Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1999-05-10
2003-09-16
Garber, Wendy R. (Department: 2612)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C348S333060, C348S333010, C377S069000
Reexamination Certificate
active
06621481
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a shift register, a display device having a driver including the shift register, an image sensing element driving apparatus, and an image sensing apparatus.
In recent years, digital still cameras for recording still images are popularly used. Such a digital still camera has a liquid crystal display device functioning as a viewfinder for displaying an image sensed by an image sensing element and also functioning as a display for displaying an image recorded on an image memory.
As the liquid crystal display devices, active matrix type devices are generally used because of their wide angles of field and good response characteristics. To drive an active matrix type liquid crystal display device, a gate driver for selecting any one of gate lines formed in units of rows of pixels arranged in a matrix on a liquid crystal panel, and a drain driver for receiving a pixel signal in units of gate lines and supplying the received pixel signal to the pixel corresponding to the selected gate line through drain lines are required. Each of the gate and drain drivers is generally formed from a plurality of TFTs. Each TFT outputs a signal supplied to its drain to the source on the basis of a gate signal. The output voltage value changes depending on the voltage value of the gate signal.
Each of the gate and drain drivers is generally constituted by a multistage shift register in which a signal is sequentially transmitted from a preceding stage to the subsequent stage. However, in such a shift register, a circuit immediately before a portion where a signal is output to the next stage must have a so-called EE structure. Thus a perfect OFF resistance can hardly be obtained, so that the output voltage from each stage gradually attenuates.
Some digital still camera can arbitrarily change the direction of an image sensing lens with respect to a camera body. For example, there are cameras capable of rotating a lens unit with an image sensing lens with respect to the main body to photograph an image on the photographer side. In this case, for example, the face of a photographer can be displayed on the liquid crystal display device as a mirror image (vertically inverted image or horizontally inverted image). Conventionally, however, to display a mirror image, complex control must be performed by a controller for supplying an image to the liquid crystal display device to change the read order of image data.
In addition, to display an image freely inverted in the vertical or horizontal, direction in accordance with the photographing situation on the liquid crystal display device of a digital still camera, complex control must be performed by a controller for supplying an image to change the read order of image data.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a shift register which can transmit a signal input to each stage to the next stage without attenuating the signal level and also output an output signal having a high S/N ratio, and is suitable as a driving circuit of a display device.
It is another object of the present invention to provide a display device capable of arbitrarily changing the direction of an image to be displayed by simple control, and an image sensing apparatus having the display device.
In order to achieve the above objects, according to the first aspect of the present invention, there is provided a shift register having a plurality of stages, each of the stages comprising:
a first switching circuit which has a control terminal for receiving a first or second control signal and outputs a driving signal in accordance with the first or second control signal;
a second switching circuit which has a control terminal for receiving the driving signal and discharges a power supply voltage input through a load in accordance with input of the driving signal to this control terminal; and
a third switching circuit which has a control terminal for receiving the driving signal and outputs a third or fourth control signal in accordance with input of the driving signal to this control terminal, or
a first switching circuit which has a control terminal for receiving a first or second control signal and outputs a driving signal to a line in accordance with the first or second control signal;
a second switching circuit which has a control terminal connected to the line and sets a power supply voltage input through a load to a low potential in accordance with input of the driving signal to this control terminal; and
a third switching circuit which has a control terminal connected to the line and outputs a third or fourth control signal in accordance with input of the driving signal to this control terminal.
According to the first aspect, as the transistor characteristics (when a transistor is used as the third switching circuit), the magnitude of the voltage output from the third switching circuit is determined in accordance with the magnitude of the voltage of the driving signal input to the third control terminal of the third switching circuit. When the driving signal is input to the third switching circuit through the third control terminal, the voltage of the third or fourth control signal is stored in the accumulation capacitance between the control terminal of the third switching circuit and the terminal for outputting the third or fourth control signal. Accordingly, the potential at the control terminal increases. Hence, the potential of the third or fourth control signal output from the third switching circuit increases, and a constant voltage can be continuously held without any attenuation in shift to the next stage.
The register may comprise a fourth switching circuit for, in accordance with the power supply voltage input through the load of a predetermined stage, discharging the driving signal input to a next stage of the predetermined stage through the first switching circuit of the next stage. The level of the third or fourth control signal is inverted at a predetermined period. When the level of one of the first and second control signals is inverted in only part of every half period of the level inversion period of the third or fourth control signal, the fourth switching circuit can be turned off in the shift register, even if one of the third and fourth control signals as the output signal from each stage goes high, so the third or fourth signal of high level can be almost directly output as the output from each stage. For this reason, the S/N ratio of the output signal can be made high.
The shift register further comprises a selection control circuit for selectively supplying an externally supplied start signal to one of a first stage and a final stage, a first driving circuit for inputting a Kth driving signal from the third switching circuit of a (K−1)th stage to the first switching circuit of a Kth stage and outputting a (K+1)th driving signal from the third switching circuit of the Kth stage to a (K+1)th stage, a second driving circuit for outputting a (K+2)th driving signal from the third switching circuit of the (K+1)th stage to the Kth stage and outputting the (K+1)th driving signal from the third switching circuit of the Kth stage to the (K−1)th stage, and a shift direction control circuit for selectively driving the first and second driving circuits. With this arrangement, a forward or reverse direction can be selected as the direction in which the third or fourth control signal is output in the shift register.
In order to achieve the above objects, according to the second aspect of the present invention, there is provided a display device having a plurality of pixels, wherein each stage comprises:
a first switching circuit which has a control terminal for receiving a first or second control signal and outputs a driving signal in accordance with the first or second control signal;
a second switching circuit which has a control terminal for receiving the driving signal and discharges a power supply voltage, input through a load, in accordan
Casio Computer Co. Ltd.
Garber Wendy R.
Misleh Justin
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