Device, method and computer program for providing control signals to a laser scanning system

Abstract

The present disclosure relates to an apparatus, a method, and a computer program for providing control signals to a laser scanning system. Examples of the present disclosure relate to an apparatus for providing control signals to an adjustable mirror in an optical system such as a laser scanning system. The optical system may be a LiDAR system or an optical coherence tomography (OCT) system or any other suitable system. The apparatus includes means for providing control signals to at least one adjustable mirror to control the movement of the at least one adjustable mirror, wherein the at least one adjustable mirror is provided within a laser scanning system. The control signal includes a multi-step signal, wherein the step width of the multi-step signal is based on half of the period of oscillation of the at least one adjustable mirror.

Description

Technical Field

[0001] Examples of the present disclosure relate to apparatuses, methods, and computer programs for providing control signals to a laser scanning system. Some relate to apparatuses, methods, and computer programs for providing control signals to one or more adjustable mirrors within a laser scanning system. Background Art

[0002] Laser scanning systems such as LiDAR and OCT systems include movable components such as one or more adjustable mirrors. When a control signal is provided to the movable component, this can result in a transient response or ringing. This ringing can have an adverse effect on the accuracy with which the laser scanning system can operate. Summary of the Invention

[0003] According to various but not all examples of the present disclosure, there is provided an apparatus including components for:

[0004] providing a control signal to at least one adjustable mirror to control movement of the at least one adjustable mirror, wherein the at least one adjustable mirror is provided within a laser scanning system; wherein

[0005] the control signal includes a multi-step signal, wherein the step width of the multi-step signal is based on half of the oscillation period of at least one adjustable mirror.

[0006] The components can be used to determine the oscillation period of at least one adjustable mirror and to use the determined period to control the step width of the control signal.

[0007] The period of oscillation can be determined based on a measurement of the mechanical resonance of at least one adjustable mirror.

[0008] The control signal can include more than two steps.

[0009] The components can be used to form the control signal based on a multi-pulse drive signal.

[0010] The multi-pulse drive signal can include a pulse width modulation drive signal.

[0011] The step width of the control signal can be substantially half of the oscillation period of at least one adjustable mirror.

[0012] The components can be used to adjust at least one of the following using a feedback loop: the step size of the control signal, the step width of the control signal.

[0013] The components can be used to adjust one or more step widths of the control signal to one or more other step widths of the control signal, respectively.

[0014] The component can be used to filter a control signal before it is provided to at least one adjustable mirror.

[0015] The control signal can be provided to one or more actuators of at least one adjustable mirror to control the movement of the at least one adjustable mirror.

[0016] The movement of the at least one adjustable mirror can enable the laser scanning system to perform linear scanning.

[0017] The at least one adjustable mirror includes a microelectromechanical system mirror.

[0018] The laser can include collimated light.

[0019] According to various but not all examples of the present disclosure, an apparatus can be provided that includes at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to at least perform:

[0020] Providing a control signal to at least one adjustable mirror to control the movement of the at least one adjustable mirror, wherein the at least one adjustable mirror is provided within a laser scanning system; wherein

[0021] The control signal includes a multi-step signal, wherein the step width of the multi-step signal is based on half of the oscillation period of the at least one adjustable mirror.

[0022] According to various but not all examples of the present disclosure, an optical coherence tomography device can be provided that includes the apparatus described herein.

[0023] According to various but not all examples of the present disclosure, a lidar device can be provided that includes the apparatus described herein.

[0024] According to various but not all examples of the present disclosure, a method can be provided that includes:

[0025] Providing a control signal to at least one adjustable mirror to control the movement of the at least one adjustable mirror, wherein the at least one adjustable mirror is provided within a laser scanning system; wherein

[0026] The control signal includes a multi-step signal, wherein the step width of the multi-step signal is based on half of the oscillation period of the at least one adjustable mirror.

[0027] According to various but not all examples of the present disclosure, a computer program can be provided that includes computer program instructions that, when executed by a processing circuit, cause:

[0028] Providing a control signal to at least one adjustable mirror to control the movement of the at least one adjustable mirror, wherein the at least one adjustable mirror is provided within a laser scanning system; wherein

[0029] The control signal includes a multi-step signal, wherein the step width of the multi-step signal is based on half of the oscillation period of the at least one adjustable mirror. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Some examples will be described with reference to the accompanying drawings:

[0031] Figure 1 An example system is shown;

[0032] Figure 2 An example device is shown;

[0033] Figure 3 An example method is shown;

[0034] Figure 4 An example method is shown;

[0035] Figure 5A 、 Figure 5B and Figure 5C Example control signals are shown;

[0036] Figure 6 An example feedback loop is shown; and

[0037] Figure 7 Example results are shown. DETAILED DESCRIPTION

[0038] Examples of the present disclosure relate to an apparatus for providing a control signal to an adjustable mirror in an optical system such as a laser scanning system. The optical system can be a LiDAR system or an optical coherence tomography (OCT) system or any other suitable system. The control signal is configured to reduce ringing or transient response oscillations. Reduction of ringing can enable faster and more efficient linear scanning.

[0039] Figure 1 An example system 101 in which examples of the present disclosure can be implemented is shown. The example system 101 can be a LiDAR system or an OCT system or any other system that uses a scanning laser or other collimated light source to obtain an image or other information from a sample 111. LiDAR systems and OCT systems can be provided in consumer devices such as smartphones or tablets. In some examples, LiDAR systems or OCT systems can be provided in other types of devices, such as medical imaging devices, vehicles, or any other suitable type of device.

[0040] Sample 111 may include any object or a part of an object to be scanned by system 101. The type of sample 111 being used may depend on the type of system 101 being used. For example, if system 101 is an OCT system, sample 111 may include a part of a subject's body, and a laser may be used to obtain an image or other information from the subject's body. If system 101 is a LiDAR system, sample 111 may be any object located in the surrounding environment of system 101. For example, if the LiDAR system is used in a vehicle, sample 111 may be other vehicles or pedestrians or other objects around the vehicle.

[0041] Figure 1 The example system 101 shown includes a light source 103, at least one adjustable mirror 107, one or more optical components 109, at least one detector 113, and a device 115. Device 115 may be configured to control system 101. It should be understood that Figure 1 only the components mentioned in the following description are shown, and system 101 may include additional components in the examples of the present disclosure.

[0042] Light source 103 may include a laser source configured to provide a laser beam 105. Laser source 103 may be configured to provide a laser beam 105 of any wavelength suitable for scanning sample 111. The wavelength of the light used may depend on the type of sample 111 to be scanned, the type of system 101 provided, or any other suitable factors. Collimated light may be provided in other examples.

[0043] System 101 is configured such that when system 101 is in use, the laser beam 105 from light source 103 is incident on at least one adjustable mirror 107. A light guide may be used to provide the laser 105 from light source 103 to adjustable mirror 107.

[0044] At least one adjustable mirror 107 may include any reflective or partially reflective component. Adjustable mirror 107 may include a microelectromechanical system (MEMS) mirror, a thermally controlled mirror, or any other suitable type of reflective surface.

[0045] At least one adjustable mirror 107 is located within system 101 such that at least some of the laser 105 reflected by at least one adjustable mirror 107 when system 101 is in use is directed towards sample 111 and thus can be used for scanning sample 111.

[0046] Adjustable mirror 107 is adjustable in that the position of adjustable mirror 107 can be adjusted so that the laser 105 can be directed to different parts of sample 111. Adjustable mirror 107 may be connected to one or more actuators to allow adjustable mirror 107 to move. The actuators may include one or more springs or any other suitable components.

[0047] Adjustment of the adjustable mirror 107 may include changing the angular position of the adjustable mirror 107 within the system 101 and / or any other suitable positional change. The adjustable mirror 107 may be configured to tilt within a range of different angular positions.

[0048] Movement of the adjustable mirror 107 may enable different portions of the sample 111 to be scanned. The position of the adjustable mirror 107 may be controlled by a control signal 121 such that different portions of the sample 111 can be scanned. The adjustable mirror may be configured to direct the laser 105 to different portions of the sample 111. The adjustable mirror 107 may be configured to allow linear scanning of the sample 111.

[0049] The device 115 is configured to provide the control signal 121 to the adjustable mirror 107. The device 115 may include a controller or any other suitable component. The device 115 may include a processor 117 and a memory 119. An example of the device 115 is shown and described below. Figure 2 is shown and described below.

[0050] The control signal 121 includes a signal that applies a force or acceleration to the actuator of the adjustable mirror 107. The control signal 121 may include a multi-step signal, where the step width of the multi-step signal is based on half of the oscillation period of the adjustable mirror 107. The use of the multi-step control signal 121 can reduce the ringing of the adjustable mirror 107 and allow for fast linear scanning.

[0051] The system 101 is configured such that the laser 105 reflected from the sample 111 is directed to the detector 113. The detector 113 may include any component that can be configured to detect the laser 105 and thus enable information to be obtained from the sample 111.

[0052] The system 101 may further include one or more optical components 109. The optical components 109 may include one or more components for directing at least a portion of the laser 105 reflected from the adjustable mirror 107 to the sample 111 in order to support scanning of the sample 111.

[0053] One or more optical components 109 may include any component that can be configured to direct the laser from the sample 111 to the detector 113. The optical components 109 may include one or more optical devices such as one or more fixed mirrors, one or more dichroic mirrors, one or more controllable apertures, optical lenses, and / or any other suitable components.

[0054] Figure 2FIG. 0 shows an example apparatus 115 that can be used to provide a control signal 121 to an adjustable mirror 107. The control signal 121 can apply a force to an actuator of the adjustable mirror 107 to control the position of the adjustable mirror 107. The control signal 121 can be configured to allow a linear scan of the sample 111 while reducing ringing of the adjustable mirror 107.

[0055] In Figure 2 the example, the apparatus 115 includes a controller 203. The controller 203 can be configured to control the position of the adjustable mirror 107. In some examples, the controller 203 can be configured to control other components of the system 101. In Figure 2 the example, the implementation of the controller 203 can be a controller circuit. In some examples, the controller 203 can be implemented solely in hardware, with certain aspects of software including firmware alone, or can be a combination of hardware and software (including firmware).

[0056] As Figure 2 shown, the controller 203 can be implemented using instructions that enable hardware functionality, e.g., by using executable instructions of a computer program 205 stored in a general - purpose or special - purpose processor 117 that can be stored on a computer - readable storage medium (disk, memory, etc.) to be executed by such a processor 117.

[0057] The processor 117 is configured to read from and write to the memory 119. The processor 117 can also include an output interface through which data and / or commands are output by the processor 117, and an input interface through which data and / or commands are input to the processor 117.

[0058] The memory 119 is configured to store a computer program 205 including computer program instructions (computer program code 207) that control the operation of the apparatus 203 when loaded into the processor 117. The computer program instructions of the computer program 205 provide the logic and routines that enable the apparatus 115 to perform Figure 3 and Figure 4 the methods shown. The processor 117 can load and execute the computer program 205 by reading from the memory 119.

[0059] Thus, the apparatus 115 includes: at least one processor 117; and at least one memory 119 including computer program code 207, the at least one memory 119 and the computer program code 207 being configured to, together with the at least one processor 117, cause the apparatus 115 to at least perform: providing a control signal to at least one adjustable mirror to control the movement of the at least one adjustable mirror, where the at least one adjustable mirror is provided within a laser scanning system; where

[0060] The control signal includes a multi-step signal, where the step width of the multi-step signal is based on half of the period of oscillation of at least one adjustable mirror.

[0061] As Figure 2 shown, the computer program 205 can reach the device 115 through any suitable transmission mechanism 201. The transmission mechanism 201 can be, for example, a machine-readable medium, a computer-readable medium, a non-transitory computer-readable storage medium, a computer program product, a storage device, a recording medium such as a compact disc read-only memory (CD-ROM) or a digital versatile disc (DVD), or a solid-state memory, an article of manufacture including or tangibly embodying the computer program 205. The transmission mechanism can be a signal configured to reliably transmit the computer program 205. The device 115 can propagate or transmit the computer program 205 as a computer data signal. In some examples, the computer program 205 can be transmitted to the device 115 using a wireless protocol such as Bluetooth, Bluetooth Low Energy, Bluetooth Smart, 6LoWPan (Low-Power Wireless Personal Area Network using IPv6), ZigBee, Ant+, Near Field Communication (NFC), Radio Frequency Identification, Wireless Local Area Network (Wireless LAN), or any other suitable protocol).

[0062] The computer program 205 includes computer program instructions for causing the device 115 to at least perform the following operations:

[0063] Providing a control signal to at least one adjustable mirror to control the movement of at least one adjustable mirror, where at least one adjustable mirror is provided within a laser scanning system; where

[0064] The control signal includes a multi-step signal, where the step width of the multi-step signal is based on half of the period of oscillation of at least one adjustable mirror.

[0065] The computer program instructions can be contained in the computer program 205, a non-transitory computer-readable medium, a computer program product, a machine-readable medium. In some but not all examples, the computer program instructions can be distributed over more than one computer program 205.

[0066] Although the memory 119 is shown as a single component / circuit, it can be implemented as one or more separate components / circuits, some or all of which can be integrated / removed and / or can provide permanent / semi-permanent / dynamic / cache storage.

[0067] Although the processor 117 is shown as a single component / circuit, it can be implemented as one or more separate components / circuits, some or all of which can be integrated / removed. The processor 117 can be a single-core or multi-core processor.

[0068] References to "computer-readable storage media", "computer program products", "tangibly embodied computer programs", etc. or "controllers", "computers", "processors", etc. should be understood to include not only computers with different architectures, such as single / multi-processor architectures and sequential (von Neumann) / parallel architectures, but also dedicated circuits such as field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), signal processing devices, and other processing circuits. References to computer programs, instructions, code, etc. should be understood to include software or firmware for programmable processors, such as programmable content for hardware devices, whether instructions for a processor or configuration settings for fixed function devices, gate arrays, or programmable logic devices, etc.

[0069] The term "circuit" as used in this application may refer to one or more or all of the following:

[0070] (a) A pure hardware circuit implementation (such as implemented only in analog and / or digital circuits) and

[0071] (b) A combination of hardware circuits and software, for example (as appropriate):

[0072] (i) A combination of analog and / or digital hardware circuits and software / firmware, and

[0073] (ii) Any part of a hardware processor with software (including a digital signal processor), software, and memory that work together to cause a device such as a mobile phone or server to perform various functions, and

[0074] (c) A hardware circuit and / or processor such as a microprocessor or a part of a microprocessor that requires software (such as firmware) to operate, but the software may not be present when not required to operate.

[0075] This definition of circuit applies to all uses of the term in this application, including any claims. As a further example, as used in this application, the term circuit also includes an implementation of only a hardware circuit or a processor and its (or its) attendant software and / or firmware. The term circuit also includes, for example, if applicable to a particular claim element, a baseband integrated circuit for a mobile device or a similar integrated circuit in a server, a cellular network device, or other computing or network device.

[0076] Figure 3 and Figure 4 The boxes shown in and may represent method steps and / or code segments in computer program 205. The specification of a particular order of the boxes does not necessarily imply a required or preferred order for the boxes, and the order and arrangement of the boxes may vary. Additionally, some boxes may be omitted.

[0077] Figure 3An example method for designing or obtaining a control signal 121 for controlling the tunable mirror 107 is shown. This method can be performed by Figure 1 and Figure 2 the device 115 shown.

[0078] The method includes, at block 301, measuring the mechanical resonance of the tunable mirror 107. Any suitable component can be used to measure the mechanical resonance of the tunable mirror 107, such as a position sensor and / or an oscillometer.

[0079] The mechanical resonance can be determined by the physical properties of the mirror 107 and the actuator of the mirror. For example, the factors determining the mechanical resonance can include the size, shape, and weight of the tunable mirror 107, as well as the stiffness and length of the spring or other components used as the actuator.

[0080] The tunable mirror 107 and the actuator of the tunable mirror can be designed to have a specific resonance. However, there may be some deviation from the designed resonance in the actual resonance. For example, manufacturing tolerances may result in a different actual mechanical resonance from the designed manufacturing tolerances. Therefore, the actual mechanical resonance can be determined by measuring the oscillation of the tunable mirror 107.

[0081] The mechanical resonance gives the oscillation period of the tunable mirror 107. This period can be used to determine the step width of the control signal 121. In the example of the present disclosure, the step width of the control signal 121 is based on the half - period of the oscillation of the tunable mirror 107. The half - period can be determined from the measured mechanical resonance.

[0082] At block 303, the method includes designing the steps of the control signal 121. The steps of the control signal 121 are designed to apply an acceleration or force to the actuator of the tunable mirror during the measured half - period.

[0083] The control signal 121 is designed to have more than two steps. The steps are designed to have a step width based on at least the half - period of the oscillation of the tunable mirror 107. The step width determines the duration of the control signal 121 having a given parameter. The parameter can be voltage, current, or power. In some examples, the duration of the step width is equal to or substantially equal to half of the period of the tunable mirror 107. In some examples, the step width can be based on a multiple of the half - period of the tunable mirror, for example, the step width can include an odd integer multiple of the half - period of the tunable mirror 107.

[0084] The step width of the control signal can be within a given tolerance range of the half - period determined by the mechanical resonance measured at block 301. In some examples, the step width can be within a tolerance range of 2% of the period determined by the mechanical resonance. Other ranges can be used in other examples of the present disclosure.

[0085] In the example of the present disclosure, each step in the multi - step signal can have the same step width.

[0086] In examples of the present disclosure, different steps within control signal 121 may have different amplitudes. In such examples, at least one step may have a first amplitude and at least one second step may have a second different amplitude. The amplitude of a step includes the voltage difference between adjacent steps of control signal 121. The amplitude may include an increase in a control signal parameter or a decrease in a control signal parameter. For example, the amplitude may include an increase in voltage or a decrease in voltage.

[0087] In some examples, the steps of control signal 121 may be formed based on a multi-pulse drive signal. The multi-pulse drive signal may include a pulse width modulation drive signal or any other suitable type of signal.

[0088] At block 305, the response of tunable mirror 107 to control signal 121 designed at block 303 is measured. The response may be measured by measuring the scan linearity and velocity uniformity of tunable mirror 107 in response to the control signal or by measuring any other suitable parameter.

[0089] The measured response is then provided back to device 115 to cause block 303 to be repeated. This allows the step size and / or step width of the control signal to be adjusted based on the measured response. The use of the feedback loop and blocks 303 and 305 may be repeated a suitable number of times. In some examples, the feedback loop and blocks 303 and 305 may be reused until the measured response reaches a threshold parameter.

[0090] Figure 4 Another example method in accordance with an example of the present disclosure is shown. The method may be performed by Figure 1 and Figure 2 shown device 115. In some examples, Figure 4 the method may be performed in combination with Figure 3 the method. In other examples, Figure 3 the method may be performed and the control signal may be stored in memory 119 of device 115 so that Figure 4 the method may be performed at a later time.

[0091] The method includes, at block 401, providing control signal 121 to at least one tunable mirror 107 to control the movement of at least one tunable mirror 107. At least one tunable mirror 107 is disposed within laser scanning system 101, such as Figure 1 shown system 101.

[0092] Control signal 121 includes a multi-step signal, wherein the step width of the multi-steps is based on half of the oscillation period of at least one tunable mirror 107. Control signal 121 may use Figure 3Designed or obtained by the method shown or any other suitable method. The control signal 121 can be used to allow linear scanning of the sample 111. The use of steps in the control signal 121 reduces the ringing of the tunable mirror and thus allows for faster linear scanning.

[0093] Figures 5A to 5C An example control signal 121 is shown.

[0094] Figure 5A An example where the control signal is not a multi-step control signal 121 is shown. In this example, a linear ramp signal is used. In this example, the voltage of the control signal 121 increases linearly or substantially linearly over the duration of the control signal 121.

[0095] Curve 501 shows the movement of the tunable mirror 107 in response to the control signal 121. Figure 5A It is shown that the linear ramp signal causes a ringing response. In this example, the ringing response lasts for several resonance lifetimes. This may be the case if the linear ramp is used at a frequency close to the resonance frequency of the tunable mirror 107.

[0096] Figure 5B A control signal 121 including a multi-step signal is shown, where the step width of the multi-step signal is based on half of the oscillation period 503 of at least one tunable mirror 107. The steps of the control signal 121 are designed to apply acceleration or force to the actuator of the tunable mirror 107 to move the tunable mirror 107 at the measured half-period.

[0097] Figures 5A to 5C The dashed line shown in shows the half-period of the oscillation of the tunable mirror 107. Any suitable component or process can be used to determine the half-period of the oscillation of the mirror 107, such as a position sensor and / or an oscillometer.

[0098] Figure 5B The control signal 121 shown can be obtained using Figure 3 the process shown or any other suitable process.

[0099] As Figure 5B shown, the multi-step control signal 121 includes a plurality of steps 505. The multi-step control signal 121 includes more than two steps 505. In Figure 5B the example, the multi-step control signal 121 includes eight steps 505. In other examples of the present disclosure, other numbers of steps 505 can be used.

[0100] In Figure 5B the example, each step 505 has the same width. The width of each step 505 is half a period or substantially half a period of the oscillation of the tunable mirror 107. The half-period can be based on the measured oscillation of the tunable mirror 107.

[0101] The amplitude of the steps 505 can be adjusted to reduce ringing or other unwanted movement of the adjustable mirror 107. In some examples, the amplitude of the steps 505 can be adjusted to minimize or substantially minimize ringing of the adjustable mirror 107.

[0102] In Figure 5B the example, different steps within the control signal 121 have different amplitudes. In Figure 5B the example, each step 505 has a different amplitude. In other examples, one or more of the steps 505 within the control signal 121 can have a first amplitude, and one or more of the steps 505 can have a different second amplitude.

[0103] The control signal 121 can be configured such that the amplitudes of the steps 505 can be adjusted independently of each other. For example, the amplitude of a first step 505 can be adjusted without adjusting the amplitudes of other steps 505 within the control signal 121.

[0104] In response to Figure 5B the multi-step control signal 121 shown, the motion curve 501 of the adjustable mirror 107 shows significantly less ringing than the motion of the adjustable mirror 107 in response to Figure 5A the linear ramp signal shown.

[0105] Figure 5C Another example control signal 121 is shown. In this example Figure 5B the multi-step control signal 121 shown has been filtered using a low-pass filter. The resulting control signal 121 includes a smoothed pulse shape, where the width of the pulse is based on the half-period of the oscillation of the adjustable mirror 107.

[0106] Higher frequencies are removed from the control signal 121 using a low-pass filter. This eliminates more unwanted oscillations of the adjustable mirror 107. Figure 5C The motion curve 501 of the adjustable mirror 107 shown in Figure 5B is more linear and includes fewer oscillations than the corresponding curve in

[0107] Figure 6 An example feedback loop 601 that can be used to design the control signal 121 is shown. The feedback loop 601 can be implemented using Figure 1 and Figure 2 the device 115 shown or using any other suitable components.

[0108] In block 603, the feedback loop includes obtaining the resonant steps 505 of the control signal 121. The steps 505 of the control signal 121 can be determined based on the mechanical resonance of the adjustable mirror 107. The output of block 603 includes a step signal 605.

[0109] The stepped signal 605 is then provided to a low-pass filter 607 to provide a smoothed signal 609.

[0110] The smoothed signal 609 is provided to a pulse-width modulation (PWM) conversion module 611 to form a control signal 121 provided to the tunable mirror 107 based on a multi-pulse drive signal. In this example, the multi-pulse drive signal includes a pulse-width modulated drive signal.

[0111] The control signal 121 is then provided to the tunable mirror 107 in the system 101 to control the movement of the tunable mirror 107.

[0112] One or more position sensors 613 can be used to determine the position of the tunable mirror 107 in response to the control signal. One or more position sensors 613 can include any suitable components. In some examples, one or more position sensors 613 can include an image sensor, such as a complementary metal oxide semiconductor sensor or any other suitable component. In some examples, one or more position sensors 613 can include an oscillometer and / or any other suitable component.

[0113] One or more position sensors 613 provide an output signal 615 including an indication of the position of the tunable mirror 107. The indication of the position of the tunable mirror 107 provides information related to ringing or other unwanted motion of the tunable mirror 107.

[0114] The output signal 615 including the indication of the position of the tunable mirror is provided to a feedback correction module 617. The feedback correction module 617 uses the information related to ringing or other desired motion of the tunable mirror 107 to determine how the resonance step should be adjusted.

[0115] Any suitable parameter of the resonance step can be adjusted in the examples of the present disclosure. For example, the step width can be adjusted and / or the amplitude of one or more steps 505 can be adjusted. The feedback correction module 617 can be configured such that the step 505 is adjusted independently of other steps 505 within the control signal 121. For example, the amplitude of the first step 505 can be controlled without adjusting the amplitude of the second step 505 and / or other steps within the control signal 121.

[0116] Figure 7 Example results in accordance with examples of the present disclosure are shown. Figure 7 Three different curves showing results obtained using three different control signals 121 are shown. In each curve, the dashed line shows the control signal 121 provided to the tunable mirror 107, while the solid line shows the corresponding deflection of the tunable mirror 107. The deflection of the tunable mirror can be measured using a position sensor or any other suitable component.

[0117] In obtainingFigure 7 In system 101 with the data of curves 701, 703, 705 in , the tunable mirror 107 is a microelectromechanical system mirror with a mechanical resonance frequency of approximately 900 hertz.

[0118] In the first curve 701, the control signal 121 includes a linear ramp signal 121. The control signal 121 has a scan speed of 250 hertz. This results in ringing or unnecessary movement of the tunable mirror 107. This unnecessary movement will affect the driving speed of the tunable mirror 107 and thus limit the speed at which system 101 can obtain information from the sample 111.

[0119] In the second curve 703, the control signal includes a multi-step signal based on the half-period of the oscillation of the tunable mirror 107. The steps are designed to apply acceleration or force to the actuator of the tunable mirror 107 to move the tunable mirror 107 at the measured half-period.

[0120] The use of the multi-step signal reduces the ringing or other unnecessary movement of the tunable mirror 107. Curve 703 shows that the multi-step signal provides a linear or substantially linear forward scan. This is shown within a time period of 2 - 4 ms. This provides an improved scan of the sample 111. Compared with the linear ramp signal, this can allow for a faster linear scan of the sample 111.

[0121] In the third curve 705, the control signal 121 includes a filtered multi-step signal. The filter used can include any suitable low-pass filter. Filtering of the multi-step signal removes the high-frequency components and provides a smoother movement of the tunable mirror with less deflection and / or smaller deflection compared to using an unfiltered multi-step signal.

[0122] In Figure 7 the example of , curve 705 shows that the filtered multi-step signal provides a linear or substantially linear forward scan and a linear or substantially linear backscan. The backscan is shown between 0 - 2 ms and 4 - 7 ms.

[0123] Examples of the present disclosure thus enable the control signal 121 to be provided to the tunable mirror 107 of the scanning system 101. The control signal 121 drives the tunable mirror 107 to provide a smooth movement of the tunable mirror. This smooth movement enables a high-quality image of the sample 111 to be obtained even at high scan speeds.

[0124] As used herein, the term "comprising" has an inclusive rather than an exclusive meaning. That is, referring to X that comprises Y means that X can include only one Y or can include more than one Y. If it is intended to use "comprising" with an exclusive meaning, it is made clear in the context by referring to "comprising only one..." or by using "consisting of".

[0125] In this specification, various examples have been referred to. The description of a feature or function related to an example indicates the presence of those features or functions in that example. The terms "example" or "for example" or "able to" or "may" used in the text indicate that, whether explicitly stated or not, such a feature or function exists at least in the described example, whether described as an example or not, and they may but do not necessarily exist in some or all other examples. Thus, "example", "for example", "able to" or "may" refer to a particular example within a class of examples. The attributes of an instance may be only the attributes of that instance, or may be the attributes of the class or a subclass of the class, including some but not all instances within the class. Thus, it is implicitly disclosed that a feature described with reference to one example rather than another can, where possible, be used as part of a working combination in that other example, but does not necessarily have to be used in that other example.

[0126] Although examples have been described with reference to various examples in the preceding paragraphs, it should be understood that the given examples can be modified without departing from the scope of the claims.

[0127] In addition to the combinations explicitly described above, the features described in the foregoing specification can be used in combination.

[0128] It is explicitly stated that features in different examples (e.g., different methods in different flowcharts) can be combined.

[0129] Although functions have been described with reference to certain features, these functions can be performed by other features, whether described or not.

[0130] Although features have been described with reference to certain examples, these features can also exist in other examples, whether described or not.

[0131] The terms "a" or "the" used herein have an inclusive rather than an exclusive meaning. That is, unless the context clearly indicates the contrary, any reference to X that includes a / the Y means that X may include only one Y or may include more than one Y. If an exclusive meaning of "a" or "the" is intended, it should be clearly stated in the context. In some cases, the use of "at least one" or "one or more" can be used to emphasize the inclusive meaning, but the absence of these terms should not be taken as inferring any exclusive meaning.

[0132] The presence of a feature (or combination of features) in a claim refers to the feature or combination of features itself, and also to features (equivalent features) that achieve substantially the same technical effect. Equivalent features include, for example, variant features and achieve substantially the same result in substantially the same way. Equivalent features include, for example, features that perform substantially the same function in substantially the same way to achieve substantially the same result.

[0133] In this specification, various examples have been referred to that use adjectives or adjective phrases to describe example features. Such descriptions of example features indicate that the feature is exactly the same as described in some examples and substantially the same as described in other examples.

[0134] Although efforts have been made in the foregoing specification to draw attention to those features that are considered important, it should be understood that the applicant may seek protection by means of the claims for any patentable feature or combination of features mentioned above and / or shown in the drawings, whether or not they have been emphasized.

Claims

1. An apparatus for providing a signal, comprising: at least one processor, and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured to, when executed by the at least one processor, cause the apparatus to at least: provide a control signal to at least one adjustable mirror to control movement of the at least one adjustable mirror, wherein the at least one adjustable mirror is provided within a laser scanning system; wherein the control signal includes a multi-step signal, wherein consecutive step widths of the multi-step signal are based on half of a period of mechanical resonance of the at least one adjustable mirror, wherein: physical characteristics of the at least one adjustable mirror for determining the period of the mechanical resonance include: the size, shape, and weight of the at least one adjustable mirror, further physical characteristics of one or more actuators of the at least one adjustable mirror for determining the period of the mechanical resonance include: the stiffness and length of the one or more actuators, and the multi-step signal is configured to reduce ringing of the at least one adjustable mirror; and filter the control signal before the control signal is provided to the at least one adjustable mirror.

2. The apparatus according to claim 1, wherein the computer program code and the at least one processor are further configured to cause the apparatus to: determine the period of the mechanical resonance of the at least one adjustable mirror; and use the determined period to control the step width of the control signal.

3. The apparatus according to claim 2, wherein the period of the mechanical resonance is determined based on a measurement of mechanical resonance of the at least one adjustable mirror.

4. The apparatus according to claim 1, wherein the control signal includes more than two steps.

5. The apparatus according to claim 1, wherein the computer program code and the at least one processor are further configured to cause the apparatus to: form the control signal based on a multi-pulse drive signal.

6. The apparatus according to claim 5, wherein the multi-pulse drive signal includes a pulse width modulation drive signal.

7. The apparatus according to claim 1, wherein the step width of the control signal is half of the period of the mechanical resonance of the at least one adjustable mirror.

8. The apparatus according to claim 1, wherein the computer program code and the at least one processor are further configured to cause the apparatus to: use a feedback loop to adjust at least one of: the step size of the control signal, or the step width of the control signal.

9. The apparatus according to claim 8, wherein the computer program code and the at least one processor are further configured to cause the apparatus to: individually adjust one or more step widths of the control signal to one or more other step widths of the control signal.

10. The apparatus according to claim 1, wherein based on the movement of the at least one adjustable mirror, the laser scanning system is configured to perform a linear scan.

11. The apparatus according to claim 1, wherein the laser includes collimated light.

12. The device according to claim 1, wherein the device is an optical coherence tomography device.

13. The device according to claim 1, wherein the device is a LiDAR device.

14. The device according to claim 1, wherein the adjustable mirror comprises at least one of the following: a microelectromechanical system (MEMS) mirror or a thermally controlled mirror.

15. The device according to claim 1, wherein consecutive steps in the multi-step signal have a width based on a half period of the mechanical resonance.

16. The device according to claim 1, wherein the step width of the multi-step signal is based on half of the period of the ringing oscillation of the at least one adjustable mirror.

17. A method of providing a signal, comprising: providing a control signal to at least one adjustable mirror to control movement of the at least one adjustable mirror, wherein the at least one adjustable mirror is provided within a laser scanning system; wherein the control signal comprises a multi-step signal, wherein consecutive step widths of the multi-step signal are based on half of the period of the mechanical resonance of the at least one adjustable mirror, wherein: determining physical characteristics of the at least one adjustable mirror for the period of the mechanical resonance comprises: the size, shape, and weight of the at least one adjustable mirror, further determining physical characteristics of one or more actuators of the at least one adjustable mirror for the period of the mechanical resonance comprises: the stiffness and length of the one or more actuators, and the multi-step signal is configured to reduce ringing of the at least one adjustable mirror; and filtering the control signal before the control signal is provided to the at least one adjustable mirror.

18. A non-transitory computer-readable medium comprising program instructions stored thereon, the program instructions for causing a device to at least perform the following: providing a control signal to at least one adjustable mirror to control movement of the at least one adjustable mirror, wherein the at least one adjustable mirror is provided within a laser scanning system; wherein the control signal comprises a multi-step signal, wherein consecutive step widths of the multi-step signal are based on half of the period of the mechanical resonance of the at least one adjustable mirror, wherein: determining physical characteristics of the at least one adjustable mirror for the period of the mechanical resonance comprises: the size, shape, and weight of the at least one adjustable mirror, further determining physical characteristics of one or more actuators of the at least one adjustable mirror for the period of the mechanical resonance comprises: the stiffness and length of the one or more actuators, and the multi-step signal is configured to reduce ringing of the at least one adjustable mirror; and filtering the control signal before the control signal is provided to the at least one adjustable mirror.

19. The non-transitory computer-readable medium according to claim 18, wherein consecutive steps of the multi-step signal have a width based on a half period of the mechanical resonance.

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