Optical-band visibility for touch-sensor mesh designs
In one embodiment, an apparatus includes a touch sensor that includes a mesh of conductive material configured to extend across a display. The mesh includes first lines of conductive material that are substantially parallel to each other and second lines of conductive material that are substantially parallel to each other. The first lines extend across the display at a first angle relative to a first axis, and the second lines extend across the display at a second angle relative to the first axis. First lines that are adjacent to each other are separated from each other along the first axis by a first separation distance, and second lines that are adjacent to each other are separated from each other along the first axis by a second separation distance.
1. An apparatus that comprises:
a touch sensor that comprises a mesh of conductive material configured to extend across a display, wherein:
the mesh comprises first lines of conductive material that are substantially parallel to each other and second lines of conductive material that are substantially parallel to each other;
the first lines extend across the display at a first angle relative to a first axis;
the second lines extend across the display at a second angle relative to the first axis;
first lines that are adjacent to each other are separated from each other along the first axis by a first separation distance;
second lines that are adjacent to each other are separated from each other along the first axis by a second separation distance;
the first and second angles of the first and second lines and the first and second separation distances of adjacent ones of the first and second lines collectively form optical bands with respect to the display that have an optical-band visibility that is a product of an optical-band contrast function and an optical-band frequency function;
the optical-band contrast function is
I
max
-
I
min
I
max
+
I
min
,
wherein I max is a maximum optical-band intensity and I min is a minimum optical-band intensity;
the optical-band frequency function is
1
1
+
(
f
/
K
)
n
,
wherein f is an optical-band frequency of the optical bands, K is a constant, and n is a constant; and
the optical-band visibility of the optical bands is less than or equal to 0.11; and
one or more computer-readable non-transitory storage media coupled to the touch sensor and embodying logic that is configured when executed to control the touch sensor.
2. The apparatus of claim 1 , wherein:
f has units of cycles per millimeter;
K is 3 cycles per millimeter;
n is 2; and
the optical-band frequency function is
1
1
+
(
f
/
3
)
2
.
3. The apparatus of claim 1 , wherein the optical-band frequency of the optical bands is greater than or equal to 2 cycles per millimeter.
4. The apparatus of claim 1 , wherein the optical-band frequency of the optical bands is a lowest frequency of two or more optical-band frequencies associated with the optical bands.
5. The apparatus of claim 1 , wherein the optical-band contrast function for the optical bands has a value less than or equal to 0.16.
6. The apparatus of claim 1 , wherein the optical-band frequency function for the optical bands has a value less than or equal to 0.7.
7. The apparatus of claim 1 , wherein:
the display comprises a plurality of pixels, wherein:
each of the pixels has a first pixel pitch (PP x ) along the first axis and a second pixel pitch (PP y ) along a second axis that is substantially perpendicular to the first axis;
the first pixel pitch is a distance between corresponding features of two adjacent pixels along the first axis; and
the second pixel pitch is a distance between corresponding features of two adjacent pixels along the second axis;
the first angle is within 1° of the arctangent of
[
3
m
×
PP
y
PP
x
]
,
wherein m is an integer; and
the second angle is within 1° of the arctangent of
[
3
n
×
PP
y
PP
x
]
,
wherein n is an integer.
8. The apparatus of claim 7 , wherein:
the first pixel pitch is approximately equal to the second pixel pitch;
m is equal to 5;
the first angle is within 1° of 30.96°;
n is equal to 2; and
the second angle is within 1° of 56.31°.
9. The apparatus of claim 7 , wherein:
the first pixel pitch is approximately equal to the second pixel pitch;
m is equal to 4;
the first angle is within 1° of 36.87°;
n is equal to 2; and
the second angle is within 1° of 56.31°.
10. The apparatus of claim 1 , wherein:
the display comprises a plurality of pixels, wherein each of the pixels has a first pixel pitch (PP x ) along the first axis, the first pixel pitch being a distance between corresponding features of two adjacent pixels along the first axis;
the first separation distance is within 1% of
(
p
3
×
q
×
PP
x
)
,
wherein p and q are integers; and
the second separation distance is within 1% of
(
r
3
×
s
×
PP
x
)
,
wherein r and s are integers.
11. The apparatus of claim 10 , wherein:
p is equal to 12;
q is equal to 1;
the first separation distance is within 1% of 4×PP x ;
r is equal to 10;
s is equal to 1; and
the second separation distance is within 1% of
10
3
×
PP
x
.
12. The apparatus of claim 10 , wherein:
p is equal to 9;
q is equal to 1;
the first separation distance is within 1% of 3×PP x ;
r is equal to 14;
s is equal to 3; and
the second separation distance is within 1% of
14
9
×
PP
x
.
13. The apparatus of claim 10 , wherein:
p is equal to 31;
q is equal to 2;
the first separation distance is within 1% of
31
6
×
PP
x
;
r is equal to 17;
s is equal to 2; and
the second separation distance is within 1% of
17
6
×
PP
x
.
14. The apparatus of claim 10 , wherein:
p is equal to 41;
q is equal to 6;
the first separation distance is within 1% of
41
18
×
PP
x
;
r is equal to 14;
s is equal to 3; and
the second separation distance is within 1% of
14
9
×
PP
x
.
15. The apparatus of claim 1 , wherein the first and second lines of conductive material each have a width between approximately 2.5 μm and 3.5 μm.
16. The apparatus of claim 1 , wherein the first and second lines of conductive material each have a width between approximately 4.5 μm and 5.5 μm.
17. The apparatus of claim 1 , wherein the first and second lines of conductive material form a plurality of mesh cells, each mesh cell having a diagonal length of approximately 265 μm to 340 μm.
18. A touch sensor that comprises:
a mesh of conductive material configured to extend across a display, wherein:
the mesh comprises first lines of conductive material that are substantially parallel to each other and second lines of conductive material that are substantially parallel to each other;
the first lines extend across the display at a first angle relative to a first axis;
the second lines extend across the display at a second angle relative to the first axis;
first lines that are adjacent to each other are separated from each other along the first axis by a first separation distance;
second lines that are adjacent to each other are separated from each other along the first axis by a second separation distance;
the first and second angles of the first and second lines and the first and second separation distances of adjacent ones of the first and second lines collectively form optical bands with respect to the display that have an optical-band visibility that is a product of an optical-band contrast function and an optical-band frequency function;
the optical-band contrast function is
I
max
-
I
min
I
max
+
I
min
,
wherein I max is a maximum optical-band intensity and I min is a minimum optical-band intensity;
the optical-band frequency function is
1
1
+
(
f
/
K
)
n
,
wherein f is an optical-band frequency of the optical bands, K is a constant, and n is a constant; and
the optical-band visibility of the optical bands is less than or equal to 0.11.
19. The touch sensor of claim 18 , wherein the optical-band frequency of the optical bands is greater than or equal to 2 cycles per millimeter.
20. A method comprising:
depositing on a substrate a mesh of conductive material configured to extend across a display, wherein:
the mesh comprises first lines of conductive material that are substantially parallel to each other and second lines of conductive material that are substantially parallel to each other;
the first lines extend across the display at a first angle relative to a first axis;
the second lines extend across the display at a second angle relative to the first axis;
first lines that are adjacent to each other are separated from each other along the first axis by a first separation distance;
second lines that are adjacent to each other are separated from each other along the first axis by a second separation distance;
the first and second angles of the first and second lines and the first and second separation distances of adjacent ones of the first and second lines collectively form optical bands with respect to the display that have an optical-band visibility that is a product of an optical-band contrast function and an optical-band frequency function;
the optical-band contrast function is
I
max
-
I
min
I
max
+
I
min
,
wherein I max is a maximum optical-band intensity and I min is a minimum optical-band intensity;
the optical-band frequency function is
1
1
+
(
f
/
K
)
n
,
wherein d is an optical-Dana frequency of the optical bands, K is a constant, and n is a constant; and
the optical-band visibility of the optical bands is less than or equal to 0.11; and
forming one or more electrodes of a touch sensor from the mesh of conductive material.