Yachiyo Kōgaku Kōgyōsho (八千代光学工業所) was a Japanese optical company. Its address in 1943 was Tokyo, Takinogawa-ku Kaminakazato 510 (東京都滝野川区上中里510). It is listed in the government inquiry compiled in April 1943 as the maker of the three-element Zeitax 75/3.5 and 75/4.5 lenses of the Semi Condor and Semi Zeitax.
- "Kokusan shashinki no genjōchōsa" (国産写真機ノ現状調査, Inquiry into Japanese cameras), listing Japanese camera production as of April 1943. Reproduced in Supuringu kamera de ikou: Zen 69 kishu no shōkai to tsukaikata (スプリングカメラでいこう: 全69機種の紹介と使い方, Let's try spring cameras: Presentation and use of 69 machines). Tokyo: Shashinkogyo Syuppan-sha, 2004. ISBN 4-87956-072-3. Pp.180–7.