Optical sensing system
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- VOXELSENSORS SRL
- Filing Date
- 2023-06-26
- Publication Date
- 2026-06-26
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to an optical sensing system. In particular, the present invention relates to an optical sensing system for efficient optical sensing.
Background Art
[0002] Optical scanning sensing systems are used in various applications. These systems rely on scanning structures or lines on a scene and detecting the depth of objects within the scene based thereon. One of the important parameters of such a system is the distance range within which such a system operates. It is desirable for such an optical sensing system to be able to simultaneously acquire information on both nearby and distant objects from the sensor. While maximizing the distance range, the power consumption of the system must be kept optimal. For example, maximizing the distance range should not lead to an increase in power consumption.
[0003] Another requirement for such a system is to operate in different environments with different light amounts, such as a dark room or during the day.
[0004] Therefore, there is a need for an optical scanning system that can be adjusted according to the distance of an object within a scene and / or the intensity of light in the system, and that has simultaneously optimized power consumption.
[0005] The present invention aims to partially solve the above problems.
Summary of the Invention
[0006] An object of an embodiment of the present invention is to provide an efficient optical sensing system. The above object is achieved by the system and method according to the present invention.
[0007] In a first aspect, the present invention relates to an optical sensing system for efficient optical sensing. The optical sensing system includes at least one optical sensor, an optical system capable of generating an image of a scene on the optical sensor, at least one light source, scanning means adapted to scan a light beam from the light source along a trajectory over the scene, and a control unit. The control unit is adapted to vary the output optical power of the light source between at least a first predetermined value and a second predetermined value higher than the first predetermined value.
[0008] An advantage of an embodiment of the present invention is that an optical sensing system with high power efficiency can be obtained.
[0009] An advantage of an embodiment of the present invention is that it can identify not only points defining an object far from the optical sensor but also points defining an object close to the optical sensor.
[0010] An advantage of an embodiment of the present invention is that a high-speed sensing system can be obtained by obtaining information on both an object far from the optical sensor and an object close to the optical sensor.
[0011] An advantage of an embodiment of the present invention is that the second predetermined value corresponds to an object far from the optical sensor and the first predetermined value corresponds to an object close to the optical sensor.
[0012] An advantage of an embodiment of the present invention is that information regarding an object in the scene can be obtained from only a partial scan of the beam from the light source over the scene.
[0013] An advantage of an embodiment of the present invention is that a high dynamic range can be obtained.
[0014] There is an advantage that the spatial integrity of the projected structure is maintained over a wider distance and object albedo range. In an optical system that images an optical structure such as a spot, secondary signals such as unwanted signals such as scattering, glare, flare, crosstalk, etc. in the optical path, optical artifacts, etc. generally scale linearly with respect to the desired signal. It is desirable to suppress these secondary signals and / or artifacts below a certain detection threshold.
[0015] An advantage of an embodiment of the present invention is that the secondary signal and / or artifact is below a certain detection threshold and the signal maximizes the amount or number of samples within a desired range.
[0016] A preferred embodiment of the first aspect of the present invention includes one or more suitable combinations of the following features.
[0017] The optical sensor has a sampling frequency, and the output optical power of the light source is preferably changed or modulated between the first predetermined value and the second predetermined value at a speed of at most the sampling frequency.
[0018] An advantage of an embodiment of the present invention is that the power required for scanning the scene is reduced. An advantage of an embodiment of the present invention is that a high-speed sensing system can be obtained by obtaining information on both an object far from the optical sensor and an object close to the optical sensor while maintaining good resolution.
[0019] The optical sensing system preferably has a processing unit, the processing unit can estimate the power level of a reflected signal reflected by at least one object in the scene and received by the optical sensor, and the processing unit can adjust the control unit to change the output optical power of the light source (for example, between the first predetermined value and the second predetermined value) based on the power level of the reflected signal.
[0020] Preferably, the processing unit can estimate the distance between the optical sensor and a point of the at least one object in the scene along the trajectory, and the processing unit can adjust the control unit to change the output optical power of the light source based on the distance.
[0021] Preferably, the processing unit can estimate the spot size of the reflection signal, and the processing unit can adjust the control unit to change the output optical power of the light source based on the spot size.
[0022] Advantages of embodiments of the present invention are that a highly power-efficient system can be obtained by optimizing the output optical power level according to the power level of the reflection signal and / or according to the distance of the object from the optical sensor and / or according to the spot size. An advantage of embodiments of the present invention is that it is simple to adjust the output optical power of the light source based on the power level and / or the distance and / or the spot size of the reflection signal. It is an advantage of embodiments of the present invention that the distance can be estimated by triangulating a point of the at least one object in the scene detected by the optical sensor with data of the emitted light of the at least one light source.
[0023] Preferably, the output optical power is changed from the second predetermined value to the first predetermined value.
[0024] Advantages of embodiments of the present invention are that the output optical power is reduced from the second predetermined value to the first predetermined value until it reaches an appropriate level corresponding to an acceptable power level and / or distance and / or spot size of the reflection signal. An advantage of embodiments of the present invention is that the power consumption is optimized.
[0025] The system preferably has at least two light sources. The output optical power of the first light source is the first predetermined value, and the output optical power of the second light source is the second predetermined value. The at least two light sources operate at different times.
[0026] An advantage of an embodiment of the present invention is that one light source is adapted to irradiate an object closer to the optical sensor with a light beam, and the other light source is adapted to irradiate an object farther from the optical sensor with a light beam. An advantage of an embodiment of the present invention is that different light sources are adapted to irradiate objects at different distance ranges from the optical sensor or objects having different reflectivities with light beams.
[0027] The optical sensor preferably has a plurality of pixel sensors, and each pixel sensor has a photodetector. The photodetector is preferably a single photon detector, preferably a single photon avalanche detector. The control unit is preferably adapted to change the bias of each of the photodetectors.
[0028] An advantage of an embodiment of the present invention is that the sensitivity of each photodetector to active light and noise can be adjusted, and a balance between the two can be obtained.
[0029] The scanning means preferably scans the light beam from the light source on the scene based on a beam steering function having a beam angular velocity, and the output optical power of the light source changes based on the angular velocity. When the angular velocity is less than a threshold angular velocity, the output optical power is preferably at most equal to the first predetermined value.
[0030] An advantage of an embodiment of the present invention is that significant power reduction can be obtained while minimizing the reduction of the irradiation field.
[0031] The duty ratio of the light source is at most 80%, preferably at most 60%, more preferably at most 40%, and most preferably at most 20%. An advantage of an embodiment of the present invention is that the power consumption is reduced.
[0032] In a second aspect, the present invention relates to an optical sensing method. The optical sensing method includes: - irradiating a scene with a light beam from a light source; - scanning the light beam along a trajectory over the scene; - receiving a reflected light signal from the scene by a light receiver; - sampling the reflected light signal. It has. The optical sensing method further includes: - changing the output optical power of the light source between at least a first predetermined value and a second predetermined value higher than the first predetermined value.
[0033] A preferred embodiment of the second aspect of the present invention has one or a preferred combination of two or more of the following features. - The reflected light signal is sampled at a predetermined sampling frequency, and the step of changing the output optical power between the first predetermined value and the second predetermined value is performed at a speed of at most the sampling frequency. - The optical sensing method includes estimating the power level of the reflected light signal and adjusting the output optical power of the light source based on the power level, and / or estimating the distance between the light receiver and the scene and adjusting the output optical power of the light source based on the distance, and / or estimating the spot size of the reflected light signal and adjusting the output optical power of the light source based on the spot size. - The optical sensing method includes scanning the light beam over the scene based on a beam steering function having an angular velocity. The output optical power of the light source is changed based on the angular velocity. - When the angular velocity is less than a threshold angular velocity, the output optical power is adapted to be equal to at most the first predetermined value.
[0034] The above and other features, configurations, and advantages of the present invention will become apparent from the following detailed description in conjunction with the accompanying drawings that exemplarily illustrate the principles of the present invention. This description is given for illustrative purposes only and does not limit the scope of the present invention.
Brief Description of the Drawings
[0035] This disclosure is further illustrated by the following description and the accompanying drawings.
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Embodiments for Carrying Out the Invention
[0036] The present invention relates to an optical sensing system for performing efficient optical sensing.
[0037] The present invention will be described with reference to specific drawings regarding specific embodiments, but the present invention is not limited thereto and is limited only by the claims. The described drawings are schematic and non-limiting. In the drawings, the sizes of some elements may be exaggerated for illustrative purposes and may not be drawn to scale. Dimensions and relative dimensions do not correspond to actual reductions for the implementation of the present invention.
[0038] The terms first, second, etc. in this specification and the claims are used to distinguish similar elements and are not necessarily used to describe an order in time, space, rank, or any other way. When used in this way, the terms are interchangeable in appropriate circumstances, and it should be understood that the embodiments of the invention described herein can operate in an order other than that described or illustrated herein.
[0039] Furthermore, terms such as top, under, etc. in this specification and the claims are used for purposes of explanation and are not necessarily for describing relative positions. When used in this way, the terms are interchangeable in appropriate circumstances, and it should be understood that the embodiments of the invention described herein can operate in an orientation other than that described or illustrated herein.
[0040] Numerous specific details are set forth in this specification. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure an understanding of this specification.
[0041] Throughout this specification, the mention of "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, although they could be. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments, as will be apparent to those skilled in the art from this disclosure.
[0042] Similarly, in the description of the exemplary embodiments of the present invention, it should be understood that various features of the present invention may be grouped together in one embodiment, figure, or description thereof for the purpose of streamlining the disclosure and facilitating understanding of one or more various aspects of the invention. However, this method of disclosure should not be construed as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims show, aspects of the invention lie in less than all the features of the single embodiment previously disclosed. Thus, the claims following the detailed description are hereby expressly incorporated herein, and each claim stands on its own as an individual embodiment of the present invention.
[0043] Furthermore, some embodiments described herein include some features included in other embodiments while excluding other features, but combinations of features of different embodiments are meant to be within the scope of the present invention and, as will be understood by those skilled in the art, form different embodiments. For example, in the following claims, any combination of the claimed embodiments can be used.
[0044] Unless otherwise defined, all terms used in disclosing the present invention, including technical and scientific terms, have the meanings commonly understood by one of ordinary skill in the art to which this invention belongs. As a further guide, definitions of terms are included to better understand the teachings of the present invention.
[0045] As used herein, the following terms have the following meanings:
[0046] As used herein, "A," "an," and "the" refer to both singular and plural unless the context clearly dictates otherwise. By way of example, "a contaminant" refers to one or more contaminants.
[0047] The recitation of numerical ranges by endpoints includes not only the recited endpoints but also all numbers and fractions subsumed within that range.
[0048] In a first aspect, the present invention relates to an optical sensing system, preferably for efficient optical sensing. The system has at least one optical sensor. The system further has an optical system capable of generating an image of a scene on the optical sensor.
[0049] The system further has at least one light source. For example, the light source is adapted to a wavelength detectable by the optical sensor. For example, it is between 100 nanometers and 10 micrometers, preferably between 100 nanometers and 1 micrometer. For example, the optical sensor is a photodetector or a matrix of photodetectors capable of detecting photons incident on each detector within a wavelength detection window in the range from 100 nanometers to 10 micrometers, preferably in the range from 100 nanometers to 1 micrometer.
[0050] The system further has scanning means adapted to scan the light beam from the light source, preferably at least partially, along a trajectory over the scene. The scanning is preferably continuous such that objects within the scene are continuously scanned and identified. For example, the light source generates a light beam that produces a light spot on the object, and the beam is continuously scanned over the scene along the trajectory. For example, at certain intervals of time, the beam will have scanned all or substantially all of the scene. The scanning may be, for example, a Lissajous pattern or a raster scan. The scanning means may be, for example, a MEMS scanner.
[0051] The system further includes a control unit. For example, the control unit is connected to the light source and preferably also connected to the scanner. The system is characterized in that the control unit is adapted to vary the output optical power of the light source between at least a first predetermined value and a second predetermined value higher than the first predetermined value. For example, the output optical power is varied continuously. For example, the output optical power is set to the first predetermined value for a predetermined period, and then the output optical power is set to the second predetermined value for a predetermined period. The first predetermined value corresponds to, for example, an object closer to the sensor, and the second predetermined value corresponds to an object farther from the sensor. The output optical power can also be varied, for example, between two or more predetermined values according to the scene, the objects in the scene, and their proximity to the system. In other words, the control unit is adapted to alternately and continuously vary the optical output power of the light source.
[0052] Objects at different distances from the system have different light reflections, for example, due to the distance from the system or due to different reflectivities of each object. Therefore, it is necessary to adjust the output optical power of the light source so that the reflected signal detected by the optical sensor is, for example, within the range of the power limit to which the optical sensor is adapted. For example, to prevent the optical sensor from being over-stimulated or under-stimulated. This is advantageous for obtaining a power-efficient system because the output optical power is adjusted based on, for example, the proximity and / or reflectivity of the object. This is also advantageous because, for example, by adjusting the light source to different output optical power levels according to the proximity and / or reflectivity, objects at different proximities and reflectivities can be identified using only one light source. Also, high-speed sensing is possible because information about different objects can be obtained in one rapid and partial scan. Also, a high dynamic range can be achieved because different adjacent objects can be identified almost simultaneously in one scan.
[0053] Further, as will be described later, the output optical power may be adjusted based on factors other than the proximity and / or reflectivity. Thereby, the spatial consistency of the detected optical signal can also be improved.
[0054] Artifacts in optical and / or image systems such as scattering, glare, flare, ghost, and speckle generally cause unwanted secondary (tertiary, etc.) signals. The stronger the reflected optical signal from the scene, the stronger the unwanted secondary signal. The reflected optical signal may reach a level that is too high such that the unwanted secondary signal impairs sufficient imaging of the desired optical signal, meaning that the spatial integrity of the optical signal deteriorates. By providing measurement scenarios with lower, different, or adapted optical powers, good spatial consistency can be guaranteed in at least one scenario.
[0055] Alternatively, instead of performing alternately, the control unit may start from the initial output optical power and then adjust its value based on, for example, the distance of the object, or the albedo of the object, or the spot size of the reflected signal. Thereafter, for example, periodically, the value is updated after a predetermined time has elapsed. For example, as will be described later, the output optical power changes from the second predetermined value to the first predetermined value.
[0056] Preferably, the optical sensor has a sampling frequency, and the output optical power of the light source changes or is modulated between the first predetermined value and the second predetermined value at a rate of at most the sampling frequency. Preferably, the rate of change or modulation is such that different parts of the scene are scanned by the light beam from the light source having an output optical power of either the first predetermined value or the second predetermined value. For example, one part of the scene is scanned by the light beam from the light source having an output optical power of the first predetermined value, and another part of the scene is scanned by the light beam from the light source having an output optical power of the second predetermined value. For example, the modulation rate may be less than twice the sampling rate, preferably at most five times, more preferably at most ten times. Alternatively, the modulation rate may be such that the output optical power of the light source changes between the first predetermined value and the second predetermined value each time the scanning means scans at least 1% of the scene, for example at least 5% of the scene.
[0057] The change or modulation is advantageous as it allows obtaining information about different objects in the scene while maintaining good resolution. For example, the modulation maintains good resolution of the objects in the scene and is fast enough to identify the proximity and / or reflectivity of the objects in the scene based on, for example, the reflected signals detected by the sensor.
[0058] The output optical power may depend on the proximity and / or reflectivity of the object. However, the scanning of the light beam may be started while the light source is randomly modulated between the first predetermined value and the second predetermined value. Then, based on this scanning, it is determined whether a specific region in the scene needs to be scanned by the light beam from the light source having an output optical power of the first predetermined value or the second predetermined value. For example, it may be based on the reflected signal (e.g., the power of the reflected signal) detected by the sensor. This is advantageous in reducing the power required for scanning the scene.
[0059] Preferably, the sampling rate of the optical sensor is at least 1 MHz, preferably at least 10 MHz, more preferably at least 100 MHz. This is suitable because in actual life, objects do not move very fast compared to such a sampling rate of the detector. For example, the optical sensor has a time resolution of at least 1 microsecond, preferably at least 100 nanoseconds, more preferably at least 40 nanoseconds. This is advantageous, for example, when scanning the scene before knowing which part of the scene is composed of which object, what reflectance it has, and / or how close it is to the optical sensor.
[0060] Preferably, the system has a processing unit. For example, the processing unit is connected to the optical sensor.
[0061] The processing unit can preferably estimate the power level of a reflected signal that is reflected by at least one object in the scene and received by the optical sensor. And the processing unit can adjust the control unit to change the output optical power of the light source based on the power level of the reflected signal.
[0062] The processing unit can preferably estimate the distance between the optical sensor and a point of the at least one object in the scene along the trajectory. And the processing unit can adjust the control unit to change the output optical power of the light source based on the distance.
[0063] The processing unit can preferably estimate the spot size of the reflected signal. And the processing unit can adjust the control unit to change the output optical power of the light source based on the spot size.
[0064] The processing unit is advantageous for optimizing the power consumption of the system in a simple way so that the light source emits light with the required output optical power.
[0065] Preferably, the distance can be estimated by triangulating a point of the at least one object in the scene detected by the optical sensor with data of the emitted light of the at least one light source. This is similar to triangulating the outputs of two optical sensors, because the data of the emitted light of the light source is known, i.e., because it is known which part of the scene is illuminated by the light at a certain time.
[0066] Preferably, the processing unit can estimate a ratio between the output optical power emitted by the light source and the optical power received by the sensor, for example, to estimate the distance and / or the reflectivity of the object. For example, if the ratio is too high, this means that the object is too close and / or reflects too much. Alternatively, if the ratio is too low, it means that the object is too far away or not reflecting. Preferably, the ratio is kept between a lower limit value and an upper limit value. For example, if the ratio is too high, the output optical power of the light source is reduced so that the ratio stays between the lower limit value and the upper limit value.
[0067] Preferably, the processing unit can classify the regions in the scene into at least two regions. For example, a first region including an object farther from the optical sensor and / or an object having a low reflectivity, and a second region including an object closer to the optical sensor and / or an object having a high reflectivity can be mentioned. Thereby, for example, the reflected signal becomes suitable for being received by the optical sensor. For example, it is possible to avoid artifacts such as glare, lens flare, and scattering due to the reflected signal being too strong, or not being detected due to being too weak. Further, the system can track the movement of an object (for example, within the same distance range) in any region, for example, so as to adapt the light source to irradiate the object with output optical power suitable for the object during and after the movement of the object. Also, the system can track the movement of an object close to or far from the optical sensor and adapt the output optical power of the light source accordingly. For example, when an object close to the optical sensor moves away from the optical sensor by a distance equal to or greater than a threshold value, for example, or when the object moves so that the reflected signal becomes lower than that adapted to be received by the optical sensor, the output optical power of the light source is increased, for example, increased from the first predetermined value to the second predetermined value. For example, there is a control loop or feedback loop that can adjust the output optical power based on different scenarios.
[0068] Preferably, once an object is identified, for example, if it is an object of interest, the system is adapted to assign a higher scanning density to the object relative to the background. For example, it is more important to track the movement and its distance of the object in the scene compared to the background, so that the object is tracked. For example, if the background is a wall, its distance generally remains the same compared to a moving object in the scene.
[0069] Preferably, when the system is used for object tracking, it may be desirable that only the object of interest is illuminated and the background is not illuminated. This is advantageous in further reducing power consumption.
[0070] Preferably, the output optical power is modulated until the signal is properly sensed by the optical sensor. For example, when the object is far away, the output optical power is increased to such an extent that the received signal is properly sensed by the optical sensor.
[0071] Preferably, the system further comprises at least one memory element. The element can store the position of the object in the scene at different times. For example, the light beam can irradiate the object in the scene with an appropriate output optical power, for example, based on a previous scanning cycle. This is also useful in enabling the system to store the position of the object in the scene and irradiate them with a light beam having an appropriate output optical power accordingly.
[0072] Preferably, the output optical power is defined to be proportional to the square of the distance of the object from the sensor. Therefore, the farther the object is from the sensor, the greater the output optical power of the light source should be, so as to maintain the power level of the reflected signal received by the sensor within the range adapted to be received by the sensor. Conversely, the closer the object is to the sensor and / or the light source, the lower the output optical power of the light source should be, so as to keep the intensity of the optical signal perceived or measured by the image sensor within a preferred range.
[0073] Preferably, the spot size is less than or equal to the threshold spot size. The spot size may refer to either the size of the light spot formed by the light beam irradiated onto the object in the scene and / or the size of the light spot formed by the reflected light of the object and detected by the optical sensor. In the case of a high-intensity signal, the measured spot size may increase due to effects such as glare, light scattering, blooming of the sensor pixel array, and optical and / or electrical crosstalk in the sensor pixel array. Thus, the measurement of the spot size can quantify the spatial integrity and can be used to determine whether it is desirable to change the output optical power for this spot position. The threshold spot size may refer to the maximum allowable spot size, for example, the spot size to which the sensor is adapted to operate. For example, when the optical sensor has a plurality of pixel sensors (for example, each pixel sensor has a photodetector), the spot size is preferably less than 3 pixel sensors, more preferably less than 4 pixel sensors, and even more preferably less than 5 pixel sensors. For example, the spot size can provide an indication of the distance of the object from the optical sensor. This is because for some irradiation types such as a parallel beam with an optical aperture, a large spot size means that the object is close to the optical sensor, and a small spot size means that the object is far from the optical sensor. Alternatively, the spot size may refer to the spot size resulting from the irradiation of light onto the object. For example, when the object is not smooth or flat, the light may be reflected multiple times on the object before finally reaching the optical sensor due to the irradiation of light onto the object. This may increase the spot size on the object. As another example, the light may be absorbed by the object, in which case the spot size may be different from the prediction. The threshold spot size determines whether the output optical power should be increased or decreased. For example, when the spot is larger than the threshold spot size, the output optical power decreases.
[0074] Preferably, the power level received by the optical sensor is within a window adapted for the sensor to operate. For example, it is between an upper power value and a lower power value, or corresponds to, for example, a predetermined upper photon count and a lower photon count per sample period. For example, 5 to 500 expected photons are incident per sample period and per pixel area.
[0075] Preferably, the present invention is implemented based on an estimation of at least one of the above-described elements, namely, distance (obtained using triangulation, for example), power level of the reflected signal, spot size, and reflectance. Therefore, as long as the main object is achieved, one or more of these elements can be estimated. That is, in the present invention, an appropriate output optical power of the light source is estimated in order to achieve an appropriate power level of the reflected signal adapted for the sensor to operate.
[0076] Preferably, the output optical power is changed from the second predetermined value to the first predetermined value. For example, this is based on the power level of the reflected signal and / or the distance and / or the spot size. For example, the initial output optical power of the light source is the second predetermined value. However, after obtaining information regarding the power level of the reflected signal and / or the distance and / or the spot size, the output optical power remains equal to the second predetermined value, for example, in a region of a scene where the object is farther away from the optical sensor, or is reduced to the first predetermined value, for example, in a region of a scene where the object is closer to the optical sensor, and the power level of the reflected signal is always maintained within a range adapted for the sensor to operate. This is continuously performed, for example, so that when an object that first received light at the first predetermined value moves away from the sensor, the output optical power is readjusted to the second predetermined value. This is advantageous for optimizing power consumption.
[0077] Preferably, the system comprises at least one optical sensor, and the distance is estimated by the displacement on the sensor of the optical signal corresponding to the point of the at least one object in the scene detected by the optical sensor. The displacement refers to the predicted position based on prior knowledge about the light source, and / or the displacement refers to the displacement of the optical signal corresponding to the point of the at least one object in the scene detected by at least one other optical sensor. This is advantageous in that it is easy to obtain the distance between each object and the sensor and then adjust the output optical power of the light source based on the distance.
[0078] Scanning the light beam from the light source is advantageous in enabling triangulation. For example, a system is used that has a light source that irradiates a light beam onto a scene (e.g., an environment) and two of the optical sensors arranged, for example, in different orientations relative to each other. The two optical sensors have a shared field of view of the scene. Thereby, it is possible to convert the x-y-time data of the two optical sensors into x-y-z-time data by triangulation. For example, the light source may be adapted to irradiate the light beam onto the scene in the irradiation trace. The light source has means adapted to scan (preferably continuously) the light beam over the scene. The optical sensor monitors the light spot generated by the light beam and outputs the position of a point of at least one object (e.g., a point on the surface of the object) in the scene along the trace in a plurality of instances. The x-y-time data of the two optical sensors can be converted into x-y-z-time data using triangulation. The light source can function, for example, as a reference point and synchronize the position of the point of the object of the first optical sensor with the point of the second optical sensor, and a depth or z-dimension can be created. The light source can irradiate and scan the light beam over the imaged scene in a Lissajous pattern or a pattern, or a raster scan, etc. This irradiation trajectory is advantageous in enabling efficient and fast image detection since after several irradiation cycles, a significant portion of the image has already been irradiated. Other irradiation patterns are also conceivable.
[0079] Preferably, the system has two light sources. For example, the output optical power of the first light source is the first predetermined value, the output optical power of the second light source is the second predetermined value, and the first and second light sources operate at different times, that is, they do not operate simultaneously. For example, the first light source operates at T = 10 - 20 nanoseconds, 30 - 40 nanoseconds, 50 - 60 nanoseconds, and the second light source operates at T = 20 - 30 nanoseconds, 40 - 50 nanoseconds, 60 - 70 nanoseconds... etc. For example, one light source is adapted to irradiate an object farther from the sensor with a light beam. For example, one light source has an output optical power equal to the second predetermined value. On the other hand, the other light source is adapted to irradiate an object closer to the sensor with a light beam. For example, the other light source has an output optical power equal to the first predetermined value. Distance is not the only criterion, and the reflectivity of the object also determines whether the object is irradiated with light having an output optical power of the first predetermined value or light having an output optical power of the second predetermined value. For example, an object that reflects light excessively such that the reflected signal received by the optical sensor becomes too strong is irradiated with the light beam of the light source having an output optical power of the first predetermined value.
[0080] Preferably, the optical sensor has a plurality of pixel sensors, and each pixel sensor has a photodetector. Preferably, the photodetector is a single - photon detector, preferably a single - photon avalanche detector. Alternatively, the photodetector is an avalanche photodetector.
[0081] Preferably, each photodetector is adapted to generate, for example, a stream of pulses where each pulse is the result of the detection of an incident photon. On average, the time interval between pulses is related to the intensity of the detected optical signal. The higher the intensity within a predetermined time window, the shorter the average time between pulses. Of course, as is well known to those skilled in the art, the actual time between pulses follows a Poisson distribution.
[0082] Preferably, each detector may be arranged in a reverse bias configuration. The detector can detect a single photon incident thereon. The detector may be adapted to output a logic signal, such as an electrical detection signal, upon detection of a photon. For example, the detection signal may be represented by a signal including logic "1", such as detection present, while the absence of a detection signal may be represented by a signal including logic "0", such as detection absent. Alternatively, the detection signal may be represented by, or result from, a pulse signal, such as a transition from, for example, logic "0" to logic "1" and then a return transition from logic "1" to logic "0". Also, the absence of detection may be represented by, or result from, the absence of such a pulse signal.
[0083] Preferably, the optical sensor has 100 or more pixel sensors, preferably 1,000 or more pixel sensors, more preferably 10,000 or more pixel sensors, still more preferably 100,000 or more pixel sensors, and most preferably 1,000,000 or more pixel sensors. For example, the optical sensor may be arranged in a matrix, and the optical sensor may have 1,000 rows of pixel sensors and 1,000 columns of pixel sensors.
[0084] Preferably, the control unit is adapted to change the bias of each of the photodetectors all together, in groups, or individually. For example, the bias voltage of the photodetector can change the sensitivity of the photodetector. By changing the bias, the sensitivity and noise of the detector can be controlled by switching the detector from a region with high quantum efficiency to a region with low quantum efficiency. For example, by operating in a region with low quantum efficiency, noise can be reduced, but at the same time the sensitivity to active light decreases. On the other hand, by operating in a region with high quantum efficiency, the sensitivity to active light is improved, but the noise also increases. Therefore, a balance between the two (sensitivity and noise) is desired.
[0085] Preferably, the scanning means scans the light beam from the light source on the scene based on a beam steering function having a beam angular velocity. The function is preferably a sine wave. For example, the deflection angle of the light beam is modulated based on the beam steering function. The output optical power of the light source changes based on the beam angular velocity. For example, the beam angular velocity has a maximum value, and the light source irradiates the light beam on the scene at an angular velocity of 1% or more, preferably 2% or more, more preferably 5% or more, still more preferably 10% or more, and most preferably 20% or more of the maximum value. In other words, the light source is off or irradiates the scene with a minimum output optical power for a low angular velocity, for example, less than a threshold angular velocity. In other words, this means that the end portion of the scene, for example, the portion corresponding to the highest deflection angle of the beam steering function, or, for example, a very end region of the scene, is not irradiated by the light beam or is irradiated minimally. Preferably, when the beam angular velocity is less than the threshold angular velocity, the output optical power is at most equal to the first predetermined value, and more preferably, the output optical power is at most equal to the minimum value or equal to zero when the beam angular velocity is less than the threshold angular velocity.
[0086] It should be noted that even in the region where the scene is irradiated with the minimum output optical power or zero output optical power, the scanner still moves along the same trajectory. The irradiation field (i.e., the region where the scene is irradiated) slightly decreases, but when the angular velocity of beam steering is not uniform, the power significantly decreases. For example, in the case of sine wave beam steering, when the irradiation field decreases by 10%, the power decreases by 50%. As shown in FIG. 6 below, a 10% decrease in the irradiation field is well within the acceptable range.
[0087] Preferably, the system has image representation means, such as a screen-like or other image representation device, to reproduce the position of points of the object within the scene.
[0088] Preferably, the optical system is used for 3D vision applications. For example, the system is used to visualize an object in three dimensions. Alternatively, the sensor can enable the scene to be analyzed, for example, by extracting features of an object within the scene, without necessarily generating an image of the scene.
[0089] Preferably, the system further comprises a plurality of optical sensors and / or a plurality of light sources. This is advantageous when creating 3D vision. For example, each optical sensor can be oriented differently such that the 3D perception of the scene being imaged is captured, for example, by triangulating the outputs of two such optical sensors.
[0090] Preferably, the duty ratio of the light source is at most 80%, preferably at most 60%, more preferably at most 40%, and most preferably at most 20%. For example, the control unit controls the duty ratio of the light source. Thereby, the power consumption of the system is reduced. The duty ratio can be changed dynamically, for example, it can be 100% at one point in time and 40% at another point in time. This can be based on, for example, whether the scene the user is looking at is changing and how fast the change is. For example, when the user is looking at the same scene, for example, looking without changing the head orientation, the duty ratio decreases.
[0091] In a second aspect, the present invention relates to an optical sensing method. The method includes the step of irradiating a scene with a light beam from a light source. The method further includes the step of scanning the light beam along a trajectory over the scene using, for example, a scanner, such as a MEMS scanner. The method further includes the step of receiving a reflected light signal from the scene by, for example, a light receiver that receives the reflected light signal from an object within the scene. For example, the light receiver is an optical sensor having, for example, a plurality of pixel sensors, and each pixel sensor has a light detector, preferably a single photon detector. For example, irradiate the detector of the optical sensor with a light beam having a wavelength detectable by the detector.
[0092] The method further comprises the step of sampling the reflected signal. For example, sampling is performed at a predetermined sampling frequency. The method is characterized in that it further comprises the step of changing the output optical power of the light source between at least a first predetermined value and a second predetermined value higher than the first predetermined value. For example, it is changed by a control unit that controls the output optical power of the light source.
[0093] Preferably, the reflected signal is sampled at a predetermined sampling frequency, and the step of changing the output optical power between the first predetermined value and the second predetermined value is performed at a rate of at most the sampling frequency. For example, the change or modulation rate of the output optical power may be at most less than twice the sampling frequency, preferably at most less than five times, preferably at most less than ten times or twenty times. The changing step may also be performed each time the scanning means scans at least 1% of the scene, for example at least 5% of the scene.
[0094] Preferably, the method comprises the steps of estimating the power level of the reflected optical signal and adjusting the output optical power of the light source based on the power level.
[0095] Preferably, the method comprises the steps of estimating the distance between the light receiver and the scene and adjusting the output optical power of the light source based on the distance.
[0096] Preferably, the method comprises the steps of estimating the spot size of the reflected optical signal and adjusting the output optical power of the light source based on the spot size.
[0097] Preferably, the method includes triangulating a point of the object in the scene detected by the light receiver with a point of the object in the scene detected by a second light receiver. Alternatively, the method includes triangulating a point of the object in the scene detected by the light receiver with data of a light beam emitted by the light source.
[0098] Preferably, the method includes classifying a region in the scene into at least two regions, preferably at least three regions. The step can be performed, for example, based on the proximity and / or reflectivity of an object in the scene to the light receiver. For example, there are a region irradiated with the light beam from the light source having the first predetermined output light power and a region irradiated with the light beam from the light source having the second predetermined output light power.
[0099] Preferably, the method includes scanning the light beam over the scene based on a beam steering function having a beam angular velocity. The output light power of the light source is varied based on the angular velocity. For example, the method may include irradiating a light beam from the light source onto the scene at an angular velocity exceeding 1% of the maximum value, preferably exceeding 2% of the maximum value, more preferably exceeding 5% of the maximum value, still more preferably exceeding 10% of the maximum value, and most preferably exceeding 20% of the maximum value. For example, the method may include irradiating the beam of the light source on the scene at an angular velocity equal to or higher than the threshold angular velocity with the light source having the second predetermined output light power, and irradiating the light beam of the light source on the scene at an angular velocity lower than the threshold angular velocity with the light source having the first predetermined output light power or zero output light power. Preferably, the output light power is adapted to be equal to at most the first predetermined value when the angular velocity is smaller than the threshold angular velocity.
[0100] The features of the second aspect (method) are as described in the first aspect (system).
[0101] In a third aspect, the present invention relates to using the system according to the first aspect and / or the method according to the second aspect for optical sensing, preferably for efficient optical sensing.
[0102] Further features and advantages of embodiments of the present invention will be described with reference to the figures. It should be noted that the present invention is not limited to the specific embodiments shown in these figures or described in the examples, but is only limited by the claims.
[0103] FIG. 1 shows an optical sensing system (1) having an optical sensor (2) and an optical system (3) capable of generating an image of a scene (4) on the optical sensor (2). The system (1) further includes a light source (5) that irradiates a light beam (33) that generates a light spot (7) on the scene (4). However, the present invention is not limited to generating a dot-shaped light spot (7), and any other suitable irradiation pattern can be used. The system (1) further includes scanning means (9) adapted to scan the light beam (33) over the scene (4). For example, the scanning means (9) may be a reflector or a MEMS mirror that can scan the light beam (33) over different parts of the scene (4), for example. The light beam (33) is scanned along an irradiation trajectory (8), for example, in a Lissajous pattern.
[0104] The system (1) further has a control unit (12) connected to the light source (5) and the scanning means (9). The control unit (12) is adapted to continuously vary the output optical power of the light source (5), for example, by changing the input to the light source (5). For example, the output optical power of the light source (5) is varied between a first predetermined value (11), for example, a low output optical power level represented by a thin line, and a second predetermined value (10), for example, a high output optical power level represented by a thick line, and this occurs repeatedly. For example, the output optical power changes at a rate of up to the sampling rate of the optical sensor (2), for example, a rate of 100 MHz. A high modulation rate is particularly advantageous when scanning different objects in the scene (4) in combination with Lissajous scanning, and can scan, for example, almost simultaneously, both when the object is far from and close to the optical sensor (2). However, it also functions at a change or modulation rate, for example, less than 1 / 10 times or 1 / 20 times the sampling rate. This means that the sensor can sample the return optical signal related to the first predetermined value (11) of the light source (5) alternately with at least one sample related to the second predetermined value (10) during at least one sampling period.
[0105] FIG. 2 shows the system (1) as in FIG. 1, but the output optical power of the light source (5) changes at a slower rate than in FIG. 1. For example, 10 times or 100 times slower. Alternatively, for example, the output optical power of the light source (5) changes each time the scanning means (9) scans a predetermined portion of the scene (4), for example, at least 1%, or 2%, or 5% of the scene (4). For example, the control unit (12) repeatedly changes the output optical power between a first predetermined value (11) for a predetermined portion or part of the scene (4) and a second predetermined value (10) for a predetermined portion or part of the scene (4). This takes more time than the implementation example shown in FIG. 1, but better resolution can be obtained for the objects in the scene (4).
[0106] Figure 3 shows a system (1) further including a processing unit (not shown) connected to, for example, an optical sensor (2). The processing unit can estimate the power level of a reflected light signal reflected from an object and received by the optical sensor (2), and / or can estimate the distance between the sensor (2) and at least one point of an object in the scene (4) along the trajectory (8), and / or can estimate the spot size of the signal. For example, points of an object at a distance closer to the optical sensor (2), for example, a distance closer than a predetermined distance, can be defined as a first set of points (13), and points of an object at a distance farther from the optical sensor (2), for example, a distance farther than the predetermined distance, can be defined as a second set of points (14). For example, the processing unit can classify the region of the scene (4) into a region having an object at a distance closer to the optical sensor (2), for example, a distance closer than the predetermined distance, such as a first region (27), and a region having an object at a distance farther from the optical sensor (2), for example, a distance farther than the predetermined distance, such as a second region (28). For example, if an object is at a distance farther than the predetermined distance from the optical sensor (2), the object belongs to the second region (28). For example, the predetermined distance is 1.5 meters as shown in Figure 3. However, the factor determining which object belongs to which region is not only the distance as described in the explanation. For example, a highly reflective object farther than the predetermined distance may belong to the first region (27), and similarly, a weakly reflective object closer than the predetermined distance may belong to the second region (28). This means that the predetermined distance is not necessarily 1.5 meters.
[0107] After classifying scene (4) into the first and second regions (27, 28), the processing unit controls the control unit (12) to change the output optical power of the light source (5). For example, for an object more than 1.5 meters away from the optical sensor (2), the output optical power of the light source (5) needs to be increased, such as to a second predetermined value (10), and for an object closer than 1.5 meters from the optical sensor (2), the output optical power of the light source (5) needs to be decreased, such as to a first predetermined value (11). This is because the farther the object is, the weaker the reflection signal from the object becomes.
[0108] In another implementation example, the scene is not classified, and the output optical power of the light source (5) is continuously adapted based on the evaluation of the previous sample. In fact, when the sample frequency is much higher than the scanning speed of the irradiator, the control unit has enough time to adapt the output optical power of the light source (5) "on the fly". For example, if the previous sample window detects no light spot or no reflection signal, the control unit can increase the output optical power, and similarly, if the sensor detects an incident signal that is too high, the control unit can decrease the output optical power.
[0109] The distance between the optical sensor (2) and an object in the scene (4) can be estimated based on the output optical power of the light source (5) and the light detected by the optical sensor (2), or for example based on the ratio of both. For example, when the output optical power is high, such as 0.2 W, an object located more than 1.5 meters away from the optical sensor (2) is accurately detected by the optical sensor (2), but an object located less than 1.5 meters away from the optical sensor (2) is not accurately detected. This is because, due to the short distance of the object, many photons are reflected by the object and received by the optical sensor (2). When the optical sensor (2) receives more photons than, for example, those adapted by the pixel sensors of the optical sensor (2), the detection becomes inaccurate due to, for example, the glare effect (6). On the other hand, when the output optical power is low, such as 0.01 W, an object located more than 1.5 meters away from the optical sensor (2) is not detected because the number of photons reflected by the object and received by the optical sensor (2) is small, but an object located less than 1.5 meters away from the optical sensor (2) is accurately detected. This is shown in FIG. 4 as will be described below. A second optical sensor may be present, and in this case, as described in the above explanation, the distance can be determined by triangulating the data of the two optical sensors.
[0110] Objects within the entire area are continuously monitored, for example, for the distance from the optical sensor (2). For example, when an object in the first area (27) moves further away from the optical sensor (2), for example, more than the 1.5 meters, the control unit (12) adjusts the light source (5) to irradiate a light beam (33) with a higher output optical power, for example, the output optical power of the light source (5) being a second predetermined value (10). The same applies when an object away from the optical sensor (2) (for example, 1.5 meters or more) approaches the optical sensor (2).
[0111] Figure 4 shows a simplified field of view of the optical sensor (2). For example, the optical sensor (2) has a plurality of pixel sensors. For example, the plurality of fields of view (21) correspond to a plurality of pixel sensors (for example, each pixel sensor has a photodetector). Figure 4 shows four different scenarios. In Figure 4(a), the output optical power of the light source (5) is high, for example 0.2W. In this case, the object is present very close to the plurality of pixel sensors, for example less than 1.5 meters from the pixel sensors. As a result, many photons are reflected by the object and received by the pixel sensors, and for example, more photons are received than those adapted for the pixel sensors to receive light, and for example, the shown glare effect (6) may occur. The glare effect (6) makes it difficult to distinguish the detections of adjacent different pixel sensors. On the other hand, for an object farther away from the pixel sensors, for example an object more than 1.5 meters away, as shown in Figure 4(b), due to the long distance, the number of photons reflected and received is reduced, so the detection becomes more accurate and the glare effect no longer exists. In this case, the number of photons corresponds to that adapted for the pixel sensors to receive light. In the third scenario of Figure 4(c), the output optical power of the light source (5) is low, for example 0.01W, and is suitable for closer objects, for example objects closer than 1.5 meters from the plurality of pixel sensors. However, for farther objects, as shown in Figure 4(d), the photons received by the plurality of pixel sensors are few or not received at all, so this is inappropriate.
[0112] FIG. 5 is a diagram showing, as a function of the distance from the pixel sensor, an example of the predicted average number of photons received by a pixel sensor having a photodetector per sample period of the pixel sensor in the case where the optical sensor (2) has a plurality of pixel sensors. In (a) and (c), the output optical powers of the light source (5) are 0.2 W and 0.01 W, respectively. The pixel sensor is adapted to operate in a region having a maximum desired value (17) and a minimum desired value (16) of the number of photons. The number of photons when the target is a Lambert reflector with a reflectivity of 100% is shown in (18) as a function of the distance from the pixel sensor. Similarly, the number of photons when the target is a Lambert reflector with a reflectivity of 10% is shown in (19). As shown in (a), the two curves (18, 19) are within the range of the maximum value (17) and the minimum value (16) for the object in the second region (28). This indicates that a high output optical power, for example, 0.2 W is required to detect the object in the second region (28). In contrast, (c) shows that a low output optical power, for example, 0.01 W is required to detect the object in the first region (27). In (a) and (c) of FIG. 5, the photodetector is biased to have a high quantum efficiency.
[0113] On the other hand, FIGS. 5(b) and (d) are similar diagrams, but the photodetector is biased to have a low quantum efficiency. In contrast to the implementation examples of FIGS. 5(a, c), this implementation example is advantageous for reducing noise. However, the drawback is that the sensitivity to active light decreases. The output optical powers of the light source (5) in FIGS. 5(b) and (d) are 1 W and 0.05 W, respectively, as an example.
[0114] As described above, the distance between the object and the optical sensor (2) is either within the first region (28), for example, 1.2 meters or more, or within the second region (27), for example, 0.75 meters or less. However, as shown in FIG. 5, the object may be in the third region (29), for example, between 0.75 meters and 1.2 meters. For example, for an object between 0.75 meters and 1.2 meters from the pixel sensor, the number of photons will not be within the range of the maximum value (17) and the minimum value (16). In this case, different output optical powers of the light source (5) are required. Therefore, the control unit (12) can also be adapted to vary the output optical power of the light source (5) between a first predetermined value (11), a second predetermined value (10) higher than the first predetermined value (11), and a third predetermined value higher than the first predetermined value (11) and lower than the second predetermined value (10).
[0115] FIG. 6 shows the field of view of the optical sensor (2). The scanning means (9) scans the light beam (33) of the light source (5) on the scene (4). The deflection angle of the means (9) is modulated, for example, in a Lissajous pattern, based on a beam steering function. The beam angular velocity of this function is reduced when the deflection angle reaches an extreme value, for example, at the edge of the scene (4). Therefore, the scene (4) can be classified into a field of view region where the angular velocity of the function is the lowest (22), for example, below a predetermined angular velocity, and a field of view region where the angular velocity of the function is the highest (23), for example, above a predetermined angular velocity, as shown in FIG. 6(b). As shown in FIG. 6(b), by turning off the light source (5) during the period when the angular velocity is the smallest, it is possible to reduce the power consumption while not significantly affecting the field of view. For example, as shown in FIGS. 6(b, c), by reducing the field of view of each axis by 10%, the power consumption has already been reduced by 50%. This is a particularly advantageous effect. FIG. 6(a) shows the field of view in a standard case, that is, when the switch of the light source (5) is not turned off.
[0116] FIG. 7 shows an example of the beam steering function. In this case, when scanning the optical beam (33) of the light source (5), it is a sine wave function (25) that modulates the deflection angle of the scanning means (9). The output optical power changes based on the angular velocity of the function (25). The function (25) has two parts with respect to its angular velocity. The two parts are a part (24) where the angular velocity is the lowest and a part (26) where the angular velocity is the highest. By operating the light source (5) only in the region (26) where the angular velocity is the highest, for example, in a region exceeding a threshold angular velocity, the field of view decreases slightly by, for example, 10%, and the power consumption decreases significantly by, for example, 50%.
[0117] FIG. 8 shows a plurality of fields of view (21) corresponding to a plurality of pixel sensors, and detections with different spot sizes are shown, where a single spot size (30) covers one pixel sensor. For example, in (a), the spot size is one pixel sensor, in (b), the spot size is four pixel sensors, and in (c), the spot size is nine pixel sensors. The processing unit can adjust the control unit (12) to change the output optical power of the light source (5) based on the spot size. For example, when the spot size is 9 as in (c), this indicates that the object is very close to the pixel sensor, so the output optical power of the light source (5) should be decreased. Therefore, the control unit (12) of the light source (5) is adjusted to decrease the output optical power. A predetermined threshold spot size may be selected, for example, to determine whether to adjust the control unit (12) to determine whether the detection belongs to an object that is very close to or very far from the optical sensor (2).
[0118] FIG. 9 shows an implementation example of an optical sensing system (1) that changes the output optical power of the light source (5) stepwise when scanned within the scene (4). This is useful, for example, in an initial stage for determining whether there are objects farther or closer to the sensing system (1) anywhere within the scene (4). This can be repeated at predetermined time intervals, for example, to update the data of the objects within the scene (4). Examples include when a closer object moves farther away or vice versa. Based on the result, for example, based on the distance of the object from the scene, for example, based on the spot size of the reflected signal from the object, or, for example, from the ratio of the emission power of the light source (5) to the received power of the sensor (2), the output optical power can be adjusted as appropriate. This is also shown in FIG. 10 described later. Both a positive step as shown in (a) and a negative step as shown in (b) can be successively applied to the same position in the scene (4). For example, to know which of the two is more suitable for irradiating a certain part of the scene (4). The variation of the output optical power can be performed in a digital discontinuous step method (32) or in an analog continuous function method (31).
[0119] Similar to FIG. 9, FIG. 10 shows the light spot (7) of the light beam (33) scanned stepwise on the scene (4). The different line widths correspond to different output light powers of the light source (5). FIGS. 10(a) and (b) are the same, but the output light powers are reversed when scanning the same part of the scene (4). As explained in FIG. 9, this is useful for determining which of the two irradiations is more suitable for a certain part of the scene (4). Once this is determined, the appropriate output light power is irradiated onto each part of the scene (4). For example, FIG. 10(c) shows two different output light power levels suitable for irradiating different parts of the scene (4). For example, the first region is irradiated with a lower output light power, and the second region is irradiated with a higher output light power. Finally, FIG. 10(d) shows that the duty ratio can also be changed. For example, when the user is looking at a scene that is not changing or changing slowly.
[0120] Other arrangements for achieving the object of the method and apparatus embodying the present invention will be apparent to those skilled in the art. Next, the details of specific embodiments of the present invention will be described. However, as detailed as the above description may be in the text, it will be apparent that the present invention can be applied in many ways. It should be noted that the use of specific terms when describing specific characteristics or aspects of the present invention is not to be construed as meaning that the terms in this specification are redefined to be limited to the specific characteristics or aspects of the present invention to which this term is associated.
Description of Reference Numerals
[0121] 1 Optical sensing system 2 Optical sensor 3 Optical system 4 Scene 5 Light source 6 Glare effect 7 Light spot 8 Locus 9 Scanning means 10 Second predetermined value 11 First predetermined value 12 Control unit 13 First set of points 14 Second set of points 16 Minimum value of photon number 17 Maximum value of photon number 18 Photon number for 100% output optical power 19 Photon number for 10% output optical power 21 Field of view of pixel sensor 22 Field of view region corresponding to minimum angular velocity 23 Field of view region corresponding to maximum angular velocity 24 Part of modulation function with lowest angular velocity 25 Modulation function 26 Part of modulation function with highest angular velocity 27 First region 28 Second region 29 Third region 30 Single spot size 31 Digital discontinuous staircase function 32 Analog continuous staircase function 33 Optical beam
Claims
1. An optical sensing system (1) for optical sensing, At least one optical sensor (2), An optical system (3) capable of generating an image of the scene (4) on the optical sensor (2), At least one light source (5), A scanning means (9) adapted to scan the light beam (33) from the light source (5) along the trajectory (8) on the scene (4), Control unit (12) and It has, The control unit (12) is configured to vary the output light power of the light source (5) between at least a first predetermined value (11) and a second predetermined value (10) that is higher than the first predetermined value (11). The control unit (12) is configured to alternately and continuously change the output light power of the light source (5), Optical sensing system (1).
2. In the optical sensing system (1) according to claim 1, The optical sensor (2) has a sampling frequency, and the output light power of the light source (5) varies between the first and second predetermined values (11, 10) at a rate equal to the sampling frequency. Optical sensing system (1).
3. In the optical sensing system (1) according to claim 1 or claim 2, The optical sensing system (1) includes a processing unit which can estimate the power level of a reflected signal that has been reflected by at least one object in the scene (4) and received by the optical sensor (2), and the processing unit which can adjust the control unit (12) to change the output light power of the light source (5) based on the power level of the reflected signal. Optical sensing system (1).
4. In the optical sensing system (1) according to claim 1 or claim 2, The optical sensing system (1) has a processing unit which can estimate the distance between the optical sensor (2) and a point of at least one object in the scene (4) along the trajectory (8), and the processing unit which can adjust the control unit (12) to change the output light power of the light source (5) based on the distance. Optical sensing system (1).
5. In the optical sensing system (1) according to claim 1 or claim 2, The optical sensing system (1) has a processing unit which can estimate the spot size of the reflected signal and can adjust the control unit (12) to change the output light power of the light source (5) based on the spot size. Optical sensing system (1).
6. In the optical sensing system (1) according to claim 4, The optical sensing system (1) has at least two optical sensors (2), and the distance is estimated by triangulation of a point of at least one object in the scene (4) detected by the first optical sensor with a point of at least one object in the scene (4) detected by the second optical sensor, or with data of the synchrotron radiation from at least one light source (5). Optical sensing system (1).
7. In the optical sensing system (1) according to claim 3, The processing unit can classify the region within the scene into at least two regions, each of which corresponds to an output optical power between the first predetermined value (11) and the second predetermined value (10). Optical sensing system (1).
8. In the optical sensing system (1) according to claim 1, The output optical power is varied from the second predetermined value (10) to the first predetermined value (11). Optical sensing system (1).
9. In the optical sensing system (1) according to claim 1, The optical sensing system (1) has at least two light sources (5), the output light power of the first light source is a first predetermined value (11), the output light power of the second light source is a second predetermined value (10), and the at least two light sources operate at different times. Optical sensing system (1).
10. In the optical sensing system (1) according to claim 1, The optical sensor (2) has a plurality of pixel sensors, and each pixel sensor has a photodetector. The control unit (12) is adapted to change the bias of each of the photodetectors. Optical sensing system (1).
11. In the optical sensing system (1) according to claim 1, The scanning means (9) scans the light beam (33) of the light source (5) on the scene (4) based on a beam steering function having a beam angular velocity, and the output light power of the light source (5) changes based on the beam angular velocity. Optical sensing system (1).
12. In the optical sensing system (1) according to claim 11, When the beam angular velocity is less than the threshold angular velocity, the output optical power is adapted to be at most equal to the first predetermined value (11). Optical sensing system (1).
13. In the optical sensing system (1) according to claim 1 or claim 12, The duty cycle of the light source (5) is a maximum of 80%, preferably a maximum of 60%, more preferably a maximum of 40%, and most preferably a maximum of 20%, and the duty cycle is dynamically changed. Optical sensing system (1).
14. An optical sensing method, The steps include illuminating the scene (4) with the light beam (33) of the light source (5), The steps include scanning the light beam (33) along the trajectory (8) on the scene (4), The steps include receiving the reflected light signal from the aforementioned scene (4) with a photodetector, The steps include sampling the reflected light signal, The steps include: changing the output light power of the light source (5) between at least a first predetermined value (11) and a second predetermined value (10) that is higher than the first predetermined value (11); It has, The changes in the step of changing the output light power of the light source (5) are characterized by being performed alternately and continuously. Optical sensing method.
15. In the optical sensing method according to claim 14, The reflected light signal is sampled at a predetermined sampling frequency, and the step of varying the output light power between the first and second predetermined values (11, 10) is performed at a rate of at most the sampling frequency. Optical sensing method.
16. In the optical sensing method according to claim 14 or claim 15, A step of estimating the power level of the reflected light signal and adjusting the output light power of the light source (5) based on the power level, and / or, A step of estimating the distance between the light receiver and at least one object, and adjusting the output light power of the light source (5) based on the distance, and / or A step of estimating the spot size of the reflected light signal and adjusting the output light power of the light source (5) based on the spot size, Having, Optical sensing method.