Electronics Guide

OLED Micro-Displays

Organic light-emitting diode (OLED) micro-displays represent a leading technology for VR applications due to their self-emissive nature, which enables true black levels, infinite contrast ratios, and rapid pixel response times. Each pixel in an OLED micro-display contains organic compounds that emit light when electrical current passes through them, eliminating the need for a backlight and enabling extremely thin form factors.

High-resolution OLED micro-displays for VR achieve pixel densities exceeding 3000 pixels per inch, with individual pixels measuring less than 10 micrometers. Silicon-based OLED (OLEDoS) technology deposits organic layers directly onto silicon backplanes that contain the pixel drive circuits, enabling the high resolutions and fast switching speeds essential for immersive applications. Response times measured in microseconds virtually eliminate motion blur and reduce latency-induced visual artifacts.

Challenges for OLED micro-displays include achieving sufficient brightness for AR applications where displayed images must compete with ambient illumination, managing differential aging of organic materials across color channels, and scaling production while maintaining the tight tolerances required for high-resolution devices.

LCD Micro-Displays

Liquid crystal display (LCD) micro-displays use liquid crystal modulators combined with separate illumination sources to create images. Liquid crystal on silicon (LCoS) technology forms images by reflecting polarized light from a silicon backplane through a liquid crystal layer that modulates polarization on a pixel-by-pixel basis. High-temperature polysilicon (HTPS) LCD micro-displays operate in transmissive mode, with light passing through the liquid crystal layer.

LCoS micro-displays offer advantages in brightness and color accuracy, as the reflecting nature allows high light utilization efficiency when combined with powerful LED or laser illumination. Pixel densities comparable to OLED micro-displays are achievable, and the technology benefits from mature manufacturing processes. However, LCD technologies inherently exhibit slower response times than OLED, potentially causing motion artifacts, and achieving true black levels is challenging due to light leakage through liquid crystal elements in their dark state.

Micro-LED Displays

Micro-LED technology represents an emerging frontier for AR/VR micro-displays, combining the self-emissive advantages of OLED with the stability and brightness potential of inorganic LED materials. Arrays of microscopic gallium nitride LEDs, each measuring only a few micrometers, can achieve brightness levels orders of magnitude higher than OLED while offering exceptional reliability and color saturation.

The high brightness of micro-LED displays makes them particularly attractive for AR applications, where displayed images must remain visible against bright outdoor environments. However, manufacturing challenges in producing and assembling millions of microscopic LEDs with the precision required for high-resolution displays, combined with difficulties achieving efficient red emission from gallium nitride materials, have limited commercial deployment. Research continues on mass transfer techniques, color conversion approaches, and monolithic integration methods to overcome these obstacles.

Laser Beam Scanning Displays

Rather than using an array of fixed pixels, laser beam scanning (LBS) displays create images by rapidly scanning modulated laser beams across the visual field. Microelectromechanical systems (MEMS) mirrors direct red, green, and blue laser beams in raster or Lissajous patterns while modulating intensity to form images. The effective resolution depends on the scanning frequency and modulation bandwidth rather than physical pixel structures.

LBS systems offer exceptional color saturation due to the narrow spectral emission of laser sources, and the scanning approach can produce very compact optical engines. The technology is well-suited to certain waveguide-based AR architectures. Challenges include achieving sufficient brightness uniformly across the scanned field, managing speckle artifacts inherent to coherent laser light, and ensuring eye safety while meeting brightness requirements.

Architecture and Design

Modern display drivers for micro-displays integrate multiple functions onto a single silicon die. Digital interfaces receive image data from the system processor, typically using MIPI DSI, LVDS, or proprietary high-speed serial protocols. Frame buffers and timing controllers manage data flow to match display requirements. Digital-to-analog converters translate pixel values into voltage or current levels for each pixel, while output drivers deliver these signals with the current capability and speed required by the display technology.

For OLED micro-displays, drivers must provide precisely controlled current to each pixel, as OLED brightness depends on current rather than voltage. Compensation circuits account for variations in pixel characteristics and aging effects that could otherwise cause non-uniform brightness. For LCD micro-displays, drivers provide voltage waveforms that control liquid crystal orientation while avoiding DC components that could damage the liquid crystal material over time.

High Dynamic Range Support

Immersive displays increasingly support high dynamic range (HDR) content to enhance realism and visual impact. Display drivers must accommodate wider color gamuts and greater brightness ranges, typically requiring higher bit depth in the digital-to-analog conversion chain. Local dimming control, where different regions of the display operate at different brightness levels, demands additional processing and control capabilities.

HDR display drivers implement sophisticated tone mapping and gamma correction to translate content mastered for specific HDR standards into appropriate drive signals for the particular display characteristics. These functions may execute in real-time hardware or rely on preprocessing by system graphics processors, depending on system architecture and latency requirements.

Low Latency Operation

Minimizing motion-to-photon latency is critical for comfortable AR/VR experiences, as delays between head movement and corresponding display updates cause disorientation and nausea. Display drivers contribute to system latency through buffering, processing time, and scan-out delays. Advanced driver designs minimize internal buffering, implement predictive algorithms, and support high refresh rates exceeding 90 Hz to reduce perceived latency.

Rolling scan-out, where the display updates progressively from top to bottom, introduces temporal variation across the image that can interact poorly with head tracking systems. Global shutter operation, updating all pixels simultaneously, eliminates this variation but requires additional circuit complexity. Some systems implement partial rolling updates or predictive warping to balance these considerations.

LED Illumination Systems

Light-emitting diode illumination systems provide the light source for LCD and LCoS micro-displays. Sequential color illumination cycles through red, green, and blue LEDs rapidly, with the display showing the corresponding color component synchronized to each illumination phase. This field-sequential color approach allows each pixel to display all three colors, maximizing effective resolution, but requires display switching speeds three times faster than the frame rate.

Alternatively, color filter systems use white LED illumination with colored filters at each pixel, similar to conventional LCD displays. This approach relaxes display speed requirements but reduces effective resolution and light efficiency as each pixel only transmits one color. LED illumination systems require thermal management to maintain consistent color and brightness as operating temperature varies.

Laser Illumination

Laser illumination offers advantages in color gamut, brightness, and optical system design. The narrow spectral emission of laser diodes enables coverage of wide color gamuts exceeding the Rec. 2020 standard, producing more saturated and vivid colors than LED illumination. Laser sources can achieve higher brightness from smaller emitting areas, simplifying optical system design and enabling more compact modules.

Laser illumination introduces additional design considerations including speckle management, where the coherent nature of laser light creates granular interference patterns that degrade image quality. Techniques for speckle reduction include wavelength diversity, angular diversity, and temporal averaging using vibrating diffusers or scanning elements. Eye safety considerations require careful power management and fail-safe mechanisms.

Pupil Forming Optics

Optical engines for waveguide-based AR systems must form the image at an appropriate pupil plane for coupling into the waveguide input. This typically requires telecentric optical designs that produce parallel chief rays across the image field. The pupil size and position must match the input coupler characteristics, often requiring precision alignment mechanisms and active adjustment during manufacturing.

Folded optical paths using prisms and mirrors reduce optical engine length, critical for achieving acceptable headset form factors. Polarization management becomes important when using polarization-sensitive display technologies like LCoS, requiring carefully designed polarizing beam splitters and wave plates to maintain high contrast and efficiency.

Direct Projection

The simplest projection approach places magnifying optics directly in front of the micro-display, enlarging the image to fill the viewer's field of view. Single-lens or multi-element eyepieces magnify the micro-display image while providing appropriate focal distance for comfortable viewing. This approach dominates current VR headset designs due to its optical simplicity and high efficiency.

Fresnel lens designs reduce the weight and thickness of high-power magnifying optics by replacing thick curved surfaces with thin elements containing concentric grooves that provide equivalent optical power. However, Fresnel structures can introduce artifacts including visible groove patterns and increased stray light. Pancake optics use polarization-based folded optical paths to achieve thin form factors with high image quality, though at the cost of reduced light efficiency.

Birdbath and Catadioptric Systems

Birdbath optical architectures combine reflective and transmissive elements to fold the optical path while maintaining image quality. A semi-transparent combiner angled in front of the eye reflects an image from a display positioned above or below the line of sight. This approach enables see-through capability for AR applications while accommodating larger displays than waveguide systems typically support.

Catadioptric designs combining curved mirrors with refractive corrector elements can achieve wide fields of view with relatively compact form factors. The folded optical path reduces system length, and properly designed mirror surfaces can correct aberrations efficiently. However, achieving a thin, lightweight form factor suitable for all-day wear remains challenging with birdbath approaches.

Waveguide Display Systems

Waveguide combiners represent the leading technology for lightweight AR glasses with see-through capability. Light from the optical engine couples into a transparent waveguide plate via input couplers, propagates through the waveguide by total internal reflection, and couples out toward the eye via output couplers. The waveguide acts simultaneously as a light pipe and a transparent window through which the user sees the real world.

Different coupling technologies offer distinct trade-offs. Diffractive waveguides use surface relief gratings or volume holograms to couple light in and out of the waveguide. Reflective waveguides employ partially reflective mirror surfaces. Holographic waveguides can combine multiple functions including color selectivity and optical power into thin holographic elements. Each approach presents different challenges in achieving uniform brightness, wide field of view, high efficiency, and minimizing artifacts.

Pupil Replication

Waveguide systems inherently perform pupil replication as light bounces along the waveguide, coupling out at multiple positions to create an array of exit pupils. The spacing and uniformity of these replicated pupils determine the effective eye-box size and viewing quality across different eye positions. Careful design of output coupler strength variation along the waveguide can produce uniform brightness across the expanded eye-box.

Two-dimensional pupil expansion requires either crossed one-dimensional expanders or more complex two-dimensional grating structures. Crossed expansion typically uses separate horizontal and vertical expansion stages, potentially in different waveguide layers. True two-dimensional gratings can achieve expansion in a single layer but require sophisticated diffractive structures and may introduce additional artifacts.

Exit Pupil Steering

Rather than creating a static large eye-box, exit pupil steering dynamically moves a smaller high-quality exit pupil to track the viewer's eye position. Eye tracking systems determine gaze direction, and beam steering mechanisms redirect the displayed image accordingly. This approach can achieve high image quality across a wide effective eye-box without the uniformity and efficiency challenges of large static expansion.

Steering mechanisms include mechanically tilting optical elements, liquid crystal beam steering devices, and switchable holographic elements that select among multiple output directions. The response speed must be sufficient to track natural eye movements, which can exceed 500 degrees per second during saccades, requiring either predictive algorithms or very fast steering mechanisms.

Uniformity Enhancement

Waveguide systems often exhibit brightness variations across the eye-box due to variable coupling efficiency along the waveguide length and non-uniform pupil replication. Compensation techniques include designed variation in output coupler efficiency, digital pre-correction in the display driver, and hybrid approaches combining optical and electronic methods.

Angular uniformity ensures consistent image quality as the eye rotates within the eye-box. Different parts of the image may arrive via different optical paths, potentially exhibiting varying aberrations, brightness, or color. Optimizing the optical design for the full range of viewing angles, combined with calibration-based electronic correction, addresses these variations.

Interaction with Eye Tracking

Eye tracking enables optimization strategies that adapt to the viewer's instantaneous gaze direction. Foveated rendering concentrates computational resources on the region the viewer is directly looking at, reducing overall rendering load while maintaining perceived quality. Display systems can similarly allocate their performance budgets, providing highest quality in the foveal region with acceptable quality in the periphery.

Gaze-contingent aberration correction applies corrections specific to the current gaze direction, accounting for aberrations that vary across the field of view. This approach can achieve better average image quality than fixed corrections designed for worst-case performance, at the cost of eye tracking system requirements and associated latency considerations.

Optical Design Approaches

Wide-FOV optical systems must manage aberrations that increase rapidly with field angle. Multi-element designs use combinations of lenses with different powers and dispersions to correct chromatic and geometric aberrations across the full field. Aspherical and freeform surfaces provide additional design degrees of freedom for aberration correction, though at increased manufacturing cost and complexity.

Catadioptric designs combining mirrors and lenses can achieve very wide fields of view with relatively compact form factors. Curved display surfaces conforming to the optical design can reduce aberration correction requirements. However, curved micro-displays present their own manufacturing and driving challenges.

Tiled and Multi-Element Systems

Rather than achieving wide FOV with a single optical system, tiled approaches combine multiple narrower-field displays to cover a larger total field. Each tile uses optics optimized for its portion of the overall field, potentially achieving better image quality than a single wide-field system. Careful alignment and seamless blending at tile boundaries are essential for avoiding visible discontinuities.

Multi-focal systems use multiple display planes at different apparent distances to extend the useful accommodation range. While primarily addressing vergence-accommodation conflict, this approach can also provide benefits for wide-FOV systems by optimizing each plane for a different portion of the visual field.

Waveguide FOV Limitations

Waveguide combiners face fundamental FOV limitations related to the angular range that can propagate within the waveguide by total internal reflection. The critical angle of the waveguide material and the refractive index of surrounding media determine the maximum propagation angle, which translates to a limited input/output coupling angle range.

Higher refractive index materials extend the angular range but increase weight and Fresnel reflections. Multiple waveguide layers, each handling a different angular range, can extend total FOV at the cost of thickness and complexity. Novel coupler designs including two-dimensional gratings, metagratings, and volume holographic structures continue to push the achievable FOV limits of waveguide systems.

Angular Resolution Requirements

Human visual acuity varies across the visual field, reaching approximately 60 pixels per degree (PPD) in the central fovea under optimal conditions. Matching this acuity across a 100-degree field of view would require approximately 6000 pixels per eye in each dimension. Current VR systems typically achieve 15-25 PPD, resulting in visible pixel structure commonly called the screen-door effect.

Achieving higher angular resolution requires either smaller pixels, which challenges manufacturing and optical system capabilities, or larger overall display size, which increases weight and optical system complexity. Foveated displays that provide maximum resolution only where the eye is looking can achieve high perceived resolution with reduced total pixel count.

Sub-Pixel Rendering

Sub-pixel rendering techniques exploit the color filter pattern of conventional displays to achieve apparent resolution beyond the physical pixel count. By treating individual color sub-pixels as independently addressable luminance elements, properly designed rendering algorithms can position edges and fine details at positions between full pixel boundaries.

For micro-displays with RGB stripe patterns, sub-pixel rendering can provide horizontal resolution improvement up to approximately three times the pixel count, though with some potential for color fringing artifacts. Pentile and other non-stripe arrangements complicate sub-pixel rendering but may offer overall efficiency advantages. The effectiveness of sub-pixel rendering depends on the optical system MTF and the specific viewing conditions.

Display Switching and Multi-Frame Synthesis

Rapid display switching techniques create apparent resolution exceeding the physical display resolution by showing multiple offset images in rapid succession. If the display and optical system can shift the image position by sub-pixel increments between frames, the time-averaged result exhibits higher effective resolution than any single frame.

Implementation requires displays capable of frame rates several times the nominal refresh rate, precise image shifting mechanisms, and rendering pipelines that generate the appropriate shifted sub-images. The human visual system's temporal integration characteristics determine how effectively multiple frames combine into perceived higher resolution. Motion during the multi-frame sequence must be carefully managed to avoid artifacts.

Optical Correction Methods

Traditional optical correction uses combinations of positive and negative lens elements made from glasses with different dispersion characteristics to balance the chromatic effects. Achromatic doublets and more complex apochromatic designs minimize chromatic aberration across visible wavelengths. However, correcting chromatic aberration optically adds weight, thickness, and cost to the optical system.

Diffractive optical elements exhibit chromatic dispersion opposite in sign to refractive elements, enabling hybrid designs that achieve chromatic correction with fewer elements. Metasurface optics can provide wavelength-dependent phase profiles that correct chromatic aberration in extremely thin structures, though manufacturing and efficiency challenges remain areas of active development.

Digital Pre-Correction

Electronic chromatic aberration correction applies pre-distortion to the displayed image such that after passing through the aberrated optical system, the final image appears correct. Separate correction maps for red, green, and blue channels shift each color component to compensate for the wavelength-dependent focusing and distortion of the optics.

Digital correction requires accurate characterization of the optical system's chromatic behavior across the full field, stored as correction lookup tables or parametric models. The correction is typically applied in the rendering pipeline or display driver, adding computational load and potentially introducing quantization artifacts if bit depth is insufficient. Lateral chromatic aberration (different magnification for different colors) is straightforward to correct digitally, while longitudinal chromatic aberration (different focus distance) cannot be fully corrected without multi-focal display capability.

Pre-Distortion Rendering

The standard approach to distortion compensation renders images with the inverse of the optical system's distortion, such that when viewed through the optics, distortions cancel and the image appears correct. Distortion maps characterizing the optical system are incorporated into the rendering pipeline, typically as a post-processing step that resamples the rendered image according to the inverse distortion function.

Pre-distortion rendering must account for distortion variations with eye position and gaze direction. For systems without eye tracking, designs typically optimize for a nominal eye position. Eye-tracked systems can apply position-dependent distortion correction, providing accurate compensation as the eye moves within the eye-box.

Distortion Calibration

Accurate distortion compensation requires precise calibration of the actual optical system distortion, which may vary between individual units due to manufacturing tolerances. Factory calibration captures distortion characteristics of each headset, storing calibration data for use by the compensation algorithms.

Calibration procedures typically involve displaying known patterns and measuring their appearance through the optical system using cameras or specialized measurement fixtures. Advanced calibration may characterize distortion as a function of eye position and gaze direction, requiring more complex measurement setups but enabling superior correction fidelity.

Sources of Ghost Images

Fresnel reflections at lens surfaces create reflected images that can reach the eye along unintended paths. In multi-element lens systems, light reflecting between different surfaces can form focused ghost images at various positions relative to the main image. Waveguide systems can produce ghosts from light coupling out at incorrect positions or from multiple interactions with coupler structures.

The severity of ghost images depends on the reflectivity of optical surfaces, the geometry of the optical system, and the brightness contrast between intended and ghost images. Bright image content on dark backgrounds tends to make ghost images most visible, while diffuse ambient light reduces ghost visibility by raising the overall background level.

Mitigation Techniques

Anti-reflection coatings on optical surfaces reduce Fresnel reflections from the typical 4% per surface for uncoated glass to below 0.5% with multilayer coatings. Coatings must be designed for the appropriate wavelength range and angle of incidence distribution for the specific optical system. Index-matching between cemented elements eliminates reflection at those interfaces.

Optical design can position ghost-forming reflections such that resulting ghosts fall outside the viewing field or are sufficiently defocused to be unobtrusive. Baffles and absorbing surfaces block ghost-forming ray paths. In waveguide systems, output coupler designs that minimize light coupling in unwanted directions reduce waveguide-specific ghost mechanisms.

Electronic Ghost Suppression

When optical methods cannot completely eliminate ghosts, electronic compensation can reduce their visibility. If ghost image formation is characterized through calibration, the displayed image can be modified to reduce brightness in regions that would otherwise create visible ghosts. This approach trades some dynamic range for reduced ghost visibility.

More sophisticated approaches model ghost formation as a function of image content and apply content-adaptive compensation. Machine learning techniques can characterize complex ghost relationships that resist analytical modeling, enabling more effective electronic suppression of residual ghost artifacts.

Display-Level Contrast

The micro-display itself sets the foundation for system contrast. OLED displays achieve excellent native contrast because pixels that are off emit no light, providing true blacks. LCD-based displays require careful light management to minimize leakage in the dark state, including high-quality polarizers, compensator films, and backlight control.

Local dimming in LCD systems varies backlight intensity across zones to reduce light behind dark image regions, improving effective contrast ratio beyond the liquid crystal's native contrast. The resolution and responsiveness of local dimming zones affect how well this technique works with varied image content.

Optical System Contrast

Optical systems can degrade display contrast through scattered light, ghost images, and internal reflections. Stray light from bright image areas or external sources scattering onto dark image regions raises the apparent black level, reducing effective contrast. Managing stray light requires attention to surface quality, anti-reflection coatings, baffling, and absorptive treatments throughout the optical path.

For AR systems, contrast between virtual content and the real world depends on the combiner's ability to separate virtual image light from ambient scene light. Higher combiner reflectivity improves virtual content brightness but can reduce real-world visibility. Dynamic combiners that modulate transparency in synchronization with displayed content can improve effective contrast for AR applications.

Optical Efficiency

Maximizing the fraction of light from the display that reaches the viewer's eye reduces the source brightness required for any given perceived brightness. High-efficiency optical designs minimize surface reflections, absorption in optical materials, and vignetting at aperture boundaries. For waveguide systems, coupling efficiency at input and output interfaces significantly impacts overall brightness.

Polarization state management affects efficiency in systems using polarization-sensitive components. Maintaining correct polarization through the optical system and minimizing polarization-dependent losses can substantially improve efficiency in LCoS-based systems and certain waveguide architectures.

Dynamic Brightness Control

Adaptive brightness control adjusts display output based on content and viewing conditions. In VR, brightness can be optimized for the current scene content, reducing power consumption for dark scenes while providing full brightness when needed. In AR, ambient light sensors enable automatic adjustment to maintain visible contrast against varying environmental illumination.

Content-aware brightness management recognizes that human perception of brightness is relative rather than absolute. Tone mapping techniques can create satisfying visual experiences with limited peak brightness by managing the distribution of brightness values within the displayable range. High dynamic range content requires careful mapping to the capabilities of the specific display system.

Display Power Reduction

OLED displays consume power proportional to displayed brightness, enabling significant savings with dark content. Content-aware rendering that avoids unnecessarily bright regions reduces display power. For LCD systems, backlight power dominates, and local dimming or dynamic backlight control based on content reduces consumption while maintaining perceived brightness.

Foveated display architectures that provide full resolution and brightness only in the gaze direction while reducing quality in the periphery can substantially reduce display power. Implementation requires eye tracking with sufficient accuracy and latency to direct resources effectively to the foveal region.

Driver and Processing Efficiency

Display driver circuits consume significant power, particularly at high resolutions and refresh rates. Advanced driver IC designs using low-power process technologies, efficient circuit topologies, and intelligent power management reduce driver contribution to total power. Adaptive refresh rate control reduces power when high refresh rates are unnecessary.

The rendering pipeline that generates display content often consumes more power than the display itself. Foveated rendering dramatically reduces GPU workload by rendering peripheral regions at reduced resolution. Asynchronous timewarp and similar techniques reduce the latency requirements on full-frame rendering, potentially enabling power-saving GPU operating modes during portions of each frame interval.

Heat Sources and Paths

Display backlights or emissive elements convert electrical power to light with efficiencies typically ranging from 5% to 50%, with the remainder becoming heat. Display driver ICs dissipate power proportional to switching activity and output current. Processing electronics for rendering and system control generate substantial heat, particularly during demanding applications.

Heat must be conducted away from sensitive components and ultimately rejected to the environment. Thermal interface materials, heat spreaders, and heat pipes transfer heat from concentrated sources to larger dissipation areas. Passive cooling through natural convection and radiation is preferred for silent operation, but active cooling with miniature fans may be necessary for high-power systems.

Thermal Management Strategies

Thermal design integrates with mechanical and optical design to create effective heat paths without compromising other functions. Metal structural elements can serve dual purposes as heat spreaders. Placement of heat-generating components considers proximity to the user's face to avoid discomfort, proximity to temperature-sensitive optical elements, and access to thermal dissipation surfaces.

Active thermal management adjusts system operation based on measured temperatures. Throttling display brightness, reducing refresh rate, or limiting processing performance prevents overheating when thermal limits approach. Predictive algorithms can anticipate thermal buildup based on workload patterns, enabling preemptive adjustments that minimize perceptible performance impact.

User Comfort Considerations

Components in contact with or adjacent to the user's face must remain at comfortable temperatures, typically below 40 degrees Celsius for extended contact. Insulating layers between heat-generating components and user-facing surfaces reduce perceived warmth. Directing heat dissipation away from the face, such as toward the top or back of a headset, improves comfort even with significant total heat generation.

Ventilation design balances thermal performance with other requirements including dust intrusion, acoustic considerations, and aesthetic appearance. Breathable fabrics and foam materials in user-contact areas can improve comfort by allowing some airflow while maintaining cushioning and light-blocking functions.

Optical-Mechanical Integration

Optical elements must be positioned with precision measured in micrometers and angular accuracy measured in arc-minutes. Mechanical structures must maintain this alignment across temperature variations, mechanical impacts, and long-term use. Materials selection considers thermal expansion coefficients, stiffness, weight, and compatibility with optical coatings and bonding adhesives.

Manufacturing tolerances accumulate through the assembly process, potentially compromising optical performance. Tolerance analysis guides allocation of requirements across components, identification of sensitive dimensions, and design of adjustment mechanisms where needed. Active alignment during assembly enables correction of accumulated errors but adds process complexity and cost.

Electrical Integration

High-speed signals between processors, display drivers, and displays require careful signal integrity management. Impedance-controlled interconnects, appropriate termination, and attention to crosstalk and electromagnetic interference ensure reliable signal transmission. Power distribution must provide clean, stable supply voltages to sensitive analog circuits while efficiently converting from battery voltage.

Flexible printed circuits often connect components that must move relative to each other, such as hinged displays or adjustable optics. These circuits must survive repeated flexing, maintain signal integrity, and fit within tight mechanical envelopes. Cable routing integrates with thermal design to avoid blocking heat paths while protecting cables from damage.

Calibration and Quality Control

System-level calibration captures the actual characteristics of assembled units, enabling software compensation for component variations. Calibration data for distortion, color, brightness uniformity, and other parameters is stored in device memory and applied during operation. The calibration process must be efficient enough for production volumes while thorough enough to ensure quality.

Quality control testing verifies that assembled systems meet specifications across all performance parameters. Automated optical measurement systems assess image quality, field of view, distortion, color accuracy, and other optical metrics. Functional testing verifies electrical operation, sensor function, and software behavior. Reliability testing validates performance over simulated lifetime use cycles.