Adaptive illuminator sequencing

An eyewear device is disclosed including an illumination device including illumination sources, each illumination source including a first illuminator, a second illuminator, and a third illuminator, and a spatial light modulator coupled to the illumination device to control when each of the first, second, and third illuminators are on during an illumination frame. The spatial light modulator is adapted to turn on the first illuminator while the second and third illuminators are off, turn on the second illuminator while the first and third illuminators are off, turn on the third illuminator while the first and second illuminators are off during a third time period of the illumination frame, and turn on the first, second and third illuminators during a fourth time period. An illumination method is also disclosed.

FIELD OF THE INVENTION

The present invention relates to light projectors and, more particularly, to projectors with adaptive illuminators.

BACKGROUND OF THE INVENTION

Consumer electronics devices utilize projectors to display images to their users. The projectors include illuminators such as LEDs to create light for displaying the images. In environments where the ambient level of light is high, the projectors may increase the current to the illuminators to boost brightness in order to improve visibility. Increasing the current to the illuminators, however, causes the illuminators to generate heat, which limits the usefulness of such an approach.

DETAILED DESCRIPTION OF THE INVENTION

The term “coupled” or “connected” as used herein refers to any logical, optical, physical or electrical connection, link or the like by which electrical or magnetic signals produced or supplied by one system element are imparted to another coupled or connected element. Unless described otherwise, coupled or connected elements or devices are not necessarily directly connected to one another and may be separated by intermediate components, elements or communication media that may modify, manipulate or carry the electrical signals. As used herein, the term lens covers transparent or translucent pieces of glass or plastic having curved and/or flat surfaces that cause light to converge/diverge or that cause little or no convergence/divergence. The term “about” as used herein refers to a range of values surrounding an actual value, i.e., +/−10%.

The orientations of an eyewear device, associated components and any complete devices as shown in any of the drawings, are given by way of example only, for illustration and discussion purposes. In operation, the eyewear device may be oriented in any other direction suitable to the particular application of the eyewear device, for example up, down, sideways, or any other orientation. Also, to the extent used herein, any directional term, such as front, rear, inwards, outwards, towards, left, right, lateral, longitudinal, up, down, upper, lower, top, bottom, side, horizontal, vertical, and diagonal are used by way of example only, and are not limiting as to direction or orientation of any depth-capturing camera or component of the depth-capturing camera constructed as otherwise described herein.

FIG. 1depicts an eyewear device100. Eyewear device100includes a support structure that has a frame102, a right temple104a, and a left temple104b. Frame102includes a right rim106athat supports a right lens108aand left rim106bthat supports a left lens108b. A bridge107connects the left and right rims106aand106band is adapted to receive a nose of the wearer. Eyewear device100additionally includes a spatial light modulator (SLM)110, an ambient light sensor (ALS)112, and a temperature sensor114, which will be described in further detail below.

Eyewear device100additionally includes an optional chunk116between frame102and temple104ato house electronic components. Chunk116may be attached to frame102or integrated into frame102. A hinge117may connect temple104ato chunk116to enable folding of temple104atoward frame102in a conventional manner. Although an eyewear device example is provided, it is to be understood that the examples described herein may be applied to other electronic devices including color illuminator light sources.

FIG. 2conceptually depicts a portion of eyewear device100for use in describing optical characteristics. An illumination device200projects beams of light202under control of SLM110(FIG. 1). Projection optics204such as light guides and mirrors direct beams of light202into a waveguide206. In this example, lens106adefines the waveguide206. Beams of light202are internally reflected by waveguide206and exit waveguide206at an exit coupler such as a diffractive grating or coating for viewing in a view area by an eye208of a wearer of eyewear device100.

FIG. 3depicts hardware components300for use in eyewear device100. In addition to SLM110, ALS112, thermistor114, and illumination device200described above, hardware components300include a system controller302, a memory304, current controller312, and three illuminators. The three illuminators include a red illuminator306such as a red light emitting diode (LED) adapted to emit light at a first frequency associated with the color red, a green illuminator308such as a green LED adapted to emit light at a second frequency associated with the color green, and a blue illuminator310such as a green LED adapted to emit light at a third frequency associated with the color red. System controller302and current controller312may each be a microcontroller adapted to implement the functions described herein. Memory304may be non-volatile memory such as flash memory or erasable read only memory.

System controller302receives temperature values from thermistor114and ambient light levels from ALS112via transmission lines. System controller retrieves timing information for tuning on the illuminators from memory304based on the ambient light levels. System controller302also configures SLM110and current controller312based on ambient light levels and/or temperature to project light beams202. For example, system controller302may configure SLM110for high/low brightness in high/low ambient light conditions and may configure current controller312to reduce current (e.g., in accordance with current derating curves) if heat generation by the illuminators could damage the device.

FIG. 4Adepicts an example timing sequence for a four-color sequence (red, green, blue, white) to depict the color white. The timing sequence is over an illumination sequence of 16.67 ms (representing a 60 Hz frame of video). Because the sequence occurs with a short period of time from the human eye's perspective, the eye of a user interprets the combination of colors as occurring simultaneously rather than the colors individually. In the timing sequence ofFIG. 4A, red illuminator (R)306is solely illuminated for a duration equal to t1-t0(20%), green illuminator (G)308is solely illuminated for a duration equal to t2-t1(40%), blue illuminator (B)310is solely illuminated for a duration equal to t3-t2(10%), and all three illuminators (RGB; White; W)306,308, and310are illuminated for a duration equal to t4-t3(30%). In a conventional system, the illuminators are not simultaneously lit. In order to increase brightness in such system, current to the illuminators are increased. Illuminating the illuminators simultaneously some of the time in accordance with the timing sequence inFIG. 4Aenables more light to be delivered than in conventional system without increasing current. Additionally, the illuminators are still turned off periodically to allow for cooling.

FIG. 4Bdepicts an example timing sequence for a seven-color sequence (red, green, blue, cyan, magenta, yellow, white) to depict the color white. The timing sequence is over an illumination sequence of 16.67 ms. In the timing sequence ofFIG. 4B, red illuminator (R)306is solely illuminated for a duration equal to t1-t0(20%), green illuminator (G)308is solely illuminated for a duration equal to t2-t1(30%), blue illuminator (B)310is solely illuminated for a duration equal to t3-t2(10%), the green illuminator308and blue illuminator310(GB; Cyan; C) are illuminated for a duration equal to t4-t3(10%), the red illuminator306and blue illuminator310(RB; Magenta; M) are illuminated for a duration equal to t5-t4(10%), the red illuminator306and green illuminator308(RG; Yellow; Y) are illuminated for a duration equal to t6-t5(10%), and all three illuminators (RGB; White; W)306,308, and310are illuminated for a duration equal to t7-t6(10%). Illuminating the illuminators simultaneously some of the time in accordance with the timing sequence inFIG. 4Benables more light to be delivered than in conventional system without increasing current. Additionally, the illuminators are still turned off periodically to allow for cooling.

In an example, when displaying an overlapping color such as white, the red illuminator306is on during both tRand tW, and off during tGand tB, the green illuminator308is on during both tGand tWand off during tRand tB, and the blue illuminator310is on during both tBand tW, and off during tRand tG.

In an example, when displaying a non-overlapping color such as red, the red illuminator306is on during tR, but is off during tW. In another example, when displaying a non-overlapping color such as red, the red illuminator306is on during both tRand tW(with the green illuminator308and the blue illuminator310off during tW).

FIG. 5depicts an equation for use in determining characteristics such as current and timing values to configure the illuminators in order to produce a desired color white having particular intensity or brightness. Each illuminator has an International Commission on Illumination (CIE) tristimulus value (X, Y, Z), which is a three-dimensional value. An alternative representation of the tristate value is x, y, Y, where x=X/(X+Y+Z), y=Y/X+Y+Z, and Y represents intensity or brightness. The “on” time for each illuminator is represented by “t” and is the duration when the illuminator is on, during which current “i” is supplied to the illuminator. When off, the illuminator cools down thermally. To maintain color points (i.e., chromaticity values), the current (i) supply to each illuminator is set to a constant value. For example, the current value for the red illuminator306when showing red, magenta, yellow, and white is constant throughout the timing sequence.

In an example, the system adjusts brightness to address visibility based on ambient light conditions by adapting the duration when all illuminators are on (tW) for a four color system and (tW, tC, tM, and tY) for a seven color system. There is a direct correlation between system brightness and time duration for overlapping illuminator colors tW(for a four color system) and tW, tC, tM, and tY(for a seven color system). An optimal set of operational parameters (current and duration for each illuminator) are chosen for each system. For example, the eyewear100optimizes the SLM110to run at a brightness of Y0for an ambient temperature of T0, a brightness of Y1for an ambient temperature of T1, and a brightness of Y2for an ambient temperature of T2. For higher ambient light levels, the duration of the overlapping color(s) is increased to improve visibility. Conversely, for lower ambient light levels, the duration of the overlapping color(s) is decreased to reduce power consumption. When the duration of the overlapping color(s) is high/low, the duration of the non-overlapping colors (tR, tG, and tB) are increased/reduced to compensate for the time in the illumination frame that the overlapping color(s) are not in use.

Determination of the optimal operational parameters takes into account illuminator temperature, e.g., via a thermistor114positioned adjacent the illuminator. The positions adjacent the illuminator include areas providing an accurate representation of illuminator temperature (either actual or correlated). Touch temperature on the temple of104anear (e.g., within half of centimeter) of the illuminators has good correlation with the actual temperature of the illuminators. Touch temperature may be an operation parameter set at a maximum value of 55 degrees Celsius, as an example.

Conventional systems address bright ambient light conditions by increasing current to the illuminators to increase brightness without adjusting illuminator on duration times, which has limited effectiveness due to thermal limitation of the illuminators. Additionally, such system typically require an active control loop including a color sensor to maintain the system white point due to the non-linear brightness response of illuminators such as LEDs to current increases.

By cycling the illuminators, for example, as taught inFIGS. 4A and 4B, the system can maintain the illuminator temperature in a safe operating range for a longer operational time. Additionally, active control loops such as those found in conventional system can be avoided.

FIG. 6depicts a flow chart of example steps for use in displaying images by an electronic device such as eyewear100. Although eyewear device100is described in the following example, it is apparent from the description herein that other types of electronic device where illuminators generate light may benefit from implementing the method. Additionally, one of skill in the art will understand suitable modification from the description here such as omission of one or more of the steps and/or performance in a different order.

At step602, initiate request to turn on the light projector. In an example, the light projector may include SLM110and illumination device200. System controller302of eyewear device100may initiate the request to turn on SLM110and illumination device200, e.g., in response to an instruction to display information via lens108aof eyewear device100.

At step604, read ambient light sensor. System controller302may read an ambient light level by periodically polling ALS112. ALS112may be positioned on eyewear device100to provide an accurate reading of the light level the user is experiencing while wearing the eyewear device100(or a value with good correlation to the light level).

At step606, obtain illuminator timing and current settings. System controller302may read values from a lookup table in memory304. The lookup table may include multiple timing entries where each timing entry corresponds to a different ambient light level. In this example, system controller302reads the timing values from the lookup table associated with the current ambient light level read from ALS112. For a four color sequence, the timing sequence includes four timing values (tR, tG, tB, and tW) for each of multiple ambient light level ranges. For a seven color sequence, the timing sequence includes seven timing values (tR, tC, tB, tC, tM, tY, and tW) for each of multiple ambient light level ranges. The same or a different lookup table may include initial current settings for the illuminators.

At step608, load the timing sequence into an adaptive spatial light modulator. System controller302may load the timing sequence from step606into SLM110, which in turn, controls current controller312to selectively switch current on/off to illuminators306,308, and310.

At step610, load current settings into current controller. System controller302may load the current setting from step606into SLM110.

At step612, turn on the projector. System controller302may turn on SLM110and current controller312after loading timing sequences into SLM110and loading current settings into current controller312.

At step614, read temperature associated with the projector illuminators. System controller302may periodically read the temperature from thermistor114. The temperature may be an actual temperature of the illuminators from a position in very close proximity or a correlated temperature from a nearby location such as on or near the surface of the temple104acontaining the illuminators (e.g., touch temperature).

At step616, determine if temperature is within an acceptable range. System controller302may compare the periodically read temperature values to acceptable temperature limits (e.g., a threshold value selected below an acceptable touch temperature of 55 degrees Celsius, as an example). If the temperature is acceptable, at step618, the system waits a predetermined period of time (e.g., 10 seconds) before reading the temperature again. System controller302repeats steps614,616, and618for as long as the temperature from thermistor114is below the acceptable range.

At step620, when the read temperature is not within the acceptable range, current to the illuminators is reduced. System controller302may instruct current controller312to reduce current by a predetermined amount (e.g., 1% or approximately 1%). Current to the individual illuminators (e.g., iR, iG, and iB) may be reduced proportionally using current derating curves for the individual illuminators in order to maintain the white point of the system.

At step622, the system waits a predetermined period of time (e.g., 10 seconds) before reading the temperature again. System controller302repeats steps614,616,620and622for as long as the temperature from thermistor114is at or above the acceptable range.

System controller302may additionally adjust timing of illuminators if ambient light levels change while the projector is on. For example, if ambient light levels increase above a predetermined amount (e.g., 5,000 lux), system controller302may increase the percentage on time of the overlapping colors (e.g., tWin a four color system and tC, tM, tY, and tWin a seven color system) to improve visibility. Conversely, if ambient light levels decrease below a predetermined amount (e.g., 5,000 lux), system controller302may decrease the percentage on time of the overlapping colors (e.g., tWin a four color system and tC, tM, tY, and tWin a seven color system) to reduce power consumption. When the duration of the overlapping color(s) is reduced/increased, the duration of the non-overlapping colors (tR, tG, and tB) may be increased/reduced to compensate for the time in the illumination frame that the overlapping color(s) are no longer in use.

While the foregoing has described what are considered to be the best mode and other examples, it is understood that various modifications may be made therein and that the subject matter disclosed herein may be implemented in various forms and examples, and that they may be applied in numerous applications, only some of which have been described herein. It is intended by the following claims to claim any and all modifications and variations that fall within the true scope of the present concepts.