On March 8th, it's been noted that as the number of vehicles supporting smart driving increases, so does the shipment of car-mounted laser radars. For vehicles utilizing fused perception solutions, laser radars are indispensable.
However, there are concerns about laser radars. After all, incidents have occurred where laser radars damaged cameras and surveillance CMOS. So, is there any potential harm to human eyes? Today, Huawei's "Intelligent Automotive Solutions" provided an extremely detailed analysis.
Lidar, short for Light Detection and Ranging, is a core sensor in smart driving systems. Its ability to reconstruct three-dimensional environments provides vehicles with rich and precise environmental information. Unlike cameras and millimeter-wave radar, Lidar actively emits light, making it unaffected by low-light conditions at night. This characteristic effectively supplements the limitations of cameras and radar, enhancing the safety and reliability of smart driving systems.
Is laser radar safe?
Let's start by looking at the definition of laser hazards in international standards.
The hazard level of lasers is divided into four classes: Class 1 lasers are considered harmless, Class 4 lasers are highly hazardous, while Class 2 and 3 lasers have low and moderate hazards respectively.
Vehicle-mounted laser radar belongs to Class 1 laser products. In other words, commercially available vehicle-mounted laser radar products must meet Class 1 standards. Their power and radiation intensity are far below the threshold that could cause harm to the human eye. Therefore, under normal operating conditions, vehicle-mounted laser radar does not pose a threat to human eyes.
Some might argue that having standards doesn't guarantee complete satisfaction. Huawei also interpreted the safety of lidar from a technical perspective, as follows:
Energy density: This looks at the "instantaneous irradiance of a single pulse" and the "average accumulated energy per unit area after prolonged exposure."
Firstly, the instantaneous energy of a single pulse can be ensured by strictly controlling the emission power of the lidar to limit it within the required threshold of standards.
Secondly, mainstream vehicle lidars on the market are scanning lidars. Taking a line scanning lidar as an example, it emits a laser beam covering a specific position with each emission. With the rotation of the mirror, the laser beam scans from left to right, covering a complete 120° field of view, as shown in the diagram below. This ensures that the lidar does not continuously "stare" and irradiate your eyes, and the accumulated energy per unit area remains within the specified threshold.
Let's take a look at the physiological structure of the human eye. The human eye mainly consists of the cornea, lens, and retina. When a laser beam enters the eye, different wavelengths exhibit slight differences.
Currently, mainstream automotive LiDAR systems on the market operate in the 905nm wavelength range of near-infrared light, with a few using 1550nm wavelength in the far-infrared range.
When a 905nm laser beam enters the eye, most of the energy is absorbed by the cornea and lens, with a small portion transmitted onto the retina. On the other hand, a 1550nm laser beam is almost entirely absorbed by the cornea and lens, with very little reaching the retina. Hence, there is an online claim that 1550nm LiDAR is safer than 905nm.
Actually, as long as the energy of the LiDAR is kept within the threshold acceptable to the human eye, it is safe, so there's no one safer than the other.
While it's true that 1550nm has a higher maximum safe power level in the human eye compared to 905nm, if the energy of a 1550nm laser exceeds regulatory limits, it can still damage the cornea and lens of the eye, just as a 905nm laser would harm the retina if its energy were exceeded.
If there are still doubts, let's look at the experimental results:
In the test setup below, the receiving aperture simulates the human eye's pupil. Under normal conditions, the pupil diameter ranges from 2.5 to 4mm and contracts when exposed to bright light. In a dark room, the pupil can dilate to 5 to 7mm. This test uses a 7mm aperture to simulate the maximum scenario of pupil dilation (i.e., maximum light transmission). The testing distance ranges from the most stringent 100mm to 1m, where the laser beam energy rapidly attenuates with increasing distance. 100mm is the shortest distance the human eye can focus, beyond which imaging on the retina is not possible.
Based on the rigorous testing scenarios outlined above, the efficiency of the laser beam entering the human eye is only about 1%. Moreover, the energy reaching the retina, after being heavily absorbed by the water in the eyeball, typically amounts to only around 20% of the eye damage threshold.
It's worth noting that the IEC 60825-1 standard also takes skin safety into account. Experimental calculations show that the energy from current laser radar systems only reaches about 1% of the safety threshold.
Therefore, vehicle-mounted laser radar products certified with Class 1 eye safety standards pose no harm to either the eyes or the skin.
