1.  Field of the Invention
The present invention relates to a disk drive unit adapted to record and/or reproduce information in and/or from a disk-shaped recording medium. 
2.  Description of the Related Art
There have been provided disk drive units for recording and reproducing information in and from optical disks, such as CDs and DVDs, and also DVRs or blue ray disks for recording information with higher densities than those of the CDs and DVDs (refer to, for example, Japanese Unexamined Patent Application Publication No.  2003-67920). 
The wavelength of an optical beam used for recording and reproducing in and from CDs and DVDs is, for example, 650 nm or 680 nm, while the wavelength of an optical beam used for recording and reproducing in and from DVRs is shorter, e.g., 405 nm.  For this reason, the aforesaid disk drive unit is equipped with a first pickup having a light source of the wavelength of the CDs and DVDs, and a second pickup having a light source of the wavelength for the DVRs. 
Because of the difference in wavelength mentioned above, the sizes of light spots formed on a DVR are significantly smaller than those formed on a CD or DVD, so that DVRs are more susceptible to dust than CDs or DVDs are. 
A DVR is, hence, provided in the form of a disk cartridge having an optical disk housed in a cartridge case to protect the optical disk from dust. 
However, in the disk drive unit described above, dust on a CD or DVD, or dust on the disk cartridge of a DVR inevitably is scattered in the disk drive unit. 
If dust adheres to an object lens of the second pickup, then the quantity of light reaching an optical disk reduces, and recording or reproducing failure may result, or excessive drive current may be supplied to the light source of the second pickup to compensate for the reduced quantity of light, causing deterioration of the light source.