TW201600880A - Collimator lens - Google Patents

Abstract

The purpose of the present invention is to provide a collimator lens having a high NA, and improved lens transmittance. According to the present invention, there is provided a collimator lens (1) comprising a glass material, for converting light rays of 380 to 700 nm wavelength outputted from a light source (S) into a parallel beam, wherein the opposite side from the surface facing the light source has a surface provided with a protruding portion; the numerical aperture (NA) is 0.6 or above; the ratio (t/f) of the center lens thickness to the focal distance (f) is 1.3 or below; the maximum surface angle of the surface provided with the protruding portion is 65 DEG or less; the refractive index (nd) is 1.59 or greater; and the total content of TiO2, WO3, Nb2O5, and Bi2O13 of the glass material is 0-40 wt%.

Description

Collimating lens

The present invention relates to collimating lenses, and more particularly to collimating lenses for converting light from a source into parallel light.

A collimating lens is known which converts a divergent beam from a source such as a laser source into a lens of parallel light.

As such a collimator lens, for example, a collimator lens attached to an optical system of a projection type image display device using a laser light source is known (Patent Documents 1 and 2).

In the collimator lens of Patent Document 1, since the change in the operating distance (working distance) accompanying the temperature rise is suppressed, the chromatic aberration characteristics are improved. Further, the lens is characterized in that the wavelength of the laser light source is 375 nm or more and 750 nm or less, and the numerical aperture is 0.2 or more and 0.75 or less. (1) The thickness of the lens is D, and the focal length of the lens is set to In the case of f, D/f>0.85 holds, and (2) when the Abbe number is set to νd, ν d>57 holds.

Further, in the collimator lens of Patent Document 2, in order to prevent an increase in the image spot of the collimated parallel light, the surface on the light source side (the first surface) and the surface on the emission side of the lens ( The second surface is convex, and a diffraction structure is provided on at least one of the first surface and the second surface.

Patent Document 1: International Publication WO2010/116862

Patent Document 2: Japanese Laid-Open Patent Publication No. 2011-145387

For example, in the case of a projection type image display device, a collimator lens converts a divergent light beam emitted from a light source such as a laser light source into a parallel light beam as a main function. In recent years, with the demand for enlargement and high definition of projection images, it is required to increase the brightness of an image display device. Along with this, the collimating lens used in the optical system of the image display device is required to have high NA and high lens transmittance.

The present invention has been made in view of the above problems, and an object thereof is to provide a collimating lens having a high NA and improved lens transmittance.

According to the present invention, there is provided a collimating lens which is a collimating lens composed of a glass material, and the collimating lens converts light having a wavelength of 380 nm to 700 nm emitted from a light source into a parallel beam, wherein the surface facing the light source is On the opposite side, the surface having the convex portion is provided, the numerical aperture NA is 0.6 or more, the ratio t/f of the central lens thickness t to the focal length f is 1.3 or less, and the maximum surface angle of the surface on which the convex portion is provided is 65°. Hereinafter, the refractive index nd of the glass material is 1.59 or more, and the total content of TiO ₂ , WO ₃ , Nb ₂ O ₅ , and Bi ₂ O ₃ of the glass material is 0 to 40% by weight.

According to the present invention, a collimating lens having a high NA and improved lens transmittance is provided.

1‧‧‧ collimating lens

2‧‧‧The side of the light source side

4‧‧‧The side of the exit side

S‧‧‧ light source

t‧‧‧Center lens thickness

F‧‧•focal length

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic side view showing the shape of a collimating lens of a preferred embodiment of the present invention.

Fig. 2 is a block diagram schematically showing the configuration of a light source unit of the projection type image display device in which the collimator lens of Fig. 1 is mounted.

Fig. 3 is a block diagram schematically showing the configuration of a light source portion of another projection type image display device in which the collimator lens of Fig. 1 is mounted.

Fig. 4 is a schematic side view showing the shape of a collimator lens according to another preferred embodiment of the present invention.

Fig. 5 is a schematic side view showing the shape of a collimator lens according to another preferred embodiment of the present invention.

Fig. 6 is a schematic side view showing the shape of a collimator lens according to still another preferred embodiment of the present invention.

Fig. 7 is a view for explaining the configuration of an example of an aspherical surface used in the collimating lens of the present invention.

Fig. 8 is a view showing the relationship between the maximum surface angle of the surface on the exit side of the lens and the transmittance of the lens in the NA-based 0.6 or more lens of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. 1 is a schematic side view showing the shape of a collimator lens 1 of a preferred embodiment of the present invention. The collimator lens 1 of the present embodiment is a glass lens for converting light having a wavelength of 380 nm to 700 nm emitted from a light source such as a laser device into parallel light. Specifically, it is used, for example, in an optical system of a projection type image display device such as a liquid crystal projector.

As shown in Fig. 1, the collimator lens 1 is a single lens having a so-called lenticular lens shape in which an annular edge portion is provided on the outer edge. In detail, in making The two surfaces of the surface (the surface on the light source side) 2 facing the light source S and the surface (the surface on the emission side) 4 opposite to the surface 2 on the light source side have a convex shape. In the present embodiment, the two faces of the face 2 on the light source side and the face 4 on the exit side are spherical surfaces. Further, the collimator lens 1 has a flange-shaped edge portion 6 at the outer edge portion. Further, the edge portion 6 is useful for a lens fixing member that is fixed to the inside of the device when mounted to a projection type image display device or the like, but the edge portion 6 may not be provided.

The maximum surface angle of the surface 2 on the exit side of the collimator lens 1 is preferably 65 or less. The maximum surface angle is more preferably 55° or less, still more preferably 50° or less. Further, the plane angle θ means an angle formed by a normal line at one position in the effective diameter on the lens surface and the lens central axis Z. When the maximum surface angle is 65° or less, the lens workability such as press formability, grinding or polishing workability is good, and the shape evaluation of the lens can be further facilitated.

Further, t/f (t: central lens thickness, f: focal length) of the collimator lens 1 is preferably 1.3 or less. The reason for this is that if t/f exceeds 1.3, it is not possible to secure a practically sufficient working distance (working distance) (WD), for example, WD of 1 mm or more. The t/f is preferably less than 1.20. In addition to ensuring sufficient WD, from the viewpoint of lens processability, t/f is preferably 0.3 to 1.3, more preferably 0.3 to 0.85, still more preferably 0.3 to 0.80.

Further, the upper and lower limits of t/f will be described in detail. From the viewpoint of securing WD, the upper limit of t/f is preferably in the order of 1.20 or less, 1.00 or less, 0.80 or less, and 0.70 or less. From the viewpoint of lens workability, the lower limit of t/f is preferably 0.30 or more, 0.40 or more, or 0.50 or more.

In addition, in the present specification, "Working Distance (WD)" means, for example, as shown in FIG. 1, the light source S, The distance between the point-like light-emitting portion in the light source and the portion of the surface 2 of the light source side of the collimator lens 1 that is closest to the light source is described in detail.

Further, the numerical aperture NA of the collimator lens 1 is 0.6 or more. In order to secure WD and to make the maximum surface angle 65 or less, the upper limit of NA is preferably 0.9 or less.

Further, the upper limit of NA may be 0.85 or less, 0.80 or less, or 0.75 or less. The lower limit of NA may be more than 0.6 (0.6 <), 0.65 or more, 0.70 or more, or 0.71 or more.

In the method of manufacturing the collimator lens 1, there are a method based on precision press molding, grinding processing, and polishing processing, and a glass material is used in the above method.

As a material for forming the collimator lens 1, for example, a glass material (glass I, glass II) having the following two types of composition can be used.

The glass I contains B ₂ O ₃ and contains a glass material selected from at least one of rare earth oxides such as La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ .

The glass II contains P ₂ O ₅ and contains a glass material selected from at least one of Nb ₂ O ₅ , WO ₃ , TiO ₂ and Bi ₂ O ₃ .

For the glass material forming the collimator lens 1, the total content of TiO ₂ , WO ₃ , Nb ₂ O ₅ , and Bi ₂ O _{3 in} the glass I or the glass II is preferably 0 to 40% by weight. The total content of TiO ₂ , WO ₃ , Nb ₂ O ₅ , and Bi ₂ O ₃ is preferably from 0 to 28% by weight, and more preferably from 0 to 16% by weight, from the viewpoint of improving the pressability and the like.

Further, as the glass material forming the collimator lens 1, in the glass I, TiO ₂ + WO ₃ + Nb ₂ O ₅ + Bi ₂ O ₃ / ((total content of rare earth oxides) from the viewpoint of lens transmittance +Ta ₂ O ₅ ) 1.1 is preferred. The ratio is more preferably 0.9 or less, and still more preferably 0.5 or less.

The refractive index nd of the material forming the collimator lens 1 is 1.59 or more. The refractive index nd is more preferably 1.68 or more, further preferably 1.75 or more, and still more preferably 1.80 or more. The reason for this is that the refractive index nd is such that the maximum surface angle of the surface on the emission side can be reduced.

The Abbe number of the glass material forming the collimator lens 1 is preferably 57 or less from the viewpoint of maintaining a high refractive index of the refractive index nd of 1.59 or more. Further, from the viewpoint of high refractive index, the upper limit of the Abbe number is more preferably 50 or less, or 45 or less. The lower limit of the Abbe number is not particularly limited, and may be 20 or more.

Further, from the viewpoint of the suitability for precision press molding, the glass transition temperature Tg of the glass material forming the collimator lens 1 is formed. 630 ° C is preferred.

In association with this, in the glass material forming the collimator lens 1, the ZnO content is preferably 3% by weight or more, more preferably 8% by weight or more, and still more preferably 10% by weight or more, because it contributes to lowering Tg.

In the collimator lens 1 of the present embodiment, the total content of WO ₃ , Nb ₂ O ₅ , and Bi ₂ O ₃ is suppressed to 40% by weight or less, so that the lens transmittance is improved, and the emission from the laser light source can be improved. The efficiency of light utilization.

Further, in the collimator lens 1, since the utilization efficiency of the emitted light from the laser light source is improved, the brightness of the projected image in the projection type image display device is improved.

At present, a laser light source (Laser Diode (LD)), especially a high output of a green laser, is a subject, but high output is not easy. However, if the transmittance of the collimating lens is improved, even if the laser output is low, the brightness of the projected image is improved, and a sufficient projected image can be obtained. Further, also Can achieve low power consumption.

2 is a block diagram schematically showing a configuration of a light source unit (illumination optical system) 10 of a projection type image display device (for example, a liquid crystal projector) to which the collimating lens of the present embodiment is mounted 1.

As shown in FIG. 2, the light source unit 10 includes three laser devices R, G, and B that generate red light, green light, and blue light, respectively, and are disposed on the downstream side of the laser (LD) devices R, G, and B, respectively. Collimating lens 1. The collimator lens 1 converts the divergent light emitted by each of the laser devices R, G, and B into parallel light.

In the light source unit 10, multiplexer optical system 12 including a dichroic prism or the like is used to multiplex red light, blue light, and green light which are collimated by the collimator lenses 1 and become parallel light, and Transfer to the projection optics.

3 is a block diagram schematically showing the configuration of a light source unit (illumination optical system) 14 of another projection type image display device (for example, a liquid crystal projector) to which the collimation of the present embodiment is mounted. Lens 1.

As shown in FIG. 3, the light source unit 14 includes a monochromatic light source (LD) 16 similar to a near-ultraviolet laser device, and a collimator lens 1 is disposed on the downstream side of the monochromatic light source 16. The collimator lens 1 converts the light emitted by the monochromatic light source 16 into parallel light.

The light source unit 14 includes a conversion unit 18 that includes three portions that convert near-ultraviolet light into red light, blue light, and green light. In the conversion unit 18, three portions converted into red light, blue light, and green light are sequentially arranged on the optical path of the near-ultraviolet light, and the near-ultraviolet light is converted into red light, blue light, and green light at regular intervals. And, the red light, the blue light, and the green light are sequentially sent to the projection optical system.

For example, the collimator lens 1 of this embodiment has a so-called double convex shape. A collimating lens, however, the invention is not limited to such a biconvex shaped collimating lens. The collimator lens of the present invention has a surface on which a convex portion is provided on the side opposite to the surface facing the light source, and further has specific conditions.

Therefore, for example, the outer shape as shown in FIGS. 4 to 6 can be provided. That is, the plano-convex lens 104 shown in Fig. 4 may be used, in which the edge portion facing the light source S is not provided with an edge portion, and the surface 4 opposite to the surface 2 facing the light source S is convex. It is advantageous in securing the working distance (WD) and lens workability by making the surface facing the light source flat. Further, there is no problem of eccentricity (decenter) between the surface 2 facing the light source and the surface 4 on the opposite side.

Further, a lenticular lens 105 as shown in FIG. 5 may be used, in which the surface portion facing the light source S is not provided with an edge portion, and the surface 4 opposite to the surface 2 facing the light source S is also convex. Further, a convex meniscus lens 106 as shown in FIG. 6 may be provided, in which the surface 2 facing the light source S is not provided with an edge portion, and the surface 4 opposite to the surface facing the light source S is convex.

In the collimator lens 1 of the above embodiment, the two faces facing the surface 2 of the light source and the face 4 on the opposite side are spherical surfaces, but one or both of the faces may be aspherical.

Preferably, as shown in FIG. 7, in particular, the convex surface 4A on the opposite side of the surface facing the light source is an aspherical surface (solid line) in which the radius of curvature (R1 or R2) of the periphery of the paraxial radius of curvature is larger than The paraxial radius of curvature (R0) of the sphere (dashed line). This is because the surface angle at the peripheral portion of the lens is small, which contributes to an increase in lens transmittance. At this time, as shown in FIG. 7, the radius of curvature increases from the central axis Z of the lens to the periphery (lens end 1a). Here, the paraxial radius of curvature refers to the radius of curvature on the central axis of the lens.

The convex surface facing the opposite side of the surface facing the light source may be aspherical, and the convex or concave surface facing the light source may be aspherical. Thereby, the aberration characteristics are further improved.

For example, an aspherical lens having the following specifications (spec) using a glass material of Example 4 to be described later can be used.

(aspherical data)

Example

Table 1 shows the constituent components (composition) of the glass material used in determining the maximum surface angle dependence of the surface 4 on the emission side of the lens transmittance for the lens shape of Fig. 4 .

Fig. 8 is a view showing the lens of the NA system of 0.6 or more in the present invention. The relationship between the maximum surface angle of the surface on the exit side of the mirror (the surface 4 on the exit side in Fig. 1) and the transmittance of the lens (i.e., the dependence of the maximum surface angle of the surface on the exit side of the transmittance). Further, t/f is 1.3 or less. In the case of NA=0.60, t/f is made 0.30, 0.40, 0.50, 0.60, 0.75, 0.80, 1.00, 1.20, 1.30; in the case of NA=0.65, t/f is made 0.30, 0.40, 0.50, 0.60, 0.75, 0.80, 1.00, 1.20, 1.30; in the case of NA=0.71, t/f is made 0.40, 0.60, 0.71, 0.80, 0.90, 1.00, 1.10, 1.20, 1.28, 1.30.

Specifically, FIG. 8 shows lens transmittances in the case of NA systems of 0.6, 0.65, and 0.71 when the wavelength is 430 nm (blue) for each of the glass materials shown in Table 1 below. Further, although the data of the wavelength system of 530 nm (green) and the wavelength of 650 nm (red) are not described, in general, the internal transmittance of the glass material sharply drops when it is less than or equal to the vicinity of 450 nm of the purple on the short wavelength side. In the present specification, the lens transmittance of the wavelength region (430 nm) in the wavelength region is used as an index of the lens transmittance to study the characteristics of the lens.

Further, in Fig. 8, the area enclosed by the broken line is an embodiment of the invention of the present application.

The lens transmittance of the vertical axis of Fig. 8 was normalized by setting the maximum value to 1. As shown in FIG. 8, the lens transmittance is good when the maximum surface angle is 55 or less, and when it exceeds 65, it is abruptly deteriorated. The data of the wavelength of 530 nm and the wavelength of 650 nm also showed the same tendency as the wavelength of 430 nm of FIG.

In addition, the lens transmittance of the collimating lens having a maximum surface angle of more than 65° is greatly different between the center portion and the peripheral portion, so that the parallel light converted by the collimating lens passes through the center of the collimating lens. A difference in brightness occurs between the light of the portion and the light passing through the peripheral portion of the periphery of the center portion. Self-inhibiting brightness difference, At the same time, from the viewpoint of increasing the lens transmittance, the upper limit of the maximum surface angle is preferably 65° or less, 60° or less, and 55° or less. From the viewpoint of making the NA system 0.6 or more, the lower limit of the maximum surface angle is preferably 20 or more.

Table 1 shows the indices of the maximum surface angle and lens transmittance of each glass material. As is clear from the results of FIG. 8 , the case where the maximum surface angle is 65° or less is represented by ○, and the case where it exceeds 65° is represented by ×.

[Table 1]

The lens transmittance is represented by ◎○× as an index. Here, ◎ is a grade A (0.985 or more), ○ grade B (0.970 or more, and less than 0.985), and a × grade C (less than 0.970). The value in the above () is a value that normalizes the lens transmittance. The glass material which satisfies the requirements of the maximum surface angle and the lens transmittance is shown in the form of an embodiment, and the glass material which is not satisfied is shown in the form of a comparative example.

As is clear from Table 1, in the glass materials shown in Examples 1 to 7, the maximum surface angle was 65° or less, nd=1.59 or more, and the total content of TiO ₂ , WO ₃ , Nb ₂ O ₅ , and Bi ₂ O _{3 was obtained} . The suppression is 40% by weight or less, whereby good lens transmittance characteristics can be obtained.

As is clear from Table 1, the glass material of Comparative Example 1 did not satisfy the requirements of the maximum surface angle. Further, as is clear from Table 1, the glass material of Comparative Example 2 in which the total content of TiO ₂ , WO ₃ , Nb ₂ O ₅ , and Bi ₂ O ₃ in the glass was large was insufficient. The ultraviolet absorption of the above metal ions in the glass is large, which causes the lens transmittance to deteriorate.

The present invention is not limited to the above-described embodiments of the present invention, and various modifications and changes can be made without departing from the spirit and scope of the invention.

Hereinafter, the present invention will be summarized with reference to the drawings. As shown in Fig. 1, the collimator lens 1 of the first embodiment is a collimator lens made of a glass material, and converts light having a wavelength of 380 nm to 700 nm emitted from the light source S into a parallel beam. The collimator lens 1 has a face 4 on which a convex portion is provided on the side opposite to the face 2 facing the light source S. In the collimator lens 1, the numerical aperture NA is 0.6 or more, and t/f is 1.3 or less (t: central lens thickness, f: focal length). Further, the maximum surface angle θ of the surface 4 on which the convex portion is provided is 65 or less. Further, the refractive index nd of the glass material forming the collimator lens 1 is 1.59 or more, and the total content of TiO ₂ , WO ₃ , Nb ₂ O ₅ , and Bi ₂ O ₃ is 0 to 40% by weight.

In the collimator lens 1, the convex portion provided on the surface 4 opposite to the surface facing the light source S may be aspherical.

Further, in the collimator lens 1, the surface facing the light source S may be a flat surface.

Further, in the collimator lens 1, for example, as shown in FIG. 1, a convex portion is provided on a surface facing the light source S.

The convex portion provided on the surface facing the light source may be aspherical.

Further, as shown in the collimator lens 106 of the embodiment shown in Fig. 6, the present invention may be configured such that a concave portion is provided on the surface facing the light source S.

In the collimating lens of the present invention, the light source S can be used as a light source for an illumination optical system.

Further, in the collimator lens of the present invention, the illumination optical system may be an illumination optical system of a projection type image display device.

As shown in FIGS. 2 and 3, in the collimator lens of the present invention, the light source S can be a laser light source.

Further, the present invention may use the illumination optical system of each of the collimating lenses summarized above.

Furthermore, the present invention can be a projection type image display device including such an illumination optical system.

1‧‧‧ collimating lens

2‧‧‧The side of the light source side

4‧‧‧The side of the exit side

S‧‧‧ light source

t‧‧‧Center lens thickness

Claims (7)

A collimating lens is a collimating lens made of a glass material, and the collimating lens converts light having a wavelength of 380 nm to 700 nm emitted from a light source into a parallel beam, wherein the side opposite to the surface facing the light source has The surface of the convex portion is provided, the numerical aperture NA is 0.6 or more, the ratio t/f of the central lens thickness t to the focal length f is 1.3 or less, and the maximum surface angle of the surface on which the convex portion is provided is 65 or less. The refractive index nd is 1.59 or more, and the total content of TiO ₂ , WO ₃ , Nb ₂ O ₅ , and Bi ₂ O ₃ of the above glass material is 0 to 40% by weight. The collimating lens of claim 1, wherein the convex portion provided on a surface opposite to the surface facing the light source is aspherical. The collimating lens of claim 1 or 2, wherein the surface facing the light source is a flat surface. A collimating lens according to claim 1 or 2, wherein the convex surface is provided on the surface facing the light source. The collimating lens of claim 4, wherein the convex portion provided on the surface facing the light source is aspherical. A collimating lens according to claim 1 or 2, wherein the surface facing the light source is provided with a concave portion. The collimating lens of claim 6, wherein the concave portion provided on the surface facing the light source is an aspherical surface.