JPS5868711A - Objective lens - Google Patents

Abstract

PURPOSE:To reduce the number of lens elements to a single lens and to correct the aberrations of an objective lens with respect to monochromatic light, more particularly 0.8mum wavelength light, by using an inexpensive lens material and introducing an aspherical surface. CONSTITUTION:An objective lens 1 which is used in combination with a collimator lens is a biconvex single lens and the 1st face thereof is a convex face of a small radius r1 of curvature and is an aspherical face which is approximated by hyperbolas near the vertex and includes up to the terms proportional to the 10th power of indident height. The 2nd face thereof is a convex face of a large radius r2 of curvature. When the focal length of the lens is defined as (f), the refractive index as nd and the interface space as d1, these have the relations (i) 1.48<nd<1.50, (ii) -0.42<r1/r2< -0.37, (iii) 0.6<d1/f<0.82. The conditions (i) are the conditions of an inexpensive lens material, for which a reduction in costs is realized by using materials of low refractive indices. The conditions (ii) and (iii) correct wave front aberrations and are limiting conditions for satisfying sine conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention can be applied, for example, to Hideo Y, (suf, '-necessary to the desk), academic field/1. ) Utilization of the proboscis lens, especially the collimator lens. 1. <S%
'J! Of course, this is related to the V7.

Used for bib-o-tisks, etc. 7" l/l) j Hitoto's exhibit lens trJ:... It is made up of 114 threads of 3 to 5 pieces of wood. It
7) It's enough to support the Saikai fl & Yoshui-kai 1) Of course, it's cheap, auto-focus on history, Tonno ＼
- Due to the necessity of the Ngoolibo, it is important that it be small and lightweight. ``Low price, small size and light weight'', Karuni C-11
Although it is safe to reduce the number of lenses and reduce the number of lenses, compared to the conventional spherical glass lenses, the I'! 'It is difficult to satisfy these requirements while maintaining VI high 1 and 1 performance in the present invention.' H4: Use 1 In addition, by introducing an aspherical surface, the number of lenses is reduced to 1'1 lens, and +1'1 color) is 4, and 'l'!+ is Oj87.
The present invention provides an objective lens that has 11 mos of aberration compensation for light with a wavelength of 1 m.

The present invention will be explained in detail below.

FIG. 1 shows an example of the structure of the objective lens of the present invention.

1 is the objective lens, 2 is the cover glass of the disk 1
0 The lens configuration of the present invention consists of a single double-convex lens, and the first curve is a small convex ++'+i with a radius of curvature r1, and is approximated by a hyperbola near the apex 1, and is proportional to the 10th power of the incident height. The second surface is a convex surface with a large radius of curvature r2, and the focal length of the lens is f, the refractive index is n1, and the distance is d (+) 1.4 s (nd (1)). ,50(11)
-〇, 42 (r, /r2(-o.37(iii)
0.6 < d, /f (has the relationship o, s 2.

The lens according to the present invention uses at least the first element as an aspherical surface to correct wavefront aberration, thereby realizing a single lens with a numerical aperture of approximately 0.46, compared to the conventional three to five elements. The number of spheres +r[i] has been significantly reduced compared to the i-series objective lens. The shape of the aspherical surface that constitutes the first surface 1.
1st part 11', 1, (niI,...&l-)',)l
1111V (concerning, tangent 'F 1li at each incident height y
j in i-J, l 驕III Z +:+:,1. /r=
C1 conic constant is 1 (, l-1 ~ and then 1 (1) Δ71
．． /, ),, Gy + D''-...- Here, D, E, F, and G are masculine face coefficients.

Wave + M Aberration compensation iE &) Point K'+, 1st +f
ii (1, 1, Ii'! It is desired that the point II! E is rotationally symmetrical about the major axis (1") on a circular surface, -, "r JLl). That is, a cone The constant is -1(k(.

There will be a relationship like this. , -The first side of the men's field is still his side; 1. 'Noura 11. It is good to sink from the point to the term G y IO! 7 Toshii 3, then explain conditions (1) to jiii) 1
, Regarding (i) ii, I am using a cheap lens of 4J and N, and I am using the old model with a 1fil 1lli rate (I use 1~ to lower the price). 5, I] 11,
-1'Crylic resin plastic material Oni'i (nd-
1,491) ', When using ry, it has 1 bite compared to a crow and has a friend width f,) : + Stretch run is 11 abilities. In addition to making it easier to process aspherical surfaces, which is difficult to do with glass, it also has a specific gravity that is much smaller than that of glass, so it can be used for electric melting as easily as 5
Next, conditions (1) and (iii) are limiting conditions for compensating for wavefront aberration and satisfying the first chord condition.

If it is sufficient to correct the aberrations only on the axis -L, it is sufficient to make only the first element of the single lens aspheric. In order to improve the correction of off-axis aberrations, it is necessary to make the second element of the single lens also an aspherical surface. In this case, from the point of view of off-axis wavefront aberration correction, the first surface is a convex surface with a small radius of curvature r2, and is approximated by a hyperboloid (k<-1) near the apex, which is proportional to the 10th power of the incident height. It becomes an aspheric surface that includes up to the term .

Specific examples of the objective lens of the present invention are shown below.

(Example 1) f-8.351 NA-0,46 object image distance L)
L-) r, *=4.899 d, =6.61n
”=-1,486r2=-13,069d2-23.s
Complete r 3 =, i:, 0-1 d 3 = 1,
20 1*==1.500 r4* mark Ihara 1Ti1 knee 0.12104 D=--0,624,0O
X10-'E----〇, 17009×1σ+1
-, -o, γ6428XIO' G=-0,190
88
Rate (Example 2) f-4,053 NA -0,45 object 1゛; distance 1-11
(×)r, *1=2.456 d, -2,8On"'
1.485r2--6.183 d2-1.75
j, (f+d5=:1.2 n*=1.
600 r4-tl, +* mark Aspheric surface * 1 * 2k
-0,11934-38774 D -0,51249X10-2 0.1394.9
X1σ2E −0,52200X1σ3 0.180
2/I\10zuF -0,78663X 10-'
-0,16653ゝ・ζ1O-4C-0,13150X
10"" -0,68100XI O'n*Qsu0.
8 μm refractive index diagram 2 kl, aberration diagram of Example 1, diagram 3 01, real M11
The aberration diagram of Example 2 is shown.

Rayleigh Limino I. is used as a tolerance for the objective lens. This indicates that it is sufficient if the wavefront aberration is corrected to 1/or less of the wavelength.

Since the present invention uses a wavelength of 0.088 m, the wavefront aberration only needs to be 0.2 μm or less.
The characteristics in the figure satisfy this requirement.

As is clear from the above description, according to the present invention, it is possible to provide an objective lens whose aberrations are well corrected.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an objective lens in one embodiment of the present invention, and FIGS. 2 and 3 are characteristic diagrams showing aberration performance in each embodiment. 1. Objective lens, 2. Cover glass. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Top surface q x Difference 1r-1*1

Claims (3)

[Claims] (1) Consisting of a double-convex single lens, the focal length of the lens is fl, the refractive index is nds, the surface spacing is dl and j-, the first surface is a convex surface with a small radius of curvature r1, and the apex is elliptical. The second surface is a convex surface with a large radius of curvature r2, and the following condition (1) 1,4 s (nd (1,50( 11)
-〇, 42 < r, / r2 (-〇, 37 (m)
1. ), 6 (an objective lens satisfying the following relationship: f/f<0.82. (2) A patent claim characterized in that the second surface is a convex surface with a large radius of curvature r2, is approximated by a hyperboloid near the apex, and is an aspheric surface including a term proportional to the 10th power of the incident height. Range of objective lens described in item (1) ○ (3) Paragraph (1) of the patent claim characterized in that the lens is made of a plastic material! '＋'
i i/koQl, ;'g'r (2) The moon and moon described in trouble 1.