Doubly telecentric lens and imaging system for multiwell plates

Details Doubly telecentric lens and imaging system for multiwell plates Doubly telecentric lens and imaging system for multiwell plates

1998-03-10

2001-03-06

Epps, Georgia (Department: 2873)

Optical: systems and elements

Lens

Telecentric system

C359S754000

Reexamination Certificate

active

06198577

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to the imaging of multiwell plates, in particular, to the use of a doubly telecentric lens and system for accurate and efficient detection of low levels of light from high density multiwell plates.
BACKGROUND OF THE INVENTION
Microtiter or multi-well plates are becoming increasingly popular in various chemical and biological assays. Further, high-density format plates, such as 384, 864 and 1536 well plates, are beginning to displace 96-well plates as the plate of choice. Many of the assays conducted in multiwell plates employ some type of light detection from the plate as the reporter for positive or negative assays results. Such assays include fluorescence assays, luminescence assays (e.g., luciferase-based assays), phosphorescence assays, scintillation assays, and the like. In particular, with the advent of solid phase scintillating materials, capsules and beads, homogeneous scintillation proximity assays (SPA) are now being performed with increasing frequency in multiwell plates.
Detection of light signals from multiwell plates in the past has typically been done using plate readers, which generally employ a photodetector, an array of such photodetectors, photomultiplier tubes or a photodiode array to quantify the amount of light emitted from different wells. Such plate readers have been disclosed, for example, by Russell, et al., U.S. patent Ser. No. 4,810,096, issued Mar. 7, 1989, and VanCauter, et al., U.S. patent Ser. No. 5,198,670, issued Mar. 30, 1993. Although plate readers can detect the total light from each well, they have a number of limitations. For example, plate readers are typically not capable of resolving discrete light sources in a single well, so they could not be used, for example, to differentiate light from different beads in one well. Further, most plate readers have fewer photodetectors than there are wells in the plate, so at least some wells must be read serially, adding to the time required to complete the assays. This becomes a substantial problem in assays where the light signal is so low that each well needs to be in the detection field for an extended period of time (e.g., tens of minutes). In addition, most currently-available plate readers have been designed for 96-well plates. Although some can be adapted for, e.g., 384-well plates, the adaptation does not result in any significant increase in throughput, since a 384-well plate going through a modified 96-well reader typically takes four times as long to read as a 96-well plate.
Another technique that has been applied to the detection of light from multiwell plates is imaging. Prior art imaging systems typically comprise a standard 50-55 mm f1.4 photographic lens coupled to a camera. While such systems can be used to image an entire multiwell plate, and theoretically provide resolution of discrete light points within individual wells, they have poor sensitivity, even when coupled to efficient cameras, so that many assays still require imaging times of tens of minutes or more. Other assays, such as SPA bead-based assays, cannot be performed at all due to lack of sensitivity. Further, images acquired with such systems suffer from vignetting and lateral distortion effects, making it difficult or impossible to compare signals from center portions of the plate with signals from lateral wells.
The present invention provides lenses and systems which overcome the above-described disadvantages of prior art methods of light detection in multiwell plates. In particular, the present invention provides, for the first time, a doubly telecentric lens-based system with the ability to image SPA bead-based assays. The telecentric lens of the invention is economical to manufacture due to a design employing a minimal total number of lens elements, the use of spherical lens elements, and generous tolerance limits in lens fabrication. Further, the telecentric lens of the present invention is the first such lens to provide an unprocessed image of a multiwell plate that is substantially free from vignetting, chromatic aberration and distortion.
SUMMARY OF THE INVENTION
In one aspect, the present invention includes a multiple element doubly telecentric lens for imaging a substantially flat object onto an image plane. The lens is preferably color-corrected, particularly in the range of 400 nm-700 nm, and comprises, in succession from a side of incident light, the following lens elements or groups (illustrated in FIGS.
2
and
3
): (i) a biconvex field lens element L
1
, (ii) separated by a distance D from the field lens element, a positive meniscus lens element L
2
, concave toward the incident light side, (iii) a double-Gauss lens element group, (iv) a positive meniscus lens element L
10
, convex toward the incident light, (v) a positive meniscus lens element L
11
, convex toward the incident light, and (vi) a plano concave field flattener lens element L
12
, concave toward the incident light side. Changing distance D changes magnification of the telecentric lens.
In a preferred embodiment, the double-Gauss lens element group comprises, in succession from the side of incident light, (i) an incident-side lens element group, comprising, in succession from the side of incident light, (a) a biconvex lens element L
3
, (b) a positive meniscus lens element L
4
, convex toward the incident light, and (c) a doublet formed of two positive meniscus lens elements, L
5
and L
6
, both convex toward the incident light; (ii) an aperture stop; and (iii) an image-side lens element group, comprising, in succession from the side of incident light, (a) a doublet formed of a biconcave lens element L
7
and a biconvex lens element L
8
, the doublet being concave toward the incident light, and (b) a biconvex lens element.
The adjacent surfaces of the above-listed lens elements are preferably separated by distances as follows: between about 11.4″ and about 13.4″ between element L
1
and element L
2
; about 3.9″ between element L
2
and element L
3
; about 0.3″ between element L
3
and element L
4
; about 0.04″ between element L
4
and element L
5
; about 0.0″ between element L
5
and element L
6
; about 2.3″ between element L
6
and element L
7
; about 0.0″ between element L
7
and element L
8
; about 0.1″ between element L
8
and element L
9
; about 0.1″ between element L
9
and element L
10
; about 0.1″ between element L
10
and element L
11
; and about 0.3″ between element L
11
and element L
12
.
Further, the lens described above preferably has the following characteristics, where elements L
1
-L
12
are made of glass and have surfaces S
1
-S
24
; each of the surfaces is convex (CX), concave (CC) or plano (XX); and the CX and CC surfaces have a radius measured in inches:
Element
Glass
Surface
Radius
CX/CC
L1
Schott BK7
S1 
30.008″ 
CX
(No. 517642)
S2 
62.327″ 
CX
L2
Schott BK7
S3 
88.185″ 
CC
(No. 517642)
S4 
18.483″ 
CX
L3
Schott LaKN22
S5 
28.992″ 
CX
(No. 651559)
S6 
19.682″ 
CX
L4
Schott LaKN22
S7 
6.938″
CX
(No. 651559)
S8 
26.500″ 
CC
L5
Schott LaFN28
S9 
2.644″
CX
(No. 773496)
S10
3.024″
CC
L6
Ohara PBH53
S11
3.024″
CX
(No. 847239)
S12
1.564″
CC
L7
Ohara PBH53
S12
1.836″
CC
(No. 847239)
S14
14.212″ 
CC
L8
Schott LaFN28
S15
14.212″ 
CX
(No. 773496)
S16
2.776″
CX
L9
Ohara LAL14
S17
6.589″
CX
(No. 697555)
S18
8.284″
CX
 L10
Ohara LAL14
S19
2.798″
CX
(No. 697555)
S20
10.465″ 
CC
 L11
Schott BK7
S21
5.195″
CX
(No. 517642)
S22
7.752″
CC
 L12
Ohara LAH53
S23
7.236″
CC
(No. 806410)
S24
PLANO
XX
In another embodiment, the telecentric lens is designed to form a focused image at the image plane when the field lens element (L
1
) is positioned between about 20 mm and about 30 mm, preferably about 25mm from the object. In other embodiments, distance D is preferably betwee

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