CIRCUITS FOR CONTROLLING DISPLAY APPARATUS

• US 20110164067A1
• Filed: 01/05/2010
• Published: 07/07/2011
• Est. Priority Date: 01/05/2010
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Pixtronix, Incorporated (Qualcomm, Inc.)
• Inventors: English, Stephen, Lewis, Stephen R., McAllister, Abraham
• Granted Patent: US 9,082,353 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: G02B 26/04 by periodically varying the intensity of light, e.g. using choppers shutters, diaphragms for cameras G03B9/00; devices for eliminating or reducing the effect of flicker in projection systems G03B21/40
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G09G 2300/0456 with a reflective area and a transmissive area combined in one pixel, such as in transflectance pixels
• CPC Class Codes: G09G 2300/08 Active matrix structure, i.e. with use of active elements, inclusive of non-linear two terminal elements, in the pixels together with light emitting or modulating elements
• CPC Class Codes: G09G 2300/0814 used for selection purposes, e.g. logical AND for partial update
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0857 Static memory circuit, e.g. flip-flop
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2310/0262 The addressing of the pixel, in a display other than an active matrix LCD, involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependent on signals of two data electrodes
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 3/2003 Display of colours specific for liquid crystal displays G09G3/3607
• CPC Class Codes: G09G 3/2022 using sub-frames
• CPC Class Codes: G09G 3/2074 using sub-pixels
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3433 using light modulating elements actuated by an electric field and being other than liquid crystal devices and electrochromic devices using liquid crystal devices G09G3/36; using electrochromic devices G09G3/38
• CPC Class Codes: G09G 3/346 based on modulation of the reflection angle, e.g. micromirrors micromirrors devices per se G02B26/0833
• CPC Class Codes: H03K 3/037 Bistable circuits

Abstract

The invention relates to methods and apparatus for forming images on a display utilizing a control matrix to control the movement of MEMS-based light modulators.

Claims

1. A direct-view display apparatus comprising:

an array of pixels comprising, for each pixel, a MEMS-based light modulator formed on a substrate and including a first actuator and a second actuator opposing the first actuator for controlling the state of the light modulator to form an image on the display apparatus; and

a control matrix disposed on the substrate comprising, for each pixel;

a dual inverter latch coupling the first and second actuators and configured to maintain an opposite logical state on the first and second actuators.

2. The display apparatus of claim 1, wherein the substrate is a transparent substrate.

3. The display apparatus of claim 1, wherein the dual inverter latch comprises two cross-coupled inverters.

4. The display apparatus of claim 3, wherein each of the two cross-coupled inverters comprises two transistors.

5. The display apparatus of claim 3, wherein each of the two cross-coupled inverters comprises dual gate transistors.

6. The display apparatus of claim 3, wherein each of the two cross-coupled inverters are connected to a cascode circuit.

7. The display apparatus of claim 1, further comprising a data store, wherein the dual inverter latch is latched in a first state based, at least in part, on a data voltage stored in the data store.

8. The display apparatus of claim 7, further comprising a switch coupling the data store to the dual inverter latch for allowing the data to pass from the data store to the dual inverter latch.

9. The display apparatus of claim 8, wherein the switch is controlled by a common voltage interconnect for a plurality of rows and columns.

10. The display apparatus of claim 8, wherein the switch functions to electrically de-couple the data store from the dual inverter latch to prevent current from flowing between the data store and the dual inverter latch.

11. The display apparatus of claim 10, further comprising an actuation line interconnect, wherein the actuation line interconnect is configured to provide a voltage to only one of the first and second actuators for actuating the light modulator to form an image.

12. The display apparatus of claim 11, wherein the actuation line interconnect further provides an intermediate voltage to latch the dual inverter latch in a first state corresponding to the data voltage.

13. A method for addressing pixels in a display wherein each pixel includes a MEMS based light modulator, first and second actuators, and a dual inverter latch coupling the first and second actuators for maintaining an opposite logical state on the first and second actuators comprising:

loading data into a data store coupled to the dual inverter latch;

updating the latch state based at least in part on the loaded data such that a full actuation voltage is only applied to one of the first and second actuators; and

actuating the MEMS based light modulator.

14. The method of claim 13, wherein actuating the MEMS-based light modulator comprises applying voltages to the MEMS-based light modulator and the first and second actuators in accordance with a polarity reversal process.

15. The method of claim 13, wherein loading data into the data store comprises:

applying a write-enable voltage to a row interconnect associated with a row in the display;

determining the next state of at least one pixel in the row; and

applying a data voltage corresponding to the next state of the pixel to a corresponding column interconnect.

16. The method of claim 15, wherein the data store comprises a capacitor and the method further comprises storing the applied data voltage as electrical charge on the capacitor.

17. The method of claim 13, wherein the display further comprises an actuate interconnect coupled to the dual inverter latch and a common interconnect coupled to the dual inverter latch, and wherein updating the latch state further comprises:

setting the actuate interconnect voltage to be approximately the same as the common interconnect voltage;

applying an update voltage to an update interconnect;

applying an intermediate voltage to the actuate interconnect; and

removing the update voltage from the update interconnect.

18. The method of claim 17, wherein applying an update voltage to the update interconnect further comprises:

switching at least one update switch connected to the update interconnect to an ‘

on’

state; and

allowing stored data to be passed from the data store to the dual inverter latch.

19. The method of claim 18, wherein removing the update voltage from the update interconnect further comprises electrically isolating the data store from the dual inverter latch.

20. The method of claim 17, wherein removing the update voltage from the update interconnect occurs prior to actuating the MEMS based light modulator.

21. The method of claim 17, wherein setting the actuate interconnect voltage to be approximately the same as the common interconnect voltage occurs prior to applying an update voltage to the update interconnect, and wherein there is a pre-determined delay between setting the actuation interconnect voltage and applying an update voltage.

22. The method of claim 17, wherein applying an intermediate voltage to the actuate interconnect occurs before applying an update voltage to the update interconnect.

23. The method of claim 17, wherein applying an intermediate voltage to the actuate interconnect occurs after applying an update voltage to the update interconnect.

24. The method of claim 17, wherein applying an intermediate voltage to the actuate interconnect occurs simultaneously with applying an update voltage to the update interconnect.

25. The method of claim 17, wherein the intermediate voltage is selected to be sufficient to latch the dual inverter latch corresponding to the data stored in the data store.

26. The method of claim 17, wherein the common interconnect is held at ground potential.

27. The method of claim 17, wherein actuating the MEMS-based light modulator comprises raising the voltage on the actuate interconnect to full voltage.

28. The method of claim 27, wherein the full voltage is the voltage necessary to actuate and hold the MEMS based light modulator in a logical state.

29. The method of claim 28, wherein actuating the MEMS-based light modulator includes causing the light modulator to be attractive to only one of the first and second actuators.