Technical requirements for camera lighting in palm vein recognition

Near-infrared light source: Palm vein recognition mainly relies on near-infrared light becauseoxygenated hemoglobin in veins has a strong absorption of near-infrared light. Under the illumination of near-infrared light, the vein area appears dark, forming clear contrast with the surrounding tissue, thus clearly displaying the palm vein pattern. Common near-infrared light sources include near-infrared light-emitting diodes (LEDs which have the advantages of low power consumption, long life, and fast response speed, and can stably provide the required light source for palm vein image acquisition. For, in common palm vein recognition access control devices, near-infrared LED light sources are widely used to ensure effective acquisition of palm vein images in various environments.

Invisible characteristics: To protect user privacy and enhance security, the light source for palm vein recognition should have invisible light characteristics. Near-infrared light is in the spectrum range that invisible to the human eye, avoiding interference with the user's vision and also reducing the risk of palm vein features being observed and stolen by the naked eye. In the vein recognition identity verification system of financial institutions, the invisible near-infrared light source can not only ensure the accuracy of user identity verification but also effectively protect user information security.

Stable and moderate intensity: The light intensity needs to be stable and moderate. Too strong light may lead to overexposure of the image, causing loss of details in the palm vein pattern; while too weak light will increase the noise of the image and reduce the clarity, affecting the extraction and recognition of palm features. Generally speaking, the light intensity of palm vein recognition devices should be controlled within a certain range to ensure that the acquired palm vein images have uniform brightness and clear. For example, in palm vein attendance devices in indoor office environments, the light intensity needs to be reasonably adjusted according to the indoor natural light and the placement position of device to ensure that the palm vein images of employees can be accurately acquired at different times.

Automatic adjustment function: To adapt to different usage environments and differences in users', the camera light should have the function of automatically adjusting the light intensity. Through the built-in light sensor, the ambient light intensity is detected in real time, and light source output is automatically adjusted to ensure that high-quality palm vein images can be obtained whether in strong sunlight outdoors or in dim light indoors. In outdoor palm vein recognition devices, the function of automatically adjusting the light intensity can make the device work normally both in the daytime and at night, without being affected by changes in light.

Uniform illumination of the palm area: The camera light needs to evenly illuminate the entire palm area to avoid local over-brightness or over-darkness, ensuring that contrast and clarity of each part of the palm vein image are consistent. By using special optical design and diffuse reflection materials, near-infrared light can be evenly distributed the palm surface. For example, in some high-end palm vein recognition devices, a ring-shaped light source and a diffuse reflection plate are used in combination to achieve uniform of the entire palm, providing a guarantee for accurately extracting palm vein features.

Avoiding shadow generation: Uniform lighting can effectively avoid shadows on the palm surface, as shadows can interfere with the recognition of palm vein patterns, leading to feature extraction. When designing the lighting system for palm vein recognition devices, it is necessary to fully consider the angle and distribution of the light source to ensure that the light illuminates the palm from multiple directions, eliminating the impact of shadows. In the context of security surveillance, avoiding shadow generation can improve the accuracy of palm vein recognition and the occurrence of false positives.

Fast lighting and extinguishing: When a user performs palm vein recognition, the camera light needs be able to turn on quickly, reaching a stable illumination state in a short period of time (usually within 0.1 seconds), to capture the palm vein image time and improve recognition efficiency. After recognition is completed, the light should be able to turn off quickly to save energy and reduce interference to the user. In the palm recognition equipment of the airport's fast security check channel, the fast response light can ensure that passengers quickly pass through the security check and reduce waiting time.

Synchronization camera capture: The response speed of the light should be synchronized with the camera's image capture speed to ensure that the light is in the best state when the camera captures image, obtaining a clear palm vein image. Through precise circuit design and control algorithms, the synchronous operation of the light and the camera is achieved, avoiding image blurring uneven illumination caused by asynchronization. In the intelligent attendance system, the synchronization of the light and the camera can ensure that employees complete palm vein recognition quickly and accurately whening in.

Long life: Palm vein recognition devices may work continuously for a long time, so the life of the camera light is crucial., the life of the near-infrared light source is required to reach tens of thousands of hours or more, reducing the frequency of replacing the light source and the cost equipment maintenance. In places with high requirements for equipment stability, such as banks, long-life light sources can ensure the long-term stable operation of the palm vein recognition system ensure the normal operation of the business.

High stability: The light should maintain stable performance during long-term use, including light intensity, spectral characteristics, etc., to avoid degradation due to light source aging or other factors, which affects the accuracy of palm vein recognition. By using high-quality light sources and stable drive circuits, it is ensured the light can work stably under different environmental conditions. In palm vein recognition devices in industrial environments, highly stable lights can adapt to complex working conditions and ensure the operation of the equipment.

Matching with the camera: The optical characteristics of the light, such as the emission angle and spot size should match the field of view and imaging range of the camera to ensure that the camera can fully and clearly capture the palm vein image of the illuminated palm area. When the palm vein recognition system, the parameters of the camera and the light should be considered comprehensively to optimize the matching and improve the system performance. In the design of palm vein recognition access control all-in-one machine, ensuring the matching of the light and the camera can improve the recognition accuracy and stability of the access control system.

Support the recognition algorithm: The lighting effect of the light should meet the requirements of the palm vein recognition algorithm for image quality, providing the algorithm with clear and accurate palm vein data. For example, for algorithms that rely on the extraction of specific image features, the light needs to ensure the clarity and contrast of the palm vein patterns, making easy for the algorithm to accurately identify the features. When developing palm vein recognition algorithms, it is necessary to optimize them based on the actual lighting effect of the light to the adaptability and accuracy of the algorithm under different lighting conditions.