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Immersing users in the metaverse requires a combination of physical AR / VR hardware and software content to create a sense of genuine commitment to the simulated world. With years of vision study at PixArt, optical finger navigation (OFN) has evolved into wearable technology to allow users to interact well with AR / VR devices in the virtual world.

OFN technology was widely used as an optical trackpad in mobile phones before the era of touchscreen smartphones. The ease of use of OFN makes users quickly adapt to its friendly interaction with the HMI Management Gadget. Let’s see how it works!

Figure 1. OFN optical system

Figure 2. OFN system blocks

The OFN optical system consists of 4 main functional units: OFN chip, optical lens, infrared (IR) LED and sensor cover. The sensor cover and FPC can be customized based on the external identifier of the final product. IR LED illuminates the fingertip through the set of optical lenses. The OFN chip optically acquires consistent fingertip images and mathematically determines the direction and magnitude of finger movements. The OFN chip is a system on a chip (SoC) that contains an image acquisition system, a digital signal processor (DSP) and an I2C serial port interface. Microscopic fingerprint surface images are obtained and processed internally to display motion data in Δx and Δy relative displacement and directions, as well as touch detection, one-click and double-click. The OFN chip calculates all image processing and motion interpretation in a chip without an external data processing MCU, thus allowing OFN technology to be a truly low-power wireless HID solution.

Figure 3. OFN output data

To fit well as a touch element in wearables, PixArt further transforms OFN technology to meet the critical aspects of wearables with low form factor, low power consumption, high performance and ease of integration. The newly introduced PAW3008 is an OFN solution that unlocks the intuitive human-machine interaction that controls the metaverse.

Key features of the PAW3008 solution
Work temperature -20 to + 60 ° C
Operating voltage VDDM: 2.5V ~ 3.6V


Current consumption Operating mode: 2.5 mA

Sleep1 / Sleep2: 50/25 µA

Standby shutdown: 15 µA

Interface I2° C
High speed motion detection up to 24 IPS (inches per second)
Selectable resolution up to 3200 CPI (counts per inch)
Data output

Motion data: Δx and Δy displacement

Directions for movement

Touch Detection

Click detection: single and double click click

Universal break pins To display traffic, directions, tap and click
Chip package type CSP with 9 balls
Chip package size 1,526 x 1,656 x 0.554 mm3
Chip and lens mounting

Dimensions (L x W x H)

3.6 x 2.5 x 1.5 mm3 (excluding sensor cover and FPC)

Figure 4. The new PAW3008 OFN chip and lens

(1) Superb small in size

The newly introduced miniature OFN solution, PAW3008 from PixArt, is available in a superb small size with a chip and lens size of 3.6 (L) x 2.5 (W) x 1.5 (H) mm3. This little OFN solution can be embedded in thin and thin wearable designs such as smart rings, clothing, ribbons, etc.

Figure 5. Assembly of OFN chip, optical lens and IR LED

Figure 6. OFN in the PixArt Smart Ring demo guide

(2) Low energy consumption

Low power consumption is always the key factor in buying a wearable gadget. The PAW3008 chip can operate at a low current consumption of 2.5 mA when detecting finger movement and up to 25 μA in standby mode. For example, the low-power design of the OFN solution can make the smart ring withstand 7.5 hours of continuous use on a single charge of 21 mAH *.

* Based on the PixArt usage model of the Smart Ring Demo Reference, as shown in Figure 6. For detailed information, please contact us directly.

(3) High productivity

In order for an AR / VR gadget to be widespread, a good user experience is vital to the perception of the human-to-machine connection in the virtual world. The PAW3008 OFN solution is well-chosen for detecting slight finger movements through AR / VR wearable accessories to control software content. The most impressive OFN technology is the recognition of small and real finger gestures. The natural pinching of the fingertip through the small window area of ​​the touch cover can be translated exactly as index finger movements with scalable sensitivity and resolution from 50 to 3200 inches (CPI) to move smoothly in 3D virtual space. The OFN solution can detect high-speed movement up to 24 inches per second (IPS). Even swiping with your finger is not a puzzle for OFN.

Figure 7. Illustration of the OFN Smart Ring application

(4) Easy integration

PixArt always puts reliability and ease of integration as the main considerations in product design. A complete OFN optical system can be assembled by integrating the OFN chip, optical lens and sensor cover into the FPC. Since there is no mechanical moving part and does not require any precise optical alignment, the optical lens holder clicks directly on the OFN chip package and IR LED to form a functional optical system. A touch coating is added to the final product as a protective coating to increase the durability and purpose of the exterior design style.

Figure 8. OFN module

Many HMI products that involve finger movement can use OFN technology to maneuver navigation control. OFN can be found in many witches entering people’s daily lives. Initially it started as a trackpad in mobile phones, then it is used in the remote control, presenter, manual pointing devices, etc. When Smart Gadgets became popular, OFN appeared as a touch element in Smart Wearables as an AR / VR accessory to expand its great use to give a sense of real commitment to controlling computer-generated cyberspace. The new miniature OFN solution PAW3008 is perfect in its small size to fit in the thin, thin and compact enclosed space of Smart Wearables.

PixArt not only delivers the OFN solution in a discrete IC package with its corresponding optical lens and standard modular package, but also customizes the chip and module. To fit into niche applications for automotive, medical, industrial, etc. market segments, PixArt can customize the OFN solution with a variety of module designs, including touch cover designs. To evaluate the OFN solution, comprehensive support tools are available by contacting PixArt to request samples, an evaluation kit and a design kit.

For more information, please contact your local PixArt sales or contact us at https://www.pixart.com.


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