Patent Application
20070169139
The invention relates to an optical scanning device for an appliance for reading and/or writing to optical recording media, in which the scanning device reads or stores information or data in one or more tracks on a recording medium. In this case, the recording medium may be a compact disc, known as a CD, a digital versatile disc, known as a DVD, a CD-ROM or DVD-ROM or a rewritable CD or DVD or else another recording medium.
Appliances for recording or reproducing information or data in one or more tracks on a recording medium which are provided with a scanning device, also called a “pick-up”, for reading and/or recording the information are known. Normally, the respective scanning device has an optical housing, which can be moved obliquely or at right angles to the respective recording track on the recording medium in the manner of a carriage and which can move at high speed and with a high level of positioning accuracy when driven by an electric motor, combined with a short access time to different locations on the recording medium, and has an optical scanning unit, also called actuator, which emits a laser beam onto the recording medium and receives the beam reflected therefrom. The scanning unit, which has a focusing lens, has a baseplate mounted so that it is adjustable on the housing, which can be moved on guide rods, in order to be able to orient the focusing lens according to the optical path. This is necessary because the scanning unit has a series of optical components for directing and orienting the laser beam on the path to the respective recording medium and from the latter to a detector which, like the mechanical parts which retain and connect them, have specific production and assembly tolerances.
So that the respective recording medium can be illuminated at the correct position and its data can be transmitted to an optical detector precisely, provision is made for the focusing lens to be aligned during assembly of the scanning device by tilting the scanning unit, as described in DE 694 15 762 T2 and DE 698 01 021 T2, for example.
In the known scanning devices, the scanning unit with the focusing lens is tilted by means of the baseplate (support), which has at least one slide face resting on at least one support face integrally formed on the optical housing, the faces being in spherical or cylindrical form, in particular. To this end, said documents disclose the practice of tilting the scanning unit together with the baseplate using a spring means and at least one adjusting screw, which are supported on the housing, the spring means being arranged on the side of the (virtual) tilt axis and of the scanning unit which is remote from the at least one adjusting screw, in order to change the position of the focusing lens in this way.
In this case, the at least one adjusting screw is arranged at an opening in the housing so as to be displaceable transversely with respect to the screw axis, has a screw head bearing against the edge of the opening on the side of the housing which is remote from the baseplate, and its threaded shaft engages without play into a threaded hole with a plurality of threads which is made in the baseplate. When the at least one adjusting screw is turned, the baseplate with the threaded hole is tilted about a virtual axis, the spring force having a more or less pronounced action depending on the direction of tilt, and friction arising between the screw head and the housing which inhibits the sliding movement from the screw head on the housing and prevents smooth rotation of the adjusting screw. The alternation between adhesive and sliding friction on the screw head results in bucking (“stick-slip effect”), which makes precise adjustment more difficult. The invention is intended to provide a remedy for this.
A problem to be solved by the invention is to improve the mounting arrangement for the scanning unit on an optical housing in an optical scanning device for an appliance for reading and/or writing to optical recording.
According to the invention, in an optical scanning apparatus for an appliance for reading and/or writing to optical recording media, having a moveably arranged optical housing with slide faces for applying a support for an adjustable scanning head, where the support is mounted on and tensioned against the slide faces by means of at least one adjusting screw supported on the housing and by means of at least one spring means and can have the scanning head adjusted about a virtual axis when there is a screw movement from the adjusting screw, the adjusting screw acts on the support at a variable angle and changes its angle with respect to said support in the event of a screw movement to prompt an adjusting movement from said support. In known fashion, mating slide faces are arranged on the support. In similarly known fashion, the adjusting screw at an interval from the mating slide faces and the spring means likewise act on the support on the side which is remote from the adjusting screw. In this case, the screw head of the adjusting screw bears against that edge of an opening made in the housing which is situated transversely with respect to its axis, penetrates said opening with its threaded shaft with play in the direction of the support, and can move in the opening transversely with respect to its axis. This adjusting screw arrangement advantageously results in simpler adjustment of the support with the scanning head, since said adjustment takes place gently and smoothly. This in turn is associated with shorter process and adjustment times.
When there is a screw movement from the adjusting screw, the support with the scanning head is moved on the slide faces, which are preferably in spherical or cylinder-segment form, and is tilted about a virtual axis. In this case, the angle of inclination of the support changes with respect to the optical housing. As a result of the adjusting screw being arranged on the support at a variable angle, the screw head at the edge of the opening is no longer moved on the optical housing, but rather is just tilted about a line or a point, in each case depending on the design of the screw head, which results in a gentle and smooth adjusting movement.
The variability of the angle of the adjusting screw acting on the support is easily achieved by virtue of a threaded hole with just one supporting thread being made in said support for the adjusting screw. When said adjusting screw engages in this thread to produce a connection, the adjusting screw is supported on it in the manner of an articulation, the strength of the connection to this one thread being approximately 60% of the strength of a threaded element with a plurality of threads. In this case, the one thread may also still be interrupted and may just comprise two thread segments arranged opposite, with the connecting line between these thread segments running essentially parallel to the virtual axis of the support and simultaneously being the axis of inclination for the adjusting screw.
To increase the interval between the screw head and the axis of inclination of the adjusting screw on the support, the thread or the thread segments is/are made in the threaded hole on the side which is remote from the housing. This keeps down the size of the adjusting screw's angle of inclination which is made possible, and linked to this also the diameter of the opening for the screw, which in turn means that the screw head may advantageously end up being smaller.
To improve the fine adjustment, the adjusting screw should be at as great as possible an interval from the virtual axis. This greater interval is achieved by providing the support with a tongue which points away from it and on which the threaded hole is made. In known fashion, the optical housing is advantageously at a lower level in the region of the tongue, in order to increase the maximum adjustment angle of the support relative to the optical housing.
The support extends parallel to the virtual axis between bearing brackets which are formed on the housing and whose free ends have the slide faces on them. In this case, the bearing brackets are simultaneously used as guide means for the support when there is an adjusting movement about the virtual axis.
The arrangement and/or design of the slide faces on the housing is preferably concave relative to the support, so that the latter's mating slide faces which correspond to these slide faces are held in the manner of a tub. In this case, the slide faces may have a spherical or cylindrical shape, in particular. Advantageously, these and the mating slide faces, which bear against them using the matching shapes, are in cylindrical form, however, in order to permit an adjusting movement from the support in just one stipulated direction. As an alternative to the cylindrical design of the slide faces on the housing, a planar prismatic design is also possible, with the cylindrical mating slide faces bearing linearly against these in a manner parallel to the virtual axis.
The spring means is a pretensioned tension spring which simply needs to be arranged between the support and the housing and which acts on a tongue integrally formed on the support. This tongue and hence the tension spring are advantageously arranged on the support diagonally with respect to the adjusting screw on the other side, because as a result the guidance of said support between the bearing brackets prevents twisting during an adjusting movement and the arrangement requires just one adjusting screw.
The invention is explained below with reference to an exemplary embodiment. In the associated drawings:
a to c: show a respective section Z-Z through a known scanning apparatus with various settings for the support on the optical housing and with an adjusting screw,
a and b: show the position of the adjusting screw in the settings shown in
a to c: show a respective section Z-Z through an inventive scanning apparatus with various settings for the support on the optical housing and also with an adjusting screw,
a and b: show the position of the adjusting screw in the settings shown in
a to c show a respective section Z-Z through a known scanning apparatus with various settings for the support on the optical housing and also with an adjusting screw 8. The figure shows the mounting of the support 7 and the arrangement of the adjusting screw 8. The screw head 15 of the latter bears against the lower edge of an opening 16, and its threaded shaft 17 penetrates said opening, the diameter of the opening being greater than the diameter of the threaded shaft, such that the screw head 15 covers the edge of the opening 16 on all sides even when it moves within the scope of the given play. In this case, the threaded hole 12 has a thread 18 over its entire length. On account of this thread which comprises a plurality of windings, the adjusting screw 8, whose screw head 15 bears against the housing 1 under pretensioning, is connected rigidly to the support 7.
To correct the position of the focusing lens, the support 7 with the scanning head 4 is rotated about a virtual axis A so as to slide on the slide faces 9, which changes its angle relative to the housing 1. This correction is made by turning the adjusting screw 8. Depending on the direction of correction, the adjusting screw 8 is rotated either clockwise or anticlockwise. In the first case the support 7 is rotated anticlockwise about the virtual axis A and arrives at a position as shown in
a and 5b show the two screw positions shown in
a to 6c show the mounting of the support 7 and the arrangement of the adjusting screw 8 for a scanning apparatus based on the invention. In this case, just one supporting thread turn 18 is made in the threaded hole 12 and, in this context, is arranged on the scanning head side, that is to say on the side which is remote from the housing 1, in the threaded hole and hence on the tongue 11. This thread design with just one thread turn 18 allows the adjusting screw 8, whose screw head 15 bears against the housing 1 under pretensioning, to make a tilting movement on the thread turn 18 without the screw head 15 sliding with friction on the housing 1. Instead of such a sliding movement, the screw head 15 is merely twisted.
In this case too, the position of the focusing lens is corrected by turning the adjusting screw 8. The movements of the adjusting screw 8 which are enforced in each case are made possible without friction and smoothly as a result of its variation of angle in the threaded hole 12, as described above.
a and b show the two screw positions shown in
