To solve the problem that reduction in optical coupling loss generated in a spatial optical system including a single lens is not sufficient, a lens excellent in performance is difficult to manufacture and expensive, adjustment work when an optical signal processor is manufactured is complex, a manufacturing cost is high, and further, it is necessary to secure a return loss in an optical system and reduce the amount of cross-talk, in the conventional optical signal processor.
The lens configuration of this invention is found by using the refractive powers (D1, D2, D3 and D4) of respective lens surfaces as a parameter, by focusing on reduction in tangential astigmatism. It is found that in not the single lens of the conventional technique, but two-group two-lens, when the focal length of two lenses is near (D1f+D2fD3f+D4f0.5) and a second condenser lens is a plano-convex lens whose convex side faces a first condenser lens side (D3f0.5), the optical coupling loss of wavelength dependency is remarkably small.
SUZUKI MASAYA
MINO SHINJI
ISHII MOTOHAYA
EBISAWA FUMIHIRO
NTT ELECTRONICS CORP
| JP2004239991A | 2004-08-26 | |||
| JP2002250828A | 2002-09-06 | |||
| JPH0875948A | 1996-03-22 |
Kazuo Abe
Next Patent: IMAGE FORMING APPARATUS AND EXPOSURE APPARATUS