|Title of Invention||
C-WALLS OPTICAL DRIVE
|Abstract||The present invention describes an optical drive capable of reading and writing information on a disc and non-disc type of optical media, without requiring the media to rotate. The drive comprising of a head component and a wall component; the head component rotates in the center containing an implicit linear motion with a reflecting mirror fixed at the tip of the head. The wall component is a concave shaped reflector placed along the circumference of the media at a particular angle. The drive's size and shape can be modified according to the media's size and shape, which offers flexibility for variety of designs in shaping and sizing the drive. Since the media is not going to rotate, the media wobbling will be nil and hence zero tilt. Also, the tray dust/particles will not scratch the media, which means long life for the media. Due to contraction of head assembly, which is confined to the central axis, C-Walls drive will have greater performance in accessing data, high throughput, consumes very less power, which means long battery life for hand held type of devices.|
Field of the invention
The present invention is related to an optical drive unit, which can read or write information on an optical media, without requiring the media to rotate.
Background of the invention
In conventional methods of reading/writing information on any disc type of media, the drive use two types of motion which are controlled by two different motors viz. a)spindle motor and b)traction motor. The disc rotation is in the form of circular motion, attained from the spindle motor. The head movement over the top surface of the media is linear type of motion, achieved from a traction motor and the traction motor drives the head assembly. The drive electronics controls the spindle and traction motors. An application software requests for any information required by a user that is present in the media through the device driver and the device driver activates the drive electronics to access information from the media. The Laser from the head is focused by an objective lens on to the media at the right spot.
In C-walls drive, the media does not rotate but held statically in the drive. The head component will carry both the circular and the linear motions, that are integrated in a single head assembly. This head assembly is positioned within the center hole area region without touching the media. The tubular head assembly will rotate on its own axis with an implicit linear motion carrying a reflector that moves vertically up and down. The timing and control of the angular and linear movements of the head assembly will be taken care by the drive electronics.
The Laser from the source is of a coUimated, circular polarized beam. A concave wall along the circumference of the optical drive is formed at a particular angle. The concave wall converge the incident light to its focal point where a photo diode is placed to receive the light.
Objective of the invention
The objective of the current invention is to produce optical drives that can read or write information on different types of media, without the need to rotate the media. As the required rotary and linear motions by a drive are integrated in a single tubular head assembly, this optical drive will have higher access speed and hence perfomance improvement over the current type of optical drives. It will further help to reduce power consumption and therefore increases running time of battery in hand held type of devices. With the help of this new technology, optical drives can
be custom-built of desired size and shape according to different size and shape of media.
Brief description of the diagrams
Fig. 1A illustrates the Laser path inside the C-Walls drive. Insert il explains the angle formation by the Laser when it changes its path after reflection. Insert i2 explain the placement of the reflector inside the head assembly. Insert i3 explains the law of reflection by the Laser whenever it meets a reflecting surface.
Fig. IB illustrates the reflector at different heights and how the Laser path changes accordingly.
Fig. 2A shows the 3D view of the C-Walls drive with the Laser hitting a spot in the media and then follows towards the concave walls.
Fig. 2B shows the prior view of Fig 2A, but the angle of the head assembly is rotated by 0 degrees and hence changes in the Laser path.
Fig. 2C illustrates that the drive supports a non circular media, but the write happens in circular patterns as in conventional media.
Fig. 3A illustrates the change in beam profile between the conventional drive and the current invention.
Fig. 4A shows the tubular head assembly with its intemal reflector placement.
Fig. 4B shows the closer view of the tubular head assembly, which has a vertical window through which the Laser comes out of the head assembly.
Fig. 4C illustrates the Laser light hitting the media after hitting the reflector on the head assembly.
Fig. 5A indicates the principle behind a concave mirror.
Fig. 5B shows how the concave wall is placed in C-Walls. It depicts the necessary angle of placement of the concave reflector.
Fig. 5C illustrates the semi sectored concave wall, wherein the non-requisite portion of the concave reflector is removed.
Fig. 5D1 illustrates the formation of concave walls.
Fig. 5D2 illustrates the required portion of the concave walls that is depicted in Fig. 5D1.
Fig. 5E1 illustrates the fully formed concave walls.
Fig. 5E2 exhibits the concave walls with media and head assembly.
Fig. 6A indicates the refraction of Laser while it interfere the media. Insert il, shows the angle of refraction that is defined by Snell's law. Insert i2, exhibits the displacement that is needed by the Laser to hit the exact spot in the medium.
Fig. 6B illustrates the effect of refraction depending on the height of the polycarbonate material used in different types of media. Insert il, shows the Laser hitting a track on the media. Insert 12, exhibits the Laser interference on a ROM type of media, whereas insert i3 shows the Laser interference on a Read/Write type of media.
Fig. 6C1 illustrates grooved type of media, in which the recording layer with recording marks in both the Land area and Groove area are shown.
Fig. 6C2 illustrates how a re-collimated Laser interferes with the aforementioned Lands and Grooves. The insert il shows the critical angle of interference of Laser beam.
Detailed description of the invention
Figure lA consists of a main diagram with three inserts namely il, i2 and i3. These three inserts are part of the main diagram but need separate explanation, as they are all are placed within Fig 1 A. Referring to Fig lA, 4 is the media, R is the radius of the media and r is the radius of the center hole of the media. To read information from spot S on the media 4, Laser source 1 beams collimated Laser light 6 towards the reflecting mirror 2. The reflected Laser light 6A makes an angle θrl with the incident light 6 following the Law of reflection, which states "The angle of incidence light is equal to the angle of reflected light". This reflected beam 6A hits the spot S in the media in the radial direction of the media at an angle θi2 with the media.
For example, 9r]=70° for a 2cm height drive and 6cm of media radius; 6rl is so chosen that by altering the height of the mirror 2 the entire radius of the media is covered to read/write information on different tracks. So, knowing the dimensions of the media i.e. the radius of the media and height of the head assembly, θrl may be derived from
tanθrl = Radius of the media/height of the head assembly (tan6=opp/adj),
height of the head assembly - when the reflector reaches the peak height inside the head assembly.
Insert il shows that the incident Laser 6, reflected Laser 6A and the plane of the media 4, form a right angled triangle. If θrl=70° then θrl=20°, as the sum of the angles in a triangle is =180°.
Assuming the Laser beam 6A hits a perfect reflective surface at spot S in the media 4, it will reflect meeting the Law of reflection.
This is shown in the insert i3, where 6A is the incident beam making an angle i(i==70°, as θi2 =20°) with the Normal N. Since the angle of incidence is equal to angle of reflection, i= r=70°, θr2 will be 20°.
Coming back to the main figure 1 A, the reflected Laser light 6B, making an angle 0,2 with the media 4, will be incident on the Concave walls 3 at point P. Laser beam 6C, which is reflected from the Concave walls 3, will converge at the focal point of the Concave reflecting wall, where a photo diode 5 is positioned to detect the light changes reflected from the media.
Insert i2 explains the positioning of the reflecting mirror 2 with respect to the horizontal plane of axis. The placement angle D of this reflecting mirror 2 plays a significant role in deciding the required angle θrl(θrl/2+ θrl/2). Thus, by altering the height of the reflecting mirror 2, the reflected Laser beam 6A could cover the entire length of the radius of the media and hence n number of tracks that are present in the media. The reflected Laser 6A makes an angle 9rl with the incident Laser 6 at point e on the reflecting mirror 2. A normal N is drawn perpendicular to the mirror 2 at point e. Since the angle of incidence is equal to the angle of reflection, θrl is divided into two equal half angles as θrl/2 and θrl/2. In our example θrl=70°, then θrl/2=35°. From this E=90-θrl/2, i.e.90-35=55°. As dfe is a right angled triangle, D=90-E, i.e. 90-55=35° which is equal to θrl/2. So, the reflecting mirror 2 has to be placed in angle D with respect to horizontal plane of axis while the plane of the reflecting mirror 2 facing the media 4.
To access the entire radius of the media, the height of the reflecting mirror 2 is altered. In Fig IB, the Laser 6 is incident on the reflecting mirror 2A. This is when the height of the mirror is at the lower position, thus Laser 6 making an angle 9rl with the Laser 6A will hit the spot S1 in the media 4. The reflected Laser beam 6B from the spot S1 will hit the point PI in the concave walls 3. The concave wall converges the Laser 6C to it's focal point, where the photo diode 5 is placed. When
the height of the reflecting mirror 2 is increased, shown as 2B, Laser beam 7 strikes at it and reflected towards the spot S2. Then the Laser beam 7B gets reflected to the point P2 in the concave walls 3. Laser beam 7C will again get converged to the focal point 5. Similarly, when the reflecting mirror's 2C height is increased further Laser beam 8 will follow the path 8A, S3, SB, P3, 8C then reaches point 5. S3 and P3 are points in the media 4 and concave wall 3 respectively. It clearly shows that when the height of the reflecting mirror is closer to the axis point 1, the Laser beam hits the surface of the media closer to the center and then in the concave wall at the highest point. When the reflecting mirror is altered to the highest position, the Laser beam hits the surface of the media near it's circumference and then in the concave wall at the lowest point. In all the instances, the Laser beams are converged to the focal point of the concave mirror making an angle θr3 with the incident beam.
Figure 2A depicts the 3D view of the drive, shown transparent, it is surrounded by concave wall 3 along the entire circumference. The tubular head assembly 7 is placed at the center with the reflecting mirror 2 inside the head assembly. Laser beam 6 hosted from the source 1 hits the reflecting piece of mirror 2, which reflects the Laser 6A towards the media 4 at spot S. The reflected Laser 6B from the media meets the concave wall 3 at point P. Laser 6B is parallel to the principle axis of the concave walls along the radial plane 8. Laser 6C gets converged to the photo diode 5.
Figure 2B shows when the tubular head assembly 7 is rotated by an angle 9, the Laser 6A will hit a different spot SI in the media 4. Still the convergence of the Laser beam 6C will happen at the photo diode 5.
Referring to the figure 2C, the circular shape media is replaced with a square shape media. The important thing to be noted here is the recording layer, which is circular immaterial of the shape of the media, denotes that whatever the shape of the media be, the recording happens only in arcs.
In conventional methods, referring to figure 3A, to read or write information in optical drives, the Laser beam LI is focused through the substrate on to the medium 4 using an objective lens O and the convergence of the beam L2 happens at the focal point of the objective lens. The concentration of light will be high at the focal point S that follows the Gaussian profile of the beam. The distance of the light focusing on the medium is determined by the NA(Numerical Aperture) of the objective lens and the wave length of the Laser beam The objective lens has to be closer to the medium not just only because of the beam focus on to the medium but
also to gather the divergent light that is reflected back by the medium. A collimated beam will not diverge quickly but a converged beam upon reflection or after the beam waist/focal point will diverge very quickly. As the photo sensor(that converts light energy to electrical energy) has to get maximum percentage of the reflected light, the objective lens has to be very nearer to the medium, the higher the NA the closer the lens to the medium.
Whereas, in C-Walls method, refer figure 3B, the beam profile is modified that uses a re-collimated Laser beam L3 of thickness of the spot size S. Laser LI is by itself a collimated Laser but of larger thickness. Hence to reduce the thickness of the Laser beam LI, the beam is first converged using a converging lens CI and the converged Laser L2 is re-collimated using collimator Cr, which is directed towards the media 4 at spot S. The change in beam profile by using collimated beam rather than a convergent beam is necessary because of the variation in distance at every instance of reads and writes between the head and the medium. This is the major difference between the C-Walls and the conventional drives, as in the conventional drives the distance is maintained constant between the head and the medium.
Figure 4 A depicts the placement of the head assembly 1 at the center hole of diameter d on media 4 having diameter D. A spindle motor takes on the rotation of the head assembly 1 as a whole and the vertical movement of the reflector 2 is taken care by an inbuilt traction motor. Figure 4B shows, the tubular head assembly 1 with its central axis 3 having a vertical window 2 through which the Laser will come out of the head assembly. Figure 4C shows the head assembly containing the reflecting mirror 2, which moves up and down to make the Laser 6A to hit different spots at different tracks on the media 4. When the head assembly is rotated by and angle 9, the Laser 6A will move over the same track until the height of the reflecting mirror 2 is adjusted.
Figure 5 A shows the concave walls 3 placed along the circumference of the media 4, in which OX is the diameter of the media and DD' is the data area. PQX is the concave wall taking the radial plane along the media into consideration. RQ is the radius of the concave wall with R as its center C. PA is the principle axis of the concave wall that makes an angle θpA with the media 4. The center of curvature CC of the concave wall is at point Q, whereas the focal point FP, which is the midpoint on the principle axis, is at point O, which means RO is equal to OQ. The portion RO is imaginary and so it is shown as dotted line, but is quite important in determining the radius of concave wall.
Figure 5B depicts the principle behind the erection of concave walls 3. Laser 6A pitches at point B on the media 4, so that AB makes an angle θi2 with the media 4. BC is the reflected Laser 6B from the media making an angle θr2. As the angle, θrl, made by the reflected Laser beam 6B with the surface of the media is equal to the angle, θpA , made by the principle axis PA of the concave wall 3, Laser BC will be parallel to the principle axis QR. A property of concave mirror; while a light ray is parallel to the principle axis of a concave mirror, the beam will converge at it's focal point. Hence Laser 6C will converge at the point O, where a photo diode is kept to receive this Laser. As it can be seen from the figure 5B, Laser 6B will always be parallel to the principle axis of the concave walls and Laser 6B is essentially not required to hit any spots in the media beyond the data area D, clearly indicating that points BC will never touch the imaginary points OQ(principle axis). When the Laser 6B is undoubtedly not going to hit the concave wall beyond point Q, the portion PQ of the concave walls can be removed as shown in figure 5C. By removing portion PQ, the material used for building the concave wall, which surrounds the entire drive, can be saved. The height of the concave wall will also not protrude out of the drive, limiting itself to lower levels. So it can be termed as semi-sectored concave walls, as only half of it is put to use.
The issue of spherical aberration, reflective of a defect in concave mirrors; states that light rays incident far away from the center of curvature CC - refer figure 5 A, may not perfectly converge to its focal point. But this spherical aberration will not affect C-Walls, as the Lasers incident on the C-Walls are not far away from the center of curvature. The maximum point of reach will not go beyond point X that is close to the plane of the media.
Figures 5 A, 5B, and 5C explain the formation of Concave Wall for a single plane. Referring to Fig. 5D1, which illustrates the formation of C-Walls along the entire circumference of the media, with C as the center, and CQ as radius, a sector plane CPX is formed perpendicular to the surface plane of the media. O as its focal point, which is at the mid point on the hne CQ, and Q is center of curvature of the concave wall PX. The media DD', which is the radius of the media, is placed exactly along the center plane of the concave wall - which means the center point of the media meets the focal point of the concave wall, then only the Laser beams that are reflected from the concave wall will converge at focal point O. Similarly, CI, C2,
C3 Cn are the center points for each n number of planes with respective points
of Center of curvatures Ql, Q2, Q3 Qn. For all these n planes the focal point O is
common. When all these points of the centers and center of curvatures of the concave wall are joined, two imaginary circles are formed. A full-sectored concave wall for a single plane is shown as PX, whereas a semi-sectored concave wall for a single plane with the portion QX is shown in Fig. 5D2. DD' is the media. Wlien the
concave wall is extended for n number of parallel planes along the circumference of the media, the formation looks like the figure shown in Fig 5E1. The fully formed concave walls should have its internal surface reflecting. Fig. 5E2 depicts the concave walls with both media and head assembly present.
When a Laser enters from one medium to another, the beam will refract, and due to refraction of Laser beam, there will be a displacement d, hitting the spot on the medium. This is explained in figure 6A, where Laser 6A enters the poly carbonate material of the media 4 having thickness of 4a with recording layer of thickness 4b. After entering the polycarbonate material, the Laser 6A refracts and hits the media 4 at spot SL Had the refraction not taken place, the Laser 6A would have retraced 6 A A, hitting the spot S2 and reflecting as Laser 6BB. The refracted Laser 6a hits the spot SI and get reflected. Reflected Laser 6b again refracts while leaving the polycarbonate material and passes away as Laser 6B.
The change in angle of the Laser beam due to refraction, and the displacement of the target spot of the Laser beam on the media due to refraction, are explained in the inserts il and i2 respectively in figure 6A. Insert il shows the refraction due to the Laser traveling from air medium to polycarbonate medium. Snell's Law gives the angular change of light rays when passed from one medium to another. It states that n2/nl=sin i/sin r, where nl is the refractive index of air medium and n2 is the refractive index of the polycarbonate medium, i is the angle made by the incident Laser 6A with the normal N and r is the angle made by the reflected Laser 6a with the normal N.
In our example we have seen θi2 as 20° and so i becomes 70°. Refractive index of Laser in air is 1 and that of in polycarbonate is 1.55.
So, from Snell's law,
n2/nl = sin i/sin r, angle r can be found out.
nl * sin 70 = n2 * sin r,
l*sin 70 ^ 1.55*sin r,
The displacement of Laser hitting the spot can be determined from insert i2. If the actual spot o has to be reached by the Laser, then Laser 6A should be focused at point m so that the refracted Laser 6a will hit the recording layer 4b at the target point o. The displacement of Laser hitting the polycarbonate depends on the height h of the polycarbonate material.
mn = h, i.e. height of the polycarbonate.
angle r is the angle made by the Laser 6a with the line perpendicular to the polycarbonate.
no = d, i.e. the distance between the perpendicular line drawn at the point of contact of Laser 6A with the polycarbonate when extended to point n and the actual spot o.
Now tan 9 = opp/adj, i.e. tan r = d/h
Hence, displacement d = h * tan r
For a polycarbonate having height h 0.9mm, and angle r =37.32°, displacement d can be calculated as d = 0.99 * tan 37.32° = 0.75mm.
To understand how the Laser beam interacts with different types of media, refer figure 6B. The Laser beams 6A, 6B outside the polycarbonate 4 of having thickness 4a are common for all types of media, but the interactivity of Laser differs in the recording layer between a ROM type of media and a writable/re-writable types of media. Insert il shows incident Laser 6A hitting a track on a media and reflects as Laser 6B. Insert i2 shows a ROM type of media, which contains pits and lands on a track. On the Laser side of the media, the pits are termed as bumps. Different types of ROM media, like CDROM, DVD ROM, will have different pit configurations. Each bump will have definite length 1, width w, and height h. The edges e of the bumps will create Laser transitions, and these transitions are sensed by a photo diode to create a series of 0s and Is. These 0s and Is are demodulated, reconstructed by the software to form human readable information. Laser 6a hits the bump across the width w on a track. When train of Lasers hitting a track, it comes across several bumps and Lands and when the Laser hits a bump it reflects as 6b and when it meet the edges the reflections will vary. The reflected Laser 6b will then hit the concave wall and converges to its focal point where a photo diode is placed to check the Laser transitions. Insert i3 shows a writable/rewritable type of media in which c is the crystalline portion and a is the amorphous portion. When Laser 6a strikes c it will be reflected as 6b. If the Laser 6a strikes a it will be deflected, as amorphous portion will not have regular surface. The length 1 and width w of these crystalline and amorphous portions in a track is shown in the figure. Strong Lasers are used to change the crystalline structure to amorphous ones in the recording layer on the media and this is termed as writing/buming a RW type of media.
Higher storage capacity media uses land groove concept to accommodate more data, i.e. the space in-between two lands, a grove is formed in the recording layer of the media. Both land and groove carry tracks to record information. It is obvious that the pit size shrinks in high storage media. Now to understand how C-Walls address these lands and grooves configuration, refer figures 6C1 and 6C2. In Fig. 6C1, land L and groove G have same width. The depth of the groove G from the
surface of the media is d in nanometers, usually, a fraction of the wavelength of the Laser used. The recorded marks M in both lands and grooves are shown. In conventional drives the Laser L will be incident I on the media, but the convergence differs between a land and a groove as the depth differs. Whereas, C-Walls uses re-collimated Laser beam 6A incident on the recording medium. Fig. 6C2 illustrates that the incident and reflected Laser beams does not touch the walls of the groove,
which is quite important to consider. Grooves Gl, G2 Gn and Lands LI,
L2 Ln are alternately formed along the radius of a media. These Lands and
Grooves will have same width W, whereas the Grooves will have a depth d. At the Laser side the Lands are seen as having depth d and the Land walls will have edges e. The refracted Laser beam 6a, inside the polycarbonate material, is incident at the spot S on the recording medium and then reflects as Laser beam 6b. The angle between the incident Laser and reflected Laser is 2r. Insert il illustrates the critical angle taking a single Land along the track direction for explanation purpose. On the Laser side the Land is at higher depth than the Groove. Laser 6a is incident at spot S, which is exactly the mid point on the width of Land, making an angle 02 with the surface of the Land. After hitting the spot S, assuming the Laser has hit a definite surface(as these Lands by itself a track containing pits and lands), it reflects as Laser 6b. The distance between the spot and the edge of the Land wall is width/2, i.e. W/2. When a line is drawn connecting the edge e of the Land and the spot S, it makes an angle 0] with the surface of the Land. Now, the critical angle 9c is defined as the difference between 62 and 0i, which should never be zero, otherwise the incident Laser or reflected Laser will touch the edges of the walls of the Lands causing undesirable operation.
θc=θ2 - θ1, and θ2 > θ1, which should be positive angle.
θ2 - the angle made by the Laser with the surface of the Land
θ1 - the angle made by the hypotenuse with the surface of the Land
In our example, referring to page 9,
AVhen r = 37.32°, θ2 will be 52.68°
To know θ1, we should know the pit configuration of a media that uses Land Groove. A typical DVD will have a depth d of a Land of about a fraction of the wave length λ of the Laser that is used. Assuming λ = 600nm, d == λ /6 -600/6=100nm. If the Width W of the Land is - 0.6µm, W/2=0.3µm.
Now to calculate θ1, tan θ1= depth / half-width of the Land, tan θ1.100 nm/0.3µm, θ1,. 18.43°.
As θc.θ2 - θ1, 52.68°- 18.43°- 34.24° , which is very much in the limits of the critical angle. So, it proves that the Laser beam can enter a Land/Groove and return without any hassle.
C-Walls, an innovation, can improve upon the current technology in optical drive systems. It has a great potential as it offers flexibility for designing of desired shapes and sizes of drives according to the needs. C-Walls will have high performance in accessing information. C-Walls will benefit the IT industry as it supports multiple formats on a single drive and it assures to qualify for a better optical storage system. C-Walls is echo friendly as the noise produced by the drive will be very minimal and the quality of the media will last long as the media in the drive will not rotate. Due to the same reason the fan out will be nil and hence reduction in sound output, can be assured.
1. C-Walls provides a method for reading and writing information on an optical media without requiring the media to rotate. The Laser is beamed from the source at a particular angle on the media by the head and depending on the reflective surface at that spot, the Laser will be reflected. The C-Walls drive is surrounded internally by concave shaped reflecting mirror. When the reflected Laser from the media hits the concave mirror, it converges at the focal point of the concave mirror. At the focal point an arrangement is made to detect the light changes that are reflected by the concave mirror.
2. The method mentioned in Claim 1, where in a provision of tubular head assembly containing an internal reflector with an implicit linear motion, is obtained from a traction motor that is inbuilt into the head assembly, thereby achieving Lasers to reach entire radial lengths.
3. The method mentioned in Claim 1, where in the provision of tubular head assembly rotates on its own axis, using a spindle motor, in such a way the Laser beam that is reflected from the internal reflector mentioned in the Claim 2 covers the entire area on the media by changing the angle of rotation of the tubular head assembly combined with the method mentioned in Claim 2.
4. The provision mentioned in Claim 2, where in the positioning of the reflector inside tubular head assembly at a particular angle.
5. The method mentioned in Claim 1, where in a provision of concave shaped wall along the circumference of the media. The media being any definite shape or size but the recording shape in the medium will only be in arcs or
6. The provision mentioned in Claim 5, where in the positioning of the concave
wall at a particular angle in which the principle axis of the concave wall is
parallel to the line of Laser reflected from the media.
7. The method mentioned in Claim 1, where in a provision of C-Walls supports
R, R/W types of media that is achieved by changing the intensity of the Laser
8. The method mentioned in Claim 1, where in a provision of C-Walls
supporting multiple formats of media by changing the wavelength of the
9. The method mentioned in Claim 1, where in a provision of stacking multiple
media on a single host drive thereby achieving simultaneous burning of
multiple optical media by using the scope of the method.
|Indian Patent Application Number||118/CHE/2006|
|PG Journal Number||17/2012|
|Date of Filing||25-Jan-2006|
|Name of Patentee||V. NARAYANAN|
|Applicant Address||NO.23/3, PLOT 99/B, KULASEKARAN STREET, SUNDARAM COLONY, EAST TAMBARAM, CHENNAI-600 059|
|PCT International Classification Number||H01S 001/00|
|PCT International Application Number||N/A|
|PCT International Filing date|