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IEC TR 63145-1-1: Eyewear Display Terminology — Building a Common Language for Wearable Displays
IEC TR 63145-1-1:2020 — Eyewear Display — Part 1-1: Generic Terminology
1. The Need for Standardized Eyewear Display Terminology
The rapid proliferation of augmented reality (AR), virtual reality (VR), and mixed reality (MR) devices has created a pressing need for standardized terminology to describe the performance and characteristics of eyewear displays. IEC TR 63145-1-1 addresses this need by establishing a comprehensive vocabulary and set of definitions for eyewear display technologies, covering optical parameters, image quality metrics, ergonomic considerations, and measurement methodologies.
Eyewear displays, also commonly referred to as head-mounted displays (HMDs), smart glasses, or near-eye displays, present unique measurement and characterization challenges compared to conventional flat-panel displays. The optical path involves multiple elements including waveguides, combiners, micro-displays, and projection optics, all of which must be precisely aligned and calibrated to deliver a satisfactory user experience. Without standardized terminology, comparing products from different manufacturers or evaluating technical improvements across generations becomes unreliable.
| Term | Abbreviation | Definition per IEC TR 63145-1-1 | Typical Measurement Unit |
|---|---|---|---|
| Field of View | FOV | Angular extent of the visible display content as seen by the user’s eye | Degrees (°) |
| Eye Relief | ER | Distance from the last optical surface to the user’s corneal apex | Millimeters (mm) |
| Exit Pupil | EP | Diameter of the beam of light exiting the eyepiece optics | Millimeters (mm) |
| Virtual Image Distance | VID | Apparent distance from the eye to the virtual image plane | Meters (m) or Diopters (D) |
| Luminance Uniformity | LU | Ratio of minimum to maximum luminance across the field of view | Percentage (%) |
| Modulation Transfer Function | MTF | Measure of optical system contrast preservation at a given spatial frequency | Line pairs per degree (lp/°) |
One of the most frequently misunderstood parameters in eyewear displays is the virtual image distance (VID). A VID of 2–3 m is generally recommended for AR applications to match typical indoor viewing distances, while VR applications often use a VID of 1–2 m. An excessively short VID (<0.5 m) can cause accommodative-convergence conflict, leading to user fatigue and discomfort.
The scope of IEC TR 63145-1-1 extends beyond mere definitions. It provides a structured taxonomy that categorizes eyewear display parameters into optical, electro-optical, image quality, and ergonomic groups. This classification system enables engineers and researchers to systematically evaluate display performance and identify the root causes of visual quality degradation in prototype and production systems.
2. Key Optical Parameters and Measurement Methods
The standard defines a comprehensive set of optical parameters that characterize the performance of eyewear displays. Field of View (FOV) is one of the most important and most frequently cited specifications, yet its measurement can vary significantly depending on the methodology used. IEC TR 63145-1-1 specifies that FOV should be measured as the diagonal angular extent at the design eye position, with the display showing a full-white test pattern at maximum luminance. Both monocular and binocular FOV are defined, along with the overlap region which is critical for stereoscopic depth perception.
Resolution in eyewear displays is measured in terms of angular resolution (arc minutes per pixel or line pairs per degree) rather than the raw pixel count of the micro-display. This is because the same micro-display can produce very different angular resolutions depending on the optical magnification employed. The standard specifies measurement procedures using USAF 1951 resolution test charts or equivalent patterns, imaged through the complete optical system including the eyepiece and any waveguide combiner.
For waveguide-based AR displays, the standard introduces the concept of “eyebox” — the volume of space within which the user can move their eye while maintaining a complete view of the displayed image. A larger eyebox (typically >10 mm × 8 mm) significantly improves usability by accommodating different interpupillary distances (IPD) and allowing some spectacle clearance. The standard defines methods for measuring eyebox dimensions using a robotically controlled photodetector scanned across the exit pupil plane.
Luminance and contrast measurements for eyewear displays require specialized equipment and procedures due to the proximity of the display to the eye. The standard specifies the use of an imaging photometer or a spot photometer with a custom-designed artificial eye that replicates the optical characteristics of the human eye, including the pupil diameter (typically 4 mm for photopic conditions) and the spectral response of the human visual system. Colorimetry follows the CIE 1931 standard colorimetric system, with measurements reported in the sRGB or DCI-P3 color space as appropriate for the application.
Latency, or motion-to-photon delay, is a critical parameter for AR/VR applications where head movements must be tracked and rendered with minimal delay to prevent simulator sickness. IEC TR 63145-1-1 defines latency as the time difference between a change in the input (e.g., head rotation) and the corresponding change in the displayed image, measured using a high-speed photodetector and an inertial measurement unit (IMU) synchronized with sub-millisecond precision.
3. Engineering Design and Testing Insights
Implementing the measurement and characterization framework defined in IEC TR 63145-1-1 requires careful attention to test setup, environmental conditions, and statistical analysis. The standard emphasizes that all optical measurements should be performed in a darkroom environment (ambient illuminance < 1 lux) after a warm-up period of at least 30 minutes to allow the display and measurement instruments to reach thermal equilibrium.
One of the most challenging aspects of eyewear display testing is the alignment between the display under test and the measurement instrument. The standard specifies a six-degree-of-freedom alignment procedure using precision translation and rotation stages, with the display positioned at the design eye point. For binocular displays, the interpupillary distance (IPD) adjustment mechanism must be set to the nominal value used in the product specification, typically 63.5 mm representing the population average.
Environmental robustness testing is essential for eyewear displays intended for outdoor or industrial use. The standard recommends testing at temperatures from -10°C to +50°C and humidity levels up to 95% RH. Optical adhesives used in waveguide combiners are particularly susceptible to delamination under thermal cycling, and the standard specifies accelerated aging tests (1000 cycles from -20°C to +60°C) to validate long-term reliability.
For see-through AR displays, the standard introduces specific metrics that are not applicable to immersive VR displays. These include see-through luminance (the perceived brightness of the real-world scene through the display), see-through color shift (change in chromaticity coordinates when viewing through the combiner), and occlusion capability (the ability to render virtual objects that optically block real-world objects behind them). Occlusion is particularly challenging and remains an active area of research; current waveguide-based combiners typically achieve only partial occlusion.
The standard also addresses subjective evaluation methods through defined visual comfort scales and task performance metrics. While objective measurements form the foundation of display characterization, the ultimate assessment of an eyewear display depends on human visual perception. The standard provides structured questionnaires (such as the Simulator Sickness Questionnaire SSQ and the NASA Task Load Index NASA-TLX) that should be administered as part of a comprehensive display evaluation protocol.
When developing a production test plan for eyewear displays, prioritize the measurement of parameters that have the greatest impact on user experience: MTF at the center of the field (correlates strongly with perceived sharpness), luminance uniformity (affects comfort during prolonged use), and latency (directly causes or prevents simulator sickness). These three parameters account for approximately 70% of the variance in user satisfaction scores based on published studies referenced in the standard.
4. Frequently Asked Questions
Q1: How does IEC TR 63145-1-1 relate to other IEC display standards such as IEC 62341 (OLED) and IEC 61747 (LCD)?
A: IEC TR 63145-1-1 is complementary to these existing display standards. Wherever possible, the eyewear display standard references the measurement methods and terminology established in the flat-panel display standards, adapting them as needed for the unique optical configuration of near-eye displays. For example, luminance measurement follows the same fundamental principles as IEC 62341-6 but specifies an artificial eye optical system to account for the proximity of the display to the viewer.
A: IEC TR 63145-1-1 is complementary to these existing display standards. Wherever possible, the eyewear display standard references the measurement methods and terminology established in the flat-panel display standards, adapting them as needed for the unique optical configuration of near-eye displays. For example, luminance measurement follows the same fundamental principles as IEC 62341-6 but specifies an artificial eye optical system to account for the proximity of the display to the viewer.
Q2: Is compliance with IEC TR 63145-1-1 mandatory for selling eyewear displays in international markets?
A: As a Technical Report (TR), this document is informative rather than normative. However, many national regulatory bodies and major procurement organizations (such as defense agencies and healthcare providers) are adopting these definitions and measurement methods as contractual requirements. Manufacturers who align their datasheets with IEC TR 63145-1-1 terminology benefit from clearer customer communication and reduced commercial disputes.
A: As a Technical Report (TR), this document is informative rather than normative. However, many national regulatory bodies and major procurement organizations (such as defense agencies and healthcare providers) are adopting these definitions and measurement methods as contractual requirements. Manufacturers who align their datasheets with IEC TR 63145-1-1 terminology benefit from clearer customer communication and reduced commercial disputes.
Q3: What is the recommended measurement distance for determining resolution and MTF in eyewear displays?
A: The standard recommends measuring at the design eye position with the virtual image distance set to the manufacturer’s specified value. The measurement instrument (typically a CCD camera with a microscope objective) should be focused on the virtual image plane, not on the physical micro-display surface. This is a critical distinction: focusing on the micro-display would measure the native resolution of the display panel, not the system-level resolution experienced by the user.
A: The standard recommends measuring at the design eye position with the virtual image distance set to the manufacturer’s specified value. The measurement instrument (typically a CCD camera with a microscope objective) should be focused on the virtual image plane, not on the physical micro-display surface. This is a critical distinction: focusing on the micro-display would measure the native resolution of the display panel, not the system-level resolution experienced by the user.
Q4: How does the standard address emerging technologies such as holographic and light-field displays?
A: IEC TR 63145-1-1 establishes a terminology framework that can be extended to emerging display technologies. The generic definitions for parameters such as FOV, eye relief, and exit pupil apply to all near-eye display types. For technology-specific parameters (such as holographic display’s viewing angle or light-field display’s depth resolution), the standard provides a methodology for defining new terms while maintaining consistency with the existing terminology structure. A future part of the 63145 series is expected to address holographic displays specifically.
A: IEC TR 63145-1-1 establishes a terminology framework that can be extended to emerging display technologies. The generic definitions for parameters such as FOV, eye relief, and exit pupil apply to all near-eye display types. For technology-specific parameters (such as holographic display’s viewing angle or light-field display’s depth resolution), the standard provides a methodology for defining new terms while maintaining consistency with the existing terminology structure. A future part of the 63145 series is expected to address holographic displays specifically.
