Display Color Properties

Displays of all kinds are the main channels for human interaction with various devices. Whether it is a mobile phone, tablet, PC, cars, home appliances, info screens, or machine controllers, displaying information and content on display is the most natural way to interact with people. As the variety and usage of displays increase, the color optics of display performance grows in importance. Can the user see the content clearly from various angles? Are the colors vivid and natural at the same time? Are there unevenness or visible defects on display? Do the colors of two in-device displays match when it comes to dual-screen devices?

Humans are gifted with five senses namely sight, hear, touch, taste and smell. These senses help us perceive the world and get the best of the experiences. Technology has certainly adapted to give us best experience by the means of touch. From phone to a watch, from car to fridge, from ATMs to POS, everything is embedded with a touch capacity for human interaction. Delivering such interactive technology comes with a requirement of quality assurance to keep the product consistent and enhance the customer experience. Having shipped a poor quality of touch panels in any device has a significant impact on the quality of device. This certainly affects the device brand and the future of the product. Having a thorough testing cycle in R&D as well in manufacturing line, improves the quality of production, which helps getting better business yield.

Consumer VR headsets have been available since 2015, when a large number of companies announced their own versions of the products. By 2016, more than 230 companies were working on their own VR HMD projects. Most of these projects have since ended and companies have gone bankrupt, but some keep releasing new products, both stand-alone and tethered versions, on an almost annual basis. Oculus (Facebook) released new Quest and Rift devices in 2019, while HTC came up with a new VIVE and Valve announced their Index glasses. Then there is Varjo, a company that keeps amazing their fans with human-eye resolution products, as well as numerous new Chinese companies that are also catching up fast in product design and performance. In CES 2020, there were dozens of new players and products coming to both the VR and AR markets. ^{[1] [2]}

The testing process during R&D of a new smart device involves many aspects. In this blog I will showcase some of the most important areas where we are the best in the world.

When it comes to the development of physical mass products, we work with most of the top-rated companies in the world. Why? Our competence in testing and our ability to help the customer in the early stages of new product innovation makes us unique. The competence of our metrology teams, especially our optical and imaging-related knowledge, combined with extensive knowledge of high-precision robotics, is unique in the world. An example of our competence in component testing is described in the blog Characterizing Diffractive Waveguides. Add an exceptional team and the ability to help customers to solve their problems and that is what OptoFidelity stands for.

We work with our customers as well as further down the line during manufacturing and after sales. For further information please have a look at further details at the Production Testing blog posting or, for tailored solutions, at the OptoFidelity Competencies site.

Production is the key process in bringing the end user products into the market. For our customers, this involves production technology validation, traveling to the factories, meeting tight line ramp-up deadlines and ensuring that production costs are within the business case for the product. In a later phase, the focus moves into production line efficiency improvements and maintaining the systems. Equipment vendor capabilities and level of experience has significant influence on the level of required effort. This blog is outlining our experience for how to create successful projects, a checklist for the key ingredients.

Saying "Well planned is half done" makes perfect sense in measurement automation. In fact, the key for successful projects is to understand production automation targets, measurement, interfaces and delivery logistics. When setting up the project, this understanding provides a solid starting point for the project.

In general, production automation aims at generating value as improved compliance, cost level, quality of results, yield and overall efficiency:

• Compliance: the key target of production measurement and calibration is to ensure that the manufactured units meet the product specifications, i.e. the product quality.
• Cost level: automation provides tools for improving the line throughput and reducing the labor costs. Typically performance metrics are units per hour (UPH), resource level and CAPEX costs.
• Quality of results: automation provides both enhanced accuracy and repeatability when compared to a manual or a semi-automated process, measured by Gage Repeatability & Reproducibility (GRR) metrics or similar.
• Yield: test automation provides the data for the yield improvement (percentage of non-defective items of all produced items).
• Overall efficiency is a combination of the above mentioned items, measured typically with Statistical Process Control (SPC) for continuous monitoring and development.

Successful projects have typically well-defined targets for the automation. The production automation targets provide priorities which have a big impact on the technological choices used in the station design. This target setting also enables possibly needed priority discussion already at the concept design phase to find the correct balance e.g., between UPH, measurement accuracy and cost. Having these discussions and setting achievable targets is important - no surprises should occur in the later phase of the project.

Measurement definition provides the purpose for the test system. This is typically defined in the form of a test list. A test list is created to establish understanding about the relevant phenomenon to be measured, the necessary measurement data for the test result (e.g., to define pass/fail thresholds) and a necessary level of test configurability. The test list is examined hand-in-hand with the production automation targets and performance targets such as the measurement accuracy, resolution and repeatability requirements. Measurement definition makes it possible to create a system concept:

• To find and select the best-suited measurement method and sequence, the key operating principle for the measurement.
• To screen and select the measurement instruments (e.g., camera, optics, illumination, and other sensors)
• To define the actuators providing the required performance (e.g., motion accuracy)
• To develop mechatronics 3D illustration about the system (including moving axis, measurement sequence)
• To create concept description including functions of sub-modules and their interaction as a complete system

Interfaces define how the test system is operated and what the sequence of actions in each interface is – for a production line station the interfaces include:

• Operator interface – how the operator interacts with the system, including system safety
• Physical interfaces – including cabinet size and shape as well as electrical, pneumatics and data interfaces
• Material handling - the way to move and physically interact with the device under test (DUT)
• DUT communication - identify and interact with the DUT software or firmware
• Measurement instruments and actuators – the equipment for control, actuation, sensing and data acquisition
• Data analysis – analyzing the raw data to produce the measurement results
• Reporting – providing the measurement results for the host system, e.g., factory data management or manufacturing execution system (MES)
• Configuration – toolset for setting up the system, making calibrations and configuring the test list, pass/fail criteria and system parameters
• Test sequence – the procedure to carry out the measurement sequence using all the interfaces

Well-defined and designed interfaces enable validation of system parts and the system as a whole. Having a well-thought-out sequence of actions is important for system reliability. Parallelism enables improved UPH e.g., by completing the analysis of previous DUT in parallel with measuring the next DUT. System level design is an area where the experience is very valuable; this enables performance, innovative designs, maintenance and use of proven technology platforms.

The purpose of delivery logistics is to create the demand-supply network for the station which is suited for the needs of factory locations and processes. Work at the factories is typically split into three phases: pre-production, line ramp-up and sustaining-mode production. Defining the delivery logistics to meet the demands in each phase is important – making it possible to meet the schedules and produce good quality prototypes and products. Delivery logistics involves:

• Station manufacturing – parts lead times and availability, incoming quality check (IQC), assembly quality control, burn-in, testing and outgoing quality check (OQC), packing
• Shipping – lead time for shipping and customs, delivery term used, cost level of tariffs, factory incoming shipments procedures
• Pre-production builds – arrangements for tools, resourcing and access rights, on-site work for installing, setting up and calibrating the stations, developing the best fit test sequence and pass/fail thresholds, validating the station accuracy and repeatability
• Production ramp-up – similar to pre-production but without development, focus on GRR for the stations to ensure station to station variations are within limits
• Sustaining production – OSS including on-site and off-site support, station performance monitoring and improvements, spare parts, repairs, maintenance and periodical calibrations

Work at the factory is fast-paced. This is the point where everything comes together – including the product hardware and software and the stations in the production line. Experience in the delivery logistics helps quite a bit in preparing, making things run smoothly and dealing with unexpected changes.

OptoFidelity can deliver turnkey production measurement and calibration systems – this statement is backed by 100+ different purpose-built systems that OptoFidelity has developed for volume production. Our systems are designed to fulfill the customer-specific measurement needs and used by world-leading manufacturers of smartphones, tablet computers, AR/VR devices, laptops, vehicle infotainment systems and industrial smart machinery.

Based on several years of experience, OptoFidelity has developed standard products and technology platforms to efficiently combine software, robotics, camera technologies and sensors to create demanding test systems. This gives a head start for the projects as the OptoFidelity platform frequently provides a large part of the needed overall implementation.

We at OptoFidelity are always trying to find ways to improve our working methods to support our customers’ needs – we have built our expertise and capabilities since 2005. Currently, OptoFidelity provides operations and service support for an installed base of 5,000+ pieces of measurement equipment in China, Vietnam, Taiwan and the USA. Our philosophy is to work close to our customers in both R&D and production, and we have design teams in the USA, Finland and China who are easy to work with. OptoFidelity provides delivery logistics with test equipment manufacturing in China and Europe. As a team, we have special expertise in mechatronics, optical metrology, signal processing and software as well as system design for production equipment. Together with special application expertise for measuring smartphone sensors, AR/VR technology, displays and touch UI, we can provide unique value for our customers.