Get best of the week

Lidars of the future: 11,000 lasers instead of 128

image

The principle of operation of lidar sensors is to reflect the light of lasers from surrounding objects and create a three-dimensional cloud of points. The first modern three-dimensional lidar was created for the 2005 DARPA Grand Challenge, the main competition among unmanned vehicles. Nowadays, many experts continue to consider lidars as a key technology for unmanned vehicles.

The original 2005 lidar, created by Velodyne, had a vertical array of 64 lasers that rotated 360 degrees, and each laser in the array had to be carefully aligned with an appropriate detector. This complexity has led the price to reach $ 75,000. Today, high-end lidars still cost tens of thousands of dollars.

Now dozens of startups are trying to create cheaper lidars. Many of them are trying to reduce the price using a single laser beam, which is scanned in a two-coordinate model.

However, other companies working with lidars are moving in a different direction: they are building lidars with thousands of lasers. Sense sells lidars with 11,000 lasers for $ 3,000. Another company called Ibeo is working on a lidar with more than 10,000 lasers.

For clarity, we note that the new Ibeo lidar has not yet been released, and therefore we do not know how well it will work, and the Sense lidar performance is far from the performance of the best Velodyne lidar. Sense lidar range is from 15 to 40 meters, while some Velodyne models operate at a distance of 200 meters.

However, Sense CEO Scott Burroughs says their company is just starting out. Sense is working on a new sensor with a range of 200 meters, which is due out next year. It is planned that this model will be able to compete with market leaders. In turn, Ibeo has deep ties with the automotive industry, which allows the company to enter into major transactions with partner car makers.

Microtransfer printing


Both Sense and Ibeo use an inexpensive type of laser - VCSEL lasers. These lasers can be manufactured using conventional semiconductor technology, which allows you to place thousands or even millions of devices on one wafer. Earlier we talked about another startup called Ouster, their lidar is based on VCSEL.

The Sense lidar has a lot more lasers than the Ouster lidar. To achieve this, Sense uses a technology called microtransfer printing .

To place several thousand VCSELs on one chip is not difficult. But when making a chip with 11,000 lasers densely located, you might have problems. Such lasers in such a quantity over a small area can generate a large amount of heat. You may also have eye safety issues. Vertical radiation lasers operate at frequencies that can damage the retina, and 11,000 lasers aimed at the human eye can cause permanent injuries.

Sense has a smart solution to this problem: laser distribution. After installing thousands of lasers with vertical radiation on a gallium arsenide plate, Sense transfers them to a new heat-conducting ceramic substrate, cutting the density of the laser installation.

image


At this point, microtransfer printing comes into play. This technology uses a rubber stamp, at the bottom of which is a mesh with rubber protrusions. When one of the protrusions touches a laser with vertical radiation, it can lift it with the help of static electricity.

image

The protrusions are arranged so that one of every n chips (counting both horizontally and vertically) is lifted from the original plate and placed on a new substrate. Next, the stamp collects a set of chips from the following slots for the next lidar. Thus, a single silicon wafer can form assemblies of 11,000 lasers for multiple lidars.

Sense seeks to increase the range of its lidars


image

Instead of scanning the scene sequentially (as most lidars do), Sense lidars use their 11,000 lasers to illuminate the entire scene in one flash, after which the sensor measures the time it takes for the backlight to reflect from all directions.

Flash lidars like this, as a rule, have a short range, since lighting the entire scene leads to the fact that the light is lost in the spaces between the pixels. In essence, Sense solves this problem by brute force using a large amount of light to illuminate the scene. The distribution of lasers helps to cope with the generated heat and harm to human eyes - problems that could arise with such an approach.

However, Ouster CEO Angus Pascala notes that the Sense approach has a significant drawback: high power consumption. “The more electricity, the more sensors” - Angus comment for Ars. “The larger the sensors, the higher the price and the greater the complexity of integration.”

Despite the fact that current Sense products consume more power than lidars from leading companies, they have a shorter range. Also, the lidars from Ouster and Velodyne rotate 360 ​​degrees, while you will need several Sense lidars in order to get a similar coating.

Burroughs plans to release a lidar with a range of 200 meters in 2021. This lidar will have more than 11,000 lasers, although the exact number is still unknown. The main objective will be to achieve a longer range without an equally significant increase in energy consumption.

Single-photon avalanche diodes come into fashion


image

One of the solutions to this problem is to use an array of single-photon avalanche diodes (SPAD) to detect reflected laser beams in new generation lidar sensors. This is another similarity with the Ouster lidars that use SPAD. In an interview with Ars Technica in 2018, Pacala said his long-term strategy is to use two-dimensional arrays of vertical radiation lasers and sensors on single-photon avalanche diodes, which will create lidars that work like cameras - a product that Sense plans to introduce next year.

As the name implies, sensors on single-photon avalanche diodes are sensitive enough to detect a single photon. Like lasers with vertical radiation, they can be made using conventional silicon technology, which allows them to be cheap in terms of scaling. The greater sensitivity of these sensors can help Sense achieve a greater range for the amount of laser light available.

Interestingly, Ibeo also plans to use single-photon avalanche diodes in their next-generation lidars.

Ibeo is not a startup. Some of their lidars participated in the 2005 DARPA Grand Challenge, although the company’s participation was overlooked because their lidars had only 4 scan lines, while Velodyne lidars had 64. Ibeo made a major coup several years ago when they received Audi's lidar contract is the first time lidars have been installed in production cars. Ibeo's minority shareholder is ZF Friedrichshafen, which helps them enter into even more contracts for the supply of sensors for automobiles.

In an interview given on Thursday, Ibeo COO Mario Bramm told Ars that the next-generation lidar from Ibeo should come out later this year and will have arrays of vertical radiation lasers and single-photon avalanche diodes of dimension 128 by 80. Ibeo strive for a modular design. which will allow the company to use various optics to create a range of models with different capabilities - from long-range lidars with a small viewing angle to wide-angle lidars with a shorter range. Ibeo wants to make these lidars cheap enough to be sold to automotive concerns for mass production from late 2022 or early 2023.

The obvious question is how Ibeo will solve the temperature and eye safety issues that Sense solves using microtransfer printing. One solution is to use highly sensitive single-photon avalanche diodes, so Ibeo can reduce the output power of their lasers enough to avoid problems with power and danger to human eyes. Another solution is to use a direct connection between each laser and the sensor, which will reduce the number of “lost” photons. During our conversation, Bramm said that low power is a priority for customers representing the automotive market.

On the other hand, it may turn out that this approach is difficult to implement without the micro-transfer printing technology used by Sense, while Ibeo and Ouster will try to create solid-state lidars without it.

Correction: At first I stated that the vertical radiation lasers used by Sense are made of silicon - in fact they are based on gallium arsenide.


image

About ITELMA
- automotive . 2500 , 650 .

, , . ( 30, ), -, -, - (DSP-) .

, . , , , . , automotive. , , .

Read more useful articles:

More articles:


All Articles