JP4376764B2 - Stereoscopic image display device - Google Patents

Description

  The present invention relates to a stereoscopic image display device using a liquid crystal display device having a plurality of gate lines and a plurality of source lines, and in particular, a time-division stereoscopic image display that performs stereoscopic display by alternately displaying left and right parallax images. Relates to the device.

  For example, as shown in FIG. 1 of Patent Document 1, a conventional time-division liquid crystal stereoscopic image display device includes two light sources that respectively focus on the right and left eyes of an observer, and the liquid crystal display panel is on the right side. When displaying a parallax image for the eye, the right eye light source is turned on in synchronization with it, and when the left eye parallax image is displayed, the light source for the left eye is turned on in synchronization with it, and the left and right parallax images are displayed. Are alternately displayed to display a stereoscopic image. In this device, if two different images are used instead of the left and right parallax images, two different images can be displayed depending on the viewing direction.

JP 2001-66547 A (FIG. 1)

  A conventional time-division liquid crystal stereoscopic image display device has the following problems when used in a mobile phone, for example.

  That is, in a mobile phone, the input rate of image input data is as low as about 24 times per second (frames) due to limitations of wireless communication capability, power consumption, and CPU (Central Processing Unit) processing speed, and image flickering occurs. There was a problem.

  In order to perform display without generating flicker in the stereoscopic image display device, it is desirable to display the left and right parallax images at a rate close to 60 times per second, and images at a rate close to 120 times / second in total on the left and right It is desirable to display.

  However, in order to perform such high-speed display, there is a problem that the response speed of the liquid crystal is insufficient and a ghost due to the response delay of the liquid crystal occurs.

  In addition to the above-described problems, in a liquid crystal stereoscopic image display device that employs an illuminating device that blinks all over the surface in synchronization with the frame, the gate line is sequentially selected and the voltage is applied to the pixel. Since the time from when the liquid crystal starts to respond until the lighting device is turned on varies depending on the gate line in the gate scan direction, the luminance is uneven in the gate scan direction, and the response of the liquid crystal is insufficient depending on the location. There was a problem that occurred.

  The present invention has been made to solve the above-described problems, and is caused by a response delay of liquid crystal in a time-division type stereoscopic image display device that performs stereoscopic display by alternately displaying left and right parallax images. It is an object of the present invention to provide a stereoscopic image display device that prevents the occurrence of ghosts and prevents the occurrence of luminance unevenness and ghost intensity unevenness.

  The stereoscopic image display apparatus according to claim 1 of the present invention has a plurality of gate lines and a plurality of source lines, and displays a right-and-left parallax image data alternately on the left and right to perform a stereoscopic display to perform a stereoscopic display. An image display device, a liquid crystal display unit, an illumination device having a right eye light source and a left eye light source that alternately flash to illuminate the entire surface of the liquid crystal display unit in synchronization with a frame, and the right eye image A memory for storing data and the image data for the left eye, and each of the image data for the right eye and the image data for the left eye to be displayed on the same gate line of the liquid crystal display unit from the memory by one gate line Read out one by one, and with respect to the right-eye image data and left-eye image data for one gate line read out, either the left or right is set as the latest input image data, and the other The previous input image data displayed one field before is used for the gradation value compensation processing in the liquid crystal display based on the latest input image data, and the gradation value compensation processing is performed as described above. In each of the plurality of gate lines, the gradation value is compensated for each of the plurality of gate lines in accordance with the time from the start of the response of the liquid crystal to the time when the light source of the lighting device is turned on. Data for field image display.

  According to the stereoscopic image display device of the first aspect of the present invention, the immediately preceding input image data is used for the gradation value compensation processing in the liquid crystal display based on the latest input image data, and the liquid crystal in each of the plurality of gate lines. Since the gradation value is compensated for each of the plurality of gate lines in accordance with the time from the start of response to the time when the light source of the lighting device is turned on, the data for image display of the latest field to be displayed next is obtained. In a stereoscopic image display device including an illuminating device that simultaneously flashes on the entire surface of the liquid crystal display unit in synchronization with the frame, it is possible to prevent occurrence of luminance unevenness and ghost intensity unevenness in the gate scan direction.

<Embodiment>
<A-1. Device configuration>
An embodiment of a stereoscopic image display device according to the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing a device configuration when the present invention is applied to a mobile phone capable of displaying a stereoscopic image, and is a configuration common to Embodiment 1 and Embodiment 2 described later.

  A stereoscopic image display device 100 illustrated in FIG. 1 includes a communication device module 1 and a display module 2.

  The communication device module 1 includes a communication device unit 11, a CPU unit 12, and a power source 15 such as a battery. The CPU unit 12 includes a decoder 131, an encoder 13, and a video random access memory (VRAM) 14 that is a video memory.

  The display module 2 includes a backlight blinking driver 20, a control circuit 21, a gate driver 26, a source driver 27, and a liquid crystal display panel 28. The control circuit 21 includes a timing controller 22, a frame memory 23, a decoder 24, a DAC (digital / digital). An analog converter) 25 and an arithmetic unit 29.

  The liquid crystal display panel 28 includes a liquid crystal display unit 281 that alternately displays left and right parallax images, and a light source (not shown) that focuses the left eye when displaying an image for the left eye in synchronization with the left and right parallax images. And when displaying the image for right eyes, it has two types of light sources of the light source (not shown) which condenses on the right eye.

<A-2. Basic operation>
Next, the basic operation of the stereoscopic image display apparatus 100 will be described.
The communicator unit 11 of the communicator module 1 receives the stereoscopic image data composed of the right-eye image and the left-eye image from the sender, gives it to the decoder 131 of the CPU unit 12, and decodes it. Right-eye image data and left-eye image data are obtained. Here, the frame input rate of the input image data is limited by the processing capacity and communication speed of the CPU, and here it is 24 times per second on the left and right.

  In the CPU unit 12, the right eye image data and the left eye image data decoded by the decoder 131 are given to the encoder 13, and the encoder 13 performs processing such as run length encoding, Huffman encoding, and discrete cosine conversion again. After each data compression encoding, it is recorded in the VRAM 14 together with data decoding parameters.

  Here, the image data for the right eye and the image data for the left eye displayed on the same display position, that is, on the same gate line on the liquid crystal display panel 28, are compressed as one group and recorded in the VRAM 14 as compressed image data. To do. At this time, if a common parameter is used as a compression / decoding parameter for the left and right image data, the amount of data can be reduced.

  Next, the compressed image data recorded in the VRAM 14 is transferred to the frame memory 23 of the display module 2 together with the data decoding parameters and recorded.

  In the display module 2, it is desirable to display the left and right images at a rate of at least 40 times per second in order to suppress flicker, and the left and right images given 24 times (frames) per second in synchronization with the clock of the timing controller 22. By displaying the input parallax image data alternately and twice in each field within one frame period, each of the left and right images is displayed at a rate of 48 fields / second, for a total of 96 fields / second flicker. Display images without

  Here, in order to suppress flicker, at least each of the left and right images only needs to be 40 fields / second, and display of the left and right images at 48 fields / second satisfies this condition.

  When the right eye image is displayed, the recording data is read from the frame memory 23 by reading the right eye image data one gate line at a time and using the decoding parameters recorded in the frame memory 23. To obtain image data for the right eye.

  The decoded right-eye image data is stored in a line memory (not shown). The data stored in the line memory is sequentially D / A converted in the DAC 25 and stored in a latch circuit (not shown) of the source driver 27. The clock from the timing controller 22 and the gate line selection by the gate driver 26 are performed. Synchronously, it is applied as a gradation voltage to the pixels on the gate line. The above operation is sequentially repeated for each gate line to display the right eye image field.

  Next, the same processing is performed on the left-eye image data to display the left-eye image field, and the same right-eye and left-eye image fields are repeatedly displayed, so that a pair of left and right input image data is displayed. Are alternately displayed in two fields for a one-frame image display.

  In the above description, when the left and right image data is compressed, an example in which each image data is compressed as complete parallax image data and recorded in the VRAM 14 has been described. For example, right-eye image data is treated as complete parallax image data, The left-eye image data may be compressed and recorded only for the difference from the right-eye image data.

  In this case, the image data for the right eye and the image data for the left eye displayed on the same display position, that is, on the same gate line on the liquid crystal display panel 28, are compressed as one group with the same parameters, and used for the right eye. The image data for the left eye is recorded in the VRAM 14 for the difference between the image data for the left eye and the image data for the right eye.

  Further, the memory reading from the frame memory 23 is performed by reading the compressed image data for the right eye and the compressed image data for the left eye displayed on the same gate line together and decoding parameters recorded in the frame memory 23. And the right eye image data and the difference data between the right eye image and the left eye image are obtained.

  When displaying the right-eye image, the right-eye image data is stored in the line memory as it is, and when displaying the left-eye image, the difference data is added to the right-eye image data to the left. The image data for the eye is stored in the line memory.

  The above description has been made on the assumption that the right eye image data and the left eye image data decoded by the decoder 131 are compressed again by the encoder 13, but the data is compressed again in this way. In other words, the storage capacity of the image data storage memory such as the frame memory 23 can be reduced. In other words, by compressing the received data again, the storage capacity of the image data storage memory can be reduced. An inexpensive stereoscopic image display device can be obtained. However, if the image data storage memory has a sufficient storage capacity, or if there is no problem in cost even if a memory with a huge storage capacity is prepared, it is not necessary to compress the received data again. There is no need for compression encoding or decoding processing of the received data.

<A-3. Prevention of ghost and outline blur>
In the method of displaying stereoscopic images by alternately displaying left and right parallax images, the right-eye image and the left-eye image are displayed at positions slightly shifted in the left-right direction even if they are the same display target. Is done. This is a parallax image, but when displaying a display object whose position is shifted in this way alternately, even if it is a still image, switching between a right eye image and a left eye image is performed as in the case of a moving image. Each time, a change in luminance is required at each pixel, and if the response speed of the liquid crystal is insufficient, ghosts and blurring of the outline may occur.

  In the stereoscopic image display device 100, as described above, the number of times of display in one frame is doubled to prevent flicker, so that the frame display speed is increased and the liquid crystal response speed is likely to be insufficient.

  Therefore, the input image data of the latest field is compared with the gradation value of the image data of the field displayed immediately before, and the latest field to be displayed next from the previous field as the gradation voltage for image display of the latest field. By creating a gradation voltage emphasizing the gradation change to be applied to the liquid crystal display panel 28, the response speed of the liquid crystal with respect to the gradation change is accelerated, and the response delay is compensated.

Hereinafter, compensation processing for accelerating the response speed of the liquid crystal with respect to a change in gradation and compensating for a response delay will be described.
Specifically, as a means for creating a gradation voltage in which gradation change is emphasized, a gradation value conversion table as shown in FIG. 2 is prepared in advance in a predetermined memory (not shown). The calculator 29 shown in FIG. 1 creates an optimum gradation voltage for changing from the current liquid crystal display state to the gradation to be displayed next.

  As shown in FIG. 2, the gradation value conversion table includes gradation values (0 to 255) of image data of the current frame (latest field) and gradation values (0 to 255) of image data of the previous frame (previous field). ) Is set to a gradation value to be given to the liquid crystal display panel 28, and a gradation voltage corresponding to the gradation value is recorded as output data.

  For example, when the gradation value of a pixel in the previous field is “1” and the gradation value to be displayed on the same pixel in the latest field is “2” on the image data, based on the conversion table, The liquid crystal display panel 28 outputs a gradation voltage corresponding to the gradation value “3”. Thus, by setting the gradation voltage that is actually applied to the liquid crystal display panel 28 to be higher than the gradation value on the image data, it is possible to compensate for a delay in the response of the liquid crystal. explain.

<A-3-1. Tone value compensation procedure>
The above-described gradation value compensation is performed using the gradation value conversion table before the decoded left and right image data is stored in the line memory.

Specifically, the process proceeds according to the following procedure.
As described above, in the encoder 13, the right-eye image data and the left-eye image data displayed on the same gate line are each grouped as one gate line, compressed with the same parameters, and recorded in the VRAM 14. To do.

  The left and right compressed image data is transferred to the frame memory 23 of the display module together with the decoding parameters. From the frame memory 23, the compressed image data for the right eye and the compressed image data for the left eye to be displayed on the same gate line are read out in pairs, and decoded by the decoder 24 to complete complete image data for the right eye and image data for the left eye. Get.

  Then, before the image data for the right eye and the image data for the left eye are stored in the line memory (not shown), the arithmetic unit 29 uses the gradation value conversion table to compensate the gradation value. At this time, the left-eye image data is used as the image data of the previous field in order to compensate the gradation value of the right-eye image data, and the right-eye is used in order to compensate the gradation value of the left-eye image data. The image data can be used as the image data of the previous field.

  That is, when the input image data is a moving image, when the compressed image data recorded in the VRAM 14 is transferred to the frame memory 23, the compressed image data for one field for the right eye is first written in the frame memory 23, and thereafter The compressed image data for one field for the left eye is written with a predetermined time difference. This time difference is determined by using the left-eye image data displayed immediately before in the frame memory 23 in order to use it as left-eye image data at the same display position that is read as a pair with the right-eye image data when decoding the image data. It is for leaving it in.

  As a result, the left-eye image data displayed immediately before and the latest right-eye image data are read as a pair, and the left-eye image data displayed immediately before is used as the image data of the previous field. As a result, the tone value of the right-eye image data can be compensated, so that tone compensation for accelerating the response speed of the liquid crystal can be executed without delay.

  Note that, after reading out one field of the compressed image data for the right eye from the frame memory 23, the compressed image data for the left eye is written in the frame memory 23 and the data is updated. In this case, the previously input compressed image data for the right eye for one field is used as the image data for the previous field.

  Here, when the input image data is a moving image, the timing of writing the compressed image data to the frame memory 23 and the reading from the frame memory 23 are shown in FIG.

  In FIG. 3, the compressed image data for the right eye for n lines and the compressed image data for the left eye for n lines are written in the frame memory 23 during one frame period and displayed on the same gate line. The state in which the compressed image data for the right eye and the compressed data for the left eye are read in pairs is schematically shown.

  In FIG. 3, the compressed image data for the left eye is input first and the compressed image data for the right eye is input later, but the input order may be reversed.

<A-4. Prevention of uneven brightness and ghost>
<A-4-1. Operation of simultaneous flashing method on the entire LCD panel>
Here, the configuration of the illumination device of the liquid crystal display panel 28 will be described with reference to FIG.
As shown in FIG. 4, the liquid crystal display panel 28 has a lighting device called a backlight 50. The backlight 50 includes light sources 52 a and 52 b such as LEDs, and a light guide plate 51 that guides light from the light sources to the liquid crystal display unit 281. The light guide plate 51 has a size corresponding to the size of the entire surface of the liquid crystal display unit 281 and is made of a resin such as plastic or acrylic and has translucency.

  Further, the same number of light sources 52a and 52b are arranged on two opposite sides of the liquid crystal display panel 28, respectively. Here, the light source 52a disposed at the right edge toward the liquid crystal display panel 28 is referred to as a left eye light source, and the light source 52b disposed at the left edge is referred to as a right eye light source.

  The backlight 50 of the liquid crystal display panel 28 is controlled to blink simultaneously on the entire surface of the liquid crystal display unit 281 in synchronization with the frame.

  Here, the blinking control of the backlight 50 is controlled by the backlight blinking driver 20.

  That is, the timing signal from the timing controller 22 to the gate driver 26 is supplied to the gate driver 26. This timing signal is also supplied to the backlight blinking driver 20, and the light sources 52a and 52b are combined with the gate line scan. Blinks.

  More specifically, when scanning a gate line based on right-eye image data, only the right-eye light source 52b is turned on, and when scanning a gate line based on left-eye image data. Control is performed so that only the light source 52a for the left eye is lit.

  In displaying a stereoscopic image, when the above-described simultaneous flashing method of the liquid crystal display panel as described above is employed, the selection time of the gate line, the number of gate lines, and the response characteristics of the liquid crystal must be taken into consideration. Therefore, the response characteristics of the liquid crystal will be described with reference to FIG.

  FIG. 5 is a conceptual diagram showing the relationship between the backlight lighting period for stereoscopic image display and the response characteristics of the liquid crystal, with the horizontal axis representing time and the vertical axis representing liquid crystal transmittance. .

  In the liquid crystal display panel 28 having N gate lines, the liquid crystal display unit 281 has a uniform transmittance L1 on the entire surface as a left eye image, and a transmittance L2 (L1 <L2) on the entire surface as a right eye image. Explained.

  As shown in FIG. 5, the liquid crystal display panel 28 has a transmittance for displaying a left eye image in the entire liquid crystal display unit 281 until time t <b> 0 when the lighting period of the left eye light source ends in the left eye image display period. L1 and the liquid crystal has a luminance corresponding to the transmittance L1. Note that the luminance of the liquid crystal is represented by multiplication of the transmittance of the liquid crystal and the brightness of the backlight.

  From time t0, in order to display a right eye image, an image signal corresponding to the liquid crystal transmittance L2 is sequentially applied from the first gate line by gate scanning. After the gate scan is completed, the right eye light source is turned on for a period from time t1 to time t2.

<A-4-2. Compensation for liquid crystal response delay>
When the response of the liquid crystal is slower than the frame display switching speed, the compensation process for compensating for the response delay described above is performed.

  That is, FIG. 2 is used based on the gradation values of the input image data of the latest field (for example, image data for right eye) and the image data of the field that was displayed immediately before (for example, image data for left eye). Using the gradation value conversion table (compensated gradation data) described above, the gradation voltage for image display in the latest field (in this case, the gradation voltage for image display for the right eye) is emphasized ( Higher), the compensated gradation voltage is given to the liquid crystal display panel 28 to accelerate the response speed of the liquid crystal with respect to the gradation change and compensate for the response delay.

  Here, a mechanism that can compensate for the delay in the response of the liquid crystal by emphasizing the gradation voltage will be described below with reference to FIG.

  FIG. 6 is a conceptual diagram showing changes in the response characteristics of the liquid crystal when the voltages applied to the gate lines (gradation voltage) are V2, V3, V4 and V5 (V2 <V3 <V4 <V5). Yes, the horizontal axis represents time, and the vertical axis represents liquid crystal transmittance.

  From FIG. 6, it can be seen that increasing the voltage to V2, V3, V4, V5 increases the response speed in the direction of increasing the transmittance of the liquid crystal, and improves the transmittance in a shorter time.

  Therefore, by increasing the gradation voltage for image display in the latest field higher than the actual image data value, the response speed of the liquid crystal with respect to the gradation change can be accelerated, and the response delay can be compensated.

<A-4-3. About prevention of uneven brightness>
As described above, if a characteristic that can increase or decrease the response characteristic of the liquid crystal by changing the voltage (gradation voltage) applied to the gate line is used, the liquid crystal display panel 28 is generated in the gate scan direction. It is also possible to prevent luminance unevenness.

  FIG. 5 illustrates a case where the response of the liquid crystal is slower than the frame display switching speed in order to explain the luminance unevenness that occurs in the gate scan direction.

  For example, it is assumed that one gate line is selected and the time spent until new data (gray scale voltage) is written to the gate line is the gate selection time, and the gate selection time is tg.

  In this case, a time difference of N · tg occurs between the pixels on the first gate line and the pixels on the Nth gate line before the image data is updated. Therefore, at time t1 in FIG. 5, the pixel on the first gate line has passed (t1-t0) time from the start of the response of the liquid crystal, that is, the liquid crystal transmittance starts to change, but the Nth gate Only (t1−t0−N · tg) passes through the pixels on the line. Therefore, at time t1, the elapsed time after the liquid crystal transmittance of the pixel on the first gate line starts to change and the elapsed time after the liquid crystal transmittance of the pixel on the Nth gate line starts to change. There will be a difference.

  Therefore, when the response time of the liquid crystal is longer than (t1−t0−N · tg), that is, in the case of the response characteristics A and B shown in FIG. 5, the liquid crystal of the pixel on the first gate line at time t1. Even if the response is completed and the transmittance is L2, the pixel on the Nth gate line does not complete the response of the liquid crystal, and the transmittance is a value L3 between L1 and L2.

  In this state, when the light source is turned on during the period from time t1 to time t2, the luminance on the pixels on the first gate line is different from that on the Nth gate line. This phenomenon occurs continuously over the entire surface of the liquid crystal display unit 281 and luminance unevenness occurs in the gate scan direction.

  In order to prevent this, it is desirable that the predetermined transmittance L2 is obtained over the entire area of the liquid crystal display unit 281 in the time from the writing time of new data to each gate line to the light source lighting time.

  Here, paying attention again to FIG. 6, V4 is earlier than the case where the voltage applied to the gate line is V3 to reach the transmittance L2 which is the average transmittance during the effective lighting period. This means that the lighting period of the light source can be shortened by using the voltage V4. FIG. 6 also shows a pattern in which the voltage V2 is applied.

  That is, in FIG. 6, the lighting period of the light source in the case of the voltage V3 is indicated by the symbol b, the lighting period of the light source in the case of the voltage V4 is indicated by the symbol a, and by increasing the voltage applied to the gate line, It can be seen that the lighting period of the light source can be shortened.

  In other words, if the voltage applied to the gate line is increased, the lighting period can be set to an early time after the voltage is applied after the gate line is selected. This means that even if the time from the time to the lighting time of the light source is different, the same transmittance, that is, the same screen luminance can be realized if the applied voltage is changed in each gate line corresponding to each time.

  FIG. 7 shows response characteristics A and B ′ when the applied voltage is changed between the first gate line and the Nth gate line, with the horizontal axis representing time and the vertical axis representing liquid crystal. The transmittance is shown.

  In FIG. 7, as in the case of FIG. 5 described above, the time difference of N · tg between the pixel on the first gate line and the pixel on the Nth gate line is updated before the image data is updated. At time t1, the pixel (characteristic A) on the first gate line has passed (t1-t0) time after the liquid crystal transmittance has started to change, but the Nth gate In the pixel (characteristic B ′) on the line, only (t1−t0−N · tg) has passed.

  However, by applying a voltage higher than that of the first gate line to the Nth gate line so that the response is quickened by the time until the light source is turned on, the response characteristic B ′ rises. Is steeper than the response characteristic A, and is close to the transmittance L2 at time t1 (right-eye light source lighting start time), and is transmitted at time t2 (right-eye light source lighting end time). It can be seen that the transmittance L4 is higher than the rate L2.

  Therefore, the average transmittance of the pixels on the first gate line during the right-eye light source lighting period (defined by the area surrounded by the region indicating the lighting period and the curve of the characteristic A in the figure), and the Nth The average transmittance (defined by the area surrounded by the region indicating the lighting period and the curve of the characteristic B ′ in the drawing) of the pixels on the gate line during the right eye light source lighting period is substantially the same, and the liquid crystal display Luminance unevenness that occurs in the gate scan direction of the panel 28 can be prevented.

  In order to compensate the gradation value so that the applied voltage is changed in accordance with the time from the data writing time to the light source lighting time in each gate line of the liquid crystal display panel 28, the gradation value shown in FIG. A conversion table is required for each gate line.

However, in this method, as the gradation value conversion table, when the number of gradations of each pixel is K bits and the number of gate lines is N, the data amount is N · K · 2 ^2K bits. A large memory capacity is required for the memory to store.

  Here, since the in-plane state of the liquid crystal display panel 28 continuously changes from the first gate line to the Nth gate line, the gradation value conversion table (compensated gradation data) is 1 It is possible to prepare two of the first gate line and the Nth gate line and obtain the gate line between them by, for example, interpolation processing in the arithmetic unit 29.

  As an interpolation method, for example, weighting in proportion to the gate line number is performed, and proportional interpolation is performed from the gradation value conversion table D1 of the first gate line and the gradation value conversion table DN of the Nth gate line. A gradation value conversion table Dm for the mth gate line is determined (1 <m <N). More specifically, interpolation is performed using an interpolation formula represented by Dm = D1 · (m / N) + DN · (m / N). As a result, the data capacity of the memory for the gradation value conversion table can be reduced.

  Needless to say, the reference data may be prepared not only for two lines of the first gate line and the Nth gate line but also for three or more lines, and interpolation processing may be performed between the respective reference data. Yes. In this case, it is expected that the accuracy of the data created by the interpolation process will increase.

<A-4-4. Modification of brightness unevenness prevention operation>
In the luminance unevenness prevention operation described with reference to FIGS. 6 and 7, a method of changing the applied voltage in accordance with the time from the data writing time to the light source lighting time in each gate line of the liquid crystal display panel 28. However, if the applied voltage is increased, the response speed of the liquid crystal can be increased, but the transmittance may be increased too much. Therefore, the method described below may prevent the transmittance from increasing excessively.

  FIG. 8 is a conceptual diagram showing changes in the response characteristics of the liquid crystal when the voltages applied to the gate lines (gradation voltage) are V2, V3, V4 and V5 (V2 <V3 <V4 <V5). Yes, the horizontal axis represents time, and the vertical axis represents liquid crystal transmittance.

  From FIG. 8, by increasing the voltage to V2, V3, V4, V5, the response speed in the direction of increasing the transmittance of the liquid crystal is increased, and the transmittance is improved in a shorter time. However, at voltages V3, V4, and V5, the transmittance continues to increase past the transmittance L2, which is the average transmittance during the effective lighting period.

  On the other hand, the response characteristic S indicated by the solid line shows the characteristic when the voltage V3 is applied until the transmittance L2 is reached, and maintains the transmittance L2 after reaching the transmittance L2. FIG. 8 also shows an example of a voltage application pattern for obtaining such a response characteristic S.

  As shown in FIG. 8, until the time t0 when the lighting period of the left-eye light source ends in the left-eye image display period, the liquid crystal display panel 28 transmits the transmittance for displaying the left-eye image in the entire liquid crystal display unit 281. L1 and the liquid crystal has a luminance corresponding to the transmittance L1.

  From time t0, an image signal corresponding to the transmittance L2 for displaying the right eye image is sequentially applied from the first gate line by gate scanning. At this time, the first applied voltage to each gate line is V3, which is referred to as a first write voltage, and the application of the first write voltage is referred to as a first write. After the first writing is continued for a predetermined period, the applied voltage is lowered to V2. This is called a second write voltage, and giving the second write voltage is called a second write.

  When this voltage application pattern is compared with the response characteristic S, the transmittance is set to reach L2 from L1 in the period from the start of the first write to the start of the second write (the period of the first write). The first writing period is defined by N · tg.

  In order to obtain such a voltage application pattern, first, the input image data of the latest field is compared with the gradation value of the image data of the field displayed immediately before to obtain the gradation voltage for image display of the latest field. A gradation voltage that emphasizes the gradation change from the previous field to the latest field to be displayed next is generated and applied to the liquid crystal display panel 28 as the first writing voltage, so that the response speed of the liquid crystal with respect to the gradation change is increased. Accelerate and compensate for response delays. As shown in FIG. 9, the first write voltage is common to the first gate line and the Nth gate line, and it is not necessary to prepare a gradation value conversion table for each gate line. This is because, in all the gate lines, the gradation value that provides the first writing voltage that reaches L2 within the first writing period is set in the gradation value conversion table.

  By this. Luminance unevenness in the gate scan direction and ghost intensity unevenness can also be prevented.

  Here, as means for creating a gradation voltage in which gradation change is emphasized, the current liquid crystal display is performed by the arithmetic unit 29 shown in FIG. 1 using a gradation value conversion table as shown in FIG. An optimum gradation voltage is created for changing from the state to the gradation to be displayed next.

  Next, when performing the second writing, the input image data for the right eye in the latest field is not emphasized and used in an uncompensated state.

  Thus, since the first writing voltage is set using the gradation value conversion table and the second writing voltage uses the image data of the latest field in an uncompensated state, the liquid crystal transmittance is unnecessarily high. Can be prevented from continuing. Further, the period during which the first writing voltage is applied is easily affected by variations in the liquid crystal and the environment. However, since the first writing voltage is set using the gradation value conversion table, the occurrence of ghost can be suppressed. it can.

  FIG. 9 shows the relationship between the backlight lighting period for displaying a stereoscopic image and the response characteristics of the liquid crystal when the voltage application pattern as described above is used.

  FIG. 9 shows response characteristics A1 and B1 when a voltage application pattern composed of first and second write voltages is applied to the first gate line and the Nth gate line. The axis represents time, and the vertical axis represents liquid crystal transmittance.

  In FIG. 9, the response characteristic A1 is the response characteristic of the pixel on the first gate line, and the response characteristic B1 is the response characteristic of the pixel on the Nth gate line and is on the first gate line. A time difference of N · tg occurs between the pixel and the pixel on the Nth gate line until the image data is updated, and the first writing period in the response characteristic A1 corresponds to the time difference of N · tg. Is set to In this period, the first write voltage is set so as to reach the transmittance L2.

  As a result, when the second writing is started, the desired transmittance L2 is reached, and then when the first writing voltage is lowered to the second writing voltage, the transmittance L2 is maintained.

  In the pixel on the Nth gate line (response characteristic B1), the first writing period starts at the timing when the second writing period starts in the pixel on the first gate line (response characteristic A1). Thus, the first write voltage in the pixel on the Nth gate line is set to a voltage that reaches the transmittance L2 at time t1 (right eye light source lighting start time).

  By using the voltage application pattern as described above, the time during which the transmittance almost reaches the desired transmittance L2 is maintained over the entire surface of the liquid crystal panel 28, so that data writing is performed on each gate line. Even if the time from the time to the lighting time of the light source is different, the same luminance can be realized on the entire surface of the liquid crystal panel 28.

  In the above description, the description has been made on the assumption that it is applied to a liquid crystal stereoscopic image display device that alternately displays right and left parallax images using a liquid crystal display panel. However, the present invention is synchronized with rewriting of the liquid crystal panel. It is also effective when applied to a flashing moving image-capable LCD or a field sequential color LCD.

  Further, the on-board electronic device is not limited to a mobile phone, but can be applied to a personal computer, a portable game machine, a PDA (Personal Digital Assistant), and the like.

It is a figure which shows the structure of the stereo image display apparatus of embodiment which concerns on this invention. It is a figure which shows the gradation value conversion table used for the stereo image display apparatus of embodiment which concerns on this invention. It is a figure explaining the timing of the moving image data processing of the three-dimensional image display apparatus of embodiment which concerns on this invention. It is a figure explaining the structure of the illuminating device of the liquid crystal display panel of embodiment which concerns on this invention. It is a conceptual diagram which shows the relationship between the lighting period of the backlight for a three-dimensional image display, and the response characteristic of a liquid crystal. It is a schematic diagram explaining the relationship between the response characteristic of a liquid crystal, and a gate line voltage. It is a conceptual diagram which shows the relationship between the lighting period of the backlight of the stereoscopic image display apparatus of embodiment which concerns on this invention, and the response characteristic of a liquid crystal. It is a schematic diagram explaining the relationship between the response characteristic of the liquid crystal of the three-dimensional image display apparatus of embodiment which concerns on this invention, and a gate line voltage. It is a conceptual diagram which shows the relationship between the lighting period of the backlight of the stereoscopic image display apparatus of embodiment which concerns on this invention, and the response characteristic of a liquid crystal.

Explanation of symbols

  13 Encoder, 23 Frame memory, 24 Decoder, 28 Liquid crystal display panel.

Claims (7)

A time-division type stereoscopic image display device that has a plurality of gate lines and a plurality of source lines, displays left and right parallax image data alternately left and right, and performs stereoscopic display,
A liquid crystal display,
An illuminating device having a right eye light source and a left eye light source alternately flashing so as to illuminate the entire surface of the liquid crystal display unit in synchronization with a frame;
A memory for storing the image data for the right eye and the image data for the left eye, and the image data for the right eye and the image data for the left eye that are displayed on the same gate line of the liquid crystal display unit from the memory. For each one gate line, with respect to the read image data for the right eye and the image data for the left eye for each one gate line, either the left or the right is the latest input image data, and the other is one field before The last input image data displayed in
Using the previous input image data for the gradation value compensation processing in the liquid crystal display based on the latest input image data,
The gradation value compensation process is:
In each of the plurality of gate lines, the gradation value is compensated for each of the plurality of gate lines in accordance with the time from the start of the response of the liquid crystal to the time when the light source of the illuminating device is turned on. A three-dimensional image display device that uses data for image display of the latest field to be used. The gradation value compensation process is:
The stereoscopic image display apparatus according to claim 1, wherein the immediately preceding input image data is compared with the latest input image data, and the gradation value is compensated so as to emphasize a gradation change of the latest input image data. An encoder that compresses and encodes the left and right parallax image data, creates compressed image data for the right eye and compressed image data for the left eye, and stores the compressed data in the memory;
The stereoscopic image display device according to claim 1, further comprising: a decoder that reads and decodes the compressed image data for the right eye and the compressed image data for the left eye stored in the memory.   In the gradation value compensation process, the plurality of gate lines are set so that the average transmission rate of the liquid crystal during the lighting period of the light source of the lighting device is equalized in each of the plurality of gate lines. The stereoscopic image display apparatus according to claim 1, wherein the gradation value for each of the two is compensated. In the gradation value compensation processing, compensated gradation data is prepared in advance corresponding to at least two of the plurality of gate lines,
The stereoscopic image display device according to claim 4, wherein the compensated gradation data of the remaining gate lines is determined by interpolation processing based on the compensated gradation data of the at least two gate lines. The gradation value compensation process compensates the gradation value so that the first and second write voltages are applied to each of the plurality of gate lines,
As the first writing voltage, a voltage at which the transmittance of the liquid crystal within a predetermined period reaches an average transmittance of an effective lighting period of the light source of the lighting device is set.
The stereoscopic image display device according to claim 1, wherein a voltage at which the transmittance of the liquid crystal maintains the predetermined value is set as the second writing voltage. The first write voltage is
Comparing the previous input image data and the latest input image data, and is set based on compensated gradation data compensated to emphasize the gradation change of the latest input image data,
The stereoscopic image display device according to claim 6, wherein the second write voltage is set based on the uncompensated latest input image data.

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