JP2003084195A - Plastic aspherical collimator lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive plastic aspherical collimator lens the aspherical surface shape which can be easily measured with accuracy of 1/10 of a light source wavelength. SOLUTION: The plastic aspherical collimator lens, is a single lens, the surface on the collimated light outgoing side is molded to a quadric spheroid surface which has a positive refractive power and which is shown by a prescribed expression, and the surface on the light source side is spherical, and the collimator lens is molded of resin by an injection molding method. The cone constant (k) of the spheroid surface, the correction coefficient r1 /nf of a sine condition and the under correction coefficient (n-1)k of the spherical aberration satisfy the following conditions; -1<k<0, 0.20<r1 /nf<0.40 and -0.45<(n-1)k<-0.22. Besides, the lens thickness (d), the cone constant (k) of the spheroid surface and the correction coefficient r1 /nf of the sine condition satisfy the following conditions so as to reduce the sensitivity of aberration due to decentering; 1<=d<=2, -0.9<k<=-0.65 and 0.360<=r1 /nf<=0.399.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a collimator lens used as one of optical components constituting an optical system of an optical pickup, and more particularly to an aspherical collimator lens.

[0002]

As is well known, various optical recording media (optical disks) have been developed and put into use. Examples of such an optical disc include a magneto-optical disc, a mini disc, a compact disc (CD), and a CD-R (CD
Recordable), DVD (Digital Versatile Disk), and the like. Such an optical disc is driven by an optical disc drive. The optical disk drive includes an optical pickup for reading information from the optical disk and / or writing information to the optical disk. The optical pickup uses a semiconductor laser as a light source, and irradiates a laser beam emitted (emitted) from the semiconductor laser onto an optical disc through an optical system. A collimator lens is used as one of the optical components forming this optical system. The collimator lens is for collimating the laser light.

As is well known, a semiconductor laser is composed of an active region (active layer) that amplifies light and a resonator that produces a feedback necessary for oscillation. The laser light (radiation light) emitted from the semiconductor laser has different divergence angles and other properties between the direction of the active layer and the direction perpendicular thereto. Considering the anisotropy and efficiency of the emitted light, the collimator lens is required to have a numerical aperture (NA) of about 0.1 to 0.2 and a diffraction limit. here,
The "numerical aperture" is one of the quantities that represent the brightness and resolution of an optical system, and the sine of an angle α formed by an object point on the optical axis in the medium of refractive index n with respect to the radius of the entrance pupil and the medium. Is the product of the refractive indices n sin α. Further, the “diffraction limit” means that the resolution capability of an optical system for image formation is close to the limit value based on the theoretical value of the diffraction effect. In this case, the resolution is determined only by the wavelength of light and the numerical aperture.

Conventionally, this collimator lens has been composed of a plurality of lenses such as two lenses. Therefore, it was complicated and expensive. Recently, in order to realize cost reduction of this collimator lens, a single lens using an aspherical surface has been developed,
Invented.

Here, the lens includes a "spherical lens" and an "aspherical lens". A "spherical lens" is a lens whose surface shape is spherical, and an "aspherical lens" is a lens whose surface shape is aspherical. In a typical "spherical lens" that is a cut out part of a sphere, an aberration occurs that it cannot focus on one point, so in an "aspherical lens", this aberration does not occur depending on the part of the lens. Changing the curvature. While an aspherical lens is expensive, it eliminates the need for aberration removal that is normally done by combining a plurality of lenses, which helps reduce the size and weight of the lens.

Here, the "aberration" means a geometrical optical deviation from an ideal image in optical image formation by a lens or the like.
Aberrations are roughly classified into five types, and three types of aberrations are spherical aberrations, astigmatisms, and distortions. “Spherical aberration” refers to an aberration in which, when a light ray emitted from one point on the optical axis enters the optical system, the position where the light ray intersects the optical axis varies depending on the distance from the optical axis of the incident point. "Astigmatism" is an aberration in which the off-axis image points due to the ray bundles emerging from the off-axis object point of the optical system do not converge at one point, and the sagittal image point and the meridional image point do not match. Say.
“Distortion aberration” is an aberration that represents a defect in reproducibility of the shape of an image.

Wavefront aberration is also known. "Wavefront aberration" refers to the deviation between the wavefront after passing through the optical system and the reference wavefront centered on the ideal image point. Wavefront aberration is used as a measure of aberration.In practice, the difference between the wavefront after passing through the optical system and the wavefront (reference wavefront) having the center of curvature at the observation point at the exit pupil plane is measured along the ray. , Which is multiplied by the refractive index at that location, that is, the optical path length.

As the material of the aspherical lens, plastic and glass are used. In the case of plastic, it is manufactured by the injection molding method, and in the case of glass, it is manufactured by the press molding method.

[0009]

However, since the conventional aspherical lens has a complicated aspherical shape, it is difficult to measure the aspherical shape with an accuracy of 1/10 or less of the wavelength of light. . This hinders the practical use of a lens having a diffraction limit. Further, when the material of the aspherical lens is glass, there is a drawback that it becomes expensive.

Therefore, an object of the present invention is to provide an inexpensive plastic aspherical collimator lens capable of easily measuring an aspherical shape with an accuracy of 1/10 of a light source wavelength.

Further, such a plastic aspherical collimator lens is manufactured by the injection molding method as described above, but in general, there is a center deviation of the axis of the mold used, that is, eccentricity. Further, there is a case where the light ray has an angle with the horizontal due to the inclination with respect to the light source when the plastic aspherical collimator lens is incorporated in the optical pickup. This angle is called the angle of view. In such a case, it is desired that the sensitivity of wavefront aberration due to decentering is as low as possible.

Therefore, another object of the present invention is to provide a plastic aspherical collimator lens capable of suppressing wavefront aberration even if the eccentricity or the angle of view is present.

Specifically, the eccentricity is 0.03 at maximum.
Another object of the present invention is to provide a plastic aspherical collimator lens capable of suppressing wavefront aberration to 40 [mλRMS] or less when the angle of view is [mm] and the angle of view is 2 [deg] at maximum.

[0014]

According to the present invention, the surface on the parallel light exit side is a spheroid having a positive refractive power, and the spheroid is a vertex contact point of a point on an aspheric surface. The distance from the plane is X, the height from the optical axis is h, and the curvature of the ellipse vertex is C.
₁ and the conic constant k,

[Equation 8] Further, when the radius of curvature 1 / C ₁ of the apex of the ellipsoid is r ₁ , the focal length of the lens is f, and the refractive index of the lens is n, the conical constant k, the correction coefficient r ₁ / nf of the sine condition, and the under The correction coefficient (n-1) k of the spherical aberration of satisfies the conditions of the following formulas 9, 10, and 11, respectively,

[Equation 9]

[Equation 10]

[Equation 11] In addition, a single lens having a spherical surface on the light source side, and a plastic aspherical collimator lens made of resin can be obtained.

In the plastic aspherical collimator lens, when the lens thickness is d [mm], the lens thickness d, the conic constant k, and the correction coefficient r ₁ / nf of the sine condition are Conditions of the following formula 12, formula 13, and formula 14, respectively

[Equation 12]

[Equation 13]

[Equation 14] It is desirable to satisfy.

The resin material is preferably selected from the group consisting of norbornene-based, amorphous polyolefin-based, and acrylic resin materials.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

The plastic aspherical collimator lens according to the first embodiment of the present invention is a single lens whose surface on the parallel light emission side is a spheroidal surface having a positive refractive power and whose surface on the light source side is a spherical surface. Therefore, it is made of resin by injection molding. Here, the “refractive power” refers to the ability of the lens and the eyepiece to collect and diffuse light, and is represented by the reciprocal (1 / f) of the focal length f of the lens. In this embodiment, the resin material is selected from the group consisting of norbornene-based, amorphous polyolefin-based, and acrylic resin materials.

As shown in FIG. 1, the spheroidal surface has a distance X from the tangent plane of the aspherical vertex O of a point on the aspherical surface, a height h from the optical axis, and an elliptical vertex O. Curvature is C1,
And the conic constant is k, X is expressed by the following Expression 15.

[0020]

[Equation 15]

The above equation 15 is a mathematical expression that defines a quadric surface. The spheroidal surface has a conical constant k and a correction coefficient r for the sine condition, where r ₁ is the radius of curvature 1 / C ₁ of the ellipsoidal vertex O, f is the focal length of the lens, and n is the refractive index of the lens.
₁ / nf and under spherical aberration correction coefficient (n-
1) k satisfies the following expressions 16, 17, and 18, respectively.

[0022]

[Equation 16]

[Equation 17]

[Equation 18]

Here, the above equation 16 is a condition for the quadric surface to be a quadric ellipsoid. When k <−1, the quadric surface becomes a quadratic hyperboloid.

FIG. 2 shows the relationship between the correction coefficient r ₁ / nf for the sine condition and the correction coefficient (n-1) k for the under spherical aberration. In FIG. 2, the horizontal axis represents the correction coefficient r ₁ / n of the sine condition.
f is the vertical axis and the correction coefficient (n-1) of the spherical aberration is under.
is taking k. Here, the "sine condition" means that when the image of the object point P on the axis of the optical system occurs at one point P'on the axis without aberration, the point P is close to the point P on the plane including the point P and perpendicular to the axis. Point Q
Is a condition for forming an image as a single point at a point Q ′ that is close to a point P ′ on a plane that includes the point P ′ and is perpendicular to the axis. It can be seen from FIG. 2 that when the correction coefficient r ₁ / nf of the sine condition satisfies the above expression 17, the correction coefficient (n−1) k of the under spherical aberration also satisfies the above expression 18. .

The optical characteristics of the collimator lens of the first embodiment are such that spherical aberration is | 0.0012 | mm.
Hereinafter, the lens satisfies astigmatism of | 0.0013 | mm or less and distortion of | 0.0015 |% or less. In order to satisfy this optical characteristic, it is necessary to satisfy the conditions of the above formulas 17 and 18.

FIG. 3 shows the relationship between the correction coefficient r ₁ / nf of the sine condition and each aberration. In FIG. 3, the horizontal axis represents the correction coefficient r ₁ / nf of the sine condition, and the vertical axis represents the value of each aberration. Here, the unit of each aberration on the vertical axis is spherical aberration [mm], astigmatism [mm], and distortion [%].
From FIG. 3, the correction coefficient r ₁ / nf of the sine condition is calculated as
It can be seen that when the value of 7 is satisfied, the spherical aberration, the astigmatism, and the distortion are within the ranges described above.

As will be described later in detail with reference to a comparative example, an aspherical collimator lens that does not satisfy the above conditions has the following disadvantages. For example, r ₁ / nf ≦
At 0.18, distortion and spherical aberration increase. When r ₁ /nf≧0.42, the surface is not an ellipsoid but a hyperboloid (k <−1). If both surfaces of the lens are made to be second-order aspherical surfaces, spherical aberration will be extremely large at 0.01 mm. If both surfaces of the lens are made to have a fourth-order aspherical surface, the distortion aberration exceeds 0.0015%. Furthermore, if both surfaces of the lens are made a 10th-order aspherical surface, the distortion will be 0.0015%.
Surpass.

The plastic aspherical collimator lens according to the first embodiment, which satisfies the above-mentioned conditions, is
The aspherical shape can be easily measured with an accuracy of 1/10 of the light source wavelength. The reason is that, as an aspherical shape,
This is because the aspherical surface is not complicated because a low-order quadric surface that is a quadratic elliptic surface is used instead of a high-order aspherical surface of 4th order or higher. The aspherical surface shape can be measured by using a stylus type aspherical surface measuring device which is well known in this technical field. The plastic aspherical collimator lens according to the present embodiment has a numerical aperture NA of 0.12.
Since the spherical aberration and the sine condition are well corrected at about 0.2, the lens is a substantially aspherical single lens having diffraction-limited performance.

Further, since it is made of plastic, the aspherical collimator lens according to the present embodiment can be inexpensively supplied.

In the plastic aspherical collimator lens according to the second embodiment of the present invention, the spheroidal surface is added to the restriction in the first embodiment described above.
When the lens thickness is d [mm], the lens thickness d, the conic constant k, and the correction coefficient r ₁ / n of the sine condition
f is the following formula 19, formula 20, and formula 21, respectively.
The conditions of are met.

[0031]

[Formula 19]

[Equation 20]

[Equation 21]

As shown in FIG. 4, the plastic aspherical collimator lens CL according to the second embodiment has a center shift of the optical axis OA in the mold used when the plastic aspherical collimator lens CL is manufactured by the injection molding method. The maximum eccentricity is 0.
It is assumed that the angle of view is 03 mm, and the angle of view of the light ray with respect to the horizontal is 2 ° at the maximum when the collimator lens CL is incorporated in the optical pickup.

In Table 1 below and FIG. 5, the lens thickness d is 1
2 shows the wavefront aberration [mλRMS] when the angle of view is 2 ° with respect to the correction coefficient r ₁ / nf of the sine condition when the eccentricity is 0 mm and 0.03 mm at 2 mm.

[0034]

[Table 1]

In FIG. 5, the horizontal axis represents the correction coefficient r ₁ / nf of the sine condition, and the vertical axis represents the wavefront aberration [mλRMS]. From Table 1 and FIG. 5, the wavefront aberration is 40 mλRMS.
In order to suppress below, correction coefficient r ₁ / nf of sine condition
However, it can be seen that it is necessary to satisfy the above expression 21. The lens thickness d is set to the range shown by the above mathematical expression 19 because the lens thickness is usually in this range. Further, the conical constant k is limited to the range of the formula 20 as described below with reference to the examples, when the correction coefficient r ₁ / nf of the sine condition satisfies the formula 21, This is because the constant k is within the range of the above equation 20.

Therefore, it can be seen that the plastic aspherical collimator lens according to the second embodiment, which satisfies the above-mentioned conditions, has low sensitivity of aberration due to decentering.

[0037]

EXAMPLES Next, the plastic aspherical collimator lens according to the present invention will be described with reference to Examples and Comparative Examples.

In the following, Examples 1 to 6 are given as examples of the plastic aspherical collimator lens according to the first embodiment of the present invention, and Comparative Examples 1 to 1 are given as comparative examples.
Comparative Example 4 is shown. Here, each of the examples and the comparative examples is a simulation result under the conditions described below.
The wavelength used was 780 [nm]. Numerical aperture NA
Was performed at 0.14. The refractive index of the cover glass in this wavelength range was 1.505. Here, as the cover glass, for example, glass of a laser diode is assumed. The image height was set to 0.0 [mm] and 0.1 [mm].

The simulation results of Examples 1 to 6 under these conditions are shown in Table 2 below.

[0040]

[Table 2]

In Table 2 above, r ₁ is the radius of curvature of the surface on the parallel light emitting side, r ₂ is the radius of curvature of the surface on the light source incident side, n is the refractive index of the plastic lens, and d is the plastic lens. The thickness of the lens, d _c is the thickness of the cover glass, f is the focal length, k is the conical coefficient of the surface on the parallel light emission side, r ₁ / nf is the correction coefficient of the sine condition, (n-1) k
Indicates the correction coefficient of the spherical aberration of under.

From Table 2 above, in any of Examples 1 to 6, the conical constant k, the correction coefficient r ₁ / nf of the sine condition, and the correction coefficient (n-1) k of the under spherical aberration are respectively It can be seen that the above-described conditions of Expression 16, Expression 17, and Expression 18 are satisfied.

6 to 11 show a spherical aberration diagram, an astigmatism diagram, and a distortion diagram of Examples 1 to 6, respectively. 6 to 11, (A) is a spherical aberration diagram, (B) is an astigmatism diagram, and (C) is a distortion diagram.

In the spherical aberration diagram of (A), the vertical axis is the entrance height h and is normalized to 1, and the horizontal axis is spherical aberration [mm].
Is. As is clear from FIGS. 6 to 11A,
In each of Examples 1 to 6, the spherical aberration is | 0.001.
It can be seen that it is in the range of 2 | mm or less.

In the astigmatism diagram of (B), the vertical axis represents the image height.
IM GHT [mm], and the horizontal axis represents the distance [mm] in the optical axis direction from the ideal image plane. The solid curve indicated by S indicates the sagittal image surface (aspherical image surface), and the dotted curve indicated by T indicates the meridional image surface (meridian image surface). As is clear from FIGS. 6 to 11B, it is found that the astigmatism | T−S | is in the range of | 0.0013 | mm or less in all of Examples 1 to 6.

In the spherical aberration diagram of (C), the vertical axis represents the image height.
IM GHT [mm], and the horizontal axis represents distortion [%]. As is clear from (C) of FIGS. 6 to 11, in each of Examples 1 to 6, the distortion aberration is | 0.0015 |
It can be seen that it is in the range of% or less.

As described above, in the plastic aspherical collimator lenses of Examples 1 to 6 described above, the above-mentioned three types of aberrations are satisfactorily corrected. Further, since the lens is composed of the ellipsoidal surface and the spherical surface, it is possible to easily and accurately measure the accuracy of each surface with an interferometer or the like at a wavelength of about 1/10 of the used wavelength. .

Next, a comparative example according to the first embodiment will be described. 12 to 15 show a spherical aberration diagram, an astigmatism diagram, and a distortion diagram of Comparative Examples 1 to 4, respectively. In each of FIGS. 12 to 15,
(A) is a spherical aberration diagram, (B) is an astigmatism diagram, (C)
Represents a distortion diagram. In the spherical aberration diagram of (A), the vertical axis is the entrance height h and is normalized to 1, and the horizontal axis is the spherical aberration [mm]. In the astigmatism diagram of (B), the vertical axis represents the image height IM GHT [mm], and the horizontal axis represents the distance [mm] in the optical axis direction from the ideal image plane. The solid curve indicated by S indicates the sagittal image surface (aspherical image surface), and the dotted curve indicated by T indicates the meridional image surface (meridian image surface).
In the spherical aberration diagram of (C), the vertical axis represents the image height IM GHT [m
m], and the horizontal axis represents distortion [%].

Comparative Example 1 shown in FIG. 12 is an example in which the correction coefficient r1 / nf of the sine condition is equal to 0.18. As is clear from FIG. 12C, the distortion is | 0.00
It can be seen that it is larger than 15%.

Comparative Example 2 shown in FIG. 13 is an example in which both surfaces of the lens are quadratic aspherical surfaces. As is clear from FIG. 13A, it can be seen that the spherical aberration is extremely large at 0.01 mm.

Comparative Example 3 shown in FIG. 14 is an example in which both surfaces of the lens are quaternary aspherical surfaces. As is clear from FIG. 14C, it can be seen that the distortion aberration exceeds | 0.0015 |%.

Comparative Example 4 shown in FIG. 15 is an example in which both surfaces of the lens are aspherical surfaces of tenth order. As is clear from FIG. 15C, it can be seen that the distortion aberration exceeds | 0.0015 |%.

Next, Examples 7 to 14 will be shown as examples of the plastic aspherical collimator lens according to the second embodiment of the present invention. Here, each of the examples is a simulation result under the conditions described below. The wavelength used was 656 [nm]. The numerical aperture NA is 0.
Conducted in 14. The refractive index of the cover glass CG in this wavelength range was 1.506. Here, as the cover glass CG, for example, glass of a laser diode is assumed. The angle of view was set to 2 [°].

The simulation results of Examples 7 to 14 under these conditions are shown in Table 3 below.

[0055]

[Table 3]

In Table 3, r ₁ is the radius of curvature of the surface on the parallel light emitting side, r ₂ is the radius of curvature of the surface on the light source incident side, n is the refractive index of the plastic lens, and d is the plastic lens. The thickness of the lens, d _c is the thickness of the cover glass CG, f is the focal length, k is the conical coefficient of the surface on the parallel light emission side, and r ₁ / nf is the correction coefficient of the sine condition.

From Table 3 above, in any of Examples 7 to 14, the lens thickness d, the conic constant k, and the correction coefficient r ₁ / nf of the sine condition are respectively the above-mentioned Formula 19 and Formula 2
It can be seen that the conditions of 0 and Formula 21 are satisfied.

Embodiment 7 is shown in each of FIGS. 16 to 19.
11A to 11C show the spherical aberration diagram, the astigmatism diagram, and the distortion diagram of Example 10. In each of FIGS. 16 to 19,
(A) is a spherical aberration diagram, (B) is an astigmatism diagram, (C)
Represents a distortion diagram.

In the spherical aberration diagram of (A), the vertical axis is the entrance height h and is normalized to 1, and the horizontal axis is spherical aberration [mm].
Is. As is clear from (A) of FIG. 16 to FIG. 19, in any of Examples 7 to 10, the spherical aberration was | 0.
It can be seen that it is in the range of 01 | mm or less.

In the astigmatism diagram of (B), the vertical axis represents the angle [deg], and the horizontal axis represents the distance [m] from the ideal image plane in the optical axis direction.
m] is shown. The solid curve indicated by S indicates the sagittal image surface (aspherical image surface), and the dotted curve indicated by T indicates the meridional image surface (meridian image surface). As is clear from FIGS. 16 to 19B, it is understood that astigmatism | T-S | is in the range of | 0.01 | mm or less in all of Examples 7 to 10.

In the distortion diagram of (C), the vertical axis represents the angle [deg] and the horizontal axis represents the distortion [%]. Figure 1
6 to FIG. 19 (C), Example 7 to
It can be seen that in all of Example 10, the distortion aberration is in the range of | 0.01 |% or less.

As described above, in the plastic aspherical collimator lenses of Examples 7 to 10 described above, the above-mentioned three types of aberrations are satisfactorily corrected. Further, since the lens is composed of the ellipsoidal surface and the spherical surface, it is possible to easily and accurately measure the accuracy of each surface with an interferometer or the like at a wavelength of about 1/10 of the used wavelength. .

Although the present invention has been described above with reference to examples, it goes without saying that the present invention is not limited to the above-described embodiments.

[0064]

As is apparent from the above description, in the present invention, the surface on the parallel light exit side is a spheroid of quadratic and the surface on the light source side is a spherical surface. It is possible to easily measure the aspherical shape with high accuracy. Further, since the above-mentioned quadratic spheroid is manufactured so that the conic constant, the correction coefficient for the sine condition, and the correction coefficient for the under spherical aberration satisfy the predetermined conditions, the spherical aberration and the sine condition are well corrected. It is possible to provide a substantially aspherical single lens having diffraction-limited performance. Furthermore, since plastic (resin) is used as the material, an inexpensive aspherical collimator lens can be supplied. Further, in addition to the above conditions, the spheroidal surface of the second order is manufactured so that the lens thickness, the conical constant, and the correction coefficient of the sine condition satisfy predetermined conditions. It is possible to provide an aspherical single lens having low

[Brief description of drawings]

FIG. 1 is a diagram for explaining a spheroidal surface of a plastic aspherical collimator lens according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a correction coefficient for a sine condition and a correction coefficient for under spherical aberration in the plastic aspherical collimator lens according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between a correction coefficient of a sine condition and each aberration in the plastic aspherical collimator lens according to the first embodiment of the present invention.

FIG. 4 is a diagram for explaining decentering and an angle of view in a plastic aspherical collimator lens according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a relationship between a sine condition correction coefficient and a wavefront aberration in the plastic aspherical collimator lens according to the second embodiment of the present invention.

FIG. 6 is a spherical aberration diagram (A), an astigmatism diagram (B), and a distortion diagram (C) in Example 1 of the plastic aspherical collimator lens of the present invention.

FIG. 7 is a spherical aberration diagram (A), an astigmatism diagram (B), and a distortion diagram (C) in Example 2 of the plastic aspherical collimator lens of the present invention.

FIG. 8 is a spherical aberration diagram (A), an astigmatism diagram (B), and a distortion diagram (C) in Example 3 of the plastic aspherical collimator lens of the present invention.

FIG. 9 is a spherical aberration diagram (A), an astigmatism diagram (B), and a distortion diagram (C) in Example 4 of the plastic aspherical collimator lens of the present invention.

FIG. 10 is a spherical aberration diagram (A), an astigmatism diagram (B), and a distortion diagram (C) in Example 5 of the plastic aspherical collimator lens of the present invention.

FIG. 11 is a spherical aberration diagram (A), an astigmatism diagram (B), and a distortion diagram (C) in Example 6 of the plastic aspherical collimator lens of the present invention.

FIG. 12 is a spherical aberration diagram (A), an astigmatism diagram (B), and a distortion diagram (C) in Comparative Example 1 of a plastic aspherical collimator lens.

FIG. 13 is a spherical aberration diagram (A), an astigmatism diagram (B), and a distortion diagram (C) in Comparative Example 2 of a plastic aspherical collimator lens.

FIG. 14 is a spherical aberration diagram (A), an astigmatism diagram (B), and a distortion diagram (C) in Comparative Example 3 of a plastic aspherical collimator lens.

FIG. 15 is a spherical aberration diagram (A), an astigmatism diagram (B), and a distortion diagram (C) in Example 4 of the plastic aspherical collimator lens.

FIG. 16 is a spherical aberration diagram (A), an astigmatism diagram (B), and a distortion diagram (C) in Example 7 of the plastic aspherical collimator lens of the present invention.

FIG. 17 is a spherical aberration diagram (A), an astigmatism diagram (B), and a distortion diagram (C) in Example 8 of the plastic aspherical collimator lens of the present invention.

FIG. 18 is a spherical aberration diagram (A), an astigmatism diagram (B), and a distortion diagram (C) in Example 9 of the plastic aspherical collimator lens of the present invention.

FIG. 19 is a spherical aberration diagram (A), an astigmatism diagram (B), and a distortion diagram (C) in Example 10 of the plastic aspherical collimator lens of the present invention.

[Explanation of symbols]

h Height from optical axis X Distance of the point on the aspherical surface from the tangent plane of the aspherical vertex O aspherical vertex CL collimator lens CG cover glass OS light source f Focal length

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yuuki Sato             1601 Sakai, Atsugi, Kanagawa Mitsumi Electric Co., Ltd.             Company Atsugi Office F term (reference) 2H087 KA13 LA01 LA25 PA01 PA17                       PB01 QA02 QA06 QA07 QA12                       QA14 QA32 QA34 RA04 RA12                       RA42

Claims (3)

[Claims] 1. A surface on the exit side of parallel light is a spheroid having a positive refractive power, and the spheroid has a distance X from an aspherical surface tangent plane of a point on the aspherical surface and an optical axis. The height of
Assuming that the curvature of the apex of the ellipsoid is C ₁ and the conic constant is k, it can be expressed by the following equation ₁ , Further, when the radius of curvature 1 / C ₁ of the apex of the ellipsoid is r ₁ , the focal length of the lens is f, and the refractive index of the lens is n, the conical constant k, the correction coefficient r ₁ / nf of the sine condition, and the under The correction coefficient (n-1) k of the spherical aberration of satisfies the conditions of the following formulas 2, 3, and 4, respectively, and [Equation 3] [Equation 4] Further, a plastic aspherical collimator lens which is a single lens having a spherical surface on the light source side and made of resin. 2. When the thickness of the lens is d [mm], the lens thickness d, the conical constant k, and the correction coefficient r ₁ / nf of the sine condition are respectively expressed by the following formula 5,
Conditions of Formulas 6 and 7 [Formula 5] [Equation 6] [Equation 7] The plastic aspherical collimator lens according to claim 1, wherein 3. The non-plastic material according to claim 1, wherein the resin material is selected from the group consisting of norbornene-based, amorphous polyolefin-based, and acrylic resin materials. Spherical collimator lens.