Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1994-05-09
2001-03-20
Brier, Jeffery (Department: 2672)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
Reexamination Certificate
active
06204836
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to inspection circuits of flat type light valve devices used for direct visual type display devices or projection type display devices. More specifically, it relates to light valve devices, and for example, inspection circuits of active-matrix liquid crystal display devices which incorporate integrated circuits, such as a liquid crystal panel formed of driving circuits unitarily into semiconductor thin films.
An active-matrix type liquid crystal display device has an extremely simplified operation principle, where switching elements are provided on each pixel, and in selecting specified pixels the corresponding switching elements are activated, and in a non-selecting state, the switching elements are deactivated. The switching elements are formed on a glass substrate constituting a liquid crystal panel, and it is therefore important to realize a method for more satisfactorily producing thin-film switching elements. For such elements, thin-film type transistors are generally used.
The conventional active-matrix device shown in a schematic circuit diagram in
FIG. 6
, comprises; pixels each arranged in a matrix shape in vertical and horizontal directions and formed of thin-film transistors
1
and electrooptic elements
3
such as liquid crystal elements, control signal lines
5
provided on gate electrodes of the thin film transistors
1
, image signal lines
4
connected to source electrodes, an image signal line driving circuit
8
connected to the image signal lines
4
, and a control signal line driving circuit
6
connected to control signal lines
5
. The control signal line driving circuit
6
is mainly formed of shift registers, where each unit-bit output is connected to the signal lines
5
. The image signal line driving circuit
8
is formed of the shift registers and sample hold circuits provided at every bit basis, and writes the image signals into the sample hold circuits in accordance with sampling signals from output of the shift registers.
The conventional light valve device has more than several hundreds of adjacent pixels arranged respectively in each of the vertical and horizontal directions, the quantity of pixels thus reaches an extent of one million and generally at least an area of more than 1 cm2. It is considerably difficult to produce such elements with a high production yield without any defect, and in general the produced elements are inspected in a form of the driving substrate before completion as a light valve device. For the most normal method of inspection, the measurement to determine acceptance or failure is performed in accordance with the current produced by applying a voltage through a metallic probe (hereinafter referred to as a prober) in contact with the electrodes of elements, or for the output voltage/current etc.
In the method described above, to confirm operation of the elements formed of a large number of pixels of the light valve devices or the like more than several hundreds of probers are required to be in electrical contact with the electrodes of elements at an interval corresponding to a pitch between pixels, and it is therefore difficult to obtain a reliable result in using the present technique. On the other hand, while measurement may be performed while moving a smaller number of probers, this however requires a long time for the measurement process and is not suitable for practical use.
For another method of inspection, it is considered by applicants to provide inspection circuits inside the elements.
FIG. 6
shows an equivalent circuit diagram of the elements used in such inspection method, where transistors
23
having gate electrodes connected to the signal lines
4
are provided on signal output sections ranging from each driving circuit to the pixels, and in the inspection transistors
23
one-side terminals
24
are grounded and the other-side terminals are connected to common terminals
25
thereafter connected to a power supply
27
through a load resistance
26
, such that an output of the load is then detected by the inspection transistors
23
at every bit. Signals from the driving circuit are applied to the signal lines
4
to turn ON the inspection transistors
23
and to produce current flow into the load
26
, and with such current flow detected, the signal transfer to the signal lines
5
is confirmed. By observing timing of the current flow in synchronism with clock of the shift register, a bit relating to the operation can be determined to thereby detect a line on which a malfunction arises.
However, in the inspection circuit of the light valve device, if only one of the detecting FET's having several hundreds of bits comes to a turn-ON state, signals are detected in an output of a buffer amplifier, thus the inspection circuit of the light valve device does not determine on which of the bits the defect is generated in the case of the driving method of simultaneously originating signals for a plurality of bits. The image signal driving circuit generally produces the outputs at the same time from the entire lines. The present invention, which provides a function to control detecting operation at every bit basis, securely performs the detecting operation only at specified bits to exactly find a cause of the defect. With the malfunction securely determined, the defective components or parts are removed in the form of driving substrate, at the same time the cause of malfunction is fed back and thus reduces generation of such malfunction. The present invention also uses an electrical method, which enables rapid measurement.
SUMMARY OF THE INVENTION
To solve the problem above described, an inspection circuit for a light valve device according to the present invention is provided in a light valve device which is comprised of; a driving substrate which includes, driving electrodes arranged in a matrix form, switching elements for driving the driving electrodes, pixels formed of electrooptic material driven by the switching elements, and a driving circuit for driving and exciting control signal lines and image signal lines depending on predetermined signals, both the control signal lines for controlling turn ON/OFF of each switching element and the image signal lines for transferring image display signals being connected to the switching elements; a counter substrate opposingly arranged on the driving substrate; and an electrooptic material layer arranged between the driving substrate and the counter substrate. The inspection circuit for the above-described light valve comprises a driving circuit operation confirmation circuit in which the signal lines are connected with switching devices formed of three terminals, a first terminal of the three terminal elements is connected to signal lines, a second terminal is connected to inspection signal output line, and a third terminal is a terminal for controlling connection/disconnection of the first terminal and the second terminal.
Switching elements capable of performing connection/disconnection of input from signal lines to detectors are provided to detect signal levels of the signal lines during input or after completion of the input. In addition, the timing of signal potential detection of the signal lines is controlled to independently detect each operation of the entire signal lines.
REFERENCES:
patent: 4676761 (1987-06-01), Poujois
patent: 5262720 (1993-11-01), Senn et al.
patent: 0143039 (1985-05-01), None
patent: 0480819 (1992-04-01), None
patent: 9211560 (1992-07-01), None
IEEE Journal of Solid-State Circuits, vol. 25, No. 2, Apr. 25, 1990, New York, pp. 531-538, I. De Rycke et al., “2-MHz clocked LCD Drivers on Glass”.
Sakurai Atsushi
Takahashi Kunihiro
Takasu Hiroaki
Yamazaki Tsuneo
Adams & Wilks
Brier Jeffery
Seiko Instruments INC
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