Dynamic laser diode compensation

A laser drive circuit compensates for laser diode dynamics. A compensation value is determined from a sum of weighted basis functions. The basis functions may be a function of current desired optical powers and/or past desired optical powers. The weights may be updated periodically based at least in part on accumulated basis function outputs and measured optical powers.

FIELD

The present invention relates generally to compensation in optical systems, and more specifically to compensation for dynamic changes in laser diode operating characteristics.

BACKGROUND

Laser diodes emit light when current is passed through the diode. The optical power of the light varies as the drive current through the diode is varied.FIG. 1shows a prior art laser diode drive circuit that includes a laser diode110, a digital-to-analog converter (DAC) and driver circuit108, and an inverse laser model101. In operation, a value representing a desired optical light power is provided to the inverse laser model101. Inverse laser model101maps the desired optical power value to a different drive value to compensate for the nonlinear operating characteristic of diode110. The drive value is then provided to the DAC/driver circuit108, which then drives diode110with a drive current, resulting in emitted light112.

FIG. 2shows prior art curves used in the drive circuit ofFIG. 1. Curve220shows an idealized nonlinear diode operating characteristic. This typical diode curve is well known and shows that a negligible (or zero) amount of light is produced below a certain threshold current, and then above the threshold, the amount of light produced is a nonlinear function of drive current.

Curve230shows a desired linear relationship between desired optical power and output optical power that is actually produced by the diode. Curve210shows the inverse laser model that, when combined with the operating characteristic shown by curve220, will result in the desired linear relationship shown at230.

Using an inverse laser model as shown inFIGS. 1 and 2works well to linearize the relationship between desired optical power and output optical power when the laser diode operating characteristic is time-invariant. Unfortunately, laser diode characteristics are not always time-invariant. For example, the output optical power of the laser diode may vary with age, temperature changes, and other factors.

DESCRIPTION OF EMBODIMENTS

FIGS. 3A and 3Bshow how short laser light pulse durations can contribute to errors in optical energy in accordance with various embodiments of the present invention. The pulses inFIGS. 3A and 3Brepresent pulses of light emitted from a laser diode, such as laser diode110(FIG. 1). BothFIGS. 3A and 3Bshow ideal pulses310,320having identical optical energy E. Because the optical energy is the product of optical power and pulse duration, the desired optical power is given by:
P=E/T(1)

where P is the desired optical power, E is the optical energy of the pulse, and T is the pulse duration.

Ideal pulse310(FIG. 3A) has duration T0, and ideal pulse320(FIG. 3) has shorter duration T1. As shown inFIGS. 3A and 3B, the desired optical power324is a higher magnitude than desired optical power314because of the difference in pulse durations.

FIGS. 3A and 3Balso show actual pulses316,326with finite rise and fall times. The finite rise and fall times may be attributable to any cause, including for example, driver circuit nonlinearities, laser diode nonlinearities, and device physics. The finite rise and fall times can introduce errors in laser light pulse optical energies. For example, as shown inFIG. 3A, optical energy error312represents the difference in optical energies of ideal pulse310and actual pulse316. Similarly, as shown inFIG. 3B, optical energy error322represents the difference in optical energies of ideal pulse320and actual pulse326.

Error322is a larger percentage error than error312. This larger error is caused in part by the combination of short pulse durations and finite rise and fall times. Various embodiments of the present invention compensate for this error, as further described below.

FIG. 4shows rise time correction in accordance with various embodiments of the present invention.FIG. 4shows the same ideal pulse320that is shown inFIG. 3B. To compensate for the error described above, the desired optical power414has been increased to
P=E/T+C(2)

where C is a compensation value that is added to the desired optical power value. As shown inFIG. 4, the error is reduced in part because the optical power of the actual pulse416is greater than the optical power of the ideal pulse for a portion of the pulse duration. As described further below, various embodiments of the present invention determine appropriate values for C based on many criteria. For example, some embodiments determine values for C as a function of the desired optical power. Also for example, some embodiments determine values for C based on past desired optical powers.

FIG. 5shows the effects of short pulse durations as a function of desired optical power values in accordance with various embodiments of the present invention. Curve510represents normalized optical pulse energies for 100 ns (nanosecond) pulses as a function of desired optical power values, and curve520represents normalized optical pulse energies for 7 ns pulses as a function of desired optical power values. The desired optical power values are shown as ten bit digital numbers ranging in value from zero to 1023, but this is not a limitation of the present invention.

In some embodiments, an inverse laser model is generated from curve510. In these embodiments, the laser diode input current to output light power relationship can be linearized (seeFIG. 2) for 100 ns pulses, but significant errors are introduced for shorter pulses. As described further below, various embodiments of the present invention determine compensation values that are summed with the desired optical power values for shorter pulse durations to account for these errors.

The non-linear difference between curves510and520represents errors in optical energies as a function of desired optical power values. These nonlinear differences may be time varying nonlinear operating characteristic of the system that become more pronounced for short pulse durations. Three characteristic areas of the curves have been identified, and are labeled as “knee shift,” “slope change,” and “roll over.” The labels are for convenience only, and are not meant to be limiting in any way.

FIG. 6shows basis functions useful to compensate for time varying nonlinear operating characteristic shown inFIG. 5in accordance with various embodiments of the present invention. Each of the basis functions αix[n] shown inFIG. 6is used to determine a component of a compensation value, where that component compensates for a different labeled area of the curve. For example, compensation for the “roll over” portion of the curve can be generated using a basis function of the form:
eax+b(3)

and compensation for the “slope change” and “knee shift” portions of the curve can be generated using basis functions of the form:
1−eax+b(4)

where a and b are constants. In some embodiments, the constants a and b are determined from experimental data using well known curve fitting methods.

The basis functions shown inFIG. 6are examples only. Any function that can compensate for errors may be used. The exponential basis functions shown inFIG. 6are relatively straight forward to implement in hardware, which makes the exponential form a suitable choice.

Various embodiments of the present invention generate compensation values by summing weighted basis function outputs. For example, a compensated desired optical power may be determined by:

where y[n] is the compensated desired optical power, x[n] is desired optical power, αi(x[n]) are the basis functions, wiare weights applied to the basis functions, and N is the number of basis functions. An example embodiment that determines a compensated optical power value according to Eq. (5) is described below with reference toFIG. 7.

FIG. 7shows a laser drive circuit with dynamic laser diode compensation in accordance with various embodiments of the present invention. Laser drive circuit700includes memory circuits702and752, accumulators750and772, basis function circuits710, multipliers712, summers714and716, inverse laser model101, DAC/driver102, and laser diode110. Laser drive circuit700also includes photodiode730, integrator732, analog-to-digital converter (ADC)734, summer736, multiplier738, and memory circuit740.

In operation, a desired optical power value x[n] is received on node701. The desired optical power value corresponds to a desired optical pulse energy. For example, referring back toFIG. 3B, the desired optical power value on node701may be equal to desired optical power324. In some embodiments, the desired optical power value x[n] is a sequence of discrete values. For example, in some embodiments, x[n] is a sequence of light power values for successive pixels in an image.

Laser drive circuit700determines a compensation value on node715by summing weighted basis function outputs according to Eq. (5). Basis function circuits710determine output values that are a function of the desired optical power value on node701, multipliers712apply weights to the basis function outputs, and summer714sums the multiplier outputs to create the compensation value on node715. Summer716then sums the desired optical power value with the compensation value to create the compensated desired optical power value y[n] on node717. The compensated desired optical power value on node717is a drive value that compensates for finite pulse rise times, as well as other nonlinearities in the system. For example, the compensated desired optical power value on node717may be equal to compensated desired optical power414(FIG. 3).

Inverse laser model101maps the compensated desired optical power value on node717to a drive value, and DAC/driver circuit102converts the drive value to a drive current to drive laser diode110.

Weights that are applied to basis function outputs are received on node780. In some embodiments, the weights are updated periodically based on various criteria. For example, the weights may be updated periodically based on past weight values, past basis function outputs, past desired optical power values, and measured optical power values. As shown inFIG. 7, past basis function outputs are represented by accumulated basis function output values A on node770, past desired optical power values are represented by accumulated desired optical power values M on node772, and measured optical power values are represented by integrated measured optical power values {circumflex over (M)} on node774. Values may be accumulated and/or integrated for any period of time. For example, in some embodiments, values are accumulated and integrated for a fixed period of time (the “accumulation period”), and in other embodiments, values are accumulated and integrated for a variable period of time.

Accumulator772accumulates individual basis function outputs over the accumulation period, and stores the result in memory circuit702as a vector A with length N. Similarly, accumulator750accumulates desired optical power values over the accumulation period, and stores the result in memory circuit752as scalar M.

Pickoff mirror720and fold mirror722are positioned to reflect at least a portion of the emitted laser light112to photodiode730. Current provided by photodiode730represents a scaled version of the optical light power emitted by diode110. Integrator732integrates the photodiode current over the accumulation period, and provides the result to ADC734. In some embodiments, integrator732includes circuit components to integrate the current directly, and in other embodiments, integrator732includes a transimpedance amplifier to convert the current to a voltage, and the voltage is integrated.

Summer736subtracts a value that corresponds to background light, and multiplier738provides a scale factor for unit conversion. The result is stored in memory circuit740as {circumflex over (M)}.

The various circuits shown inFIG. 7may be implemented in any fashion. For example, memory circuits may include static random access memory semiconductor devices. Accumulators may include digital adder circuits that are resettable at the end of each accumulation period. Basis function circuits may include digital adders, multipliers, registers, state machines, and the like. Multipliers may include digital multipliers, and summers may include digital adders. The inverse laser model may be implemented as a look up table in a digital memory device, or may be a computational device that maps the compensated desired optical power value to a drive value using a mathematical function.

DAC/driver circuit102may include any type of digital to analog converter, and may include any type of driver circuit. For example, DAC/driver circuit102may include a DAC with a current output or a DAC with a voltage output followed by a voltage-to-current converter to convert the DAC output to the final drive current to drive the laser diode. The DAC may include any width digital word. For example, in some embodiments, the compensated desired optical power is a 10 bit digital word, however, this is not a limitation of the present invention.

FIG. 8shows a processing circuit in accordance with various embodiments of the present invention. As further described below, processing circuit800may implement algorithms that update weights to be applied to basis function outputs. Processing circuit800includes processor810and memory820. Memory820represents a non-transitory computer-readable medium that stores instructions. When instructions stored in memory820are executed, processor810determines new values for the weights wnon node780.

Processor810may be any type of processor capable of executing instructions and performing mathematical calculations. For example, processor810may be a microprocessor, a digital signal processor, or the like. Memory820may be any type of memory capable of non-transitory storage of processor instructions. For example, memory820may a volatile or nonvolatile semiconductor storage device such as static random access memory or FLASH memory. Memory820may also include magnetic or optical storage.

In some embodiments, system800includes graphics processor(s), field programmable gate array(s) (FPGA), and/or application specific integrated circuit(s) to perform some or all of the described functions.

In operation, processor receives past basis function outputs A on node770, past desired optical power values M on node772, and past measured optical power values {circumflex over (M)} on node774, and determines the new weights wnon node780. For example, some embodiments determine new weights using an equation of the form:
n+1=(1−α)0+αn+β(μw+(Cw−1+ATCnoise−1A)−1ATCnoise−1(M−{circumflex over (M)}−Aμw))  (6)

n+1are the new weights,

nare the existing weights,

μwis the average of past weights,

A are the accumulated basis function outputs,

M are the accumulated desired optical power values,

{circumflex over (M)} are the integrated measured optical power values,

Cwis the basis function covariance matrix,

Cnoiseis the measured noise covariance matrix,

0are the initial weights,

α is a restoring constant (default is 1), and

β is a learning constant (default is 1).

In some embodiments, Eq. (6) is solved using a recursive Bayesian approach such as Cholesky Decomposition and Tikhonov Regularization. The Bayesian approach allows the system of equation to be solved even with noisy or little meaningful information collected from the desired optical power values. This is done by measuring the range of real compensator corrections and forcing the solution to remain within these bounds in addition to building on the solutions from previous iterations.

FIGS. 9 and 10show optical energy variations as a function of previous diode drive values in accordance with various embodiments of the present invention.FIG. 9shows variations in optical pulse energy for 7 ns pulses as a function of previous diode drive values. The previous diode drive value x[n−1] is shown as a 10 bit digital code for convenience, however this is not a limitation of the present invention.FIG. 9shows that the maximum energy in a pulse of a given current drive value x[n] is when the previous drive value x[n−1] is near threshold (x[n−1]˜130). This suggests that the pulse energy has some relation to laser physics and not just driver rise-time as described above. It should be noted that the relationship is highly non-linear and is very difficult to compensate.

For convenience, three different areas ofFIG. 9have been identified for compensation: “rise loss,” “peaking,” and “fall gain.” These terms are being used as labels only and are not meant to limit the present invention in any way. In the “rise loss” region, previous drive values less than threshold tend to suppress the optical pulse energy of the current drive value. In the “peaking” region, previous drive values around threshold tend to increase the optical pulse energy of the current drive value, and in the “fall gain” region, high previous drive values tend to suppress the optical pulse energy of the current drive for small current drive values.

FIG. 10shows the same data asFIG. 9, with the independent variable being the current drive value and the plot being parameterized based on previous drive values of zero (minimum drive), 134 (threshold), and 1023 (maximum drive). If the previous code is a zero the pulse will have significantly less energy than a pulse with the previous code near threshold (threshold ˜130).

FIG. 11shows basis functions useful to compensate for the limitations shown inFIGS. 9 and 10in accordance with various embodiments of the present invention. Each of the basis functions βix[n−1] shown inFIG. 11is used to determine a component of a compensation value, where that component compensates for a different labeled area of the curve. For example, compensation for the “rise loss” and “peaking” portions of the curve can be generated using basis functions of the form:
eax+b(7)

and compensation for the “fall gain” portion of the curve can be generated using a basis function of the form:
1−eax+b(8)

where a and b are constants. In some embodiments, the constants a and b are determined from experimental data using well known curve fitting methods.

The basis functions shown inFIG. 11are examples only. Any function that can compensate for errors may be used. The exponential basis functions shown inFIG. 11are relatively straight forward to implement in hardware, which makes the exponential form a suitable choice.

Various embodiments of the present invention generate compensation values by summing weighted basis function outputs. For example, a compensated desired optical power may be determined by:

where y[n] is the compensated desired optical power, x[n] is desired optical power, x[n−1] is the previous desired optical output power, βi{x[n]} are the basis functions, wiare weights applied to the basis functions, and N is the number of basis functions. An example embodiment that determines a compensated optical power value according to Eq. (9) is described below with reference toFIG. 12.

FIG. 12shows a laser drive circuit with dynamic laser diode compensation in accordance with various embodiments of the present invention. Diode drive circuit1200is similar to diode drive circuit700(FIG. 7) with the exception of basis function circuits1210and delay stage1202. Delay stage1202receives the desired optical power value x[n], and delays it by one sample time to produce x[n−1], which is input to basis function circuits1210. Basis function circuits1210receive x[n−1] and determine basis function outputs according to the basis functions shown, and the compensation value on node715is the sum of the weighted basis function outputs.

The weights may be updated as described above with reference toFIGS. 7 and 8. For example, laser drive circuit1200provides A, M, and {circumflex over (M)} to an update circuit capable of determining new weight values according to Eq. (6).

FIG. 13shows a laser drive circuit with dynamic laser diode compensation in accordance with various embodiments of the present invention. Diode drive circuit1300is similar to diode drive circuit1200(FIG. 12) with the exception of basis functions circuits1310. Basis function circuits1310receive both x[n] and x[n−1] and determine basis function outputs according to the basis functions shown, and the compensation value on node715is the sum of the weighted basis function outputs. This combines the approaches ofFIGS. 7 and 12, and results in compensating desired optical power as a function of both the current desired optical power and a past desired optical power. The basis functions may be of the form:

where the basis functions ϕiare functions of both the current desired optical power x[n] and a past desired optical power x[n−1]

In some embodiments, the basis functions ϕimay be decomposed into a product of the basis functions αiand βi. For example, in some embodiments, the basis functions ϕimay take the form:
ϕi(x[n],x[n−1])≈αi(x[n])βi(x[n−1]).  (11)

The weights may be updated as described above with reference toFIGS. 7 and 8. For example, laser drive circuit1300provides A, M, and {circumflex over (M)} to an update circuit capable of determining new weight values according to Eq. (6).

FIG. 14shows a scanning laser projector in accordance with various embodiments of the present invention. Scanning laser projector1400includes image processing component1402, drive circuit with dynamic laser diode compensation1494, red laser module1410, green laser module1420, and blue laser module1430. Light from the laser modules is combined with dichroics1403,1405, and1407to produce combined laser beam1409. Scanning laser projector1400also includes fold mirror1450, drive circuit1470, and MEMS device1414with scanning mirror1416.

In some embodiments, image processing component1402processes video content at1401using two dimensional interpolation algorithms to determine the appropriate spatial image content for each mirror position at which an output pixel is to be displayed. In other embodiments, image processing component1402processes the video content by placing pixels without interpolating. This content is then mapped to desired optical power values on node1493for each of the red, green, and blue laser light sources.

Drive circuit1494receives the desired optical power values on node1493and produces commanded drive values for each of the red, green, and blue laser sources such that the output intensity from the lasers is consistent with the input image content. In some embodiments, this process occurs at output pixel rates in excess of 150 MHz.

Drive circuit1494provides compensation for dynamic nonlinearities in the system as described with reference to previous figures. For example, drive circuit1494may include any of drive circuits700(FIG. 7),1200(FIG. 12), or1300(FIG. 13). Also for example, drive circuit1494may include one or more processing circuits800(FIG. 8). In these embodiments, the accumulation period may correspond to a period of time related to the video. For example, the accumulation period may correspond to one line of video or one frame of video. Also for example, the accumulation period may correspond to less than one line of video.

Combined laser beam109is directed onto an ultra-high speed gimbal mounted two-dimensional bi-axial laser scanning mirror1416. In some embodiments, this bi-axial scanning mirror is fabricated from silicon using MEMS processes. The vertical axis of rotation is operated quasi-statically and creates a vertical sawtooth raster trajectory. The vertical axis is also referred to as the slow-scan axis. The horizontal axis is operated on a resonant vibrational mode of the scanning mirror. In some embodiments, the MEMS device uses electromagnetic actuation, achieved using a miniature assembly containing the MEMS die and small subassemblies of permanent magnets and an electrical interface, although the various embodiments are not limited in this respect. For example, some embodiments employ electrostatic or piezoelectric actuation. Any type of mirror actuation may be employed without departing from the scope of the present invention. The horizontal resonant axis is also referred to as the fast-scan axis.

In some embodiments, raster scan1482is formed by combining a sinusoidal component on the horizontal axis and a sawtooth component on the vertical axis. In these embodiments, output beam1417sweeps back and forth left-to-right in a sinusoidal pattern, and sweeps vertically (top-to-bottom) in a sawtooth pattern with the display blanked during flyback (bottom-to-top).FIG. 14shows the sinusoidal pattern as the beam sweeps vertically top-to-bottom, but does not show the flyback from bottom-to-top. In other embodiments, the vertical sweep is controlled with a triangular wave such that there is no flyback. In still further embodiments, the vertical sweep is sinusoidal. The various embodiments of the invention are not limited by the waveforms used to control the vertical and horizontal sweep or the resulting raster pattern.

A mirror drive circuit1470provides a drive signal to MEMS device1414on node1473. The drive signal includes an excitation signal to control the resonant angular motion of scanning mirror1416on the fast-scan axis, and also includes a slow-scan drive signal to cause deflection on the slow-scan axis. The resulting mirror deflection on both the fast and slow-scan axes causes output beam1417to generate a raster scan1482in field of view1480. In operation, the laser light sources produce light pulses for each output pixel and scanning mirror1416reflects the light pulses as beam1417traverses the raster pattern.

Mirror drive circuit1470also receives a feedback signal from MEMS device1414on node1475. The feedback signal on node1475provides information regarding the position of scanning mirror1416on the fast-scan axis as it oscillates at a resonant frequency. In some embodiments, the feedback signal describes the instantaneous angular position of the mirror, and in other embodiments, the feedback signal describes the maximum deflection angle of the mirror, also referred to herein as the amplitude of the feedback signal.

In operation, drive circuit1470excites resonant motion of scanning mirror1416such that the amplitude of the mirror deflection is substantially constant. This provides for a constant maximum angular deflection on the fast-scan axis as shown in raster scan1482. Drive circuit1470also provides mirror position information to image processing component1402on node1471.

Drive circuit1470may be implemented in hardware, a programmable processor, or in any combination. For example, in some embodiments, drive circuit1470is implemented in an application specific integrated circuit (ASIC). Further, in some embodiments, some of the faster data path control is performed in an ASIC and overall control is provided by a software programmable microprocessor.

Although red, green, and blue laser light sources are shown inFIG. 14, the various embodiments of the invention are not limited by the wavelength of light emitted by the laser light sources. For example, in some embodiments, non-visible light (e.g., infrared light) is emitted instead of, or in addition to, visible light.

The particular dual axis gimbaled MEMS device embodiment is described as an example, and the various embodiments of the invention are not limited to this specific implementation. For example, any combination of scanning mirrors capable of sweeping in two dimensions to reflect a light beam in a raster pattern may be incorporated without departing from the scope of the present invention. Also for example, any combination of scanning mirrors (e.g., two mirrors: one for each axis) may be utilized to reflect a light beam in a raster pattern. Further, any type of mirror drive mechanism may be utilized without departing from the scope of the present invention. For example, in some embodiments, MEMS device1414may use a drive coil on a moving platform with a static magnetic field, an in other embodiments, MEMS device1414may include a magnet on a moving platform with drive coil on a fixed platform. Further, the mirror drive mechanism may include an electrostatic and/or a piezoelectric drive mechanism.

FIG. 15shows a flow diagram of methods in accordance with various embodiments of the present invention. In some embodiments, method1500, or portions thereof, is performed by a drive circuit that provides dynamic compensation for system nonlinearities as described above. In other embodiments, method1500is performed by a series of circuits or an electronic system such as one of drive circuits700(FIG. 7),1200(FIG. 12), and1300(FIG. 13). Method1500is not limited by the particular type of apparatus performing the method. The various actions in method1500may be performed in the order presented, or may be performed in a different order. Further, in some embodiments, some actions listed inFIG. 15are omitted from method1500.

Method1500is shown beginning with block1510. As shown at1510, a value representing a desired optical power is received. In some embodiments, this is a digital value that represents an uncompensated desired power value. At1520, a compensation value is determined as a sum of weighted basis functions of the value of representing the desired optical power. This corresponds to the operation of the basis functions circuits710shown inFIG. 7. Is some embodiments, the compensation value is determined as a sum of weighted basis functions of previous desired optical power values. This corresponds to the operation of the basis function circuits810shown inFIG. 8. In still further embodiments, the compensation value is determined as a function of both the desired optical power value and previous optical power values. This corresponds to the operation of basis function circuits1310as shown inFIG. 13.

At1530, the compensation value is added to the desired optical power value to produce a compensated optical power value. This corresponds to summer716adding the compensation value on node715to the desired optical power value on node701to produce the compensated desired optical power value on node717.

At1540, an inverse laser model (inverse laser model101,FIGS. 7, 12, 13) is used to determine a drive value, and at1550, a laser diode (diode110) is driven with a current (output of DAC/driver102) corresponding to the drive value.

FIG. 16shows a flow diagram of methods in accordance with various embodiments of the present invention. In some embodiments, method1600, or portions thereof, is performed by a drive circuit that provides dynamic compensation for system nonlinearities as described above. In other embodiments, method1600is performed by a series of circuits or an electronic system such as one of drive circuits700(FIG. 7),1200(FIG. 12), and1300(FIG. 13). Method1600is not limited by the particular type of apparatus performing the method. The various actions in method1600may be performed in the order presented, or may be performed in a different order. Further, in some embodiments, some actions listed inFIG. 16are omitted from method1600.

Method1600is shown beginning with block1610. As shown at1610, values representing past basis function outputs are summed. This corresponds to the operation of accumulator772(FIGS. 7, 12, 13) accumulating the basis function outputs over an accumulation period.

At1620, optical powers produced by the laser diode are measured, and at1630, these measured values are summed. In operation, this corresponds to the operation of photodiode730along with integrator732, and ADC734(FIGS. 7, 12, 13). At1640, past desired optical power values are summed. In operation, this corresponds to the operation of accumulator750.

At1650, new weights are determined as a function of past basis function outputs, past desired optical powers, and past measured optical powers. In some embodiments, this corresponds to processing circuit800(FIG. 8) determining new weights in accordance with Eq. (6).

FIG. 17shows a block diagram of a mobile device in accordance with various embodiments of the present invention. As shown inFIG. 17, mobile device1700includes wireless interface1710, processor1720, memory1730, and scanning laser projector1400. Scanning laser projector1400includes dynamic laser diode compensation circuits as described above.

Scanning laser projector1400may receive image data from any image source. For example, in some embodiments, scanning laser projector1400includes memory that holds still images. In other embodiments, scanning laser projector1400includes memory that includes video images. In still further embodiments, scanning laser projector1400displays imagery received from external sources such as connectors, wireless interface1710, a wired interface, or the like.

Wireless interface1710may include any wireless transmission and/or reception capabilities. For example, in some embodiments, wireless interface1710includes a network interface card (NIC) capable of communicating over a wireless network. Also for example, in some embodiments, wireless interface1710may include cellular telephone capabilities. In still further embodiments, wireless interface1710may include a global positioning system (GPS) receiver. One skilled in the art will understand that wireless interface1710may include any type of wireless communications capability without departing from the scope of the present invention.

Processor1720may be any type of processor capable of communicating with the various components in mobile device1700. For example, processor1720may be an embedded processor available from application specific integrated circuit (ASIC) vendors, or may be a commercially available microprocessor. In some embodiments, processor1720provides image or video data to scanning laser projector1400. The image or video data may be retrieved from wireless interface1710or may be derived from data retrieved from wireless interface1710. For example, through processor1720, scanning laser projector1400may display images or video received directly from wireless interface1710. Also for example, processor1720may provide overlays to add to images and/or video received from wireless interface1710, or may alter stored imagery based on data received from wireless interface1710(e.g., modifying a map display in GPS embodiments in which wireless interface1710provides location coordinates).

FIG. 18shows a mobile device in accordance with various embodiments of the present invention. Mobile device1800may be a hand held scanning laser projector with or without communications ability. For example, in some embodiments, mobile device1800may be a scanning laser projector with little or no other capabilities. Also for example, in some embodiments, mobile device1800may be a device usable for communications, including for example, a cellular phone, a smart phone, a tablet computing device, a global positioning system (GPS) receiver, or the like. Further, mobile device1800may be connected to a larger network via a wireless (e.g., cellular), or this device can accept and/or transmit data messages or video content via an unregulated spectrum (e.g., WiFi) connection.

Mobile device1800includes scanning laser projector1400, touch sensitive display1810, audio port1802, control buttons1804, card slot1806, and audio/video (A/V) port1808. None of these elements are essential. For example, mobile device1800may only include scanning laser projector1400without any of touch sensitive display1810, audio port1802, control buttons1804, card slot1806, or A/V port1808. Some embodiments include a subset of these elements. For example, an accessory projector may include scanning laser projector1400, control buttons1804and A/V port1808. A smartphone embodiment may combine touch sensitive display device1810and projector1400.

Touch sensitive display1810may be any type of display. For example, in some embodiments, touch sensitive display1810includes a liquid crystal display (LCD) screen. In some embodiments, display1810is not touch sensitive. Display1810may or may not always display the image projected by scanning laser projector1400. For example, an accessory product may always display the projected image on display1810, whereas a mobile phone embodiment may project a video while displaying different content on display1810. Some embodiments may include a keypad in addition to touch sensitive display1810.

A/V port1808accepts and/or transmits video and/or audio signals. For example, A/V port1808may be a digital port, such as a high definition multimedia interface (HDMI) interface that accepts a cable suitable to carry digital audio and video data. Further, A/V port1808may include RCA jacks to accept or transmit composite inputs. Still further, A/V port1808may include a VGA connector to accept or transmit analog video signals. In some embodiments, mobile device1800may be tethered to an external signal source through A/V port1808, and mobile device1800may project content accepted through A/V port1808. In other embodiments, mobile device1800may be an originator of content, and A/V port1808is used to transmit content to a different device.

Audio port1802provides audio signals. For example, in some embodiments, mobile device1800is a media recorder that can record and play audio and video. In these embodiments, the video may be projected by scanning laser projector1400and the audio may be output at audio port1802.

Mobile device1800also includes card slot1806. In some embodiments, a memory card inserted in card slot1806may provide a source for audio to be output at audio port1802and/or video data to be projected by scanning laser projector1400. Card slot1806may receive any type of solid state memory device, including for example secure digital (SD) memory cards.

FIG. 19shows a head-up display system in accordance with various embodiments of the invention. Projector1400is shown mounted in a vehicle dash to project the head-up display at1900. Although an automotive head-up display is shown inFIG. 19, this is not a limitation of the present invention. For example, various embodiments of the invention include head-up displays in avionics application, air traffic control applications, and other applications.

FIG. 20shows eyewear in accordance with various embodiments of the invention. Eyewear2000includes projector1400to project a display in the eyewear's field of view. In some embodiments, eyewear2000is see-through and in other embodiments, eyewear2000is opaque. For example, eyewear2000may be used in an augmented reality application in which a wearer can see the display from projector1400overlaid on the physical world. Also for example, eyewear2000may be used in a virtual reality application, in which a wearer's entire view is generated by projector1400. Although only one projector1400is shown inFIG. 20, this is not a limitation of the present invention. For example, in some embodiments, eyewear2000includes two projectors; one for each eye.

FIG. 21shows a gaming apparatus in accordance with various embodiments of the present invention. Gaming apparatus2100includes buttons2102, display2110, and projector1400. In some embodiments, gaming apparatus2100is a standalone apparatus that does not need a larger console for a user to play a game. For example, a user may play a game while watching display2110and/or the projected content at1480. In other embodiments, gaming apparatus2100operates as a controller for a larger gaming console. In these embodiments, a user may watch a larger screen tethered to the console in combination with watching display2110and/or projected content at1480.