CN1758348A - Laser read-write lens of holographic optical disk memory - Google Patents

Abstract

This invention relates to a laser read-write lens of a optical-disk storage, in which, two Fourier transformation lens sets are serial and in the structure of asymmetrical structure, the anaberration and aberration design is carried out according to the pixel diameter of the special light modulator and a face array photoelectric coupler to match the lens set amplification rate, the optical axis of the anaberration reference lens and the Fourier transformation lens forms a angle and two Fourier transformation lens and the reference optical lens form a laser read-write lens of a three lens combined optical-disk storage.

Description

The laser read-write lens of holographic optical disk memory

Technical field

The laser read-write lens of holographic optical disk memory belongs to field of optical storage technology.

Background technology

The light holographic memory is as a kind of novel HIGH-DENSITY OPTICAL STORAGE system, because every advantage such as its memory capacity is big, highly redundant degree, fast message transmission rate and access time are short is causing research field people's very big concern.At present because the maturation of the correlation technique of solid state laser, high resolution space photomodulator and high resolving power high-speed photodetector etc. more and more develops high density light holographic memory to the practicability direction.The storage of light holographic information storage meanss such as Fresnel holography, image plane holographic and Fourier transform holography are arranged, and Fourier transform hologram wherein has the space displacement unchangeability according to different situations and needs, and it is taken advantage in the spatial reuse storage.

Holographic optical disk memory is a kind of light holographic memory that adopts disk storage medium, camera lens as the laser and/write of holographic optical disk memory is made up of the fourier transform lens group and the reference light lens of particular design, two fourier transform lenses being composed in series the 4f system finishing information processing, is that input information is carried out the core instrument that Fourier transformation computation is handled.Form hologram with interfering through the thing optical information after spatial light modulator (SLM) modulation after through a fourier transform lens, be stored in certain the locational hologram memory medium that is arranged between the Fourier lens group from the reference light of reference lens.When reading, be radiated at by the reference light camera lens on the storage medium of holographic optical disk with reference light, second Fourier camera lens of the information via in the storage medium is reduced into the thing optical information of SLM, is imaged onto on the face battle array photoelectric coupled device the reading of the data of realization.

Fig. 1 is the fundamental diagram of read-write lens in the holographic optical disk memory.Shine the spatial light modulator (SLM) 1 that places on the lens front focal plane with directional light, be called page composer again, it is rendered as optical imagery with information to be stored, sees through fourier transform lens FTL ₁2, near its back focal plane, lay holographic optical disk 4, introduce another reference beam 3 through reference light camera lens 7, form the hologram of interfering, the hologram of this interference can be noted by holographic optical disk under certain light intensity.With the hologram in the former reference light illumination holographic optical disk, by fourier transform lens FTL ₂5 make inverse fourier transform, just can reproduce former canned data on its back focal plane plane, form image, at this placed side, position battle array photoelectric coupled device 6, as CCD device or COMS device etc., just can realize reading of canned data.

General fourier transform lens group all is to connect with the symmetrical structure form with the fourier transform lens of two optical parametric unanimities at present, and holographic optical disk is between two camera lenses, and the reference light camera lens only adopts the positive lens of a single eyeglass.Its shortcoming one is because the focal length of two Fourier camera lenses is the same, its magnification is 1, be not 1: 1 spatial light modulator and face battle array photoelectric coupled device like this for the Pixel Dimensions ratio, each pixel that can not realize them all is complementary, limit the reading speed of canned data, increased the bit error rate of data.Shortcoming two is that not only focal length is long because traditional fourier transform lens is not designed at holographic memory, and volume is big, and aberration do not obtain enough corrections yet, the requirement that makes the bit error rate of canned data not reach data storage.Shortcoming three is that reference light does not have specially at the designed anaberration reference light camera lens of holographic memory, when the optical axis of reference light and storage medium surface normal have the minute angle error, can make the light spot shape of reference hot spot in storage medium that contains aberration correction not irregular, light energy distribution is inhomogeneous, cause the interference hologram image uneven illumination that is stored in the medium even, make the bit error rate of data be difficult to control.Do not have special short focal length at the design of 3-dimensional digital holographic memory in addition, wide-aperture reference light camera lens does not reach the high density purpose of three-dimensional storage storage.

Summary of the invention

Holographic optical disk memory spatial light modulator and the face battle array photoelectric coupled device pixel matching problem of the present invention in order to solve above-mentioned proposition, and, a kind of laser read-write lens of the holographic optical disk memory based on the Fourier transform hologram has been proposed with reference to problems such as the of poor quality and practicability of hot spot.

The laser read-write lens of the holographic optical disk memory that the present invention is designed, concrete structure is referring to Fig. 2～3.The present invention includes fourier transform lens (FTL ₁) 2 and fourier transform lens (FTL ₂) 5 two camera lens and reference light camera lenses 7, fourier transform lens 2 and fourier transform lens 5 series connection, holographic optical disk is between two fourier transform lenses, storage medium vertically fourier transform lens 2 optical axis or be placed between fourier transform lens 2 and the fourier transform lens 5 for 30 °～60 ° with angle with it, reference light camera lens 7 and the angled placement of fourier transform lens optical axis, angle is at 30 °～150 °, and the optical axis of these three camera lenses is all in same plane, referring to Fig. 2.

Fourier transform lens group among the present invention adopts asymmetric structure.The focal distance ratio of two fourier transform lenses equals the Pixel Dimensions size ratio of spatial light modulator and face battle array photoelectric coupled device, and two fourier transform lenses have the combination of multiple different focal.

The series connection of fourier transform lens 2 and 5 front and back, after adding the storage medium of holographic optical disk between 2 and 5, holographic optical disk storage medium surface normal and fourier transform lens 2 vertical the time, the optical axis of camera lens 5 and camera lens 2 is coaxial.When holographic optical disk storage medium surface normal and fourier transform lens 2 when certain angle is arranged, because storage medium has the deviation effect to the information light from camera lens 2, make the optical axis of information carrying beam produce certain parallel translation, the camera lens 5 of the present invention's design is not coaxial with camera lens 2, the two optical axis is positioned at same plane and parallel, two light shaft offset amounts and offset direction equal because side-play amount and the direction that the holographic optical disk storage medium produces the optical axis refraction of information carrying beam, can guarantee the actual alignment and the aberration requirement of light path, 2 and 5 light shaft offset amount increases progressively according to the angle and the storage medium thickness of holographic optical disk and fourier transform lens 2, and scope is 1～6mm.

Fourier transform lens 2 is formed by four groups four: first group is first monolithic biconvex lens 12 with positive light coke, second group is second meniscus lens 13 with negative power, the 3rd group is that to have three thick biconcave lenss of negative power be for 14, the four groups the 4th thin biconvex lens 15 with positive light coke.This camera lens effective focal length scope is between 100mm～150mm, and relative aperture is between 1/5～1/2.5.

The design of fourier transform lens 2 back has a taper sheath as wave filter, the spectrum filtering of all the other grades on the frequency plane that spatial light modulator is produced after through 2 conversion time, only keep the maximum zero level spectrum 26 of diffracted intensity, can remove the interference of diffraction light at different levels to memory image, the present invention determines the clear aperature of tapered cover wave filter diaphragm according to the size of zero level spectrum face 26.The square single pixel length of side of spatial light modulator is b, and operation wavelength is λ, and f is fourier transform lens FTL ₁Back focal length 9, zero level spectrum face size is $w=\frac{2\mathrm{\&lambda;<figure-callout\; id="2"\; label="f\; b"\; filenames="A20051009833800141.png"\; state="\{\{state\}\}">f</figure-callout>}}{b^{}}\&CenterDot;$ And by fourier transform lens FTL ₁Back focal length 9 and the diameter of last a slice lens 15 of this camera lens awl height and the cone bottom diameter that are used as tapered wave filter.Tapered cover inside surface is done not reflective processing, referring to Fig. 2 and Fig. 3.

Fourier transform lens 5 is formed by three groups four, and first group is FTL ₂First have negative power monolithic meniscus lens, second group is FTL ₂The centre have positive light coke monolithic biconvex lens, the 3rd group is the cemented doublet with positive light coke.Its effective focal length scope is between 40mm～80mm, and relative aperture is between 1/6～1/3.

Wave aberration after fourier transform lens 2 and 5 the combination is less than λ/4, and modulation transfer function MTF is when 401p/mms, and greater than 0.5, maximum distortion is less than 0.012% in the full visual field, and spherical aberration is less than 0.2mm.Effective work focal length before and after in the middle of 2 and 5 satisfies the installation and the work space of SLM and CCD and hologram memory medium, can the implementation space photomodulator and 1: 1 coupling of face battle array photoelectric coupled device spare pixel.

Reference light camera lens 7 is made up of three-group three-piece, and first group is the single convex lens with positive light coke, and second group for having negative power monolithic biconcave lens, and the 3rd group for having positive light coke biconvex positive lens.Numerical aperture 0.28～0.4.Last a slice aperture of lens is between 40mm～80mm.Reference light is with the beam convergence through beam-expanding collimation, obtains anaberration and gets circular light spot.Light spot energy is evenly distributed, improves picture quality.

Among the present invention the above all eyeglass be spherical lens, and lens machining center deviation is all less than 0.005mm, the center thickness error is less than 0.02, error of curvature is less than two apertures.

This camera lens can be used for FTL ₁Focal length between 100mm～150mm, FTL ₂Focal length between 40mm～75mm, the holographic optical disk memory laser and/write of operation wavelength 532nm.Two fourier transform lenses adopt unsymmetric structure, focal length is inequality, the magnification that can make up according to the Pixel Dimensions coupling camera lens of spatial light modulator and face battle array photoelectric coupled device, carry out anaberration and distortion design, can realize the pixel matching requirement of holographic optical disk memory, reach fast and read, reduce the purpose of the bit error rate.When the reference light camera lens of design of matching with it can satisfy the optical axis of reference light and storage medium surface normal the minute angle error is arranged, the light spot shape rule of reference light in storage medium, light energy distribution is even, and the interference hologram image illumination that is stored in the medium is even, reduces the bit error rate.Short in addition focal length, wide-aperture reference light camera lens can improve the storage density of holographic optical disk memory.

Description of drawings

The fundamental diagram of the laser read-write lens of Fig. 1 holographic optical disk memory;

1. spatial light modulator 2. fourier transform lens FTL ₁3. reference light 4. storage mediums 5. fourier transform lens FTL ₂6. face battle array photoelectric coupled device 7. reference light camera lens 8.FTL ₁Preceding work focal length 9.FTL ₁Back work focal length 10.FTL ₂Preceding work focal length 11.FTL ₂The optical structure chart of laser read-write lens of back work focal length Fig. 2 holographic optical disk memory;

12.FTL ₁First biconvex lens 13.FTL ₁Second meniscus lens 14.FTL ₁The 3rd thick biconcave lens 15.FTL ₁The 4th thin biconvex lens 16.FTL ₂Cemented doublet 17.FTL ₂Second positive light coke biconvex lens 18.FTL ₂Single convex lens 22. pyramid type wave filters of first positive light coke of the 3rd positive light coke biconvex positive lens 20. reference lighies of first negative power monolithic meniscus lens 19. reference light second negative power monolithic biconcave lens 21. reference lighies

Fig. 3 fourier transform lens FTL ₁With zero level spectrum face calculated relationship;

23.λ/b 24.b 25.w。

Embodiment

Embodiment 1:

According to principle and the method in the invention, the laser read-write lens of a holographic optical disk memory of design.Wherein, under the wavelength condition of 532nm, fourier transform lens FTL ₁Focal length is 100mm, fourier transform lens FTL ₂Focal length is 40mm.Can satisfy spatial light modulator pixel and face battle array photoelectric coupled device Pixel Dimensions ratio and be the pixel matching requirement of laser read-write lens of 5: 2 holographic optical disk memory.Optical texture as shown in Figure 2, fourier transform lens group FTL ₁And FTL ₂With FTL ₁First lens surface of first group as lens surface numbering 1, have 16 faces.

1. fourier transform lens group FTL ₁And FTL ₂Have related parameter as follows:

The lens surface numbering	Radius-of-curvature	Center thickness	The glass trade mark	Bore
					1	34.26	6.60	ZK11	35
2	-712	0.76		35
					3	31.28	3.77	ZK11	32
4	47.931	2.90		32
					5	-483.964	7.06	ZF2	30
6	21.427	25.87		30
					7	74.38	4.30	ZK11	24
8	-1606	46.33		24
					9STO	Infinity	29.58		6
10	-15.68	8.72	ZK11	24
					11	-21.81	0.56		24
12	161.1	3.66	ZK11	24
					13	-46.15	0.27		24
14	36.632	3.49	ZF7	24
					15	18.427	9.58	ZK11	20
16	76.02	37.91		20

FTL ₁And FTL ₂After the combination, modulation transfer function MTF is when 401p/mms, and greater than 0.6, distortion is less than 0.01% in the full visual field.

2. reference light camera lens

Under the wavelength condition of 532nm, this reference light lens focus is numerical aperture N.A.=0.3.First lens surface with first group on reference light camera lens numbers 1 as lens surface, has six faces.Have related parameter as follows:

The lens surface numbering	Radius-of-curvature	Center thickness	The glass trade mark	Bore
					1	29.93	5.58	ZF2	30
2	269.87	10.30		30
					3	-30.91	1.90	K9	30
4	52.12	8.40		24
					5	137.99	5.7	ZF2	24
6	-29.99	34.67		24

Embodiment 2:

According to principle and the method in the invention, the laser read-write lens of a holographic optical disk memory of design.Wherein, under the wavelength condition of 532nm, fourier transform lens FTL ₁Focal length is 130mm, fourier transform lens FTL ₂Focal length is 60mm.Can satisfy spatial light modulator pixel and face battle array photoelectric coupled device Pixel Dimensions ratio and be the pixel matching requirement of laser read-write lens of 13: 6 holographic optical disk memory.Optical texture as shown in Figure 2, fourier transform lens group FTL ₁And FTL ₂With FTL ₁First lens surface of first group as lens surface numbering 1, have 16 faces.

1. fourier transform lens group FTL ₁And FTL ₂Have related parameter as follows:

The lens surface numbering	Radius-of-curvature	Center thickness	The glass trade mark	Bore
					1	44.26	8.62	ZK11	46
2	-912	1		46
					3	41.28	4.91	ZK11	40
4	61.931	3.77		40
					5	-627.964	9.18	ZF2	40
6	27.427	33.64		36
					7	96.38	5.59	ZK11	32

8	2088	60.23		32
					9STO	Infinity	43.58		6
10	-22.68	13.09	ZK11	24
					11	31.81	0.76		34
12	242.1	5.49	ZK11	34
					13	70.15	0.41		34
14	54.632	5.24	ZF7	34
					15	27.427	14.38	ZK11	34
16	114.02	56.84		28

FTL ₁And FTL ₂After the combination, modulation transfer function MTF is when 401p/mms, and greater than 0.6, distortion is less than 0.01% in the full visual field.

2. reference light camera lens

Under the wavelength condition of 532nm, this reference light lens focus is numerical aperture N.A.=0.3.First lens surface with first group on reference light camera lens numbers 1 as lens surface, has six faces.Have related parameter as follows:

The lens surface numbering	Radius-of-curvature	Center thickness	The glass trade mark	Bore
					1	41.93	7.82	ZF2	44
2	377.87	14.42		40
					3	42.91	2.40	K9	36
4	73.12	11.40		34
					5	191.99	8	ZF2	34
6	41.99	47.67		34

Embodiment 3:

According to principle and the method in the invention, the laser read-write lens of a holographic optical disk memory of design.Wherein, under the wavelength condition of 532nm, fourier transform lens FTL ₁Focal length is 150mm, fourier transform lens FTL ₂Focal length is 75mm.Can satisfy spatial light modulator pixel and face battle array photoelectric coupled device Pixel Dimensions ratio and be the pixel matching requirement of laser read-write lens of 2: 1 holographic optical disk memory.Optical texture as shown in Figure 2, fourier transform lens group FTL ₁And FTL ₂With FTL ₁First lens surface of first group as lens surface numbering 1, have 16 faces.

1. fourier transform lens group FTL ₁And FTL ₂Have related parameter as follows:

The lens surface numbering	Radius-of-curvature	Center thickness	The glass trade mark	Bore
					1	51.26	9.62	ZK11	48
2	-1052	1.15		48
					3	47.28	5.66	ZK11	46
4	71.931	4.77		46
					5	-724.964	10.18	ZF2	46
6	31.427	38.64		40
					7	111.38	6.59	ZK11	38
8	-2409	69.23		38
					9STO	Infinity	54.58		5
10	-28.68	16.09	ZK11	30
					11	-39.81	0.96		43
12	302.61	6.49	ZK11	43
					13	-87.15	0.51		43
14	68.632	6.55	ZF7	43
					15	34.427	17.38	ZK11	34
16	142.02	71.09		30

FTL ₁And FTL ₂After the combination, modulation transfer function MTF is when 401p/mms, and greater than 0.5, distortion is less than 0.012% in the full visual field.

2. reference light camera lens

Under the wavelength condition of 532nm, this reference light lens focus is numerical aperture N.A.=0.3.First lens surface with first group on reference light camera lens numbers 1 as lens surface.Have related parameter as follows:

The lens surface numbering	Radius-of-curvature	Center thickness	The glass trade mark	Bore
					1	53.93	10.06	ZF2	56
2	485.87	18.54		56
					3	-55.91	3.08	K9	46
4	94.12	14.66		42
					5	246.99	10.28	ZF2	42
6	-53.99	61.67		42

Annotate: the above glass is Chinese glass storehouse GB903-87

Claims (5)

1, the laser read-write lens of holographic optical disk memory, comprise fourier transform lens (2) and fourier transform lens (5) and reference light camera lens (7), fourier transform lens (2) and fourier transform lens (5) are connected and are positioned at the both sides of storage medium (4), it is characterized in that: the optical axis of the vertical fourier transform lens (2) of storage medium (4) or be placed between fourier transform lens (2) and the fourier transform lens (5) for 30 °～60 ° with angle with it, reference light camera lens (7) and fourier transform lens (2) optical axis included angle are at 35 °～150 °, and the optical axis of these three camera lenses is all in same plane; The fourier transform lens group adopts asymmetric structure: the focal distance ratio of two fourier transform lenses equals the Pixel Dimensions size ratio of spatial light modulator and face battle array photoelectric coupled device; When storage medium vertically was placed between fourier transform lens (2) and the fourier transform lens (5), fourier transform lens (5) was coaxial with fourier transform lens (2); When storage medium is placed between fourier transform lens (2) and the fourier transform lens (5) with certain angle, fourier transform lens (5) is not coaxial with fourier transform lens (2), the two optical axis is positioned at same plane and parallel, two light shaft offset amounts and offset direction equal because side-play amount and the direction that holographic optical disk storage medium (4) produces the optical axis refraction of information carrying beam, the light shaft offset amount of fourier transform lens (2) and (5) increases progressively according to the angle and the storage medium thickness of storage medium and fourier transform lens (2), and scope is 1～6mm.

2, the laser read-write lens of holographic optical disk memory according to claim 1, it is characterized in that: fourier transform lens (2) is formed by four groups four: first group is the first monolithic biconvex lens (12) with positive light coke, second group is second meniscus lens (13) with negative power, the 3rd group is to have three thick biconcave lenss of negative power (14), and the 4th group is the 4th thin biconvex lens (15) with positive light coke; This camera lens effective focal length scope is between 100mm～150mm, and relative aperture is between 1/5～1/2.5; Fourier transform lens (5) is formed by three groups four, and first group is FTL ₂First have negative power monolithic meniscus lens (18), second group is FTL ₂The centre have positive light coke monolithic biconvex lens (17), the 3rd group is the cemented doublet (16) with positive light coke; Its effective focal length scope is between 40mm～80mm, and relative aperture is between 1/6～1/3.

3, the laser read-write lens of holographic optical disk memory according to claim 1 and 2, it is characterized in that: fourier transform lens (2) and (5) combination magnification equal the Pixel Dimensions size ratio of spatial light modulator and face battle array photoelectric coupled device, fourier transform lens (2) and (5) combination distortion are less than 0.012%, and the pixel of magnification and distortional strain energy implementation space photomodulator and face battle array photoelectric coupled device is mated at 1: 1.

4, the laser read-write lens of holographic optical disk memory according to claim 1, it is characterized in that: reference light camera lens (7) is made up of three-group three-piece, first group is the single convex lens (21) with positive light coke, second group for having negative power monolithic biconcave lens (20), and the 3rd group for having positive light coke biconvex positive lens (19); Numerical aperture 0.28～0.4; Last a slice lens (19) bore is between 40mm～80mm.

5, the laser read-write lens of holographic optical disk memory according to claim 1 and 2, it is characterized in that: be provided with a taper sheath behind the fourier transform lens (2) as wave filter, be used as the awl height and the cone bottom diameter of tapered wave filter respectively by the diameter of the 4th thin biconvex lens (15) of the back work focal length (9) of fourier transform lens (2) and this camera lens, the catercorner length of diaphragm or diameter equal the catercorner length or the diameter of zero level spectrum face (25); Tapered cover inside surface is reflecting surface not.

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