Laser diodeLaser diodePhotodiodePhotodiodePhoto amplifierPhoto amplifierSignal (voltage) Signal (voltage) YearreleasedMinimummeasurable particlediameter0.05 µm（50 nm）0.04 µm（40 nm）0.03 µm（30 nm）0.02 µm（20 nm）Model2009KS-18F2011KS-18FX2014KS-19F2022KS-20FIllumination lens systemIllumination lens systemScattered light Scattered light collecting systemcollecting systemParticleParticleKE-40B1 controllerKS-20FKZ-31W syringe samplerRecent models of Rion particle countersSchematic illustration of a light scattering sensorParticles passing through an area irradiated by a laser emit scattered light, which is received by the light receiving element and converted into electric signals. The intensity of the electric signal correlates with particle size. The number of times the scattered light is received corresponds to particle count. The sample flow line is configured with a particle sensing cell (flow cell) made of synthetic quartz or sapphire.Example of a measurement system based on the KS-20FThe KS-20F is combined with the KZ-31W syringe sampler and KE-40B1 controller to control particle sensor operations and display measurement data for particle counting in liquids. response to industry demand, Rion launched a series of products capable of measuring even smaller particles. The latest model, the KS-20F, is capable of detecting particles as small as 20 nm.The inside story of the development of the KS-20FThe light scattering method used in particle counters involves irradiating samples with light, after which the scat-tered light emitted by the particles in the sample is captured. The size of the parti-cles is determined based on the intensity of the scattered light. The number of par-ticles is determined by the number of times the scattered light is emitted.Within the range in which particle size is sufficiently smaller than the wave-length of the light, the intensity of scat-tered light is proportional to the sixth power of particle size. Previous models like the KS-19F were able to measure par-ticles down to 30 nm, but a breakthrough was needed to achieve detection levels of 20 nm with the KS-20F. The decrease in measurable particle size by two-thirds, from 30 nm to 20 nm, meant the intensi-ty of scattered light emitted from parti-cles was reduced to one-twelfth. Thus, the KS-20F required a technology to detect much weaker signals.Mitsuaki Saito, the leader of the KS-20F project, remembers the circum-stances: “In 2019, the Development Cen-ter was established by integrating the individual product development organi-zations of each of Rion’s business areas (hearing aids, medical testing instru-ments, sound and vibration measuring instruments, and particle counters) and the R&D Center for advanced technology development. The unique technologies retained by the individual areas were shared, some of which we applied to the weak signal detection technology that had been the central issue in developing the KS-20F. Thus, our combined technol-ogies proved to be a great contribution to making 20 nm particle detection possi-ble.”The team optimized the KS-20F by reviewing all aspects of its design, includ-ing the laser source, focusing lens, photodetector, and electrical circuits to be incorporated into the model. Rion’s KS-20F offered a sophisticated design and outstanding performance that could keep up with semiconductor manufac-turing processes that were growing increasingly elaborate. In Saito’s words, the KS-20F is the “culmination of tech-nologies Rion cultivated over the years” and a testament to the endless efforts made by Rion’s engineers to keep up with the technological advancements and meet industry needs.Rion’s quest continues. The KS-20F will ride the wave of miniaturization and continue to set the foundations for tech-nological innovation in future semicon-ductor processes. We’re merely at the starting line in the race to generate inno-vations that meet the emerging needs of the industry.Mitsuaki SaitoDevelopment Department, Particle Counter Division. After joining Rion in 2008, he worked on the devel-opment of particle counters and the design of both airborne and liquid-borne particle counters. He has been involved with the development of advanced technologies, including foundational research, since around 2016. He has led the KS-20F project since 2020.Flow cellFlow cell15
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