High resolution broadband monolithic spectrometer and method

Patent metadata

Field	Value
Publication number	US-10508951-B2
Application number	US-201716068316-A
Country	US
Kind code	B2
Filing date	Jan 6, 2017
Priority date	Jan 8, 2016
Publication date	Dec 17, 2019
Grant date	Dec 17, 2019

Abstract

A monolithic spectrometer ( 10 ) for spectrally resolving light (L), comprises a body ( 2 ) of solid material having optical surfaces ( 3,4,5,6 a - 6 c, 8 ) configured to guide the light (L) along an optical path (E 1 ,E 2 ,E 3 ,E 4 ) inside the body ( 2 ). The optical surfaces of the body ( 2 ) comprise a segmented focusing surface ( 6 a, 6 b ) comprising first and second continuously functional optical shapes (Ca,Cb) to focus received parts of respective beams (La,Lb) onto respective focal position (fa,fb) in an imaging plane (P) outside the body ( 2 ). The second continuously functional optical shape (Cb) is separated from the first continuously functional optical shape (Ca) by an optical discontinuity (Dab) there between.

First claim

The invention claimed is:

1. A monolithic spectrometer for spectrally resolving light, the monolithic spectrometer comprising a body of solid material having optical surfaces configured to guide the light along an optical path inside the body, the optical surfaces comprising:
an entry surface configured to receive the light to enter into the body as an entry beam;
a collimating surface configured to receive the entry beam and to reflect the entry beam as a collimated beam;
a grating surface configured to receive the collimated beam and to reflect diffracted beams in different directions according to a wavelength dependent diffraction angle;
a first focusing section configured to receive at least part of a first diffracted beam of the diffracted beams, the received at least part of the first diffracted beam having a first wavelength, the first focusing section having a first continuously functional optical shape to focus all received parts of the first diffracted beam onto a first focal position in an imaging plane outside the body;
a second focusing section configured to receive at least part of a second diffracted beam of the diffracted beams, the received at least part of the second diffracted beam having a second wavelength that is distinct from the first wavelength, the second focusing section having a second continuously functional optical shape to focus all received parts of the second diffracted beam onto a second focal position in the imaging plane, the second focal position being distinct from the first focal position, wherein the second continuously functional optical shape is separated from the first continuously functional optical shape by an optical discontinuity there between; and
an exit surface of an exiting part of the light exiting the body, the exit surface being arranged in the optical path inside the body between:
the first focusing section and the second focusing section, and
the imaging plane;

wherein the optical path inside the body defines a two dimensional plane of the body transverse to the optical surfaces,
wherein the optical discontinuity extends transverse to the two dimensional plane of the body,
wherein light focused onto the imaging place by the first focusing section has an average angle of incidence that is smaller than an average angle of incidence of light focused onto the imaging place by the second focusing section, and
wherein the first focusing section spans a larger opening angle than an opening angle of the second focusing section.

2. The monolithic spectrometer according to claim 1 , wherein the second focusing section is sloped towards the first focusing section in the two dimensional plane of the body compared to an extrapolated continuous optical curvature of the first focusing section beyond the optical discontinuity to reduce a distance between the first focal position and the second focal position along a spectral axis in the imaging plane compared to a single continuously functional optical shape.

3. The monolithic spectrometer according to claim 1 , wherein the optical discontinuity separates the focusing sections to receive diffracted light across different ranges of the wavelength dependent diffraction angle.

4. The monolithic spectrometer according to claim 1 , wherein the first focal position and the second focal position of the respective first focusing section and the second focusing section are projected along a line forming a spectral axis of spectrally resolved light in the imaging plane.

5. The monolithic spectrometer according to claim 1 , further comprising:
a third focusing section configured to receive at least part of a third diffracted beam of the diffracted beams, the received at least part of the third diffracted beam having a third wavelength that is distinct from the first wavelength and the second wavelength, the third focusing section having a third continuously functional optical shape to focus all received parts of the third diffracted beam onto a third focal position in the imaging plane, wherein the third continuously functional optical shape is separated from the second continuously functional optical shape by a second optical discontinuity there between.

6. The monolithic spectrometer according to claim 1 , wherein each of the first focusing section and the second focusing section is configured to receive a respective light beam from the grating surface at a different angle and focus the respective light beam at a respective focal position in the imaging plane.

7. The monolithic spectrometer according to claim 1 , wherein a part of the second diffracted beam falling on the first continuously functional optical shape is directed to another position that is separate from the second focal position of the part of the second diffracted beam falling on the second continuously functional optical shape.

8. The monolithic spectrometer according to claim 1 , wherein the first focusing section spans a larger surface and/or has a larger numerical aperture than the second focusing section.

9. The monolithic spectrometer according to claim 1 , wherein light impinging the imaging plane from a focusing section at a larger angle of incidence is provided by a respective one of the first focusing section and the second focusing section having a longer depth of focus than a depth of focus of light impinging the imaging plane from a focusing section at a smaller angle of incidence.

10. The monolithic spectrometer according to claim 1 , wherein the first focusing section is configured to image a first continuous wavelength range around the first wavelength onto the imaging plane and the second focusing section is configured to image a second continuous wavelength range around the second wavelength onto the imaging plane;
wherein the second continuous wavelength range is separated in wavelength from the first continuous wavelength range but is imaged directly adjacent to the first continuous wavelength range in the image plane.

11. The monolithic spectrometer according to claim 1 , wherein an image of a wavelength range imaged by the first focusing section partially overlaps an image of a wavelength range imaged by the second focusing section.

12. The optical system according to claim 11 , further comprising one or more band filters configured to filter wavelength ranges from the light.

13. An optical system for spectrally resolving light, the system comprising:
a monolithic spectrometer for spectrally resolving light, the monolithic spectrometer comprising a body of solid material having optical surfaces configured to guide the light along an optical path inside the body, the optical surfaces comprising:
an entry surface configured to receive the light to enter into the body as an entry beam;
a collimating surface configured to receive entry beam and to reflect the entry beam as a collimated beam;
a grating surface configured to receive the collimated beam and to reflect diffracted beams in different directions according to a wavelength dependent diffraction angle;
a first focusing section configured to receive at least part of a first diffracted beam of the diffracted beams, the received at least part of the first diffracted beam having a first wavelength, the first focusing section having a first continuously functional optical shape to focus all received parts of the first diffracted beam onto a first focal position in an imaging plane outside the body;
a second focusing section configured to receive at least part of a second diffracted beam of the diffracted beams, the received at least part of the second diffracted beam having a second wavelength that is distinct from the first wavele

Assignees

• TNO

Inventors

• Kruizinga Borgert
• Van Brug Hedser
• Van Beijnum Frerik

Classifications

• G01J3/0259

  Monolithic · CPC title

• G01J2003/1282

  Spectrum tailoring · CPC title

• G01J3/18

  using diffraction elements, e.g. grating (gratings per se G02B) · CPC title

• G01J2003/1204

  Grating and filter · CPC title

• G01J3/021

  using plane or convex mirrors, parallel phase plates, or particular reflectors · CPC title