Pixel control circuitry for spatial light modulator

• US 5,548,301 A
• Filed: 09/02/1994
• Issued: 08/20/1996
• Est. Priority Date: 01/11/1993
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Conner, James L., Kornher, Kevin L.
• Primary Examiner(s): SARAS, STEVEN J
• Application Number:
  US08/300,356
• Time in Patent Office: 718 Days
• Field of Search: 345/84, 345/85, 345/206, 345/205, 345/132, 345/55, 345/147, 348/770, 348/771
• US Class Current: 345/85
• 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 2300/0804 Sub-multiplexed active matrix panel, i.e. wherein one active driving circuit is used at pixel level for multiple image producing elements
• CPC Class Codes: G09G 2300/0857 Static memory circuit, e.g. flip-flop
• CPC Class Codes: G09G 2330/10 Dealing with defective pixels
• CPC Class Codes: G09G 3/2022 using sub-frames
• 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: H04N 5/7458 the modulator being an array of deformable mirrors, e.g. digital micromirror device [DMD]

Abstract

A spatial light modulator (10) having reduced control circuitry as compared to existing devices. Sets of pixel elements (11) share a memory cell (12), such that each memory cell (12) has the same fanout as other memory cells (12). Each pixel element (11) in a set is switched to an on or off state via a reset line (13) that is separate from that of the other pixel elements (11) in that set. Frame data is loaded in split bit-frames during a set time period, such that each split bit-frame contains only the data for pixel elements (11) on one reset line (13). Thus, the same memory cell (12) can be used to deliver data to all pixel elements (11) in its fanout because only one pixel element (11) in the fanout is switched at a time.

Claims

1. A method of pulse-width modulating frames of multi-bit frame data used by a spatial light modulator, having an array of pixel elements, comprising the steps of:

dividing the time to display each frame of data into equal time units;

dividing a frame of data into split bit-frames, each split bit-frame containing data for pixel elements connected to an associated reset line;

delivering data representing said split bit-frame of data to memory cells, wherein each memory cell is connected to a set of said pixel elements and receives a data bit representing an on or off state of only one of its pixel elements;

loading said pixel elements, by using each memory cell to apply a data signal representing the data bit received by that memory cell to its associated pixel elements;

switching said pixel elements, by using a reset signal to change the state of all pixel elements connected to said reset line;

repeating the above delivering, loading, and switching steps for each split bit-frame of data within a data frame.

2. The method of claim 1, wherein the first loading step coincides with the beginning of a frame time period.

3. The method of claim 1, wherein the pixel elements connected to each reset line receive at least one split bit-frame containing a higher valued bit before receiving a split bit-frame containing the least significant bit.

4. The method of claim 1, wherein said dividing step is performed such that each time slice represents the display time for a least significant bit of data of each data value.

5. The method of claim 1, wherein said loading step and all repeated loading steps are performed such that each pixel element of a set is loaded during a continuous series of initial time slices.

6. The method of claim 1, wherein said loading step is performed so that the data for any one pixel element in each set begins and ends in the same position relative to each frame.