Abstract:
The combined actuator described can be incorporated into a miniaturized camera product. In the camera product, the shutter driver uses the focus or zoom actuator&#39;s power amplifiers to control the current flow in shutter actuators. As such, the space needed for the camera&#39;s electronics is smaller and it is less expensive to manufacture the camera product.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application is related to U.S. patent application Ser. No. 11/205,558, filed Aug. 17, 2005 and incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates generally to miniaturized camera products. More specifically, the present invention relates to a combined actuator that drives both shutter and focus functions in miniaturized camera products.  
         [0004]     2. Description of the Related Art  
         [0005]     This section is intended to provide a background or context. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the claims in this application and is not admitted to be prior art by inclusion in this section.  
         [0006]     The traditional shutter driver for a camera forces constant current to be drawn through a magnetic actuator. To have a predictable and stable closing time, the current needs to be an accurate DC current. The actuation principle is similar for aperture adjust and neutral density (ND) filter actuators. The magnetic actuator has equivalent resistance and inductance. Generally, current needed for the shutter driver is between 60 mA and 200 mA. The direction of the current determines the opening or closing of the shutter.  
         [0007]      FIG. 1  illustrates a circuit diagram of a traditional driver for a camera shutter and iris-ND filter. To close the shutter, switch S 1  is closed and S 2  is open. To close the iris-ND filter, switch S 5  is closed and S 6  is open. In either situation (closing the shutter or closing the iris-ND filter), switch S 4  is closed and S 3  is open. When S 4  is closed, an operational amplifier  20  forces the voltage over a resistor  22  to be equal to the reference voltage, Vref by controlling the gate voltage of G 1  or G 5  depending upon whether the shutter or iris is opened. The gate voltage defines the channel resistance of the MOSFET, which in turn, defines the current. The closed loop control system sets the current to the Vref/R. The resistor is often an external 1% accurate resister. A one Ohm resistor is a typically selection.  
         [0008]     To open the shutter, switch S 1  is opened and S 2  is closed. To open the iris-ND filter, switch S 5  is opened and S 6  is closed. In either situation (opening the shutter or opening the iris-ND filter), switch S 3  is closed and S 4  is open when S 2  or S 6  is closed (depending whether shutter or iris is operated). An operational amplifier  20  forces the voltage over a resistor  22  to be equal to the reference voltage, Vref, by controlling the gate voltage of G 3 . The gate voltage defines the channel resistance of the MOSFET, which in turn defines the current. The closed loop control system sets the current to the Vref/R. In this configuration, current flows in a different direction (compared to the closing situation).  
         [0009]     Generally, the shutter actuator has a resistance of about 8-24 Ohms and requires current from about 60 mA to 200 mA. Where the resistance is 8 Ohms and the current is 200 mA, the voltage over the actuator is 1.6 V. About 0.2 V is needed over the resistor. Mobile cameras typically have a supply voltage of 2.8 V. Thus, only 1 V is left to be divide over switch S 1  and S 4 . It follows that the resistance of S 1  and S 4  should be 2.5 Ohms, which is a large area low Ron MOSFET. Currently, the trend in mobile devices is to reduce the supply voltage, which would require even larger MOSFETS.  
         [0010]     Class D amplifiers are typically used to drive zoom and autofocus actuators. These actuators can be piezoceramic actuators. A class D amplifier is an amplifier in which the output transistors are operated as switches rather than as a current source. Because an ideal switch has either zero voltage across it or zero current through it at all times, it dissipates no power. When a particular transistor is turned off, the current through it is zero. When the transistor is turned on, the voltage across the switch is small (ideally zero). This increases the overall efficiency of the amplifier, requiring less power from the power supply and smaller heat sinks for the amplifier.  
         [0011]     A conventional tuned class D type of amplifier is shown in  FIG. 2 ( a ). A class D amplifier includes a P-type FET (PFET), an N-type FET, (NFET) two body diodes and a tuned load. The two FET gates are driven with signals that are about identical, but that prevents a simultaneous state of the two FET gates and a large shoot through current flow from the supply to ground. Another version of class D amplifier is shown in  FIG. 2 ( b ), where a rectangular waveform is applied to a low-pass filter rather than a tuned filter. The low-pass filter allows only its slowly-varying DC or average voltage to appear on the load. In  FIG. 2 ( b ), separate V P  and V N  drive stages are shown. These can be used to make the drive signals for V P  and V N  such that a simultaneous ON state for the two semiconductor switches can be prevented. The circuit shown in  FIG. 2 ( a ) can also have such driving of the gates. Although reasonably useful, class D amplifiers suffer from significant drawbacks. The major factors limiting the performance of class D inverters are switching losses and switching noise as discussed below. The switching loses result at least partially from resistive losses in Ron of switching devices. As such, it is advantageous to have low Ron devices driving piezo actuators. Although, in contrast to class A, B, and C amplifiers, switched mode power amplifiers such as class D amplifiers have an idealized efficiency of 100%, the combination of switching and conduction losses sets an upper bound on the amplifiers&#39; power efficiency.  
         [0012]     U.S. patent application Ser. No. 11/205,558, filed Aug. 17, 2005 and which is assigned to the same assignee as the present application, provides for the use of class DE amplifiers in conjunction with piezoceramic elements for actuating digital camera systems such as autofocus and zoom lens systems. In class DE amplifiers, switching losses are reduced in comparison to class D amplifiers. Each switching transistor in a class DE amplifier is on for less than a half period. There are two intervals of time in a period when both of the transistors are simultaneously off. During these intervals of “under lapping,” the shunt capacitances are recharged by the load current from 0 to V max  or from V max  to 0. As such, each transistor is turned on under its output voltage V out ≈0. Therefore, the switching power losses are substantially absent. In addition, electromagnetic interference is reduced because of “soft switching” during the dead time of the switches.  
         [0013]      FIG. 3  illustrates a conventional combination of a shutter-iris driver and an autofocus/zoom actuator driver. The combination includes an iris-neutral density (ND) filter  32 , a shutter  34 , a piezo actuator  36 , and a piezo actuator  38 . The iris-ND filter  32  is coupled to MOSFETS  42 ,  44 ,  46 , and  48 . The shutter  34  is coupled to MOSFETS  46 ,  48 ,  50 , and  52 . The piezo actuator  36  is coupled to MOSFETS  54  and  56 . The piezo actuator  38  is coupled to MOSFETS  58  and  60 . As such, regardless of whether a class D or class DE amplifier is used, the conventional combination of a shutter iris driver and zoom/autofocus functions needs 10 MOSFETS and 5 outputs (outputs  61 - 65 ).  
         [0014]     Thus, there is a need for a combination actuator that saves four MOSFETS and two outputs, resulting in six MOSFETS and 3 outputs. Further, there is a need for a combination actuator that results in smaller used silicon space and reduced costs to manufacture.  
       SUMMARY OF THE INVENTION  
       [0015]     In general, the present invention provides a combined actuator incorporated into a miniaturized camera product. In the camera product, the shutter driver uses the focus or zoom actuator&#39;s power amplifiers to control the current flow in shutter actuators. As such, the space needed for the camera&#39;s electronics is smaller and it is less expensive to manufacture the camera product.  
         [0016]     One exemplary embodiment relates to a driver configured to provide electric current to an autofocus/zoom driver and a light control driver. The driver includes first switches configured to couple to a first actuator, second switches configured to couple to a second actuator, and a multiplexer selecting inputs to the first and second switches. The first and second switches are coupled to the light control driver.  
         [0017]     Another exemplary embodiment relates to a combination system that drives a camera shutter and camera filter as well as a camera autofocus and zoom control. The system includes a filter coupled to a first plurality of MOSFETs, a shutter coupled to a second plurality of MOSFETs, and actuators coupled to a third plurality of MOSFETs. The first plurality of MOSFETS includes first, second, third and fourth MOSFETs; the second plurality of MOSFETs includes first, second, fifth and sixth MOSFETs; and the third plurality of MOSFETs includes third, fourth, fifth and sixth MOSFETs.  
         [0018]     Another exemplary embodiment relates to a method of driving a camera shutter, a camera filter, a camera zoom lens, and a camera autofocus lens. The method includes opening a camera shutter by closing a first switch, opening a second switch, opening a fifth switch, and closing a sixth switch; driving a camera zoom lens by opening the first and second switches and selectively manipulating actuators using third, fourth, fifth and sixth switches; and opening a camera filter by opening a first switch, closing a second switch, opening a third switch, and closing a fourth switch.  
         [0019]     Other exemplary embodiments are also contemplated, as described herein and set out more precisely in the appended claims. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0020]      FIG. 1  is a circuit diagram of a traditional driver for a camera shutter and iris-neutral density (ND) filter.  
         [0021]     FIGS.  2 ( a ) and  2 ( b ) are representations of conventional class D amplifiers.  
         [0022]      FIG. 3  is a circuit diagram of a conventional combination of a shutter-iris driver and an autofocus/zoom actuator driver.  
         [0023]      FIG. 4  is a perspective view representation of a mobile phone having a camera module constructed in accordance with an exemplary embodiment.  
         [0024]      FIG. 5  is a schematic representation of circuitry of the mobile phone of  FIG. 3  in accordance with an exemplary embodiment.  
         [0025]      FIG. 6  is a representation of a miniaturized camera module for the mobile phone of  FIG. 3  in accordance with an exemplary embodiment.  
         [0026]      FIG. 7  is a circuit diagram of a combined shutter-iris driver and autofocus/zoom actuator driver in accordance with an exemplary embodiment.  
         [0027]      FIG. 8  is the circuit diagram of  FIG. 7  with switches and iris filter removed in accordance with an alternative embodiment.  
         [0028]      FIG. 9  is a first alternative embodiment for the circuit of  FIG. 7 .  
         [0029]      FIG. 10  is a second alternative embodiment for the circuit of  FIG. 7 .  
         [0030]      FIG. 11  is a third alternative embodiment for the circuit of  FIG. 7 .  
     
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
       [0031]      FIGS. 4 and 5  illustrate a representative mobile telephone  72  within which a camera module constructed according to the principles of the exemplary embodiments may be implemented. It should be understood, however, that the present invention is not intended to be limited to one particular type of mobile telephone  72  or other electronic device. The present invention can also be incorporated into a stand alone digital camera with no additional accessories.  
         [0032]     The mobile telephone  72  of  FIGS. 4 and 5  includes a housing  74 , a display  76  in the form of a liquid crystal display, a keypad  78 , a microphone  80 , an ear-piece  82 , a battery  84 , an infrared port  86 , an antenna  86 , a smart card  88 , a card reader  90 , radio interface circuitry  92 , codec circuitry  94 , a controller or processor  96  and a memory  98 . Individual circuits and elements are all of a type well known in the art, for example in the Nokia range of mobile telephones. A camera module  100  is also operatively connected to the controller or processor  96 .  
         [0033]      FIG. 6  illustrates the camera module  100  from an exploded view (A), a first perspective view (B), a second perspective view (C), and a cutout view (D). In an exemplary embodiment, the camera module  100  has a height of 32.1 mm and a width and thickness of 19.4 mm and 14.3 mm, respectively. As can be appreciated by a person of skill in the art, reduction of electric circuitry is helpful in the design and operation of the camera module  100 .  
         [0034]      FIG. 7  illustrates a combination of a shutter-iris driver and an autofocus/zoom actuator driver in accordance with an exemplary embodiment. The combination can be implemented in a device such as mobile telephone  72  described with reference to  FIGS. 4-6 . The implementation illustrated includes an iris-neutral density (ND) filter  102 , a shutter  104 , a piezo actuator  106 , a piezo actuator  108 . The iris-ND filter  102  is coupled to MOSFETS  112 ,  114 ,  116 , and  118 . The shutter  104  is coupled to MOSFETS  112 ,  114 ,  120 , and  122 . The piezo actuator  106  is coupled to MOSFETS  116  and  118 . The piezo actuator  108  is coupled to MOSFETS  120  and  122 . As such, the combination illustrated in  FIG. 6  functions with  6  MOSFETS and  3  outputs (outputs  131 - 133 ). In alternative embodiments, the MOSFETS  112 - 122  are replaced by other suitable switching devices.  
         [0035]     Output  131  is connected to iris-ND filter  102  and shutter  104 . Output  132  is connected to shutter  104  and piezo actuator  108 . Output  133  is connected to iris-ND filter  102  and piezo actuator  106 . In such a configuration it is assumed that the camera autofocus or zoom does not work at the same time as the shutter. The situation where autofocus and zoom do not work simultaneously is typical because actuators are first driven to the correct zoom factor and focus position, and then the image is taken. The shutter closing is used to define the end fo the exposure time of the image. When the camera autofocus or zoom operates, S 3  and S 4  (MOSFETS  112  and  114 ) are open and output  131  is a high impedance node (N 1 ), which does not allow current to flow.  
         [0036]     The camera autofocus and zoom are controlled using actuators  106  and  108 . The camera autofocus and zoom normally do not operate at the same time. In some embodiments, however, separate PWM modules are used, allowing autofocus and zoom to operate independently. The actuators  106  and  108  are controlled by MOSFETS  116 ,  118 ,  120 , and  122 . MOSFET  116  is coupled to a multiplexer  135  and MOSFET  120  is coupled to a multiplexer  136 . Either the multiplexer  136  or the multiplexer  135  selects a gate control voltage or a pulse width modulation (PWM) pattern as an input to the MOSFET  116  or  120 . A multiplexer (not shown) is also used to select the gate control of mosfets  112  and  114  between the PWM pattern and the actuating of the iris-ND filter  102  or shutter  104 . To close the shutter  104 , MOSFET  120  (S 9 ) and MOSFET  114  (S 4 ) are closed and are controlled by a control loop. To open the shutter  104 , MOSFET  112  (S 3 ) and MOSFET  122  (S 10 ) are both closed, MOSFET  114  (S 4 ) and MOSFET  120  (S 9 ) are both opened, MOSFET  116  (S 7 ) and MOSFET  118  (S 8 ) are both opened, and output  133  is a high impedance node.  
         [0037]     The following table details the state of each switch depending on whether the iris/camera shutter needs to be opened or closed. When reading this table, it is noted that the Vref voltage controls the opening and closing of the camera shutter. When Vref=low, the shutter is closed while, when Vref=high, the shutter is open.  
                                                                                                                         shutter       Iris/ND filter                                Switch   Open   Close   Open   Close           S3   Closed   Open   Open   Closed           S4   Open   Closed   Closed   Open           S7   X1   X2   Closed   Open           S8   X2   X2   Open   Closed           S9   Open   Closed   X2   X1           S10   Closed   Open   X2   X2                            zoom   autofocus                            S3   Open   Open           S4   Open   Open           S7   Open   PWM           S8   Open   PWM           S9   PWM   Open           S10   PWM   Open                         X1 - The state of the switch could be open or closed. If it is closed, there is approximately the same voltage on each terminal and, therefore, the driver does not cause motion in the element while the other element is being moved.                X2 - The state of the switch can be open but not closed. If it is closed, there is a voltage across one element while the other element is being moved, causing both elements to be moved at the same time.                PWM - PWM refers to a pulse width modulation (PWM) pattern used as an input to switches S7-S10.             
 
         [0038]      FIG. 8  illustrates the combination described with reference to  FIG. 7  except MOSFETs  112  and  114  and iris-ND filter  102  have been removed. Alternatively, iris-ND filter  102  could be present and the shutter  104  is removed. Iris-ND filter  102  and shutter  104  are light control elements. A camera device may have only one of the iris-ND filter  102  and shutter  104  in mechanical form. For example, some iris arrangements could be electronic.  
         [0039]      FIG. 9  and  FIG. 10  illustrate alternative embodiments to the embodiment described with reference to  FIG. 7 .  FIG. 9  illustrates that MOSFET  112  (S 3 ) has been replaced by a current source  112 ′.  FIG. 10  illustrates that MOSFET  114  (S 4 ) has been replaced by a current source  114 ′. Such an embodiment has an advantage in that it is not necessary to multiplex the analog control voltage to Class D amplifiers. Class D switches may require complex driving circuitry, and it is difficult to bring an analog control voltage to this circuitry. Current sources  112 ′ and  114 ′ can be made using a local feedback loop, as illustrated in  FIG. 11 .  FIG. 11  also does not require inductors to the piexo actuators  106  and  108 . Depending on the embodiment, both outputs  132  and  133  can be part of an autofocus actuator such that the actuator for the shutter can be driven by a frequency that it can be responsive to.  
         [0040]     Advantageously, the configuration illustrated in  FIGS. 4-11  provides for a camera on a mobile communicator having a combination shutter-iris driver and an autofocus/zoom actuator driver. This combination includes six MOSFETS and 3 outputs, which is a reduction in four MOSFETS and two outputs from conventional configurations. The reduced circuitry results in smaller used silicon space and reduced costs to manufacture. Further, if driving electronics are outside of the camera module, fewer pads in the camera module mechanical interface are needed. Fewer pads helps in reducing the size requirements of the camera module.  
         [0041]     While several embodiments of the invention have been described, it is to be understood that modifications and changes will occur to those skilled in the art to which the invention pertains. Accordingly, the claims appended to this specification are intended to define the invention more precisely.