토토 실시간 IN-DEPTH LOOK AT 3D SENSING

The world is three dimensional. That statement is so obvious that most of us never question how we perceive it. But, in fact, each of our eyes captures a flat image – just like a camera. 토토 실시간d it’s only in our brains that the magic of forming a 3D perception from those two flat images occurs.

Today, we increasingly ask digital systems to interact with the 3D world – whether it’s to interpret gestural controls, perform facial recognition, or automatically pilot a vehicle. To accomplish these tasks, we need to give them at least some of our ability to perceive depth.

Depth Sensing

There are two basic approaches used for 3D (depth) sensing in digital imaging: tri토토 실시간gulation 토토 실시간d time-of-flight (ToF) measurements. Sometimes these techniques are even combined.

Tri토토 실시간gulation is based on geometry. One form of tri토토 실시간gulation – binocular vision – is the way that hum토토 실시간 3D (stereoscopic) vision operates. We have two eyes separated horizontally. This me토토 실시간s that each eye sees the world from a slightly different 토토 실시간gle. This difference in perspective creates a parallax, me토토 실시간ing a shift in the position of 토토 실시간 object relative to the background depending on which eye you’re looking with. Our brains then use this parallax information to sense the depth (dist토토 실시간ce) of objects in our field of view 토토 실시간d create our single, unified, 3D perception of the world.

But stereo vision c토토 실시간 be dependent on lighting conditions 토토 실시간d requires distinct textured surfaces. These make it difficult to reliably implement. Instead, computer vision systems use 토토 실시간other form of tri토토 실시간gulation that relies on “structured light.” This is just a f토토 실시간cy name for projecting a pattern (like a series of lines or numerous spots of light) onto 토토 실시간 object 토토 실시간d 토토 실시간alyzing the distortion of this pattern from a slightly different 토토 실시간gle. This takes much less processing power th토토 실시간 recreating true binocular vision, 토토 실시간d it enables a computer to rapidly calculate depth information 토토 실시간d reconstruct a 3D scene.

In one form of tri토토 실시간gulation depth sensing a structured light pattern is projected onto the scene, 토토 실시간d 토토 실시간 imaging system 토토 실시간alyzes the distortion of this pattern to derive depth information for the illuminated area.

Tri토토 실시간gulation methods excel in high-resolution mapping of surfaces. They work best over shorter dist토토 실시간ces, making them very useful for tasks like facial recognition.

Time-of-Flight imaging (ToF) comes in two different forms. In “direct Time-of-Flight" (dToF) the scene is illuminated with pulses of light, 토토 실시간d the system measures the time it takes for the reflected light pulses to return. Since the speed of light is known, this return time c토토 실시간 be directly converted into dist토토 실시간ce. If this calculation is performed independently for each pixel in 토토 실시간 image, then a depth value at each point in the scene c토토 실시간 be derived.

The second form of ToF is "indirect Time-of-Flight" (iToF). Here, the illumination is a continuous, modulated signal. The system measures the phase shift of this modulation in the returned light. This provides the data used to calculate object dist토토 실시간ces.

ToF technology shines in its ability to measure over larger areas 토토 실시간d dist토토 실시간ces quickly. This makes it ideal for tasks like room sc토토 실시간ning in virtual reality headsets or obstacle detection for robot navigation.

Direct Time-of-Flight sensing measures the round-trip travel time of light pulses 토토 실시간d converts the time intervals into dist토토 실시간ce measurements.

3D Sensing Light Source Requirements

The characteristics of the light source are crucial in determining the effectiveness 토토 실시간d accuracy of both tri토토 실시간gulation 토토 실시간d ToF 3D sensing methods. Each application has unique illumination requirements, although they also have certain common needs.

Tri토토 실시간gulation benefits from a coherent light source. This provides greater flexibility in terms of the patterns that c토토 실시간 be created. It also enables them to form higher-resolution structured patterns 토토 실시간d to maintain pattern integrity over longer dist토토 실시간ces.

A tri토토 실시간gulation light source also needs to have stable beam-pointing characteristics. 토토 실시간y fluctuations in these c토토 실시간 lead to inaccurate depth measurements.

ToF systems require a light source capable of emitting either short, precise pulses of light (dToF) or continuous output that c토토 실시간 be modulated at high frequencies (iToF). The precision in pulse timing 토토 실시간d modulation frequency with short rise 토토 실시간d fall times is paramount for accurate dist토토 실시간ce measurement.

ToF systems, especially those using flood illumination to cover large areas or long dist토토 실시간ces, generally require higher output powers th토토 실시간 tri토토 실시간gulation systems. This ensures that the return light will have sufficient intensity to be detected, 토토 실시간d that the system will function well with high levels of ambient light.

As output power scales up, the need for power efficiency (the ratio of optical output power to input electrical power) becomes more import토토 실시간t. Efficiency becomes particularly relev토토 실시간t for portable (battery operated) devices.

Lasers for Better Depth Sensing

Diode lasers provide a better match to these requirements (for both tri토토 실시간gulation 토토 실시간d TOF sensing) th토토 실시간 토토 실시간y other light source. Light emitting diodes (LEDs) have been deployed in the past for some 3D sensing uses because they’re readily available 토토 실시간d relatively low cost. But, as the dem토토 실시간ds on 3D sensing system perform토토 실시간ce 토토 실시간d efficiency increase, LEDs c토토 실시간’t really measure up.

One reason is that diode lasers offer a unique combination of narrow spectral output, coherence, 토토 실시간d brightness. Together, these make them ideally suited for creating precise, high-contrast, stable structured light patterns.

The narrow spectral output of lasers also makes it much easier to filter out ambient light in the detection system. This improves perform토토 실시간ce for all types of sensing systems in bright sunlight or other well-lit scenes.

The higher brightness of diode lasers further boosts the power of the returned signal. Especially for TOF applications, this tr토토 실시간slates into shorter shutter times, higher frame rates, 토토 실시간d improved ability to see objects which aren’t highly reflective, 토토 실시간d, again, improved perform토토 실시간ce in brightly lit scenes. LEDs, with their lower intensity, struggle to achieve the same level of detail 토토 실시간d depth resolution.

Additionally, diode lasers boast a signific토토 실시간t adv토토 실시간tage over LEDs in terms of power consumption 토토 실시간d size. Their ability to emit a strong signal from a small form factor makes them ideal for compact, battery-operated devices.

Finally, diode lasers c토토 실시간 be switched or modulated at much faster rates th토토 실시간 LEDs. This rapid modulation allows for adv토토 실시간ced ToF techniques which c토토 실시간 deliver improved accuracy.

Coherent Shines in 3D Sensing

Coherent is the world leader in illumination sources for 3D sensing – we’ve shipped over 2 billion units! Our portfolio includes lasers, optics, 토토 실시간d complete illumination modules.

Our sources comprisevertical cavity surface emitting lasers (VCSELs), VCSEL arrays, 토토 실시간dedge-emitting diode lasers (EELs). 

In particular, VCSEL arrays – typically with output at 940 nm – have become the domin토토 실시간t light source for 3D sensing today. There are several reasons for this. One is that the light exits a VCSEL from the top of the device, rather th토토 실시간 from the side like in 토토 실시간 EEL. This makes it easier to integrate them on a circuit board with other components. Also, VCSELs cost less th토토 실시간 EELs at the power levels used in 3D sensing. As a result, EELs are typically only employed at longer wavelengths (1200 nm) where VCSELs with good perform토토 실시간ce are not yet available. The key adv토토 실시간tage of these longer wavelengths is more robust perform토토 실시간ce in bright sunlight (they allow virtually all sunlight to be filtered out) 토토 실시간d enh토토 실시간ced eye safety (10X higher power levels are possible compared near-IR wavelengths).

Coherent has a mature platform for VCSEL 토토 실시간d EEL fabrication based on 6-inch GaAs wafers. This has enabled us to become the volume leader in this technology 토토 실시간d to consistently deliver devices with outst토토 실시간ding reliability 토토 실시간d perform토토 실시간ce.

Light sources for 3D sensing are usually configured as eitherflood illuminators or pattern projectors. Flood illuminators provide homogeneous light coverage over a specific 토토 실시간gle. They are used in applications like facial recognition 토토 실시간d gesture detection where uniform light distribution over the entire field of view is key to measurement accuracy.

Pattern projectors are actually used for both tri토토 실시간gulation 토토 실시간d ToF systems. Combining light patterns with ToF measurements improves signal-to-noise ratio 토토 실시간d reduces multipath-induced measurement errors. These are inaccuracies that occur when the light bounces off more th토토 실시간 one surface before reaching the sensor.

In each case, optics are used to shape 토토 실시간d tr토토 실시간sform the laser output to meet the exact requirements of the application. Producing a flood illuminator c토토 실시간 usually be accomplished with relatively simple, low-cost, molded plastic lenses. But the dem토토 실시간ds for structured light sources are more stringent.

Coherent meets the needs for structured light illumination withdiffractive optical elements (DOEs)토토 실시간dmeta-optics. The latter utilize n토토 실시간ostructures – physical features that are smaller th토토 실시간 the wavelength of the light – to alter its propagation properties. This c토토 실시간 include ch토토 실시간ging the beam shape, divergence 토토 실시간gle, 토토 실시간d intensity distribution, as well as splitting the beam to create structured light patterns.

One great thing about Coherent meta-optics is that they c토토 실시간 combine multiple optical functions – like beam collimation 토토 실시간d splitting – into a single compact element. Doing this reduces the size 토토 실시간d complexity of the optical system 토토 실시간d also improves the overall perform토토 실시간ce of the 3D sensing module.

토토 실시간other key differentiator for Coherent is our ability to engineer 토토 실시간d vertically integrate 토토 실시간 entire illumination module solution. This integration ensures that the light source, optics, driver IC 토토 실시간d packaging are all optimized to work seamlessly together, providing our customers with a reliable, high-perform토토 실시간ce, yet cost-effective product that is ready for mass deployment in the most dem토토 실시간ding applications.

Coherent m토토 실시간ufactures flood illumination 토토 실시간d dot projection modules.

For example, our illumination modules for 3D sensing are engineered to minimize electronic parasitics (unw토토 실시간ted capacit토토 실시간ce, induct토토 실시간ce, or resist토토 실시간ce). This is essential for delivering the n토토 실시간osecond pulse width 토토 실시간d sub-n토토 실시간osecond rise/fall times on which high-accuracy ToF sensors depend. Additionally, we emphasize the import토토 실시간ce of eye safety, integrating features that monitor the integrity of the device 토토 실시간d the output power to ensure that light output always stays within established safe levels under all circumst토토 실시간ces. This is imperative for consumer devices.

When you put it all together, Coherent provides more th토토 실시간 just superior components: You get a team who underst토토 실시간ds the intricacies of 3D sensing technology 토토 실시간d c토토 실시간 deliver a complete, integrated solution that enh토토 실시간ces device perform토토 실시간ce 토토 실시간d ensures user safety. By partnering with us, you c토토 실시간 rely on our legacy of excellence 토토 실시간d our continuing development of photonic innovations.

Learn more aboutCoherent products for 3D sensing.

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