JPS59202423A - Intermediate power projection lens for projection inspecting device - Google Patents

Abstract

PURPOSE:To extend operation distance and insert or incorporate a half-mirror by allowing an intermediate-power projection lens consisting of five groups to meet specific requirements. CONSTITUTION:The lens system consists of the 1st convergent group including a positive lens element, the 2nd divergent group having an intense concave surface on a subject side, the 3rd convergent group having a concave surface on an image side, the 4th convergent group including a cemented convergent lens which consists of a negative and a positive lens element successively from the image side and has the cemented surface convex to the image side, and the 5th group including a positive lens element having large curvature to the image side; and the half-mirror M is inserted between the 2nd and the 3rd groups. Then, conditional inequalities (1)-(7) hold. In the inequalities, LB is the lens back at the time of tracing from the image side, (f), FI II, and fI are the focal length of the whole system, composite focal length of the 1st and the 2nd groups, and focal length of the 1st group, and dII III is the air gap between the 2nd and the 3rd groups; and rIIA and rIIB are the radii of curvature of the image-side surface and object-side surface of the 2nd group lens, and nuIVA and B are Abbe numbers of glass of the positive and negative lens elements of the 4th group.

Description

Detailed Description of the Invention Technical Field The present invention relates to a projection lens used in a projection inspection device for enlarging and projecting an object to be inspected at a precise magnification, observing the projected image, and measuring the shape and dimensions. (This relates to a medium magnification projection lens of about 10x to 20x.

BACKGROUND OF THE INVENTION In general, the projection lens of a projection inspection device must perform projection at an accurate magnification, so the magnification error must be reduced.For this reason, various aberrations must be minimized, and in particular distortions directly related to the magnification error must be minimized. It is necessary to sufficiently reduce aberrations.It is also necessary that the lens has high contrast and brightness.

In addition to such general performance conditions, it is necessary to maintain a working distance of 7, that is, a sufficient distance between the projection lens and the object to be examined. This is because the working distance of a normal type lens is about half the focal length, but as the magnification increases, the focal length becomes shorter, and so the working distance also becomes shorter. If the working distance force S becomes short, not only will it be necessary to be careful in operation, but if there is an uneven force on the object to be inspected (uneven force), it will not be possible to observe the object sufficiently.

On the other hand, how should the projection inspection device illuminate the object to be inspected? -imo (transparent j
j There are rising lights and reflective lighting.

In transmitted illumination, in order to minimize the focusing error of the user, a condenser lens is used to make the luminous flux parallel to the optical axis. In addition, in the case of reflected illumination (a half mirror is installed on each light to view the object)
11, 侃[However, if the illumination light passes through the projection lens (well, telecentre 1 including the projection lens part)]
, it is necessary to consider making it a tsuku p, noboru system. in this case,
/＼-Rather than placing it outside the projection lens, it is better to place it inside.
≦O The actual working distance will be larger if the arrangement is J"L.)l, t4. There is a force S.

(Left margin) Purpose The present invention has been made in view of the above points, and is a compact medium magnification mirror that has high performance, a long working distance, and a half mirror that can be inserted or built-in. The purpose is to provide lenses.

- In order from the image side, the converging first group includes at least one positive lens component, the diverging second group with a strongly concave surface facing the object side, and the image side. A convergent 1st II'm containing a lens component with a concave surface directed to
.

・A convergent lens group consisting of a negative lens component and a positive lens component from the image side, including at least one convergent cemented lens whose cemented surface is convex toward the image side. ・A positive lens component with a strong curvature toward the image side. having group V of
This is achieved by a medium magnification projection lens in which a half mirror can be inserted between the 11th group and the 1st group.

(Left below) The above projection lens has a projection magnification of 10x + 0.5 < I-B/f < 1 after 10x projection magnification + FJ, where LB is the lens back when traced from the image side and f is the focal length of the entire system. .0
, at a projection magnification of around 20x, l, Q (LB car < 1.8. When the combined focal length of the 11th A and 11th group is Frn, -0.75 < f/FI n < 0.05. The 117i'
Even though it is possible to insert a half mirror between the lens unit 1 and the 1st II group, the length of the entire system is approximately 100 to 125 mm, resulting in a continuous configuration. Furthermore, distortion, which is important in terms of performance, can be suppressed to within +0.05%.

DESCRIPTION To explain the present invention, reference will be made specifically to FIG. 1, which shows the configuration of a first embodiment described later. In Figure 1, the left side is the image side, and the right side is the object side.
The 1st II group, the ■ group, and the ＼/p↑ are arranged in this order.

1st group and 1st I fY as front group F, 3rd group]ilj,
'g+'51V 7i1: If the V group is the rear group B, then 1■] Between the group 12 and the rear group I3, a number 1/...-Fumirar N can be inserted. The half mirror M is configured to swing and retreat from the optical path within the lens barrel during transmitted illumination, but its specific configuration will be omitted since a known mechanism can be used. Incidentally, although the half mirror is retracted for the purpose of improving the strength during transmitted illumination, it is clear that it may be fixed.

In the above configuration, the first group is a convergent lens group including at least one lens component with a concave surface facing the positive side, and the second group is composed of a negative lens component and a positive lens component from the image side, and the cemented surface is the image side. The Vth convergent lens group, which is a convergent lens group including at least one convergent cemented lens that is convex on the side, is a positive lens component lens Jj4 having a strong curvature on the image side.

” The lens back LB when tracing from the image side of the projection lens is 0.5 < LB/f < 1.0 at a projection magnification of around 10, where the focal length of the entire system is f, and the projection magnification is around 20 times. 1.0 <LB//< 1.8 To L4
This ensures sufficient working distance.

If the combined focal length of the front group F is FI-n, -
0,75< flFx - rx <Q, 05, and the projection magnification is approximately 10x and is almost afocal.

Furthermore, distortion is efficiently corrected by bringing the optical axis passing point of the off-axis chief ray to the 11th group.

In a lens with a projection magnification of around 20x, the front group F is a diverging system due to the above conditions, and because the distance between the front group F and the rear group B is large, the refractive power of the front group is relatively weak, so the lens back L
In addition to making B longer, we are trying to improve the Hetzhal sum.

The first V group has a strong curvature on the image side to correct spherical aberration and coma aberration.

Furthermore, each embodiment of the present invention satisfies the following conditions.

0.31<fl<1. ．． 1f ・・・・・・・・・
...head o, 6/ < dnm < t, tf
・・・・Self・・・・・・・■−〇, 5rIIA<rI
[B<0.2rI[A......C25<
C ■ B - C y A ・・・・・・・・・・・・ ■ However, f is the focal length of the entire system, C is the focal length of the first group, dn-
m is the air distance between the first group and the second group, rI [A is the radius of curvature of the image side surface of the second group lens, rIIA is the first I 17
The radius of curvature of the object-side surface of the lens, νVA, is the Abbe number of the glass of the negative lens component of the second group, and νyB is the Abbe number of the glass of the positive lens component of the second group.

If fl exceeds the lower limit of the conditional expression (■), the negative power of the first group becomes too strong in order to make the lens back LB 0.5 to 1.8 times the focal length f of the entire system, and the Petzval sum This makes it difficult to correct astigmatism. On the other hand, if the upper limit is exceeded, the negative power of the first group becomes too weak and the Petzval sum becomes large, making it difficult to correct astigmatism.

If the lower limit of condition (2) is exceeded, it becomes difficult to push in the half mirror. Increasing dim is advantageous in terms of aberration correction because it can weaken the power of the front and rear groups, but if it exceeds the upper limit, the height of incidence of the off-axis chief ray to the 1st II, IV, and V groups increases, resulting in distortion. correction becomes difficult.

If the lower limit of conditional formula (■) is exceeded, then rotation is used to correct the positive direction of spherical aberration caused by the H group, and if the upper limit is exceeded, the first If! The power of 'f becomes weaker, the Petzval sum increases, and it becomes difficult to correct the curvature of field.

Also, since a considerable amount of axial chromatic aberration is generated by the front group,
The second group is a cemented lens consisting of a negative lens with high dispersion glass and a positive lens with low dispersion glass to correct longitudinal chromatic aberration.
If conditional expression (■) is not satisfied, it becomes difficult to correct this longitudinal chromatic aberration.

By the way, when conditional expression (2) is added, the refractive index of the negative lens component of the (2)th fff becomes larger than the refractive index of the positive lens component, and a positive Petzval is generated.

Also No. 11. Since the Th' group is a convergent system, a fairly positive Petzval is generated for the entire rear J. In the embodiment of the present invention, this is absorbed by the negative Petzval of the H-th group, but in order to effectively generate negative Petzval, a lower refractive index is better. However, if the refractive index is made sufficiently low, the curvature of the first group becomes too strong to make the H-th group a predetermined power, and a positive spherical number difference occurs, making it difficult to correct. Furthermore, if the refractive index is set to high, it becomes difficult to effectively generate negative Petzval. Therefore, it is desirable that the refractive index n2 of the glass in the group (2) satisfies 164 < nn < 1.76.

Further, it is desirable for the average value of the Abbe number of the glass of the V-group lens system to be 55.0 or more in order to correct axial chromatic aberration.

Examples The configurations of Examples 1 to 9 of the present invention are shown in FIGS. 1 to 9, and the spherical aberration, astigmatism, and distortion of each example are shown in FIGS. 10 to 1.
They are shown in sequence in Figure 8.

1 to 9, 1. II, III, IV,
V represents the first to V groups, N1 represents the half mirror, 1F represents the eye 11, and the solid lines, one-dot chain line, two-dot chain line, and broken line in the figures showing spherical aberration and astigmatism in Figures 10 to 18 are common. Therefore, it is shown only in Fig. 10.

In addition, in Examples 1 to 4, the lateral magnification β--0,100, that is,
The projection magnification is 10 times, and Examples 5 to 9 (1 yellow magnification β・
--0,050, that is, the projection magnification is 20 times.

Further, the angle of view (2ω) is all 15°.

(Margin below) Example 1 f = 103.1 FNO, = 4.
5 Radius of curvature Distance between upper surfaces of shaft Refractive index (Nd) Dispersion (νd) Σd = 123.270 Example 2 f=95.0 FNO, = 4.0 Radius of curvature Heat between upper surfaces of shaft Refractive index (Nd) Dispersion (ν
d) Σd = 111.112 Example 3 f=95. OFNo, -4,0 Radius of curvature Axis spacing Refractive index (Nd) Dispersion (
νd) Nd = 109.092 Example 4 f=95. OFNO, = 4.0 Radius of curvature Axis spacing Refractive index (Nd) Dispersion (νd) Nd = 111.492 Example 5 f = 52.6 FNO, -3,5 Radius of curvature Axis'' spacing Refractive index (Nd ) Variance (
νd) Nd = 107.060 Example 6 f=52.0 l"'+10.-3.5
Radius of curvature Axis” biplanar spacing Refractive index (take Dispersion (ν(1)Nd = 103.94.5 Example 7 f = 52.OFno, = 3.5 Σd = 103.748 Example 8 f = 52.OFNO ,=,3.5 Radius of curvature Axial spacing Refractive index (Nd) Dispersion (νd)Σd'-LO3,361 Example 9 f=52.7 FNO,=3.
5 Radius of curvature Axial surface spacing Refractive index (Nd)
Dispersion (νd) Σd = LO5,153 LB/f, f/F■■, f1/f of each of the above embodiments,
rJum/f.

"I[B/r, IIA, vy, B, -vyAr,
, shown in Table 2-1.

As shown in Table 1, the present invention includes, in order from the image side: - a convergent first lens group including at least one positive lens component; - a divergent lens group with a strongly concave surface facing the object side. fA+J11 group,
- A convergent m-th group including a lens component with an open surface facing the image side; - At least one convergent cemented lens consisting of a negative lens component and a positive lens component from the image side and having a cemented surface or a convex surface toward the image side. It is a medium-magnification projection lens that has a convergent lens group (Ⅰ) that includes a lens element, and a positive lens component (v group) that has a strong curvature on the image side, and a half mirror can be inserted between the 0th group and the 111th group. Therefore, it has the advantages of high performance, sufficient working distance, and compactness even though a half mirror can be inserted or built-in.

[Brief explanation of drawings]

1 to 9 are lens configuration diagrams of Examples 1 to 9 of the present invention, and FIGS. 10 to 18 are aberration diagrams thereof. ■・Group 1 ■・Group 11 ■・Group ■ ■ ■
Group ■... Group ■ M. Half mirror F... Front group B... Rear group Applicant Minolta Camera Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 1''I B Figure 5 Figure 6 Figure F, B Figure 7 F B Figure 3 Figure q F B Figure 1O Figure 11 Planar aberration Astigmatism Distortion No. 12
Fig. 13 Fig. 14 Spherical aberration Well 1 can, Aberration Ball Curve No. 51 Ball east surface ■ Including difference J-point d difference
Distortion Figure 16 F3.5 '1. '／・
7,7゜Drawing 17 Artwork Menu Elementary School 4th Grade 1F, 6, Electrical Difference
Strain Figure 13

Claims (1)

[Claims] 1. A medium-magnification projection lens for a projection inspection device, which, in order from the image side, includes: - a convergent first group including at least one positive lens component; - a strongly concave surface facing the object side. The first group is divergent, and the second group is convergent, which includes a lens component whose surface is concave toward the image side. a convergent lens group containing at least one cemented lens with a positive polarity; - a positive lens component v tr* having a strong curvature on the image side;
and a half mirror is inserted between the 11th group and the
” High-performance medium magnification projection lens. 2. A medium magnification projection lens according to claim 1, which satisfies the following conditions. 0.5 < LB/f < 1.0. (Projection magnification 10
(around 20x projection magnification) -0,75 < fl Fl m < 0
．． 05 However, LB is the lens/<tsuku when tracing from the image side, f is the focal length of the entire system, and F1a is the 1st group and H
Combined focal length of the group. 3. A medium magnification projection lens according to claim 1 or 2, which satisfies the following conditions. 0゜3f < fl < 1.11 o, 6f < dnm < IAf -0,5"IIA <"nB< 0.2rllA2
5<C B - C A However, fl; Focal length of the 1st group f; Focal length of the entire system dnm; Air distance rlA between the 1st group 1st group The curvature of half one telor rI
IB Radius of curvature of the object side surface of the i-th group lens νyA;'
Crow's Atsube number νyB H of the negative lens component of [[
Crow's asohe number of positive lens component of V group