Biometric Authentication Technology refers to a technology that uses relevant features of the human body to authenticate identity or control permissions. Facial recognition technology, also known as Face ID, has attracted widespread attention since its first use on mobile phones in 2016.

The principle of facial recognition technology is to use an infrared laser dot matrix projector near the front camera area of a mobile phone to emit infrared laser with a certain divergence angle to model the face, and then use an infrared sensor to recognize the already modeled face to achieve recognition function.

Face ID is generally divided into structured light and ToF. There is a certain difference between the two methods. In structured light technology, the infrared laser dot matrix projector is used to emit nearly 30000 infrared laser spots and transmit them onto the face. The infrared sensor detects the position and intensity of the 30000 laser dots to obtain the 3D features of the face, and matches them with the user's 3D face model in the mobile phone database to achieve identity authentication. This method is commonly referred to as the principle of structured light.

Laser emitter (VCSEL)

Undoubtedly, the infrared laser dot matrix projector is one of the core components in facial recognition systems. The main principle is to use a vertical cavity laser emitter (VCSEL) to emit infrared laser, which is then projected into corresponding light spots through an imaging optical system and a diffractive optical element (DOE). However, due to errors in the design and processing of the entire optical system, the energy and position of the laser lattice may deviate, which can affect the detection of light spots and further facial recognition algorithms.

Therefore, detecting the spot distribution of infrared laser dots is crucial for facial recognition systems.

Lanfei optical laser integrating sphere

In addition, due to the physical characteristics of structured light principle, which means that facial recognition accuracy decreases with distance, mobile phone users need to trigger the facial recognition module at close range (less than tens of centimeters). At this distance, the impact of laser on the human eye needs to be carefully considered. Especially nowadays, the usage rate of mobile phones is quite high, and the energy of infrared lasers has a more important impact on the human eye during frequent use of mobile phones

Considering the above two issues, Lanfei Optics has developed a mobile facial recognition detection system based on 40 years of experience in optical system development. This system can achieve high-precision measurement of the total energy, individual spot energy and distribution, as well as the energy that can enter the human eye of the infrared laser dot matrix projector for mobile phones.

Mobile facial recognition detection system

The system emits Vcsel laser onto a diffuse transmission plate and takes photos using a calibrated camera for calculating human eye safety. At the same time, it also utilizes the relationship between angles to calculate functions such as divergence angle.

Internal structure diagram of mobile facial recognition detection system

In addition, by using the Lambertian optical properties of Lanfi and the highly uniform transmission film material Spectralon to make standard diffuse transmission targets, the spatial non-uniformity caused by laser spots at different angles can be eliminated, ensuring the accuracy of the measurement system in principle.

High uniformity transmission film material Spectralon

Finally, through a software system specifically developed for laser dot arrays, the detector can be corrected to accurately detect the energy and position of each laser spot, and analyze the impact of laser on human eye safety. The results can be saved and output.

• Testing laser

• Spectralon transmission material, Lambertian, ultra-high spatial uniformity

• High precision recognition algorithm

• Accurate and fast data collection

• Visual interface, dynamically displaying measurement results

• Can provide software development interfaces

Spectralon transmission film transmittance: 25% or 50%

Spectralon transmission film size: 30cm * 50cm or customized

Spectralon spectral flatness:+/-1.5%

Eye safety: 7mmc testing method

Distance between DUT and diffuse reflector: 5cm to 30cm

Wavelength range: 400nm to 1000nm

DUT divergence angle: 80 ° customizable to 120 °

Software Settings

Spot analysis: Spot position/intensity analysis/maximum light intensity analysis

Data output format:. txt/. csv