HK1032840A - Device suitable for manufacturing an optical registration carrier, such as a master plate - Google Patents

Description

Apparatus suitable for manufacturing optical registration carriers such as motherboards

The invention relates to a device suitable for manufacturing an optical registration carrier, such as a motherboard, comprising a support for said optical registration carrier, at least a first and a second light source, and an objective lens, wherein the wavelengths of the light from the first and second light sources are different from each other, and wherein said objective lens is located between said light sources and said support, and is movable relative to said light sources.

The term "master plate" refers to a plate for making a mold, where the mold can be used to make CDs, DVDs, etc. by an injection molding process. However, the main plate itself may be used as the mold. The term optical registration carrier as used in this patent application refers to a main board as well as a CD or DVD etc., unless otherwise indicated.

In the device referred to in the introduction, which is known per se, the optical registration carrier to be manufactured is written with a light source of relatively short wavelength. This light source will be referred to as a writing light source hereinafter. Another light source with a longer wavelength is used for the focused writing light source. This light source will be referred to as a focused light source in the following.

The above structure has the advantage that the optimum wavelength of the light source can be selected to meet the desired writing or focusing function. In addition, when writing on an optical registration carrier containing a photosensitive lacquer, a wavelength to which the photosensitive lacquer is insensitive can be selected for the focused light source.

The two light sources emit their light beams through the same objective lens to the optical registration carrier to be processed, and the focal points of the two light sources need to be overlapped at the end part of the objective lens. During focusing, the objective lens is moved relative to the light source and the support of the optical registration carrier until the focused light source is accurately focused onto the optical registration carrier. Since the two light sources have different wavelengths, the objective lens also has different focal lengths for the different wavelengths. When the objective lens moves relative to the focusing light source, its position relative to the writing light source also changes. As a result, if the wavelength difference of the light sources is relatively large, the writing light source cannot maintain focus when the objective lens is moving for focusing the focusing light source.

It is an object of the invention to provide a device which can simultaneously focus light sources having different wavelengths in a simple manner.

This object is achieved with the device according to the invention in that a correction lens is placed between the first light source and the objective lens, which correction lens is movable together with the objective lens. The focal points of the two light sources at least substantially coincide when the objective lens and the correction lens are variously moved with respect to the light sources.

The light beam from the first light source is made to converge or diverge with respect to the light beam from the second light source in a manner using a correction lens so that the two light beams are focused on the same point after leaving the objective lens. By moving the objective lens together with the correction lens, the focal points of the two light sources will coincide at each position of the objective lens relative to the light sources.

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

The invention will now be described in more detail with reference to the accompanying drawings, in which:

fig. 1A and 1B illustrate a focusing operation performed according to the related art;

FIG. 2 shows an apparatus according to the invention;

FIGS. 3A and 3B illustrate a focusing operation performed with the apparatus shown in FIG. 2; and

fig. 4, 5 and 6 show different embodiments of the device of fig. 2.

In the drawings, the same reference numerals are used to designate the same components corresponding to each other.

Fig. 1A and 1B show a device 1 according to the prior art, which comprises a first and a second light source (not shown), an objective lens 2, a lens 3 placed parallel to the objective lens, and a plane parallel plate 4 placed at an angle of 45 ° between the lens 3 and the objective lens 2. A first light source (not shown) is located on the side of the lens 3 remote from the objective lens 2, which light source directs a substantially parallel first light beam 5 along an optical axis 6 towards the objective lens 2. The apparatus 1 further comprises a second light source (not shown) which directs a second substantially parallel light beam 7 towards the plane parallel plate 4 along an optical axis 8 extending transversely to the optical axis 6. The plane parallel plate 4 reflects the second light beam 7, as a result of which the second light beam 7 is deflected by the plane parallel plate 4 into 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 for writing an optical registration carrier 9, such as a main plate, while the optical registration carrier 9 extends parallel to the objective lens 2. For accurate processing of the optical registration carrier the second light beam 7 has to be focused on the optical registration carrier 9. The focusing may be done with the help of the first light beam 5. The wavelength of the first light beam 5 is larger than the wavelength of the second light beam 7. In order to be able to focus the light beam 5 to the same focal point as the second light beam 7, the light beam 5 is converged by the lens 3 into a light beam 10. The light beam 10 impinging on the objective lens is itself focused with the light beam 11 in the focal point P. The plane parallel plate 4 deflects the second light beam 7 into a light beam 12 and the objective lens 2 focuses it as light beam 13 on the point P.

If the distance between the light source and the optical registration carrier 9 increases by a distance D (see fig. 1B) due to a slight variation of the position of the support of the optical registration carrier or due to a difference in the thickness of the optical registration carrier 9, the objective lens 2 is moved by a distance D with respect to the first light source by known focusing means such that the objective lens 2 focuses the converging light beam 10 as a light beam 14 on a point P' of the optical registration carrier 9. The objective lens 2 focuses the parallel light beam 12 from the second light source on a point P "which is at the same distance from the objective lens 2 as the point P is from the objective lens 2 in the case shown in fig. 1A. As is clear from fig. 1B, the focal points P' and P "do not coincide and it is not possible to correctly process the optical registration carrier 9 with a light beam from the second light source.

Fig. 2 shows a device 20 according to the invention. The apparatus 20 differs from the apparatus 1 shown in fig. 1A and 1B in that it has a holder 21 rigidly interconnecting the lens 3 and the objective lens 2. The carriage 21 moves the objective lens and the correction lens 3 together in the direction indicated by the double arrow P1.

The apparatus 20 shown in fig. 2 also comprises a support 22 for the optical registration carrier 9 to be processed. The support member 22 is rotatable about an axis 23 extending parallel to the optical axis 6 in the direction indicated by the arrow P2 or in the opposite direction thereto.

The operation of the apparatus 20 shown in fig. 2 will now be described with reference to fig. 3A and 3B.

The situation shown in fig. 3A is similar to the situation shown in fig. 1A, the two beams 5 and 7 being focused on the point P by the objective lens 2.

In the situation shown in fig. 3B, the optical registration carrier has been moved by a distance D. By moving the lens 3 and the objective lens 2 by the same distance D, the beam 5 is focused to a point P' on the moved optical registration carrier 9 by known focusing means, which are located in the device 20. Since the objective lens 2 is moved the same distance D as the optical registration carrier 9, the parallel light beam 12 from the second light source is also focused at point P'.

Figures 4, 5 and 6 show further embodiments of the inventive device 20 shown in figure 2. In the apparatus 30 shown in fig. 4, a correcting glass 31 is placed between the correcting lens 3 and the plane parallel plate 4. Astigmatism is caused by the presence of the plane parallel plate 4, and the plane parallel plate 4 is at an angle to the light beam 5, resulting in the focal point of the light beam 5 being at another point in the plane of fig. 4, which is not in the transverse direction. This astigmatism can be eliminated with a correction glass 31.

For the same reason, in the apparatus 40 shown in fig. 5, a device 41 is arranged in the path of the beam 5, wherein the device 41 comprises two lenses 42 and 43, which form a telescope, and a prism 44, which is located between the two lenses.

Astigmatism caused by the plane-parallel plate 4 can also be eliminated with an apparatus 50 as shown in fig. 6, wherein the apparatus 50 comprises two parallel lenses 51 and 52 and a cylindrical lens 53 located in between.

For example, the first light source may be a red laser with a wavelength of 650 nm, and the second light source may be a laser with a wavelength of 257 nm.

In the apparatus shown in fig. 2, a correction lens is placed between the focusing light source and the objective lens. But it is also possible to place the correction lens 3 between the writing light source and the objective lens 2.

In the apparatus shown in fig. 2, the correction lens is rigidly connected to the objective lens 2 by a holder. It is also possible to adjust the objective lens 2 and the correction lens 3 with separate operating mechanisms and to control the operating mechanisms such that the objective lens 2 and the correction lens move the same distance.

Claims (14)

1. An apparatus adapted for manufacturing an optical registration carrier, such as a motherboard, the apparatus comprising a support for the optical registration carrier; at least first and second light sources having wavelengths of light different from each other; and an objective lens, which is arranged between the light source and the support and is movable relative to the light source, characterized in that a correction lens is arranged between the first light source and the objective lens, which correction lens is movable together with the objective lens, the focal points of the two light sources at least substantially coinciding during various movements of the objective lens and the correction lens relative to the light source.

2. The apparatus of claim 1, wherein the first light source is directed as a substantially parallel beam toward the correction lens and the second light source is directed as a substantially parallel beam toward the objective lens.

3. Device as claimed in any of the foregoing claims, characterized in that the objective lens and the correction lens are mechanically interconnected.

4. The apparatus of claim 1 or 2, wherein the objective lens and the correction lens are each movable by the same distance.

5. Device as claimed in any of the foregoing claims, characterized in that an additional plate is arranged between the correction lens and the objective lens, through which additional plate the light beam from the first light source passes, while the light beam from the second light source is deflected simultaneously in the direction of the objective lens.

6. The apparatus of claim 5, wherein the additional plate is at an angle relative to the beam of light from the first light source.

7. A device as claimed in claim 5 or 6, characterized in that an astigmatism correction element is placed between the additional plate and the first light source, the astigmatism generated by the additional plate and the correction element substantially cancelling each other.

8. The apparatus of claim 7, wherein said astigmatism correction element comprises a correction plate, said correction plate being at an angle relative to said additional plate.

9. The apparatus of claim 7 or 8, wherein the corrective element comprises an astigmatic cylindrical lens.

10. An apparatus according to any of claims 7-9, wherein the correction element comprises a prism.

11. Apparatus according to any preceding claim, wherein at least one of the light sources is a laser.

12. The apparatus of claim 11, wherein the laser has a wavelength of less than 400 nanometers.

13. A device as claimed in any one of the preceding claims, characterized in that it is not possible to write to the optical registration carrier with the first light source, but it is possible to write to the optical registration carrier with the second light source.

14. A device adapted to focus a second light source with a first light source, the wavelength of the light beam from said first light source being different from the wavelength of the light beam from said second light source, a common objective lens being placed in front of said light sources, the objective lens being movable with respect to said light sources, characterized in that a correction lens is placed between the first light source and the objective lens, the correction lens being movable together with the objective lens, and the focal points of the two light sources at least substantially coincide when the objective lens and the correction lens are moved variously with respect to the light sources.