Rigaku Holdings, the Tokyo-listed precision-instrument maker, has a new top shareholder. On August 10, 2026, Atom Investment, L.P. transferred 61,123,436 common shares to Onto Innovation Inc., the U.S. semiconductor wafer-inspection and process-control equipment supplier. The transfer leaves Onto Innovation with a 27.00% voting-rights stake, making it Rigaku's largest shareholder and, under Japanese disclosure rules, an "other affiliated company".
| Shareholder | Stake before | Stake after |
|---|---|---|
| Onto Innovation Inc. | — | 27.00% |
| Atom Investment, L.P. (Carlyle-linked) | 27.29% | 0.29% |
| Columbia Management Investment Advisers, LLC | 9.38% | 10.53% |
Atom Investment, the Cayman Islands limited partnership, saw its stake fall from 27.29% to 0.29%, a drop from 61,774,100 shares to 650,664 shares. It did not leave the shareholder register entirely: it still holds those 650,664 shares after the transfer. The Carlyle Group holds and manages all of Atom Investment's interests, and one Rigaku director is an officer or employee of Carlyle Japan LLC, a Carlyle Group affiliate, the company said.
The transfer completes a deal first flagged in April and May 2026: an April 21 capital-and-business alliance announcement and a May 22 secondary offering that let Atom sell down its position, with a greenshoe option subsequently exercised. The two companies are jointly developing hybrid metrology solutions for semiconductor process control, according to the disclosure. Onto Innovation, formed in 2019 from the merger of Nanometrics and Rudolph Technologies, reported revenue of $1,005.3mn and net income of $136.8mn for its most recent fiscal year, up from $815.9mn in revenue and $121.2mn in net income two years earlier. Rigaku said the shareholder change will have only a minor effect on its own earnings.
A separate filing the same week flagged a different kind of ownership shift. Columbia Management Investment Advisers, LLC, the U.S. asset manager, increased its Rigaku voting-rights stake from 212,347 units (9.38%) as of June 30 to 238,287 units (10.53%) as of July 31, 2026, crossing the 10% line that triggers mandatory major-shareholder disclosure under Japan's Financial Instruments and Exchange Act. Rigaku based the filing on a large-shareholding amendment report Columbia submitted on August 7 and said it has not independently verified the beneficial ownership figures.
Taken together, the two disclosures show Rigaku's ownership base reshaping on two fronts at once: a strategic industrial partner taking the top seat at the table, and an institutional asset manager crossing into major-shareholder territory. As of June 30, 2026, Rigaku had 226,516,100 issued common shares and capital of roughly ¥1.2bn.