JP4038012B2 - Light source device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light source device mounted on an optical pickup that collects light emitted from a light source module on an optical disk and records / reproduces information.
[0002]
[Prior art]
Conventionally, a three-beam detection method is generally employed as a tracking error detection method used in a read-only optical disc apparatus. In an optical disc apparatus having a recording function, a differential push-pull detection method is generally employed as a tracking error detection method. Both detection methods irradiate the sides of the main spot on the optical disc with a side spot that is a predetermined distance away, and calculate the signal obtained from the reflected light from the side spot or the reflected light from the side spot and the main spot. Thus, an offset of the tracking error signal is prevented.
[0003]
On the other hand, there is an optical pickup having a configuration in which the laser light source and the light receiving element are housed in one package and the reflected light from the optical disk is guided to the light receiving element by the hologram element, which is advantageous for improving the reliability and reducing the cost. It has already been widely adopted in ROM playback devices.
[0004]
In addition, in CD / DVD playback devices that require two types of light sources, products that have two light sources and a light receiving element in a single package and that have a simplified configuration have begun to appear.
[0005]
With respect to the above technique, JP-A-10-105999, JP-A-2000-20997, JP-A-2000-132862, and the like have been proposed.
[0006]
[Problems to be solved by the invention]
However, in the configuration in which the two light sources and the light receiving element are housed in one package, since the emitted light from the two light emitting points is condensed at different positions on the optical disc, a tracking error using side spots is used. It is difficult to adopt the detection method for both light sources. This is because the diffraction grating that divides the emitted light into three is common to the two light sources, and the side spot position cannot be adjusted separately for the two light sources.
[0007]
An object of the present invention is to provide a light source device that solves the above-mentioned conventional problems and makes it possible to apply a three-beam method and a differential push-pull method as a tracking error detection method to light emitted from different light emitting points. There is.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is directed to a light source device mounted on an optical pickup that collects light emitted from a light source module on an optical disk to record / reproduce information, and the light source module A plurality of light emitting points are installed in each of the light emitting points, and the positions of the respective light emitting points are set so that the respective condensing points on the optical disk corresponding to the respective light emitting points are arranged in the radial direction of the optical disk. Since the condensing point on the optical disk is set so as to be shifted in the radial direction by each light emitting point, the optimum arrangement direction of the main spot and the side spot in the differential push-pull method or the three beam method is the same at each light emitting point. can do.
[0009]
According to a second aspect of the present invention, the optical pickup in the optical disc apparatus in which the light picked up from the light source module is condensed on the optical disc and the information is recorded / reproduced is conveyed in the radial direction of the optical disc by the coarse movement mechanism. In the light source device mounted on the light source module, each light emitting point is arranged such that a plurality of light emitting points are installed in the light source module, and each light condensing point on the optical disk corresponding to each light emitting point is arranged in the transport direction of the coarse movement mechanism. and wherein the position that was set in by this configuration, the focal point on the optical disk is set to be höðr seek direction (conveying direction of the coarse adjustment mechanism) by the light emitting points, the differential push-pull method In the three-beam method, the setting that minimizes the fluctuation due to the seek operation of the tracking error signal can be made the same at each light emitting point.
[0010]
According to a third aspect of the present invention, in the light source device according to the first or second aspect of the present invention, diffraction that divides the light emitted from the light source module so as to irradiate the optical disc with three or more condensing points for each light emitting point. With this configuration, a side spot in the differential push-pull method or the three-beam method can be easily generated by the diffraction grating, and the side spot generating means is shared by each light emitting point. be able to.
[0011]
According to a fourth aspect of the present invention, in the light source device according to the third aspect, the diffraction grating is fixed to the light source module. With this configuration, the diffraction grating for splitting the emitted light beam is fixed to the light source module. Stable characteristics are obtained that are hardly affected by changes over time and temperature.
[0012]
The invention according to claim 5 is characterized in that, in the light source device according to any one of claims 1 to 4, the wavelength of the emitted light from each light emitting point is set to be different. By switching, it becomes possible to cope with a plurality of types of optical disks having different use wavelengths.
[0013]
According to a sixth aspect of the present invention, in the light source device according to any one of the third to fifth aspects, the interval between spots on the optical disk formed by the nth light emitting point is Bn, and the optical disk whose target is the nth light emitting point. The track pitch of Tn, the constant that is a natural number depending on the light emitting point is Kn, and the constant that is a constant value regardless of the light emitting point is θ, for all the light emitting points, Bn × sin θ≈Tn × (2 × Kn -1) / 2 The diffraction grating is set so as to satisfy the equation, and with this configuration, the side spot generation condition corresponds to a plurality of combinations of the used wavelength and the track pitch, and for the differential push-pull method. Therefore, it is possible to deal with a plurality of types of optical disks having different operating wavelengths and track pitches by switching the light emitting points by the differential push-pull method.
[0014]
According to a seventh aspect of the present invention, in the light source device according to any one of the third to fifth aspects, an optical disc in which the interval between spots on the optical disc formed by the nth light emitting point is Bn and the nth light emitting point is a target. The track pitch of Tn, the constant that is a natural number depending on the light emitting point is Kn, and the constant that is a constant value regardless of the light emitting point is θ, for all the light emitting points, Bn × sin θ≈Tn × (2 × Kn -1) The diffraction grating is set so as to satisfy the expression / 4, and this configuration allows the side spot generation conditions to be set for the three-beam method corresponding to a plurality of combinations of operating wavelength and track pitch. Therefore, by switching the light emitting points, it is possible to cope with a plurality of types of optical disks having different operating wavelengths and track pitches by the three beam method.
[0015]
According to an eighth aspect of the present invention, in the light source device according to any one of the third to fifth aspects, an optical disc in which an interval between spots on the optical disc formed by the nth light emitting point is Bn and the nth light emitting point is an object. The track pitch of Tn, the constant that is a natural number depending on the light emitting point is Kn, and the constant that is a constant value regardless of the light emitting point is θ, for all the light emitting points, Bn × sin θ≈Tn × (2 × Kn −1) / 2, or Bn × sin θ≈Tn × (2 × Kn−1) / 4, and the diffraction grating is set so as to satisfy either of the formulas. Since it is set corresponding to multiple combinations of operating wavelength, track pitch, and tracking error detection method, the operating wavelength, track pitch, and tracking error are detected by switching the light emission point. It may correspond to a plurality of types of optical discs having different law.
[0016]
According to a ninth aspect of the present invention, in the light source device according to any one of the third to fifth aspects of the present invention, the interval between spots on the optical disk formed by the nth light emitting point is Bn, and the optical disk whose target is the nth light emitting point. Is a constant that is a natural number that varies depending on the light emitting point, and θ is a constant that has a constant value regardless of the light emitting point. For all the light emitting points, the equation of Bn × sin θ ≠ Tn × Kn is obtained. Since the diffraction grating is set so as to satisfy this condition, the side spot generation condition is set for the differential push-pull method corresponding to a plurality of combinations of the used wavelength and the track pitch. By switching the, it is possible to cope with a plurality of types of optical disks having different operating wavelengths and track pitches by the differential push-pull method.
[0017]
According to a tenth aspect of the present invention, there is provided the light source device according to any one of the third to fifth aspects, wherein an interval between spots on the optical disk formed by the nth light emitting point is Bn, and the optical disk targeted for the nth light emitting point. The track pitch of Tn, the constant that is a natural number depending on the light emitting point is Kn, and the constant that is a constant value regardless of the light emitting point is θ, and for each light emitting point, Bn × sin θ ≠ Tn × Kn / 2. The diffraction grating is set so as to satisfy the equation. With this configuration, the side spot generation conditions are set for the three-beam method corresponding to a plurality of combinations of the used wavelength and the track pitch. By switching the, it is possible to deal with a plurality of types of optical disks having different operating wavelengths and track pitches by the three beam method.
[0018]
According to an eleventh aspect of the present invention, in the light source device according to any one of the third to fifth aspects, an optical disc in which an interval between spots on the optical disc formed by the nth light emitting point is Bn and the nth light emitting point is an object. The track pitch of Tn, the constant that is a natural number depending on the light emitting point is Kn, and the constant that is a constant value regardless of the light emitting point is θ, Bn × sin θ ≠ Tn × Kn or Bn for all the light emitting points. The diffraction grating is set so as to satisfy any one of the formulas of x sin θ ≠ Tn × Kn / 2. With this configuration, the side spot generation condition includes a plurality of combinations of a used wavelength, a track pitch, and a tracking error detection method. Since it is set according to the light source, multiple types of light with different operating wavelengths, track pitches, and tracking error detection methods can be obtained by switching the light emission point. It is possible to correspond to the disk.
[0019]
The invention according to claim 12 is the light source device according to any one of claims 6 to 11, wherein the angle formed by the arrangement direction of the light emitting points and the grating direction of the diffraction grating is the θ, Depending on the configuration, the grating direction of the diffraction grating is set to a predetermined direction with respect to the arrangement direction of the light emitting points. Therefore, the diffraction grating is fixed to the light source module and then rotated together with the light source module, and the condensing point arrangement direction on the optical disc In addition, the deviation of the condensing point on the optical disk due to the light emitting point can be made radial.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below with reference to the drawings.
[0021]
FIG. 1 is a perspective view showing an optical pickup for explaining an embodiment of the present invention. A light source module 2, a coupling lens 3 and a rising mirror 4 are fixed in a housing 1, and an objective lens 5 is shown. Are installed to be movable in the x-axis direction (radial direction of the optical disc D: tracking direction) and z-direction (focusing direction) by an electromagnetic drive system (not shown).
[0022]
The light source module 2 includes a first light source 6, a second light source 7, and a light receiving element 8 that are a plurality of (two in this example) light emitting points, and the first light source 6 and the second light source 7. Are arranged in the x-axis direction. The position of the hologram element 9 and the diffraction grating 10 can be adjusted with respect to the light source module 2 and is fixed to the housing 1 or the light source module 2 after adjustment. The housing 1 is supported by a coarse movement mechanism (not shown) so as to be movable in the seek direction (x direction). By moving in the x direction, the position of the objective lens 5 moves in the radial direction of the optical disc D. ing.
[0023]
The light emitted from both light sources 6 and 7 in the y-axis direction is transmitted through the hologram element 9 and the diffraction grating 10, respectively, and the degree of divergence is changed by the coupling lens 3, and the recording surface of the disk D by the rising mirror 4 It is deflected in the direction (z direction), enters the objective lens 5, and is condensed on the recording surface of the optical disc D. When passing through the diffraction grating 10, the light beam is divided into three light beams of zero-order light, + 1st-order light, and −1st-order light, and there are three condensing points for one light source on the recording surface of the optical disc D. .
[0024]
Then, the three condensing points on the optical disk D are reflected by the optical disk D and follow the opposite optical path, and are divided and diffracted by the hologram element 9, and are branched from the optical path toward the light sources 6 and 7 to receive light. The light enters the element 8. The light receiving element 8 photoelectrically converts the reflected light and outputs a focus error signal, a tracking error signal, and a recording signal.
[0025]
FIG. 2 is an explanatory diagram showing the position of the condensing point on the optical disc D in FIG. 1, and the condensing point of the 0th order light emitted from the first light source 6 and transmitted through the diffraction grating 10 is M1 and + 1st order light. The condensing point is S1 +, and the condensing point of −1st order light is S1−. The condensing points S1 +, M1, and S1- are in series and form a slight angle with the track direction of the optical disc D, and the two side spots (S1 +, S1-) are both 1/2 Tp (track pitch) from the main spot (M1). The grating direction of the diffraction grating 10 is adjusted so as to be located at a shifted position. Such a condensing point arrangement enables tracking error signal detection by the differential push-pull method.
[0026]
On the other hand, since the second light source 7 is installed side by side with the one light source 6 in the x-axis direction, the three light condensing points (S2 +, M2, S2-) on the optical disk D by the second light source 7 are the first. Each of the light sources 6 is condensed at a position shifted by an equal distance from the three condensing points (S1 +, M1, S1-) in the x direction. Therefore, the tracking error signal can be detected by the differential push-pull method also using the three light condensing points (S2 +, M2, S2-) on the optical disc D by the second light source 7.
[0027]
FIG. 3 is also an explanatory diagram showing the focal point position on the optical disc D in FIG. 1, and the main spot (M1) is located on the radius of the optical disc D in FIG. In the differential push-pull method, it is desirable that the main spot (M1) always moves along the same radius. However, in practice, due to an error or the like, the main spot (M1) is always on the same radius from the innermost circumference to the outermost circumference. It is difficult to move along. In FIG. 3, the straight line P shows the movement locus of the main spot (M1), and the straight line R shows the radius with the least deviation from the straight line P. In this case, since the track direction at the position of the main spot (M1) changes depending on the radius, it is impossible to keep the angle formed by the condensing point array direction and the track direction at a desired constant value. Therefore, by adjusting the diffraction grating 10 so that the condensing point array direction forms a desired angle with respect to the radius (R) with a small deviation from the movement locus (P) of the main spot (M1), the condensing point is adjusted. An error in the angle formed by the arrangement direction and the track direction is minimized.
[0028]
The condensing points (S2 +, M2, S2-) on the optical disc D by the second light source 7 are in the x direction from the condensing points (S1 +, M1, S1-) by the first light source 6 as shown in FIG. Condensed at a position that is equidistant from Therefore, the movement locus of the main spot (M2) by the second light source 7 is substantially the same as the movement locus of the main spot (M1) by the first light source 6, and the tracking error detection error in the first light source 6 as described above. Is adjusted so as to be minimized, the error is minimized also in the second light source 7.
[0029]
FIG. 4 is a perspective view for explaining a configuration example in which the present invention is not implemented. The arrangement direction of the first light source 6 and the second light source 7 is the x-axis with respect to the configuration of the embodiment of FIG. The only difference is the z-axis direction, not the direction.
[0030]
FIG. 5 is an explanatory diagram showing the condensing point position on the optical disc D in the configuration example of FIG. 4, and the condensing points (S2 +, M2, S2-) by the second light source 7 are the first light source 6 respectively. Is condensed at a position equidistant from the condensing point (S1 +, M1, S1-) in the y-axis direction. A straight line P1 is a movement locus of the main spot (M1) by the first light source 6, and a straight line P2 is a movement locus of the main spot (M2) by the second light source 7, which are parallel to each other at a distance. The straight line R1 has the smallest deviation from the straight line P1, and the straight line R2 has the smallest deviation from the straight line P2. The two do not match.
[0031]
The diffraction grating 10 is adjusted so that the tracking error detection error is minimized by adjusting the diffraction grating 10 so that the arrangement direction of the condensing points (S2 +, M2, S2-) by the second light source 7 forms a desired angle (A) with the straight line R2. Then, the angle (B) formed by the arrangement direction of the condensing points (S1 +, M1, S1-) by the first light source 6 and the straight line R1 has a value different from the desired angle (A). Therefore, the tracking error detection error is not minimized in the first light source 6.
[0032]
In FIG. 1 to FIG. 3, for ease of explanation, the emission direction of both light sources 6 and 7 is set parallel to the y axis, and the arrangement direction of both light sources 6 and 7 is set parallel to the x axis. If the setting is such that the main spots (M1, M2) are arranged in the x-axis direction on D, the emission directions of the light sources 6 and 7 do not have to be parallel to the y-axis. 7 are not parallel to the x-axis.
[0033]
Although the differential push-pull method has been described, the same applies to the 3-beam method. In this case, the side spot is set at a position shifted from the main spot by a ¼ track pitch instead of a ½ track pitch. That's fine.
[0034]
Further, it is preferable that the diffraction grating 10 is fixed to the light source module 2 because it is less susceptible to changes with time and temperature. In this case, after fixing the diffraction grating 10 to the light source module 2, the light source module 2 is mounted on the housing 1, and the diffraction grating 10 is rotated together with the light source module 2 to adjust the focusing point arrangement direction on the optical disc D. When the design value of the angle formed by the condensing point array direction and the track direction is θ, the grating direction of the diffraction grating 10 is adjusted and fixed in advance to a state inclined by θ from the array direction of the light sources 6 and 7. Thus, the arrangement direction of the condensing point by the first light source 6 and the condensing point by the second light source 7 on the optical disc D can be set to the radial direction.
[0035]
Further, the track pitch of the target optical disc D may be different between the first light source 6 and the second light source 7.
[0036]
Here, among n light sources, the track pitch targeted for the nth light source is Tn, the interval between the main spot and the side spot is Bn, and the angle formed by the arrangement direction of the main spot and the side spot and the track direction is When θ and an arbitrary natural number are Kn, the optimum condition for adopting the differential push-pull method is (Equation 9).
[0037]
[Equation 9]
Bn × sin θ≈Tn × (2 × Kn−1) / 2
Further, the optimum condition for employing the three-beam method is (Equation 10).
[0038]
[Expression 10]
Bn × sin θ≈Tn × (2 × Kn−1) / 4
FIG. 6 is an explanatory diagram showing an example thereof. T2 / T1 = 2, B1 = B2, K1 = 3, K2 = 3, the first light source 6 satisfies (Equation 9), and the second The light source 7 satisfies (Equation 10).
[0039]
The interval Bn between the main spot and the side spot is the same between the first light source 6 and the second light source 7 in the embodiment shown in FIGS. 1 to 3, but the first light source 6 and the second light source 7 are the same. When the wavelength is different from 7, the diffraction angle at the diffraction grating 10 is different, resulting in a different value.
[0040]
The angle θ formed by the focusing point array direction and the track direction is the same for the first light source 6 and the second light source 7. The natural number Kn can take any value independently between the first light source 6 and the second light source 7.
[0041]
Therefore, by setting θ so that (Equation 9) or (Equation 10) is satisfied in each of the light sources 6 and 7, the differential push-pull method or the three beams can be used for two types of disks having different operating wavelengths and track pitches. The law can be applied. Both the light sources 6 and 7 can adopt different tracking error detection methods.
[0042]
Depending on the combination of track pitches targeted by the first light source 6 and the second light source 7, there may be no solution in which both the light sources 6 and 7 simultaneously satisfy (Equation 9) or (Equation 10). In this case, although the detection level is lowered, the differential push-pull method or the three-beam method can be adopted for both the light sources 6 and 7 by setting the conditions so as not to meet the worst conditions.
[0043]
The worst condition in which the differential push-pull method cannot be adopted is (Equation 11).
[0044]
## EQU11 ##
Bn × sin θ = Tn × Kn
Further, the worst condition in which the 3-beam method cannot be adopted is (Equation 12).
[0045]
[Expression 12]
Bn × sin θ = Tn × Kn / 2
Θ is set so that (Equation 11) or (Equation 12) is not satisfied.
[0046]
【The invention's effect】
As described above, according to the first aspect of the present invention, since the condensing point on the optical disk is set to be shifted in the radial direction by each light source (light emitting point), the differential push-pull method or the three-beam method is used. The optimum arrangement direction of the main spot and the side spot in the method can be made the same for each light source.
[0047]
According to the second aspect of the invention, since the condensing point on the optical disk is set to be shifted in the seek direction by each light source, the seek operation of the tracking error signal in the differential push-pull method or the three-beam method. The setting that minimizes the fluctuation due to the above can be made the same for each light source.
[0048]
According to the invention of claim 3, since the diffraction grating is provided, the side spot in the differential push-pull method or the three beam method can be easily generated, and the side spot generating means is shared by each light source. Can be
[0049]
According to the invention of claim 4, since the diffraction grating for splitting the emitted light beam is fixed to the light source module, stable characteristics are obtained that are hardly affected by changes with time and temperature.
[0050]
Further, according to the invention according to claim 5, since a plurality of light sources having different wavelengths are mounted, it is possible to cope with a plurality of types of optical disks having different use wavelengths by switching the light sources.
[0051]
Further, according to the inventions according to claims 6 and 9, since the side spot generation condition is set for the differential push-pull method corresponding to a plurality of combinations of the used wavelength and the track pitch, by switching the light source The differential push-pull method can be used for a plurality of types of optical disks having different operating wavelengths and track pitches.
[0052]
According to the inventions according to claims 7 and 10, since the side spot generation conditions are set for the three-beam method corresponding to a plurality of combinations of the used wavelength and the track pitch, the used wavelength or A plurality of types of optical disks having different track pitches can be handled by the three-beam method.
[0053]
According to the inventions according to claims 8 and 11, since the side spot generation conditions are set corresponding to a plurality of combinations of the operating wavelength, the track pitch, and the tracking error detecting method, the operating wavelength or A plurality of types of optical disks having different track pitches and tracking error detection methods can be handled.
[0054]
According to the twelfth aspect of the invention, since the grating direction of the diffraction grating is set to a predetermined direction with respect to the arrangement direction of the light sources, the diffraction grating is fixed to the light source module and then rotated together with the light source module, and the optical disk It is possible to adjust the upper condensing point arrangement direction and to shift the condensing point on the optical disc by the light source in the radial direction.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an optical pickup for explaining an embodiment of the present invention. FIG. 2 is an explanatory view showing a condensing point position on the optical disc D in FIG. FIG. 4 is a perspective view for explaining a configuration example in which the present invention is not implemented. FIG. 5 is an explanatory diagram showing a focus point position on the optical disc D in the configuration example of FIG. FIG. 6 is an explanatory diagram showing a focal point position on the optical disc D in the embodiment of the present invention.
DESCRIPTION OF SYMBOLS 1 Housing 2 Light source module 3 Coupling lens 4 Rising mirror 5 Objective lens 6 1st light source 7 2nd light source 8 Light receiving element 9 Hologram element 10 Diffraction grating M1, M2 Main spot S1 +, S1-, S2 +, S2- side Spot Tp Track pitch

Claims (12)

In a light source device mounted on an optical pickup that records / reproduces information by condensing light emitted from a light source module on an optical disk, a plurality of light emitting points are installed in the light source module, and each light emitting point is supported. A light source device characterized in that the position of each light emitting point is set so that the respective condensing points on the optical disk are arranged in the radial direction of the optical disk. In the light source device mounted on the optical pickup in the optical disc apparatus that transports the optical pickup that records / reproduces information on the optical disc by collecting the light emitted from the light source module in the radial direction of the optical disc by the coarse motion mechanism, The light source module is provided with a plurality of light emitting points, and the positions of the respective light emitting points are set so that the respective condensing points on the optical disc corresponding to the respective light emitting points are arranged in the transport direction of the coarse movement mechanism. A light source device. 3. The light source according to claim 1, further comprising a diffraction grating that divides the light emitted from the light source module so as to irradiate the optical disc with three or more condensing points for each of the light emitting points. apparatus. The light source device according to claim 3, wherein the diffraction grating is fixed to the light source module. The light source device according to any one of claims 1 to 4, wherein the wavelength of the emitted light from each light emitting point is set to be different. The interval between spots on the optical disk formed by the nth light emitting point is Bn, the track pitch of the optical disk targeted by the nth light emitting point is Tn, the constant that is a natural number depending on the light emitting point is Kn, and constant regardless of the light emitting point. When the constant that becomes the value of θ is θ,

The light source device according to claim 3, wherein the diffraction grating is set so as to satisfy the following formula. The interval between spots on the optical disk formed by the nth light emitting point is Bn, the track pitch of the optical disk targeted by the nth light emitting point is Tn, the constant that is a natural number depending on the light emitting point is Kn, and constant regardless of the light emitting point. When the constant that becomes the value of θ is θ,

The light source device according to claim 3, wherein the diffraction grating is set so as to satisfy the following formula. The interval between spots on the optical disk formed by the nth light emitting point is Bn, the track pitch of the optical disk targeted by the nth light emitting point is Tn, the constant that is a natural number depending on the light emitting point is Kn, and constant regardless of the light emitting point. When the constant that becomes the value of θ is θ,

Or

The light source device according to claim 3, wherein the diffraction grating is set to satisfy any one of the following formulas. The interval between spots on the optical disk formed by the nth light emitting point is Bn, the track pitch of the optical disk targeted by the nth light emitting point is Tn, the constant that is a natural number depending on the light emitting point is Kn, and constant regardless of the light emitting point. When the constant that becomes the value of θ is θ,

The light source device according to claim 3, wherein the diffraction grating is set so as to satisfy the following formula. The interval between spots on the optical disk formed by the nth light emitting point is Bn, the track pitch of the optical disk targeted by the nth light emitting point is Tn, the constant that is a natural number depending on the light emitting point is Kn, and constant regardless of the light emitting point. When the constant that becomes the value of θ is θ,

The light source device according to claim 3, wherein the diffraction grating is set so as to satisfy the following formula. The interval between spots on the optical disk formed by the nth light emitting point is Bn, the track pitch of the optical disk targeted by the nth light emitting point is Tn, the constant that is a natural number depending on the light emitting point is Kn, and constant regardless of the light emitting point. When the constant that becomes the value of θ is θ,

Or

The light source device according to claim 3, wherein the diffraction grating is set to satisfy any one of the following formulas. The light source device according to any one of claims 6 to 11, wherein an angle formed between an arrangement direction of the light emitting points and a grating direction of the diffraction grating is the θ.

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