CN200965781Y - Miniature compatible double wavelength optical head - Google Patents

Abstract

A micro compatible double wavelength optical head comprises two semiconductor lasers with wavelengths of 405nm and 650 nm respectively, the two beams of lasers use the main optical path together by using the half reverse pellicle lens and the beam splitter prism; after going through the beam splitter prism, a pentagonal prism, a collimation lens, an aspheric objective lens are formed respectively, and then the lasers can concentrate on an information recording layer of the a CD. The beams reflected by the CD return along the original path and go through sequentially a objective lens, the collimation lens, the pentagonal prism, the beam splitter, the half reverse pellicle lens and a cylindrical lens, and finally are received by a photo detector. Wherein the beam splitter prism can completely transmit the 405nm incident beam, and completely reflect the 650nm incident beam and the returned beam from the CD; the half reverse pellicle lens can reflect the 650 nm incident beam and the returned beam from the CD completely. The cylindrical lens plays the role of reshaping the beam. The utility model not only can compatibly read HDDVD and DVD disk, but also has the advantages of excellent capability, simple and tight structure, easy assembly and low producing cost, etc.

Description

Micro dual wavelength optical head with compatibility

Technical field

The utility model relates to CD player, particularly a kind of micro dual wavelength optical head with compatibility that is applicable to CD player.It can be used for optical storage technology of future generation, can also compatible existing DVD CD.

Background technology

Information age needs highly advanced information storage technology.Along with the digital product and the arrival in HDTV epoch, high-density digital multi-usage CD (being designated hereinafter simply as HDDVD) that memory capacity is bigger and the serial optical disc of future generation of Blu-ray Disc (being designated hereinafter simply as BD) will become main flow.They are based on the blue light technology, and memory capacity reaches 15G and 23G respectively.Because HDDVD adopts the object lens of 0.65 numerical aperture, the disc protective layer thickness is 0.6mm, thereby it can be smoothly and existing digital multi-purpose CD (being designated hereinafter simply as DVD) technical compatibility, and production cost and price are more cheap, thereby have the bigger market advantage.

Because the memory capacity of CD is increasing, single-surface single-layer HDDVD can store the information of 15GB, and therefore the requirement to reading speed also improves greatly.A method that improves the optical head reading speed is exactly weight and the size that reduces optical head, thereby reduces inertia, makes it can track fast, focus on.The HDDVD system often adopts the twin-laser structure for the backward compatible DVD of energy, launches blue light 405nm and ruddiness 650nm respectively.Fig. 2 is the common structure of HDDVD optical head, adopt blue-light semiconductor laser instrument (being called for short LD) 11, laser arrives HDDVD CD 16 through optical elements such as beam splitter prism 12, collimation lens 13, catoptron 14, object lens 15 successively, then through CD 16 reflections, pass through object lens 15, catoptron 14, collimating mirror 13, beam splitter prism 12 again, finally received by photo-detector (PDIC) 17.Therefore find out that by above-mentioned the total system optical element is many, and between each element certain distance will be arranged, whole optical head assembly volume is big, loosely organized, thus make track, the time lengthening of focus servo.In addition, head systems is strict to beam quality and aberration, so each element also needs accurate calibration, could guarantee not produce extra aberration, and this has also just increased difficulty technically.

Summary of the invention

The purpose of this utility model is in order to overcome above-mentioned the deficiencies in the prior art, provides a kind of micro type compatible optical head, and this optical head should be able to compatible high-density digital multi-usage CD and digital multi-purpose CD, its structure should be simply and compact, volume is less, and easy to assembly, and is with low cost.

The utility model technical solution is as follows:

A kind of micro dual wavelength optical head with compatibility, its formation is: contain first semiconductor laser and second semiconductor laser, on the output light path of first semiconductor laser, be provided with beam splitter prism successively, pentagonal prism, collimating mirror, object lens constitute main optical path, CD is positioned on the focal plane of described object lens, the laser that described second semiconductor laser sends is through half-reflecting half mirror, after described beam splitter prism reflection, enter described main optical path again, information recording layer beam reflected by described CD is returned along former road, through described object lens, collimating mirror, pentagonal prism, beam splitter prism, half-reflecting half mirror and cylindrical mirror are received by photo-detector at last.

The described first semiconductor laser emitted laser wavelength is 405nm, the described second semiconductor laser emitted laser wavelength is 650nm, described beam splitter prism is to the complete transmission of the incident light of 405nm, and the incident light of 650nm is reflected fully, and the back light from CD is reflected fully; Described half-reflecting half mirror reflects fully to the incident light of 650nm, and the back light from CD is reflected fully.

The shape of described pentagonal prism is determined by following parameter: two right angle length of side A, and both sides length of side B, side angle θ=22.5 ° is to parallactic angle =45 °.

Described object lens are non-spherical lens, and two surfaces of this non-spherical lens all are aspheric surfaces, and its radius-of-curvature is 1.5～7mm, and center thickness is 0.8～1.5mm, and numerical aperture is 0.65.Two aspheric asphericity coefficients of described object lens are as follows:

Asphericity coefficient c k α ₁

Aspheric surface 1 0.34771-3.365044 0.007077

Aspheric surface 2-0.61563-4.449736 0.008442.

Two semiconductor lasers of the present utility model read with the compatibility that realizes HDDVD and DVD respectively; Described cylindrical mirror plays the beam shaping effect, the ellipse light spot of semiconductor laser can be become circular light spot.

The shape of described pentagonal prism is determined by following parameter: two right angle length of side A, and both sides length of side B, side angle θ=22.5 ° is to parallactic angle =45 °.Light comes back reflective twice in prism, walked (2+ ) A, has played the effect of shortening the optical head size.

A face of described collimating mirror is the plane, and another side is an aspheric surface, but does not have the high-order asphericity coefficient.Its effect is to make that to incide in the object lens be parallel beam.Can also compensate spherical aberration in addition.The utility model head systems adopts focusing and the servo mode that tracks, the i.e. method of astigmatism and the difference phase scheme of existing dvd system.As seen this optical head can well be realized the compatibility of HDDVD and DVD.

The phase of wave difference root mean square RMS value at the focus place of the utility model under 405nm is less than 0.001 λ, and the RMS value at the focus place under the 650nm is less than 0.003 λ, also less than allowable value 0.033 λ of dvd system.Because the most of place of 650nm light path is shared with the 405nm light path, promptly can read the DVD CD so the HDDVD system only need change the spacing of several parts.After HDDVD finished optimal design, if order emission optical maser wavelength is that to be that second semiconductor laser of 650nm arrives semi-transparent semi-reflecting mirror spacing identical with launching optical maser wavelength to semi-transparent semi-reflecting mirror spacing for first semiconductor laser of 405nm, then only need to adjust the spacing between semi-transparent semi-reflecting lens and the beam splitter prism, can realize dvd system is well optimized, obtain compatible optical pickup.When reading the DVD CD,, can realize that the compatibility of HDDVD and DVD CD reads by the operating distance of focus servo institutional adjustment object lens.

Below in conjunction with embodiment and accompanying drawing the utility model is described further, but should limit protection domain of the present utility model with this:

Description of drawings

Fig. 1 is the utility model optical head light channel structure synoptic diagram.

Fig. 2 is existing HDDVD optical head light channel structure synoptic diagram.

Fig. 3 is the structural representation of pentagonal prism.

Fig. 4 is to be that the light path of light source is carried out the resulting lateral aberration analysis chart of optical design (Ray Fan) with ZEMAX to 405nmLD.

Fig. 5 is to be that the light path of light source is carried out wave aberration analysis chart (RMS ﹠amp before and after the resulting focus of optical design with ZEMAX to 405nmLD; Focus).

Fig. 6 is to be that the light path of light source is carried out imaging facula analysis chart (Spot Diagram ﹠amp before and after the resulting focus of optical design with ZEMAX to 405nmLD; Focus).

Fig. 7 is to be that the light path of light source is carried out the resulting point spread function figure of optical design with ZEMAX to 405nmLD.

Fig. 8 is to be that the light path of light source is carried out the resulting point spread function figure of optical design with ZEMAX to 650nmLD.

Fig. 9 is to be that the light path of light source is carried out the resulting wave front chart of optical design (Wave front) with ZEMAX to 650nmLD.

Embodiment

See also Fig. 1 earlier, Fig. 1 is the light channel structure synoptic diagram of the compatible optical head embodiment of the utility model micro type.As seen from the figure, the formation of the compatible optical head of the utility model micro type: contain first semiconductor laser 1 and second semiconductor laser 7, the wavelength of emission is respectively 405nm and 650nm, realizes that the compatibility of HDDVD and DVD reads; The shared main optical path of two-beam that two semiconductor lasers is sent with half-reflecting half mirror 8 and beam splitter prism 2; Through behind the beam splitter prism 2, be respectively pentagonal prism 3, collimating mirror 4, object lens 5, these object lens 5 are non-spherical lens, laser convergence is on the information recording layer of CD 6 then.The information recording layer of CD can be worked as reflectance coating, thereby convergent beam returns along former road, pass through object lens 5, collimating mirror 4, pentagonal prism 3, beam splitter prism 2, half-reflecting half mirror 8, cylindrical mirror 9 successively, arrive photo-detector 10 at last, be received and obtain to read information.The wherein complete transmission of incident light of 2 couples of 405nm of beam splitter prism is reflected fully to the incident light of 650nm, and the light that returns from CD 6 is reflected fully.The incident light of 8 couples of 650nm of half-reflecting half mirror reflects fully, and the back light from CD 6 is reflected fully.Cylindrical mirror 9 plays beam shaping, the ellipse light spot of laser can be become circular light spot.Optical head compatibility shown in Figure 1 has the HDDVD CD of the about 15G recording density of 0.6mm thickness and has the DVD CD of 0.6mm thickness, is further improved the CD CD that can also read to have 1.2mm thickness.

The example of optical data with optical head of said structure is shown in table 1:

Table 1

Title	Radius-of-curvature	Thickness (cm)	Material	Radius (cm)
					Collimation minute surface 1	∞	0.25	BK7	1.5
Collimation minute surface 2	-8.1	1.0		1.5
					Object lens face 1	2.875967	3.3888	M-BACD5N	1.5
Object lens face 2	-1.624374	1.186		1.5
					CD	∞	0.6	PC	0.3

Design parameter with pentagonal prism 3 of the utility model said structure is: A=4mm, B=4.5mm, θ=22.5 °, =45 °, light comes back reflective twice in prism, walked (2+ ) A=13.656mm, played the effect of shortening the optical head size, as shown in Figure 3, wherein 3 (a) are perspective views, and 3 (b) are front views.

Two surfaces with aspheric surface object lens 5 of the utility model said structure all are aspheric surfaces, and its radius-of-curvature is about 2.88mm, and center thickness is 1.39mm.The material that it adopts is M-BACD5N, and refractive index is 1.586, and Abbe number is 61.3; The numerical aperture that adopts is 0.65, can satisfy the needs of two kinds of wavelength simultaneously.Focal length is about 1.9mm, and operating distance is WD=1.186mm, external diameter Φ=1.5mm.Adopt aspheric surface object lens to have the advantages that size is little, in light weight, numerical aperture is big, can also effectively eliminate spherical aberration in addition, make picture element reach diffraction limit, satisfy the requirement of reading CD signal.

The aspheric surface of described object lens 5 is determined by following equation and parameter:

$z=\frac{{\mathrm{<figure-callout\; id="2"\; label="cr"\; filenames="Y20062004753100091.png"\; state="\{\{state\}\}">cr</figure-callout>}}^2}{1+\sqrt{1-(1+k)c^2{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="Y20062004753100091.png"\; state="\{\{state\}\}">r</figure-callout>}}^2}}+{\mathrm{\&alpha;}}_1{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="Y20062004753100091.png"\; state="\{\{state\}\}">r</figure-callout>}}^2+a_2{\mathrm{<figure-callout\; id="4"\; label="r"\; filenames="Y20062004753100091.png"\; state="\{\{state\}\}">r</figure-callout>}}^4{\mathrm{\&alpha;}}_3{\mathrm{<figure-callout\; id="6"\; label="r"\; filenames="Y20062004753100091.png"\; state="\{\{state\}\}">r</figure-callout>}}^6+{\mathrm{\&alpha;}}_4{\mathrm{<figure-callout\; id="8"\; label="r"\; filenames="Y20062004753100091.png"\; state="\{\{state\}\}">r</figure-callout>}}^8+{\mathrm{\&alpha;}}_5{\mathrm{<figure-callout\; id="10"\; label="r"\; filenames="Y20062004753100091.png"\; state="\{\{state\}\}">r</figure-callout>}}^{10}+{\mathrm{\&alpha;}}_6{\mathrm{<figure-callout\; id="12"\; label="r"\; filenames="Y20062004753100092.png"\; state="\{\{state\}\}">r</figure-callout>}}^{12}+{\mathrm{\&alpha;}}_7{\mathrm{<figure-callout\; id="14"\; label="r"\; filenames="Y20062004753100092.png"\; state="\{\{state\}\}">r</figure-callout>}}^{14}+{\mathrm{\&alpha;}}_8{\mathrm{<figure-callout\; id="16"\; label="r"\; filenames="Y20062004753100092.png"\; state="\{\{state\}\}">r</figure-callout>}}^{16}$

Wherein: c is the inverse of radius of curvature R; R is that any point is to the minor increment of Z axle on the aspheric surface object lens surface, and numerical value is determined on corresponding X-axis and the Y-axis, r ²=X ²+ Y ²K is the circular cone coefficient, and it can determine that aspheric surface is ellipsoid or hyperboloid.α ₁, α ₂, α ₃α ₈Be the high-order asphericity coefficient, they have determined the surface configuration of object lens.The object lens selected parameter is shown in table 2 in the utility model:

Table 2

Asphericity coefficient	c	k	α 1
				Aspheric surface 1	0.34771	-3.365044	0.007077
Aspheric surface 2	-0.61563	-4.449736	0.008442

A face with collimating mirror 4 of the utility model said structure is the plane, and another side is an aspheric surface, but does not have the high-order asphericity coefficient.Its effect is that to make the light beam that incides in the object lens 5 be parallel beam.Can also compensate spherical aberration in addition.This head systems adopts focusing and the servo mode that tracks, the i.e. method of astigmatism and the difference phase scheme of existing dvd system.

Reception is divided into the part of a plurality of independent opto-electronic conversion by CD 6 reflection and the photo-detector 10 that passes the incident beam of beam splitter prism 2, and normally 4, the structure of this detector 10 is commonly used for everybody, so omit the explanation to it.

Fig. 4,5,6,7 is respectively with optical design software ZEMAX analog result to this optical head under the 405nm wavelength.Fig. 4 is lateral aberration analysis chart (Ray Fan).Fig. 5 is wave aberration analysis chart (RMS ﹠amp before and after the focus; Focus).The RMS allowable value of HD dvd system is below 0.033 λ, and the focus of the present utility model RMS of place value is less than 0.001 λ, the compliance with system requirement.Fig. 6 is imaging facula analysis chart (Spot Diagram ﹠amp before and after the focus; Focus).Focus place focal spot size is the smaller the better, but it is subjected to the restriction of spherical aberration and objective aperture diffraction limit again.Fig. 7 is PSF point spread function figure.Its shows is central peak intensity on the face with a tight waist of focused beam, also is the size of the efficiency of light energy utilization.

Fig. 8 and 9 is respectively with optical design software ZEMAX analog result to this optical head under the 650nm wavelength.Fig. 8 is PSF point spread function figure.Fig. 9 is a wave front chart.Differ basic identical under analysis chart, phase of wave difference analysis figure, hot spot analysis chart etc. and the 405nm under the 650nm.This moment, the RMS value at focus place was lower than 0.003 λ, less than allowable value 0.033 λ of dvd system.As seen this optical head can well be realized the compatibility of HDDVD and DVD.For the 405nm light path, first semiconductor laser 1 is 4.05mm with the spacing of beam splitter prism 2, the spacing of aspheric surface object lens 5 and CD 6, and promptly operating distance is 1.186mm.For the 650nm light path, its most of place is shared with the 405nm light path, promptly can read the DVD CD so the HDDVD system only need change the spacing of several parts.The utility model has only changed object lens 5 to the spacing (being 1.19648) of CD 6 and the optical path length of 650nmLD7 and beam splitter prism 2 after the HDDVD system is finished optimization, realized the optimization of dvd system, and it is poor to have obtained comparatively ideal aberration and phase of wave.If make 650nm that second semiconductor laser 7 is 4.05mm with semi-transparent semi-reflecting lens 8 spacings, then the spacing between semi-transparent semi-reflecting lens 8 and the beam splitter prism 2 is 3.603758mm, so keep two semiconductor lasers in same upright position during as if assembling, only the fixed distance with half-reflecting half mirror 8 and beam splitter prism 2 can obtain compatible optical pickup.When reading the DVD CD,, can realize that the compatibility of HDDVD and DVD CD reads by the operating distance of focus servo institutional adjustment aspheric surface object lens 5.Though the utility model has been described in conjunction with the preferred embodiments, obviously the technician can make various changes to detail of the present utility model under the prerequisite of design that does not break away from appending claims and limited and scope.

In sum, the utility model has following superiority:

Add pentagonal prism in general HDDVD optical head, light path is come back reflective twice in prism, has realized long optical path with brief size, plays the effect of shortening the optical head size; Add a 650nmLD on HDDVD light path basis, the spacing of adjusting a little several parts can realize that the compatibility of HD DVD and DVD CD reads, and simplicity of design, compact conformation, function admirable. Therefore, the utility model can be effective to have some commercial potential in the optical storage product of future generation.

Claims (6)

1, a kind of micro dual wavelength optical head with compatibility, be characterised in that its formation is: contain first semiconductor laser (1) and second semiconductor laser (7), on the output light path of first semiconductor laser (1), be provided with beam splitter prism (2) successively, pentagonal prism (3), collimating mirror (4), object lens (5) constitute main optical path, CD (6) is positioned on the focal plane of described object lens (5), the laser that described second semiconductor laser (7) sends is through half-reflecting half mirror (8), after described beam splitter prism (2) reflection, enter described main optical path again, the information recording layer beam reflected of described CD (6) is returned along former road, through described object lens (5), collimating mirror (4), pentagonal prism (3), beam splitter prism (2), half-reflecting half mirror (8) and cylindrical mirror (9) are received by photo-detector (10) at last.

2, micro dual wavelength optical head with compatibility according to claim 1 is characterized in that described first semiconductor laser (1) emitted laser wavelength is 405nm, and described second semiconductor laser (7) emitted laser wavelength is 650nm; Described beam splitter prism (2) is to the complete transmission of the incident light of 405nm, and the incident light of 650nm is reflected fully, and the back light from CD (6) is reflected fully; Described half-reflecting half mirror (8) reflects fully to the incident light of 650nm, and the back light from CD (6) is reflected fully.

3, micro dual wavelength optical head with compatibility according to claim 1, the shape that it is characterized in that described pentagonal prism (3) is determined by following parameter: two right angle length of side A, both sides length of side B, side angle θ=22.5 ° is to parallactic angle =45 °.

4, micro dual wavelength optical head with compatibility according to claim 1, it is characterized in that described object lens (5) are non-spherical lens, two surfaces of this non-spherical lens all are aspheric surfaces, and its radius-of-curvature is 1.5～7mm, center thickness is 0.8～1.5mm, and numerical aperture is 0.65.

5, micro dual wavelength optical head with compatibility according to claim 1 is characterized in that a face of described collimating mirror (4) is the plane, and another side is an aspheric surface.

6,, it is characterized in that two aspheric asphericity coefficients of described object lens (5) are as follows according to each described micro dual wavelength optical head with compatibility of claim 1 to 5:

Asphericity coefficient c k α ₁

Aspheric surface 1 0.34771-3.365044 0.007077

Aspheric surface 2-0.61563-4.449736 0.008442.

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