Optical Scanning Device

An optical scanning device for scanning a first optical record carrier (10′), a second, different, optical record carrier and a third, different, optical record carrier, each record carrier having an information layer, wherein said device includes an optical system (8) including:

• a) a radiation source system (14) having a first radiation source (16), a second radiation source (70) and a third radiation source (72) arranged to emit, respectively, a first radiation beam (11′), a second radiation beam (11″) and a third radiation beam (11′″) having a predetermined first, second and third, different, wavelength, respectively;
• and
• b) an objective lens system (18) arranged to focus said first, second and third radiation beams at said first, second and third optical record carriers, the objective lens system having a common optical path (COP) for said first, second and third radiation beams to travel along,
• wherein said radiation source system is arranged to direct said first radiation beam along a first initial optical path (74), to direct said second radiation beam along a second initial optical path (76), and to direct said third radiation beam along a third initial optical path (78),
• characterized in that the device further includes a redirector (15) for redirecting said second and third radiation beams,
• wherein said second and third initial optical paths, if projected through said optical system without being redirected by said redirector, would include a first off-path displacement (D1) and a second off-path displacement (D2), respectively, with respect to said common optical path at said objective lens system, and
• wherein said redirector includes a diffraction structure having, for said first radiation beam, a first input optical path (44) and a first output optical path (46);
• for said second radiation beam, a second input optical path (48) and a second output optical path (50);
• and for said third radiation beam, a third input optical path (52) and a third output optical path (54),
• wherein said diffraction structure is arranged to redirect said second radiation beam from said second input optical path along said second output optical path and to redirect said third radiation beam from said third input optical path along said third output optical path, said second and third output paths having off-path displacements with respect to said common optical path at said objective lens system which are less than said first and second off-path displacements, so as to improve the colinearity of said second and third output optical paths with respect to said first output optical path.