KC-22AKC-24What is a DPSS laser?The history of airborne particle counters is the history of the evolution of light sources.Takashi MinakamiDevelopment Department, Particle Counter Division. Joined Rion in 1997. As a member of the development team for airborne particle counters, he led the KC-22A project, the first to adopt DPSS lasers. He also played a central role in the development of viable particle counters and established himself as a key figure at Rion in particle counter development.In 2000, we adopted DPSS laser light source technology to make sensors smaller. The first product to emerge from this approach was the KC-22A, which featured a much smaller sensor than conventional products while still achieving a minimum detectable particle size of 0.1 µm and sample flow rate of 2.83 L/min. Adopting this new type of DPSS laser completely resolved the issues associated with gas lasers, including susceptibility to laser beam misalignment and the need for high-voltage power supplies.Released in 2005, the KC-24 achieved a rated sample flow rate of 28.3 L/min, placing it among high-flow-rate models for conventional models and making it ideal for evaluating and managing cleanrooms and other environments that require high cleanliness. It also offers significant improvements in usability, including a CF card for automatically saving measurement data. As with the KC-22A, the light source is a DPSS laser. The high flow rate of this model was achieved by striking a balance between nozzle width and beam diameter.Diode-pumped solid-state (DPSS) lasers are solid-state lasers that use a laser diode (LD) as their pump source. LDs can oscillate efficiently at specific wavelengths. The beams are easily aligned with the absorption bands of the gain media (e.g., Nd:YAG, Nd:YVO₄, Yb:YAG), which results in high energy efficiency and reduced thermal load. This method helps achieve various desirable characteristics like compact dimensions, high efficiency, extended lifetime, high beam quality, and low noise. The DPSS laser system is a modern device that offers solutions to issues associated with conventional technologies while delivering the high reliability and performance required for diverse industrial applications.MirrorParticle detection regionLDLensSolid-state laser crystalIn 2000, Rion completed development of the KC-22A, which adopted a diode-pumped solid-state (DPSS) laser as its light source. This product featured a compact, lightweight design, with long service life, easy maintenance, and high resistance to temperature changes and impact. In the follow-ing year, we released the KC-22B, which offers a minimum detectable particle size of 0.08 µm and sample flow rate of 0.3 L/min. This was the first model to achieve minimum detectable particle sizes of less than 0.1 µm.Then, in 2005, Rion launched the KC-24. This was the first product from Rion to achieve a sample flow rate of 28.3 L/min while measuring particles down to 0.1 µm. To evaluate cleanliness class, you have to determine the number of particles contained per cubic meter. A higher flow rate translates to faster evaluation of volumetric particle count. The instrument incorporates a DPSS laser as its light source, and also incorporates a new technology that features a photodetector unit consisting of three photodiodes. This technology, which took nearly three years to develop, was a major turning point leading to the development of sub-sequent products.The history of airborne particle counter development mirrors the evolution of light sources: from halogen lamps, to He-Ne gas lasers, then semiconductor lasers, and finally DPSS lasers. This progression has enabled increasingly compact, high-performance products.Initially marketed to monitor air pollution, airborne parti-cle counters have become an essential tool in pharmaceutical manufacturing, food production, various other industries, and in hospitals and operating rooms. A significant external factor that accelerated the deployment of airborne particle counters was the proliferation in cleanrooms due to the growth of the semiconductor industry. Airborne particle counters are essential for maintaining and managing clean-rooms at semiconductor plants. Currently, a large portion of Rion’s particle counter product lineup targets applications in these electronics sectors. Airborne particle counters have evolved in tandem with the evolution of light sources. We’re now seeing lasers that draw on new technologies in addition to conventional semiconductor lasers. This suggests we’re on the brink of another inflection point in this evolution.9
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