1. A device housing, comprising:
a plastic substrate;
a base paint layer formed on a surface of the substrate;
a vacuum coated layer formed on the base paint layer, the vacuum coated layer having a metallic appearance;
a transparent middle paint layer formed on the vacuum coated layer;
a pattern layer formed on parts of the middle paint layer; and
a transparent top paint layer formed on the surface of the pattern layer and the parts of the middle paint layer not covered by the pattern layer, the top paint layer being made of a paint having a soft tactility.
2. The device housing as claimed in claim 1, wherein the vacuum coated layer is formed by a metallic material.
3. The device housing as claimed in claim 2, wherein the metallic material is selected from a group consisting of indium, aluminum, titanium, tin, chromium, aurum, vanadium, stainless steel and indium-tin alloy.
4. The device housing as claimed in claim 1, wherein the vacuum coated layer is formed by a non-metallic material.
5. The device housing as claimed in claim 4, wherein the non-metallic material is selected from a group consisting of titanium carbide, titanium nitride, titanium oxide, and aluminum oxide.
6. The device housing as claimed in claim 1, wherein the middle paint layer is painted with a colorless paint or a colorized paint.
7. The device housing as claimed in claim 1, wherein the pattern layer is made of a colorized ink.
8. The device housing as claimed in claim 1, wherein the top paint layer is made of acrylic lacquer or polyurethane lacquer.
9. A method for making a device housing, comprising the steps of:
providing a plastic substrate;
forming a base paint layer on a surface of the substrate;
forming a vacuum coated layer on the base paint layer, the vacuum coated layer having a metallic appearance;
forming a transparent middle paint layer on the vacuum coated layer;
forming a pattern layer on part of the middle paint layer; and
forming a transparent top paint layer on the surface of the pattern layer and the parts of the middle paint layer not covered by the pattern layer, the top paint layer made of a paint having soft tactility.
10. The method for making a device housing as claimed in claim 9, wherein the vacuum coated layer is formed by vacuum evaporating or vacuum sputtering.
11. The method for making a device housing as claimed in claim 10, wherein the target for forming the vacuum coated layer is made of a metallic material.
12. The method for making a device housing as claimed in claim 11, wherein the metallic material is selected from indium, aluminum, titanium, tin, chromium, aurum, vanadium, stainless steel and indium-tin alloy.
13. The method for making a device housing as claimed in claim 9, wherein the target for forming the vacuum coated layer is made of a metallic material.
14. The method for making a device housing as claimed in claim 13, wherein the metallic material is selected from titanium carbide, titanium nitride, titanium oxide, and aluminum oxide.
15. The method for making a device housing as claimed in claim 9, wherein the middle paint layer is painted with a colorless paint or a colorized paint.
16. The method for making a device housing as claimed in claim 9, wherein the pattern layer is made of a colorized ink.
17. The method for making a device housing as claimed in claim 16, wherein the pattern layer is formed by screen printing or pad printing.
18. The method for making a device housing as claimed in claim 9, wherein the top paint layer is made of acrylic lacquer or polyurethane lacquer.
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 apparatus for determining a resistivity parameter of an earth formation, the apparatus comprising:
(a) a logging tool in a borehole in the earth formation, the logging tool having at least one measurement electrode that conveys a measure current into the earth formation;
(b) at least one guard electrode associated with the at least one measurement electrode that focuses the measure current;
(c) a shielding electrode interposed between the at least one guard electrode and the at least one measurement electrode; and
(d) circuitry that minimizes a current flow between the at least one measurement electrode and the shielding electrode.
2. The apparatus of claim 1 wherein the circuitry includes a processor that alters at least one of (i) a potential of the at least one measurement electrode, (ii) a current supplied to the at least one measurement electrode, (iii) an impedance between the at least one guard electrode and the at least one measurement electrode, and (iv) a potential of the at least one guard electrode.
3. The apparatus of claim 1 further comprising a processor that determines from the measure current and a potential of at least one of (i) the guard electrode, and (ii) the measurement electrode an apparent resistance related to the resistivity parameter.
4. The apparatus of claim 3 wherein the processor determines the apparent resistance by using a relation of the form:
\u03c1
a
=
k
\xb7
U
M
\u2062
\u2003
\u2062
G
I
M
where \u03c1\u03b1 is the apparent resistivity, k is a calibration factor, UMG is the voltage of at least one of (i) the guard, and (ii) the measurement electrode relative to a reference potential, and IM is the measure current.
5. The apparatus of claim 4 wherein the parameter of interest comprises a formation resistivity and wherein the processor further determines the formation resistivity from the apparent resistance.
6. The apparatus of claim 3 wherein the determined apparent resistance is substantially independent of at least one of (i) a standoff of the logging tool, and (ii) a resistivity of a fluid in the borehole.
7. The apparatus of claim 1 wherein there is a standoff of between about 2 mm and about 10 mm between the logging tool and a wall of the borehole.
8. The apparatus of claim 1 further comprising a conveyance device which conveys the logging tool into the borehole, the conveyance device being selected from the group consisting of (i) a drilling tubular with a bottomhole assembly carrying the logging tool, and (ii) a wireline.
9. The apparatus of claim 1 further comprising an orientation sensor that provides an output indicative of an orientation angle of the logging tool, the apparatus including a processor which produces a resistivity image of the formation using an output of the orientation sensor
10. The apparatus of claim 1 wherein a size of the at least one measurement electrode is greater than a size of the measure current at a wall of the borehole.
11. The apparatus of claim 1 wherein the at least one shielding electrode further comprises at least one second shielding electrode surrounding the at least one guard electrode.
12. The apparatus of claim 1 further comprising insulators positioned between (i) the at least one measurement electrode and the shielding electrode, and (ii) the shielding electrode and the at least one guard electrode.
13. The apparatus of claim 2 wherein the processor is at one of (i) a surface location, and, (ii) a downhole location.
14. The apparatus of claim 1 wherein the at least one measurement electrode, the shielding electrode and the at least one guard electrode comprise ring electrodes.
15. A method of determining a resistivity parameter of an earth formation, the method comprising:
(a) conveying a measure current into the earth formation using a measurement electrode on a logging tool in the earth formation;
(b) focusing the measure current using a guard electrode on the logging tool;
(c) shielding the measurement electrode from the guard electrode; and
(d) minimizing a current flow between the measurement electrode and the shielding electrode.
16. The method of claim 15 wherein minimizing the current flow further comprises at least one of (i) altering a potential of the measurement electrode, (ii) altering a current supplied to the measurement electrode, (iii) altering an impedance between the guard electrode and the measurement electrode, and (iv) altering a potential of the guard electrode.
17. The method of claim 15 further comprising determining from the measure current and a potential of at least one of (i) the guard electrode, and (ii) the measurement electrode an apparent resistance related to the resistivity parameter.
18. The method of claim 15 wherein determining the apparent resistance further comprises by using a relation of the form:
\u03c1
a
=
k
\xb7
U
MG
I
M
where \u03c1\u03b1 is the apparent resistivity, k is a calibration factor, UMG is the voltage of at least one of (i) the guard, and (ii) the measurement electrode relative to a reference potential, and IM is the measure current.
19. The method of claim 17 wherein the resistivity parameter comprises a formation resistivity determined from the apparent resistance.
20. The method of claim 17 wherein the determined apparent resistance is substantially independent of at least one of (i) a standoff of the logging tool, and (ii) a resistivity of a fluid in the borehole.
21. The method of claim 15 further comprising conveying the logging tool into the borehole on one of (i) a drilling tubular with a bottomhole assembly carrying the logging tool, and (ii) a wireline.
22. The method of claim 15 further comprising producing a resistivity image of the formation using orientation measurements.
23. A computer readable medium for use with a logging tool used in a borehole in an earth formation, the logging tool comprising:
(a) a measurement electrode which conveys a measure current into the earth formation;
(b) a guard electrode which focuses the measure current; and
(c) a shielding electrode positioned between the guard electrode and the measurement electrode, the medium comprising instructions enabling:
(d) minimizing a current flow between the measurement electrode and the shielding electrode; and
(e) determination of an apparent resistance from a potential of the guard or measurement electrode and the measure current.
24. The medium of claim 23 selected from the group consisting of: (i) a ROM, (ii) an EPROM, (iii) an EAROM, (iv) a Flash Memory, and (v) an Optical disk.