As electronic paper (ePaper) technology continues to evolve, manufacturers are no longer focusing only on display resolution or refresh speed. Increasingly, the industry is paying attention to reading comfort and how closely an electronic display can replicate the experience of reading traditional paper. This demand has led to the development of the Paper Similarity Index (PSI), an important certification system designed specifically for paper-like displays.
Today, ePaper devices are widely used in eReaders, eNotes, education tablets, office devices, and smart displays. Since many users spend long hours reading on these screens, visual comfort has become a key factor in evaluating display quality. PSI certification was introduced to provide a scientific and standardized method for measuring the paper-like viewing experience of ePaper displays.
What Is the Paper Similarity Index (PSI)?
The Paper Similarity Index (PSI) is a display evaluation and certification system developed to measure how closely an electronic display resembles real paper in terms of readability and visual comfort.
In 2020, E Ink began collaborating with TÜV Rheinland to establish a professional assessment system for paper-like electronic displays. In 2021, the PSI certification system was officially launched.
Unlike traditional display certifications that mainly focus on brightness or color performance, PSI emphasizes the natural reading experience. The system evaluates whether a display can provide comfortable long-term viewing with minimal eye strain while maintaining the visual characteristics of printed paper.
The PSI score ranges from 0 to 100, with traditional paper defined as the benchmark score of 100. A higher PSI score indicates a display that more closely resembles real paper.
Why Is PSI Certification Important?
Modern users increasingly rely on digital devices for reading, studying, note-taking, and office work. However, conventional LCD and OLED screens often produce eye fatigue due to backlighting, glare, and excessive blue light exposure.
PSI certification helps users identify displays that provide a more comfortable and paper-like reading experience. For manufacturers, PSI certification also serves as an important indicator of display quality and user-centered design.
The certification is especially valuable for:
- eReaders
- eNotes
- Digital learning devices
- Office productivity tablets
- Long-term reading applications
As electronic paper technology expands into education and professional environments, paper-like visual performance has become a major competitive advantage.
How Is PSI Evaluated?
The PSI system evaluates multiple aspects of display performance related to reading comfort and visual similarity to paper.
Key Evaluation Factors Include:
- Ambient light adaptability
- Contrast consistency
- Reflection control
- Eye comfort performance
- Viewing angle consistency
- Color and brightness uniformity
- Ghosting effects
- Refresh performance
- Grayscale characteristics
These testing categories help determine whether a display can maintain stable readability under different environments and long-term usage conditions.
Unlike traditional display testing that focuses heavily on vivid color output or maximum brightness, PSI evaluation prioritizes natural readability and visual stability.
PSI Certification and ePaper Technology
Electronic paper displays are particularly well suited for PSI certification because of their reflective display structure. Unlike LCD displays that rely on continuous backlighting, ePaper displays reflect ambient light similarly to traditional paper, resulting in reduced glare and lower eye fatigue.
Modern color ePaper technologies such as E Ink Kaleido™ have demonstrated strong PSI performance. In October 2021, TÜV Rheinland awarded the first PSI certification to E Ink Kaleido™ Plus color ePaper modules, achieving a PSI score of 86.
In 2024, devices using the latest Kaleido 3 technology, including products such as the Tab10C Pro, also received PSI certification with similarly high scores.
These results demonstrate the continuous improvement of color ePaper technology in reading comfort and visual quality.
The Future of Paper-Like Display Certification
As consumers increasingly prioritize eye comfort and long-duration usability, paper-like display certification is expected to become more important across the display industry.
Future PSI evaluation systems may further expand into areas such as:
- Flexible ePaper displays
- Full-color ePaper
- Educational devices
- Medical reading equipment
- Low-blue-light smart displays
At the same time, PSI certification may become an important purchasing reference for users selecting eReaders, digital notebooks, and productivity devices.
Conclusion
The Paper Similarity Index (PSI) represents an important advancement in the evaluation of electronic paper displays. Rather than focusing only on traditional display specifications, PSI measures how effectively a screen replicates the comfortable and natural reading experience of real paper.
As ePaper technology continues developing toward higher color performance, faster refresh rates, and wider commercial adoption, PSI certification will likely play an increasingly important role in defining display quality and reading comfort standards for the next generation of digital devices.
SEEKINK is at the forefront of leveraging e-ink technology in our digital signage solutions. We continue to push the boundaries of visual displays, creating e-ink solutions that not only meet the demands of today’s businesses but also contribute to a more sustainable and efficient future.
