Optical: systems and elements – Lens – With support
Reexamination Certificate
1999-11-12
2001-04-24
Epps, Georgia (Department: 2873)
Optical: systems and elements
Lens
With support
C359S822000
Reexamination Certificate
active
06222687
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an object lens supporting unit for supporting an object lens, in particular, to the unit capable of compensating for inclination of the object lens when an optical and electrical apparatus provided with the object lens is manufactured.
Generally, the object lens supporting unit is applied in an optical disk drive for reading/writing data from/to an optical recording medium of disk type by irradiating laser beam to the medium and optically sensing reflected laser beam from the medium/by irradiating laser beam to the medium. The object lens supporting unit is driven in such direction that traverse innumerable tracks formed on the optical medium and is stopped on a target track. Thus, the unit carried out to irradiate the track and to read/write data from/to the track.
Conventionally, to compensate for the inclination of the object lens, various remedies have been contrived. Basically, to compensate for the inclination of the object lens, it requires a mechanism for adjusting inclination of the object lens and mechanisms for compensating for distance deviation of the object lens in focusing and tracking directions caused by the adjusting of inclination of the objects lens. Herein, the focusing direction is a direction vertical to a recording surface on a disc type-recording medium, while the tracking direction is a direction transverse recording tracks formed on the recording medium. Therefore, the conventional structure for compensating for the inclination fo the object lens is complex in structure.
To settle matter mentioned above, an object lens supporting unit related to this invention is disclosed in Japanese Patent Unexamined Publication (A) No. 223953/1984.
The unit uses a concave pedestal for adjusting the inclination of the object lens in an object lens drive. The unit comprises a supporting base for supporting the object lens and a head case for supporting the supporting thereon. The supporting base is provided with convex and spherical parts on a bottom surface thereof. The head case is provided with the concave pedestal on an upper surface thereof. The concave pedestal has a concave surface along a spherical surface of an imaginary or a supposed sphere drawn around a principal point of the object lens as central point. In other words, the concave surface has a supposed central point which positionally coincides with the principal point of the object lens. Since the supporting base is supported on the head case through only the convex and spherical parts, the convex and spherical parts can be slid on the spherical surface of the concave pedestal. Therefore, the entire supporting base can be tilted in every direction around the principal point of the object lens. This structure has an advantage that the principal point of the object lens is almost invariable in position. It is therefore unnecessary to compensate for distance deviation of the object lens in focusing and tracking directions after the object lens was adjusted for the inclination thereof.
However, it is difficult for this structure to reduce in thickness because the head case requires a relatively large thickness in order to secure a space for forming the spherical surface of the concave pedestal. If optical system of this structure is reduced in height with the structure maintained basically, it becomes difficult to put the supposed central point of the concave pedestal onto the principal point of the object lens. Namely, if it is required to reduce a height size as a first priority in the structure, the object lens deviates in the focusing and/or the tracking directions when it was adjusted the inclination. In the event, the above-mentioned advantage is spoiled. As described above, the related technique is practically unsuitable to reduce in height and to apply into apparatuses such as portable or mobile computers requested to reduce in height.
SUMMARY OF THE INVENTION
It is an object of this invention to solute disadvantages mentioned above and to therefore provide an object lens supporting unit which compensates for inclination of an object lens capable of reducing in height.
The other object, features, and advantages of this invention will become clear as the description proceeds.
This invention is directed to an object lens supporting unit used for supporting an object lens for converging laser beam irradiated from a laser source in a constant direction, which comprises a supporting frame for supporting the object lens, a base member for mounting the supporting frame thereon, an adjusting mechanism for adjusting the supporting frame with the supporting frame universally tilted to the base member, the adjusting mechanism comprising a pedestal portion formed on a top surface of the base member, a plurality of protrudent portions protruded from a bottom surface of the supporting frame, in contact with the pedestal portion, and capable of freely sliding along the pedestal portion, and holding means for limiting the protrudent portions within a predetermined sliding range. The pedestal portion has a curved surface formed along a surface of a supposed revolution body. The supposed revolution body is formed by rotation of an ellipse around a minor axis thereof. The supposed revolution body is further inscribed to a supposed spherical surface formed around a central point. The central point is served by a principal point of the object lens supported by the supporting frame. The protrudent portions are arranged so as to be in contact with the curved surface at positions which correspond to an area of the supposed revolution body inscribed to the supposed spherical surface.
This invention is further directed to an object lens supporting unit used for supporting an object lens for converging laser beam irradiated from a laser source in a constant direction, which comprises a supporting frame for supporting the object lens, a base member for mounting the supporting frame thereon, an adjusting mechanism for adjusting the supporting frame with the supporting frame universally tilted to the base member, the adjusting mechanism comprising a pedestal portion formed on a top surface of the base member, a first and a second protrudent portions protruded from a bottom surface of the supporting frame, in contact with the pedestal portion, and capable of freely sliding along the pedestal portion, the first and the second protrudent portions being equal in size to each other, and holding means for limiting the motion of each of the first protrudent portion and the second protrudent portions within a predetermined sliding range. The pedestal portion has a curved surface including a first and a second curved surfaces. The first surface is formed along a part of a first supposed revolution body. The second curved surface is formed along a part of a second supposed revolution body. The first supposed revolution body is formed by rotation of a first partial supposed ellipse around an optical axis through which the laser beam is passed. The second supposed revolution body is formed by rotation of a second partial supposed ellipse around the optical axis. The first partial supposed ellipse is a part formed by division of a supposed ellipse along the optical axis. The second partial supposed ellipse is the remaining part formed by the division of the supposed ellipse along the optical axis. The supposed ellipse is in contact with a first supposed sectional circle at a first intersection point where the first supposed sectional circle and a first supposed circumscribed circle are intersected with each other. The supposed ellipse is further in contact with a second supposed sectional circle at a second intersection point where the second supposed sectional circle and a second supposed circumscribed circle are intersected with each other. The first supposed sectional circle is defined by section of a first supposed spherical surface along a plane which includes the principal point and the optical axis. The first supposed spherical surface is circumscribed to the first protrudent p
Epps Georgia
McGinn & Gibb PLLC
NEC Corporation
Seyrafi Sayeed
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