Multifunctional sky camera system for total sky imaging and spectral radiance measurement

• US 10,110,838 B2
• Filed: 09/11/2017
• Issued: 10/23/2018
• Est. Priority Date: 04/30/2013
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Hamann, Hendrik F., Lu, Siyuan
• Primary Examiner(s): Anderson, II, James M
• Application Number:
  US15/700,777
• Publication Number:
  US 20180013968A1
• Time in Patent Office: 407 Days
• Field of Search: None
• CPC Class Codes: G01W 1/12 Sunshine duration recorders measuring intensity of sunshine G01J
• CPC Class Codes: G06T 2207/10021 Stereoscopic video; Stereoscopic image sequence
• CPC Class Codes: G06T 5/94 based on local image properties, e.g. for local contrast enhancement
• CPC Class Codes: G06T 7/20 Analysis of motion motion estimation for coding, decoding, compressing or decompressing digital video signals H04N19/43, H04N19/51
• CPC Class Codes: G06T 7/215 Motion-based segmentation
• CPC Class Codes: G06T 7/593 from stereo images
• CPC Class Codes: G06T 7/85 Stereo camera calibration
• CPC Class Codes: H04N 13/239 using two 2D image sensors having a relative position equal to or related to the interocular distance H04N13/243 takes precedence
• CPC Class Codes: H04N 23/60 Control of cameras or camera modules
• CPC Class Codes: H04N 23/69 Control of means for changing angle of the field of view, e.g. optical zoom objectives or electronic zooming
• CPC Class Codes: H04N 23/698 for achieving an enlarged field of view, e.g. panoramic image capture
• CPC Class Codes: H04N 23/75 by influencing optical camera components
• CPC Class Codes: H04N 25/621 for the control of blooming

Abstract

A multifunctional sky camera system and techniques for the use thereof for total sky imaging and spectral irradiance/radiance measurement are provided. In one aspect, a sky camera system is provided. The sky camera system includes an objective lens having a field of view of greater than about 170 degrees; a spatial light modulator at an image plane of the objective lens, wherein the spatial light modulator is configured to attenuate light from objects in images captured by the objective lens; a semiconductor image sensor; and one or more relay lens configured to project the images from the spatial light modulator to the semiconductor image sensor. Techniques for use of the one or more of the sky camera systems for optical flow based cloud tracking and three-dimensional cloud analysis are also provided.

Claims

1. A sky camera system, comprising:

an objective lens having a field of view of greater than or equal to 170 degrees;

a spatial light modulator at an image plane of the objective lens, wherein the spatial light modulator is programmable and is configured to attenuate light from objects including direct sun in images captured by the objective lens such that the sky camera system is configured to obtain sky images including an image of the sun;

at least one anti-blooming semiconductor image sensor behind the spatial light modulator; and

one or more relay lenses, between the spatial light modulator and the anti-blooming semiconductor image sensor, configured to project the images from the spatial light modulator to the anti-blooming semiconductor image sensor, wherein the spatial light modulator is configured to attenuate the image of the sun such that the image of the sun can fit into a dynamic range of the anti-blooming semiconductor image sensor, and wherein a response of the sky camera system, prior to field operation, has been calibrated indoors using a calibration light source of known radiation intensity with the spatial light modulator set to transparent, and

wherein the sky camera system is free of a mechanical sun blocker and thus can obtain a complete sky image.

2. The sky camera system of claim 1, wherein the objective lens comprises a fish eye lens.

3. The sky camera system of claim 1, wherein the spatial light modulator comprises a liquid crystal modulator, a quantum well modulator, or a micro-blinds based modulator.

4. The sky camera system of claim 1, wherein the anti-blooming semiconductor image sensor comprises a charge-coupled device (CCD) sensor.

5. The sky camera system of claim 1, wherein the anti-blooming semiconductor image sensor comprises a complementary metal-oxide semiconductor (CMOS) sensor.

6. The sky camera system of claim 1, further comprising:

a spectral filtering component between the objective lens and the anti-blooming semiconductor image sensor configured to switch between desired wavelength windows, wherein the spectral filtering component comprises mechanically-switched filter wheels.

7. The sky camera system of claim 1, wherein the anti-blooming semiconductor image sensor comprises a sensor covering from about 400 nm to about 1,100 nm spectral region.

8. The sky camera system of claim 1, wherein the sky camera system comprises multiple anti-blooming semiconductor image sensors and multiple relay lenses, and wherein the sky camera system further comprises:

a dichromatic filtering component between the objective lens and the multiple anti-blooming semiconductor image sensors configured to capture images from multiple desired wavelength windows via the multiple relay lenses each of which couples the image plane of the objective lens to a corresponding one of the multiple anti-blooming semiconductor image sensors.

9. The sky camera system of claim 8, wherein the dichromatic filtering component comprises electrochromatic glass, liquid crystal, or acousto-optical grating.

19. The sky camera system of claim 1, wherein the calibration light source of know radiation intensity is a calibration lamp on an integration sphere.

10. A total sky imaging system, comprising:

at least one first sky camera system and at least one second sky camera system, wherein the first sky camera system and the second sky camera system each includes (i) an objective lens having a field of view of greater than or equal to 170 degrees, (ii) a spatial light modulator at an image plane of the objective lens, wherein the spatial light modulator is programmable and is configured to attenuate light from objects including direct sun in images captured by the objective lens such that the first sky camera system and the second sky camera system are each configured to obtain sky images including an image of the sun, (iii) at least one anti-blooming semiconductor image sensor behind the spatial light modulator, and (iv) one or more relay lenses, between the spatial light modulator and the anti-blooming semiconductor image sensor, configured to project the images from the spatial light modulator to the anti-blooming semiconductor image sensor, wherein the spatial light modulator is configured to attenuate the image of the sun such that the image of the sun can fit into a dynamic range of the anti-blooming semiconductor image sensor, and wherein a response of the first sky camera system and the second sky camera system, prior to field operation, has been calibrated indoors using a calibration light source of known radiation intensity with the spatial light modulator set to transparent, wherein the first sky camera system and the second sky camera system are each free of mechanical sun blockers and thus can obtain complete sky images, and

wherein the first sky camera system and the second sky camera system are located at a distance of from about 100 meters to about 1,000 meters from one another.

11. The total sky imaging system of claim 10, wherein the first sky camera system and the second sky camera system each further includes (v) a spectral filtering component between the objective lens and the anti-blooming semiconductor image sensor configured to switch between desired wavelength windows.

12. The total sky imaging system of claim 10, wherein the objective lens comprises a fish eye lens.

13. The total sky imaging system of claim 10, wherein the spatial light modulator comprises a liquid crystal modulator, a quantum well modulator, or a micro-blinds based modulator.

14. The total sky imaging system of claim 10, wherein the anti-blooming semiconductor image sensor comprises a CCD sensor.

15. The total sky imaging system of claim 10, wherein the anti-blooming semiconductor image sensor comprises a CMOS sensor.

16. The total sky imaging system of claim 10, wherein the anti-blooming semiconductor image sensor comprises a sensor covering from about 400 nm to about 1,100 nm spectral region.

17. The total sky imaging system of claim 10, wherein the first sky camera system and the second sky camera system each comprises multiple anti-blooming semiconductor image sensors and multiple relay lenses, and wherein the first sky camera system and the second sky camera system each further comprises:

a dichromatic filtering component between the objective lens and the multiple anti-blooming semiconductor image sensors configured to capture images from multiple desired wavelength windows via the multiple relay lenses each of which couples the image plane of the objective lens to a corresponding one of the multiple anti-blooming semiconductor image sensors.

18. The total sky imaging system of claim 17, wherein the dichromatic filtering component comprises electrochromatic glass, liquid crystal, or acousto-optical grating.