Pentax DA* Lens Patent in Japan & US

The DA* lenses design by Pentax, made in Vietnam ( Pentax factory ) . These DA* lenses' design patent completely belongs PENTAX. (Pentax have optics and mechanism or electronic each patents in the DA*)

Tokina has used the Pentax's optical design. but Tokina lens mechanism design by Tokina.(it is the agreement). Tokina factory in Japan and make Tokina lenses. Tokina had told public news: NO OEM! (2006 PIE in Jappan)
http://dc.watch.impress.co.jp/cda/lens/2006/03/03/3352.html

These DA* lenses' optical-design-patent completely belongs PENTAX. So-called " jointly develops lens " is the Pentax's one commercial practice. (Both sides cooperate merely are restricted in the limited lens models)

PENTAX merely has provided the some optical-design authorization to Tokina. It is cannot guarantee the Tokina lens quality and performance. ( They are cost and material difference. Lens cylinder accuracy and control technology difference. Manufacture craft and equipment difference. Etc)

Pentax has 3 (accuracy and control) patents in 2007. but Pentax lens's cylinder has near 100 Patents in the 2004 Jan - 2007 Aug.
http://picasaweb.google.com/myK10D/LensSCylinderAndControlTechnology

The DA* 16-50SDM or other " jointly develops " lens are like situation. You may visit some website:
http://forum.pentaxfans.net/showthread.php?s=8cba2e17c802c3b559f31acbea79be9a&t=53793

http://picasaweb.google.com/myK10D/DAPentaxSPatents

http://dc.watch.impress.co.jp/cda/lens/2006/03/03/3352.html

http://lh6.google.com/myK10D/Rtan2nyB_eI/AAAAAAAAALs/poeMBuXRnR4/s800/da50-135sdmJP.jpg

http://lh6.google.com/myK10D/RtanonyB_bI/AAAAAAAAALU/OFUQdVorK94/s800/pdfdoc201.jpg

http://lh5.google.com/myK10D/RtUtnnyB_JI/AAAAAAAAAHQ/yi9k4HR1W7Y/s800/da16-50sdm.jpg

http://lh6.google.com/myK10D/RtanonyB_dI/AAAAAAAAALk/nGPZji_-URM/s800/same_optics_sys.jpg

http://lh6.google.com/myK10D/RtanonyB_cI/AAAAAAAAALc/iOD-1jeiMtE/s800/nz-da50_135f28ed_alsdm.jpg