MEMS actuator mounted camera module having sag compensation and sag compensation method using the same
View Patent ↗The present invention relates to a micro-electromechanical (MEMS) actuator mounted camera module having sag compensation and a sag compensation method using the same, the camera module including a MEMS actuator mounted with a lens; a MEMS actuator moving unit outputting electrostatic capacity information corresponding to position of the lens changed by displacement move and outputting a displacement move signal to the MEMS actuator for controlling the displacement moving force; a memory unit stored with reference signal information corresponding to a maximum displacement move in the displacement move; and a signal compensation unit calculating a step range corresponding to the displacement move of the MEMS actuator based on the electrostatic capacity information outputted from the MEMS actuator moving unit and the reference signal information stored in the memory unit and compensating the displacement moving force of the MEMS actuator based on the calculated step range.
1. A micro-electromechanical (MEMS) actuator mounted camera module having sag compensation, the camera module comprising:
a MEMS actuator mounted with a lens and configured to output a displacement moving force for a displacement drive of the lens based on an electrostatic force for adjustment of a focal distance between the lens and an image sensor;
a MEMS actuator moving unit configured to output electrostatic capacity information corresponding to a position of the lens changed by a displacement move and configured to output a displacement move signal to the MEMS actuator to control the displacement moving force;
a memory unit that stores reference signal information corresponding to a maximum displacement move in the displacement move; and
a signal compensation unit configured to calculate a step range corresponding to the displacement move of the MEMS actuator based on the electrostatic capacity information outputted from the MEMS actuator moving unit and the reference signal information stored in the memory unit and configured to compensate the displacement moving force of the MEMS actuator based on the calculated step range,
wherein the electrostatic capacity information outputted from the MEMS actuator moving unit includes minimum electrostatic capacity information and maximum electrostatic capacity information based on a sag in a shooting direction of the image sensor.
2. The camera module of claim 1 , wherein the calculated step range includes a start code in response to the minimum electrostatic capacity information, and a code step range in a stop code corresponding to the maximum electrostatic capacity information.
3. The camera module of claim 2 , wherein the reference signal information is maximum voltage information corresponding to the maximum displacement move.
4. The camera module of claim 2 , wherein a minimum displacement move signal corresponding to the start code is calculated by the following Equation:
V
min
=
start
code
number
of
entire
step
codes
×
V
ref
where, Vmin is an actual minimum displacement move signal, Vref is a reference signal having maximum voltage information, number of entire step codes is a number of entire codes in the code step range, and the start code is a code from which an electrostatic capacity change starts.
5. The camera module of claim 2 , wherein a maximum displacement move signal corresponding to the stop code is calculated by the following Equation:
V
max
=
stop
code
number
of
entire
step
codes
×
V
ref
where, Vmax is a maximum displacement move signal, Vref is a reference signal having maximum voltage information, number of entire step codes is a number of entire codes in the code step range, and the stop code is a code from which an electrostatic capacity change ends.
6. The camera module of claim 2 , wherein an n step displacement move signal corresponding to n steps in the compensated displacement move signal can be calculated by the following Equation:
V
out
=
(
number
of
n
step
code
number
of
entire
step
codes
×
(
stop
code
-
start
code
)
+
start
code
)
×
V
ref
number
of
entire
step
codes
where, Vout is the n step displacement move signal, Vref is a reference signal having reference signal information, number of entire step codes is a number of entire codes in the code step range, the start code is a code where an electrostatic capacity change starts, and the stop code is a code from which the electrostatic capacity change ends.
7. The camera module of claim 1 , wherein the sag is generated by gravity as a base, the gravity acting on the lens or the MEMS actuator in the shooting direction.
8. The camera module of claim 1 , wherein the memory unit includes a non-volatile memory.
9. A sag compensation method using a MEMS actuator mounted camera module having sag compensation, the method comprising:
outputting,by a MEMS actuator moving unit, a displacement moving signal for a displacement move of a lens that faces a shooting direction;
receiving, by the MEMS actuator moving unit, the displacement moving signal to output a displacement moving force to the lens based on an electrostatic force;
outputting, by the MEMS actuator moving unit, minimum electrostatic capacity information and maximum electrostatic capacity information caused by a sag based on the displacement move;
calculating, by a signal compensation unit, a step range for adjustment of a focal distance, based on reference signal information corresponding to a maximum displacement move in the displacement move, the minimum electrostatic capacity information and the maximum electrostatic capacity information; and
compensating, by the signal compensation unit, the displacement moving signal based on the step range.
10. The sag compensation method of claim 9 , further comprising receiving, by the MEMS actuator moving unit, an initialization signal which is a moving signal, from a pre-set entire step range from a user, prior to the outputting of the displacement moving signal by the MEMS actuator moving unit.
11. The sag compensation method of claim 9 , further comprising displacement-moving, by the lens, from a minimum focal distance position to a maximum focal distance position in relation to an image sensor, or from the maximum focal distance position to the minimum focal distance position in relation to the image sensor, between the outputting of the displacement moving force by the MEMS actuator moving unit and the outputting of the electrostatic capacity information by the MEMS actuator moving unit.
12. The sag compensation method of claim 9 , wherein the calculating of the step range by the signal compensation unit includes calculating, by the signal compensation unit, a start code corresponding to the minimum electrostatic capacity information, and a code step range based on a stop code corresponding to the maximum electrostatic capacity information.
13. The sag compensation method of claim 12 , wherein a minimum displacement move signal corresponding to the start code is calculated by the following Equation:
V
min
=
start
code
number
of
entire
step
codes
×
V
ref
where, Vmin is an actual minimum displacement move signal, Vref is a reference signal having maximum voltage information, number of entire step codes is a number of entire codes in the code step range, and the start code is a code from which an electrostatic capacity change starts.
14. The sag compensation method of claim 12 , wherein a maximum displacement move signal corresponding to the stop code is calculated by the following Equation:
V
max
=
stop
code
number
of
entire
step
codes
×
V
ref
where, Vmax is a maximum displacement move signal, Vref is a reference signal having maximum voltage information, number of entire step codes is a number of entire codes in the code step range, and the stop code is a code from which an electrostatic capacity change ends.
15. The sag compensation method of claim 12 , wherein an n step displacement move signal corresponding to n steps in the compensated displacement move signal can be calculated by the following Equation:
V
out
-
(
number
of
n
step
code
number
of
entire
step
codes
×
(
stop
code
-
start
code
)
+
start
code
)
×
V
ref
number
of
entire
step
codes
where, Vout is the n step displacement move signal, Vref is a reference signal having reference signal information, number of entire step codes is a number of entire codes in the code step range, the start code is a code where electrostatic capacity change starts, and the stop code is a code from which electrostatic capacity change ends.
16. A micro-electromechanical (MEMS) actuator mounted camera module having sag compensation, the camera module comprising:
a MEMS actuator mounted with a lens and configured to adjust a focal distance between the lens and an image sensor through a displacement move;
a MEMS actuator moving unit configured to output minimum and maximum electrostatic capacity information caused by a sag that is generated by gravity as a base, the gravity acting on any one of the lens and the MEMS actuator corresponding to a position of the lens from a shooting direction of the image sensor, and configured to control the displacement move;
a memory unit that stores reference signal information provided as maximum voltage information corresponding to a maximum displacement move in the displacement move; and
a signal compensation unit configured to output a displacement move compensation signal to the MEMS actuator moving unit based on a step range by calculating the step range corresponding to the displacement move of the MEMS actuator based on the electrostatic capacity information outputted from the MEMS actuator moving unit and the reference signal information stored in the memory unit.
17. The camera module of claim 16 , wherein the calculated step range includes a start code in response to the minimum electrostatic capacity information, and a code step range in a stop code corresponding to the maximum electrostatic capacity information.
18. The camera module of claim 17 , wherein a minimum displacement move signal corresponding to the start code is calculated by the following Equation:
V
min
=
start
code
number
of
entire
step
codes
×
V
ref
where, Vmin is an actual minimum displacement move signal, Vref is a reference signal having maximum voltage information, number of entire step codes is a number of entire codes in the code step range, and the start code is a code from which an electrostatic capacity change starts.
19. The camera module of claim 17 , wherein a maximum displacement move signal corresponding to the stop code is calculated by the following Equation:
V
max
=
stop
code
number
of
entire
step
codes
×
V
ref
where, Vmax is a maximum displacement move signal, Vref is a reference signal having maximum voltage information, number of entire step codes is a number of entire codes in the code step range, and the stop code is a code from which an electrostatic capacity change ends.
20. The camera module of claim 17 , wherein an n step displacement move signal corresponding to n steps in the compensated displacement move signal can be calculated by the following Equation:
V
out
-
(
number
of
n
step
code
number
of
entire
step
codes
×
(
stop
code
-
start
code
)
+
start
code
)
×
V
ref
number
of
entire
step
codes
where, Vout is an n step displacement move signal, Vref is a reference signal having reference signal information, number of entire step codes is a number of entire codes in the code step range, the start code is a code where an electrostatic capacity change starts, and the stop code is a code from which the electrostatic capacity change ends.