Sky luminance mapping system and mapping method

Patent metadata

Field	Value
Publication number	US-9829376-B2
Application number	US-201514831859-A
Country	US
Kind code	B2
Filing date	Aug 20, 2015
Priority date	Mar 9, 2015
Publication date	Nov 28, 2017
Grant date	Nov 28, 2017

Abstract

A sky luminance mapping system includes a camera unit, two pyranometer units and a processing unit. Camera unit includes a fisheye lens to shoot image of sky dome and is equipped with light-shading devices which block the sun from the camera unit corresponding to instant location of the sun at instant time. First pyranometer unit measures daylight illuminance from the sky dome and outputs first intensity signal while the light-shading device is applied to block the sun. Second pyranometer unit measures daylight illuminance from the sky dome and outputs second intensity signal without blocking the sun. A reference intensity value is obtained by subtracting a value of the first intensity signal from a value of the second intensity signal. According to the value of the first intensity signal and the reference intensity value, a total luminance of and the luminance distribution in the image of the sky dome are corrected.

First claim

What is claimed is:

1. A sky luminance mapping system comprising:
a camera unit comprising:
a first support mechanism;
a digital camera arranged on the first support mechanism, the digital camera having a fisheye lens to shoot an image of a sky dome; and
a first light-shading device arranged on the first support mechanism, a location of the first light-shading device corresponding to an instant location of a sun at an instant time, such that the first light-shading device blocks the sun from the digital camera;

a first pyranometer unit comprising:
a second support mechanism;
a first pyranometer arranged on the second support mechanism, the first pyranometer measuring the daylight illuminance from the sky dome to output a first intensity signal; and
a second light-shading device arranged on the second support mechanism, a structure of the second light-shading device being the same as a structure of the first light-shading device, a location of the second light-shading device corresponding to the instant location of the sun at the instant time, such that the second light-shading device blocks the sun from the first pyranometer, wherein the second support mechanism and the second light-shading device corresponding to the first support mechanism and the first light-shading device are separately arranged, or the second support mechanism and the second light-shading device are common devices used as the first support mechanism and the first light-shading device;

a second pyranometer unit comprising:
a third support mechanism; and
a second pyranometer arranged on the third support mechanism, the second pyranometer measuring the daylight illuminance from the sky dome to output a second intensity signal while the sun is not being blocked; and

a processing unit, receiving the first intensity signal output by the first pyranometer, the second intensity signal output by the second pyranometer, and the image of the sky dome shot by the digital camera, wherein a reference intensity value is obtained by subtracting a value of the first intensity signal from a value of the second intensity signal, and a total luminance of and the luminance distribution in the image of the sky dome are corrected according to the value of the first intensity signal and the reference intensity value.

2. The sky luminance mapping system of claim 1 , wherein the first light-shading device and the second light-shading device are light-shading rings, and a ring surface of each of the light-shading rings corresponds to a trajectory plane of the sun, so as to block the sun from the digital camera and the first pyranometer.

3. The sky luminance mapping system of claim 1 , wherein the first light-shading device and the second light-shading device are light-shading domes, and a local region of a dome surface of each of the light-shading domes corresponds to the sun is controlled to block the sun from the digital camera and the first pyranometer.

4. The sky luminance mapping system of claim 1 , wherein the luminance distribution in the image of the sky dome is corrected according to the reference intensity value by adding a luminance of a direct sunlight at the instant location to a corrected luminance and the corrected luminance distribution of the image of the sky dome according to the first intensity signal.

5. The sky luminance mapping system of claim 1 , wherein the first light-shading device and the second light-shading device are light-shading sheets, and an area shaded by the light-shading sheets is moved together with time by a control mechanism according to a trajectory of the sun.

6. The sky luminance mapping system of claim 1 , wherein the digital camera is a high dynamic range imaging camera.

7. A sky luminance mapping method comprising:
shooting an image of a sky dome by a digital camera, wherein a first light-shading device with respect to an instant location of a sun at an instant time is configured to block the sun from the digital camera;
measuring a daylight illuminance from the sky dome by a first pyranometer unit to output a first intensity signal, wherein a structure of a second light-shading device is the same as a structure of the first light-shading device, and a location of the second light-shading device corresponds to the instant location of the sun at the instant time, such that the second light-shading device blocks the sun from a first pyranometer, wherein a second support mechanism and the second light-shading device corresponding to a first support mechanism and the first light-shading device are separately arranged, or the second support mechanism and the second light-shading device are common devices used as the first support mechanism and the first light-shading device;
measuring a daylight illuminance from the sky dome by a second pyranometer unit to output a second intensity signal while the sun is not being blocked; and
subtracting a value of the first intensity signal from a value of the second intensity signal by a processing unit to obtain a reference intensity value, wherein a total luminance of and the luminance distribution in the image of the sky dome shot by the digital camera are corrected according to the value of the first intensity signal, an area of the sky dome shaded by the first light-shading devices has a luminance, and the luminance distribution of the shaded area is corrected according to the reference intensity value and the corrected luminance distribution of the image.

8. The sky luminance mapping method of claim 7 , wherein the first light-shading device and the second light-shading device are light-shading rings, and a ring surface of each of the light-shading rings corresponds to a trajectory plane of the sun, so as to block the sun from the digital camera and the first pyranometer.

9. The sky luminance mapping method of claim 7 , wherein the first light-shading device and the second light-shading device are light-shading domes, and a local region of a dome surface of each of the light-shading domes corresponds to the sun is controlled to block the sun from the digital camera and the first pyranometer.

10. The sky luminance mapping method of claim 7 , wherein the luminance of the image of the sky dome is corrected according to the reference intensity value by adding a luminance of a direct sunlight to a corrected luminance of the image of the sky dome according to the first intensity signal.

11. The sky luminance mapping method of claim 7 , wherein the first light-shading device and the second light-shading device are light-shading sheets, and the area shaded by the light-shading sheets is moved together with time by a control mechanism according to a trajectory of the sun.

12. The sky luminance mapping method of claim 7 , wherein the digital camera is a high dynamic range imaging camera.

Assignees

• Univ Nat Taiwan Science & Technology

Inventors

• Chiou Yun-Shang

Classifications

• G01J1/0418

  using attenuators · CPC title

• G01J1/4214 Primary

  specially adapted for view-taking apparatus · CPC title

• G01J2001/4266

  for measuring solar light · CPC title

• G01J1/0242

  Control or determination of height or angle information of sensors or receivers; Goniophotometry · CPC title

• G01J1/0437

  using masks, aperture plates, spatial light modulators, spatial filters, e.g. reflective filters · CPC title