RU2429550C2 - Optical head to write on optical disk and/or reading off from optical disk phase-only synthetic hologram to be used in said optical head - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: optical head comprises encased laser source, diffraction lattice to generate diffraction beam of rays of zero and ±1^st order, light splitting cure, phase-only synthetic hologram with positive optical force, collimated beam polarisation plate, lens of positive optical force, as well as astigmatic lens and photo detector to detect light beam reflected from disk. Lens is arranged ahead of optical disk to displace there along. Phase-only synthetic hologram may displace along optical axis and generate zero and ±1^st order collimated beams at outlet and reduce lengthwise chromatic aberration of zero-order beams originating in data write/read process. Phase-only synthetic hologram comprises collimator lens with first flat and second diffraction surfaces formed in compliance with phase factor defined by formula specified in invention claim.

EFFECT: higher accuracy and reliability of writing/reading.

9 cl, 8 dwg

Description

Technical field

The invention relates to an optical head capable of recording and / or reproducing information from optical discs or to optical discs, in particular so-called Blu-ray discs (BD), hereinafter referred to as BD discs.

State of the art

There are currently several basic standards for 12 cm optical discs. The standard for compact discs (CD) was established in 1982, the recording capacity of these discs is about 700 MB, and they are used mainly for audio recording. A standard for universal digital discs (DVDs) was established in 1996. A DVD-ROM allows you to save movies in standard resolution (720 × 576 pixels) for 2 hours 50 minutes with MPEG-2 compression, while the capacity for these discs was determined 4.7 gigabytes. To record the films of the new television standard HDTV (High Definition Television), new recording standards with a large amount of memory were required. Thus, two competing standards were developed: an HD-DVD disc and a Blu-ray disc (VD). To increase the amount of recorded information, it is necessary to reduce the diameter of the diffraction-limited light spot of radiation focused on the disk, which is proportional to λ / NA, where λ is the wavelength of the laser diode and NA is the numerical aperture of the lens. To implement an optical memory (storage device) of a large amount of memory with a high recording density, it is very important to reduce the wavelength of the radiation source and increase the numerical aperture (NA) of the optical read head. It should be noted that the recording capacity for a single-layer HD-DVD disc is 15 Gigabytes, and for Blu-ray discs - 23.3; 25 or 27 gigabytes. Thus, Blu-ray discs are the next generation of optical discs with a large amount of memory with a high recording density.

When recording information on an optical disk and reproducing information from an optical disk, optical drives are used, which include an optical reader (optical head) that moves across the disk-shaped information carrier.

However, for a clearer understanding of the problems that arise during the operation of optical read heads for Blu-ray discs, some features of the use of disks of the specified standard should be disclosed.

For reliable reading and writing of information, the optical system of the optical head must form a scattering spot on the information layer of the disk, the dimensions of which are determined by the BD format, while the wave aberration of the main beam should not exceed 0.033λ, where λ is the wavelength of the diode radiation. Considering that the optical head of the BD format has a high numerical aperture NA = 0.85, the aberration correction of the system should be very high. Moreover, for mass production, the most important is the simplicity of the optical system, the smallest number of its individual elements.

The wavelength at which the laser diode emits can change over time under the influence of various external factors, such as temperature. The manufacturing process of the laser diode allows the deviation of the wavelength of the radiation of the diode within 405 ± 10 nm. Temperature changes in the optical head (distances between elements, thicknesses of elements, refractive indices of materials) are slow-moving processes. To reduce additional aberrations (spherochromatism, longitudinal chromatic aberration) arising from the described effects, defocus signals can be used and, by changing the position of the lens, they can significantly reduce their negative effect on the reading and writing of information.

The prior art optical read head (US patent No. 6927923, IPC G02B 13/18, 08/09/2005) containing a radiation source that is a semiconductor laser and forming an optical system that ensures that the beam enters a specified location on the disk, while in the specified optical the system provides a means of correcting spherical aberrations made with the possibility of movement. Thus, in said optical read head, only spherical aberrations are eliminated.

The prior art also knows a combined optical read head for recording optical discs of CD and DVD formats (See US patent No. 6980503B2, IPC G11B 7/00, 12/27/2005), comprising a radiation generating device consisting of two laser sources for emission the first laser beam and the second laser beam, as well as a beam splitter for the formation of collimated beams at the output, while the direction of the first laser beam coincides with the optical axis of the lens, and the second laser beam is offset relative to the optical th lens axis, wherein the second radiation source is arranged so that the angle of incidence of the second laser beam on beam splitter is greater than the angle of incidence of the first laser beam on the beamsplitter, which ultimately helps reduce spherical aberrations arising during operation.

The prior art optical read head for reading and writing HD-DVD format discs (US patent No. 6987724B2, IPC G11B 7/00, 01/17/2006), containing a lens that corrects the chromatic aberration that occurs in the read head due to a change in the wavelength of the laser diode . The HD-DVD format uses a blue laser diode similar to the BD format with a wavelength of 405 nm, but the lens has a smaller numerical aperture NA = 0.65 (for BD NA = 0.85). An optical read head includes a laser diode, a collimator forming a parallel beam, a prism converting an elliptical beam into a round beam, a chromatic aberration correction lens, a beam splitting cube, a polarizing plate, a lens, a condenser lens, an astigmatic lens, and a photodetector. The chromatic aberration correction lens claimed in this patent is a lens bonded from two single lenses having opposite optical powers. At the same time, to correct chromatic aberration, the focal lengths f and the Abbe coefficients (ν) of the lenses that make up this lens are selected in accordance with the expression

The disadvantage of this method is the introduction of an additional bonded lens into the structure of the optical head, which increases its cost. In addition, spherochromatic aberration, which also occurs when the radiation wavelength changes, in this case remains uncorrected.

However, when using a violet laser radiation source in systems using Blu-ray discs (BD), the so-called “mode hop phenomen” or the instability effect of generating a laser diode very often occurs when the wavelength suddenly deviates slightly by a few nanometers from the original value. This effect causes the occurrence of longitudinal chromatic aberration or chromatic shift of focus, which in turn causes extremely undesirable errors in the process of writing to a disc or reproducing information from a disc. This process is random and short-term in nature, as a result of which it cannot be tracked and eliminated using defocus signals.

The claimed optical head for recording on an optical disc and / or reading from an optical disc and kinoforms for use in said optical head according to the invention provides improved accuracy and reliability of recording to a disc and reproducing data from a disc by eliminating spherical and chromatic aberrations.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided an optical head for recording onto and / or reading from an optical disk, comprising optically conjugated laser light sources housed in a housing, a diffraction grating configured to form diffraction beams of zeroth and ± 1st order beams, a beam splitter , kinoform with positive optical power, made with the possibility of movement along the optical axis and the formation at the output of collimated beams of zero and ± 1st order, simultaneous reduction of the longitudinal chromatic aberration of zero-order beams that occurs during the recording and / or reading of information, a polarizing plate for polarizing collimated beams of rays and a lens with positive optical power mounted in front of the optical disk and made with the possibility of movement, as well as an astigmatic lens and photodetector for detecting a beam of light reflected from said disk.

In addition, in the optical head, said disc is a Blu-ray disc.

The laser light source in the inventive optical head provides light with a wavelength of about 405 nm.

Furthermore, in the optical head according to the first aspect of the invention, the kinoform is a positive optical power collimator lens comprising a first surface and a second surface in which the first surface is a flat surface and the second surface is a diffractive surface.

In the inventive optical head, the lens is arranged to move along the optical axis and perpendicular to the specified axis to focus the beam of rays in a predetermined area of the disk, while the specified movement is carried out using the precision electric drive that the lens is equipped with.

In addition, the kinoform is also equipped with a precision electric drive.

,According to a second aspect of the invention, there is provided kinoforms for use in an optical head for recording onto and / or reading from an optical disc, comprising a collimator lens having a first surface and a second surface, wherein the first surface is a flat surface and the second surface is a diffractive surface, while the diffraction surface is formed in accordance with the phase coefficient, determined by the following formula:

,

Where

λ is the wavelength of the radiation incident on the kinoforms;

M is the working diffraction order;

A ₁ is the phase coefficient;

F ₂ - the optical power of the lens;

n _∂ and d are the refractive index and the thickness of the protective layer of the BD disk;

s ₁ is the distance from the radiating surface of the diode to the flat surface of the kinoform;

s ₂ is the distance from the diffraction surface to the lens;

s ₀ 'is the distance from the rear surface of the lens to a given point on the information layer of the disk;

Δ is the distance characterizing the shift of the wavelength λ.

List of drawings

The present invention and its advantages will be better understood when studying the present detailed description with the accompanying drawings.

Figure 1 is a schematic view of an optical head for recording onto and / or reading from an optical disc, in particular a Blu-ray disc according to an embodiment of the present invention, where the profile of the diffraction surface of the kinoform is shown under A.

Figure 2 is a graph of the wave aberration of the optical head for recording on an optical disk and / or reading from an optical disk depending on the radiation wavelength in the case of a smooth process of changing the wavelength due to heating of the diode or changing its power when switching from reading to recording mode ( the dashed line shows the maximum permissible wave aberration for the BD format).

Figure 3 is a diagram illustrating longitudinal spherical aberration curves for an optical head for writing to and / or reading from an optical disk for wavelengths: λ = 405 nm (a), λ = 395 nm (b), λ = 415 nm (at).

Figure 4 depicts a simplified view of the optical head for recording on an optical disk and / or reading from an optical disk in the case of a short-term change in the wavelength of the diode, where in Figure 4a) the radiation of wavelength λ from point O through kinoform 4, lens 6 and the protective layer disk 8 'falls on the information layer of the disk at point O'. In the case of a short-term change in the wavelength, the position of the kinoform and the lens does not change, as shown in Fig.4b). In this case, due to chromatism, the point O 'is shifted by Δ to the point O' ₁ .

5 is a diagram illustrating the diffraction efficiency of a kinoform as a function of wavelength for a working diffraction order. This dependence reflects the dependence of the intensity of radiation concentrated by the kinoform in the working order to the intensity of the radiation that came to the kinoform.

Preferred Embodiment

An optical head for recording onto an optical disc and / or reading from a Blu-ray optical disc is shown in FIG. When the specified optical head operates, the laser light source 1, made in the form of a laser diode, emitting at a wavelength of λ ₀ = 405 nm, forms a diverging beam of rays, which, when passing through the diffraction grating 2, is divided into 3 beams (respectively, the 0th, +1 -th and -1st orders). Figure 1 shows only the course of the beam of the 0th diffraction order, because with its help, information is recorded and read. Beams of the 1st and 1st diffraction orders are auxiliary, they are used to focus the main beam of the 0th order on the track of the disk, as well as tracking (maintaining) the spot formed by the main beam on the information disk along the track. Accordingly, the parameters of auxiliary beams of ± 1 order (such as intensity, divergence, quality) are determined by the specific implementation of tracking and focusing methods. Further, in the framework of the present invention will be considered only the main beam of the 0th order, because its behavior in the case of discs with BD format just causes additional errors of the optical head during recording or reading, which are eliminated by the claimed design of the optical head for writing and / or reading to optical discs according to the present invention. Errors caused by beams of the 1st and 1st orders are eliminated by the technical solutions known from the prior art disclosed in the Prior Art section of the present description and therefore are not disclosed within the framework of the present description. After the diffraction grating 2, the beam passes through the beam splitting cube 3 and falls on the first surface of the kinoform 4, which is a flat surface. Kinoform 4 is a single lens, the first (flat) surface of which is directed towards the laser diode 1, and the second surface on which the diffraction microrelief is provided (diffraction surface - pos. A), towards the optical disk 8. Purpose and parameters of kinoform 4 will be described below. Kinoform 4 converts the diverging beam into a parallel one and directs it through a polarizing plate 5 to a positive optical power lens 6, which focuses the main beam on the information layer 8 '' of the optical disc 8 of the Blu-ray format (BD), after passing through its protective layer 8 '. After reflection from the information layer 8 '', the laser beam returns to the optical system and passes its way in the opposite direction - through the lens 6, then the plate 5 and kinoform 4. The beam splitter 3 directs the reflected beam to the astigmatic lens 9, passing through which it focuses on photodetector 10. Kinoform 4 is made with the possibility of movement along the optical axis of the system and is equipped with a drive 11, which can be a precision electric drive. The lens 6 is also equipped with a drive 7, which can be used precision electric drive, which moves the lens 6 along the optical axis and perpendicular to it, as shown by the arrows in figure 1. Electrical signals for lens movements and kinoform are generated in accordance with tracking and defocus signals that are read from the photo detector. It should also be noted that the information signal is more high-frequency than the tracking and defocus signals. This means that the process of reading information proceeds much faster than signals are sent to move the lens.

As already mentioned, the above kinoform 4, which is a collimator lens on the second surface, has a diffraction relief, which allows to reduce the longitudinal chromatic aberration caused by changes in the wavelength of the laser light source 1.

The claimed optical head for recording on an optical disk and / or reading from an optical disk has a high degree of aberration correction due to a combination of structural parameters (surface radii, thickness of optical elements and air gaps between them, refractive indices of optical materials).

The specified optical head for recording on an optical disk and / or reading from an optical disk by changing the position of the kinoform 4 and the lens 6 can effectively eliminate additional aberrations that occur when the wavelength of the laser light source changes, for example, when it is heated. When switching from the read mode to the write mode, the radiation power increases several times, which is also accompanied by a change in the radiation wavelength. These processes are extended in time and determined, the corresponding values are given in the technical characteristics of laser diodes. Therefore, the resulting aberrations can be partially compensated by defocusing signals taken from the photodetector and supplied to the actuators kinoform 4 and lens 6, which will move them to a position optimal for reducing aberrations (see Fig. 2, 3).

Figure 2 presents a graph of the wave aberration of the optical head for recording on the optical disk and / or reading from the optical disk according to the invention, depending on the radiation wavelength in the case of a smooth process of changing the wavelength due to heating of the laser diode, or changing its power when switching from the mode reading into recording mode, while the dash-dot line shows the maximum permissible wave aberration for the BD format, component 0,033λ. The indicated graph of the aberration wave is constructed in accordance with the values of Table 2 below, which clearly illustrates the specific values of the mean square deviation of the wavefront (or wave aberration) for the optical head for writing to the optical disc and / or reading from the optical disc according to the present invention, as a result of testing. As you can see, the indicated values of the aberration wave are much smaller (see the curve in Fig. 2, indicated by a solid line) of the standard aberration values shown by the dash-dot line in Fig. 2, required in accordance with the BD standard and constituting 0.033λ.

Graphs of the longitudinal spherical aberration of the claimed optical head for recording on an optical disc and / or reading from an optical disc are shown in FIG. 3 for the main wavelength (405 nm) and additional (395 nm and 415 nm). These graphics, constructed using the optical program "CodeV", also indicate the high quality of the declared head. Thus, the optical head according to the invention makes it possible to efficiently read and write data over the entire wavelength range.

However, as mentioned above, when working with a Blu-ray disc at a wavelength of about 405 nm, additional aberrations may occur due to the instability of the generation of a laser diode. This characteristic is also known and entered in the passport of the laser diode, usually for laser diodes used in optical heads of the BD standard, this value does not exceed 2 nm.

But, unlike the temperature and power fluctuations of the wavelength described above, this process is random and short-term. This means that the actuators 7, 11 of the lens 6 and kinoform 4 do not have time to change their position during the action of this negative factor. This leads to the appearance of aberrations of longitudinal chromatism and spherochromatism. This can lead to errors in the process of recording and reading information, since the mean square wave aberration of the head can exceed the maximum permissible value of 0.033λ. Thus, longitudinal chromatism and spherochromatism should be compensated under conditions of immobility of the optical elements of the optical head. Because Since the kinoform (collimator lens) and the lens, in accordance with their functional purpose, have positive optical powers, it is generally impossible to eliminate the arising chromaticity of the position and spherochromatism. By complicating the design of the lens or collimator (see US Pat. Nos. 6,991,996 and 6,906,992) or making a glass collimator with special properties (see US Pat. No. 6,590,851), these aberrations can be reduced. But such solutions complicate the design and significantly increase the cost of the optical head. In addition, these methods are ineffective for correcting spherochromatism.

In the inventive optical head for recording on an optical disk and / or reading from an optical disk, it is proposed to use kinoform 4 as a collimator, having a first surface made in the form of a flat surface and a second surface made in the form of a diffraction surface (see pos. A on Figure 1). This kinoform 4 performs simultaneously collimating and corrective functions.

Figure 4 shows a simplified optical diagram of an optical head for recording on an optical disc and / or reading from an optical disc according to the invention. The emitting surface of the laser diode (t.O), located at a distance s ₁ from the flat input surface of the kinoform 4 (collimator lens), forms a spherical wave front that extends to the kinoform. Kinoform 4 converts a spherical wavefront into a plane (parallel beam of rays), which propagates from the diffraction surface of the kinoform 4 to the lens 6, located at a distance s ₂ from the specified surface. The lens 6 focuses the parallel beam of rays at a point O 'located on the information layer 8''of the optical disk 8 located at a distance s' ₀ from the rear surface of the lens 6 and having a thickness d of the protective layer 8 'of the disk 8. The point O' is called the circle of dispersion due to residual aberrations. In this case, the residual aberrations for the correct recording and reading of information in accordance with the specifications of the BD format should not exceed 0.033λ.

To determine the paraxial parameters of kinoform 4, we consider the head layout in two cases: when the radiation wavelength λ is equal to the nominal value (405 nm, Fig. 4a), and when it changes to a small value δλ (Fig. 4b)). In the first and second cases, the distances s ₁ , s ₂ , s' ₀ remain constant. When the wavelength changes, the point O 'is shifted to the point O' ₁ at a distance Δ relative to the original due to chromatism. In addition, the sizes of the scattering circle increase due to spherochromatic aberration. These aberrations must be corrected or minimized, because they can lead to errors in the process of writing or reading information. To correct these aberrations, it is proposed to use a diffraction surface (see Figure 4, item 4), the parameters of which depend on the parameters of the optical head and minimize the above negative effects. For Fig.4b) can be written using Gaussian brackets:

Where f ₁ , f ₂ - optical power, respectively, kinoform 4 and lens 6;

n _∂ and d are the refractive index and the thickness of the protective layer of the BD disk.

The conjugate points O and O 'are respectively the radiating surface of the laser light source 1 (laser diode) and the point on the information layer of the optical disk 8, in which the beam is focused.

Opening the Gaussian brackets, we obtain the expression for the optical power of kinoform 4:

The phase additive introduced by kinoform 4 into the incident wave front is represented as:

Where λ is the wavelength of the radiation incident on the kinoform 4;

M is the working diffraction order;

A _i - phase coefficients;

r is the distance from an arbitrary point on the surface of the kinoform to its optical axis.

The optical power of the kinoform is written as:

Accordingly, it can be written for the phase coefficient A ₁ :

Thus, if the phase difference introduced by kinoform 4 is determined in accordance with formulas (1) - (5), then the chromaticity of the position can be significantly reduced. The parameters of the diffraction surface of the kinoform are shown in table 3 below.

The following are the specific parameters of the options for implementing an optical head for writing to an optical disk and / or reading from an optical disk, which were obtained as a result of the above calculations (using formulas (1) - (5)) and experimental data obtained as a result of testing, which confirm the effectiveness of the claimed optical head in the process of recording and reading information on BD format discs.

Table 1 shows the main optimal design parameters of the claimed optical head for recording on an optical disc and / or reading from an optical disc, obtained as a result of experiments conducted by the authors during the operation of the optical head with a Blu-ray disc.

Table 1
Design parameters of the optical head No. R mm d mm n _λ , λ = 405 nm one' ∞ ¹ 0.25 1,530196 one'' ∞ 4.8 one 2 ' ∞ one 1,530196 2 '' ∞ 0.73 one 3 ' ∞ 4.8 1,530174 3 '' ∞ 5 ^* one four' ∞ 1,2 1,525056 4 '' ² -56.36 7.4 ^* one 5' ∞ one 1,530174 5'' ∞ 2.1965 ^* one 6 ' 1,1478 2 1,525056 6 '' -1.5778 0.6035 ^* one 8' ∞ 0.1 1,617688 8'' ∞ - - ¹ - for flat surfaces, the radius R = ∞ (infinity).
² - diffraction surface of the kinoform. The parameters will be given below.
^* - air gaps that can change during operation of the optical read head (see table 3).

In table 1, the numbers of optical surfaces are shown along the propagation of radiation in accordance with Figure 1: surfaces 1 'and 1''are the input and output surfaces of the protective glass of the laser light source 1, which are flat; surfaces 2 'and 2''- input and output surfaces of the diffraction grating 2; surfaces 3 'and 3''- input and output surfaces of the beam splitting cube 3; surfaces 4 'and 4''- flat input and diffraction surfaces of kinoform 4; surfaces 5 'and 5''- input and output surfaces of the polarizing plate 5; surfaces 6 'and 6''- input and output surfaces of the lens 6; surface 8 'corresponds to the input surface of the protective layer BD of the disk 8', surface 8 "is an information layer 8". According to formula (5), the following parameters of the diffraction surface 4 '' of the kinoform 4 were obtained: with a working diffraction order of M = 1, a phase coefficient A ₁ = -0.026 was obtained. The parameters of the diffraction surface of the kinoform are calculated in such a way that it concentrates the radiation incident on it in a given diffraction order (in our case, + 1). When the radiation wavelength is changed, in addition to the effects described above, the radiation energy is redistributed to other diffraction orders, which accordingly reduces the amount of energy in the working 1st order. The dependence of the intensity of the radiation incident on the diffraction surface on the intensity of the emitted radiation for different diffraction orders is called diffraction efficiency. The graph of the diffraction efficiency of the 1st order of the claimed kinoform 4 in the claimed optical head for recording on an optical disk and / or reading from an optical disk depending on the wavelength is shown in Fig.5.

Table 2 shows the residual aberrations (standard deviation of the wavefront ((RMS) in wavelengths) and distances (d ₈ , d ₁₀ ) that determine the position of kinoform 4 and distances (d ₁₂ , d ₁₄ ) that determine the position of lens 6 depending from a wavelength in increments of 2 nm in the case of a smooth process of changing the wavelength (see also Figs. 2 and 3) obtained by testing the inventive optical head for writing to an optical disc and / or reading from an optical disc according to the invention.

table 2 λ, nm d ₈ d ₁₀ d ₁₂ d ₁₄ SKO, dl. the waves 395 6.0400 6.3600 2,2054 0.5946 0.0073 397 5.8190 6.5810 2,2036 0.5964 0.0061 399 5.6050 6.7950 2,2018 0.5982 0.0049 401 5.3970 7,0030 2,2000 0.6000 0.0036 403 5,1951 7,2049 2.1983 0.6017 0.0022 405 5,0000 7.4000 2.1965 0.6035 0.0011 407 4.8025 7.5975 2.1947 0.6053 0.0017 409 4,6111 7,7889 2.1930 0.6070 0.0025 411 4,4449 7.9551 2.1914 0.6086 0.0034 413 4.2713 8.1287 2,1897 0.6103 0.0044 415 4,1000 8.3000 2,1881 0.6119 0.0060

Table 3 shows the longitudinal chromaticity Δf 'and residual wave aberration obtained by testing the inventive optical head for recording on an optical disk and / or reading from an optical disk with kinoform 4, in case of instability of the generation of laser diode 1 (laser radiation source), those. with a random random change in the radiation wavelength.

Table 3 λ, nm

,мкм

μm SKO, dl. the waves 403 -0.150 0,026 404 -0.075 0.013 405 0,000 0.001 406 0,072 0.014 407 0.140 0,028

It should be noted that the wave aberration values given in Tables 2 and 3 do not exceed those required by the BD standard 0.033λ. Thus, the claimed optical head effectively eliminates all of the above problems and improves the reliability and accuracy of recording and playback of optical discs in BD format.

Industrial applicability

The claimed invention relates to an optical head for reading and / or writing information to a disc and can be used when working with optical discs, in particular Blu-ray discs.

Claims (9)

1. An optical head for recording on an optical disk and / or reading from an optical disk, comprising a laser light source optically coupled in a housing, a diffraction grating configured to form diffraction beams of zero and ± 1 order rays, a beam splitter, kinoform with positive optical power, made with the possibility of moving along the optical axis and the formation of collimated beams of zero and ± 1st order at the output, and at the same time reducing the longitudinal chromatic the aberration of zero-order beams arising during the recording and / or reading of information, a polarizing plate for polarizing collimated beams of rays, and a lens with positive optical power mounted in front of the optical disk and made with the possibility of movement, as well as an astigmatic lens and photo detector for detecting the beam light reflected from said disk. 2. The optical head of claim 1, wherein said disc is a Blu-ray disc (BD disc). 3. The optical head according to claim 1, in which the laser light source provides light with a wavelength of about 405 nm. 4. The optical head according to claim 1, in which the kinoform is a collimator lens with positive optical power, comprising a first surface and a second surface. 5. The optical head according to claim 4, in which the first surface is a flat surface, and the second surface is a diffractive surface. 6. The optical head according to claim 1, in which the lens is arranged to move along the optical axis and perpendicular to the specified axis to focus the beam beams in a predetermined area of the disk. 7. The optical head according to claim 1, in which the lens is equipped with a precision electric drive. 8. The optical head according to claim 1, in which the kinoform is equipped with a precision electric drive. 9. Kinoform for use in an optical head for recording on an optical disc and / or reading from an optical disc according to claims 1 to 8, comprising a collimator lens having a first surface and a second surface, the first surface being a flat surface and the second surface being diffraction surface, while the diffraction surface is formed in accordance with the phase coefficient determined by the following formula:

,
where λ is the wavelength of the radiation incident on the kinoforms;
M — working diffraction order;
A ₁ is the phase coefficient;
F ₂ - the optical power of the lens;
n _∂ and d are the refractive index and the thickness of the protective layer of the optical disk;
s ₁ - the distance from the emitting surface of the laser light source to the flat surface of the kinoform;
s ₂ is the distance from the diffraction surface to the lens;
s ₀ 'is the distance from the rear surface of the lens to a given point on the information layer of the disk;
Δ is the distance at which the point at which the light beam is focused when the wavelength λ changes.

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