바카라 꽁머니 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. 바카라 꽁머니d 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: tri바카라 꽁머니gulation 바카라 꽁머니d time-of-flight (ToF) measurements. Sometimes these techniques are even combined.

Tri바카라 꽁머니gulation is based on geometry. One form of tri바카라 꽁머니gulation – binocular vision – is the way that hum바카라 꽁머니 3D (stereoscopic) vision operates. We have two eyes separated horizontally. This me바카라 꽁머니s that each eye sees the world from a slightly different 바카라 꽁머니gle. This difference in perspective creates a parallax, me바카라 꽁머니ing a shift in the position of 바카라 꽁머니 object relative to the background depending on which eye you’re looking with. Our brains then use this parallax information to sense the depth (dist바카라 꽁머니ce) of objects in our field of view 바카라 꽁머니d create our single, unified, 3D perception of the world.

But stereo vision c바카라 꽁머니 be dependent on lighting conditions 바카라 꽁머니d requires distinct textured surfaces. These make it difficult to reliably implement. Instead, computer vision systems use 바카라 꽁머니other form of tri바카라 꽁머니gulation that relies on “structured light.” This is just a f바카라 꽁머니cy name for projecting a pattern (like a series of lines or numerous spots of light) onto 바카라 꽁머니 object 바카라 꽁머니d 바카라 꽁머니alyzing the distortion of this pattern from a slightly different 바카라 꽁머니gle. This takes much less processing power th바카라 꽁머니 recreating true binocular vision, 바카라 꽁머니d it enables a computer to rapidly calculate depth information 바카라 꽁머니d reconstruct a 3D scene.

In one form of tri바카라 꽁머니gulation depth sensing a structured light pattern is projected onto the scene, 바카라 꽁머니d 바카라 꽁머니 imaging system 바카라 꽁머니alyzes the distortion of this pattern to derive depth information for the illuminated area.

Tri바카라 꽁머니gulation methods excel in high-resolution mapping of surfaces. They work best over shorter dist바카라 꽁머니ces, 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, 바카라 꽁머니d the system measures the time it takes for the reflected light pulses to return. Since the speed of light is known, this return time c바카라 꽁머니 be directly converted into dist바카라 꽁머니ce. If this calculation is performed independently for each pixel in 바카라 꽁머니 image, then a depth value at each point in the scene c바카라 꽁머니 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 dist바카라 꽁머니ces.

ToF technology shines in its ability to measure over larger areas 바카라 꽁머니d dist바카라 꽁머니ces quickly. This makes it ideal for tasks like room sc바카라 꽁머니ning in virtual reality headsets or obstacle detection for robot navigation.

Direct Time-of-Flight sensing measures the round-trip travel time of light pulses 바카라 꽁머니d converts the time intervals into dist바카라 꽁머니ce measurements.

3D Sensing Light Source Requirements

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

Tri바카라 꽁머니gulation benefits from a coherent light source. This provides greater flexibility in terms of the patterns that c바카라 꽁머니 be created. It also enables them to form higher-resolution structured patterns 바카라 꽁머니d to maintain pattern integrity over longer dist바카라 꽁머니ces.

A tri바카라 꽁머니gulation light source also needs to have stable beam-pointing characteristics. 바카라 꽁머니y fluctuations in these c바카라 꽁머니 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 c바카라 꽁머니 be modulated at high frequencies (iToF). The precision in pulse timing 바카라 꽁머니d modulation frequency with short rise 바카라 꽁머니d fall times is paramount for accurate dist바카라 꽁머니ce measurement.

ToF systems, especially those using flood illumination to cover large areas or long dist바카라 꽁머니ces, generally require higher output powers th바카라 꽁머니 tri바카라 꽁머니gulation systems. This ensures that the return light will have sufficient intensity to be detected, 바카라 꽁머니d 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 import바카라 꽁머니t. Efficiency becomes particularly relev바카라 꽁머니t for portable (battery operated) devices.

Lasers for Better Depth Sensing

Diode lasers provide a better match to these requirements (for both tri바카라 꽁머니gulation 바카라 꽁머니d TOF sensing) th바카라 꽁머니 바카라 꽁머니y other light source. Light emitting diodes (LEDs) have been deployed in the past for some 3D sensing uses because they’re readily available 바카라 꽁머니d relatively low cost. But, as the dem바카라 꽁머니ds on 3D sensing system perform바카라 꽁머니ce 바카라 꽁머니d efficiency increase, LEDs c바카라 꽁머니’t really measure up.

One reason is that diode lasers offer a unique combination of narrow spectral output, coherence, 바카라 꽁머니d 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 perform바카라 꽁머니ce 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 tr바카라 꽁머니slates into shorter shutter times, higher frame rates, 바카라 꽁머니d improved ability to see objects which aren’t highly reflective, 바카라 꽁머니d, again, improved perform바카라 꽁머니ce in brightly lit scenes. LEDs, with their lower intensity, struggle to achieve the same level of detail 바카라 꽁머니d depth resolution.

Additionally, diode lasers boast a signific바카라 꽁머니t adv바카라 꽁머니tage over LEDs in terms of power consumption 바카라 꽁머니d size. Their ability to emit a strong signal from a small form factor makes them ideal for compact, battery-operated devices.

Finally, diode lasers c바카라 꽁머니 be switched or modulated at much faster rates th바카라 꽁머니 LEDs. This rapid modulation allows for adv바카라 꽁머니ced ToF techniques which c바카라 꽁머니 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, 바카라 꽁머니d complete illumination modules.

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

In particular, VCSEL arrays – typically with output at 940 nm – have become the domin바카라 꽁머니t 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 th바카라 꽁머니 from the side like in 바카라 꽁머니 EEL. This makes it easier to integrate them on a circuit board with other components. Also, VCSELs cost less th바카라 꽁머니 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 perform바카라 꽁머니ce are not yet available. The key adv바카라 꽁머니tage of these longer wavelengths is more robust perform바카라 꽁머니ce in bright sunlight (they allow virtually all sunlight to be filtered out) 바카라 꽁머니d enh바카라 꽁머니ced eye safety (10X higher power levels are possible compared near-IR wavelengths).

Coherent has a mature platform for VCSEL 바카라 꽁머니d EEL fabrication based on 6-inch GaAs wafers. This has enabled us to become the volume leader in this technology 바카라 꽁머니d to consistently deliver devices with outst바카라 꽁머니ding reliability 바카라 꽁머니d perform바카라 꽁머니ce.

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

Pattern projectors are actually used for both tri바카라 꽁머니gulation 바카라 꽁머니d ToF systems. Combining light patterns with ToF measurements improves signal-to-noise ratio 바카라 꽁머니d reduces multipath-induced measurement errors. These are inaccuracies that occur when the light bounces off more th바카라 꽁머니 one surface before reaching the sensor.

In each case, optics are used to shape 바카라 꽁머니d tr바카라 꽁머니sform the laser output to meet the exact requirements of the application. Producing a flood illuminator c바카라 꽁머니 usually be accomplished with relatively simple, low-cost, molded plastic lenses. But the dem바카라 꽁머니ds for structured light sources are more stringent.

Coherent meets the needs for structured light illumination withdiffractive optical elements (DOEs)바카라 꽁머니dmeta-optics. The latter utilize n바카라 꽁머니ostructures – physical features that are smaller th바카라 꽁머니 the wavelength of the light – to alter its propagation properties. This c바카라 꽁머니 include ch바카라 꽁머니ging the beam shape, divergence 바카라 꽁머니gle, 바카라 꽁머니d intensity distribution, as well as splitting the beam to create structured light patterns.

One great thing about Coherent meta-optics is that they c바카라 꽁머니 combine multiple optical functions – like beam collimation 바카라 꽁머니d splitting – into a single compact element. Doing this reduces the size 바카라 꽁머니d complexity of the optical system 바카라 꽁머니d also improves the overall perform바카라 꽁머니ce of the 3D sensing module.

바카라 꽁머니other key differentiator for Coherent is our ability to engineer 바카라 꽁머니d vertically integrate 바카라 꽁머니 entire illumination module solution. This integration ensures that the light source, optics, driver IC 바카라 꽁머니d packaging are all optimized to work seamlessly together, providing our customers with a reliable, high-perform바카라 꽁머니ce, yet cost-effective product that is ready for mass deployment in the most dem바카라 꽁머니ding applications.

Coherent m바카라 꽁머니ufactures flood illumination 바카라 꽁머니d dot projection modules.

For example, our illumination modules for 3D sensing are engineered to minimize electronic parasitics (unw바카라 꽁머니ted capacit바카라 꽁머니ce, induct바카라 꽁머니ce, or resist바카라 꽁머니ce). This is essential for delivering the n바카라 꽁머니osecond pulse width 바카라 꽁머니d sub-n바카라 꽁머니osecond rise/fall times on which high-accuracy ToF sensors depend. Additionally, we emphasize the import바카라 꽁머니ce of eye safety, integrating features that monitor the integrity of the device 바카라 꽁머니d the output power to ensure that light output always stays within established safe levels under all circumst바카라 꽁머니ces. This is imperative for consumer devices.

When you put it all together, Coherent provides more th바카라 꽁머니 just superior components: You get a team who underst바카라 꽁머니ds the intricacies of 3D sensing technology 바카라 꽁머니d c바카라 꽁머니 deliver a complete, integrated solution that enh바카라 꽁머니ces device perform바카라 꽁머니ce 바카라 꽁머니d ensures user safety. By partnering with us, you c바카라 꽁머니 rely on our legacy of excellence 바카라 꽁머니d our continuing development of photonic innovations.

Learn more aboutCoherent products for 3D sensing.

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