JP2021158170A - Laser light source module - Google Patents

Abstract

To provide a laser light source module that can reduce a difference between wavelengths of change in a traveling direction of the laser light generated by change in an environmental temperature even when a plurality of laser light sources having different wavelengths of the emitted light is used.SOLUTION: A laser light source module has: a laser light source 100; a collimating lens 120 that converts synchrotron radiation from a laser light source into beam light, and a beam shaping prism 19 that shapes a beam shape of beam light, and the laser light source and the beam shaping prism are arranged such that first angular deviation due to deviation of the laser emission point position due to change in an environmental temperature of the laser light source, and second angle deviation which is emission angle deviation of the beam shaping prism that changes due to change in a refractive index of the beam shaping prism corresponding to the change in the wavelength of the laser due to the change in the environmental temperature of the laser light source are cancelled with each other.SELECTED DRAWING: Figure 6

Description

The present invention relates to a laser light source module having a plurality of laser light sources having different wavelengths of emitted light.

Patent Document 1 is provided as a background technique for an image drawing device such as a projector or a head-up display device using a laser light source module. In Patent Document 1, the blue, red, and green laser beams emitted from the light source unit are scanned in two directions by the optical scanning unit, and an image is displayed on the screen. In the light source unit, a laser light source of three colors of blue, red, and green, three light source holding units for individually holding the laser light sources of the three colors, and light emitted from the laser light source of each color are parallel to each other. It is provided with three collimating lenses that convert light and three optical system holding portions for individually holding the three collimating lenses, and the light source holding portion and the optical system holding portion are laser-welded for each color. Therefore, the light source holding portion and the optical system holding portion are fixed in a state of being positioned with high accuracy, and it is said that the state can be maintained even against disturbances such as vibration, impact, and temperature change.

Japanese Unexamined Patent Publication No. 2016-18206

The laser light source often used in the image drawing device as described above has a structure in which a plurality of components are joined to each other, and since the thermal expansion coefficients of the plurality of components are different, the laser chip is affected by thermal stress when the environmental temperature changes. The position of the light emitting point is displaced due to warpage. Since the laser light travels in the direction connecting the light emitting point and the principal point of the collimating lens, the displacement of the light emitting point changes the traveling direction of the laser light, and the traveling direction of the laser light shifts. Since the laser chip length of the laser light source differs depending on the wavelength of the emitted light, the laser light sources of the three colors of blue, red, and green have the displacement of the light emitting point caused by the warp of the laser chip and the accompanying direction of the laser light. The degree of change also varies from wavelength to wavelength. The effect of the difference between the wavelengths of the change in the traveling direction increases in proportion to the irradiation distance, which causes color shift on the screen.

The above-mentioned Patent Document 1 does not consider the thermal deformation that occurs inside the laser light source, and there is a possibility that color shift may occur on the screen when the ambient temperature changes.

An object of the present invention is a laser light source module capable of reducing the difference between wavelengths of changes in the traveling direction of laser light generated by a change in environmental temperature even when a plurality of laser light sources having different wavelengths of emitted light are used. Is to provide.

In view of the above background techniques and problems, the present invention includes a laser light source, a collimating lens that converts light emitted from the laser light source into beam light, and a beam shaping prism that shapes the beam shape of the beam light. A beam shaping prism that corresponds to the first angular deviation due to the deviation of the emission point position of the laser due to the change in the environmental temperature of the laser light source and the change in the wavelength of the laser due to the change in the environmental temperature of the laser light source. The laser light source and the beam shaping prism are arranged so as to cancel the second angle deviation, which is the emission angle deviation of the beam shaping prism that changes due to the change in the refractive index.

According to the present invention, in a laser light source module including a plurality of laser light sources having different wavelengths of emitted light, the difference between the wavelengths of the angle change of the traveling direction of the laser light generated with the change of the environmental temperature is reduced. A capable laser light source module can be provided.

It is a schematic block diagram of the scanning image display apparatus to which the laser light source module in an Example is applied. It is a figure explaining the structure of the semiconductor laser used as a laser light source in an Example. It is a schematic diagram which showed the state which the laser light emitted from the laser light source in an Example irradiate a screen through a lens. It is a figure explaining the characteristic of the beam shaping prism in an Example. It is a figure which shows the relationship between the refractive index and the wavelength of the beam shaping prism in an Example. It is a schematic diagram explaining the structure which reduces the amount of color shift on the screen by the change of the environmental temperature in an Example. This is a calculation result in which the amount of color shift is reduced by the configuration in the embodiment. This is a calculation result in which the amount of color shift when the glass material of the beam shaping prism in FIG. 7 is changed is reduced. This is a calculation result in which the amount of color shift is reduced when the compression ratio of the beam shaping prism in FIG. 8 is reduced.

Hereinafter, examples of the present invention will be described in detail with reference to the drawings.

This embodiment will be described by taking a scanning image display device to which the laser light source module is applied as an example.

FIG. 1 is a schematic configuration diagram of a scanning image display device to which the laser light source module in this embodiment is applied. The dotted line in FIG. 1 represents the optical path of the laser beam. The scanning image display device 1 in the present embodiment has a laser light source module 10 that emits a laser beam for image display and an optical scanning unit 20 that scans the laser beam emitted from the laser light source module 10 in two dimensions as main optical components. It is configured as.

The laser light source module 10 is arranged with three laser light sources 11, 12 and 13 that emit light having different wavelengths from each other.

The laser light source 13 is a semiconductor laser that emits a green (G) laser beam having an intermediate wavelength among the three laser light sources. The green laser light emitted by the laser light source 13 passes through the collimating lens 16 and is converted into substantially parallel laser light, and then is incident on the dichroic mirror 17.

The laser light source 12 is a semiconductor laser that emits a blue (B) laser beam having the shortest wavelength among the three laser light sources. The blue laser light emitted by the laser light source 12 passes through the collimating lens 15 and is converted into substantially parallel laser light, and is incident on the dichroic mirror 17.

The dichroic mirror 17 is a wavelength-selective optical element having a function of transmitting the green laser light emitted from the laser light source 13 while reflecting the blue laser light emitted from the laser light source 12, and transmits the dichroic mirror 17. Alternatively, the reflected two-color laser light travels in substantially the same optical path that is aligned with the traveling direction and is incident on the dichroic mirror 18.

The laser light source 11 is a semiconductor laser that emits a red (R) laser beam having the longest wavelength among the three laser light sources. Hereinafter, the laser light source 11 will be referred to as a first laser light source, and the laser light sources 12 and 13 will be referred to as second and third laser light sources. The red laser light emitted by the first laser light source 11 passes through the collimating lens 14 and is converted into substantially parallel laser light, and then is incident on the dichroic mirror 18.

The dichroic mirror 18 is a wavelength-selective optical element having a function of reflecting green and blue laser light and transmitting only red laser light. The green, blue, and red laser beams transmitted or reflected through the dichroic mirror 18 travel in substantially the same optical path in the same traveling direction and position, and scan the laser beam through the beam shaping prism 19. It is incident on the scanning unit 20.

In other words, the laser light source module 10 converts the laser light emitted from the laser light sources 11, 12, and 13 of R, B, and G and the laser light emitted from each laser light source into beam light which is substantially parallel laser light. Collimating lenses 14, 15 and 16, a beam coupling part consisting of dichroic mirrors 17 and 18 for aligning each beam light on one beam light path, and a beam of laser light aligned on one beam light path. It has a beam shaping prism 19 that shapes the shape.

The optical scanning unit 20 is provided with a reflection mirror 21 in the apparatus, and has a function of inclining the reflection surface around two axes. The optical scanning unit 20 reflects the incident laser light and scans it in two directions on the screen 30 separated by a predetermined distance to draw an image.

FIG. 2 is a diagram illustrating a structure of a semiconductor laser used as a laser light source in this embodiment. In FIG. 2, FIG. 2A is a perspective view showing a structure of a semiconductor laser corresponding to laser light sources 11, 12, and 13. In (a), the laser light source has a structure in which a disk-shaped pedestal called a stem is sealed with a can-shaped metal, but in order to make the internal structure easier to see, the stem 113, the heat sink 112, and the submount 111 , And only the laser chip 110 is described. The laser chip 110 is joined to the flat surface of the semi-cylindrical heat sink 112 connected to the stem 113, which is a disk-shaped pedestal, via a submount 111.

Since such a laser light source is constructed by joining members having different coefficients of thermal expansion, the laser chip warps due to thermal stress when the ambient temperature changes, and the position of the light emitting point is displaced.
2 (b) and 2 (c) are schematic cross-sectional schematic views seen from the direction of the white arrow in (a). (B) shows the case where the ambient temperature is the standard temperature, and (c) shows the case where the ambient temperature rises.

Since the coefficient of thermal expansion of the heat sink 112 is larger than that of the laser chip 110 and the submount 111, when the ambient temperature rises, the laser chip 110 is on the left side in the figure, that is, on the heat sink 112, as shown in (c). Warp to the other side. As a result, the position of the emission point of the laser beam is displaced to the left as indicated by the arrow. Note that (c) shows an example when the environmental temperature rises, but since the displacement of the light emitting point is almost proportional to the temperature change and the coefficient of linear expansion of each part, when the environmental temperature falls, the displacement The direction is reversed.

The magnitude of the warp of the laser chip 110 is proportional to the length of the laser chip determined by the wavelength of the light emitted by the laser light source. That is, in FIG. 1, the warp of the laser chip is remarkable in the first laser light source 11 which emits light having the longest wavelength among the three laser light sources and is equipped with the longest laser chip. In the second and third laser light sources 12 and 13, which emit light having a wavelength shorter than that of the first laser light source 11 and whose laser chip length is shorter than that of the first laser light source 11, the warp of the laser chip is also small. Therefore, the displacement of the position of the emission point of the laser beam due to the warp of the laser chip is different for each RGB laser light source.

Next, the relationship between the change in the position of the emission point of the laser beam and the deviation of the traveling angle in the traveling direction of the laser beam through the lens will be described. FIG. 3 is a schematic view showing a state in which the laser light emitted from the laser light source is applied to the screen through the lens. In FIG. 3, when the emission point of the laser light of the laser light source 100 is shifted to the left side in the drawing by Δa, the laser light passes through the lens 120, so that the traveling angle of the laser light is shifted, and the figure is shown on the screen 30. It will shift to the right on the top. When the distance b between the lens and the screen is longer than the distance a between the emission point of the laser beam and the lens, the amount of deviation Δb on the screen is larger than Δa.

Further, as described above, the displacement of the position of the emission point of the laser light due to the warp of the laser chip caused by the change in the environmental temperature is different for each RGB laser, which causes color shift on the screen.

Here, the beam shape of the semiconductor laser differs between the vicinity of the output end of the semiconductor laser and the location away from the output end. The beam pattern FFP (Far Field Pattern) at a distant place has different light emission angles in the horizontal direction and the vertical direction of the laser chip. Therefore, in order to improve the light utilization efficiency of the laser light source module, a method of arranging a wedge-shaped beam shaping prism and compressing FFP in a direction having a relatively wide divergence angle is adopted.

FIG. 4 is a diagram illustrating the characteristics of the beam shaping prism. In FIG. 4, the beam shaping prism 19 changes the traveling angle of the laser beam with _{respect to the incident light A at an angle θ 2 from the emission surface to the normal line thereof.} Assuming that the angle formed by the normal of the exit surface and the incident light is θ ₁ , the apex angle is θ ₃ , the refractive index of the glass material constituting the beam shaping prism 19 is n ₁ , and the refractive index in the air is n ₂ .
n ₁ sinθ ₁ = n ₂ sinθ ₂
From n ₂ = 1.0, n ₁ sinθ ₁ = sinθ ₂
θ ₂ = sin ^-1 (n ₁ sin θ ₁ )
Since θ ₃ = θ ₁ ,
θ ₂ = sin ^-1 (n ₁ sin θ ₃ ) ... Equation (1)
Will be.
_{That is, the traveling angle θ 2} of the laser beam, which is the light emitted from the beam shaping prism, is determined by _{the refractive index n 1} of the beam shaping prism 19 and its apex angle θ _3.

Here, the wavelength of the laser of the laser light source changes due to a change in the environmental temperature, and the wavelength becomes longer as the temperature rises. On the other hand, the refractive index n _{1 of the} glass material constituting the beam shaping prism 19 generally decreases as the wavelength becomes longer, as shown in FIG. _{That is, the refractive index n 1} of the beam shaping prism changes due to the change in the environmental temperature, and the emission angle shift of the beam shaping prism occurs.

Therefore, by arranging the installation angle of the laser light source and the installation angle of the beam shaping prism so as to cancel the angle deviation due to the deviation of the emission point position of the laser light source and the emission angle deviation of the beam shaping prism, as a result, the screen It is possible to reduce the amount of color shift above.

FIG. 6 is a schematic diagram illustrating a configuration for reducing the amount of color shift on the screen due to a change in the environmental temperature in this embodiment. In FIG. 6, the same configurations as those in FIG. 3 are designated by the same reference numerals, and the description thereof will be omitted. In FIG. 6, the difference from FIG. 3 is that the beam shaping prism 19 is arranged after the lens 120 with respect to the traveling direction of the laser light from the laser light source 100.

In FIG. 6A, when the ambient temperature rises and the emission point of the laser beam of the laser light source 100 shifts to the left side in the drawing by Δa, the deviation of the traveling angle of the laser beam after passing through the lens 120 is It is on the right side in the figure. On the other hand, as the ambient temperature rises, the wavelength of the laser beam becomes longer and the refractive index n ₁ of the beam shaping prism 19 becomes smaller. _{Therefore, according to the equation (1), the traveling angle θ 2} of the laser beam, which is the light emitted from the beam shaping prism, becomes small. Therefore, the deviation of the traveling angle of the laser beam after passing through the beam shaping prism 19 works to be corrected to the left side in the drawing. On the other hand, when the beam shaping prism 19 is arranged symmetrically with respect to FIG. 6A as shown in FIG. 6B, the deviation of the traveling angle of the laser light after passing through the beam shaping prism 19 is shown in FIG. It works to amplify to the right on the top. Therefore, as the amount of deviation on the screen 30, Δc in FIG. 6A can be made smaller than Δd in FIG. 6B. This makes it possible to reduce the amount of color shift on the screen.

FIG. 7 is a calculation result in which the amount of color shift is reduced by the configuration in this embodiment. In FIG. 7, as a condition, the amount of change in angle due to each of the RGB laser light sources when the environmental temperature is changed from 65 ° C. to 35 ° C. is shown. The optical glass material of the beam shaping prism is a glass material BK7 and a compression ratio of 2.1. Here, the compression ratio is the ratio of the beam diameter of the incident light A and the beam diameter of the emitted light B in FIG. In FIG. 7, the screen incident angle deviation 200 due to the deviation of the emission point position of the laser light source, the emission angle deviation 300 of the beam shaping prism, the screen incident angle deviation 200 due to the deviation of the emission point position of the laser light source, and the beam shaping prism. Normalized total angle based on the total angle change 400 canceled by the emission angle deviation 300 and the total angle change due to the green (G) laser light source, which is an intermediate wavelength among the RGB laser light sources in the result of the total angle change 400. It shows a change of 500. That is, the screen incident angle deviation 200 due to the deviation of the emission point position of the laser light source is canceled by the emission angle deviation 300 of the beam shaping prism, and the total angle change 400 is the screen incident angle deviation due to the deviation of the emission point position of the laser light source. It is smaller than 200.

FIG. 8 is a calculation result in which the glass material of the beam shaping prism is changed under the conditions of FIG. 7 and the amount of color shift is reduced by the configuration in this embodiment. That is, in FIG. 8, the glass material of the beam shaping prism is ZF2, and the material of the prism is changed, and other conditions are the same as in FIG. 7. In FIG. 8, the emission angle deviation 300 of the beam shaping prism is larger than that in FIG. 7, and the normalized total angle change 500 is smaller in the laser light source of R and larger in the laser light source of B than in FIG. However, the result is that the R and B laser light sources are well-balanced as a whole.

FIG. 9 shows a calculation result in which the amount of color shift is reduced by the configuration in this embodiment when the compression ratio of the beam shaping prism is reduced from 2.1 to 1.81 under the conditions shown in FIG. Reducing the compression ratio means reducing the apex angle θ _{3 , and according to Eq. (1), the traveling angle θ 2} of the laser beam, which is the light emitted from the beam shaping prism, is reduced. Therefore, the emission angle deviation 300 of the beam shaping prism is smaller than that in FIG. As a result, the normalized total angle change 500 is the same for the laser light source of R as compared with FIG. 8, and is smaller for the laser light source of B, so that the amount of color shift can be further reduced.

As described above, according to the present embodiment, in a laser light source module provided with a plurality of laser light sources having different wavelengths of emitted light, between wavelengths of an angular change in the traveling direction of the laser light generated with a change in the environmental temperature. It is possible to provide a laser light source module capable of reducing the difference between the two.

Although the examples have been described above, the present invention is not limited to the above-mentioned examples, and various modifications are included. For example, the above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to those having all the described configurations.

1: Scanning image display device, 10: Laser light source module, 11, 12, 13, 100: Laser light source, 14, 15, 16: Collimating lens, 17, 18: Dicroic mirror, 19: Beam shaping prism, 20: Light Scanning unit, 21: Reflective mirror, 30: Screen, 110: Laser chip, 111: Submount, 112: Light source, 113: Stem, 120: Lens

Claims (8)

A laser light source module having a laser light source, a collimating lens that converts synchrotron radiation from the laser light source into beam light, and a beam shaping prism that shapes the beam shape of the beam light.
Changes due to a first angular shift due to a shift in the position of the emission point of the laser due to a change in the environmental temperature of the laser light source and a change in the refractive index of the beam shaping prism corresponding to a change in the wavelength of the laser due to a change in the environmental temperature of the laser light source. A laser light source module characterized in that the laser light source and the beam shaping prism are arranged so as to cancel the second angle deviation which is the emission angle deviation of the beam shaping prism. In the laser light source module according to claim 1.
A laser light source module characterized in that the emission angle deviation of the beam shaping prism is adjusted by changing the material of the beam shaping prism to cancel the first angle deviation and the second angle deviation. .. In the laser light source module according to claim 1.
A laser light source module characterized in that the emission angle deviation of the beam shaping prism is adjusted by the compression ratio of the beam shaping prism to cancel the first angle deviation and the second angle deviation. A plurality of laser light sources, a plurality of collimating lenses that convert the synchrotron radiation from each laser light source into beam light, a beam coupling part for aligning each beam light on one beam optical axis, and one beam. A laser light source module having a beam shaping prism that shapes the beam shape of laser light aligned on the optical axis.
Changes due to a first angular shift due to a shift in the position of the emission point of the laser due to a change in the environmental temperature of the laser light source and a change in the refractive index of the beam shaping prism corresponding to a change in the wavelength of the laser due to a change in the environmental temperature of the laser light source. A laser light source module characterized in that the laser light source and the beam shaping prism are arranged so as to cancel the second angle deviation which is the emission angle deviation of the beam shaping prism. In the laser light source module according to claim 4.
The plurality of laser light sources are R, B, and G laser light sources.
The beam coupling unit is a laser light source module characterized by comprising two dichroic mirrors. In the laser light source module according to claim 4.
A laser light source module characterized in that the emission angle deviation of the beam shaping prism is adjusted by changing the material of the beam shaping prism to cancel the first angle deviation and the second angle deviation. .. In the laser light source module according to claim 4.
A laser light source module characterized in that the emission angle deviation of the beam shaping prism is adjusted by the compression ratio of the beam shaping prism to cancel the first angle deviation and the second angle deviation. In the laser light source module according to claim 5.
In the total angle change after canceling the first angle deviation and the second angle deviation from each other, the total angle change in the laser light source of G having an intermediate wavelength among the laser light sources of R, B, and G is used. A laser light source module characterized in that the laser light source and the beam shaping prism are arranged as a reference.

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