1. Lidar is a very high-tech equipment.

* Bat acoustic demo

Lidar was invented shortly after the invention of the pulsed laser in the early 1960 s. The principle is actually very simple. Just as bats measure the distance to objects based on the sound waves reflected by them, lidar simply replaces sound waves with light waves.

What LIDAR does is emit a pulse and measure the time it takes for it to bounce back from an object. Since the speed of light is constant, it is easy to calculate the distance by measuring the time of flight of light waves.

This physical basis has not changed in the past half century, so the working principle of lidar is quite simple.

2. Lidar is expensive.

* Visible pulsed laser diode

Although the price of laser radar has remained high for a long time due to the high price of laser light sources, the invention of laser diodes has greatly reduced the cost of laser radar.

Now you can buy a visible light pulse laser diode for less than a dollar, and the price of the laser light source is no longer the main factor affecting the price of lidar. For an imaging lidar capable of multi-point measurements, an increased cost is often associated with its imaging method.

The innovative approach of Cepton Micro-motion Technology (MMT) makes an imaging lidar that will not exceed the price of a normal camera.

3. Solid-state lidar has no moving parts, which is the best method.

Solid-state lidar with no moving parts is just one aspect of the improved laser architecture. The wear-free structure enhances the reliability of the lidar. However, the wear-free mechanism will greatly reduce the performance of the lidar.

The most illustrative manifestation of the problem is that the measurement distance of the lidar is reduced, the field of view is reduced, or it is more sensitive to environmental light sources (such as sunlight).

In addition, the high cost of solid-state lidar has also become a factor hindering its large-scale deployment in the consumer market.

4. Flash lidar is the best imaging lidar.

* NASA flash lidar imaging

The National Aeronautics and Space Administration (NASA) used flash lidar in space station docking operations. The lidar used in the system has high resolution and long detection range.

However, in order to achieve the required performance, the cost of the wavelength (1550nm) and the required power (peak power ~ 100 kW) of the lidar is well over a million dollars.

Although the imaging performance of flash lidar is indeed the best, the average car does not need a sensor that costs millions of dollars.

5.1550 lasers are eye-safe and 905 unsafe.

* Wavelength diagram

Eye safety is affected by many factors, not just wavelength. In addition to wavelength, the safety level also depends on factors such as power, divergence angle, pulse duration, exposure direction, etc.

Other things being similar, the power of the 1550nm laser is higher than that of the 905nm laser within a safe range. However, engineers tend to design sensitive optical detectors that do not require high-power lasers. Compared with the high-cost 1550nm laser source, the 905nm laser based on silicon process is more suitable, especially in the automotive market which is highly sensitive to cost.

6. Lidar cannot work in bad weather conditions.

* Bad airport weather conditions

Like a camera, lidar is an optical device. If the fog blocks all light transmission, the lidar does fail. But in order to quantify this effect, the aviation community clearly defined the physical quantity "visibility", that is, in the absence of light background, can see and identify the light intensity of the light source of the 1000 candela maximum distance.

According to the landing restrictions of the visual flight rules, when the visibility is greater than 1800 feet, the performance of the lidar will not be affected.

7. Lidar is only suitable for cars.

* Apollo 11 used lasers to accurately measure the distance between the Earth and the Moon for the first time.

Lidar has only been used in cars in recent years.

When lidar was first invented half a century ago, its most widely known application was to measure the distance between the Earth and the Moon. Later, lidar was used to measure the distance between the ground and clouds and other weather conditions.

Today, lidar can be used in any application that requires measuring the distance of an object. As the cost of lidar decreases, lidar will be used for infrastructure such as intersections and security.

8.CEPTON's micro-motion technology is the same as MEMS.

* Cepton Vista onboard lidar

The micro-motion technology (MMT) invented by Cepton uses frictionless electromagnetic drive motion for optical scanning. This design differs from MEMS, which primarily uses a galvanometer for beam scanning.

No galvanometer is involved in the optical path of the Cepton lidar, simplifying the structure and keeping the light energy loss to a minimum.

9. Lidar must use infrared light.

Lidar can be used as long as it can generate short pulse light waves.

In fact, green lasers are often used for lidar measurements. For automotive applications, any visible laser light will cause driver distraction, so infrared light that is invisible to the human eye is usually selected. Proper filtering can also improve the performance of lidar in ambient light, such as the illumination of car headlights.

10.FMCW lidar is superior to TOF radar.

FMCW (frequency modulated continuous wave) lidar measures the phase difference of light waves, not the time of flight, so the measurement accuracy is higher (from millimeters to microns). Such high accuracy is necessary for survey applications, but it is not necessary for cars to detect obstacles. Accuracy on the centimeter level is sufficient.

FMCW lidar is very complex and expensive, and even for L4 to L5 autonomous driving applications, it is not attractive.

Lidar can be replaced by cameras, radar, or a combination of both.

The most prominent feature of laser radar is that it also has a high spatial resolution when measuring three-dimensional objects. The radar can detect a car parked in front, but cannot tell whether the car is parked in front or next to it. Without adequate ambient lighting, the camera will become useless.

In fact, lidar, radar and cameras are expected to be equipped together in autonomous vehicles at L3 and above.