Device suitable for manufacturing an optical registration carrier, such as a master plate

<td></td><td>Office for Industrial Property in the Netherlands</td><td> © 1013003</td>

<td></td><td colspan="2">© C PATENT²⁰</td>

<td colspan="2">© Patent application: 1013003 © Filed: 08.09.1999</td><td>© Int.CI.⁷G11B7 / 26, G11B7 / 135</td>

<td>© Registered: 12.03.2001</td><td>© Patent holders): ODME International BV in Veldhoven.</td>

<td>@ Date: 12.03.2001</td><td>© Inventor (s): Henricus Theodorus Leonardus Petronella</td>

<td rowspan="2">© Published: 01.05.2001 IE 2001/05</td><td>Stockx in Someren-Eind</td>

<td>© Authorized representative: Ir. JJH Van kan et al. At 5600 AP Eindhoven.</td>

(54) Device suitable for manufacturing an optical record carrier such as, for example, a master plate.

Device suitable for manufacturing an optical record carrier such as, for example, a master plate, which device is provided with a support for the optical record carrier, at least a first and second light source, wherein the wavelengths from the first and second light sources are different and a lens located between the light sources and the support, which is movable relative to the light sources. Between the first light source and the objective lens is a correction lens which is movable together with the objective lens. The focus points of both light sources coincide with different movements of the lens and the correction lens with respect to the light sources.

NL C 1013003

The contents of this patent correspond to the original filed description with claim (s) and any drawings.

Short designation: Device suitable for manufacturing an optical record carrier such as, for example, a master plate.

The invention relates to a device suitable for manufacturing an optical record carrier such as, for example, a master plate, which device is provided with a support for the optical record carrier, at least a first and second light source, the wavelengths originating from the first and second light sources be slightly different and a lens located between the light sources and the support that is movable relative to the light sources.

A master plate is understood to mean a plate by means of which a mold can be made which is used for the production of CDs, DVDs and the like by injection molding. However, it is also possible to use the master plate itself as a mold. In this patent application, optical record carrier is understood to mean both a master disc and a CD or DVD and the like, unless otherwise indicated.

In a device which is known per se and is known per se, a light source with a relatively small wavelength is used to describe the optical record carrier to be manufactured. This light source will be further referred to as a write light source. Another larger wavelength light source is used to focus the write light source. This light source is further referred to as the focus light source.

This has the advantage that the optimum wavelength of the light source can be selected for the required function and respective writing and focusing. Moreover, when writing on an photosensitive lacquer optical record carrier, a wavelength for the focus light source can be selected for which the photosensitive lacquer is insensitive.

The two light sources are imaged via the same lens on the optical recording carrier to be processed, for which purpose the focus points of both light sources must coincide. During focusing, the lens is moved relative to the light sources and the support of the optical record carrier until the focus light source is accurately focused on the optical record carrier. Because the wavelength of the two light sources differ, the focal lengths of the lens for these different wavelengths are also different. When moving the lens in relation to the focus light source, the position relative to the writing light source also changes. As a result of relatively large differences between the wavelengths of the light sources, when the lens is moved to focus the focus light source, the writing light source cannot be kept in focus.

The object of the invention is to provide a device in which light sources of different wavelengths can be focused in a simple manner simultaneously.

This object is achieved with the device according to the invention in that a correction lens is situated between the first light source and the objective lens, which is movable together with the objective lens, wherein the focus points of both light sources coincide substantially at different displacements of the objective lens and the correction lens relative to the light sources.

With the aid of the correction lens, the light source from the first light source is converged or diverged with respect to the light beam from the second light source such that both light beams are focused on the same point after leaving the lens. By moving the lens together with the correction lens, the focus points of both light sources will coincide with each position of the lens relative to the light source.

Preferably, both light sources are lasers, the first light source forming a focus laser and the second light source forming a writing laser. The wavelength of the focus laser is preferably greater than that of the writing laser. The first light source must converge between the correction lens and the lens.

The invention will be further elucidated with reference to the drawings, in which figures 1A and 1B show the focusing according to the prior art, figure 2 shows a device according to the invention, figures 3A and 3B focus with the aid of the Fig. 2 show device shown, Figs. 4, 5 and 6 show different embodiments of the device shown in Fig. 2.

Corresponding parts are provided with the same reference numerals in the figures.

Fig. 1A and 1B show a prior art device 1 comprising one of first and second light sources (not shown), an objective lens 2, a lens 3 arranged parallel to the objective lens and one between the lens 3 and the objective lens 2, plan-parallel plate arranged at an angle of 45 ° 4. A first light source (not shown) is arranged on a side of the lens 3 remote from the lens 2, from which a first substantially parallel light beam 5 is emitted along an optical axis 6 in the direction of the lens 2. The device 1 is further provided with a second light source (not shown) from which a second substantially parallel light beam 7 is emitted along an optical axis 8 extending transversely of the optical axis 6 in the direction of the plane-parallel plate 4. The plane parallel plate 4 is reflective of the second light beam 7, as a result of which the second light beam 7 is deflected by the plane parallel plate 4 in a direction parallel to the optical axis 6. The plane-parallel plate 4 is transparent to the first light beam 5. The second light beam 7 is used to describe an optical record carrier 9 extending parallel to the objective lens 2, such as, for example, a master plate. In order to process the optical record carrier 9 accurately, it is necessary that the second light source 7 be focused on the optical record carrier 9. For focusing, the e first light beam 5 is used . The first light beam 5 has a greater wavelength than the second light beam 7. In order to be able to focus the light beam 5 in the same focus point P on the record carrier 9 as the second light beam 7, the light beam 5 is converged with the aid of the lens 3 into a light beam 10 . The light beam 10 falling on the lens focuses with light beam 11 in the focus point P. The second light beam 7 is bent by the plane-parallel plate 4 into light beam 12 and focused by the objective lens 2 as light beam 13 in point P.

If now the distance between the light sources and the optical record carrier 9 increases by a distance D (see fig. IB), for example as a result of a slight change in the arrangement of a support of the optical record carrier or as a result of differences in thickness of the optical record carrier 9, the objective 2 is moved over a first light source by means of a focusing device known per se. moved such distance d that the converging light beam 10 is focused by the objective lens 2 as light beam 14 on the optical record carrier 9 in point P '. The parallel beam of light 12 from the second light source is focused by the objective 2 at point P "which is at the same distance from the objective 2 as the point P in the situation shown in FIG. 1A. As can be clearly seen from Fig. 1B, the focus points P 'and P ”do not coincide and correct processing of the optical record carrier 9 with the aid of the light beam from the second light source is not possible.

Fig. 2 shows a device 20 according to the invention which differs from the device 1 shown in FIGS. 1A and 1B in that the lens 3 and the objective 2 are rigidly connected to each other by means of a bracket 21. The objective and the correction lens 3 can be moved together with the aid of the bracket 21 in directions indicated by double arrow P1.

The device 20 shown in Fig. 2 furthermore shows a support 22 for the optical record carrier 9 to be processed. The support 22 is rotatable about a center line 23 extending parallel to the optical axis 6 in and opposite to a direction indicated by arrow P2 .

The operation of the device 20 shown in Fig. 2 will be explained in more detail with reference to Figs. 3A and 3B.

The situation shown in Fig. 3A corresponds to the situation shown in Fig. 1A in which both light beams 5, 7 are focused via point 2 in point P.

In the situation shown in Fig. 3B, the optical record carrier 9 is displaced by a distance D. With the aid of a focusing device known per se arranged in the device 20, the light beam 5 is focused on the displaced optical record carrier 9 by moving both the lens 3 and the objective lens 2 at point P ', also by a distance D. Since the objective 2 is displaced by the same distance D as the optical record carrier 9, the parallel light beam 12 of the second light source will also be focused in point P '.

Fig. 4, 5 and 6 show other embodiments of the device 20 according to the invention shown in Fig. 2. In the device 30 shown in Fig. 4, a correction glass 31 is arranged between the correction lens 3 and the plane-parallel location 4. As a result of the plane-parallel plate 4 arranged at an angle to the light beam 5, an astigmatism is introduced, which results in the focus of the light beam 5 in the plane of the drawing of FIG. 4 is located in a location other than in a direction extending transversely thereto. This astigmatism is eliminated with the aid of the correction glass 31.

For the same reason, in the device 40 shown in Fig. 5, in the light beam 5, a device 41 is provided which is provided with two lenses 42, 43 which form a telescope and a prism 44 situated between them.

In order to overcome the astigmatism introduced by the plane-parallel plate 4, use can also be made of the device 50 shown in Fig. 6, which is provided with two parallel-extending lenses 51, 52 and a cylinder lens 53 situated between them.

For example, a red laser with a wavelength of 650 nm can be used as the first light source, while a laser with a wavelength of 257 nm is used as the second light source.

In the device shown in Fig. 2, the correction lens is located between the focus light source and the lens. However, it is also possible to arrange the correction lens 3 between the writing light source and the lens 2.

In the device shown in Fig. 2, the correction lens 3 is rigidly connected to objective 2 by means of a bracket. However, it is also possible to provide the objective 2 and the correction lens 3 with separate displacement devices, whereby the displacement devices are each time actuated such that the objective 2 and the correction lens 3 are displaced by the same distance.