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Digital Camera Patent Abstract
A digital camera module (100) for a portable electronic device,
includes a lens holder (20), a lens module (10) axially movably
received in the lens holder and at least one position tracking device
(30). Each position tracking device includes a resistor (33) secured
to the holder, a probe (31) attached to the lens module and slidably
contacting with the resistor, and a measuring unit (35) electrically
connecting with the resistor and the probe therebetween in series
for measuring a resistance value of the resistor as it changes with
the movement of the lens module thus enabling it to detect the position
of the lens module.
Digital Camera Patent Claims
1. A digital camera module comprising: a lens holder; a lens module
axially movably received in the lens holder; and at least one position
tracking device, each position tracking device comprising: a resistor
secured to the lens holder; a probe attached to the lens module
and slidably contacting with the resistor; a measuring unit electrically
connecting with the resistor and the probe therebetween in series
for measuring a resistance value of the resistor as it changes with
the movement of the lens module thus enabling it to detect the position
of the lens module.
2. The digital camera module as claimed in claim 1, wherein the
lens module comprises a barrel and at least one lens received in
the barrel, the barrel has at least one groove defined in a peripheral
surface thereof, each groove respectively receiving a corresponding
probe therein.
3. The digital camera module as claimed in claim 1, wherein the
lens holder is a hollow cylinder in shape, and has at least one
slot defined on an inner peripheral surface thereof, each slot respectively
receiving a corresponding resistor therein.
4. The digital camera module as claimed in claim 2, wherein the
probe comprises a pin projecting therefrom, the pin contacts with
the resistor.
5. The digital camera module as claimed in claim 1, wherein each
probe contacts with a resistor at a contacting position, each contacting
position changes in response to the movement of the lens module.
6. The digital camera module as claimed in claim 5, wherein each
measuring unit electrically connects with an end of a corresponding
resistor, and measures the resistance value of the corresponding
resistor between the contacting position and the end.
7. The digital camera module as claimed in claim 1, wherein each
measuring unit outputs a signal corresponding to the resistance
value.
8. The digital camera module as claimed in claim 7, wherein the
digital camera module further comprises a controlling unit electrically
connecting with each measuring unit, the controlling unit receives
the signal with the resistance value output from each measuring
unit and calculates the position of the lens module derived on the
signal.
9. The digital camera module as claimed in claim 1, wherein the
measuring unit is an ohmmeter.
10. A digital camera module comprising: a lens holder; a lens module
axially movably received in the lens holder; and a position tracking
device, the position tracking device comprising a resistor, a probe
and a measuring unit, one of the resistor and the probe being attached
to the lens holder and the other being attached to the lens module,
the resistor and the probe slidably contacting with each other,
the measuring unit electrically connecting with the resistor and
the probe in series so as to form a loop, the measuring unit being
configured for measuring a resistance value of the resistor as it
changes with movement of the lens module thus enabling it to detect
the position of the lens module.
11. The digital camera module as claimed in claim 10, wherein the
probe comprises a pin projecting therefrom, and the pin slidingly
contacts the resistor as the lens module moves relative to the lens
holder.
Digital Camera Patent Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to digital camera
modules, and more particularly to a digital camera module which
integrates a position tracking device for tracking a real-time position
of a lens module.
[0003] 2. Discussion of the Related Art
[0004] Nowadays, digital cameras with an automatic focus (AF) function
are widely used. The AF apparatus works by detecting the focusing
state of an image-taking lens to find a defocus amount (i.e. the
distance by which the camera is out of focus), calculating a movement
amount of a focus lens corresponding to the defocus amount, and
driving the focus lens to move. However, there is a risk that an
actual movement amount of the focus lens driven to move will not
be the same as the target movement amount and the focusing accuracy
of the digital camera will be affected as a result.
[0005] What is needed, therefore, is a digital camera module with
position tracking device which tracks a real-time position of a
lens module for improving focusing accuracy.
SUMMARY OF THE INVENTION
[0006] In one aspect, a digital camera module for a portable electronic
device includes a lens holder, a lens module axially movably received
in the lens holder and at least one position tracking device. Each
position tracking device includes a resistor secured to the holder,
a probe attached to the lens module and slidably contacting with
the resistor, and a measuring unit electrically connecting with
the resistor and the probe therebetween in series for measuring
a resistance value of the resistor as it changes with the movement
of the lens module thus enabling it to detect the position of the
lens module.
[0007] Other advantages and novel features will become more apparent
from the following detailed description of preferred embodiment
when taken in conjunction with the accompanying drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Many aspects of the present digital camera module with a
position tracking device can be better understood with reference
to the following drawings. The components in the drawings are not
necessarily drawn to scale, the emphasis instead being placed upon
clearly illustrating the principles of the digital camera module
with a position tracking device. Moreover, in the drawings, like
reference numerals designate corresponding parts throughout the
several views.
[0009] FIG. 1 is a schematic, exploded, isometric view of a digital
camera module in accordance with a preferred embodiment, without
showing a measuring unit; and
[0010] FIG. 2 is an assembled, cross-sectional view of FIG. 1,
but showing the measuring unit.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0011] The digital camera module with a position tracking device
of the present invention is suitable to use in portable electronic
devices, such as cameras, mobile phones, personal digital assistants
(PDA), palm computers and so on, which can contain a digital camera
module having an AF function therein. Referring to FIG. 1 and FIG.
2, a digital camera module 100 according to a preferred embodiment
includes a lens module 10, a lens holder 20 and a position tracking
device 30. The lens module 10 is received in the lens holder 20
and can be driven to move axially in the lens holder 20. The position
tracking device 30 is used to detect a position of the lens module
10 received in the lens holder 20.
[0012] The lens module 10 includes a lens barrel 11, a lens group
13 and an infrared-cut filter (IR-cut filter) 14. The lens barrel
11 has a first half-opening end 12 and a second opening end (not
labeled) opposite to the first end 12. The lens barrel 11 has a
groove 15 defined in an outer peripheral surface (not labeled) of
the barrel 11, axially extending from the second end to the first
end 12. In a central portion of the first end 12, there is a window
121 for transmitting light beams into the lens barrel 11. The window
12 includes a transparent board 122 embedded therein, in order to
seal the first end 12, and protect the lens group 13 from dust and/or
particle pollution/contamination. It is to be understood that, a
focus lens could be embedded in the window 121 instead of the transparent
board 122. The focus lens can converge external light beams into
the lens barrel 11 while preventing dust and/or particle pollution/contamination.
[0013] The lens holder 20, which is a cylinder in shape, includes
an inner surface 21 and a receiving chamber 23 defined therein.
The inner surface 21 peripherally surrounds the receiving chamber
23, and has a slot 25 defined therein. The slot 25 communicates
with the receiving chamber 23, and corresponds to the groove 15
of the barrel 11. The receiving chamber 23 is used to receive the
barrel 11 of the lens module 10, and has a profile slightly larger
than that of the barrel 11.
[0014] The position tracking device 30 includes a probe 31, a resistor
33, a measuring unit 35 and a controlling unit (not shown). The
probe 31 is made from electric conducting material, and has a pin
311 projecting therefrom. The probe 31 is embedded in and fixed
to the groove 15 of the barrel 11, with the pin 311 extending out
of the groove 15. The resistor 33 is received in the slot 25 and
fixed to the lens holder 20. The measuring unit 35, such as an ohmmeter,
electrically connects with the probe 31 and one end of the resistor
33 therebetween in series. The lens module 10 is received in the
receiving chamber 23 of the holder 20, and the pin 311 of the probe
31 electrically contacts with the resistor 33. Therefore, the measuring
unit 35 measures a resistance value of the resistor 33 between a
contact position where the pin 311 contacts with the resistor 33
and the end of the resistor 33 electrically connecting with the
measuring unit 35, which is in association with the movement of
the lens module 10 to detect the position of the lens module 10
received in the lens holder 20. The measuring unit 35 outputs a
signal with the resistance value corresponding to the position of
the lens module 10. The controlling unit electrically connects with
the measuring unit 35 and receives the signal with the resistance
value. The controlling unit calculates the position of the lens
module 10 received in the lens holder 20 from the resistance value
transmitted from the measuring unit 35.
[0015] In use of the digital camera module 100, which is integrated
into a portable electronic device, the measuring unit 35 is electrically
connected with a power source such as a battery of the portable
electronic device in order to supply electrical power. The controlling
unit could be a micro controller unit (MCU) of the portable electronic
device. When the digital camera module 100 needs to AF, the lens
module 10 is driven by an actuator, such as a step motor integrated
in the electronic portable device, to axially move in the lens holder
20. The contact position jointly changes, and the resistance value
of the resistor 33 between the contact position and said end of
the resistor 33 changes in response to the movement of the lens
module 10. The controlling unit receives the continuously varied
signal with the resistance value from the measuring unit 35 and
calculates the position of the lens module 10 deriving on the resistance
value. Therefore, in this manner the tracking of the position of
the lens module 10 received in the lens holder 20 is achieved. If
the actual movement amount of the lens module 10, which is calculated
by the controlling unit deriving on the signal output from position
tracking device 30, is unequal to the target movement amount of
the lens module 10, the controlling unit triggers the actuator to
drive the lens module 10 until the actual movement amount of the
lens module 10 is equal to the target movement amount.
[0016] It is to be understood that the position tracking device
30 could include multiple groups of the probe 31, the resistor 33
and the measuring unit 35. The probes 31 can be axially mounted
to the lens barrel 11 and spaced from each other. The resistors
33 can be mounted to the lens holder 20, each resistor 33 contacting
with a probe 31. Each measuring unit 35 can electrically connect
with a corresponding probe 31 and a corresponding resistor 33. The
controlling unit electrically connects with the measuring units
35 of each group, and compares the resistance values simultaneously
transmitted from the measuring units 35 to estimate whether the
lens barrel 11 moves axially or deviates from the axis.
[0017] It is believed that the present embodiments and their advantages
will be understood From the foregoing description, and it will be
apparent that various changes may be made thereto without departing
from the spirit and scope of the invention or sacrificing all of
its material advantages, the examples hereinbefore described merely
being preferred or exemplary embodiments of the invention. |