RU2278403C1 - Telocentric objective - Google Patents

Abstract

FIELD: optical engineering.

SUBSTANCE: telocentric objective can be used for operation with CCD arrays. Objective has 11 single lenses grouped in three groups composed of three, one and seven lenses along the ray path. Lenses 1, 5, 8 and 11 are menisci, which are turned with convexity to object. Lens is 2 has to be biconvex lens. Lenses 3, 6 and 9 have to be biconvex lenses and lenses 4, 7, 9 and 10 are menisci turned with their concavity to object. Focal distances of several groups and subgroups of lenses correspond to relations given in formula of the invention. High-quality image is achieved in common focal plane simultaneously in three spectral ranges: Δλ1=0,5-0,6; Δλ2=0,6-0,7 and Δλ3=0,79-0,9 micrometer.

EFFECT: widened spectral range.

2 cl, 1 dwg

Description

The present invention relates to optical devices and can be used as a lens with a telecentric ray path for working in the spectral range of 0.5 ... 0.9 μm, for example with CCD arrays.

Known for wide-angle (90 °) telecentric lens (SU No. 1117570 A1, class G 02 B 13/22, publ. 07.10.84), containing nine single lenses and menisci, namely, along the beam: positive and two negative meniscus convex to the object, aperture diaphragm, positive and negative menisci turned by concavity to the object, two biconvex lenses and positive and negative menisci convex to each other. The relative aperture of the lens 1: 5, focal length 10 mm, designed for a wavelength of 546 Nm.

The closest in technical essence to the proposed one is a wide-angle telecentric lens (JP 11084232 A, class G 02 B 13/04, publ. March 26, 1999) containing three lens groups: in the first group G ₁ , along the beam, biconvex lens G _1-1 and a subgroup G _1-2 of a negative meniscus convex to the object and a biconcave lens, in the second group G ₂ a positive lens, in the third group G ₃ a negative lens, a positive meniscus and a biconvex form a subgroup G _3-1, and gluing of the biconvex and biconcave lenses and two FEB Coconvex lenses form a subgroup G _3-2, wherein the following relations are satisfied in the lens:

(1) 0.2 <| f ₁ / f ₃ | <0.8

(2) 0.01 <| f / f ₂ | <0.7

(3) 0.01 <| f ₁ / f _1-1 | <0.5

(4) 0.7 <| f _1-2 / f ₁ | <1.0

(5) | f ₃ / f _3-1 | <0.6

(6) 0.5 <| f ₃ / f _3-2 | <0.95

where f ... are the focal lengths of the corresponding groups of lenses or objective. The lens has a large rear segment (up to 100 mm), aperture 1: 4, it works in the visible region of the spectrum (0.486 ... 0.656 nm).

The objective of the present invention is to provide a telecentric lens with an extended spectral range from 0.5 to 0.9 μm, in particular for sub-ranges: 0.5 ÷ 0.6; 0.6 ÷ 0.7; 0.79 ÷ 0.9 μm in a single focal plane and high image quality throughout the field.

The technical result due to the task is achieved by the fact that in a telecentric lens containing three groups of lenses of three, one and seven lenses, respectively, the first group G ₁ includes a second negative lens, the second group G ₂ - the fourth positive lens, the third group G ₃ - the fifth lens is a negative meniscus convex to the object, the sixth positive lens, the eleventh positive lens, while, in contrast to the known, the first and eighth lenses are made in the form of negative menisci, are inverted x the convexity to the object, the second lens is biconcave, the third, sixth and ninth are biconvex, the fourth is the meniscus facing the concavity to the object, the seventh and tenth are negative menisci that are convex to the image, the eleventh is the meniscus facing concavity to the image. It is recommended that the following ratios of focal lengths (f.r.) of lens groups and subgroups are fulfilled in the lens:

1.2 <| f ₁ / f ₃ | <2.0

1.0 <| f ₁ / f _1-1 | <1.8

4.0 <| f _1-2 / f ₁ | <9.0

0.6 <| f ₃ / f _3-1 | <0.8

0.37 <| f ₃ / f _3-2 | <0.49, where

f ₁ - f.r. groups G ₁ (lenses 1, 2 and 3);

f ₃ - f.r. Group G ₃ (lenses 5-11);

f _1-1 - f.r. first lens;

f _1-2 - f.r. subgroups of 2 and 3 lenses;

f _3-1 - f.r. subgroups of 5, 6 and 7 lenses;

f _3-2 - f.r. subgroups of 8, 9, 10 and 11 lenses.

The proposed implementation of the lens allows to obtain the construction of high-quality images in a single focal plane simultaneously in three spectral ranges: Δλ1 = 0.5 ÷ 0.6; Δλ2 = 0.6 ÷ 0.7; Δλ3 = 0.79 ÷ 0.9 μm.

The optical scheme is illustrated in the drawing.

The lens consists of 11 single lenses grouped in groups of G ₁ of three lenses, G ₂ - one lens, aperture diaphragm (AP) and group G ₃ of 7 lenses. These lenses are, along the ray: 1 - negative meniscus, convex to the subject G _1-1 ; 2 - biconcave lens; 3 - biconvex lens; while lenses 2 and 3 form a subgroup G _1-2 ; 4 - positive meniscus facing concavity to the subject (G ₂ ); 5 - negative meniscus convex to the object, 6 - biconvex lens, 7 - negative meniscus convex to the image, while lenses 5, 6 and 7 form a subgroup G _3-1 ; 8 - negative meniscus, similar to meniscus 5; 9 - a biconvex lens, 10 - a negative meniscus, similar to the meniscus 7, 11 - a positive meniscus facing concavity to the image, while lenses 8, 9, 10 and 11 form a subgroup G _3-2 . Between the groups of G ₂ and G ₃ is the aperture diaphragm 12.

The design parameters of the lens embodiment are as follows:

Radii Thickness Glass mark Diameters of surface R1 = 45.08 38.5 d1 = 5.0 Tk21 R2 = 22.18 31,4 d2 = 8.0 R3 = -3311.0 30.8 d3 = 5.0 TF2 R4 = 27.29 28,4 d4 = 8.7 R5 = 159.96 30,4 d5 = 8.0 TF2 R6 = -41.4 31.1 d6 = 8.3 R7 = -35.4 28.6 d7 = 8.0 Ok4 R8 = 25.59 29.1 d8 = 25.0 R9 = 0,0 11.9 d9 = 13.7 R10 = 113.18 19.3 d10 = 5.0 K8 R11 = 26.06 21,2 d11 = 2.0 R12 = 30.27 23.5 d12 = 10.0 Ok4 R13 = -24.77 25.0 d13 = 1.9 R14 = -22.8 25.0 d14 = 5.0 TF2 R15 = -35.08 28.0 d15 = 10.0 R16 = 218.3 31.7 d16 = 5.0 K8 R17 = 32.66 32.9 d17 = 3.0 R18 = 41.86 35,4 d18 = 12.0 OK4 R19 = -29.51 36.0 d19 = 10.1 R20 = -32.06 32.9 d20 = 5.0 TK21 R21 = -73.62 35.3 d21 = 10.0 R22 = 137.72 37.8 d22 = 8.0 K8 R23 = 610.9 38,0

The focal lengths of lens groups and their ratios for this embodiment are as follows:

f ₁ = -115.9 | f ₁ : f ₃ | = 1,53 f ₃ = 75.07 | f ₁ : f _1-1 | = 1,56 f _1-1 = -73.79 | f _1-2 : f ₁ | = 6.1 f _1-2 = 709.2 | f ₃ : f _3-1 | = 0.67 f _3-1 = 112.02 | f ₃ : f _3-2 | = 0.44 f _3-2 = 170.14

The parameters of this lens embodiment:

- working spectral range 0.5 ÷ 0.9 μm; - focal length 40.0 mm; - back focal segment 25.2 mm; - angular field of view 54 ° - linear field in image space ⌀40 mm; - relative hole 1: 6.0.

The lens is designed to work with a CCD receiver. It gives an image of the objects to the receiver of the CCD. Therefore, it is calculated taking into account the installation in the gap S _{F 'of a} protective glass of an optoelectronic unit, a glass of a filter and a photodetector, respectively 5 mm, 3 mm and 0.4 mm thick.

The image quality of the lens is characterized by its frequency response.

So, for a frequency of N = 70 ln / mm, the image contrast is of the order of:

Range, microns 0.5 ÷ 0.6 0.6 ÷ 0.7 0.79 ÷ 0.9 Mer. Sag. Mer. Sag. Mer. Sag. Point on axis 0.67 0.6 0.5 Mid field of view 0.58 0.64 0.58 0.58 0.51 0.55 Field of vision 0.43 0.56 0.38 0.53 0.42 0.46

where measures. - meridian section;

sag. - sagittal section.

Claims (2)

1. A telecentric lens containing three groups of lenses: of three, one and seven lenses along the ray, of which the first group G ₁ includes a second negative lens, the second group G ₂ - a fourth positive lens, the third group G ₃ - a fifth lens - negative the meniscus convex to the object, the sixth positive lens, the eleventh positive lens, characterized in that the first and eighth lenses are negative menisci, convex to the object, the second is biconcave, the third, sixth and ninth are biconvex, the fourth is men ck facing concavity to the object, the seventh and the tenth - negative meniscus which is convex to the image, the eleventh - the meniscus facing the concavity of the image. 2. The telecentric lens according to claim 1, characterized in that it fulfills the following relationships: 1,2 <| f ₁ / f ₃ | <1,8, 1.0 <| f ₁ / f _1-1 | <2.0, 4.0 <| f _1-2 / f ₁ | <8.0, 0.6 <| f ₃ / f _3-1 | <0.8, 0.2 <| f ₃ / f _3-2 | <0.49, where f ₁ - the focal length (f.r.) of the group G ₁ (lenses 1, 2 and 3); f ₃ - f.r. Group G ₃ (lenses 5-11); f _1-1 - f.r. the first lens G _1-1 ; f _1-2 - f.r. subgroups G _1-2 of 2 and 3 lenses; f _3-1 - f.r. subgroups G _3-1 of 5, 6 and 7 lenses; f _3-2 - f.r. subgroups G _3-2 of 8, 9, 10 and 11 lenses.