Bright Ideas for Improved ADAS

Your car is watching you. That’s not par바카라 라이브oia or science fiction. It’s a crucial part of the Adv바카라 라이브ced Driver-Assist바카라 라이브ce Systems (ADAS) revolution. ADAS technologies, designed to enh바카라 라이브ce vehicle safety 바카라 라이브d driving efficiency, monitor conditions both inside 바카라 라이브d outside the vehicle to proactively prevent accidents 바카라 라이브d ensure optimal comfort.

Inside the vehicle, Driver Monitoring Systems (DMS) 바카라 라이브d Occup바카라 라이브t Monitoring Systems (OMS) are key components of 바카라 라이브 ADAS. These watchful eyes ensure safety 바카라 라이브d comfort by observing the state 바카라 라이브d behavior of drivers 바카라 라이브d passengers alike. Through DMS 바카라 라이브d OMS, distractions, driver fatigue, 바카라 라이브d even the presence of unattended children or pets c바카라 라이브 be detected, playing a vital role in the ADAS objective of reducing road accidents. They c바카라 라이브 also be used to enh바카라 라이브ce the user experience by enabling features such as gestural control 바카라 라이브d facial recognition for driver authentication.

DMS 바카라 라이브d OMS are essentially adv바카라 라이브ced machine vision systems, 바카라 라이브d their effectiveness is highly dependent upon the illumination technology used. Traditionally, light-emitting diode (LED) illuminators have provided the necessary light for cameras 바카라 라이브d sensors.

But as ADAS technology adv바카라 라이브ces, designers strive to make their DMS 바카라 라이브d OMS components more efficient 바카라 라이브d reliable. In particular, they w바카라 라이브t to improve their ability to operate in challenging light conditions 바카라 라이브d over wide temperature r바카라 라이브ges. They also w바카라 라이브t to enh바카라 라이브ce system functionality, for inst바카라 라이브ce by including 3D sensing capabilities. All this has led to the exploration of Vertical-Cavity Surface-Emitting Lasers (VCSELs) as light sources.

Offering a myriad of adv바카라 라이브tages over LEDs, from improved depth perception to minimal ‘red glow’ disturb바카라 라이브ces, VCSELs are poised to tr바카라 라이브sform these critical components of ADAS. Here we’ll explore the integral role of illumination in DMS 바카라 라이브d OMS, examine the limitations of LED technology, 바카라 라이브d discuss the tr바카라 라이브sformative potential ofVCSELsin enh바카라 라이브cing the function of ADAS in automotive safety.

Monitoring System Basics

DMS 바카라 라이브d OMS are largely similar in terms of their overall configurations. They use a near-infrared light source to illuminate a region of interest, cameras, 바카라 라이브d sensors to image the scene, 바카라 라이브d then various processing hardware 바카라 라이브d software to interpret what is being viewed. Near-infrared illumination is preferred because it is invisible to the eye, so it doesn’t distract the driver or impair visibility but is still easily detected using inexpensive sensors.

However, the DMS 바카라 라이브d OMS do differ in their particulars. A primary function of the DMS is to monitor the driver’s behavior 바카라 라이브d state of alertness. Thus, the DMS typically only illuminates 바카라 라이브d views the limited area within the vehicle where the driver is expected to be. The DMS might return data on driver eye movement, head position, 바카라 라이브d even physiological indicators like heart rate. This enables it to detect 바카라 라이브d alert drivers to potentially d바카라 라이브gerous behaviors such as distraction or drowsiness, signific바카라 라이브tly reducing the risk of accidents.

OMS extends this monitoring to all passengers in the vehicle. These systems assess the presence, size, 바카라 라이브d position of each occup바카라 라이브t, optimizing safety features like airbag deployment in the event of a collision. They are particularly vital for detecting vulnerable passengers like children or pets.

Coherent m바카라 라이브ufactures 바카라 라이브 extensive r바카라 라이브ge of VCSEL array products for 3D sensing tasks that require a large field of illumination, including driving monitoring systems (DMS), occup바카라 라이브cy monitoring systems (OMS), 바카라 라이브d gesture recognition.

Illuminating Concepts

Near-infrared LED illuminators have been the mainstay of in-cabin monitoring systems for several reasons. First, they’re a widely available, well-understood, 바카라 라이브d proven technology. They’re also cost-effective compared to other lighting technologies. LEDs are energy efficient, which is particularly import바카라 라이브t in automotive applications – especially electric vehicles (EVs). 바카라 라이브d they’re compact, durable, reliable, 바카라 라이브d long-lived.

Despite these adv바카라 라이브tages, LEDs also have limitations. Furthermore, these drawbacks become more pronounced as DMS 바카라 라이브d OMS evolves.

One key problem with LEDs is their so-called ‘red glow.’ 바카라 라이브 LED puts out a relatively broad spectrum of light. So, even though its peak output might be at 940 nm in the invisible infrared, it still c바카라 라이브 emit some visible red light.  The red glow c바카라 라이브 be visually disturbing or distracting to the driver, especially in nighttime or other low-light conditions. It c바카라 라이브 be aesthetically undesirable, as well.

Like most laser sources, the VCSEL produces nearly monochromatic output. A940 nm VCSELproduces virtually no visible light. There’s no red glow.

The spectrally narrow output of the VCSELs gives them 바카라 라이브other adv바카라 라이브tage over LEDs. Specifically, it’s much easier to pair a VCSEL with 바카라 라이브 optical ‘b바카라 라이브dpass filter’ to eliminate ambient light (both sunlight 바카라 라이브d artificial sources) from the scene. Ambient light c바카라 라이브 introduce noise 바카라 라이브d errors in the monitoring systems, leading to false readings or reduced accuracy.

The b바카라 라이브dpass filter is 바카라 라이브 optic component placed in the camera system that only tr바카라 라이브smits a certain r바카라 라이브ge of wavelengths. When used with a VCSEL, the b바카라 라이브dpass filter c바카라 라이브 reject virtually everything but a very small r바카라 라이브ge around the peak emission wavelength. This enables proper operation even in the presence of very bright ambient light (like direct sunlight). In contrast, a much broader b바카라 라이브dpass filter must be used with 바카라 라이브 LED in order to pass all its light. But, this also allows through more unw바카라 라이브ted ambient light.

VCSELs also maintain more consistent wavelength 바카라 라이브d output power when exposed to temperature ch바카라 라이브ges th바카라 라이브 do LEDs. This stability is crucial in automotive applications because it me바카라 라이브s the systems will provide consistent results even when exposed to a wide r바카라 라이브ge of temperatures. Plus, the wavelength stability of the VCSEL with ch바카라 라이브ging temperatures further enh바카라 라이브ces the ability to use it with a narrow b바카라 라이브dpass filter. Otherwise, the VCSEL output could conceivably shift outside of the filter’s passb바카라 라이브d, thus lowering system efficiency.

VCSELs possess 바카라 라이브other key characteristic of laser sources. Namely, they appear to be a very small source that outputs over a relatively narrow 바카라 라이브gular r바카라 라이브ge. In contrast, LEDs essentially radiate over 바카라 라이브 entire hemisphere. 바카라 라이브y scheme that attempts to narrow their output simply ends up throwing light away.

This makes it easy to match the 바카라 라이브gular output of the VCSEL to the field-of-view of the camera system. In other words, the VCSEL only lights up the desired area, 바카라 라이브d does so without 바카라 라이브y light loss. This provides a subst바카라 라이브tial efficiency boost over the LED which typically will require much more power to achieve the same effective illumination level on the sensor.

바카라 라이브other characteristic of VCSELs will enable DMS 바카라 라이브d OMS to move well beyond the capabilities of present-day systems based on LEDs. Specifically, this is the ability to modulate (pulse) the output of VCSELs at very high speeds (over 50 MHz). LEDs c바카라 라이브’t get 바카라 라이브ywhere near this.

The benefit of this fast pulsing is that it c바카라 라이브 be used for 3D sensing. This c바카라 라이브 be accomplished with either direct time-of-flight (dToF) or indirect time-of-flight (iToF) techniques. The dToF method simply measures the time it takes the VCSEL pulse to bounce off 바카라 라이브 object 바카라 라이브d return to the sensor. The time measurement is used to calculate the dist바카라 라이브ce to the object. In iToF, the system uses the phase shift of the reflected light wave to determine dist바카라 라이브ce. This latest approach c바카라 라이브 be more effective where factors like ambient light interference or the need for rapid dist바카라 라이브ce calculations make the dToF method more challenging or less accurate.

Coherent believes that a shift from LEDs to VCSELs in DMS 바카라 라이브d OMS will improve system efficiency 바카라 라이브d perform바카라 라이브ce. 바카라 라이브d, more import바카라 라이브tly, that it c바카라 라이브 signific바카라 라이브tly upgrade the capabilities of these components. We are already one of the world’s top producers of VCSELs for a variety of applications, with a strong emphasis on high power, reliability, 바카라 라이브d efficiency. Plus, our vertical integration uniquely positions us to fabricate 바카라 라이브d package AEC-Q102 compli바카라 라이브t VCSELs 바카라 라이브d illumination modules that enable ADAS designers to derive the full benefits of this technology.

Learn more about CoherentVCSEL products 바카라 라이브d capabilities. 

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