1. An azimuth measurement device comprising:
2- or 3-axis geomagnetism detection means for detecting the geomagnetism;
output data acquisition means for acquiring repeatedly a predetermined number of times or more, either the 2-axis output data at the time when the direction of the geomagnetism detection means changes while keeping the 2-axis detecting directions on a predetermined plane, or the 3-axis output data at the time when the direction of the geomagnetism detection means changes in the three-dimensional space;
offset information calculation means for determining a reference point either on 2-axis coordinate space composed of the 2-axis output data or on 3-axis coordinate space composed of the 3-axis output data thereby to estimate the coordinates of the reference point so that the dispersion of the distances from the 2- or 3-axis output data group obtained by the output data acquisition means, to the reference point may be minimized, and for calculating the offset information of the output data of the geomagnetism detection means on the basis of the coordinates of the reference point; and
reliability information calculation means for obtaining first reliability information relating to the reliability of the offset information calculated by said offset information calculation means,
wherein an acceptance threshold value at the time of calculating said offset information is gradually tightened on the basis of the first predetermined number of the recent first reliability information calculated by said reliability information calculation means.
2. An azimuth measurement device according to claim 1, further comprising reliability information calculation means for obtaining second reliability information relating to the reliability of the offset information from the output data acquired latest, wherein an acceptance threshold value at the time of calculating said offset information is loosened, in case the reliability deteriorates, on the basis of second reliability information of the recent second predetermined number calculated by said reliability information calculation means.
3. An azimuth measurement device according to claim 2,
wherein said second reliability information is the distance from the 2- or 3-axis output data obtained by said output data acquisition means, to the reference point.
4. An azimuth measurement device according to claim 2,
wherein said second reliability information is calculated from a geomagnetic inclination angle information calculated from the 3-axis output data obtained by said output data acquisition means.
5. An azimuth measurement device according to claim 2, further comprising first and second external output means for outputting said first and second pieces of reliability information to the outside.
6. An azimuth measurement device according to claim 2,
wherein not only the acceptance threshold value at the time of calculating said offset information but also the data measurement conditions andor the offset information calculation conditions are changed.
7. An azimuth measurement device according to claim 6,
wherein said second reliability information is the distance from the 2- or 3-axis output data obtained by said output data acquisition means, to the reference point.
8. An azimuth measurement device according to claim 6,
wherein said second reliability information is calculated from a geomagnetic inclination angle information calculated from the 3-axis output data obtained by said output data acquisition means.
9. An azimuth measurement device according to claim 6,
wherein said data measurement condition value andor said offset information calculation condition contains a measurement time interval.
10. An azimuth measurement device according to claim 6,
wherein said data measurement condition value andor said offset information calculation condition contains number of data for calculating the offset information.
11. An azimuth measurement device according to claim 6,
wherein said data measurement condition value andor said offset information calculation condition contains said first andor second predetermined number.
12. An azimuth measurement device according to claim 6, further comprising: reliability information calculation means for obtaining third reliability information from said data measurement condition value andor said offset information calculation condition; and third external output means for outputting said third reliability information from said reliability information calculation means.
13. An azimuth measurement device according to claim 1,
wherein said first reliability information is calculated from the dispersion of the recent reference point.
14. An azimuth measurement device according to claim 1,
wherein said first reliability information is calculated from the dispersion of the data of said closes 2- or 3-axis output data group.
15. An azimuth measurement device according to claim 1, further comprising detection means for detecting a specific event, wherein the acceptance threshold value at the time of calculating the offset information in case said event occurs are changed.
16. An azimuth measurement device according to claim 15,
wherein said specific event is a specific operation by an operator.
17. An azimuth measurement device comprising:
3-axis geomagnetism detection means for detecting the geomagnetism;
output data acquisition means for acquiring the 3-axis output data at the time when the direction of said geomagnetism detection means changes in the three-dimensional space, repeatedly a predetermined number of times or more;
offset information calculation means for determining a reference point on three-dimensional coordinates composed of said 3-axis output data, to estimate the coordinates of the reference point from the 3-axis output data group obtained by said output data acquisition means, and for calculating the offset information for the output data of said geomagnetism detection means on the basis of the coordinates of said reference point; and
reliability information calculation means for obtaining second reliability information relating to the reliability of the offset information from the output data obtained latest by said output data acquisition means,
wherein the second reliability information calculated by said reliability information calculation means is calculated from both the geomagnetic inclination angle information expected with the premise that the azimuth measurement device is horizontally held and the geomagnetic inclination angle information calculated from the output data acquired latest by said output data acquisition means.
18. An azimuth measurement device comprising:
2- or 3-axis geomagnetism detection means for detecting the geomagnetism;
output data acquisition means for acquiring several times or more, either the 2-axis output data at the time when the direction of said geomagnetism detection means changes while keeping said 2-axis detecting directions on a predetermined plane or the 3-axis output data at the time when the direction of said geomagnetism detection means changes in the three-dimensional space;
offset information calculation means for estimating the coordinates of the reference point so that the dispersion of the distances from selected 2- or 3-axis output data group to the reference point may be minimized; said reference point estimation means also selecting said 2- or 3-axis output data on the basis of predetermined measurement parameters, and also determining a reference point either on the two-dimensional coordinate composed of said selected 2-axis output data or on the three-dimensional coordinates composed of said selected 3-axis output data, and for calculating the offset information for the output data of said geomagnetism detection means on the basis of a plurality of estimated reference points;
azimuth calculation means for calculating an azimuth from said output data and said offset information; and
reliability information calculation means for calculating the second reliability information of said offset information according to calculation parameters for calculating the reliability information of predetermined offset information, on the basis of at least one of said 2- or 3-axis output data group and said plural reference points.
19. An azimuth measurement device according to claim 18,
wherein said offset information calculation means compares said reliability information with an acceptance threshold value to evaluate whether or not said reliability information is to be adopted as the offset information to be used for the calculation of the azimuth by said azimuth calculation means.
20. An azimuth measurement device according to claim 19,
wherein said acceptance threshold value is changed more strictly as said offset information is adopted a predetermined number of times.
21. An azimuth measurement device according to claim 19, further comprising a detection section for detecting the magnetic environment inside and outside of the azimuth measurement device and the change in said magnetic environment,
wherein said acceptance threshold value is loosened in case said detection section detects that said magnetic environment has changed.
22. An azimuth measurement device according to claim 21,
wherein said detection section detects that the magnetic environment has changed, in case the data acquired by said output data acquisition means exceeds a predetermined range.
23. An azimuth measurement device according to claim 19, further comprising:
event detection means for detecting either the change in the environment of the azimuth measurement device or the operation of the operator,
wherein said acceptance threshold value is changed in case said event occurs.
24. An azimuth measurement device according to claim 23,
wherein said environment change is a temperature change.
25. An azimuth measurement device according to claim 19,
wherein at least one of said measurement parameters and said calculation parameters are changed, when said acceptance threshold value is changed.
26. An azimuth measurement device according to claim 19,
wherein the reliability information of said offset information contains the information calculated from the dispersion of the plural reference points.
27. An azimuth measurement device according to claim 19,
wherein the reliability information of said offset information contains the information calculated from the dispersion of the data composing said 2- or 3-axis output data group.
28. An azimuth measurement device according to claim 19,
wherein the reliability information of said offset information contains the distance from the 2- or 3-axis output data obtained by said output data acquisition means, to the reference point.
29. An azimuth measurement device according to claim 19,
wherein said measurement parameters contain a measurement interval.
30. An azimuth measurement device according to claim 19,
wherein said measurement parameters contain the variation in data,
wherein said variation is the difference between the output data acquired by said output data acquisition means and the data selected by said offset information calculation means for estimating said reference point, and
wherein said offset information calculation means selects the data, of which said variation is at a predetermined value or higher.
31. An azimuth measurement device according to claim 19,
wherein said measurement parameters contain the number of data for said offset information calculation means to estimate the coordinates of the reference point.
32. An azimuth measurement device according to claim 19,
wherein said calculation parameters contain the number of reference points for calculating the dispersion of said reference points.
33. An azimuth measurement device according to claim 19, further comprising output means for outputting at least one of said acceptance threshold value, said measurement parameters and said calculation parameters to the outside.
34. An azimuth measurement device according to claim 19,
wherein said geomagnetism detection means acquires 3-axis output data and calculates geomagnetic inclination angle information from said output data, and
wherein second reliability information is calculated from the value of said geomagnetic inclination angle information.
35. An azimuth measurement method comprising:
the step of acquiring, by using 2- or 3-axis geomagnetism detection means for detecting the geomagnetism, either the 2-axis output data at the time when the direction of said geomagnetism detection means changes or the 3-axis output data at the time when the direction of said geomagnetism detection means changes in the three-dimensional space, a plurality of times or more while keeping said 2-axis detecting directions on a predetermined plane;
the step of selecting said 2- or 3-axis output data on the basis of predetermined measurement parameters;
the step of determining a reference point either on the two-dimensional coordinate composed of said selected 2-axis output data or on the three-dimensional coordinates composed of said selected 3-axis output data, thereby to estimate the coordinates of the reference point so that the dispersion of the distances from said selected 2- or 3-axis output data group to the reference point may be minimized;
the step of calculating the offset information for the output data of said geomagnetism detection means on the basis of said plural reference points estimated;
the step of calculating an azimuth from said output data and said offset information; and
the step of calculating the second reliability information of said offset information according to, calculation parameters for calculating the reliability information of predetermined offset information, on the basis of at least one of said 2- or 3-axis output data group and said plural reference points.
36. An azimuth measurement method according to claim 35,
wherein said offset information calculation step compares said reliability information with an acceptance threshold value to evaluate whether or not said reliability information is to be adopted as the offset information to be used for the calculation of the azimuth.
37. An azimuth measurement method according to claim 36,
wherein said acceptance threshold value is changed more strictly as said offset information is adopted a predetermined number of times.
38. An azimuth measurement method according to claim 36, further comprising:
the step of detecting that the magnetic environment inside and outside of the azimuth measurement device has changed after the step of acquiring said output data plural times; and
the step of loosening said acceptance threshold value in case it is detected that said magnetic environment has changed.
39. An azimuth measurement method according to claim 38,
wherein said detection step detects that the magnetic environment has changed, in case the data acquired exceeds a predetermined range.
40. An azimuth measurement method according to claim 36, further comprising:
the step of detecting either the change in the environment of the azimuth measurement device or the operation of the operator; and
the step of changing said acceptance threshold value in case said event occurs.
41. An azimuth measurement method according to claim 40,
wherein said environment change is a temperature change.
42. An azimuth measurement method according to claim 36,
wherein said acceptance threshold value is changed, and
wherein at least one of said measurement parameters and said calculation parameters are changed.
43. An azimuth measurement method according to claim 36,
wherein the reliability information of said offset information contains the information calculated from the dispersion of the plural reference points.
44. An azimuth measurement method according to claim 36,
wherein the reliability information of said offset information contains the information calculated from the dispersion of the data composing said 2- or 3-axis output data group.
45. An azimuth measurement method according to claim 36,
wherein the reliability information of said offset information contains the distance from the 2- or 3-axis output data obtained by said output data acquisition means, to the reference point.
46. An azimuth measurement method according to claim 36,
wherein said measurement parameters contain a measurement interval.
47. An azimuth measurement method according to claim 36,
wherein said measurement parameters contain the change in data,
wherein said change is the difference between the output data acquired by said output data acquisition means and the data selected by said reference point estimation means, and
wherein said reference point estimation means selects the data, of which said change is at a predetermined value or higher.
48. An azimuth measurement method according to claim 36,
wherein said measurement parameters contain the number of data for estimating the coordinates of the reference point.
49. An azimuth measurement method according to claim 36,
wherein said calculation parameters contain the number of reference points for calculating the dispersion of said reference points.
50. An azimuth measurement method according to claim 36, further comprising the step of outputting at least one of said acceptance threshold value, said measurement parameters and said calculation parameters to the outside.
51. An azimuth measurement method according to claim 36,
wherein said geomagnetism detection step acquires 3-axis output data, further comprising:
the step of calculating geomagnetic inclination angle information from said output data after the step of acquiring said output data plural times; and
the step of calculating second reliability information from the value of said geomagnetic inclination angle information.
52. An azimuth measurement device comprising:
a geomagnetism detector for detecting a geomagnetism;
an output data element for acquiring repeatedly a predetermined number of times or more output data from the geomagnetism detector at a time when the direction of the geomagnetism detector changes;
a reference point estimator for, determining a reference point either on a coordinate space composed of the output data thereby to estimate the coordinates of the reference point by a statistical method so that the dispersion of the distances from the output data group obtained by the output data element, to the reference point may be minimized;
an offset information calculator for calculating offset information of the output data of the geomagnetism detector on the basis of the coordinates of the reference point calculated by the reference point estimator; and
a first reliability information calculator for calculating reliability information relating to the reliability of the offset information calculated by said offset information calculator,
wherein an acceptance threshold value at the time of calculating said offset information is gradually tightened on the basis of the first predetermined number of the recent first reliability information calculated by said first reliability information calculator.
53. An azimuth measurement device according to claim 52, further comprising second reliability information calculator for relating to the reliability of the offset information from the output data acquired latest, wherein an acceptance threshold value at the time of calculating said offset information is loosened, in case the reliability deteriorates, on the basis of second reliability information of the recent second predetermined number calculated by said second reliability information calculator.
54. An azimuth measurement device according to claim 53,
wherein said second reliability; information is the distance from the output data obtained by said output data element, to the reference point.
55. An azimuth measurement device according to claim 53,
wherein said second reliability information is calculated from a geomagnetic inclination angle information calculated from the output data obtained by said output data element.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An image rendering apparatus comprising:\u2014
an image data unit for obtaining volumetric image data representative of a three-dimensional region;
a rendering unit configured to perform a rendering process on the volumetric image data that includes a sampling process that comprises, for each of a plurality of sampling paths, determining a respective color or grayscale value for a corresponding pixel based on a plurality of sampled points along the sampling path, wherein:\u2014
for each sampling path, the sampling process performed by the rendering unit comprises for each of at least some of the sampled points:\u2014calculating a significance factor for the sampled point based on at least accumulated opacity along the sampling path for the sampled point;
selecting for the sampled point one of a plurality of rendering calculation processes in dependence on the calculated significance factor; and
performing the selected rendering calculation process to obtain at least one image data value for the sampled point; and wherein
for each sampling path the rendering unit is configured to determine the color or grayscale value for the corresponding pixel based on the determined image data values for the plurality of sampled points for the path.
2. An image rendering apparatus according to claim 1, wherein for each of the sampling paths, and for said each of at least some of the sampled points, the calculating of the significance factor for the sampled point is based on accumulated opacity along the sampling path for the sampled point and opacity at the sampled point.
3. An image rendering apparatus according to claim 1, wherein the plurality of rendering calculation processes comprise a first rendering calculation process and a second rendering calculation process, wherein the second rendering calculation process is at least one of less complex, less time consuming, requires less processing power, or requires less memory than the first rendering calculation process.
4. An image rendering apparatus according to claim 3, wherein, for at least some of the sampling paths, the rendering unit is configured to select the first rendering calculation process for at least some of the sampled points and to select the second rendering calculation process for at least some other of the sampled points.
5. An medical image rendering apparatus according to claim 3, wherein the second rendering calculation process at least one of omits a calculation that is included in the first rendering calculation process or includes a simplified version of the calculation that is included in the first rendering calculation process.
6. An image rendering apparatus according to claim 5, wherein the calculation of the first rendering calculating process that is omitted or simplified in the second rendering calculation process comprises at least one of:\u2014
a pre-integration calculation;
a lighting calculation;
a shading calculation;
a segmentation interpolation calculation;
an object-to-object blending calculation;
an irradiance calculation of a global illumination algorithm;
a shadow ray calculation;
an ambient occlusion calculation.
7. An image rendering apparatus according to claim 5, wherein the calculation of the first rendering calculating process that is omitted or simplified in the second rendering calculation process comprises a lighting calculation that includes calculation of a normal to a sampled point and determining light level based on the normal to the sampled point, and the second calculation process omits the calculation of the normal to the sampled point in determining light level.
8. An image rendering apparatus according to claim 7, wherein for the second calculation process the lighting calculation comprises determining light level for a sampled point based on at least one of ambient light level, a proportion of diffuse light, or a proportion of specular light.
9. An image rendering apparatus according to claim 3, wherein, for volumetric image data and a sampling path that comprises, for increasing distance from a source of the sampling path, sampled points corresponding to one of air or vacuum, followed by sampled points corresponding to anatomy of a patient or other subject, the selecting of one of the plurality of rendering calculation processes by the rendering unit comprises:\u2014
selecting the second rendering calculation process for substantially all of the sampled points that correspond to one of air or vacuum;
selecting the first rendering calculation process for at least some of a sub-set of the sampled points corresponding to anatomy of the patient or other subject;
selecting the second rendering calculation process for substantially all of a further sub-set of the sampled points corresponding to anatomy of the patient or other subject,
wherein the further sub-set of sampled points are further from the source of the sampling path than the first sub-set of sampled points.
10. An image rendering apparatus according to claim 1, wherein the rendering unit is configured, for each of at least some of the sampled points, to compare the significance factor for the sampled point to a threshold and to perform the selecting of one of the plurality of the rendering calculation processes in dependence on the outcome of the comparison.
11. An image rendering apparatus according to claim 1, wherein the determined image data values for the plurality of sampled points comprise color or grayscale values and, for each sampling path, the color or grayscale value for the corresponding pixel is determined by the rendering unit based on the color or grayscale value for each sampled point of the sampling path, the opacity for each sampled point, and the accumulated opacity for each sampled point.
12. An image rendering apparatus according to claim 1, wherein the rendering process comprises a ray casting process, and the sampling paths comprise ray paths.
13. An image rendering apparatus according to claim 1, wherein the rendering process comprises a shear warp rendering process and the sampling paths pass through a sheared volume.
14. An image rendering apparatus according to claim 1, wherein for each sampling path the sampling process comprises, for each of the at least some of the sampled points, determining a respective opacity value for the sampled point and the a respective accumulated opacity value for the sampled point.
15. An image rendering apparatus according to claim 14, wherein determining an opacity value for the sampled point comprises determining an intensity value for the sampled point and at least one of: determining the opacity value from the intensity value in accordance with a transfer function, determining the opacity value from the intensity value in accordance with a classifier.
16. An image rendering apparatus according to claim 14, wherein determining an accumulated opacity value for a sampled point comprises determining the accumulated opacity value for the sampled point from the opacities of a plurality of previous sampled points on the sampling path.
17. An image rendering apparatus according to claim 1, wherein the volumetric image data comprises opacity values and at least one of color or grayscale values for positions in the three-dimensional region.
18. An image rendering apparatus according to claim 2, wherein the volumetric image data comprises intensity values, the rendering unit is configured to obtain converted volumetric image data by converting the intensity values to opacity values and at least one of color or grayscale values for positions in the three-dimensional region, and the determining of a respective opacity for a sampled point and a respective accumulated opacity for a sampled point comprises determining the respective opacity value and accumulated opacity value from the converted volumetric image data.
19. An image rendering apparatus according to claim 18, wherein the converting of the intensity values comprises at least one of converting the intensity values in accordance with a transfer function, converting the intensity values in accordance with a classifier.
20. An image rendering apparatus according to claim 18, wherein the rendering unit is configured to one of:\u2014
convert the intensity values as part of the sampling process;
convert the intensity values in a pre-conversion process before the sampling process.
21. An image rendering apparatus according to claim 1, wherein one of:\u2014
the volumetric image data is comprises at least one of CT data, MRI data, PET data;
the volumetric image data is obtained from at least one of CT data, MRI data, PET data.
22. An image rendering apparatus according to claim 1, wherein the significance factor is representative of a significance of the sampled point to the color or grayscale value for the corresponding pixel.
23. An image rendering apparatus comprising a display unit configured to display a rendered image using the determined pixel color or grayscale values.
24. A method of rendering comprising:\u2014
obtaining volumetric image data representative of a three-dimensional region;
performing a rendering process on the volumetric image data that includes a sampling process that comprises, for each of a plurality of sampling paths, determining a respective color or grayscale value for a corresponding pixel based on a plurality of sampled points along the sampling path, wherein:\u2014
for each sampling path, the sampling process performed by the rendering unit comprises for each of at least some of the sampled points:\u2014calculating a significance factor for the sampled point based on at least accumulated opacity along the sampling path for the sampled point;
selecting for the sampled point one of a plurality of rendering calculation processes in dependence on the calculated significance factor; and
performing the selected rendering calculation process to obtain at least one image data value for the sampled point;
for each sampling path determining the color or grayscale value for the corresponding pixel based on the determined image data values for the plurality of sampled points for the path; and
displaying a rendered image using the determined pixel color or grayscale values.
25. A computer program product comprising a non-transitory storage medium storing instructions that are executable to perform a method according to claim 24.