Tag Archives: LIDAR


A solid-state Lidar chip works by emitting laser light from an optical antenna. A tiny switch turns the antenna on and off. The light reflects off the sample and the same antenna captures it. For 3D imaging, the Lidar chip has an array of such antennae. The switches sequentially turn them on in the array.

An array of MEMS switches for high-resolution solid-state Lidar can reduce its cost significantly. This allows the solid-state Lidar to match other inexpensive chip-based radar and camera systems. This removes the major barrier to the adoption of Lidar for autonomous vehicles.

At present, autonomous highway driving and collision avoidance systems use inexpensive chip-based radar and cameras as their mainstream building blocks. At the same time, Lidar navigation systems, being mechanical devices and unwieldy, are also expensive, costing thousands of dollars.

However, researchers at the University of California, Berkeley, are working on a new type of high-resolution Lidar chip and this may be the game-changer. The new Lidar uses an FPSA or Focal Plane Switch Array. This is a matrix of micron-scale antennas made of semiconductors. Just like the sensors in digital cameras do, these antennas also gather light. While smartphone cameras have impressive resolutions of millions of pixels, FPSA on the new Lidar has a resolution of only 16,384 pixels. However, this is substantially larger than the 512 pixels that the current FPSA has.

Another advantage of the new FPSA is its design is scalable. Using the same CMOS or Complementary Metal-Oxide Semiconductor technology that produces computer processors, it is possible to reach megapixel sizes easily. According to the researchers, this can lead to a new generation of 3D sensors that are not only immensely powerful but also low-cost. Such powerful 3D sensors will be of great use in smartphones, robots, drones, and autonomous cars.

Surprisingly, the new Lidar system works the same way as mechanical Lidar systems do.  Mechanical Lidars also use lasers for visualizing objects situated several hundreds of yards away, even when they are in the dark. They also generate high-resolution 3D maps for the artificial intelligence in a vehicle for distinguishing between obstacles like pedestrians, bicycles, and other vehicles. But for over a decade, researchers have tried to put these capabilities on a chip, without success, up until now.

The idea is to illuminate a large area. However, the larger the area illuminated, the weaker is the light intensity. This does not allow reaching a reasonable distance. Therefore, researchers had to make a trade-off for maintaining the light intensity. They had to reduce the area that their laser light was illuminating.

The new Lidar has an FPSA matrix consisting of tiny optical transmitters. Each transmitter has a MEMS switch that can rapidly turn on and off. This allows time for the waveguides to move from one position to another while allowing channeling the entire laser power through a single antenna at any time.

Routing light in communications networks commonly uses MEMS switches. The researchers have used this technology for the first time for Lidar. Compared to the thermo-optic switches that the mechanical Lidar uses, the MEMs switches have the advantage of being much smaller, consuming far less power, operating faster, and performing with significantly lower light losses.

Metamaterials Improve LIDAR

Light Detection and Ranging or LIDAR is a remote sensing method. The technique uses the time of flight of pulsed laser light to measure variable distances. Airborne systems record additional data, which, when combined with the data from the light pulses are able to generate three-dimensional information about the neighboring environment that offer precise surface characteristics.

In general, a LIDAR comprises a laser, a scanner, and a specialized receiver for Global Positioning System or GPS. Although so far, common platforms for LIDAR used helicopters and airplanes for acquiring data over broad areas, autonomous vehicles are now using Topographic LIDAR extensively for navigation through road traffic using a near-infrared laser to map the nearby area.

Using LIDAR systems help scientists and engineering professionals examine both artificial and natural environments with precision, accuracy, and flexibility. As the market for LIDAR is still in its nascent state and its technologies fragmented, there are only about 70 LIDAR companies worldwide, making it a hotbed of new technology.

For scanning a wide area, conventional LIDAR systems have to rely on electro-mechanical spinners to steer laser light beams. Not only does this method reduce the scan speed, but it also affects measurement accuracy. A Seattle-based, venture-backed startup, Lumotive, is now developing a new technology that will change the way LIDAR systems function.

According to Bill Colleran, co-founder, and CEO of Lumotive, they are developing a LIDAR system that can steer beams but has no moving parts. Rather, their patented technology uses the light-bending properties of metamaterials such as Liquid Crystal Metasurfaces or LCM to steer the laser beams. Bill calls the use of such metamaterials “pivotal technology.”

However, Lumotive is not the only player in the field to offer LIDAR systems that do not rely on mechanical scanning. Other rivals have used optical phased arrays or MEMS mirrors to claim their LIDARs use a lower number or no mechanical components.

According to Bill, Lumotive LIDAR systems use LCM semiconductor chips. The main advantages of LCM are it offers a large optical aperture of about 25 x 25 mm, resulting in a longer range for the LIDAR, along with a 120-degree field of view. The high performance of the LCM comes from its fast-random-access beam steering capability.

When a laser beam shines onto the Lumotive’s liquid crystal metasurface chip, programmed electrical signals can direct the reflected light into any direction within its 120-degree field of view.

Metamaterials are mostly artificially structured materials that allow unprecedented control over their properties, specifically in new ways for controlling the flow of electromagnetic radiation including light. For instance, Kymeta has a flat-panel satellite antenna technology based on metamaterials.

Kymeta’s antenna can move electronically. It does not require the conventional phase shifters, amplifiers, and related components on its surface. This not only cuts down the cost, it also consumes far less power and does not require cooling devices. Compared to conventional antenna systems, Kymeta is able to increase the density of their flat-panel antenna elements dramatically, while controlling the phase and amplitude simply by activating or deactivating individual antenna elements. Lumotive have adapted the Kymeta antenna’s metamaterial architecture to their LIDAR system.

What Active Safety Systems do Cars Use?

As cars move towards independence from drivers, and become more self-reliant, they are also becoming smarter and safer. Manufacturers are using newer systems every year for the assistance of drivers with the systems increasingly employing advanced technology and data processing. Among such advanced technology range from automatic high-bean control to pre-collision braking systems, and these are now becoming the norm in practically all kinds of cars.At present, the active safety systems manufacturers use in cars are mainly in the form of three major sensors – LIDAR, radar, and cameras. While assisting drivers in cars, these sensors offer benefits in different ways. Manufacturers also combine these with other sensors for achieving better solutions.

Light Detection and Ranging – LIDAR

This technology relies on lasers to measure distance. When used for automotive applications, the LIDAR system uses infrared lasers firing hundreds of pulses every second. The system measures the time of flight for the reflected light to return to the sensor. The distance to the object is then half of the time of flight times the speed of light.

LIDAR systems are in use by major car manufacturers, including Toyota, Volvo, Continental, and Infinity. These and other manufacturers often combine LIDAR sensors with other technologies such as radar and cameras to provide additional information. For instance, the MFL system from Continental combines LIDAR with a multifunctional camera that Toyota uses for providing automatic high-beam control, lane departure alert and a pre-collision system.

Radio Detection and Ranging – RADAR

One of the oldest and predominant sensor technologies, radar is used for advanced driver safety systems in automotive applications. These safety systems measure the time of flight, frequency shift, and the amplitude of the return signal for determining the relevant information. Automotive applications use radar systems for monitoring blind spots and provide warning for forward collision.

Similar to the LIDAR sensors, other technologies are used in conjunction with radar to obtain better information. By combining a camera and radar into a single package system, mounted in front of the rearview mirror inside the car, it offers multiple functionality such as traffic sign recognition, headlight control, object detection, pedestrian detection, full autonomous braking, pre-crash collision mitigation, forward collision warning, headway alert, lane departure warning/lane keeping, and full-speed adaptive cruise control.

Daylight and Night Vision Cameras

Driver assistance systems majorly rely on cameras, either on their own or by augmenting other systems using computer vision algorithms. Powerful processors extract valuable data using sophisticated image processing in real time. Some cars contain multiple cameras for providing different forms of data to the driver.

Cameras are also useful in assisting the driver to remain attentive when driving. For instance, the Driver Status Monitor from DENSO uses a system of cameras for detecting the driver’s head position, drowsiness level, long-duration eye closure, and the face angle to determine if the driver is distracted of drowsy. IR LEDs provide illumination for nighttime detection. The system then produces a suitable warning for the driver.

In the Future

A decade ago, such systems would be part of science fiction and even five years earlier, these safety systems were part only of luxury vehicles. However, these are commonplace now. Maybe, within the next five to ten years, self-driving cars will be the norm and people will take these and other safety systems for granted.

LIDAR and the Raspberry Pi

For hackers and DIY enthusiasts, it is always a challenge to make correct measurements between their robots and nearby objects such as an autonomous vehicle. Estimating the distance is important for the robot to make a decision about avoiding bumping into obstacles. Although this may be considered trivial for a small robot running into a wall, it could turn out deadly for the same robot encountering an autonomous vehicle.

In 2013, NASA held a competition called SRR or Sample Return Robot, where several entrants used various techniques for making measurements using visual aids such as cameras. Two entrants used LIDAR, which can also be used with the single board computer, the Raspberry Pi, or RBPi.

Although using similar methods, LIDAR uses light for measurements, rather than its forerunner RADAR or Radio Detection and Ranging. According to the Merriam-Webster dictionary, LIDAR was first used 1963 for measurement of clouds and Apollo 13 used it to measure the surface of the moon. Since then, the reductions in the size of lasers have led to additional uses, including the military using LIDAR for range finding.

A scanning LIDAR uses the laser beam to sweep a wide area both vertically and horizontally. The feedback provides a cloud of distantness measurement points. This is similar to aircraft control radar swinging a beam through the sky. There are two principal methods for measuring distances using a laser. One is to measure the time of flight of a laser pulse and the other is to measure the angle by which the laser beam deflects.

For the time of flight measurement, you send out a pulse of laser and measure the time for the signal to return. That time divided by the speed of light gives the distance the laser traveled out and back. The distance to the object is then half the calculated distance. Given the high speed at which light travels, it is difficult to measure distances below a meter using lasers, because light would be returning in about seven nanoseconds. LIDAR uses continuous modulation of the laser by amplitude or frequency and measures the phase difference between the transmitted and received signals. This process using modulation allows measurements down to centimeters.

The LIDAR is actually a sealed unit with a motor at one end that spins a turret at about 300 RPM. Inside the turret are the laser and the receiving sensor. Spinning allows a 360-degree scan of the surrounding area. There are two optical ports out of the turret, corresponding to the laser and the sensor. A two-pin connector provides power to the motor. Another four pin connector is for supplying the inner control and serial interface circuits with 5V and 3V3 DC.

WiringPi is a library of programming the GPIO on the RBPi that offers an absurdly simple and minimal user interface for handling the LIDAR. Additionally, WiringPi is suitable for several RBPi models. Another advantage in using WiringPi is its ability to do hardware PWM on one GPIO pin of the RBPi. Another possibility is to use PID or Proportional Integral Differential control system in a loop to maintain constant speed of the turret motor.