At the 2025 Shanghai Auto Show, Cadillac VISTIQ showcased a new LiDAR integration approach. The sensor is installed behind the front windshield, no longer protruding from the vehicle body as in traditional roof-mounted solutions. This setup utilizes Fuyao Smart Vision front windshield glass and features Hesai AT-series LiDAR.
For intelligent vehicles seeking to balance exterior design with sensor placement, this undoubtedly offers another option. However, changing the sensor's location brings new technical challenges. LiDAR needs to emit laser beams outward and receive signals reflected back from targets.
If there is an additional layer of glass in front, can light still pass through normally? After being hidden, can detection range and point cloud quality meet requirements?
01 Why Can't LiDAR Simply Be Hidden Inside the Body?
To understand the difficulties of hidden integration, one must first grasp how LiDAR works. Automotive LiDAR measures the distance between the target and the sensor by emitting laser beams and receiving light signals reflected back from targets. Combined with scanning direction information, the system constructs a three-dimensional point cloud of the surrounding environment, providing a basis for the vehicle to identify obstacles and estimate spatial positions. This means that LiDAR performance depends not only on its internal laser emission, reception, and scanning systems but also on the entire propagation process of light traveling from the sensor to the external environment and back.
If a piece of glass or body trim panel is added in front of the sensor, the optical signal may be affected. Absorption, surface reflection, and scattering of specific wavelengths by the material can all weaken the effective echo; additional reflections or stray light may also interfere with the receiving system.
Moreover, front windshields are generally curved and have a certain thickness. When lasers enter at an angle, refraction occurs, leading to deflection of scanning angles, field-of-view distortion, and point cloud angular errors. Different degrees of refraction at various incident angles make calibration and distortion compensation more complex. Automotive front windshields also need to accommodate functions such as thermal insulation.
Some products use infrared reflective coatings, but these designs do not fully align with the requirement for LiDAR to efficiently transmit infrared laser beams at specific wavelengths. Therefore, hidden LiDAR is not simply a matter of placing the sensor behind glass. The glass and sensor must be designed as an integrated unit, meeting automotive glass usage requirements while ensuring the LiDAR receives sufficient effective echoes.
02 What Changes Does the Front Windshield Need for LiDAR?
Since ordinary insulated glass may affect the signal, solving the problem cannot rely solely on increasing the LiDAR's own transmission power or receiver sensitivity; it also requires improving the optical performance of the glass at the corresponding laser wavelength. The ET25 supporting glass co-developed by Hesai and Fuyao is a good example. According to relevant technical materials, the custom glass is optimized for the LiDAR's working wavelength. Under specific test conditions, its infrared laser transmittance can reach up to three times that of ordinary insulated glass.
It should be noted here that a threefold increase in transmittance does not mean the LiDAR's detection range also increases threefold. The relationship between transmittance, received signal strength, and final detection range is not linear. Actual performance is also influenced by factors such as target reflectivity, incident angle, environmental conditions, and sensor performance.
Additionally, it is not necessary to treat the entire front windshield specifically. The solution introduced by Hesai can process specific areas where the LiDAR beam passes through, improving laser signal transmission conditions while balancing the glass's thermal insulation needs.
Transmittance is not the only metric. Both the emitted beam and the received echo from the LiDAR must pass through the glass. The curvature, laminated structure, installation angle, and local optical properties of the glass can all affect light propagation and echo reception. Therefore, specialized glass must not only minimize signal loss but also coordinate with the sensor's optical path design, verifying ranging and angle measurement performance across different field-of-view directions.
Only by considering both transmission performance and optical geometric characteristics can one determine whether hidden integration truly meets perception requirements.
03 Beyond Glass: What Other Problems Must the Sensor Solve?
Even if the glass transmission issue is resolved, cabin-integrated hidden LiDAR still faces challenges regarding volume, field of view, and thermal management. Taking volume as an example, the sensor must fit inside without excessively occupying driver headroom or obstructing the forward view. Especially near the top edge of the front windshield, cameras, rearview mirrors, and other sensors may also be concentrated, leaving limited space for LiDAR. Besides the whole-vehicle integration case of Cadillac VISTIQ, Hesai ET25 helps us understand the technical requirements for cabin-integrated LiDAR.
This is a product specifically designed for installation behind the front windshield, with a body height of 25 mm. According to Hesai's published product data, the ET25's ranging capability against a 10% reflectivity target exceeds 250 meters under unobstructed conditions, reaching 225 meters when installed behind its dedicated supporting windshield. These figures indicate that cabin integration does not necessarily mean failing to meet long-range detection needs.
However, these data remain manufacturer-published product specifications under specific conditions. They cannot be directly generalized to the performance level of all hidden LiDARs, nor interpreted as vehicles being able to stably detect the same distance under any weather or road conditions.
Compressing the LiDAR volume itself involves technical trade-offs. Optical aperture, internal optical paths, scanning mechanisms, and receiving systems are all constrained by space. The more compact the structure, the greater the need to balance effective optical aperture, detection performance, and thermal management within limited space.
Furthermore, once the sensor enters the cabin, its operating temperature and vibration environment must also meet whole-vehicle requirements. The system must remain stable after experiencing high temperatures, low temperatures, and prolonged operation. The design of mounting brackets, housings, and connections to the body affects sensor vibration transmission and mechanical stability, which in turn relates to the reliability of the entire system over the vehicle's long-term use.
Therefore, hidden integration is not merely about pursuing a thinner housing, but ensuring that optics, mechanics, thermal management, and vehicle layout simultaneously meet requirements.
04 Will Hidden LiDAR Become the Mainstream in the Future?
From a vehicle design perspective, hidden LiDAR is indeed attractive. Sensors no longer visibly protrude from the body, reducing constraints on styling imposed by exposed components. For cabin-based solutions, the front windshield can also utilize the wiper system to clean some debris, lowering the risk of direct external contamination and physical damage to the sensor.
But these advantages do not imply that all vehicle models are suitable for the same integration method. External solutions do not require laser signals to pass through the front windshield, offering different degrees of freedom in optical design and mounting position; hidden solutions require additional resolution of issues such as glass material selection, optical processing, cabin space, and internal heat dissipation.
Different mounting positions correspond to different engineering constraints. Roof-mounted solutions offer a higher observation point but must balance appearance, aerodynamic performance, and external protection; solutions behind the front windshield reduce exposed hardware but are limited by glass optical properties and mounting space; low-position options like bumpers require attention to body obstruction, ground-level field of view, and soiling risks.
Whether a specific solution meets requirements depends on sensor field of view, mounting attitude, and whole-vehicle validation results. Automakers' final choice of route depends even more on model positioning, perception performance requirements, body styling, manufacturing costs, and supply chain conditions.
For different LiDAR products, suitable mounting positions may vary. At present, LiDAR is transitioning from a relatively independent external hardware component to a part that must be co-designed with the body, glass, and whole-vehicle electronic systems.
As sensors begin to integrate into the vehicle body, R&D efforts are no longer just about making LiDAR smaller or detecting farther, but also considering how it works together with other automotive systems and maintains long-term stability in real-world usage environments.