JP2021043352A - Laser light source device and image forming device using the same - Google Patents

Abstract

To provide a laser light source with which component counts and costs are reduced, and which emits a multiple-wavelength laser.SOLUTION: Provided is a laser light source device (1) comprising a diffraction optical element (13) for diffracting a laser beam emitted from laser elements (3, 5, 7), and a collimator lens (15) for parallelizing the respective laser beams. The respective laser elements (3, 5, 7) emit laser beams mutually differing in wavelength, and the diffraction optical element (13) has a sawtooth shaped part (13a) in which a plurality of linear grooves (13b) are formed in parallel to each other. The respective laser elements (3, 5, 7) are arranged in a sectional view that includes an optical axis (Ls) of the collimator lens (15), at positions differing in distance to the optical axis (Ls) and closer to one side than the optical axis of the collimator lens (15), the respective laser beams being diffracted in different orders of diffraction by the diffraction optical element (13) and synthesized.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a laser light source device that emits laser light having a plurality of wavelengths and an image forming device using the laser light source device.

Conventionally, a laser light source device that emits laser light of a plurality of wavelengths has synthesized laser light of each wavelength by using a dichroic mirror. Further, the laser light of each wavelength was made into parallel light before being incident on the dichroic mirror.

Patent Document 1 describes a three-color light source that combines and outputs laser beams of three colors of R (red), G (green), and B (blue). A collimating lens is arranged for each of the red, green, and blue laser diodes, and two wavelength filters are arranged.

Japanese Unexamined Patent Publication No. 2016-174189

However, when a dichroic mirror is used, a collimating lens and a wavelength filter for reflection are required for each laser light source of each color. As a result, the number of parts increases and the cost increases.

The present disclosure provides a laser light source device that emits a plurality of wavelength lasers with a reduced number of parts and a reduced cost.

The laser light source device of the present disclosure includes a plurality of laser elements and
A diffractive optical element that diffracts the laser light emitted from each of the laser elements,
A collimated lens that converts each of the laser beams into parallel light is provided.
Each of the laser elements emits laser light having different wavelengths from each other.
The diffractive optical element has a sawtooth-shaped portion in which a plurality of linear grooves are formed in parallel with each other.
Each of the laser elements is arranged on one side of the optical axis of the collimating lens at a position different from the optical axis in a cross-sectional view including the optical axis of the collimating lens.
Each laser beam emitted from each laser element is diffracted and synthesized by the diffractive optical element at different diffraction orders.

Further, the image forming apparatus of the present disclosure includes the laser light source apparatus and the laser light source apparatus.
A first scanning element that scans a laser beam having a plurality of wavelengths emitted from the laser light source device in the first direction, and a first scanning element.
A second scanning element that scans a laser beam emitted from the first scanning element in a second direction orthogonal to the first direction is provided.

The laser light source device and the image forming device in the present disclosure can reduce the number of parts, reduce the cost, and emit a plurality of wavelength lasers.

Cross-sectional view showing the configuration of the laser light source device A linear diffraction grating formed on the light source side of the collimating lens is shown, (a) is a plan view of the linear diffraction grating 13 as viewed from the light source side, and (b) is a portion of the linear diffraction grating. Cross section Perspective view of collimating lens A graph showing the relationship between the diffraction order of each of the red laser element, the green laser element, and the blue laser element and the diffraction efficiency of each. Cross-sectional view of the laser light source device according to the first embodiment Explanatory drawing which shows the relative position of a red laser element and a blue laser element with respect to the position of a green laser element in Embodiment 1. A table showing various conditions of the optical system of the light source device according to the first embodiment. The figure which shows the spherical aberration of the optical system of the light source apparatus in Embodiment 1. Cross-sectional view of the laser light source device according to the second embodiment Explanatory drawing which shows the relative position of a red laser element and a blue laser element with respect to the position of a green laser element in Embodiment 2. A table showing various conditions of the optical system of the light source device according to the second embodiment. The figure which shows the spherical aberration of the optical system of the light source apparatus in Embodiment 2. Cross-sectional view of the laser light source device according to the third embodiment The concentric diffraction grating formed on the collimating lens in the third embodiment is shown, (a) is a cross-sectional view of the concentric diffraction grating, and (b) is a front view of the concentric diffraction grating. Explanatory drawing which shows the relative position of a red laser element and a blue laser element with respect to the position of a green laser element in Embodiment 3. A table showing various conditions of the optical system of the light source device according to the third embodiment. The figure which shows the spherical aberration of the optical system of the light source apparatus in Embodiment 3. Cross-sectional view of the laser light source device according to the fourth embodiment Explanatory drawing which shows the relative position of a red laser element and a blue laser element with respect to the position of a green laser element in Embodiment 4. A table showing various conditions of the optical system of the light source device according to the fourth embodiment. The figure which shows the spherical aberration of the optical system of the light source apparatus in Embodiment 4. Cross-sectional view of the laser light source device according to the fifth embodiment Explanatory drawing which shows the relative position of a red laser element and a blue laser element with respect to the position of a green laser element in Embodiment 5. A table showing various conditions of the optical system of the light source device according to the fifth embodiment. The figure which shows the spherical aberration of the optical system of the light source apparatus in Embodiment 5. Cross-sectional view of the laser light source device according to the sixth embodiment Explanatory drawing which shows the relative position of a red laser element and a blue laser element with respect to the position of a green laser element in Embodiment 6. A table showing various conditions of the optical system of the light source device according to the sixth embodiment. The figure which shows the spherical aberration of the optical system of the light source apparatus in Embodiment 6. Explanatory drawing which shows an example of the image forming apparatus in Embodiment 7. Graph showing diffraction efficiency of each embodiment

Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed explanation than necessary may be omitted. For example, detailed explanations of already well-known matters and duplicate explanations for substantially the same configuration may be omitted. This is to avoid unnecessary redundancy of the following description and to facilitate the understanding of those skilled in the art.
It should be noted that the inventors (or others) intend to limit the subject matter described in the claims by those skilled in the art by providing the accompanying drawings and the following description in order to fully understand the present disclosure. It is not something to do.

First, a schematic description of the present disclosure will be given with reference to FIGS. 1 to 3. FIG. 1 is a cross-sectional view showing an example of the configuration of the light source device of the present disclosure. 2A shows a linear diffraction grating 13 formed on the light source side of the collimating lens 15, FIG. 2A is a rear view of the linear diffraction grating 13, and FIG. 2B is a linear diffraction grating 13. It is a partial sectional view of. FIG. 2B is a perspective view of the collimating lens. FIG. 3 is a graph showing the relationship between the diffraction order of each of the red laser element, the green laser element, and the blue laser element and the diffraction efficiency of each. In FIG. 1, the direction of the optical axis Ls of the collimating lens 15 is the Z-axis direction, the direction perpendicular to the optical axis Ls of the collimating lens and the inside of the paper surface is the Y-axis direction, and the Z-axis direction and the direction perpendicular to the paper surface are X. Axial direction.

The light source device 1 includes a laser light source 2 that emits laser light having a plurality of wavelengths, a diffraction grating 13 that diffracts laser light having a plurality of wavelengths emitted from the laser light source 2, and each laser that is diffracted by the diffraction grating 13. A collimating lens 15 for converting light into parallel light is provided. In this example, the diffraction grating 13 as a diffraction optical element is formed on one surface of the collimating lens 15, but the diffraction grating 13 and the collimating lens 15 may be separate bodies. The convex surface 16 of the collimating lens 15 has an aspherical shape.

The laser light source 2 has at least two or more laser elements that emit laser light having different wavelengths. In the example of FIG. 1, the laser light source 2 includes a red laser element 3, a green laser element 5, and a blue laser element 7. Each laser element is, for example, a laser chip type semiconductor laser. The light sources of the red laser element 3, the green laser element 5, and the blue laser element 7 do not exist on the optical axis Ls of the collimating lens 15, and in a cross-sectional view taken along the YZ plane including the optical axis Ls of the collimating lens 15. The collimating lens 15 is arranged on one side of the optical axis Ls at a position different from the optical axis Ls. The direction in which the intensity of the laser emitted from each laser element is the strongest is directed toward the center of the collimating lens 15.

The laser light of each wavelength emitted from the laser light source 2 is diffracted by the diffraction grating 13. The diffraction grating 13 has a plurality of blaze 13a as serrated portions in which a plurality of linear grooves 13b are formed in parallel with each other. The blaze 13a has, for example, a right triangle shape in a cross-sectional view of the YZ plane including the optical axis Ls, and has a groove 13b and a hypotenuse 13c that rises from the groove 13b in the optical axis Ls direction of the collimating lens 15. The sawtooth shape is not limited to a straight shape with the hypotenuse 13c in cross-sectional view, but also includes an arc shape. The linear groove 13b extends in the direction perpendicular to the optical axis Ls (X-axis direction). Each groove 13b is formed in parallel. For example, the direction in which the groove 13b of the blaze 13a of the diffraction grating 13 extends (X-axis direction) is orthogonal to the YZ plane including the optical axis Ls of the collimating lens 15. The diffraction efficiency of each wavelength changes depending on the height d of the saw-toothed blaze 13a of the diffraction grating 13.

FIG. 3 shows the change in diffraction efficiency at the diffraction order having the highest diffraction efficiency at each wavelength depending on the blaze height (horizontal axis). The diffraction efficiency is calculated by scalar analysis. The calculation conditions are that the wavelength of the blue laser light BL is 0.467 μm, the wavelength of the green laser light GL is 0.532 μm, the wavelength of the red laser light RL is 0.630 μm, and the material is K-SFLD8 of Sumita Optical Glass, Inc. It was used. The numbers shown at the peaks of each graph indicate the highest diffraction efficiency of each wavelength. For example, when the primary diffracted light of the green laser light GL has a diffraction efficiency of 100%, the red and blue laser beams RL and BL have a diffraction efficiency of about 90%, respectively, and are regarded as parallel light. The amount of laser light of each color in the case is 10% less than the amount of emitted light. The reduced amount of light becomes stray light, which also causes noise.

On the other hand, when the height d of the blaze is 4.6 μm, the fifth-order diffracted light of the red laser light RL, the sixth-order diffracted light of the green laser light GL, and the seventh-order diffracted light of the blue laser light BL have almost 100% diffraction efficiency. It becomes. Therefore, by making the 5th-order diffracted light of the red laser light RL, the 6th-order diffracted light of the green laser light GL, and the 7th-order diffracted light of the blue laser light BL parallel, the laser light of different wavelengths is efficiently made into parallel light. It can be seen that there are conditions that enable synthesis.

In the light source device 1, each wavelength of each laser element is λp, the refractive index of the diffractive optical element at each wavelength is np, and the height of the blaze, which is the serrated portion of the diffractive optical element, is d. When the diffraction order having the maximum diffraction efficiency at the wavelength is mp, mp is an integer other than 0, and it is desirable that the following equation (1) is satisfied.
-0.175 <d (np-1) / λp-mp <0.175 ... (1)

If the light source device 1 satisfies the equation (1), parallel light having high diffraction efficiency can be obtained.

Further, if the following equation (2) is satisfied instead of the equation (1), the diffraction efficiency is still improved.
-0.1 <d (np-1) /λp-mp <0.1 ... Eq. (2)

If the light source device 1 satisfies the equation (2), parallel light having a higher diffraction efficiency can be obtained.

ここで、ｒは光軸からの距離（＝（ｘ^２＋ｙ^２）^１／２）であり、ｃは曲率であり、ｋは円錐定数であり、Aｎはｎ次の非球面係数である。 The following formula is used as a formula for expressing the aspherical surface of the lens surface.

Here, r is the distance from the optical axis (= (x ² + y ² ) ^1/2 ), c is the curvature, k is the conical constant, and An is the nth-order aspherical coefficient.

(Embodiment 1)
Hereinafter, the first embodiment, which is more specifically exemplified, will be described with reference to FIGS. 4 to 7.
[1-1. Constitution]
FIG. 4 is an explanatory diagram showing the configuration of the light source device 1A according to the first embodiment. FIG. 5 is an explanatory diagram showing the relative positions of the red laser element and the blue laser element with reference to the position of the green laser element. FIG. 6 is a table showing various conditions of the optical system of the light source device 1A. FIG. 7 is a diagram showing spherical aberration of the optical system of the light source device 1A.

The light source device 1A includes a light source 2, a diffractive lens 19A, and a collimating lens 15A. The collimating lens 15A has an aspherical S1 surface and an S2 surface. The flat plate-shaped diffraction lens 19A has a flat S3 surface and an S4 surface on which a linear diffraction grating 13 is formed.

In the light source device 1A of the first embodiment, the diffraction grating S4 surface of the diffractive lens 19A, the S3 surface of the diffractive lens 19A, the S2 surface of the collimating lens 15A, and the S1 surface of the collimating lens 15 are arranged in the order of the optical path from the laser light source 2. Is placed.

FIG. 4 shows the focal position Fc of the non-diffracting light on the optical axis Ls of the collimating lens 15A, and the position of the diffracting light source 2 is located at a distance Ly1 in the vertical direction (Y-axis direction) from the optical axis Ls. Here, the position of the green laser element 5 is shown as a reference. FIG. 5 shows the positional relationship between the red laser element 3 and the blue laser element 7 in the focus direction (Z-axis direction) and the direction perpendicular to the optical axis (Y-axis direction) with reference to the green laser element 5.

In the first embodiment, the green laser element 5 is arranged at a position of −3.025 mm (Ly1) in the vertical direction (Y-axis direction) of the optical axis Ls. As shown in FIG. 5, the red laser element 3 is arranged at a position of about 90 μm in the focus direction (Z-axis direction) and about 70 μm in the vertical direction (Y-axis direction) of the optical axis Ls from the green laser element 5. .. The blue laser element 7 is arranged at a position of about −90 μm in the focus direction (Z-axis direction) and about −120 μm in the vertical direction (Y-axis direction) of the optical axis Ls from the green laser element 5.

A specific numerical configuration of the optical system in the light source device 1A of the first embodiment is shown in FIG. FIG. 6A shows the focal length f of the collimating lens 15A, the numerical aperture NA of the collimating lens 15A, the wavelength λ1 of the blue laser beam BL, the wavelength λ2 of the green laser beam GL, and the wavelength λ3 of the red laser beam RL.

In FIG. 6B, the curvature R of each of the surface numbers S1 to S3, the distance (distance) t to the next surface of each of the surface numbers S1 to S3, and the back focus t of the surface number S4 are shown. Further, in FIG. 6C, the refractive index n1 is a value for each wavelength λ1 of the plane numbers S1 and S3, the refractive index n2 is a value for each wavelength λ2 of the plane numbers S1 and S3, and the refractive index n3 is a plane. It is a value for the wavelength λ3 of each of the numbers S1 and S3.

The surface number S1 in the collimating lens 15A is an aspherical surface, the conical coefficient k in Eq. (3) is −0.92456, and the fourth-order aspherical coefficient A4 = 1.47679 × 10 ^-4 . Further, the surface number S2 in the collimating lens 15A is also an aspherical surface, and the fourth-order aspherical surface coefficient A4 = 4.1240 × ^10-5 in the equation (3).

The height d of the blaze 13a of the diffraction grating 13 is 3.121 μm, and the pitch width Pb is 8 μm. According to the diffraction grating 13, the diffraction grating 13 has a diffraction order m1 = 6 of the blue laser light BL, a diffraction order m2 = 5 of the green laser light GL, and a diffraction order m3 = 4 of the red laser light RL. Is emitted from.

Therefore,
d (n1-1) / λ1-m1 = 0.06691,
d (n2-1) / λ2-m2 = 0.03501,
d (n3-1) / λ3-m3 = 0.05339,
And satisfies both the conditions of both equations (1) and (2).

With these configurations, the diffraction efficiency is 98.5% for the blue laser light BL, 99.6% for the green laser light GL, and 99.1% for the red laser light RL, and highly efficient diffraction efficiency can be obtained. ..

With reference to FIG. 7, the chromatic aberration of each laser beam is about ± 0.1 mm. The laser elements of each color are arranged so as to be shifted in the focus direction (Z-axis direction) so as to correct this chromatic aberration.

[1-2. Effect, etc.]
The light source device 1A according to the first embodiment is diffracted by a plurality of laser elements 3, 5, 7 and a diffraction grating 13 that diffracts the laser light emitted from the respective laser elements 3, 5, 7. A collimating lens 15A for converting each laser beam into parallel light is provided. Each of the laser elements 3, 5 and 7 emits laser beams BL, GL, and RL having different wavelengths from each other, and the diffraction grating 13 has a blaze 13a in which a plurality of linear grooves 13b are formed in parallel. The respective laser elements 3, 5 and 7 are arranged at positions different from the optical axis Ls on one side of the optical axis Ls of the collimating lens 15A in a cross-sectional view of the YZ plane including the optical axis Ls of the collimating lens 15A. Has been done. The laser beams BL, GL, and RL emitted from the respective laser elements 3, 5, and 7 are diffracted and synthesized by the diffraction grating 13 at different diffraction orders. As a result, each diffracted light having a different diffraction order at each wavelength is generated, and these diffracted lights are made into parallel light, so that a parallel beam with improved diffraction efficiency can be generated. Further, by using the diffraction grating 13, it is possible to reduce the number of parts, reduce the cost, and emit a plurality of wavelength lasers. Further, by improving the diffraction efficiency, the generation of stray light can be reduced. Further, since the laser light emitted from the laser elements 3, 5 and 7 is diffracted, even if the ambient temperature changes and the wavelength of each laser light changes, the respective laser lights are diffracted in the same direction. Therefore, the influence of the temperature change can be reduced as compared with the configuration in which only a part of the laser light is diffracted. Further, in the first embodiment, since the collimating lens 15A and the diffraction grating 13 are separate bodies, they can be formed of different materials, and the optimum material can be selected for each.

Further, the wavelengths of the respective laser elements BL, GL, and RL are set to λ1, λ2, and λ3, the refractive index of the diffraction grating 13 at each wavelength is set to n1, n2, and n3, and the blaze, which is the sawtooth shape portion of the diffraction grating 13. When the height of 13a is d and the diffraction orders m1, m2, and m3, which are the combination of the maximum diffraction efficiencies at each wavelength, m1, m2, and m3 are non-zero integers.
−0.175 <d (n1-1) /λ1-m1 <0.175,
−0.175 <d (n2-1) /λ2-m2 <0.175,
−0.175 <d (n3-1) /λ3-m3 <0.175,
Meet. This makes it possible to generate a parallel beam with improved diffraction efficiency.

(Embodiment 2)
Next, the second embodiment will be described with reference to FIGS. 8 to 11. FIG. 8 is a cross-sectional view showing the configuration of the light source device 1B according to the second embodiment. FIG. 9 is an explanatory diagram showing the relative positions of the red laser element and the blue laser element with reference to the position of the green laser element. FIG. 10 is a table showing various conditions of the optical system of the light source device 1B. FIG. 11 is a diagram showing spherical aberration of the optical system of the light source device 1B.
[2-1. Constitution]
As shown in FIG. 8, in the light source device 1B of the second embodiment, the collimating lens 15B has a shape in which the collimating lens 15A of the light source device 1A of the first embodiment and the diffraction grating 13 are integrated. Even if one side of the collimating lens 15B has a planar shape, a lens material that suppresses off-axis coma and can be glass-molded is selected. The light source device 1A of the first embodiment and the light source device 1B of the second embodiment have the same configuration other than these differences and the points described below.

The light source device 1B includes a light source 2 and a collimating lens 15B in which a diffraction grating 13 is formed on one surface. The collimating lens 15B has an aspherical S1 surface and an S2 surface on which a linear diffraction grating 13 is formed. In the light source device 1B according to the second embodiment, the diffraction grating 13's diffraction surface S2 and the convex S1 surface are arranged in the order of the optical path from the laser light source 2.

FIG. 8 shows the focal position Fc of the non-diffracting light on the optical axis Ls of the collimating lens 15B, and the position of the diffracting light source 2 is located at a distance Ly2 in the vertical direction (Y-axis direction) from the optical axis Ls. Here, the position of the green laser element 5 is shown as a reference. FIG. 9 shows the positional relationship between the red laser element 3 and the blue laser element 7 in the focus direction (Z-axis direction) and the direction perpendicular to the optical axis (Y-axis direction) with reference to the green laser element 5.

In the second embodiment, the green laser element 5 is arranged at a position of -2.737 mm (Ly2) in the vertical direction (Y-axis direction) of the optical axis Ls. As shown in FIG. 9, the red laser element 3 is arranged at a position of about 170 μm in the focus direction (Z-axis direction) and about 40 μm in the vertical direction (X-axis direction) of the optical axis Ls from the green laser element 5. .. The blue laser element 7 is arranged at a position of about −170 μm in the focus direction (Z-axis direction) and about −80 μm in the vertical direction (Y-axis direction) of the optical axis Ls from the green laser element 5.

A specific numerical configuration of the optical system in the light source device 1B of the second embodiment is shown in FIG. The surface number S1 in the collimating lens 15B is an aspherical surface, the conical coefficient k in Eq. (3) is −0.9466, the fourth-order aspherical coefficient A4 = 1.01201 × 10 ^-4 , and the sixth-order The aspherical coefficient A6 = 1.00260 × ^10-7 . Further, the surface number S2 in the collimating lens 15B is a flat surface.

The height d of the blaze 13a of the diffraction grating 13 is 4.013 μm. According to the diffraction grating 13, the diffraction grating 13 has a diffraction order m1 = 6 of the blue laser light BL, a diffraction order m2 = 5 of the green laser light GL, and a diffraction order m3 = 4 of the red laser light RL. Is emitted from.

Therefore,
d (n1-1) / λ1-m1 = -0.10660,
d (n2-1) / λ2-m2 = 0.04984,
d (n3-1) / λ3-m3 = 0.09988,
And satisfy the condition of equation (1).

With these configurations, the diffraction efficiency is 96.2% for the blue laser light BL, 99.2% for the green laser light GL, and 96.8% for the red laser light RL, and highly efficient diffraction efficiency can be obtained. ..

Further, referring to FIG. 11, the chromatic aberration of each laser beam is about ± 0.18 mm. Laser elements of each color are arranged so as to be offset in the optical axis Ls direction (Z-axis direction) of the collimating lens 15 so as to correct this chromatic aberration. The optical axis Ls direction of the collimating lens 15 can be said to be the focus direction.

[2-2. Effect, etc.]
According to the configuration of the second embodiment, it is possible to generate a parallel beam having improved diffraction efficiency by generating each diffracted light having a different diffraction order at each wavelength and making these diffracted lights parallel light. .. Further, in the second embodiment, since the collimating lens 15B and the diffraction grating 13 are integrated, space saving can be realized. Further, since one side of the collimating lens 15B is a flat S2 surface, the diffraction grating 13 can be easily formed on the S2 surface.

(Embodiment 3)
Hereinafter, the third embodiment will be described with reference to FIGS. 12 to 16. FIG. 12 is an explanatory diagram showing the configuration of the light source device 1C according to the third embodiment. FIG. 13 shows a concentric diffraction grating 19 formed on the S1 surface of the collimating lens 15C, FIG. 13A is a cross-sectional view of the concentric diffraction grating 19, and FIG. 13B is a concentric diffraction grating. It is a front view of the diffraction grating 19 of. FIG. 14 is an explanatory diagram showing the relative positions of the red laser element and the blue laser element with reference to the position of the green laser element. FIG. 15 is a table showing various conditions of the optical system of the light source device 1C. FIG. 16 is a diagram showing spherical aberration of the optical system of the light source device 1C.

[3-1. Constitution]
As shown in FIG. 12, the light source device 1C of the third embodiment has a concentric diffraction grating 19 on the S1 surface of the collimating lens 15C of the light source device 1B of the second embodiment. The light source device 1C of the third embodiment and the light source device 1B of the second embodiment have the same configuration other than these differences and the points described below.

The light source device 1C includes a light source 2 and a collimating lens 15C in which a diffraction grating 13 is formed on one surface. The collimating lens 15C has an aspherical and convex S1 surface and a flat S2 surface on which a linear diffraction grating 13 is formed.

In the light source device 1C according to the third embodiment, a diffraction surface S2 surface on which a linear diffraction grating 13 is formed and an aspherical surface S1 surface are arranged in the order of the optical path from the laser light source 2. A concentric diffraction grating 19 is formed on the aspherical S1 surface. Therefore, the collimating lens 15C is a collimating lens including a concentric diffractive lens.

FIG. 12 shows the focal position Fc of the non-diffracting light on the optical axis Ls of the collimating lens 15C, and the position of the diffracting light source 2 is located at a distance Ly3 in the vertical direction (Y-axis direction) from the optical axis Ls. Here, the position of the green laser element 5 is shown as a reference. FIG. 14 shows the positional relationship between the red laser element 3 and the blue laser element 7 in the focus direction (Z-axis direction) and the direction perpendicular to the optical axis (X direction) with respect to the green laser element 5.

In the third embodiment, the green laser element 5 is arranged at a position of -2.737 mm (Ly3) in the vertical direction (Z-axis direction) of the optical axis Ls. Then, as shown in FIG. 14, the red laser element 3 is arranged at a position of about −42 μm in the focus direction (Z-axis direction) and about 100 μm in the vertical direction (X-axis direction) of the optical axis Ls from the green laser element 5. ing. The blue laser element 7 is arranged at a position of about −45 μm in the focus direction (Z-axis direction) and about −120 μm in the vertical direction (X-axis direction) of the optical axis Ls from the green laser element 5.

A specific numerical configuration of the optical system in the light source device 1C of the third embodiment is shown in FIG. The surface number S1 in the collimating lens 15C is an aspherical lens, has a conical coefficient k = 1.32542 in the equation (3), has a fourth-order aspherical coefficient A4 = -4.41926 × 10 ^-4 , and has a sixth-order The aspherical coefficient A6 = -1.10591 × ^10-5 . The surface number S2 in the collimating lens 15C is a flat surface, and a sawtooth-shaped diffraction grating 13 is formed on the S2 surface.

The height d of the blaze 13a of the diffraction grating 13 on the S2 surface is 4.013 μm, and the pitch width Pb is 10 μm. Further, the height h of the blaze 19a of the concentric diffraction grating 19 is also the same height as the height d of the blaze 13a of the linear diffraction grating 13. As a result, high diffraction efficiency can be obtained for any of the wavelengths of red, green, and blue.

According to the diffraction grating 13, the diffraction grating 13 has a diffraction order m1 = 6 of the blue laser light BL, a diffraction order m2 = 5 of the green laser light GL, and a diffraction order m3 = 4 of the red laser light RL. Is emitted from.

Therefore,
d (n1-1) / λ1-m1 = −0.10664,
d (n2-1) / λ2-m2 = 0.04984,
d (n3-1) / λ3-m3 = 0.09987,
And satisfy the condition of equation (1).

With these configurations, the diffraction efficiency is 96.2% for the blue laser light BL, 99.2% for the green laser light GL, and 96.8% for the red laser light RL, and highly efficient diffraction efficiency can be obtained. ..

Referring to FIG. 16, the chromatic aberration of each laser beam is converged within 0.05 mm, the chromatic aberration is smaller than that of the first and second embodiments, and each laser light source can be arranged on substantially the same plane. ..

[3-2. Effect, etc.]
According to the configuration of the third embodiment, it is possible to generate a parallel beam having improved diffraction efficiency by generating each diffracted light having a different diffraction order at each wavelength and making these diffracted lights parallel light. .. Further, in the third embodiment, since the concentric diffraction grating is formed on the S1 surface of the collimating lens 15C, chromatic aberration can be reduced.

(Embodiment 4)
Hereinafter, the fourth embodiment will be described with reference to FIGS. 17 to 20. FIG. 17 is an explanatory diagram showing the configuration of the light source device 1D according to the fourth embodiment. FIG. 18 is an explanatory diagram showing the relative positions of the red laser element and the blue laser element with reference to the position of the green laser element. FIG. 19 is a table showing various conditions of the optical system of the light source device 1D. FIG. 20 is a diagram showing spherical aberration of the optical system of the light source device 1D.

[4-1. Constitution]
As shown in FIG. 17, unlike the light source device 1B of the second embodiment, the light source device 1D of the fourth embodiment has a spherical S2 surface between the S1 surface and the S3 surface of the collimating lens 15D. Regarding the configuration other than this difference and the points described below, the light source device 1D of the fourth embodiment and the light source device 1B of the second embodiment are common.

The light source device 1D includes a light source 2 and a collimating lens 15D in which a diffraction grating 13 is formed on one surface. The collimating lens 15D is a lens in which the first lens 15Da and the second lens 15Db are bonded together. The first lens 15Da has a convex and aspherical S1 surface. The second lens 15Db has a flat S3 surface on which a linear diffraction grating 13 is formed. The collimating lens 15D has a spherical S2 surface, which is a bonding surface between the opposite side of the S1 surface of the first lens 15Da and the opposite side of the S3 surface of the second lens 15Db.

In the light source device 1D according to the fourth embodiment, a diffraction surface S3 surface on which a linear diffraction grating 13 is formed, a spherical S2 surface, and an aspherical S1 surface are arranged in the order of the optical path from the laser light source 2. Has been done.

FIG. 17 shows the focal position Fc of the non-diffracting light on the optical axis Ls of the collimating lens 15D, and the position of the diffracting light source 2 is located at a distance Ly4 in the vertical direction (Y-axis direction) from the optical axis Ls. Here, the position of the green laser element 5 is shown as a reference. FIG. 18 shows the positional relationship between the red laser element 3 and the blue laser element 7 in the focus direction (Z-axis direction) and the direction perpendicular to the optical axis (Y-axis direction) with respect to the green laser element 5.

In the fourth embodiment, the green laser element 5 is arranged at a position of -2.737 mm (Ly4) in the vertical direction (Y-axis direction) of the optical axis Ls. Then, as shown in FIG. 18, the red laser element 3 is arranged at a position of about 20 μm in the focus direction (Z-axis direction) and about 80 μm in the vertical direction (X-axis direction) of the optical axis Ls from the green laser element 5. There is. The blue laser element 7 is arranged at a position of about 10 μm in the focus direction (Z-axis direction) and about −140 μm in the vertical direction (X-axis direction) of the optical axis Ls from the green laser element 5.

A specific numerical configuration of the optical system in the light source device 1D of the fourth embodiment is shown in FIG. The surface number S1 in the collimating lens 15D is an aspherical surface, the conical coefficient k = 0.26004 in the equation (3), the fourth-order aspherical coefficient A4 = −1.64830 × 10 ^-4 , and the sixth-order The aspherical coefficient A6 = −1.55915 × ^10-6 . The surface number S2 in the collimating lens 15D has a spherical shape. The surface number S3 in the collimating lens 15D is a flat surface, and a sawtooth-shaped diffraction grating 13 is formed on the S3 surface.

The height d of the blaze 13a of the diffraction grating 13 on the S3 surface is 4.013 μm, and the pitch width Pb is 10 μm.

According to the diffraction grating 13, the diffraction grating 13 has a diffraction order m1 = 6 of the blue laser light BL, a diffraction order m2 = 5 of the green laser light GL, and a diffraction order m3 = 4 of the red laser light RL. Is emitted from.

Therefore,
d (n1-1) / λ1-m1 = −0.10664,
d (n2-1) / λ2-m2 = 0.04984,
d (n3-1) / λ3-m3 = 0.09987,
And satisfy the condition of equation (1).

With these configurations, the diffraction efficiency is 96.2% for the blue laser light BL, 99.2% for the green laser light GL, and 96.8% for the red laser light RL, and highly efficient diffraction efficiency can be obtained. ..

Referring to FIG. 20, the chromatic aberration of each laser beam is converged within 0.04 mm due to the spherical S2 surface, and the chromatic aberration is smaller than that of the second and third embodiments.

[4-2. Effect, etc.]
According to the configuration of the fourth embodiment, it is possible to generate a parallel beam having improved diffraction efficiency by generating each diffracted light having a different diffraction order at each wavelength and making these diffracted lights parallel light. .. Further, in the fourth embodiment, the collimating lens 15D is a laminated lens of the first lens 15Da and the second lens 15Db, chromatic aberration can be reduced, and the focusing directions (Z directions) of the laser elements 3, 5 and 7, respectively. ) Can be placed close to each other.

(Embodiment 5)
Hereinafter, the fifth embodiment will be described with reference to FIGS. 21 to 24. FIG. 21 is an explanatory diagram showing the configuration of the light source device 1E according to the fifth embodiment. FIG. 22 is an explanatory diagram showing the relative positions of the red laser element and the blue laser element with reference to the position of the green laser element. FIG. 23 is a table showing various conditions of the optical system of the light source device 1E. FIG. 24 is a diagram showing spherical aberration of the optical system of the light source device 1E.

[5-1. Constitution]
As shown in FIG. 21, the light source device 1E of the fifth embodiment is different from the light source device 1D of the fourth embodiment in that the collimating lens 15E and the diffraction lens 19E on which the linear diffraction grating 13 is formed are separate bodies. Has been done. Further, in the fifth embodiment, a combination of wavelengths of laser light different from that of the first to fourth embodiments is used. The light source device 1E of the fifth embodiment and the light source device 1D of the fourth embodiment have the same configuration other than this difference and the points described below.

The light source device 1E includes a light source 2, a collimating lens 15E, and a diffraction lens 19E. The collimating lens 15E is a lens in which the first lens 15Ea and the second lens 15Eb are bonded together. The first lens 15Ea has a convex and aspherical S1 surface. The second lens 15Eb has an aspherical S3 surface. The collimating lens 15E has a spherical S2 surface, which is a bonding surface between the opposite side of the S1 surface of the first lens 15Ea and the opposite side of the S3 surface of the second lens 15Eb.

The diffractive lens 19E has a flat plate shape, and has a flat S4 surface facing the S3 surface of the second lens 15Eb and an S5 surface on which a linear diffraction grating 13 is formed on the light source 2 side.

The light source device 1E according to the fifth embodiment has a diffraction surface S5 surface on which a saw-toothed diffraction grating 13 is formed, a planar S4 surface and an S3 surface, and a spherical S2 surface in the order of the optical path from the laser light source 2. , The aspherical S1 surface is arranged.

FIG. 21 shows the focal position Fc of the non-diffracting light on the optical axis Ls of the collimating lens 15E, and the position of the diffracting light source 2 is located at a distance Ly5 in the vertical direction (Y-axis direction) from the optical axis Ls. FIG. 22 shows the positional relationship between the red laser element 3 and the blue laser element 7 in the focus direction (Z-axis direction) and the direction perpendicular to the optical axis (Y-axis direction) with respect to the green laser element 5.

In the fifth embodiment, the green laser element 5 is arranged at a position of -4.352 mm (Ly5) in the vertical direction (X direction) of the optical axis Ls. Then, as shown in FIG. 22, the red laser element 3 is arranged at a position of about 20 μm in the focus direction (Z-axis direction) and about 60 μm in the vertical direction (X-axis direction) of the optical axis Ls from the green laser element 5. There is. The blue laser element 7 is arranged at a position of about 10 μm in the focus direction (Z-axis direction) and about −130 μm in the vertical direction (X-axis direction) of the optical axis Ls from the green laser element 5.

A specific numerical configuration of the optical system in the light source device 1E of the fifth embodiment is shown in FIG. The surface number S1 in the collimating lens 15E is an aspherical surface, the conical coefficient k = 0.26173 in the equation (3), the fourth-order aspherical coefficient A4 = -1.87896 × 10 ^-4 , and the sixth-order The aspherical coefficient A6 = −5.91751 × ^10-6 . The surface number S3 is also an aspherical surface, and the conical coefficient k = −1091.926 in Eq. (3), the fourth-order aspherical coefficient A4 = −6.87462 × 10 ^-4 , and the sixth-order aspherical surface. The coefficient A6 = 6.47266 × ^10-5 .

The height d of the blaze 13a of the diffraction grating 13 on the S5 plane is 4.382 μm, and the pitch width Pb is 8 μm.

According to the diffraction grating 13, the diffraction grating 13 has a diffraction order m1 = 7 of the blue laser light BL, a diffraction order m2 = 6 of the green laser light GL, and a diffraction order m3 = 5 of the red laser light RL. Is emitted from.

Therefore,
d (n1-1) /λ1-m1=-0.00931,
d (n2-1) / λ2-m2 = 0.01843,
d (n3-1) / λ3-m3 = 0.00740,
And satisfies both the conditions of both equations (1) and (2).

With these configurations, the diffraction efficiency is 99.9% for the blue laser light BL, 99.9% for the green laser light GL, and 99.9% for the red laser light RL, and highly efficient diffraction efficiency can be obtained. ..

Referring to FIG. 24, the chromatic aberration of each laser beam is 0.02 mm or less, and the chromatic aberration is reduced as compared with the second to fourth embodiments.

[5-2. Effect, etc.]
According to the configuration of the fifth embodiment, it is possible to generate a parallel beam having improved diffraction efficiency by generating each diffracted light having a different diffraction order at each wavelength and making these diffracted lights parallel light. .. Further, in the fifth embodiment, the collimating lens 15E is a laminated lens of the first lens 15Ea and the second lens 15Eb, chromatic aberration can be reduced, and the focusing directions (Z directions) of the laser elements 3, 5 and 7, respectively. ) Can be placed close to each other. Further, since the collimating lens 15E and the diffractive lens 19E are separately configured, they can be formed of different materials, and the optimum material can be selected for each.

(Embodiment 6)
Hereinafter, the sixth embodiment will be described with reference to FIGS. 25 to 28. FIG. 25 is an explanatory diagram showing the configuration of the light source device 1F according to the sixth embodiment. FIG. 26 is an explanatory diagram showing the relative positions of the red laser element and the blue laser element with reference to the position of the green laser element. FIG. 27 is a table showing various conditions of the optical system of the light source device 1F. FIG. 28 is a diagram showing spherical aberration of the optical system of the light source device 1F.

[6-1. Constitution]
As shown in FIG. 25, in the light source device 1F of the sixth embodiment, the material of the collimating lens 15B of the light source device 1B of the second embodiment is changed to lengthen the focal length. Further, in the sixth embodiment, a combination of wavelengths of laser light different from that of the first to fourth embodiments is used. The light source device 1F of the sixth embodiment and the light source device 1B of the second embodiment have the same configuration other than these differences and the points described below.

The light source device 1F includes a light source 2 and a collimating lens 15F. The collimating lens 15F has an aspherical S1 surface and a flat S2 surface on which the linear diffraction grating 13 is formed.

In the light source device 1F according to the sixth embodiment, a diffraction surface S2 surface on which a linear diffraction grating 13 is formed and an aspherical S1 surface are arranged in the order of the optical path from the laser light source 2.

FIG. 25 shows the focal position Fc of the non-diffracting light on the optical axis Ls of the collimating lens 15F, and the position of the diffracting light source 2 is located at a distance Ly6 in the vertical direction (Y-axis direction) from the optical axis Ls. FIG. 26 shows the positional relationship between the red laser element 3 and the blue laser element 7 in the focus direction (Z-axis direction) and the direction perpendicular to the optical axis (Y-axis direction) with reference to the green laser element 5.

In the sixth embodiment, the green laser element 5 is arranged at a position of −6.38 mm (Ly6) in the vertical direction (Y-axis direction) of the optical axis Ls. Then, as shown in FIG. 26, the red laser element 3 is arranged at a position of about 420 μm in the focus direction (Z-axis direction) and about 20 μm in the vertical direction (Y-axis direction) of the optical axis Ls from the green laser element 5. There is. The blue laser element 7 is arranged at a position of about -380 μm in the focus direction (Z-axis direction) and about −130 μm in the vertical direction (Y-axis direction) of the optical axis Ls from the green laser element 5.

FIG. 27 shows a specific numerical configuration of the optical system in the light source device 1F of the sixth embodiment. The surface number S1 in the collimating lens 15F is an aspherical surface, the conical coefficient k = −2.58130 in the equation (3), the fourth-order aspherical coefficient A4 = -1.96836 × ^10-5 , and the sixth-order. The aspherical coefficient A6 = -2.95251 × ^10-8 . The surface number S2 in the collimating lens 15F is a flat surface, and a sawtooth-shaped diffraction grating is formed on the S2 surface.

In the sixth embodiment, a combination of wavelengths of laser light, which is different from the first to fourth embodiments, is used. Further, in the sixth embodiment, since the material having a high refractive index was selected, the height d of the blaze 13a of the diffraction grating 13 on the S2 surface is as low as 2.93 μm. The pitch width Pb is 20 μm. Although the pitch width Pb of the diffraction grating is wider than that of the first to fifth embodiments, the distance between the semiconductor lasers can be sufficiently secured by increasing the focal length of the collimating lens.

According to the diffraction grating 13, the diffraction grating 13 has a diffraction order m1 = 6 of the blue laser light BL, a diffraction order m2 = 5 of the green laser light GL, and a diffraction order m3 = 4 of the red laser light RL. Is emitted from.

Therefore,
d (n1-1) /λ1-m1=-0.16212,
d (n2-1) / λ2-m2 = 0.07794,
d (n3-1) / λ3-m3 = 0.09466,
And satisfy the condition of equation (1).

With these configurations, the diffraction efficiency is 91.7% for the blue laser light BL, 97.9% for the green laser light GL, and 97.1% for the red laser light RL, and highly efficient diffraction efficiency can be obtained. ..

Referring to FIG. 28, the chromatic aberration between the green laser element 5 and the red laser element 3 is about 0.42 mm, and the chromatic aberration between the green laser element 5 and the red laser element 3 is about −0.37 mm. Chromatic aberration can be eliminated by arranging the laser elements 3, 5 and 7 so apart from each other. Since the distance between the laser elements can be widened, maintenance becomes easy.

[6-2. Effect, etc.]
According to the configuration of the sixth embodiment, it is possible to generate a parallel beam having improved diffraction efficiency by generating each diffracted light having a different diffraction order at each wavelength and making these diffracted lights parallel light. .. Further, by lowering the height d of the blaze 13a of the diffraction grating 13 as compared with other embodiments and widening the pitch width Pb, it is effective in improving the diffraction efficiency.

(Embodiment 7)
Hereinafter, the seventh embodiment will be described with reference to FIG. 29. FIG. 29 is an explanatory diagram showing the configuration of the image forming apparatus according to the seventh embodiment.

[7-1. Constitution]
The image forming device 21 includes a laser light source device 1, a condenser lens 23, a first scanning element 25, a second scanning element 27, and a control unit 29. The image forming apparatus 21 may use any of the laser light source devices 1A to 1F of the first to sixth embodiments instead of the laser light source device 1.

The condensing lens 23 condenses the parallel light emitted from the collimated lens 15 of the laser light source device 1 on the first scanning element 25.

The first scanning element 25 is, for example, a rotary mirror that is rotationally driven by piezoelectric drive. The laser light having a plurality of wavelengths emitted from the laser light source device 1 is scanned in the first direction. The scanned laser beam is incident on the second scanning element. As a result, the parallel light is diffused in the vertical direction of the screen 31.

The second scanning element 27 is, for example, a rotary mirror that is rotationally driven by piezoelectric drive. The laser beam emitted from the first scanning element 25 is scanned in the second direction orthogonal to the first direction. The scanned laser beam is diffused in the horizontal direction of the screen 31. As a result, the two-dimensional image can be projected on the screen 31.

The control unit 29 controls the light emission timing of each wavelength in synchronization with the scanning of the first scanning element 25 and the second scanning element 27. The control unit 29 can be realized by a semiconductor element or the like. The control unit 29 can be composed of, for example, a microcomputer, a CPU, an MPU, a GPU, a DSP, an FPGA, and an ASIC. The function of the control unit 29 may be configured only by hardware, or may be realized by combining hardware and software. The control unit 29 has a storage unit such as a hard disk (HDD), SSD, and memory, and realizes a predetermined function by reading data and programs stored in the storage unit and performing various arithmetic processes. ..

[7-2. Effect, etc.]
The image forming apparatus 21 of the seventh embodiment includes one of the laser light source devices 1 to 1F, a first scanning element 25 that scans a laser beam having a plurality of wavelengths emitted from the laser light source device in a first direction, and a first scanning element 25. It includes a second scanning element 27 that scans a laser beam emitted from the scanning element 25 in a second direction orthogonal to the first direction. Since the diffraction efficiency of the laser light emitted from the laser light source device is high, the brightness of the laser light projected on the screen 31 can be kept high, and stray light is reduced. The image forming apparatus 21 is not limited to the two-dimensional image, and may project a three-dimensional image.

As described above, FIG. 30 shows the relationship between the equation (1) of the light source 2 and the diffraction efficiency in the illustrated embodiments 1 to 6. In FIG. 30, in the first embodiment, the value of the blue laser light BL of the formula (1) is B1, the value of the green laser light GL is G1, and the value of the red laser light RL is R1. Similarly, in the second to sixth embodiments, the values of the blue laser light BL of the formula (1) are B2 to B6, the values of the green laser light GL are G2 to G6, and the values of the red laser light RL are R2 to R6, respectively. And. The diffraction efficiency of the blue laser light BL, the green laser light GL, and the red laser light RL of any of the embodiments is 91% or more.

(Other embodiments)
As described above, Embodiments 1 to 7 have been described as examples of the techniques disclosed in this application. However, the technique in the present disclosure is not limited to this, and can be applied to embodiments in which changes, replacements, additions, omissions, etc. have been made. Further, it is also possible to combine the constituent elements described in the above-described first to seventh embodiments to form a new embodiment.

(1) The light source device 1 of the present disclosure emits laser light of three colors, but the present invention is not limited to this. For example, it may be two colors or four or more colors. For example, as a light source used in a laser plant factory, a light source device 1 that emits two colors of red laser light RL and blue laser light BL may be configured. Further, for example, as a light source used for generating a two-dimensional image or a three-dimensional image, a light source device 1 that emits four colors of a red laser light RL, a green laser light GL, a blue laser light BL, and a yellow laser light YL is configured. You may.

(2) In the light source device 1 of the present disclosure, a diffraction grating 13 is arranged between the collimating lens 15 and the light source 2, but the present invention is not limited to this. The collimating lens 15 may be arranged closer to the light source 2 than the diffraction grating 13, and the collimating lens 15 may be arranged between the diffraction grating 13 and the light source 2.

As described above, an embodiment has been described as an example of the technique in the present disclosure. To that end, the accompanying drawings and detailed description are provided. Therefore, among the components described in the attached drawings and the detailed description, not only the components essential for solving the problem but also the components not essential for solving the problem in order to exemplify the above technology. Can also be included. Therefore, the fact that these non-essential components are described in the accompanying drawings or detailed description should not immediately determine that those non-essential components are essential.

Further, since the above-described embodiment is for exemplifying the technique in the present disclosure, various changes, replacements, additions, omissions, etc. can be made within the scope of claims or the equivalent scope thereof.

(Outline of Embodiment)
(1) The laser light source device of the present disclosure includes a plurality of laser elements, a diffracting optical element that diffracts laser light emitted from each laser element, and a collimating lens 15 that makes each laser light parallel light. , Each laser element emits laser light having different wavelengths from each other, and the diffractive optical element has a serrated portion in which a plurality of linear grooves are formed in parallel, and each laser element is a collimating lens. In the cross-sectional view including the optical axis of, the collimated lens is arranged on one side of the optical axis at a position different from the optical axis, and the respective laser beams emitted from the respective laser elements are diffracted by the diffractive optical element. It is diffracted and synthesized with different diffraction orders.

In this way, it is possible to generate a parallel beam with improved diffraction efficiency by generating each diffracted light at each wavelength and converting the diffracted light into parallel light.

(2) In the laser light source device of (1), the extending direction of the groove of the sawtooth shape portion is orthogonal to the cross section including the optical axis of the collimating lens.

(3) In the laser light source device of (1) or (2), the serrations of the diffractive optical element are synthesized so that each laser beam emitted from each laser element is diffracted and synthesized with a diffraction efficiency of 91% or more. The height of the shape portion is a value in a predetermined range. The height of the sawtooth-shaped portion of the diffractive optical element may be determined so that each laser beam emitted from each laser element is diffracted and synthesized with a diffraction efficiency of 91% or more.

(4) In any one of the laser light source devices (1) to (3), the wavelength of each laser beam emitted from each laser element is λp, and the refractive index of the diffractive optical element at each wavelength is np. When the height of the blaze 13a, which is the serrated portion of the diffraction optical element, is d, and the diffraction order at each wavelength, which is the combination of the maximum diffraction efficiencies, is mp, mp is an integer other than 0.
Satisfy −0.175 <d (np-1) / λp-mp <0.175.

(5) In the laser light source device of (4),
Satisfy −0.1 <d (np-1) / λp-mp <0.1. Thereby, the diffraction efficiency can be further improved.

(6) In any one of the laser light source devices (1) to (5), one of the laser elements emits a laser beam having a blue wavelength, and one of the laser elements emits a laser light having a green wavelength. One of the laser elements emits a laser beam having a red wavelength.

(7) In the laser light source device of (6), in the diffractive optical element, laser beams having different wavelengths are generated and synthesized into laser beams having a diffraction order of at least 4th order or higher.

(8) In the laser light source device of (6) or (7), when the wavelengths of the three laser elements having the wavelengths of blue, green, and red are λ1, λ2, and λ3,
450nm <λ1 <475nm,
500nm <λ2 <540nm,
625nm <λ3 <650nm,
Meet.

(9) In any one of the laser light source devices (1) to (8), the respective laser elements are arranged at different positions in the optical axis direction of the collimating lens.

(10) In any one of the laser light source devices (1) to (9), the diffractive optical element and the collimating lens are integrated. This makes it possible to save space in the laser light source device.

(11) One of the laser light source devices (1) to (10), a first rotating mirror that scans laser light having a plurality of wavelengths emitted from the laser light source device in the first direction, and a first rotating mirror. An image forming apparatus including a second rotating mirror that scans a laser beam emitted from a laser beam in a second direction orthogonal to the first direction.

The present disclosure is applicable to a laser light source device that emits laser light having a plurality of wavelengths.

1 Light source device 2 Laser light source 3 Red laser element 5 Green laser element 7 Blue laser element 13 Diffraction grating 13a Blaze 15, 15A, 15B, 15C, 15D, 15E, 15F Collimating lens 16 Aspherical surface 19A, 19E Diffraction lens 21 Image forming device 23 Condensing lens 25 1st scanning element 27 2nd scanning element 29 Control unit 31 Screen Pb Grating pitch Hb Grating height BL Blue laser light GL Green laser light RL Red laser light

Claims (11)

With multiple laser elements
A diffractive optical element that diffracts the laser light emitted from each of the laser elements,
A collimated lens that converts each of the laser beams into parallel light is provided.
Each of the laser elements emits laser light having different wavelengths from each other.
The diffractive optical element has a sawtooth-shaped portion in which a plurality of linear grooves are formed in parallel with each other.
Each of the laser elements is arranged on one side of the optical axis of the collimating lens at a position different from the optical axis in a cross-sectional view including the optical axis of the collimating lens.
Each laser beam emitted from each laser element is diffracted and synthesized by the diffractive optical element at different diffraction orders.
Laser light source device. The extending direction of the groove of the sawtooth shape portion is orthogonal to the cross section including the optical axis of the collimating lens.
The laser light source device according to claim 1. The height of the serrated portion of the diffractive optical element is within a predetermined range so that each laser beam emitted from each laser element is diffracted and synthesized with a diffraction efficiency of 91% or more. is there,
The laser light source device according to claim 1 or 2. Let λp be the wavelength of each laser beam emitted from each of the laser elements.
Let np be the refractive index of the diffractive optical element at each of the wavelengths.
Let d be the height of the serrated portion of the diffractive optical element.
When the diffraction order at each of the wavelengths, which is the combination of the maximum diffraction efficiencies, is mp,
mp is a non-zero integer
−0.175 <d (np-1) /λp-mp <0.175
The laser light source device according to any one of claims 1 to 3, which satisfies the above conditions. -0.1 <d (np-1) /λp-mp <0.1
The laser light source device according to claim 4. One of the laser elements emits a laser beam having a blue wavelength.
One of the laser elements emits a laser beam having a green wavelength.
One of the laser elements emits a laser beam having a red wavelength.
The laser light source device according to any one of claims 1 to 5. In the diffractive optical element, the laser beams having different wavelengths are generated and synthesized into laser beams having a diffraction order of at least 4th order or higher.
The laser light source device according to claim 6. When the wavelengths of the three laser elements having the wavelengths of blue, green, and red are λ1, λ2, and λ3,
450nm <λ1 <475nm,
500nm <λ2 <540nm,
625nm <λ3 <650nm,
Meet,
The laser light source device according to claim 6 or 7. Each of the laser elements is arranged at a different position in the optical axis direction of the collimating lens.
The laser light source device according to any one of claims 1 to 8. The diffractive optical element and the collimating lens are integrated.
The laser light source device according to any one of claims 1 to 9. The laser light source device according to any one of claims 1 to 10 and
A first scanning element that scans a laser beam having a plurality of wavelengths emitted from the laser light source device in the first direction, and a first scanning element.
A second scanning element that scans the laser beam emitted from the first scanning element in a second direction orthogonal to the first direction, and a second scanning element.
An image forming device equipped with.

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