Pentax is a brand name used primarily by Ricoh Imaging Company for cameras, sport optics (including binoculars and rifle scopes), and CCTV optics. The brand is also used by Hoya Corporation for medical products & services, TI Asahi for surveying instruments, and Seiko Optical Products for certain optical lenses.

The company was founded as Asahi Kogaku Goshi Kaisha in November 1919 by Kumao Kajiwara, at a shop in the Toshima suburb of Tokyo, and began producing spectacle lenses (which it still manufactures). In 1938 it changed its name to Asahi Optical Co., Ltd. (旭光学工業株式会社, Asahi Kōgaku Kōgyō Kabushiki-gaisha), and by this time it was also manufacturing camera/cine lenses. In the lead-up to World War II, Asahi Optical devoted much of its time to fulfilling military contracts for optical instruments. At the end of the war Asahi Optical was disbanded by the occupying powers, being allowed to re-form in 1948. The company resumed its pre-war activities, manufacturing binoculars and consumer camera lenses for Konishiroku and Chiyoda Kōgaku Seikō (later Konica and Minolta respectively).

Merger with Hoya

In December 2006, Pentax started the process of merging with Hoya Corporation to form 'Hoya Pentax HD Corporation'. Hoya's primary goal was to strengthen its medical-related business by taking advantage of Pentax's technologies and expertise in the field of endoscopes, intraocular lenses, surgical loupes, biocompatible ceramics, etc. It was speculated that Pentax's camera business could be sold off after the merger. A stock swap was to be completed by October 1, 2007 but the process was called off on April 11, 2007. Pentax president Fumio Urano resigned over the matter, with Takashi Watanuki taking over as president of Pentax. However, despite Watanuki's previously stated opposition to a Hoya merger, on May 16 it was reported that Pentax had accepted "with conditions" a sweetened offer from Hoya, according to a source familiar with the matter. Pentax was under increasing pressure from its major shareholders, Sparx Asset Management in particular, to accept Hoya's bid.

On August 6, 2007, Hoya completed a friendly public tender offer for Pentax and acquired 90.59% of the company. On August 14, 2007, the company became a consolidated subsidiary of Hoya. On October 29, 2007, Hoya and Pentax announced that Pentax would merge with and into Hoya effective on March 31, 2008.Hoya closed the Pentax-owned factory in Tokyo, and moved most of their operations to Southeast Asia. All professional (DA*) and consumer (DA, D-FA) lenses are produced in Vietnam, whereas DSLR cameras are produced in Philippines.

Ricoh Imaging Company

Japanese optical glass-maker Hoya Corporation stated on July 1, 2011, that it would sell its Pentax camera business to copier and printer maker Ricoh, in a deal the Nikkei business daily reported was worth about 10 billion yen ($124.2 million). On July 29, 2011, Hoya transferred its Pentax imaging systems business to a newly established subsidiary called Pentax Imaging Corporation. On October 1, 2011, Ricoh acquired all shares of Pentax Imaging Corp. and renamed the new subsidiary Pentax Ricoh Imaging Company, Ltd. Hoya will continue to use the Pentax brand name for their medical related products such as endoscopes. On August 1, 2013, the company name was changed to Ricoh Imaging Company Ltd.