White Paper : Platanus® Diffuser for 3D‐TOF Sensors
1. Introduction
3D sensing technology is a technology to acquire not only 2D images but also depth (distanceinformation) as image data. In recent years, technology for measuring the distance of objects reflectedwith a camera has been widely used not only in conventional industrial measurement applications, butalso in consumer applications such as automated driving, augmented reality (AR) and virtual reality (VR)game devices mounted on smartphones, and robot home appliances, as shown in Figure 1.
Among 3D sensing technologies, Time of Flight(TOF) sensing is a measurement technique that
calculates the distance between a camera and anobject based on the time it takes for irradiatedlight to be reflected back to the object. This
technology has advantages such as smaller
system size, less CPU load during dataacquisition, and the ability to be used in darkareas.
The optical diffuser for TOF sensing discussed
here is an optical element that controls the light
distribution so that the light emitted from thelight source and transmitted through the element
is irradiated with the desired intensitydistribution in the field of view of the lightreceiving camera. Its characteristic optical
performance and applications are describedbelow.

2. Diffuser for TOF System
Figure 2 shows the relationship between a TOF
system and an optical diffuser. The TOF system
consists of a light source and a receiver. In thelight source section, pulsed light emitted from asurface emitting laser (VCSEL) passes through an
optical diffuser consisting of a diffractive opticalelement (DOE) or a microlens array (MLA), andthe area to be measured is irradiated with this
diffused light. In the light receiving section, thelight receiving camera detects the light reflectedfrom the subject and calculates the distance ofthe subject from the delay of the reflected light.

SCIVAX | NANOBIC 7‐7 Shin‐Kawasaki, Saiwai‐ku, Kawasaki City, Kanagawa Prefecture 212‐0032 | +81‐44‐599‐5051

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Optical diffusers control the light distribution
intensity as shown in Figure 3. In order to measure
the distance accurately, the intensity of the lightemitted from the light source, reflected by theobject, and returned to the light receiving sensor of
the camera should be uniformly close to theincident direction, as shown in (a). However, if weconsider that the light is diffusely reflected(Lambert reflection) on a flat surface as shown inFig. 3(a), the larger the camera's viewing angle Θ is,
the weaker the reflected light that reaches thecamera. To compensate for this, an optical diffuser
is used to make the correction. The ideal condition
for sensing, where light is uniformly incident on thelight receiving sensor across the angle Θ, is said tobe the intensity distribution P(Θ) ∝ cos‐7 in the far field, and optical diffusers are designed so that thelight transmitted through them approaches this condition. However, it is difficult to make thedistribution completely proportional to (cosθ)‐7 when the light is irradiated to a very wide viewing
angle, so the camera sensitivity is adjusted by making the distribution proportional to (cosθ)‐n (1<n<7).
(b) is an example of the light distribution intensity transmitted through an optical diffuser designed inthis way, in terms of contour and cross‐sectional intensity distributions

3. Thesis Questions
MLA and DOE, which are conventionally used as optical diffusers, are known to have their own
challenges in their use. DOE, which control the phase distribution of light emitted from a light source bymeans of a pattern of elements, have the advantage of high design flexibility and easy control of theorientation distribution of the emitted light. On the other hand, there is a certain amount of light whose
optical path cannot be completely controlled due to evanescent light seeping at the position where thelocal phase change occurs. This results in the generation of zero‐order light that travels straight fromthe light source without diffraction and stray light that is randomly scattered outside the irradiated areaand becomes background light, reducing the accuracy of measurement and the efficiency of light use.
On the other hand, MLA, which utilize light refraction, do not generate zeroth‐order light or straylight, and provides extremely high light utilization efficiency. However, depending on the positional
relationship between the lens and the light source, interference and other phenomena may prevent
uniform irradiation. In addition, the degree of freedom of the light distribution of the emitted light isinferior to that of DOE, and there is a limit to the irradiation at high angles.

4. Solutions
In order to solve the respective problems ofdiffractive optical (DOE) and refractive optical(MLA), SCIVAX has devised a hybrid opticalsystem of diffractive and refractive systems
and developed a unique optical diffuser,
Platanus®.
Figure 4 shows a comparison of thecharacteristics of conventional MLAs and DOEs
with those of our Platanus®, which effectively
utilizes both diffractive and refractive
properties of light to achieve high light use
efficiency equivalent to or higher than that ofMLAs, and light distribution with a high degreeof freedom and evenness equivalent to that ofDOEs.
SCIVAX | NANOBIC 7‐7 Shin‐Kawasaki, Saiwai‐ku, Kawasaki City, Kanagawa Prefecture 212‐0032 | +81‐44‐599‐50512

5. Products InfoFigure 5 shows some examples of diffuse opticalelements in SCIVAX catalog products. Taking advantage ofPlatanus®'s highly flexible structure in terms of light
distribution intensity, SCIVAX can cover a wide variety ofField Of Illumination (FOI) from narrow angle to theindustry's widest ultra‐wide angle, and provide 3D‐TOF an
optical diffusers optimized for customer applications such asindustrial measurement, mobile, robotic home appliances,and automated driving. In addition to the catalog products,
we can also design and manufacture custom products tomeet your needs.

6. Conclusion
As described above, optical diffusers for 3D‐TOF manufactured with our unique concept andNanoimprint technology are beginning to be adopted in a wide range of products, and SCIVAX isdeveloping a business of providing optical diffusers customized with optimal properties for eachapplication.

SCIVAX | NANOBIC 7‐7 Shin‐Kawasaki, Saiwai‐ku, Kawasaki City, Kanagawa Prefecture 212‐0032 | +81‐44‐599‐5051

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