facilitate controllable adjustment of the distance between the first focal plane and the position-sensitive device in response to at least one target detection distance of the optical system.

10. The optical system according to any one of claims 1 to 9, wherein, The beam manipulation device is a rotatable mirror.

11. The optical system according to any one of claims 1 to 10, wherein, The beam splitter is a partial transmission mirror.

12. The optical system according to any one of claims 1 to 11, wherein, The position-sensitive device is a four-quadrant photodetector.

13. The optical system according to any one of claims 1 to 12, wherein, The beam splitter is configured such that the first beam includes at least 25% of the incident beam and the second beam includes at least 25% of the incident beam.

14. An optical wireless communication device (110), comprising: The optical system (150) according to any one of claims 1 to 13; as well as A processing system (160) is configured to receive data signals and extract embedded information from the data signals.

15. An optical wireless communication system, comprising: The optical wireless communication device according to claim 14; as well as A second optical wireless communication device is configured to generate a light beam carrying embedded information and transmit the generated light beam to the optical wireless communication device, wherein the transmitted light beam serves as the incident light beam of the optical system of the optical wireless communication device.

Images