JP2015191039A - Image processing apparatus and image processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing apparatus configured to prevent discoloration or the change in luminance of an image generated when a refresh rate is changed, and an image processing method.SOLUTION: An image processing apparatus having PSR function includes: a switch frame calculation section which calculates a frame rate of switch frame which selects first display mode in response to an instruction to select the first display mode; and an image correction section which outputs first correction image data formed by correcting a grayscale value of storage image data of the switch frame so that a luminance on a display panel corresponding to a grayscale value of the storage image data of the switch frame in the frame rate of the switch frame may be equal to a luminance on the display panel corresponding to the grayscale value of receiving image data in a frame rate of the receiving image data. In the case of the switch frame, the correction image data is selected as output image data, to be output from an output data selection section.

Description

  The present invention relates to an image processing apparatus and an image processing method having a PSR (Panel Self-Refresh) function.

  In order to reduce the power consumption of an image display device equipped with a display panel such as a liquid crystal panel, an image display device employing an image interface standard such as a display port (DisplayPort) displays a still image whose screen display does not change. In addition, image data for one screen (one frame) of the still image is stored in a memory unit inside the image processing apparatus provided in the image display device, and the image data of the still image stored in the memory unit is read out. A PSR function for self-refreshing the screen display has been put into practical use.

  FIG. 9 is a block diagram illustrating an example of a configuration of a conventional image processing apparatus. The image processing apparatus 40 shown in the figure has a PSR function, and includes a data receiving unit 12, a memory unit 14, a memory control unit 16, and an output data selection unit 22.

  In the image processing apparatus 40, the data receiving unit 12 receives input image data transferred from a GPU (Graphics Processing Unit) 42 of a personal computer (PC) via a display port, for example, and outputs the received image data. The

  In the first display mode, as shown in FIG. 10A, received image data is selected as output image data and output from the output data selection unit 22, and an image corresponding to the received image data is displayed on the display panel. The

Subsequently, when a still image is displayed on the display panel, data instructing switching from the first display mode to the second display mode is transferred from the GPU 42 to the image processing device 40.
When the data receiving unit 12 receives this data, the received image data is sequentially written into the memory unit 14 by the memory control unit 16 as shown in FIG. As a result, the received image data corresponding to the still image for one screen is stored in the memory unit 14.

  When the received image data corresponding to the still image for one screen is stored in the memory unit 14, the received image data is sequentially read from the memory unit 14 by the memory control unit 16, as shown in FIG. Are output as stored image data. Then, the stored image data is selected as output image data and output from the output data selection unit 22, and a still image corresponding to the stored image data is displayed on the display panel. That is, the first display mode is switched to the second display mode.

  During the period of the second display mode, the GPU 42 on the transmission side of the input image data and the data reception unit 12 of the image processing apparatus 40 on the reception side are put into a dormant state. Thereby, power consumption can be reduced.

Subsequently, when a moving image is displayed on the display panel, data instructing switching from the second display mode to the first display mode is transferred from the GPU 42 to the image processing device 40.
When the data receiving unit 12 receives this data, the received image data is selected as output image data and output from the output data selecting unit 22 as shown in FIG. An image corresponding to is displayed on the display panel. That is, the second display mode is switched to the first display mode.
The subsequent operation is the same.

  In the case of the first display mode used in the display port, the image processing apparatus 40 operates using a clock recovered from the data transferred from the GPU 42, but in the case of the second display mode, the GPU 42 and the data receiving unit 12 are operated. Is in a dormant state and cannot obtain its clock, and therefore operates using an internal clock generated inside the image processing apparatus 40. That is, the received image data and the stored image data are asynchronous during the period of switching from the second display mode to the first display mode.

  Therefore, when switching from the second display mode to the first display mode, the received image data A, B, C, D,... And the stored image data PSR, as shown in FIG. After adjusting the phase, it is necessary to switch from the stored image data PSR to the received image data B in the V (vertical) blanking period. For example, in order to match both phases, reading of the stored image data PSR from the memory unit 14 is stopped, and a V blanking period between the received image data A and the received image data B is waited.

  In this case, as shown in FIG. 11, the V blanking period of the switching frame for switching from the second display mode to the first display mode, that is, the stored image data PSR to the received image data B, is increased according to the switching timing. The refresh rate may change temporarily unintentionally. If the frame rate temporarily changes, it may appear as flicker of an image displayed on a display panel such as a liquid crystal panel. Alternatively, flicker may not occur, but the brightness of the image may change or appear discolored.

Further, in the liquid crystal panel, since the charge of the liquid crystal transistor leaks with time, it is necessary to periodically refresh the screen even when a still image is displayed. On the other hand, in order to reduce the power consumption required for refresh, there is a demand for reducing the refresh rate as much as possible when displaying still images in the second display mode.
However, when the frame rate is lowered, similarly, the brightness of the still image displayed in the second display mode may change or change color.

Here, there is Patent Document 1 as a prior art document relevant to the present invention.
In Patent Document 1, when a still image start signal is applied, input video data is stored in a frame memory, and the stored video data stored in the frame memory is displayed on the display panel at a second frequency lower than the first frequency. And inactivate the transmission of input video data. When a still image end signal is applied, the transmission of the input video data is activated and the input video data is output to the display panel at the first frequency. A display device is described.

JP 2013-37366 A

  An object of the present invention is to provide an image processing apparatus and an image processing method capable of solving the problems of the prior art and reducing changes in image luminance and discoloration caused by a change in refresh rate. .

To achieve the above object, the present invention provides a first display mode for outputting input image data transferred from the outside as output image data, and displaying an image corresponding to the input image data on a display panel, An image processing apparatus having a second display mode in which stored image data stored therein is output as the output image data by a self-refresh function and a still image corresponding to the stored image data is displayed on the display panel. And
A data receiving unit for receiving the input image data transferred from the outside and outputting the received image data;
A memory unit for storing the received image data;
In response to an instruction to switch from the first display mode to the second display mode transferred from the outside, the received image data is written to the memory unit and corresponding to the still image for one screen. A memory control unit that controls to read out the received image data from the memory unit and output it as the stored image data in the second display mode;
Switching frame calculation for calculating a frame rate of a switching frame for switching from the second display mode to the first display mode in response to an instruction for switching from the second display mode to the first display mode transferred from the outside. And
The luminance on the display panel corresponding to the gradation value of the stored image data of the switching frame at the frame rate of the switching frame corresponds to the gradation value of the received image data at the frame rate of the received image data. An image correction unit that outputs first corrected image data in which the gradation value of the stored image data of the switching frame is corrected so as to have the same luminance on the display panel;
In the case of the first display mode, the received image data is selected and output as the output image data, and in the case of a frame other than the switching frame in the second display mode, the stored image data is converted to the output image data. And an output data selection unit that selects and outputs the first corrected image data as the output image data in the case of the switching frame. It is.

Here, the switching frame calculation unit
In response to an instruction for switching from the second display mode to the first display mode transferred from the outside, one frame time of the received image data and the position of the received image data and the stored image data A phase difference calculation unit for calculating a phase difference;
A frame rate calculation unit that calculates a frame rate of the stored image data based on one frame time of the received image data and the phase difference;
After the calculation of the frame rate of the stored image data is completed, the frame of the stored image data for which the frame rate is calculated is switched based on synchronization signals of images corresponding to the received image data and the stored image data, respectively. It is preferable to include a switching frame determination unit that determines a frame.

In addition, the image correction unit
The luminance on the display panel corresponding to the gradation value of the stored image data of the switching frame at the frame rate of the switching frame corresponds to the gradation value of the received image data at the frame rate of the received image data. An LUT unit for storing a correction coefficient or a representative value of the correction value for correcting the gradation value of the stored image data of the switching frame so as to be the same as the luminance on the display panel;
In the case of the switching frame, the representative value of one or more correction coefficients or correction values corresponding to the frame rate of the switching frame is read from the LUT unit, and the one or more correction coefficients or correction values read from the LUT unit And a correction value calculation unit that calculates the first correction image data based on the representative value.

In the second display mode, the memory control unit further reads the received image data from the memory unit at a frame rate in the second display mode input from the outside, and stores the stored image It is controlled to output as data,
The image correction unit further includes the display panel corresponding to a gradation value of stored image data of a frame other than the switching frame in the second display mode at a frame rate in the second display mode input from the outside. Other than the switching frame in the second display mode, the brightness on the display panel is the same as the brightness on the display panel corresponding to the gradation value of the received image data at the frame rate of the received image data. Outputting the second corrected image data obtained by correcting the gradation value of the stored image data of the frame;
Preferably, the output data selection unit is configured to select and output the second corrected image data as the output image data in a frame other than the switching frame in the second display mode.

Further, the present invention outputs input image data transferred from the outside as output image data, and displays the image corresponding to the input image data on the display panel, and the panel self-refresh function, A second display mode for outputting the stored image data stored in the display panel as the output image data and displaying a still image corresponding to the stored image data on the display panel.
A data receiving unit receiving the input image data transferred from the outside and outputting the received image data;
The memory control unit writes the received image data into the memory unit in response to an instruction to switch from the first display mode to the second display mode transferred from the outside, and creates the still image for one screen. Corresponding received image data is stored in the memory unit, and in the case of the second display mode, the received image data is read from the memory unit and controlled to output as the stored image data;
The frame rate of the switching frame in which the switching frame calculation unit switches from the second display mode to the first display mode in response to an instruction for switching from the second display mode to the first display mode transferred from the outside. Calculating steps,
The luminance on the display panel corresponding to the gradation value of the stored image data of the switching frame at the frame rate of the switching frame is determined by the image correction unit so that the gradation of the received image data at the frame rate of the received image data Outputting first corrected image data in which the gradation value of the stored image data of the switching frame is corrected so as to be the same as the luminance on the display panel corresponding to the value;
The output data selection unit selects and outputs the received image data as the output image data in the first display mode, and the stored image in the case of a frame other than the switching frame in the second display mode. Selecting and outputting data as the output image data, and selecting and outputting the first corrected image data as the output image data in the case of the switching frame. provide.

Here, when the memory control unit is in the second display mode, the received image data is further read from the memory unit at a frame rate in the second display mode input from the outside, and stored in the memory unit. Controlling to output as image data;
The display panel further corresponds to a gradation value of stored image data of a frame other than the switching frame of the second display mode at a frame rate in the case of the second display mode input from the outside. Other than the switching frame in the second display mode, the brightness on the display panel is the same as the brightness on the display panel corresponding to the gradation value of the received image data at the frame rate of the received image data. Outputting second corrected image data obtained by correcting the gradation value of the stored image data of the frame;
It is preferable that the output data selection unit includes a step of selecting and outputting the second corrected image data as the output image data in a case other than the switching frame in the second display mode.

According to the present invention, when switching from the second display mode to the first display mode, even when the refresh rate is temporarily changed unintentionally, the luminance change of the image displayed on the display panel, Discoloration can be reduced.
Further, according to the present invention, in the second display mode, even when the refresh rate is changed by lowering the frame rate, the luminance change or discoloration of the image displayed on the display panel is reduced. be able to. In addition, since the frame rate in the second display mode can be freely adjusted, the power consumption of the display panel can be reduced by reducing the frame rate.
In other words, according to the present invention, the response to the problem when switching from the second display mode to the first display mode and when reducing the frame rate in the second display mode is completed only within the image processing apparatus. be able to.

It is a block diagram of one embodiment showing composition of an image processing device of the present invention. It is a block diagram of an example showing the structure of the switching frame calculation part shown in FIG. FIG. 2 is a block diagram illustrating an example of a configuration of an image correction unit illustrated in FIG. 1. 2 is a timing chart illustrating an example of an operation of the image processing apparatus illustrated in FIG. 1. 3 is a flowchart of an example illustrating an operation of a switching frame calculation unit illustrated in FIG. 2. 4 is a flowchart illustrating an example of an operation of an image correction unit illustrated in FIG. 3. It is a conceptual diagram of an example in the case of calculating a correction value corresponding to a frame rate of a switching frame and a gradation value of stored image data from representative values of four correction values. 6 is a timing chart of another example showing the operation of the image processing apparatus shown in FIG. 1. It is a block diagram of an example showing the structure of the conventional image processing apparatus. (A)-(D) are the conceptual diagrams of an example showing operation | movement of the image processing apparatus shown in FIG. FIG. 10 is an example timing chart illustrating an operation of the image processing apparatus illustrated in FIG. 9. FIG.

  Hereinafter, an image processing apparatus and an image processing method according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

  FIG. 1 is a block diagram of an embodiment showing a configuration of an image processing apparatus of the present invention. The image processing apparatus 10 shown in the figure outputs a first display mode (normal display mode) in which input image data transferred from the outside is output as output image data, and an image corresponding to the input image data is displayed on the display panel. And a second display mode (PSR display mode) for outputting stored image data stored therein as output image data and displaying a still image corresponding to the stored image data on the display panel by the PSR function. .

  The image processing apparatus 10 includes a data receiving unit 12, a memory unit 14, a memory control unit 16, a switching frame calculation unit 18, an image correction unit 20, and an output data selection unit 22.

The data receiving unit 12 receives input image data transferred from the outside of the image processing apparatus 10 via, for example, a PC GPU via a video port such as a display port, and outputs the received image data. .
The data receiving unit 12 is not only input image data, but also data for switching from the first display mode to the second display mode and switching from the second display mode to the first display mode, which is transferred from the GPU. Instruction data is also received.

  The memory unit 14 is a semiconductor memory such as an SDRAM (Synchronous Dynamic Random Access Memory), and a received image of a still image for one screen displayed on the display panel in the second display mode under the control of the memory control unit 16. Stores data.

The memory control unit 16 controls writing of received image data to the memory unit 14 and reading of received image data from the memory unit 14.
The memory control unit 16 writes the received image data to the memory unit 14 in response to an instruction to switch from the first display mode to the second display mode transferred from the GPU, and receives corresponding to a still image for one screen. The image data is stored in the memory unit 14, and in the second display mode, the received image data is read from the memory unit 14 and output as stored image data.

Subsequently, the switching frame calculation unit 18 responds to the switching instruction from the second display mode to the first display mode transferred from the GPU, and the frame rate of the switching frame that switches from the second display mode to the first display mode. Is calculated.
As shown in FIG. 2, the switching frame calculation unit 18 includes a phase difference calculation unit 24, a frame rate calculation unit 26, and a switching frame determination unit 28.

The phase difference calculation unit 24 receives one frame time of the received image data and the received image data and the stored image data in response to the instruction for switching from the second display mode to the first display mode transferred from the GPU. The phase difference is calculated.
The phase difference calculation unit 24 also outputs a synchronization signal including an image display period signal and a V blanking period signal corresponding to the received image data and the stored image data.

The frame rate calculation unit 26 determines the frame of the stored image data (the stored image data of the frame predicted to be the switching frame) based on one frame time of the received image data and the phase difference between the received image data and the stored image data. The rate is calculated.
The frame rate calculation unit 26 also outputs a frame rate calculation completion signal that becomes active when the calculation of the frame rate of the stored image data is completed.

The switching frame determination unit 28, after completing the calculation of the frame rate of the stored image data based on the frame rate calculation completion signal, determines the frame rate based on the received image data and the synchronization signal of the image corresponding to the stored image data. The frame of the stored image data for which is calculated is determined as a switching frame.
The switching frame determination unit 28 outputs a switching frame signal that becomes active during the switching frame period.

Subsequently, the image correction unit 20 determines that the luminance on the display panel corresponding to the gradation value of the stored image data of the switching frame at the frame rate of the switching frame is the gradation value of the received image data at the frame rate of the received image data. The first corrected image data in which the gradation value of the stored image data of the switching frame is corrected so as to be the same as the luminance on the display panel corresponding to is output.
As shown in FIG. 3, the image correction unit 20 includes an LUT unit 30 and a correction value calculation unit 32.

  The LUT unit 30 displays the luminance on the display panel corresponding to the gradation value of the stored image data of the switching frame at the frame rate of the switching frame corresponding to the gradation value of the received image data at the frame rate of the received image data. The correction coefficient for correcting the gradation value of the stored image data of the switching frame or the representative value of the correction value is stored so as to be the same as the luminance on the panel.

  Based on the switching frame signal, the correction value calculation unit 32 reads one or more correction coefficients or representative values of correction values corresponding to the frame rate of the switching frame from the LUT unit 30 in the case of the switching frame, and from the LUT unit 30. First corrected image data is calculated based on one or more read correction coefficients or representative values of correction values.

  When the correction coefficient that matches the gradation value of the stored image data of the switching frame or the representative value of the correction value is stored in the LUT unit 30, the correction value calculation unit 32 uses one correction coefficient that matches the gradation value. Alternatively, the representative value of the correction value is read out.

  On the other hand, when the correction coefficient or the representative value of the correction value that matches the gradation value of the stored image data of the switching frame is not stored in the LUT unit 30, an interpolation process is necessary. In this case, the correction value calculation unit 32 reads the correction coefficient corresponding to the gradation value or two or more correction coefficients before and after the correction value, or representative values of the correction values, and reads the two or more read correction coefficients or correction values. A correction coefficient or correction value that matches the gradation value of the stored image data of the switching frame is calculated by interpolating between the representative values.

When the correction coefficient is stored in the LUT unit 30, the correction value calculation unit 32 calculates a result of multiplying the correction coefficient calculated by interpolation and the gradation value of the stored image data of the switching frame, Output as first corrected image data.
On the other hand, when the correction value is stored in the LUT unit 30, the correction value calculation unit 32 outputs the correction value calculated by interpolation as the first corrected image data.

  Finally, the output data selection unit 22 selects and outputs the received image data as output image data in the first display mode, and stores the stored image data in a frame other than the switching frame in the second display mode. The output image data is selected and output, and in the case of the second display mode switching frame, the first corrected image data is selected and output as the output image data.

  Next, before describing the operation of the image processing apparatus 10, the operation of the switching frame calculation unit 18 will be described with reference to the flowchart shown in FIG.

  The switching frame calculation unit 18 waits until the data receiving unit 12 receives data for instructing to start switching from the second display mode to the first display mode (NO in step S1). When the data receiving unit 12 receives the data for instructing switching start (YES in step S1), the phase difference calculating unit 24 performs one frame time of the received image data and the received image data in accordance with the instruction to start switching. And the phase difference between the stored image data.

  In this case, the phase difference calculation unit 24 waits until it detects the start of the frame of the received image data based on the synchronization signal of the image corresponding to the received image data (NO in step S2). When the start of the frame of the received image data is detected (YES in step S2), as shown in FIG. 4, the phase difference calculation unit 24 clears the count value of the counter to 0 and then synchronizes with the internal clock by the counter. Thus, counting is started from the start of the frame of the received image data A (step S3).

  Subsequently, the phase difference calculation unit 24 continues counting by the counter until it detects the start of the frame of the next received image data B (NO in step S4). When the start of the frame of the received image data B is detected (YES in step S4), as shown in FIG. 4, the phase difference calculating unit 24 ends the count of the counter (step S5), and the count value is set to the received image. After the data is stored in the first register as the cycle number a for one frame time (step S6), the counter value is cleared to zero.

  Note that the cycle number a can be calculated in advance at the start of the second display mode, for example.

  Subsequently, the phase difference calculation unit 24 continues counting by the counter until it detects the start of the frame of the next stored image data PSR based on the synchronization signal of the image corresponding to the stored image data PSR (NO in step S7). ). When the start of the frame of the next stored image data PSR is detected (YES in step S7), as shown in FIG. 4, the phase difference calculation unit 24 ends the count of the counter, and the count value is set as the received image data. Stored in the second register as the number of cycles b of the phase difference from the stored image data (step S8).

Subsequently, the frame rate calculation unit 26 calculates the frame rate of the stored image data based on the cycle numbers a and b (step S9).
Here, as shown in FIG. 4, X = a and Y = a + a−b, where X is the number of cycles of one frame time of received image data and Y is the number of cycles of one frame time of stored image data. Therefore, if the frame rate of the received image data is 60 Hz, the frame rate F of the stored image data can be calculated by F = 60 × (X / Y).

  Subsequently, after the calculation of the frame rate of the switching frame is completed by the switching frame determination unit 28 based on the frame rate calculation completion signal from the frame rate calculation unit 26, the received image data A, Switching frames are determined on the basis of image synchronization signals respectively corresponding to B, C, D,... And stored image data PSR. In the example of FIG. 4, the switching frame is a period from the start of the frame of the stored image data PSR next to the received image data B to the start of the frame of the received image data D.

  As described above, the switching frame calculation unit 18 outputs the frame rate of the switching frame and the switching frame signal that becomes active during the period of the switching frame (step S10).

Subsequently, the switching frame calculation unit 18 waits until the data reception unit 12 receives data indicating the end of switching from the second display mode to the first display mode (NO in step S11). When the data receiving unit 12 receives the data indicating the end of switching (YES in Step S11), the switching frame signal becomes inactive according to this instruction (Step S12).
Thereafter, the process returns to step S1 and the above-described operation is repeated.

  Next, the operation of the image correction unit 20 will be described with reference to the flowchart shown in FIG.

  In the image correction unit 20, for example, when the image display apparatus on which the image processing apparatus 10 is mounted is turned on, a correction coefficient or correction value stored in a flash ROM (Read Only Memory) or the like provided outside the image processing apparatus 10. Are read out and written to the LUT unit 30 (step S13).

  The image correction unit 20 waits until the correction coefficient or the representative value of the correction value is completely written to the LUT unit 30 (NO in step S14). When the writing of the correction coefficient or the representative value of the correction value to the LUT unit 30 is completed (YES in step S14), the image correction unit 20 is ready for correction processing (step S15).

  Subsequently, the image correction unit 20 waits until the stored image data is input (NO in step S16). When the stored image data is input (YES in step S16), the gradation value of the stored image data is not corrected until the switching frame signal becomes active (NO in step S17), that is, until the switching frame is reached. Then, it is output as it is from the correction value calculation unit 32 (step S18). Then, it returns to step S16.

Subsequently, when the switching frame signal becomes active (YES in step S17), the correction value calculation unit 32 reads a correction coefficient or a representative value of the correction value corresponding to the frame rate of the switching frame from the LUT unit 30 ( In step S19), the gradation value of the stored image data of the switching frame is corrected based on the correction coefficient or the representative value of the correction value read from the LUT unit 30 (step S20), and the first corrected image data is output. (Step S21).
Thereafter, the process returns to step S16 and the above-described operation is repeated.

  Here, the correction process of the correction value calculation unit 32 will be described.

For example, when the representative value of the correction coefficient is stored in the LUT unit 30, the gradation values of the RGB components of the stored image data of the switching frame are common to the RGB components corresponding to the frame rate of Rx, Gx, Bx, and the switching frame. Assuming that the correction coefficient is γ, the gradation values R_out, G_out, and B_out of the RGB components of the first corrected image data can be calculated by Expression (1).
R_out = Rx × γ
G_out = Gx × γ
B_out = Bx × γ (1)

  On the other hand, when the representative value of the correction value is stored in the LUT unit 30, the gradation values R_out, G_out, and B_out of the RGB components of the first corrected image data are the RGB components corresponding to the frame rate of the switching frame. This is the correction value.

  Note that three LUT units 30 each storing a correction coefficient or a representative value of a correction value corresponding to each RGB component may be provided. In that case, the representative value of the correction coefficient or the correction value is set for each of the RGB components. It can be a different value.

  Hereinafter, a specific example will be described.

For example, as shown in Table 1, when the representative value of the correction coefficient is stored in the LUT unit 30, the frame rate of the switching frame is 42 Hz, and the gradation value represented by 8 bits is 134. To do.
In this case, 0.95 and 0.9, which are representative values of correction coefficients respectively corresponding to the frame rates of 45 Hz and 40 Hz before and after 42 Hz, which is the frame rate of the switching frame, are read from the LUT unit 30.

The correction value calculation unit 32 interpolates between 0.95 and 0.9, which are representative values of the two correction coefficients, using Equation (2), and calculates a correction coefficient corresponding to 42 Hz, which is the frame rate of the switching frame. calculate.
(0.95 × (42−40) + 0.9 × (45−42)) / (45−40) = 0.92 Formula (2)
Further, the gradation value of the first corrected image data is multiplied by 134, which is the gradation value of the stored image data of the switching frame, and the correction coefficient 0.92 calculated by interpolation according to Expression (3). Can be calculated.
134 × 0.92 = 123.28 Formula (3)
For example, the gradation value of the first corrected image data is 123 by rounding off the decimal part.

Further, as shown in Table 2, when the representative value of the correction value is stored in the LUT unit 30, the frame rate of the switching frame is 51 Hz, and the gradation value represented by 8 bits is 218. To do.
In this case, representative values of the correction values respectively corresponding to the frame rates of 55 Hz and 50 Hz before and after 51 Hz as the frame rate of the switching frame, and corresponding to 224 and 208 before and after 218 as the gradation value, respectively. Certain 223, 207, 220 and 205 are read from the LUT unit 30.

First, as shown in FIG. 7, the correction value calculation unit 32 calculates a value between 207 and 205 that are representative values of the two correction values, and 223 that is a representative value of the two correction values. Interpolated values A and B interpolated between 220 are calculated.
A: (207 × (51−50) + 205 × (55−51)) / (55−50) = 205.4
B: (223 * (51-50) + 220 * (55-51)) / (55-50) = 220.6 ... Formula (4)
Subsequently, interpolation is performed between 205.4 and 220.6 which are interpolation values A and B by Expression (5), and as shown in FIG. 7, the frame rate of the switching frame is 51 Hz, and its gradation value. A correction value corresponding to 218 is calculated.
(205.4 * (224-218) + 220.6 * (218-208)) / (224-208) = 2149 .... Formula (5)
For example, the gradation value of the first corrected image data is 215 by rounding off the decimal part.

  Note that the step size of the gradation values in Table 2 may not be constant.

  Next, the operation of the image processing apparatus 10 will be described.

  The first display mode, the switching from the first display mode to the second display mode, and the operation of the image processing apparatus 10 in the second display mode are the same as those of the conventional image processing apparatus 40 shown in FIG. is there.

When the data receiving unit 12 receives data instructing switching from the second display mode to the first display mode, the switching frame calculating unit 18 calculates the frame rate of the switching frame in response to the instruction.
Then, the brightness on the display panel corresponding to the gradation value of the stored image data of the switching frame at the frame rate of the switching frame is changed by the image correction unit 20 to the gradation value of the received image data at the frame rate of the received image data. The gradation value of the stored image data of the switching frame is corrected so as to be the same as the luminance on the corresponding display panel, and the first corrected image data is output.

In the switching frame, the first corrected image data is selected as output image data and output from the output data selection unit 22, and a still image corresponding to the first corrected image data is displayed on the display panel.
Thus, in the image processing apparatus 10, when the second display mode is switched to the first display mode, the brightness of the image displayed on the display panel is maintained even when the refresh rate temporarily changes unintentionally. Change and discoloration can be reduced.

Subsequently, the received image data is selected as output image data and output from the output data selection unit 22, and an image corresponding to the received image data is displayed on the display panel. That is, the second display mode is switched to the first display mode.
The subsequent operation is the same.

Further, the present invention can be applied not only to the switching frame but also to the case where the frame rate is lower than the frame rate of the received image data in the second display mode.
Here, the frame rate of the stored image data is determined not by the image processing apparatus 10 autonomously but by the frame rate in the second display mode input from the outside. Even if not in the frame mode, the frame rate can be determined by the number of cycles in one frame time, the number of cycles in the image display period, the number of cycles in the V blanking period, or the like.

For example, as shown in FIG. 8, when the frame rate in the second display mode is determined as the number of cycles Z for one frame time, if the frame rate of the received image data is 60 Hz, the frame of the stored image data The rate F can be calculated by equation (6).
F = 60 × (X / Y) Expression (6)

In this case, when the data receiving unit 12 receives the instruction data for switching from the first display mode to the second display mode, the memory control unit 16 responds to the instruction in the case of the second display mode. The received image data is read from the memory unit 14 at the frame rate in the second display mode input from the GPU, and is controlled to be output as stored image data.
Further, the image correction unit 20 further causes the image correction unit 20 on the display panel corresponding to the gradation value of the stored image data of the frames other than the switching frame of the second display mode at the frame rate in the case of the second display mode. Of the stored image data of the frames other than the switching frame of the second display mode so that the brightness of the image is the same as the brightness on the display panel corresponding to the gradation value of the received image data at the frame rate of the received image data. Second corrected image data in which the tone value is corrected is output.
Then, in the case of a frame in the second display mode other than the switching frame, the second corrected image data is selected as output image data and output from the output data selection unit 22, and an image corresponding to the second correction data is displayed on the display panel. Is displayed.
The subsequent operation is the same.

Accordingly, in the image processing apparatus 10, in the second display mode, even when the refresh rate is changed by lowering the frame rate, the luminance change or discoloration of the image displayed on the display panel is reduced. can do. In addition, since the frame rate in the second display mode can be freely adjusted, the power consumption of the display panel can be reduced by reducing the frame rate.
That is, in the image processing apparatus 10, the response to the problem when switching from the second display mode to the first display mode and when reducing the frame rate in the second display mode is completed only within the image processing apparatus 10. Can be made.

  Note that the specific configuration of each component constituting the image processing apparatus 10 is not limited in any way, and various configurations having similar functions can be used.

The present invention is basically as described above.
Although the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and it is needless to say that various improvements and modifications may be made without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 10, 40 Image processing apparatus 12 Data receiving part 14 Memory part 16 Memory control part 18 Switching frame calculation part 20 Image correction part 22 Output data selection part 24 Phase difference calculation part 26 Frame rate calculation part 28 Switching frame determination part 30 LUT part 32 Correction value calculation unit 42 GPU

Claims (6)

A first display mode in which input image data transferred from the outside is output as output image data and an image corresponding to the input image data is displayed on a display panel, and a stored image stored internally by a panel self-refresh function A second display mode for outputting data as the output image data and displaying a still image corresponding to the stored image data on the display panel;
A data receiving unit for receiving the input image data transferred from the outside and outputting the received image data;
A memory unit for storing the received image data;
In response to an instruction to switch from the first display mode to the second display mode transferred from the outside, the received image data is written to the memory unit and corresponding to the still image for one screen. A memory control unit that controls to read out the received image data from the memory unit and output it as the stored image data in the second display mode;
Switching frame calculation for calculating a frame rate of a switching frame for switching from the second display mode to the first display mode in response to an instruction for switching from the second display mode to the first display mode transferred from the outside. And
The luminance on the display panel corresponding to the gradation value of the stored image data of the switching frame at the frame rate of the switching frame corresponds to the gradation value of the received image data at the frame rate of the received image data. An image correction unit that outputs first corrected image data in which the gradation value of the stored image data of the switching frame is corrected so as to have the same luminance on the display panel;
In the case of the first display mode, the received image data is selected and output as the output image data, and in the case of a frame other than the switching frame in the second display mode, the stored image data is converted to the output image data. And an output data selection unit that selects and outputs the first corrected image data as the output image data in the case of the switching frame. The switching frame calculation unit
In response to an instruction for switching from the second display mode to the first display mode transferred from the outside, one frame time of the received image data and the position of the received image data and the stored image data A phase difference calculation unit for calculating a phase difference;
A frame rate calculation unit that calculates a frame rate of the stored image data based on one frame time of the received image data and the phase difference;
After the calculation of the frame rate of the stored image data is completed, the frame of the stored image data for which the frame rate is calculated is switched based on synchronization signals of images corresponding to the received image data and the stored image data, respectively. The image processing apparatus according to claim 1, further comprising a switching frame determination unit that determines a frame. The image correction unit
The luminance on the display panel corresponding to the gradation value of the stored image data of the switching frame at the frame rate of the switching frame corresponds to the gradation value of the received image data at the frame rate of the received image data. An LUT unit for storing a correction coefficient or a representative value of the correction value for correcting the gradation value of the stored image data of the switching frame so as to be the same as the luminance on the display panel;
In the case of the switching frame, the representative value of one or more correction coefficients or correction values corresponding to the frame rate of the switching frame is read from the LUT unit, and the one or more correction coefficients or correction values read from the LUT unit The image processing apparatus according to claim 1, further comprising: a correction value calculation unit that calculates the first correction image data based on the representative value of the first correction image data. In the second display mode, the memory control unit further reads out the received image data from the memory unit at a frame rate in the second display mode input from the outside, and stores the received image data as the stored image data. Control to output,
The image correction unit further includes the display panel corresponding to a gradation value of stored image data of a frame other than the switching frame in the second display mode at a frame rate in the second display mode input from the outside. Other than the switching frame in the second display mode, the brightness on the display panel is the same as the brightness on the display panel corresponding to the gradation value of the received image data at the frame rate of the received image data. Outputting the second corrected image data obtained by correcting the gradation value of the stored image data of the frame;
The output data selection unit is configured to select and output the second corrected image data as the output image data in a case other than the switching frame in the second display mode. The image processing apparatus according to claim 1. A first display mode in which input image data transferred from the outside is output as output image data and an image corresponding to the input image data is displayed on a display panel, and a stored image stored internally by a panel self-refresh function A second display mode for outputting data as the output image data and displaying a still image corresponding to the stored image data on the display panel;
A data receiving unit receiving the input image data transferred from the outside and outputting the received image data;
The memory control unit writes the received image data into the memory unit in response to an instruction to switch from the first display mode to the second display mode transferred from the outside, and creates the still image for one screen. Corresponding received image data is stored in the memory unit, and in the case of the second display mode, the received image data is read from the memory unit and controlled to output as the stored image data;
The frame rate of the switching frame in which the switching frame calculation unit switches from the second display mode to the first display mode in response to an instruction for switching from the second display mode to the first display mode transferred from the outside. Calculating steps,
The luminance on the display panel corresponding to the gradation value of the stored image data of the switching frame at the frame rate of the switching frame is determined by the image correction unit so that the gradation of the received image data at the frame rate of the received image data Outputting first corrected image data in which the gradation value of the stored image data of the switching frame is corrected so as to be the same as the luminance on the display panel corresponding to the value;
The output data selection unit selects and outputs the received image data as the output image data in the first display mode, and the stored image in the case of a frame other than the switching frame in the second display mode. An image processing method comprising: selecting and outputting data as the output image data; and selecting and outputting the first corrected image data as the output image data in the case of the switching frame. When the memory control unit is in the second display mode, the received image data is further read from the memory unit at a frame rate in the second display mode input from the outside, and is stored as the stored image data. Controlling to output, and
The display panel further corresponds to a gradation value of stored image data of a frame other than the switching frame of the second display mode at a frame rate in the case of the second display mode input from the outside. Other than the switching frame in the second display mode, the brightness on the display panel is the same as the brightness on the display panel corresponding to the gradation value of the received image data at the frame rate of the received image data. Outputting second corrected image data obtained by correcting the gradation value of the stored image data of the frame;
The output data selection unit includes a step of selecting and outputting the second corrected image data as the output image data in a case other than the switching frame in the second display mode. Image processing method.