KR19980014351A - A keystone correction circuit using a lookup-table - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for correcting image distortion in the form of a keystone which may occur depending on the relative position of a device in relation to a projection type image display device.

SUMMARY OF THE INVENTION The present invention has been made to solve the disadvantage that the conventional keystone correction circuit has to repeatedly control the image correction function for each image line. The image correction data includes a lookup table in which the image correction data is stored in advance to avoid repetition of the same operation The control cycle is reduced considerably and at the same time the control of multiple functions is made possible by a single microcomputer. Further, by making the control signal more efficient, the keystone distortion correction can be performed more accurately and effectively.

Description

A keystone correction circuit using a lookup-table

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image distortion correction circuit relating to a projection type image display apparatus, and more particularly to a circuit for correcting image distortion in the form of a keystone by using a lookup- will be.

Generally, an image display apparatus is classified into a direct view type image display apparatus and a projection image display apparatus according to a display method.

The direct-view type image display device has a CRT (Cathode Ray Tube) or the like. Although such a CRT image display device has good image quality, it has problems such as an increase in weight and thickness and an increase in price as the screen size increases. .

Examples of the projection type image display device include a liquid crystal display (LCD), a digital micromirror device (DMD), and an actuated mirror array (AMA). Since a liquid crystal display (LCD) can be made large in size and thin, it is possible to reduce the weight of the LCD. However, since the LCD has a large loss of light due to polarization and a thin film transistor for driving the LCD is formed for each pixel, ), The efficiency of light is very low.

In order to solve the above problems, an AMA device having excellent light efficiency and simple manufacturing process has been developed.

The AMA image display device is configured to adjust an optical path through such a mirror surface (hereinafter, referred to as an actuator) by using a principle that an electric field is generated and deformed by a voltage applied thereto by a deformed portion made of a piezoelectric or electrostrictive ceramic material And optical path adjustment means for projecting on a screen.

A projection type image display apparatus using an AMA separates white light emitted from a light source into red (R), green (G) and blue (B) lights and then drives the light by an optical path adjusting device including actuators . That is, the optical signals for image display are reflected on mirror surfaces that are tilted at a predetermined angle, respectively, as the actuators are individually driven, thereby changing the light path and controlling the amount of light and projecting the light onto the screen. As a result, an AMA image is displayed on the screen of the projection-type image display apparatus.

In the AMA image display apparatus, the optical path adjusting means, which is a main technique, faces a screen on which an image is displayed and its relative position at which the optical path adjusting means is installed is important. In this regard, As follows.

FIG. 1 is a view showing an installation state of the AMA optical path adjusting means in relation to the image display screen, FIG. 2 is a view showing a distorted form of the projected image on the screen according to different installation states of the AMA light path adjusting means shown in FIG. FIG.

With respect to the first aspect, when the apparatus 100 is installed in the center so that the lens optical axis of the AMA image display apparatus 100 is perpendicular to the screen, a correct image is displayed on the screen SC, In most cases, the AMA image display device 100 is used to be movable rather than fixed.

As a result, the image reproduced on the screen SC has a trapezoidal shape (see FIG. 2B) with a longer upper side (FIG. 2A) and a longer lower side (Also referred to as keystone distortion) can not be avoided.

2B shows the distortion of the image projected on the screen when the AMA image display apparatus 100 is installed at a relatively low position with respect to the screen, The distortion of the image picked up on the screen is shown.

At this time, the rectangle shape indicated by the solid line in the drawing is a normal image reproduced on the screen as a comparison standard when the AMA image display device is installed at the center position.

In the conventional AMA projection image display technology, inverse image correction is performed by performing sequential image compression on a distorted image that may occur depending on the installation position of the AMA image display device 100 discussed above A method has been proposed.

An image correction method of such a projection type image display apparatus will be described below with reference to FIG.

FIG. 3 is a schematic block diagram of a general keystone image distortion correction circuit.

3, reference numeral 1 denotes a microcomputer for controlling various functions of the AMA image display apparatus and controlling the keystone distortion correction function.

The microcomputer 1 includes a plurality of input / output ports, and includes a KEY port for receiving a key input of a user to control the image display device, a Remocon port for receiving a user's remote control command, H-SYNC, and V-SYNC port for providing the image data to be scanned, and control data over the image display function including data concerning the number of pixels to be compressed on each scanning line in the correction of the distorted image, An enable port w-ld for enabling control of the digital control ports d0-d7 by enabling a digital control port d0-d7 serving as a signal, a latch 1 2 described later, Enable ports (r-ld1, r-ld2) that enable latch 2 (3) and latch 3 (4) described below to determine the start position and end position of each display line of the image, Reset counter Etc. port (reset) for generating a reset signal for Pointing and is displayed on the drawings.

Reference numerals 2, 3, and 4 denote latch 1, latch 2, and latch 3, respectively, which temporarily store control signals output from the microcomputer 1 and provide them.

5 is a counter for receiving the clock signal Clk and the H-DSP signal and outputting a counter clock signal corresponding to the image display period of the unit scan line, 6 is a counter for receiving the image display control data d0-d7 ) Through the latch 1 (2), and is enabled by a clock pulse to output image compression data in a first-in first-out form.

Reference numeral 7 denotes a latch circuit for latching the image display control data d0-d7 provided when the latch 2 (3) is activated by the latch enable signal r-ld1 for determining the start point at which the image is to be displayed, And a comparator 8 for comparing the counter clock signal outputted from the latch 3 (4) with the counter enable signal r-ld1 for determining the end of image display (D0-d7) provided when the display data is activated by the counter 5 and the output data of the counter 5, and outputs the corresponding data if they are the same.

Reference numeral 9 denotes a first-in first-out F / F buffer for delaying the counter clock signal output from the counter 5 by a predetermined time, and is initialized by a reset signal (reset) provided from the microcomputer 1. [

Reference numeral 10 denotes a first-in first-out F / F buffer for receiving a signal from the first comparator and / or the second comparator and controlling reading of the line memory.

In the preceding projection image correction system comprising the main constituent elements described above, the user sees the keystone image distortion visually while viewing the screen and manipulates the key of the main panel or the remote control key to correct the keystone image distortion to the microcomputer 1 When the control command is issued, the microcomputer 1 provides the line compression data for correcting the keystone image distortion to the latch 1, the latch 2 and the latch 3 (2, 3, 4) to perform the image compression operation for the purpose of distortion correction .

When an image has an image aspect ratio of 640 pixels X 480 lines and compresses an image in 32 steps, 15 lines of image display data are grouped into one group, and the same image compression data is applied Receive.

Therefore, the conventional AMA image correction system performs a predetermined compression operation on the first line of the display image, and then repeatedly performs the same compression operation on each line from the second line to the fifteenth line until the new image compression data And then proceeds to the second step of correcting the image data of the 16 < th >

Since the microcomputer 1 must continuously issue a control command for repeatedly performing such a compression operation, it is difficult to control other functions, and it is also difficult to control other functions such as KEY, Remocon, H-SYNC, V- SYNC, d0-d7, , r-ld1, r-ld2, and reset, the number of ports assigned to the keystone image correction function is large. Therefore, it is difficult to use the port for controlling other functions.

Therefore, the present invention avoids repetition of the same image compression operation and reduces the control cycle of the microcomputer allocated to such an operation, thereby providing a control microcomputer in the A / V circuit section and the keystone distortion correction section in the image correction system according to the related art And it is an object of the present invention to overcome the disadvantage that each control has to be executed and control multi-function with one microcomputer.

It is another object of the present invention to more accurately and effectively correct keystone distortion caused by positional variation of an AMA image display apparatus.

1 is a diagram illustrating an installation state of an AMA image display apparatus;

2 (a) and 2 (b) illustrate a display image projected at position A in FIG. 1, and FIG. 2 (b) and FIG.

FIG. 3 is a schematic block diagram of a prior art AMA keystone image distortion correction circuit; FIG.

FIG. 4 is a schematic block diagram of an AMA keystone image distortion correction circuit according to the present invention; FIG.

FIGS. 5A and 5B illustrate signal states of a microcomputer and a preset counter when correcting a keystone image distortion according to the present invention, wherein FIG. 5A and FIG. 5B illustrate an image correction, and FIGS.

6 is a diagram illustrating signal states of first and second comparators in a keystone image distortion correction according to the present invention;

* Symbol Description for Major Parts of Drawings *

100: AMA image display device 1, 40: Microcomputer

2, 12: Latches 13, 13: Latch 2

4,14: latch 35,15: counter

6, 16: preset counter 7, 17: first comparator

8, 18: second comparator 9, 10, 19, 48, 50: F / F buffer

41: field counter 42: program section

43: remote transmitting / receiving unit 44: up / down counter

45, 46, 47: Lookup table SC: Screen

According to an aspect of the present invention, there is provided a method of correcting a keystone image distortion using a memory storage device, the method comprising: a lookup- table), and when the video signal compression of the first line is performed by receiving the user's image correction control command, when the remaining plurality of lines included in the same step are compressed (for example, 14 out of 15) Is used to repeatedly use the compressed data stored in the memory.

In addition, according to the present invention, the count operation is started by inputting the H-SYNC signal in the microcomputer of the keystone distortion correction circuit of the present invention, and the field counter for terminating the count operation by inputting the V-SYNC signal, And the V-SYNC signal and the H-SYNC signal, which have been executed based on only the -SYNC signal, are used together to compensate the control of the keystone distortion.

FIG. 4 is a block diagram showing a schematic configuration of a keystone distortion correction circuit according to the present invention, which is described above with respect to a projection type image display apparatus.

Hereinafter, the configuration and operation effects of the present invention will be described in detail with reference to FIG.

In FIG. 4, reference numeral 40 denotes a microcomputer for controlling a plurality of other image display controls including an image distortion correction function and an audio / video function in a keystone form that can be caused by a positional variation of the image display device.

Reference numeral 41 denotes a field counter for starting the counting operation by the horizontal synchronizing signal H-SYNC and clearing a value accumulated by the vertical synchronizing signal V-SYNC and generating a key H-SYNC at this time, Reception unit 42 for receiving a remote control command signal of the user and providing the control signal to the corresponding function processing unit 42, and 42 for transmitting the keystone correction function control signal through the operation of the panel key of the user or the operation of the remote control key, And a keystone distortion correction program section 41 for activating the field counter 41 and generating control signals such as keystone on / off and top / bottom correction, , 42, and 43 constitute the microcomputer 40.

4, reference numeral 44 denotes a counter for counting the number of pulses of the Key H-SYNC signal, which is enabled by the top / bottom signal provided from the program unit 42 and inputted from the field counter 41, And an up / down counter configured to be reset by a vertical synchronization signal (V-SYNC).

Reference numerals 45, 46, and 47 are predetermined storage elements or memories, for example, image compression data of 32 stages, which are sequentially stored in advance, and are look-up tables that can be utilized for correction of keystone image distortion.

Functional portions similar to the constituent blocks of the conventional keystone image distortion correction circuit shown in FIG. 3 are indicated by adding an Arabic numeral '1' before the reference numerals of FIG.

Reference numerals 12, 13, and 14 denote latch 1, latch 2, and latch 3 elements for temporarily storing input data input through the input terminals and providing the output data to the output terminals. Reference numerals 48 and 19 denote data to be transmitted in a first- 15 is a counter that counts the clock signal clk through the F / F buffer 48 and initializes a count value to '0' by a reset signal to perform a new count operation.

In the figure, reference numeral 16 denotes a latch circuit which loads the image correction data latched in the latch 1 (12) on the basis of the H-SYNC signal with reference to the H-SYNC signal and counts the clk signal. At this time, when the count value reaches a predetermined set value , And a preset counter adapted to generate an output signal.

17 and 18 respectively compare the count value of the counter 15 with the image correction data provided through the latches 2 and 13 and the latch 3 14 to output the same to the F / 1 comparator and a second comparator.

Reference numeral 50 denotes an F / F buffer for receiving a signal from the first comparator 17 or the second comparator 18 and controlling the line memory to be readable.

In the keystone image distortion correction circuit of the present invention configured as described above, the distortion of the image displayed visually by the user is detected and the image correction instruction is issued to the program section 42 through the remote transmission / reception section 43 by operating the remote control key, A direct image correction command is issued through the body panel key input.

The program unit 42 not only generates a keystone on / off signal which is a signal for enabling keystone correction by reading such an image correction command and a top / bottom signal which is a signal for determining a correction direction according to the distortion of the image, , And activates the filter counter 41 to provide a horizontal synchronizing signal (Key H-SYNC) on a field basis.

At this time, if the AMA image display device is located at a relatively high position with respect to the screen, the top / bottom signal becomes 'Top state' and the top / bottom signal is referred to The up / down counter 44 functions as an up counter when the enable / down counter 44 is enabled, and the bottom / bottom signal becomes the bottom state when the enable / do.

On the other hand, the lookup tables 45, 46, and 47 receive the output of the up / down counter and read the multistage image distortion correction data stored in advance in the lookup table, 1 (12), the latch 2 (13), and the latch 3 (14).

The latch 1 (12), latch 2 (13), and latch 3 (14) parts in which the image distortion correction data are temporarily stored as described above latch the data stored on the basis of the H-SYNC signal as the next stage and deliver it.

The line correction data stored in the latch 1 (12) is latched to the preset counter 16. The preset counter 16 counts the clk signal to perform image data correction with respect to one line of the keystone-distorted image, And generates an output signal for controlling the write enable terminal of the line memory for recording the image display data when the latched data value is reached.

The line comparator 17 latches the line start point data stored in the latch 2 13 by the keystone on / off signal of the program section 42 of the microcomputer 40 When the two data are the same, the F / F buffer 50 generates an output pulse for controlling the reading of the line memory corresponding to the start position of the image display line .

Similarly, the line endpoint data stored in latch 3 14 is latched into second comparator 18 and the second comparator is similarly enabled by a keystone on / off signal to latch data and counter 15) When the output data is the same, the F / F buffer 50 generates an output pulse for controlling the line memory reading corresponding to the end position of the image display line.

The counter 15 counts the clk signal input through the F / F buffer 48 and provides the counting data to the first comparator and the second comparator, as well as to the F / F buffer 19 to output the H_DSP signal Which is a signal delayed by a predetermined time.

This time delay takes into consideration the driving time required for driving the optical path adjusting apparatus by using the image display data of the line memory.

According to the operation of each of the above-described components, the distorted image is divided into a plurality of stages, and the same image data correction operation can be repeatedly performed with only one microcomputer control command for a plurality of lines included in each compression step. Such image data correction can be made at the starting point and the display end point.

FIGS. 5A and 5B are timing diagrams showing states of control signals provided from the microcomputer 40 and an output signal state of the preset counter 15, respectively, which control execution of correction of a keystone image distortion according to the present invention.

5A and 5B illustrate the case where the position of the AMA image display apparatus of the present invention is relatively upper, and FIG. 5B illustrates a case where the position of the AMA image display apparatus is relatively lower.

FIG. 6 is a timing diagram showing output signal states of the preset counter 16 and the first and second comparators 17 and 18 when the keystone image distortion correction is executed.

Hereinafter, the keystone correction function of the present invention will be described in detail with reference to FIGS. 4, 5 and 6 attached hereto.

As an example, assume that the position of the AMA image display device is higher than the screen relatively to the screen (Top state). Further, the image reproduced on the screen is set to a general 640 pixel X 480 line. At this time, the visible image distortion observed by the user becomes a trapezoidal shape (Top keystone) longer in the lower side than in the upper side, and it can be easily seen that a larger number of pixel data compression is required for a later line in sequential line correction.

The correction of the image line is performed in 32 steps, and 15 lines (480/32) constitute one group in one group, and the same number of image data compression is performed for each line, and so on.

5A, the program unit 42 in the microcomputer 40 generates a Top / bottom signal as a 'Top state' and a Keystone on / off signal as a '1', and simultaneously enables a field counter 41 .

The field counter 41 is reset with reference to the V-SYNC signal and counts pulses of the H-SYNC signal.

The up / down counter 44 operates as an up counter according to the top / bottom signal of the program unit 42, upwardly counts the Key H-SYNC signal pulse, and generates lookup tiers 45 and 46 , 47 are designated.

Each of the lookup tables 45, 46 and 47 stores each keystone image distortion correction data stored at a specified address in a latch 1 (12), a latch 2 (13), and a latch 3 (14) Remember.

The three latch elements 12,13,14 are latch enabled by the same H-SYNC signal as that provided to the field counter 41, and the latch 1 12 then sends the data to the preset counter 16 Latch.

The preset counter 16 provides the data stored in the address of the look-up table 45 for every H-SYNC pulse. At this time, the signal output state of the field counter 41 becomes '0' And the same output is generated until the data of the new address is latched.

The latch 2 13 latches the data to the first comparator 17 and the first comparator 17 compares the latched data with the data provided from the counter 15. If the two data are the same, Level. The F / F buffer 50 receiving this signal outputs a signal (read pulse) for controlling reading of the line memory to determine the start position of the image display line.

Similarly, the latch 3 14 latches the data to the second comparator 18 and compares it with the second comparator 18 and then falls to the '0' level in the same case, Outputs the line memory read control signal (read pulse) to determine the end position of the image display line.

The counter 15 counts the clock signal input through the F / F buffer 48 and delays it by 40 clocks in the F / F buffer 19 of the next stage to output the DLY H-DSP signal.

5b, the top / bottom signal is 'bottomed' by correcting the keystone distortion that occurs when the position of the AMA actuator is down, and the up / down counter 44 is connected to the down counter Except that the data reading and transmission are sequentially performed starting from the end address of the lookup tables by operation, so that the description will be omitted.

As described above, according to the present invention, the conventional projection image correction technique repeatedly performs the same correction control on a plurality of image lines, And corrects the keystone distortion by using the V-SYNC signal as a reference signal as well as H-SYNC, thereby effectively solving the drawbacks of the prior art.

As a result, according to the present invention, not only the number of ports of the microcomputer used for image correction of the projection type image display device can be greatly reduced, but only a part of the control cycle can be assigned to the image correction, so that other functions can be controlled. Also, since the present invention does not control based on the width of the H-SYNC signal as in the conventional method, correct control is performed and keystone distortion correction is effectively performed.

Claims (2)

A circuit for correcting a keystone image distortion associated with a projection type image display apparatus, A field counter 41 for starting the counting operation based on the horizontal synchronizing signal and initialized with reference to the vertical synchronizing signal, a predetermined control program section 42 for correcting the keystone image distortion, and a remote transmitting / A microcomputer 40 for controlling image distortion correction and other image display functions, An up / down counter 44 operating as an up-counter or a down-counter according to a control signal of the program unit 42, Tables 45, 46, and 47 in which image correction data for performing multistage image correction including a plurality of image lines are sequentially stored in advance, Latch 1, latch 2, and latch 3 elements 12, 13, and 14 for temporarily storing and latching data provided from the lookup tables 45, 46, and 47, A counter 15 counting the clock signal and initialized by a reset signal input, A preset counter 16 for loading data of the latch 1 (12) and generating an output signal when the count reaches this value, A first comparator 17 for comparing the data of the latch 2 13 and the counted value of the counter 15 and outputting them when they are the same, A second comparator 18 for comparing the data of the latch 3 14 with the counted value of the counter 15 and for outputting the same when they are the same, F / F buffers 48 and 19 for providing input data in a first-in first-out form and F / F buffers 48 and 19 for controlling the line memory reading in response to signal inputs of the first comparator 17 or the second comparator 18. [ / F buffer (50). The image processing apparatus according to claim 1, wherein the lookup tables (45, 46, 47) are arranged in a group of 15 lines (480/32) so that the same number of image data compressions Up table 46 stores the line start position data, and the look-up table 47 stores the line end position data. The look-up table 45 stores line correction data, Is stored.