JP2006234989A - Lens unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain the cost reduction of a lens unit, to improve the assemblability of the lens unit, and to prevent the erroneous assembling. <P>SOLUTION: The lens unit includes a 1st lens 1, an aperture diaphragm plate 4 of a prescribed diameter and a 2nd lens 2 which are successively arranged from an object side to an image field side, and also, a spacer 300 arranged between the 1st lens 1 and the 2nd lens 2, and the spacer 300 is constituted by joining a plurality of spacers 300a to 300d having the same shape, and the aperture diaphragm plate 4 is sandwiched between either two of the plurality of spacers. By having such the constitution that the plurality of spacers having the same shape are used, the manufacturing cost is reduced, and it can be assembled in both directions, then, the erroneous assembling is prevented, and also, since the installation position of the aperture diaphragm plate 4 is allowed to be located between either two of the plurality of spacers, the degree of freedom in design can be enhanced, and the aperture diaphragm plate can be arranged in a position corresponding to the optical design specification. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lens unit that is applied as an imaging lens optical system of a solid-state imaging device such as a CCD or CMOS, and more particularly to a lens unit that includes a plurality of lenses arranged in the optical axis direction.

In general, in a lens unit including a plurality of imaging lenses, a spacer is disposed between the lenses to position the lenses in the optical axis direction. As such a spacer, it is desirable that the reflection on the surface is small and the dimensions are accurate.
As a lens unit having a spacer that copes with the above problem, a lens unit in which a lens and a spacer are integrally formed to reduce the number of parts and cost is known (for example, see Patent Document 1).
However, when the lens and the spacer are integrally molded, the shape becomes complicated, so that the molding die is naturally complicated and the cost increases.

Another lens unit is known in which a flare stopper plate is fixed to a spacer to prevent the occurrence of flare due to internal reflection (see, for example, Patent Document 2).
However, this method of fixing the flare stopper plate to the stopper by retrofitting requires a punching operation in which the flare stopper plate is previously punched from a sheet metal or the like, and a fixing operation in which the flare stopper plate is fixed to the spacer. Incurs an increase.

Further, as another lens unit, there is known a lens unit that uses a piano wire or a spring wire as a spacer so as to ensure a minute lens interval (see, for example, Patent Document 3).
However, when a piano wire or a spring wire is used as the spacer, even if a minute lens interval can be secured, the assembly is not easy, and it is difficult to ensure the lens interval with high accuracy.

JP 2002-90621 A JP 2004-184687 A Japanese Patent Application Laid-Open No. 2004-233795

  The present invention has been made in view of the above-described problems of the prior art, simplifying the shape and structure of parts, reducing costs, and facilitating assembly work while ensuring the accuracy of assembly between lenses. It is another object of the present invention to provide a lens unit capable of reducing the reflected light at the stop end face (edge of the stop opening).

The lens unit of the present invention includes a first lens, an aperture stop plate having a predetermined aperture, a second lens, a first lens, and a second lens, which are sequentially arranged from the object side to the image plane side. A plurality of spacers having the same shape, and the aperture stop plate is one of the plurality of spacers. It is characterized by being sandwiched between two spacers.
According to this configuration, since the spacer that regulates the distance between the first lens and the second lens is composed of a plurality of spacers having the same shape, the distance between the lenses can be managed with high accuracy, and when the aperture stop plate is assembled. It can be easily assembled by simply sandwiching between adjacent spacers. In this way, since a plurality of spacers having the same shape are adopted, the manufacturing cost is reduced, and the assembly direction can be either forward or reverse, so that erroneous assembly can be prevented, and the aperture diaphragm plate can be arranged in a plurality of locations. Since it suffices to be between any two of the spacers, the degree of freedom of setting increases accordingly, and the aperture stop plate can be arranged at a position according to the specifications of the optical design.

In the above configuration, the plurality of spacers may include two cylindrical spacers, and the aperture stop plate may be sandwiched between the two spacers.
According to this configuration, the lens interval between the first lens and the second lens can be regulated and the position of the aperture diaphragm plate is regulated only by sandwiching the aperture diaphragm plate between two spacers having the same shape. be able to. When assembling, for example, in a state where the second lens is assembled in an upright lens barrel, one spacer is dropped from the front side in the optical axis direction, and then the aperture stop plate is dropped, By simply dropping the other spacer and finally dropping the first lens, the entire assembling operation is easily completed.

In the above configuration, each of the two spacers has a cylindrical reduced-diameter portion that is reduced in diameter so as to concentrically define a step, and each reduced-diameter portion of each of the two spacers opens in cooperation with each other. It is possible to adopt a configuration in which the diaphragm plates are arranged to face each other so as to sandwich the diaphragm plate.
According to this configuration, since the two spacers have the same shape, it is possible to achieve cost reduction and reduce irregular reflection on the inner peripheral surface of the cylindrical spacer by providing a reduced diameter portion that defines a step. It is possible to prevent flare from occurring.

In the above configuration, the first lens is a negative lens including an aspheric surface having a negative refractive power with a concave surface facing the object side, and the second lens is a non-lens having a positive refractive power with a convex surface facing the object side. A configuration that is a positive lens including a spherical surface can be employed.
According to this configuration, since the first lens includes a negative lens including an aspheric surface having negative refractive power, and the second lens includes a positive lens including an aspheric surface having positive refractive power, spherical aberration and astigmatism are achieved. Various aberrations such as aberration and distortion are corrected well, and a lens unit having good optical characteristics as an imaging lens can be obtained.

In the above configuration, when the refractive index of the first lens is N1 and the Abbe number is ν1, the refractive index of the second lens is N2 and the Abbe number is ν2, the following conditional expressions (1) and (2)
(1) N1 = N2
(2) ν1 = ν2
A configuration that satisfies the above can be adopted.
According to this configuration, since the first lens and the second lens can be formed of the same material, the overall cost can be further reduced.

  According to the lens unit having the above configuration, it is possible to achieve the simplification of the shape and structure of the parts, the cost reduction, the ease of the assembling work, etc. while ensuring the assembling accuracy of the lenses. It is possible to obtain a lens unit that can reduce irregularly reflected light on the surface.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the invention will be described with reference to the accompanying drawings.
FIG. 1 is a sectional view showing an embodiment of a lens unit according to the present invention. As shown in FIG. 1, the lens unit includes a first lens 1 and a second lens 2, a first lens 1 and a second lens 2 that are sequentially arranged from the object side to the image plane side in the optical axis direction L. A plurality of (here, two) spacers 3 (3a, 3b), an aperture diaphragm plate 4 sandwiched between the two spacers 3 (3a, 3b), and an outer contour surrounding them And a lens holder 6 that is screwed onto the front surface of the lens barrel 5 and presses the first lens 1.

  As shown in FIG. 1, the lens barrel 5 is formed in a substantially cylindrical shape by a metal material or a resin material, and includes a seat portion 5a having an opening 5a ′, cylindrical walls 5b and 5c, a male screw portion 5d, and the like. . The seat portion 5a receives the second lens 2 and regulates (positions) the rear end position of the optical axis direction L. The cylindrical wall 5b regulates (positions) the second lens 2, the spacer 3 (3a, 3b), and the aperture stop plate 4 so as to be arranged coaxially in the optical axis direction L. The cylindrical wall 5c is formed with a slightly larger diameter than the cylindrical wall 5b, and restricts (positions) the first lens 1 so as to be arranged coaxially in the optical axis direction L. The depth of the cylindrical wall 5b in the optical axis direction L is set to be shallower (shorter) than the thickness in which the second lens 2, the aperture stop 4 and the plurality of spacers 3 are stacked.

The first lens 1 is formed of a glass material or a resin material, and includes an edge portion that defines a flat rear end surface 1a in the rear in the optical axis direction L and a flat front end surface 1b in the front as shown in FIG. Yes. The rear end surface 1 a is in contact with the front end surface of the spacer 3 a, and the front end surface 1 b is in contact with the press surface 6 b of the lens presser 6.
The second lens 2 is formed of a glass material or a resin material, and includes an edge portion that defines a flat rear end surface 2a at the rear in the optical axis direction L and a flat front end surface 2b at the front, as shown in FIG. Yes.

  The two spacers 3, that is, the spacer 3a and the spacer 3b, have the same cylindrical shape formed by using the same mold from a resin material. The two spacers 3a and 3b define the lens interval (interval in the optical axis direction L) between the first lens 1 and the second lens 2 to a predetermined value with the aperture stop plate 4 sandwiched between them. Thus, the length (thickness) in the optical axis direction L is set in advance.

  The aperture stop plate 4 is formed by punching a thin plate-like sheet metal having a thickness of about 0.05 mm, and has an opening 4a having a predetermined diameter at the center as shown in FIG. In this way, by forming the aperture stop plate 4 independently, the thickness of the edge (the stop end surface) of the opening 4a can be reduced compared to the case where the aperture stop plate 4 is integrally formed with the spacer. It is reduced and the occurrence of flare can be suppressed.

  The lens retainer 6 is formed in a cap shape from a metal material or a resin material, and as shown in FIG. 1, an opening 6 a having a predetermined diameter in front of the object side of the first lens 1 and a front end surface 1 b of the first lens 1. A pressing surface 6b that comes into contact with and presses, a female screw portion 6c that engages with the male screw portion 5d of the lens barrel 5, and the like.

The assembly of the lens unit having the above configuration will be described. First, in a state where the lens barrel 5 is upright, the second lens 2 is fitted into the cylindrical wall 5b, and the rear end surface 2a is brought into contact with the seat portion 5a and positioned. .
Subsequently, one of the two spacers 3 is fitted into the cylindrical wall 5 b and brought into contact with the front end surface 2 b of the second lens 2. Subsequently, the aperture stop plate 4 is fitted into the cylindrical wall 5b and brought into contact with the spacer 3b. From there, the other spacer 3a is fitted into the cylindrical wall 5b, and the aperture diaphragm plate 4 is sandwiched in cooperation with the spacer 3b.
Subsequently, the first lens 1 is fitted into the cylindrical wall 5c, and the rear end face 1a is brought into contact with the front end face of the spacer 3a. Thereafter, the lens retainer 6 is screwed into the lens barrel 5, and the front end surface 1b of the first lens 1 is depressed by the retainer surface 6b.

  As described above, when the second lens 2 is assembled in the upright lens barrel 5 from the front side in the optical axis direction L, one spacer 3b, the aperture stop plate 4, the other spacer 3a, By simply fitting the first lens 1 sequentially and attaching the lens retainer 6 at the end, the entire assembling operation is easily completed.

According to the configuration of the lens unit, the spacer 3 that regulates the distance between the first lens 1 and the second lens 2 is composed of the two spacers 3a and 3b having the same shape, and therefore, between the two spacers 3a and 3b. The lens interval between the first lens 1 and the second lens 2 and the position of the aperture stop plate 4 can be regulated simply by sandwiching the aperture stop plate 4, and the lens interval and the position of the aperture stop can be managed with high accuracy. can do.
Further, when the aperture stop plate 4 is assembled, it can be easily assembled only by being sandwiched between the spacers 3a and 3b. Furthermore, since two spacers 3a and 3b having the same shape are employed, different shapes are used. The manufacturing cost is reduced as compared with the case of using the one having the following structure, and the assembly direction can be either forward or reverse in the optical axis direction L, so that erroneous assembly can be prevented.
Furthermore, the cost of the mold can be reduced as compared with the case where the aperture stop is integrally formed with the spacer, and when changing the aperture stop specification, only the aperture stop plate 4 is changed. Since it is good, the lens unit according to various optical specifications can be provided.

FIG. 2 shows another embodiment of the lens unit according to the present invention, and is the same as the above-described embodiment except that the spacer is changed. Description is omitted.
In the lens unit according to this embodiment, the two spacers 30 (30a, 30b) form the same stepped cylindrical shape formed of the resin material using the same mold. That is, the two spacers 30a and 30b are integrally provided with cylindrical reduced-diameter portions 30a ′ and 30b ′ that are reduced in diameter so as to demarcate the steps on the same axis.
Then, the reduced diameter portion 30a ′ of one spacer 30a and the reduced diameter portion 30b ′ of the other spacer 30b are back-to-back so as to cooperate with each other and sandwich the aperture diaphragm plate 4 as shown in FIG. Opposed to each other.
According to this, since the two spacers have the same shape, the cost can be reduced in the same manner as described above, and irregular reflection on the inner peripheral surface of the spacer 30 can be achieved by the reduced diameter portion 30a ′ of the spacer 30a disposed on the front side. It can be reduced and the occurrence of flare can be prevented.

3 and 4 (a) and 4 (b) show still another embodiment of the lens unit according to the present invention, which is the same as the above-described embodiment except that the number of spacers is changed. About the same structure, the same code | symbol is attached | subjected and the description is abbreviate | omitted.
In the lens unit according to this embodiment, the spacer 300 includes four spacers 300a, 300b, 300c, and 300d. These four spacers 300a, 300b, 300c, and 300d have the same cylindrical shape that is formed of a resin material using the same mold.

According to this configuration, the spacer 300 that regulates the distance between the first lens 1 and the second lens 2 is composed of the four spacers 300a to 300d having the same shape. Therefore, when the aperture stop plate 4 is assembled, they are adjacent to each other. If it is between the spacers, as shown in FIG. 3, it is between the second spacer 300b and the third spacer 300c from the front, and as shown in FIG. 4A, the third spacer 300c and the fourth spacer from the front. As shown in FIG. 4 (b), or as shown in FIG. 4 (b), it can be easily assembled only by being sandwiched between the first spacer 300a and the second spacer 300b from the front. Can do.
As described above, since a plurality of (four) spacers 300 having the same shape are employed, the manufacturing cost can be reduced, erroneous assembly can be prevented, and the aperture diaphragm plate 4 can be disposed at any one of the plurality of spacers 300. Since it suffices to be between the two spacers, the degree of freedom in setting the aperture stop plate 4 increases accordingly, and the aperture stop plate 4 can be arranged at a position according to the specifications of the optical design.

In the lens unit configured as described above, as shown in FIG. 5, the first lens 1 is a negative lens (biconcave lens) having a negative refractive power with the concave surface S1 facing the object side and the concave surface S2 facing the image surface side. As the second lens 2, a positive lens (biconvex lens) having a positive refractive power with the convex surface S4 facing the object side and the convex surface S5 facing the image surface side can be employed.
Here, the surfaces S1, S2, S4, and S5 of the first lens 1 and the second lens 2 are preferably formed as aspherical surfaces. An expression representing the aspheric surface is defined by the following expression.
Z = Cy ² / [1+ (1- (κ + 1) C ² y ² ) ^1/2 ] + Dy ⁴ + Ey ⁶ + Fy ⁸ + Gy ¹⁰
Where Z is the distance from the tangential plane at the apex of the aspheric surface to a point on the aspheric surface whose height from the optical axis L is y, y is the height from the optical axis, and C is the curvature at the apex of the aspheric surface. (1 / R), κ: conic constant, D, E, F, G: 4th, 6th, 8th, and 10th order aspherical coefficients of height y, respectively.
According to this lens configuration, various aberrations such as spherical aberration, astigmatism and distortion are corrected well, and a lens unit having good optical characteristics as an imaging lens can be obtained.

When the refractive index of the first lens 1 is N1 and the Abbe number is ν1, the refractive index of the second lens 2 is N2 and the Abbe number is ν2, the following conditional expressions (1) and (2)
(1) N1 = N2
(2) ν1 = ν2
You may employ | adopt the structure which satisfies these.
According to this, since the 1st lens 1 and the 2nd lens 2 can be formed with the same material, the whole cost can further be reduced.

Next, specific numerical values of the first lens 1 and the second lens 2 will be described below.
In this embodiment, the first lens 1 and the second lens 2 have all surfaces S1, S2, S4, S5 formed of aspherical surfaces and are made of the same material.
As shown in FIG. 5, in the configuration in which the object OB, the first lens 1, the aperture stop plate 4, the second lens 2, and the image plane P are arranged, each surface is Si (i = 1 to 5), The radius of curvature of each surface Si is Ri (i = 1 to 5), the refractive index for d-line is Ni and the Abbe number is νi (i = 1, 2), the object OB to the first lens 1 to the aperture stop plate 4 to An interval (thickness, air interval) on each optical axis L to the second lens 2 is represented by Di (i = 0 to 4), and an interval from the second lens 2 to the image plane P is represented by BF.

  Table 1 shows main specification specifications in the embodiment, Table 2 shows various numerical data (setting values), and Table 3 shows numerical data relating to the aspherical surface. In addition, the aberration diagrams regarding spherical aberration, astigmatism, and distortion are as shown in FIG. In FIG. 6, S represents the aberration on the sagittal plane, and M represents the aberration on the meridional plane.

  According to the lens specifications according to this embodiment, an imaging lens with high optical performance in which spherical aberration, astigmatism, and distortion are well corrected can be obtained.

  As described above, the lens unit of the present invention can achieve low cost, easy assembling work, etc., while ensuring the accuracy of assembling the lenses, and can reduce irregular reflection light in the spacer. Therefore, it is useful not only for a lens unit of an imaging lens optical system including a solid-state imaging device but also for other lens optical systems.

It is sectional drawing which shows one Embodiment of the lens unit which concerns on this invention. It is sectional drawing which shows other embodiment of the lens unit which concerns on this invention. It is sectional drawing which shows other embodiment of the lens unit which concerns on this invention. (A), (b) shows the modification of the assembly | attachment of the lens unit shown in FIG. It is a block diagram which shows arrangement | positioning of the lens system of the lens unit which concerns on this invention. FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, and distortion in a specific numerical example.

Explanation of symbols

1 First lens (negative lens)
1a Rear end face 1b Front end face 2 Second lens (positive lens)
2a Rear end face 2b Front end face 3 (3a, 3b) Multiple spacers 4 Aperture diaphragm plate 5 Lens barrel 5a Seat 5b, 5c Cylindrical wall 5d Male thread 6 Lens presser 6b Presser face 30 (30a, 30b) Multiple spacers 30a ', 30b' Reduced diameter portion 300 (300a, 300b, 300c, 300d) Multiple spacers L Optical axis

Claims (5)

The first lens, the aperture stop plate having a predetermined aperture, the second lens, and the first lens and the second lens, which are sequentially arranged from the object side to the image plane side. A lens unit comprising a spacer,
The spacer is arranged by joining a plurality of spacers having the same shape,
The aperture stop plate is sandwiched between any two spacers of the plurality of spacers,
A lens unit characterized by that. The plurality of spacers comprises two cylindrical spacers,
The aperture stop plate is sandwiched between the two spacers,
The lens unit according to claim 1. The two spacers have a cylindrical reduced diameter portion that is reduced in diameter so as to concentrically define a step,
The reduced diameter portions of each of the two spacers are arranged to face each other so as to sandwich the aperture diaphragm plate in cooperation with each other.
The lens unit according to claim 2. The first lens is a negative lens including an aspherical surface having negative refractive power with a concave surface facing the object side;
The second lens is a positive lens including an aspherical surface having a positive refractive power with a convex surface facing the object side.
The lens unit according to claim 1, wherein the lens unit is a lens unit. When the refractive index of the first lens is N1 and the Abbe number is ν1, the refractive index of the second lens is N2 and the Abbe number is ν2, the following conditional expressions (1) and (2)
(1) N1 = N2
(2) ν1 = ν2
The lens unit according to claim 1, wherein the lens unit is satisfied.

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