WO2016042511A2

WO2016042511A2 - Emitter angle control for laser projector

Info

Publication number: WO2016042511A2
Application number: PCT/IB2015/057157
Authority: WO
Inventors: Eldad STERN
Original assignee: Mantisvision Ltd.
Priority date: 2014-09-18
Filing date: 2015-09-17
Publication date: 2016-03-24
Also published as: WO2016042511A3

Abstract

A projector includes an emitter array comprising a plurality of individual emitters and a mask for providing a structured light pattern. A distance between the emitter array and the mask is such that, at a given emitter temperature and given a certain emitter drive current, the light from the emitter array meets a uniformity criterion.

Description

Emitter Angle Control for Laser Projector

Background

[0001] VCSEL (V ertical-Cavity Surface-Emitting Laser) have been recently become an important component in a wide spectrum of applications. The performance of such components, similarly to other semiconductor devices, is affected by various factors related to the environment and electrical loads that operate it,

[0002] Lasers are commonly used as light projectors in various applications and purposes, and designed to produce beams of light that are projected onto optical components, such as lenses.

Summary

[0003] A projector includes an emitter array comprising a plurality of individual emitters and a mask for providing a structured light pattern. A distance between the emitter array and the mask is such mat, at a given emitter temperature and given a certain emitter drive current, the light from the emitter array meets a uniformity criterion.

[0004] In a further embodiment, a projector includes an array of light sources spaced apart on a substrate. A temperature sensor is positioned to sense temperature about the light sources. A current sensor is coupled to sense current provided to the light sources. A controller is coupled to receive information from the temperature sensor and the current sensor, and coupled to the light sources to control an emission profile of the light sources as a function of the received information.

[0005] A further projector includes an array of vertical cavity surface emitting lasers spaced apart on a substrate, a temperature sensor positioned to sense temperature about the lasers, a current sensor coupled to sense current provided to the lasers, and a controller coupled to receive information from the temperature sensor and the current sensor, and coupled to the lasers to control an emission beam angle of the lasers as a function of the received information. [0006] A method includes receiving a sensed temperature of an emitter array, receiving a parameter representative of current provided to the emitter array, and calculating a current to provide to the emitter array as a function of the received sensed temperature and parameter representative of current to control beam

divergence of light emitted from the emitter array.

[0007] A further method includes receiving a sensed temperature of a laser array, receiving a parameter representative of current provided to the laser array, and calculating a current to provide to the laser array as a function of the received sensed temperature and parameter representative of current to control beam divergence of light emitted from the laser array.

Brief Description of the Drawings

[0008] FIG. 1 is a block diagram illustrating beam divergence with respect to temperature change according to an example embodiment.

[0009] FIG. 2 is a block diagram illustrating beam divergence with respect to current change according to an example embodiment.

[0010] FIG. 3 is a block perspective view of an array of vertical cavity surface emitting lasers (VCSEL) showing beam divergence and spacing according to an example embodiment.

[0011] FIG. 4 is a block side view of the VCSEL array of FIG. 3 including a mask according to an example embodiment.

[0012] FIG 5 is a block diagram illustrating a projector having controlled beam divergence with respect to temperature and current according to an example embodiment.

[0013] FIG. 6 is a block diagram illustrating electronic circuitry for forming a controller according to an example embodiment.

[0014] FIG. 7 is a top view of a quadrant of an emitter array showing an order associated with each emitter in the quadrant according to an example embodiment.

[0015] FIG. 8 is graph illustrating power versus emitter array to mask distances for a beam divergence angle of 15 degrees according to an example embodiment. [0016] FIG. 9 is graph illustrating power versus emitter array to mask distances for a beam divergence angle of 11 degrees according to an example embodiment.

Detailed Description

[0017] In the following description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural, logical and electrical changes may be made without departing from the scope of the present invention. The following description of example embodiments is, therefore, not to be taken in a limited sense, and the scope of the present invention is defined by the appended claims.

[0018] The functions or algorithms described herein may be implemented in software or a combination of software and human implemented procedures in one embodiment. The software may consist of computer executable instructions stored on computer readable media or computer readable storage device such as one or more memory or other type of hardware based storage devices, either local or networked. Further, such functions correspond to modules, which are software, hardware, firmware or any combination thereof. Multiple functions may be performed in one or more modules as desired, and the embodiments described are merely examples. The software may be executed on a digital signal processor, ASIC, microprocessor, or other type of processor operating on a computer system, such as a personal computer, server or other computer system.

[0019] VCSEL (V ertical-Cavity Surface-Emitting Laser) have been recently become an important component in a wide spectrum of applications. The performance of such components, similarly to other semiconductor devices, is heavily affected by various factors related to the environment and electrical loads that operate it.

[0020] Lasers are commonly used as light projectors in various applications and purposes. In combination with a mask, lasers can produce patterned beams of light that are projected onto optical components, such as lenses. In many cases, the divergence angle of the beam can affect, for example, the amount of light available to project through the mask. Changes in the current and temperature may vary the divergence angle of the laser beam. In a similar manner the output far field intensity profile of the lasers can affect the amount of light that is available to project through the mask, and the far field intensity profile of the lasers can also be sensitive to changes in drive current and/or temperature. For simplification of the description, unless it is explicitly stated otherwise, or when it is apparent from the description, the terms "beam divergence angle" and "far field intensity profile" are interchangeable, and the factors which effect the beam divergence profile should be considered to have a similar effect over the far field intensity profile, and the results of such effects should be regarded as being indicative of the effects that such factors would have over the far field intensity profile. It would be appreciated that some tuning may be required in order to accurately reflect the effects of the various factors on the far field intensity profile, and such tuning can be factored into the equations that are used to manage one or more of: the current that is supplied to the emitters array, the temperature of the emitters array and the distance between the emitters array and the mask.

[0021] As for the beam emission from the top of the VCSEL surface, its output profile may vary under changes of both temperature and current. In one embodiment, an output beam profile is controlled in accordance with knowledge of the needed system's performance under different conditions of temperature and current. The angle of divergence may be actively controlled according to the temperature and current to ensure optimal projection through a mask.

[0022] To maintain the system stability and provide best performance, several parameters of the system are to be taken into consideration, namely mask resolution, emitters' x-y spacing on the VCSEL array, the uniformity of light needed for the projector and the distance of the mask from the VCSEL. In addition, examinations of the VCSEL beam-profile show measured divergence angles with respect to various temperature and current values. Based on these measurements, divergence increases with increasing current and decreases with increasing temperature, as shown in FIG. 1 at 100 and FIG. 2 at 200. [0023] In FIG.1, temperature dependentbeam divergence is illustrated for two temperatures. At 110, a beam divergence angle is shown for a temperature of 60°C, and at 115, a beam divergence angle is shown for a temperature of20°C. As previously indicated, the divergence at lower temperature is greaterthanthat at high temperature.

[0024] In FIG.2, a beam divergence for a current of4 Amps is illustrated at

210 and for a current of 12 Amps at 215. Again, the higherthe current, the greater the beam divergence. A resultant formula using linear approximation is as follows:

[0025] Where / and Tdenote the current (Amperes) and temperature

(Celsius), respectively. The parameters and constant ofFormula 1 are determined empirically by having a VCSEL array operate at different drive current and at different temperatures, and measuring the effects ofthe current andtemperature over the beam divergence angle. It would be appreciated that the testing can be performed for each batch ofVCSEL or once for a certain type ofVCSELs or emitter array. It would also be noted that the testing protocol can be influenced by a desired accuracy and reliability thereof. Accordingly, the paramaters and constant in Formula, are provided as an example for illustration purposes, and for different emitter arrays (including differenttypes ofemitter arrays, different batches ofa certaintype of emitter array, or different units ofa certain types ofemitter array) different parameters and constant can be determined and applied.

[0026] FIG.3 illustrates a perspective viewportion ofan array oflasers 310 to project light 315 from an array oflasers 310 through a mask. FIG 4 is a sideview of the array including a mask 410.

[0027] In one embodiment, the following parameters may be taken into consideration: d_x And_y- are the distances between the VCSELs in a multiple array.

An empirical formula for finding the angle ofdivergence, a range oftemperatures in which theVCSEL operates, a range ofdrive currentthat can be usedto drive the VCSEL and desired overlap ofthe beams on a mask ofthe VCSELs in a multiple array or a desired divergence angle ofthe emitters may be taken into account. It would be noted that the desired overlap measure and the desired divergence can be related and can even serve as alternatives to one another. It would be further appreciated that other measures can be devised which correspond to a desired overlap of the beams on a mask of the VCSELs in a multiple array and/or correspond to a desired divergence angle of the emitters, and such corresponding measures can be used in addition or as an alternative to the desired overlap or desired divergence angle measures.

[0028] Given the temperature and the ideal distance d_z between the VCSEL and the mask, one can control the current and/or the temperature using a temperature control module and/or a current control module, respectively.

[0029] For example, the temperature control module can include thermoelectric cooler (TEC), various types of heat sinks etc.

[0030] The current controller can include any kind of current source control, including for example, the laser driver disclosed in PCT Patent Application No. PCT/IL2014/050529, which is hereby incorporated by reference in its entirety. It would also be appreciated that controlling the current can involve tracking the power output of the emitters array or of the projector (where the emitters array serve as light source). The power measurements can be used in addition or as an alternative to current input measurements.

[0031] According to examples of the presently disclosed subject matter, by controlling the current mat is applied to the VCSEL and/or by controlling the VCSEL' s temperature a target angle of divergence can be reached. Further by way of example, the target angle of divergence can be a certain range of angles which are acceptable. In still further examples, the range is a certain optimal required target and an acceptable tolerance.

[0032] Controlling the current that triggers the device can also be done by setting the pulse width or alternatively by PWM (pulse width modulation) configuration. In one embodiment, d_z and the angle of convergence are controlled such that multiple beams overlap at the mask. Between 2 and four beams overlap in one embodiment to provide a desired uniformity of light at the mask. [0033] When changing the current of a laser, and thus altering the amount of light that the projector emits, the performance of the projector is also changed. Such changes may have an impact on the contrast of the projected beam. Hence, when using a device that absorbs the projected light and collects the energy (e.g., a sensor), such as a rolling shutter camera with a capacitor, the obtained image quality might not be as expected or can fall below a certain target quality threshold. According to examples of the presently disclosed subject matter, PWM with a constant current (or with small current variations) can be used to control the current that is applied to the VCSEL. It would be noted that by using PWM to control the current that is applied to the VCSEL image quality can be retained, at least compared to modifying the current of the laser, which would change the amount of light emitted by the projector.

According to example, controlling the PWM with a target current (e.g., constant) is carried out under the restriction that the frequency is high enough:

Where ^te denotes the exposure duration. In one example, a single pulse per period of time may be transformed into multiple pulses over the same period having the same amplitude having approximately the same amount of energy as the single pulse.

[0034] The 3D camera can be designed to collect energy via a capacitor, and thus the average energy collected by the camera in the PWM control implementation (with a certain target current) can be approximately the same as a single (continuous) pulse with lower energy. When using PWM, the resolution can be higher than an analog output.

[0035] Consider a system that works under varying heat conditions. As a result, the beam divergence angle could vary with temperature. In order to compensate for the deviation and maintain the desired angle, the system according to examples of the presently disclosed subject matter, can react to changes in temperature by automatically adapting the current to an extent which compensates, at least in part, for the effect of the temperature change. For example the extent of adjustment of the current can be determined based on Formula 1 presented above. As mentioned above, the parameters and constant in Formula 1 can be different for different emitter arrays. Further according to examples of the presently disclosed subject matter, the divergence angle control process can be configured and operable such that as the temperature rises, the beam angle goes down which leads to current increasing and vice versa.

[0036] FIG. 5 is a block diagram of a projector 500 for controlling beam divergence angles according to an example embodiment. The projector 500 includes an array of vertical cavity surface emitting lasers 510 spaced apart on a substrate 515. A temperature sensor 520 is positioned to sense temperature about the lasers 510. A current sensor 525 is coupled to sense current provided to the lasers via a driver 530, and a controller 535 is coupled to receive information from the temperature sensor and the current sensor, and coupled to the lasers to control an emission beam angle of the lasers as a function of the received information.

[0037] It would be noted that due to design choice or as a result of

implementation limitations, for example, the temperature sensor 520 may be positioned such that it is not capable of reading directly the temperature of the VCSEL array, and rather the temperature of the VCSEL can be estimated or deduced based on the temperature readings at the position where the temperature sensor 520 is located. The temperature sensor may be directly coupled to the VCSEL array, such as a substrate or packaging material, or may be located near the array to sense a temperature from which the temperature of the VCSEL can be deduced based on empirical testing, simulation, or calculation. Formula 1 can be adapted accordingly, for example, by adding some factor (which can be a constant, a function, etc.) to reflect the difference between the temperature at the location of the sensor and the VCSEL' s temperature or by using different parameters and/or constant in the formula. For example, the controller 535 can use a lookup table (e.g., generated based on empirical measurements) to determine the temperature of the VCSEL, based on the received temperature readings, and possibly based on further inputs and factors. In another example, the controller 535 can use a formula which receives as input the measured temperature, and possibly other parameters and factors, and computes the VCSEL' s temperature. [0038] Still further by way of example, the controller 535 can have various configurations and can be implemented for example as part of the VCSEL driver, as part of a 3D camera controller, etc.

[0039] In one embodiment, a mask 540 is positioned to receive light from the lasers at a distance such that light from the lasers overlaps at or prior to reaching the mask. Still further by way of example, the mask may be positioned, and the beam angle can be controlled to provide a certain level of uniformity across the mask plane. In yet further embodiments, in a projector, a relative distance between the mask and the VCSEL array can be determined such that for a given temperature and for a given current, the non-uniformity profile of the plurality of individual emitters (or the divergence angle of the plurality of individual emitters) is such that a uniformity criterion related to the light intensity distribution across the mask plane is met. In another example, the temperature or the current can change, such that for a given relative distance between the mask and the VCSEL array a different distribution (or uniformity profile) of light across the mask plane is achieved.

[0040] In an example, a non-uniformity profile of the plurality of individual emitters can be associated with the divergence angle of the beam emitted by the plurality of individual emitters. The non-uniformity profile can be expressed as a target divergence angle of each one of the individual emitters in the emitters array. The target divergence angle can represent an average, a median or any other statistical or other measure of the divergence angle across the multiple emitters. In another example the target divergence angle can provide a certain range of divergence within which all, a majority, etc. of the emitters in the array should operate.

[0041] In still a further example, the relative distance is a minimum distance where the non-uniformity profile of the plurality of individual emitters is such that a uniformity criterion related to the light intensity distribution across the mask plane is met. A minimal beam angle of the plurality of individual emitters can be associated with the minimum distance.

[0042] In still further examples, there can be provided a maximum distance for positioning the mask relative to the laser array. By way of example, the maximum distance can be associated with predetermined (e.g. minimum or average) power transfer of the laser array source through the mask. Further by way of example the maximum distance can be associated with predetermined light intensity criterion across the mask surface. By way of one specific example the predetermined criteria can be a minimum power transfer of 85%, and/or the criterion that the light intensity at the edge of the mask does not drop below 80% of its value at the center of the mask illumination area.

[0043] According to examples of the presently disclosed subject matter, the mask can be positioned within a certain range from the laser array, wherein the range can be determined according to the minimal distance, which is in turn determined according to the non-uniformity profile of the plurality of individual emitters and according to a uniformity criterion related to the light intensity distribution across the mask plane, and further according to the maximum distance. Still further by way of example, both the minimal distance and the maximum distance can be associated with a given temperature and a given current or with a set of temperature and current parameters which balance one another, and thus allowing the distribution of light across the mask plane to remain constant or to remain within an acceptable range. The maximum distance can be associated with a maximum beam divergence angle of the plurality of individual emitters.

[0044] In an example, the target level of uniformity across the mask plane can be expressed as a certain number of overlaps between adjacent lasers. Returning now to the description of FIG. 5, the mask may be positioned, and the beam angle can be controlled to provide beam overlap from two to four lasers at the mask, for example. One or more sets of optics 545 may be positioned to provide beam shaping and focusing and may be dispersed before and after mask 540 in various embodiments. The controller 535 may be operable to provide modulated pulses of current to the lasers via driver 530, optionally using an energy storage device 550 that is recharged by a power source 555 between pulses. The controller 535 may also be operable to modulate a pulse width of the modulated pulses of current while maintaining a constant current for each pulse. The controller may be further operable to modulate a current amplitude of each pulse while maintaining a constant pulse width. In one embodiment, the emission beam angle decreases with increasing temperature and increases with increasing current. The temperature sensor 520 may be located on a surface of the substrate opposite a surface supporting the lasers. In further embodiments, multiple temperature sensors may be utilized.

[0045] Table 1 below provides an example of the change in beam divergence angle of an emitter in a reference VCSEL array under various drive current and temperature conditions.

Table 1

[0046] Where in the i column various drive current values (in Watts) are listed, in t column various temperature values are listed (in degrees Celsius), in the Cont. column the constant for the VCSEL array is provided, and angle are the various beam divergence angles of emitters in the emitter array under the various current and temperature combinations. It would be noted that the various parameters and the constant are provided here by way of non-limiting example.

[0047] Table 2 below shows a set of example parameters for the reference

VCSEL array with which Table 1 is associated, when the beam divergence angle of the emitters is at 15 degrees. A beam divergence angle of 15 degrees is the broadest angle in Table 1 and this angle is reached when the drive current is at 8 Watts and the temperature of the VCSEL array is at 10 degrees Celsius. In particular Table 2 shows the light distribution across the mask plane for different emitter array to mask distance values when the beam divergence angle is at 15 degrees.

Table 2

[0048] The leftmost column in Table 2 is the emitters order column. FIG. 7 is a top view of a quadrant of the emitter array with which Table 2 and showing the order associated with each emitter in the quadrant, Each square in FIG. 7 represents an emitter, and the center emitter (the zero order square) is shown at the top-left corner of the quadrant. It should be noted that the layout of the emitter array shown in FIG. 7 and associated with Table 2, is just one example of a possible emitter array layout, and it would be noted that further examples of the presently disclosed subject matter are applicable to the emitter array layouts, such as hexagonal, circular and other layouts. It would be further noted that a table similar to Table 2 can be readily generated by those versed in the art to accommodate other designs and layouts of the emitters.

[0049] The column immediately left to the order column provides the distance difference in each of the X and Y axis relative to the previous order; next is the distance column which lists the linear distances between a center emitter and a furthest emitters of each order; the contribution column lists the number of emitter that are added by each order; angle is the beam divergence angle of each emitter. In Table 2 the angle is 15 degrees and it is the angle that is associated with a drive current of 8 Watts and emitter array temperature of 10 degrees Celsius, as mentioned above; dz denotes the relative distance in mm between the emitters in the emitter array to the mask plane. In Table 2, each row is associated with an incrementally increasing relative distance; the left most column shows the total power at each relative distance point. This parameter reflects the contribution of light from more and more emitters as the relative distance grows. As the relative distance grows, the light from the emitters diverges further and more and more beams from individual emitters overlap, and a result the light across the mask plane become increasingly more uniform. Thus, given a certain light uniformity criterion, the relative distance where the uniformity criterion is met can be determined. The process of determining the exact relative distance can be influenced by design preferences and can also involve empirical measurements, trail and error iterations, etc.

[0050] Reference is additionally made to FIG. 8, which provides a graphical illustration between relative distance and power, according to the respective values in Table 2.

[0051] Table 3 below shows a set of example parameters for the reference

VCSEL array with which Table 1 is associated, when the beam divergence angle of the emitters is at 11 degrees.

Table 3

[0052] Table 3 has the same structure as Table 2. However, the beam divergence angle in Table 3 is 11 degrees (as opposed to the 15 degrees angle in Table 2). A beam divergence angle of 11 degrees is the narrowest angle in Table 1 and this angle is reached when the drive current is at 3 Watts and the temperature of the VCSEL array is at 60 degrees Celsius. As can be seen, at this angle, in order to achieve the same power values as in Table 2 (e.g., when the drive current is at 8 Watts and the temperature is at 10), the VCSEL array needs to be positioned further away from the emitters. All the other parameters are the same as in Table 2.

[0053] Reference is additionally made to FIG. 9, which provides a graphical illustration between relative distance and power, according to the respective values in Table 3.

[0054] It would be appreciated, that according to examples of the presently disclosed subject matter, any suitable combination of: either one or both of the emitter array temperature and emitter array drive current can be controlled to a achieve a certain uniformity profile across the mask plane at a given relative distance between the emitter array and the mask plane. In other examples, the relative distance between the emitter array and the mask can be controlled to achieve a certain light uniformity across the mask plane, possibly in addition to controlling either one or both of the emitter array temperature and emitter array drive current. Still further by way of example either one or both of the emitter array temperature and emitter array drive current can be controlled, and in addition or as an alternative a target light uniformity across the mask plane can be controlled or adjusted so that, given a certain emitter array temperature, emitter array drive current and relative distance, a target light uniformity across the mask plane is achieved.

[0055] As mentioned above, by controlling the PWM further flexibility can be achieved with regard to the drive current and with regard to any of the above parameters which are effected or which in combination with the drive current have an effect over some other parameter. Thus for example, in case a certain current and temperature combination is required in order to achieve a certain light uniformity criterion at a given (say fixed) relative mask-array distance, and the output power of the projector needs to be increased (for example, as requested by an exposure control process running on the 3D camera), the PWM that is applied to the emitter array can be adjusted so as to keep the drive current at a certain level, and as a result maintain a fixed light uniformity profile across the mask plane, while enabling a higher output intensity. A similar process in the reverse direction can be used for decreasing the intensity. [0056] There is now provided a description of a possible testing protocol that can be used in order to find an optimal distance for positioning a mask relative to an emitter array. It would be appreciated that this process is taken under certain conditions and makes certain assumptions that can change according to the applicable implementation (different emitter types, layouts, batches and configurations, different operational parameters, such as drive current and emitter array temperature, and different uniformity profile criterion). Those versed in the art can apply the following protocol with variations to accommodate different implementations and desired target parameters.

[0057] By way of example, in the following empirical relative distance determination protocol, a raytrace program such as ZEMAX being sold by Zemax, LLC of Redmond, WA. It would be noted that physical measurements can be used instead of a simulation program. An array of emitters is setup as the source of the rays where the arrangement or layout of the emitters is identical to a VCSEL array which the empirical relative distance determination protocol is used to model. For example, the correct emitter diameter and spacing are chosen to accurately model the source. Further by way of example, the emitter layout can be hexagonal or Cartesian or any other shape that the VCSEL array manufacturer is capable of producing. For each emitter in the array a certain divergence angle is provided. In addition, or as an alternative for each emitter an output far field intensity profile is provided. By way of example, the output intensity profile describes the intensity of the rays exiting each emitter as a function of the divergence angle. Examples of intensity distributions are Gaussian, Super Gaussian, Donut shapes, etc.

[0058] As mentioned above, the divergence angle and/or the far field intensity profile can change with drive current or VCSEL array temperature. The protocol can assume certain drive current and temperature values, or it can be performed for a variety of different drive current and temperature values, and for various combinations of different drive current and temperature values.

[0059] The actual far field intensity distribution of each emitter can be provided as input into the simulation program. Now rays (e.g., many millions) are traced from all the emitters in the VCSEL array (can be 50 million rays). Detectors are placed (in the program) at different distances from the VCSEL array to determine the optimum distance for the required uniformity level and relative power transfer. If the detector is too close to the VCSEL array then the individual emitters will be evident in the detector rendering a very non-uniform source (like a series of delta functions). If the detector is too far away from the VCSEL array the rays from one emitter will have well overlapped with rays from neighboring detectors. In this instance the intensity distribution will be exactly the same as the far field intensity distribution from each individual emitter, i.e. Gaussian, Super Gaussian, Donut, etc. In this case it will be very difficult to establish an area of illumination (identical to the active area of the mask) with the pre-determined minimum uniformity criterion. At the optimum distance the area of illumination will satisfy the pre-determined minimum uniformity criterion. The pre-determined minimum uniformity criterion can be, for example, "less than X% fall off (say 10%) at the edge of the illumination area". Furthermore it is evident that some power will be lost outside the area of illumination. The optimum VCSEL array mask distance is intended to minimize mis power loss while maintaining the uniformity criterion

[0060] FIG.6 is a block schematic diagram of control circuitry 600 to implement a controller according to an example embodiment. Fewer elements than those shown may be used in some embodiments to provide the functionality capable of performing the methods described. One example computing device in the form of a computer 600, may include a processing unit 602, memory 603, removable storage 610, and non-removable storage 612. Memory 603 may include volatile memory 614 and non-volatile memory 608. Computer 600 may include - or have access to a computing environment that includes - a variety of computer-readable media, such as volatile memory 614 and non-volatile memory 608, removable storage 610 and nonremovable storage 612. Computer storage includes random access memory (RAM), read only memory (ROM), erasable programmable read-only memory (EPROM) & electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD ROM), Digital Versatile Disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium capable of storing computer-readable instructions. Computer 600 may include or have access to a computing environment that includes input 606, output 604, and a communication connection 616. The computer may operate in a networked environment using a communication connection to connect to one or more remote computers, such as database servers. The remote computer may include a personal computer (PC), server, router, network PC, a peer device or other common network node, or the like. The communication connection may include a Local Area Network (LAN), a Wide Area Network (WAN) or other networks.

[0061] Computer-readable instructions stored on a computer-readable medium are executable by the processing unit 602 of the computer 600. A hard drive, CD- ROM, and RAM are some examples of articles including a non-transitory computer- readable medium. For example, a computer program 618 capable of providing a generic technique to perform access control check for data access and/or for doing an operation on one of the servers in a component object model (COM) based system may be included on a CD-ROM and loaded from the CD-ROM to a hard drive. The computer-readable instructions allow computer 600 to provide generic access controls in a COM based computer network system having multiple users and servers.

[0062] Examples

[0063] 1. A projector comprising:

an emitter array comprising a plurality of individual emitters;

a mask for providing a structured light pattern;

wherein a distance between the emitter array and the mask is such that, at a given emitter temperature and given a certain emitter drive current, the light from the emitter array meets a uniformity criterion.

[0064] 2. The projector according to example 1 , further comprising

[0065] a temperature sensor positioned to sense temperature about the emitter array;

[0066] a current sensor coupled to sense current provided to the emitter array; and [0067] a controller coupled to receive information from the temperature sensor and the current sensor, and coupled to the emitter array to control an emission beam angle of the emitters as a function of the received information.

[0068] 3. The projector according to any of examples 1 -2, further comprising

a temperature sensor positioned to sense temperature about the emitter array; a current sensor coupled to sense current provided to the emitter array; and a controller coupled to receive information from the temperature sensor and the current sensor, and coupled to the emitter array to control a far field intensity profile of the emitters as a function of the received information.

[0069] 4. The projector according to any of examples 1 -3, wherein the uniformity criterion requires that an intensity at an edge of the mask does not drop below 80% of its value at a center of the mask.

[0070] 5. The projector according to any of examples 1 -4, wherein the uniformity criterion requires that at a non-edge area of the mask each point within an emission cone of each emitter is illuminated by light from at least one other emitter.

[0071] 6. The projector according to any of examples 1 -5, wherein the uniformity criterion requires that at a non-edge area of the mask, each point within an emission cone of each emitter is illuminated by light from at least two other emitters.

[0072] 7. The projector of example 2 wherein the controller is operable to modulate a pulse width of the modulated pulses of current while maintaining a constant current for each pulse.

[0073] 8. The projector of example 7 wherein the controller is operable to modulate a current amplitude of each pulse while maintaining a constant pulse width.

[0074] 9. The projector of any of examples 1 -8 wherein the temperature sensor is located on a surface of the substrate opposite a surface supporting the laser.

[0075] 10. A projector comprising:

an array of light sources spaced apart on a substrate;

a temperature sensor positioned to sense temperature about the light sources; a current sensor coupled to sense current provided to the light sources; and a controller coupled to receive information from the temperature sensor and the current sensor, and coupled to the light sources to control an emission profile of the light sources as a function of the received information.

[0076] 11. The proj ector of example 10 and further comprising a mask positioned to receive light from the light sources at a distance such that light from the lasers overlaps at or prior to reaching the mask.

[0077] 12. The projector of example 11 wherein the mask is positioned, and the emission profile is controlled to provide beam overlap from two to four light sources at the mask.

[0078] 13. The proj ector of any of examples 1-12 wherein the light sources comprise vertical cavity surface emitting lasers (VCSEL).

[0079] 14. The proj ector of any of examples 10-12 wherein the controller is operable to provide modulated pulses of current to the lasers.

[0080] 15. The projector of example 14 wherein the controller is operable to modulate a pulse width of the modulated pulses of current while maintaining a constant current for each pulse.

[0081] 16. The projector of example 14 wherein the controller is operable to modulate a current amplitude of each pulse while maintaining a constant pulse width.

[0082] 17. The proj ector of any of examples 1-16 wherein the emission profile is a beam divergence angle and the beam divergence angle decreases with increasing temperature and increases with increasing current.

[0083] 18. The projector of any of examples 1-17 wherein the emission profile is a far field intensity profile, and wherein the far field intensity profile changes when the temperature of the emitters array changes.

[0084] 19. A method comprising:

receiving a sensed temperature of an emitter array;

receiving a parameter representative of current provided to the emitter array; calculating a current to provide to the emitter array as a function of the received sensed temperature and parameter representative of current to control beam divergence of light emitted from the emitter array. [0085] 20. The method ofexample 19 wherein the emitters array comprises vertical cavity surface emitting lasers.

[0086] 21. The method ofany ofexamples 19-20 and further comprising directingthe light emitted from the emitter arrayto a mask having a pattern such that at leasttwo beams overlap atthe mask

[0087] 22. The method ofany ofexamples 19-21 whereinthe beam divergence Θ(Τ,Ι) is calculated in accordance with a linear approximation as follows:

where I and T denote the current (Amperes) and temperature (Celsius), respectively.

[0088] 23. The method ofany ofexamples 19-22 whereinthe current is pulse width modulated.

[0089] 24. A projector comprising:

a vertical cavity surface emitting laser;

a temperature sensor positioned to sense temperature about the laser;

a current sensor coupled to sense current provided to the laser; and

a controller coupled to receive information fromthe temperature sensor and the current sensor, and coupled to the laserto control an emission beam angle ofthe laser as a function ofthe received information.

[0090] 25. The projector ofexample 24 wherein the controller is operable to provide modulated pulses ofcurrent to the laser.

[0091] 26. The projector ofexample 25 wherein the controller is operable to modulate a pulse width ofthe modulated pulses ofcurrent while maintaining a constant current for each pulse.

[0092] 27. The projector ofany ofexamples 24-26 wherein the controller is operable to modulate a current amplitude ofeach pulse while maintaining a constant pulse width.

[0093] 28. The projector ofany ofexamples 24-27 wherein the emission beam angle decreases with increasing temperature and increases with increasing current. [0094] 29. The projector of any of examples 24-28 wherein the

temperature sensor is located on a surface of the substrate opposite a surface supporting the laser.

[0095] 30. The projector of any of examples 24-29 wherein the

temperature sensor measures a temperature from which the laser temperature is deducible.

[0096] 31. A proj ector comprising:

an array of light sources spaced apart on a substrate;

a temperature sensor positioned to sense temperature about the light sources; a current sensor coupled to sense current provided to the light sources; and a controller coupled to receive information from the temperature sensor and the current sensor, and coupled to the light sources to control an emission beam angle of the light sources as a function of the received information.

[0097] 32. The projector of example 31 and further comprising a mask positioned to receive light from the light sources at a distance such mat light from the lasers overlaps at or prior to reaching the mask.

[0098] 33. The projector of example 32 wherein the mask is positioned, and the beam angle is controlled to provide beam overlap from two to four light sources at the mask.

[0099] 34. The projector of example 33 wherein the light sources comprise vertical cavity surface emitting lasers.

[00100] 35. The projector of any of examples 31 -34 wherein the controller is operable to provide modulated pulses of current to the lasers.

[00101] 36. The projector of example 35 wherein the controller is operable to modulate a pulse width of the modulated pulses of current while maintaining a constant current for each pulse.

[00102] 37. The projector of any of examples 35-36 wherein the controller is operable to modulate a current amplitude of each pulse while maintaining a constant pulse width. [00103] 38. The projector of any of examples 31-37 wherein the emission beam angle decreases with increasing temperature and increases with increasing current.

[00104] 39. The projector of any of examples 31-38 wherein the

temperature sensor is located on a surface of the substrate opposite a surface supporting the lasers.

[00105] 40. A method comprising:

receiving a sensed temperature of a laser array;

receiving a parameter representative of current provided to the laser array; calculating a current to provide to the laser array as a function of the received sensed temperature and parameter representative of current to control beam

divergence of light emitted from the laser array.

[00106] 41. The method of example 40 wherein the laser array comprises vertical cavity surface emitting lasers.

[00107] 42. The method of any of examples 40-41 and further comprising directing the light emitted from the laser array to a mask having a pattern such that at least two beams overlap at the mask.

[00108] 43. The method of any of examples 40-42 wherein the beam divergence Θ(Τ,Ι) is calculated in accordance with a linear approximation as follows:

where / and T denote the current (Amperes) and temperature (Celsius), respectively.

[00109] 44. The method of any of examples 40-43 wherein the current is pulse width modulated.

[00110] Although a few embodiments have been described in detail above, other modifications are possible. For example, the logic flows depicted in the figures do not require the particular order shown, or sequential order, to achieve desirable results. Other steps may be provided, or steps may be eliminated, from the described flows, and other components may be added to, or removed from, the described systems. Other embodiments may be within the scope of the following claims.

Claims

1. A proj ector comprising:

an emitter array comprising a plurality of individual emitters;

a mask for providing a structured light pattern;

2. The projector according to claim 1, further comprising

a temperature sensor positioned to sense temperature about the emitter array; a current sensor coupled to sense current provided to the emitter array; and a controller coupled to receive information from the temperature sensor and the current sensor, and coupled to the emitter array to control an emission beam angle of the emitters as a function of the received information.

3. The projector according to claim 1, further comprising

4. The projector according to claim 1, wherein the uniformity criterion requires that an intensity at an edge of the mask does not drop below 80% of its value at a center of the mask.

5. The projector according to claim 1, wherein the uniformity criterion requires that at a non-edge area of the mask each point within an emission cone of each emitter is illuminated by light from at least one other emitter.

6. The projector according to claim 1, wherein the uniformity criterion requires that at a non-edge area of the mask, each point within an emission cone of each emitter is illuminated by light from at least two other emitters.

7. The projector of claim 2 wherein the controller is operable to modulate a pulse width of the modulated pulses of current while maintaining a constant current for each pulse.

8. The projector of claim 7 wherein the controller is operable to modulate a current amplitude of each pulse while maintaining a constant pulse width.

9. The projector of claim 1 wherein the temperature sensor is located on a surface of the substrate opposite a surface supporting the laser.

10. A proj ector comprising:

an array of light sources spaced apart on a substrate;

11. The projector of claim 10 and further comprising a mask positioned to receive light from the light sources at a distance such that light from the lasers overlaps at or prior to reaching the mask.

12. The projector of claim 11 wherein the mask is positioned, and the emission profile is controlled to provide beam overlap from two to four light sources at the mask.

13. The proj ector of claim 10 wherein the light sources comprise vertical cavity surface emitting lasers (VCSEL).

14. The projector of claim 10 wherein the controller is operable to provide modulated pulses of current to the lasers.

15. The projector of claim 14 wherein the controller is operable to modulate a pulse width of the modulated pulses of current while maintaining a constant current for each pulse.

16. The projector of claim 14 wherein the controller is operable to modulate a current amplitude of each pulse while maintaining a constant pulse width.

17. The projector of claim 10 wherein the emission profile is a beam divergence angle and the beam divergence angle decreases with increasing temperature and increases with increasing current.

18. The projector of claim 10 wherein the emission profile is a far field intensity profile, and wherein the far field intensity profile changes when the temperature of the emitters array changes.

19. A method comprising:

receiving a sensed temperature of an emitter array;

receiving a parameter representative of current provided to the emitter array; and

calculating a current to provide to the emitter array as a function of the received sensed temperature and parameter representative of current to control beam divergence of light emitted from the emitter array.

20. The method of claim 19 wherein the emitters array comprises vertical cavity surface emitting lasers.

21. The method of claim 19 and further comprising directing the light emitted from the emitter array to a mask having a pattern such that at least two beams overlap at the mask.

22. The method of claim 19 wherein the beam divergence is calculated in

accordance with a linear approximation as follows:

23. The method of claim 19 wherein the current is pulse width modulated.

24. A projector comprising:

a vertical cavity surface emitting laser;

a temperature sensor positioned to sense temperature about the laser;

a current sensor coupled to sense current provided to the laser; and a controller coupled to receive information from the temperature sensor and the current sensor, and coupled to the laser to control an emission beam angle of the laser as a function of the received information.

25. The projector of claim 24 wherein the controller is operable to provide modulated pulses of current to the laser.

26. The projector of claim 25 wherein the controller is operable to modulate a pulse width of the modulated pulses of current while maintaining a constant current for each pulse.

27. The projector of claim 24 wherein the controller is operable to modulate a current amplitude of each pulse while maintaining a constant pulse width.

28. The projector of claim 24 wherein the emission beam angle decreases with increasing temperature and increases with increasing current.

29. The projector of claim 24 wherein the temperature sensor is located on a surface of the substrate opposite a surface supporting the laser.

30. The projector of claim 24 wherein the temperature sensor measures a temperature from which the laser temperature is deducible.

31. A proj ector comprising:

an array of light sources spaced apart on a substrate;

32. The projector of claim 31 and further comprising a mask positioned to receive light from the light sources at a distance such that light from the lasers overlaps at or prior to reaching the mask.

33. The projector of claim 32 wherein the mask is positioned, and the beam angle is controlled to provide beam overlap from two to four light sources at the mask.

34. The projector of claim 33 wherein the light sources comprise vertical cavity surface emitting lasers.

35. The projector of claim 31 wherein the controller is operable to provide modulated pulses of current to the lasers.

36. The projector of claim 35 wherein the controller is operable to modulate a pulse width of the modulated pulses of current while maintaining a constant current for each pulse.

37. The projector of claim 35 wherein the controller is operable to modulate a current amplitude of each pulse while maintaining a constant pulse width.

38. The projector of claim 31 wherein the emission beam angle decreases with increasing temperature and increases with increasing current.

39. The projector of claim 31 wherein the temperature sensor is located on a surface of the substrate opposite a surface supporting the lasers.

40. A method comprising:

receiving a sensed temperature of a laser array;

receiving a parameter representative of current provided to the laser array; calculating a current to provide to the laser array as a function of the received sensed temperature and parameter representative of current to control beam divergence of light emitted from the laser array.

41. The method of claim 40 wherein the laser array comprises vertical cavity surface emitting lasers.

42. The method of claim 40 and further comprising directing the light emitted from the laser array to a mask having a pattern such that at least two beams overlap at the mask.

43. The method of claim 40 wherein the beam divergence is calculated in

accordance with a linear approximation as follows:

44. The method of claim 40 wherein the current is pulse width modulated.