JP2014134704A - Image processing system, image processing method, and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce simultaneous switching noise during processing image data with a simple configuration.SOLUTION: A projector 1 includes: a color space conversion part 13 of a front end IC 8 for converting input image data of a predetermined number of bits; a scaler 14 of a scaler IC 9 for processing converted image data by the color space conversion part 13; and a color space conversion part 17 of an LCD controller IC 10 for performing inverse transformation and outputting processed image data by the scaler 14.

Description

  The present invention relates to an image processing device, an image processing method, and a display device.

It is known that simultaneous switching noise occurs in a data processing system having a multi-bit data bus. Simultaneous switching noise is generated when signals simultaneously change on a plurality of signal lines, and causes deterioration of EMI (ElectroMagnetic Interference). In recent years, with the advancement of data processing, it has become difficult to take measures against simultaneous switching noise as the speed of signals on a circuit board and the number of data buses increase.
Therefore, conventionally, a method has been proposed in which the simultaneous switching noise is reduced by delaying the signal in each signal line of the data bus and adjusting the skew (see, for example, Patent Document 1).

JP 2012-044488 A

The configuration described in Patent Document 1 includes a buffer circuit and a delay circuit corresponding to each signal line of the data bus, and determines a delay amount in the delay circuit based on a change in the signal of each signal line. In this configuration, since the circuit configuration becomes complicated, a method capable of reducing simultaneous switching noise with a simpler configuration has been desired. In particular, in an apparatus that processes image data, it is necessary to process a large amount of image data at high speed. For this reason, when complicated processing is performed to reduce simultaneous switching noise, there is a problem that problems such as processing delay are likely to occur.
The present invention has been made in view of the above-described circumstances, and an object thereof is to reduce simultaneous switching noise when processing image data with a simple configuration.

In order to solve the above problems, an image processing apparatus according to the present invention includes a conversion unit that converts input image data having a predetermined number of bits, an image processing unit that processes the converted image data converted by the conversion unit, and Output means for inversely converting and outputting the processed image data processed by the image processing means.
According to the present invention, it is possible to suppress the occurrence of simultaneous switching noise when image processing is performed by converting image data. In addition, since the inverse transformation is performed before outputting the image data, the influence on the output image can be suppressed.

In the image processing apparatus, the image processing means may be constituted by a hardware circuit including a bus for inputting and outputting the predetermined number of bits of image data.
In this case, the occurrence of simultaneous switching noise in the bus of the hardware circuit that processes the input image data can be effectively suppressed.

In the image processing apparatus, the conversion unit may perform conversion to reduce the number of bits whose value changes when the input image data changes from a minimum value to a maximum value or vice versa. .
In this case, by converting the image data, it is possible to reduce a phenomenon in which many bit values change simultaneously, and it is possible to more reliably suppress the occurrence of simultaneous switching noise.

The image processing apparatus may include a control unit that determines whether or not conversion by the conversion unit is necessary based on a white ratio in a frame constituting the input image data.
In this case, it is possible to quickly determine whether or not the input image data is a type of data that can effectively suppress simultaneous switching noise by performing data conversion. Thereby, for example, it is possible to suppress simultaneous switching noise by converting data that can be expected to have an effect, and to reduce the processing load by omitting the conversion of data that is difficult to expect. Therefore, simultaneous switching noise can be suppressed more efficiently.

In the image processing apparatus, the conversion unit may perform a conversion to change a part of values on the lower bit side of the input image data having the predetermined number of bits.
In this case, by changing some values on the lower bit side, it is possible to reliably suppress the occurrence of simultaneous switching noise without greatly changing the value of data consisting of a plurality of bits.

In the image processing apparatus, the image processing means is connected to a memory by a bus having a bus width of the predetermined number of bits, and executes processing for developing the converted image data in the memory, and the output means May be configured to perform processing in a direction opposite to the conversion executed by the conversion means on the image data developed and processed in the memory by the image processing means.
In this case, it is possible to suppress the occurrence of simultaneous switching noise during memory access by converting the image data before performing image processing by accessing the memory through a bus having a predetermined number of bits. Thereby, generation | occurrence | production of simultaneous switching noise can be suppressed effectively. Furthermore, since the reverse conversion is performed on the image data after the image processing, the influence on the image quality can be minimized.

In the image processing apparatus, the conversion unit performs a process of converting the maximum value of the input image data into a smaller value, and the output unit converts the maximum value of the processed image data by the conversion unit. It may be converted to a maximum value before being processed.
In this case, the occurrence of simultaneous switching noise can be suppressed by a simple process by reducing the maximum value of the image data. In addition, since the maximum value of the converted data is output after being processed to be the maximum value before conversion, image deterioration can be prevented.

In order to solve the above problems, the present invention provides an image processing method for converting image data, and executes conversion processing for changing the values of at least some of the bits of input image data having a predetermined number of bits. The image data after conversion is processed, and the converted image data is converted in the reverse direction of the conversion process and output.
According to the present invention, it is possible to suppress the occurrence of simultaneous switching noise when image processing is performed by converting image data. In addition, since the inverse transformation is performed before outputting the image data, the influence on the output image can be suppressed.

In order to solve the above problems, the present invention provides a conversion unit that converts input image data having a predetermined number of bits, an image processing unit that processes the converted image data converted by the conversion unit, and the image processing Output means for inversely converting and outputting the processed image data processed by the means, and display means for displaying the image data output by the output means.
According to the present invention, it is possible to suppress the occurrence of simultaneous switching noise when image processing is performed by converting image data. Further, by performing inverse conversion before the process of displaying the image data, it is possible to suppress the occurrence of simultaneous switching noise without causing deterioration of the display image.

  According to the present invention, it is possible to suppress the occurrence of simultaneous switching noise during image processing.

FIG. 2 is a functional block diagram of a projector according to an embodiment of the invention. It is explanatory drawing which shows the conversion process of image data. It is a flowchart which shows operation | movement of a projector.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a functional block diagram showing a configuration of 1 to which the present invention is applied.
The projector 1 (display device) projects a still image or a moving image on the screen SC. The projector 1 includes an interface (I / F) 2, a projection unit 3 (display means), and an image processing unit 7 (image processing device). The projector 1 includes an operation panel operated by a user, a remote control device, a remote control receiving unit that communicates with the remote control device, a power supply device, and the like, but illustration and description thereof are omitted here.

  The interface 2 includes a connector connected to an external image supply device, an interface circuit, and the like. For example, the interface 2 may include various interfaces such as DVI, USB, LAN, HDMI (registered trademark), and DisplayPort (trademark) as interfaces for digital data. The interface 2 may include an S video terminal, an RCA terminal, a D terminal, a D-Sub terminal, and the like as an interface for analog image signals. Examples of devices connected to the interface 2 include video output devices such as personal computers, video playback devices, DVD playback devices, TV tuner devices, CATV set-top boxes, and video game devices. The digital image data S1 and the analog image signal S2 are input to the interface 2 of the present embodiment. The interface 2 outputs the input digital image data S1 and analog image signal S2 to the image processing unit 7.

  The projection unit 3 includes a light source unit 4, a light modulation device 5, and a projection optical system 6. The light source unit 4 includes a xenon lamp, an ultrahigh pressure mercury lamp, or the like as a light source. The light source unit 4 may include a reflector and an auxiliary reflector that guide light emitted from the light source to the light modulation device 5. Further, the light source unit 4 includes a lens group (not shown) for enhancing the optical characteristics of the projection light, a polarizing plate, a dimming element that reduces the amount of light emitted from the light source on the path to the light modulation device 5, and the like. You may have.

The light modulation device 5 modulates the light emitted from the light source unit 4 based on the image data input from the image processing unit 7. The light modulation device 5 of this embodiment includes three transmissive liquid crystal panels corresponding to RGB colors. The light modulation device 5 forms an image with each pixel arranged on the transmissive liquid crystal panel, and modulates the light emitted from the light source unit 4. The liquid crystal panel of the light modulation device 5 is driven by a liquid crystal driver IC (Integrated Circuit) (not shown) to form an image. The light modulation device 5 may employ a method using a reflective liquid crystal light valve or a method using three digital mirror devices (DMD). Further, as the light modulation device 5, a method in which a color wheel and one DMD or liquid crystal panel are combined may be employed.
The projection optical system 6 includes a lens group that performs enlargement / reduction of the projected image and adjustment of the focus, a zoom adjustment motor, a focus adjustment motor, and the like. The projection optical system 6 projects the light (image light) modulated by the light modulation device 5 onto the screen SC and forms an image on the screen SC.

The image processing unit 7 processes the digital image data S <b> 1 or the analog image signal S <b> 2 input from the interface 2 and outputs it to the projection unit 3. The image processing unit 7 includes a front end IC 8, a scaler IC 9, an LCD controller IC 10, and a DDR memory 11. The DDR memory 11 is a memory device compliant with the DDR SDRAM (Double-Data-Rate Synchronous Dynamic Random Access Memory) standard. A frame memory 15 is provided in the storage area of the DDR memory 11.
The front end IC 8 includes a front end circuit 12 and a color space converter (CSC: Color Space Converter) 13. The front-end circuit 12 is disposed at the input stage of the front-end IC 8 and receives digital image data S1 and an analog image signal S2 from the interface 2. The front end circuit 12 decodes the digital image data S <b> 1 input from the interface 2 and outputs it to the color space conversion unit 13. The front end circuit 12 performs A / D conversion processing on the analog image signal S2 input from the interface 2 and outputs the converted digital image data to the color space conversion unit 13.
The color space conversion unit 13 is configured by hardware capable of performing a 3 × 3 matrix operation, for example, and is arranged at the output stage of the front end IC 8. The color space conversion unit 13 performs color space conversion (luminance color difference space-RGB space) on the digital image data input from the front end circuit 12 and outputs the processed data to the scaler IC 9.

  The scaler IC 9 includes a scaler 14 that processes data input from the front end IC 8 under the control of the CPU 21. The scaler 14 develops the input data in the frame memory 15 and draws an image for one frame. The scaler 14 and the frame memory 15 are connected by a bus B having a predetermined bit width. The bit width of the bus B is a bit width that matches the number of bits of image data processed by the scaler 14.

The scaler 14 performs various image processes on the image developed in the frame memory 15. As this image processing, for example, processing such as resolution conversion of data input from the front-end IC 8 is executed.
In addition, the scaler 14 may execute a distortion correction process for correcting trapezoidal distortion or pincushion distortion when the projection unit 3 projects an image on the screen SC with respect to the image developed in the frame memory 15. In this distortion correction processing, the scaler 14 deforms the image in the frame memory 15 so as to compensate for distortion generated on the screen SC.
The scaler 14 may perform a process for adjusting the color tone of the image developed in the frame memory 15. The projector 1 has a color mode function for adjusting the color tone of the projected image on the screen SC. In the color mode function, for example, the user selects a desired color mode from preset color modes such as a theater mode, a living mode, and a blackboard mode. The scaler 14 performs a process of changing the color of the image drawn in the frame memory 15 using an adjustment parameter corresponding to the designated color mode.

The scaler 14 outputs the image data on the frame memory 15 to the LCD controller IC 10 after executing the various image processes described above.
The LCD controller IC 10 includes an LCD controller 16 and a color space conversion unit (CSC) 17.
The LCD controller 16 is arranged at the input stage of the LCD controller IC 10. The LCD controller 16 performs various image adjustment processes including gamma adjustment on the image data input from the scaler IC 9. By this image adjustment processing, the LCD controller 16 generates image data for drawing on the liquid crystal panel included in the light modulation device 5 and outputs the image data to the color space conversion unit 17. The LCD controller 16 also has an average picture level (APL) calculation function and a histogram measurement function for one frame image based on the image data input from the scaler 14.
The color space conversion unit 17 is configured by hardware capable of performing a 3 × 3 matrix operation, for example, and is arranged at the output stage of the LCD controller IC 10. The color space conversion unit 17 performs color space conversion processing on the image data processed by the LCD controller 16, and outputs the processed image data to the light modulation device 5.

The scaler IC 9 includes a CPU 21, a RAM 22, and a ROM 23. The CPU 21 reads out and executes a program stored in the ROM 23, and controls each unit of the image processing unit 7 based on data such as setting values stored in the ROM 23. The RAM 22 temporarily stores programs executed by the CPU 21, data to be processed, and the like.
The CPU 21 controls the scaler 14 by executing a program in the ROM 23. Under the control of the CPU 21, the scaler 14 develops an image in the frame memory 15 and executes the above-described various image processing (resolution conversion processing, distortion correction processing, color tone adjustment processing) and the like. The CPU 21 outputs data for specifying a process to be executed to the scaler 14, parameters relating to the specified process, and the like. This parameter is stored in the ROM 23, for example.

The projector 1 has a function of converting image data by the color space conversion units 13 and 17 in order to suppress the occurrence of simultaneous switching noise related to the processing of the scaler 14.
FIGS. 2A and 2B are explanatory diagrams showing image data conversion processing in the color space conversion units 13 and 17. FIG. 2A shows an example of conversion processing by the color space conversion unit 13, and FIG. An example of the inverse conversion process by is shown.
The color space conversion unit 13 converts the image data input from the front end circuit 12 under the control of the CPU 21, and outputs the converted image data to the scaler 14. For example, the image data of the input image is input from the front end circuit 12 to the color space conversion unit 13 for each pixel. For example, when processing 24-bit color image data, the data of one pixel is composed of R 8-bit data, G 8-bit data, and B 8-bit data.

2A shows an example in which 8-bit data P1, P2, P3, P4... Are input to the color space conversion unit 13. FIG. 2A and 2B show the input and output data in time series. Each data in FIG. 2A is input to the color space conversion unit 13 in the order of data P1, P2, P3, P4.
The maximum value of the data P1, P2, P3, P4... Is 0xFF, and the minimum value is 0x00. The value of the data P1 in this example is 0x00 (minimum value), and the value of each bit is “00000000”. The value of the data P2 is 0xFF (maximum value), and the value of each bit is “11111111”. Data P1 and P2 are typical examples in which simultaneous switching noise occurs. That is, simultaneous switching noise is more likely to occur as the number of bits whose values change simultaneously increases when data is transmitted to a bus having a bit width of a plurality of bits. When data P1 and P2 are transmitted by an 8-bit bus, the values of all bits change when transitioning from data P1 to data P2. At this time, in all of the signal lines D0 to D1 of the bus, the voltage changes from Low to High or vice versa, so that there is a high possibility that simultaneous switching noise occurs.

  Therefore, the image processing unit 7 of the present embodiment converts the data by the color space conversion unit 13 so as to suppress the occurrence of simultaneous switching noise. Specifically, the color space conversion unit 13 multiplies data having a predetermined number of bits input from the front end circuit 12 by a preset coefficient. For example, the coefficient multiplied by the color space conversion unit 13 may be a number less than 1 so that the maximum value of the data becomes small.

In the present embodiment, an example in which the color space conversion unit 13 uses the coefficient “240/255” is shown. In this case, the data P2 (0xFF) in FIG. 2A is converted into data P2 ′ (0xF0) as shown in the following formula (1). Data P1 (0x00) is converted to data P1 ′ (0x00), but the value does not change. Data P3 (0xFE) is converted to data P3 ′ (0xEF), and data P4 (0xF0) is converted to data P4 ′ (0xE1).
0x00 × 240/255 = 0x00 = 0b00000000
0xFF × 240/255 = 0xF0 = 0b11110000
0xFE × 240/255 = 0xEF = 0b11101111 (1)
0xF0 × 240/255 = 0xE1 = 0b11100001
The converted data is output from the color space conversion unit 13 in the order of data P1 ′, P2 ′, P3 ′, P4 ′.

  When the data P1 and P2 before conversion are compared, the value changes in all 8 bits. On the other hand, when the converted data P1 ′ and data P2 ′ are compared, the number of bits whose value changes is 4 bits. In the signal lines D0 to D7 that transmit the data P1 ′ and the data P2 ′, the voltage changes in half. That is, simultaneous switching noise is less likely to occur than before conversion. This effect is noticeable when data of the minimum value (0x00 in this example) is transmitted next to data of the maximum value (0xFF in this example) and vice versa. .

  In the example of FIG. 2A, by multiplying the coefficient “240/255”, the value of the lower 4 bits of the maximum value (0b11111111) is changed to 0b11110000. Since half of the 8-bit values constituting the data are changing, the effect of reducing simultaneous switching noise is high. Furthermore, as the value of 8-bit data, 0xFF is changed to 0xF0, but it can be said that this is only a slight decrease in the maximum value. Thus, by performing conversion that changes the value of the lower bit of the data, the amount of change in the value of the pixel data can be suppressed, and simultaneous switching noise can be effectively prevented.

The coefficient used by the color space conversion unit 13 for conversion is not limited to 240/255, and various values can be used, and the above coefficient is the most preferable example. For example, if the coefficient is 248/260, the maximum value (0xFF) of 8-bit data is converted to 0xF8 as shown in the following equation (2).
0xFF × 248/255 = 0xF8 = 0b11111000 (2)
In this case, when the data before conversion changes from 0x00 to 0xFF, the data after conversion changes from 0x00 to 0xF8, so the number of bits whose value changes decreases by 3 bits. Also in this case, it can be said that the occurrence of simultaneous switching noise can be suppressed and the change in the data value is small, which is preferable. Preferred coefficients for converting 8-bit data include coefficients that change some bits on the lower side of the maximum value (0xFF), and specifically include 224/260, 192/260, and the like.
Similarly, when 16-bit data or 32-bit data is converted by the color space conversion unit 13, a coefficient for converting the maximum value of the data so that the number of bits having a value “1” is reduced may be used. It is more preferable to use a coefficient that converts the value “1” to “0” in some of the lower-order bits with respect to the maximum value of the data because the change in the data value is small. Furthermore, it is preferable that the number of bits converted from “1” to “0” is larger because simultaneous switching noise is effectively suppressed.

The image data processed by the scaler 14 is processed by the LCD controller 16 and then inversely converted by the color space conversion unit 17.
The inverse transformation executed by the color space conversion unit 17 is a process in the reverse direction of the conversion process executed by the color space conversion unit 13. As shown in FIG. 2A, when the color space conversion unit 13 performs conversion by multiplying a coefficient less than 1, the color space conversion unit 17 performs conversion by multiplying the reciprocal of the coefficient.
Each data is input to the color space conversion unit 17 in the order of data P5, P6, P7, P8.
When the color space conversion unit 13 uses the coefficient “240/255”, the color space conversion unit 17 uses the coefficient “255/240”. In this case, the data P6 (0xF0) in FIG. 2B is converted into data P6 ′ (0xFF) as shown in the following equation (3). Data P5 (0x00) is converted to data P5 ′ (0x00), but the value does not change. Data P7 (0xEF) is converted to data P7 ′ (0xFE), and data P8 (0xE1) is converted to data P8 ′ (0xF0).
0x00 × 255/240 = 0x00 = 0b00000000
0xF0 × 255/240 = 0xFF = 0b11111111
0xEF × 255/240 = 0xFE = 0b11111110 (3)
0xE1 × 255/240 = 0xF0 = 0b11110000
The color space conversion unit 17 outputs the converted data in the order of data P5 ′, P6 ′, P7 ′, P8 ′,.

  Here, when processing RGB 24-bit color (16.77 million colors) image data, the color space conversion units 13 and 17 execute the above-described processing on each of 8-bit data of each color of RGB. In the 24-bit image data, the color space conversion units 13 and 17 respectively perform 8 bits corresponding to R data, 8 bits corresponding to G data, and 8 bits corresponding to B data. Conversion and inverse conversion are performed. When the image processing unit 7 processes 8-bit monochrome image data, the color space conversion units 13 and 17 convert and inversely convert 8-bit data as described above. Furthermore, the processing by the color space conversion units 13 and 17 can also be applied to image data of 30-bit color, 36-bit color, 42-bit color, 48-bit color and more bits as described above. In this case, the coefficients used by the color space conversion units 13 and 17 for conversion / inverse conversion may be coefficients that match the number of bits of data to be processed.

  As shown in FIGS. 2A and 2B, when the color space conversion unit 13 uses a coefficient less than 1 for image data conversion, the maximum value of the image data is substantially reduced. In other words, the color space conversion unit 13 performs a process of compressing the image data. For example, when the color space conversion unit 13 uses the coefficient “240/255”, the maximum value of 8-bit image data is compressed from 255 to 240. However, the color space conversion unit 17 performs a reverse conversion by multiplying the reciprocal of the coefficient used by the color space conversion unit 13 to increase the maximum value of the image data. For this reason, the maximum value of the image data is restored to 255. That is, since the color space conversion unit 17 performs the process of expanding the image data, there is no possibility that the contrast is deteriorated even if the process by the color space conversion unit 13 is performed.

As described above, in the image processing unit 7, the image data to be processed by the scaler 14 is converted by the color space conversion unit 13 before processing. When the scaler 14 develops image data in the frame memory 15 and executes the various image processing described above, a large amount of data is transmitted and received between the scaler 14 and the frame memory 15. In addition, with the advancement and speeding up of image processing, a display device such as the projector 1 employs a memory that can be driven at a higher speed. In the present embodiment, a configuration using the DDR memory 11 is shown as an example, but it is also possible to employ a higher speed DDR2 SDRAM, DDR3 SDRAM, or other standard memory device. Accordingly, simultaneous switching noise is particularly likely to occur in the bus B connecting the scaler 14 and the frame memory 15.
In the present embodiment, the color space conversion unit 13 located at the output stage of the front end IC 8 converts (compresses) the image data, so that the simultaneous switching noise in the bus B can be effectively suppressed.
Further, after the scaler 14 performs image processing, the color space conversion unit 17 located at the output stage of the LCD controller IC 10 performs reverse conversion (expansion) on the image data. For this reason, the contrast of the image data finally output does not deteriorate compared with the input image data. Therefore, it is possible to effectively suppress the occurrence of simultaneous switching noise in the scaler 14 without degrading the image quality.

In the image data processed by the projector 1, black pixel data has a minimum value (0x00), and white pixel data has a maximum value (0xFF). A minimum value (0x00) and a maximum value (0xFF) frequently appear in image data of an image composed of a white background and black characters. When processing such image data, a phenomenon in which the minimum value and the maximum value are continuously transmitted to the bus B frequently occurs, and there is a concern about the occurrence of simultaneous switching noise. When processing such image data, it is more effective to perform conversion and inverse conversion of the image data by the color space conversion units 13 and 17 as described above. On the other hand, when processing image data with few pixels of the maximum value (0xFF) or the minimum value (0x00), the data transmitted on the bus B changes from the minimum value (0x00) to the maximum value (0xFF), or Less likely to change to the opposite. For this reason, the effect of performing the conversion / inverse conversion by the color space conversion units 13 and 17 is relatively small.
Therefore, the image processing unit 7 determines the state of the image data under the control of the CPU 21, and when the simultaneous switching noise is effectively suppressed by the above method, the conversion / reverse of the color space conversion units 13 and 17 is performed. Conversion can be performed.

FIG. 3 is a flowchart showing the operation of the projector 1, and particularly shows the operation of controlling the execution of conversion / inverse conversion by the color space conversion units 13 and 17. In the operation of FIG. 3, the CPU 21 functions as a control means.
CPU21 starts the process of this FIG. 3, when the factor which changes the setting of the conversion / inverse conversion process by the color space conversion parts 13 and 17 generate | occur | produces (step S11). Factors for changing the setting include turning on the projector 1 and switching the image source. Here, the switching of the image source is an operation of switching an image supply device to be displayed when a plurality of image supply devices are connected to the interface 2, or an image supply device connected to the interface 2 is another device. It means that it can be replaced.

The CPU 21 controls the LCD controller 16 to create a histogram for one frame of image data output from the scaler 14 (step S12). Based on the histogram created by the LCD controller 16, the CPU 21 determines whether or not the ratio of all white pixels in the target frame is larger than a preset value X (step S13).
If the ratio of all white pixels is greater than the set value X (step S13; Yes), the CPU 21 determines whether the ratio of all black pixels in the target frame is greater than a preset value Y based on the histogram. Is determined (step S14).
An all-white pixel refers to a pixel whose image data has a maximum value, and an all-black pixel refers to a pixel whose image data has a minimum value. The set values X and Y are stored in the ROM 23, for example.

  When the ratio of all black pixels is larger than the set value Y (step S14; Yes), the CPU 21 determines to set the image processing unit 7 to the compression mode (step S15). The compression mode is an operation mode for performing conversion / inverse conversion by the color space conversion units 13 and 17. The CPU 21 specifies a conversion coefficient for the color space conversion unit 13 and sets the conversion processing to be executed (step S16). In addition, the CPU 21 specifies a conversion coefficient to the color space conversion unit 17 and performs a reverse conversion process (step S17).

  On the other hand, when the ratio of all white pixels is equal to or less than the set value X (step S13; No) and when the ratio of all black pixels is equal to or less than the set value Y (step S14; No), the CPU 21 7 is determined to be in the uncompressed mode (step S18). The non-compression mode is an operation mode in which the conversion / inverse conversion by the color space conversion units 13 and 17 is not performed. The CPU 21 sets the color space conversion unit 13 not to perform the conversion process (step S19). Further, the CPU 21 sets the color space conversion unit 17 not to perform the reverse conversion process (step S20). When the initial state of the image processing unit 7 is the uncompressed mode, the CPU 21 initializes the color space conversion units 13 and 17 in steps S19 and S20. Further, when a factor for changing the setting of the conversion / inverse conversion process occurs in the projector 1, the image processing unit 7 is set to the initial state, that is, the non-compression mode, and then the CPU 21 performs the operations after step S12. Good.

  With the operation of FIG. 3, the image displayed by the projection unit 3 is when all white pixels are larger than a predetermined ratio (set value X) and all black pixels are larger than a predetermined ratio (set value Y). In addition, conversion / inverse conversion by the color space conversion units 13 and 17 is performed. For this reason, the image processing unit 7 easily generates simultaneous switching noise, and performs conversion / inverse conversion by the color space conversion units 13 and 17 on an image suitable for reducing simultaneous switching noise by the above method. For this reason, simultaneous switching noise is effectively suppressed, and the processing load can be reduced when the effect of the above method is small.

As described above, in the projector 1 according to the embodiment to which the invention is applied, the image processing unit 7 includes the color space conversion unit 13, the scaler 14, and the color space conversion unit 17. The color space conversion unit 13 converts input image data having a predetermined number of bits, and the scaler 14 processes the converted image data converted by the color space conversion unit 13. The color space conversion unit 17 performs inverse conversion on the processed image data processed by the scaler 14 and outputs it. According to this configuration, it is possible to suppress the occurrence of simultaneous switching noise when image processing is performed by converting image data. In addition, since the inverse transformation is performed before outputting the image data, the influence on the output image can be suppressed.
Further, the color space conversion unit 13 performs conversion to reduce the number of bits whose value changes when the input image data changes from the minimum value to the maximum value or vice versa. As a result, it is possible to reduce the phenomenon that many bit values change simultaneously by converting the image data, and it is possible to more reliably suppress the occurrence of simultaneous switching noise.

Further, the color space conversion unit 13 performs conversion to change some values on the lower bit side of the input image data having a predetermined number of bits. By changing some values on the lower bit side, it is possible to reliably suppress the occurrence of simultaneous switching noise without greatly changing the value of data consisting of a plurality of bits.
Further, the CPU 21 determines whether or not conversion is necessary based on the ratio of all white pixels in the frame constituting the input image data. Accordingly, it is possible to quickly determine whether or not the input image data is a type of data that can effectively suppress simultaneous switching noise by performing data conversion. Then, conversion is performed on data that can be expected to have an effect, and conversion is omitted for data that is unlikely to have an effect, thereby reducing the processing load. Therefore, simultaneous switching noise can be suppressed more efficiently.

The scaler 14 is connected to the frame memory 15 by a bus B having a bus width of a predetermined number of bits. The scaler 14 executes processing for developing the converted image data in the frame memory 15. Then, the color space conversion unit 17 performs a process in the opposite direction to the conversion executed by the color space conversion unit 13 on the image data developed and processed in the frame memory 15 by the scaler 14. As a result, the scaler 14 converts the image data at a stage before accessing the frame memory 15 via the bus B and performing image processing. For this reason, simultaneous switching noise when accessing the frame memory 15 can be suppressed. Furthermore, since the reverse conversion is performed on the image data after the image processing, the influence on the image quality can be minimized.
In addition, the color space conversion unit 13 performs processing for converting the maximum value of the input image data into a smaller value. On the other hand, the color space conversion unit 17 converts the maximum value of the processed image data into the maximum value before being converted by the color space conversion unit 13. For this reason, generation | occurrence | production of simultaneous switching noise can be suppressed by simple processing. In addition, since the maximum value of the converted data is output after being processed to be the maximum value before conversion, image deterioration can be prevented.

  Furthermore, since the image data conversion / inverse conversion is performed by utilizing the arithmetic processing function of the color space conversion units 13 and 17, the present invention can be realized without adding dedicated hardware. Moreover, since radiation noise can be reduced, noise countermeasure components such as a shield plate can be reduced. Therefore, the cost can be reduced by reducing the number of parts and the degree of freedom in circuit design can be improved.

In addition, embodiment mentioned above does not limit this invention, It is also possible to apply this invention as an aspect different from the said embodiment. For example, in the above-described embodiment, the color space conversion units 13 and 17 have been described with an example in which a calculation using a predetermined coefficient is performed. The present invention is not limited to this. For example, the ROM 23 or the color space conversion units 13 and 17 hold a table associating the input data with the converted data, and the data may be converted according to this table. In this case, the table used for conversion by the color space conversion unit 17 may be set so as to perform conversion in the reverse direction corresponding to the table used for conversion by the color space conversion unit 13.
The display device of the present invention is not limited to a projector that projects an image on the screen SC. A liquid crystal monitor or liquid crystal television that displays images / images on a liquid crystal display panel, or a monitor device or television receiver that displays images / images on a plasma display panel (PDP), OLED (Organic light-emitting diode), OEL (Organic) Various display devices such as a monitor device for displaying an image / image on an organic EL display panel called “electro-luminescence” or a self-luminous display device such as a television receiver are also included in the image display device of the present invention.
Each functional unit of the projector 1 illustrated in FIG. 1 indicates a functional configuration, and a specific mounting form is not particularly limited. Furthermore, other specific details can be arbitrarily changed without departing from the gist of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Projector (display apparatus), 3 ... Projection part (display means), 7 ... Image processing part (image processing apparatus), 8 ... Front end IC, 9 ... Scaler IC, 10 ... LCD controller IC, 11 ... DDR memory, DESCRIPTION OF SYMBOLS 12 ... Front end circuit, 13 ... Color space conversion part (conversion means), 14 ... Scaler (image processing means), 15 ... Frame memory (memory), 16 ... LCD controller, 17 ... Color space conversion part (output means), 21 ... CPU (control means), SC ... screen.

Claims (9)

Conversion means for converting input image data of a predetermined number of bits;
Image processing means for processing the converted image data converted by the conversion means;
Output means for inversely converting and outputting the processed image data processed by the image processing means;
An image processing apparatus comprising: The image processing apparatus according to claim 1,
The image processing apparatus, wherein the image processing means comprises a hardware circuit having a bus for inputting and outputting the image data of the predetermined number of bits. The image processing apparatus according to claim 1 or 2,
The image processing apparatus according to claim 1, wherein the conversion means performs conversion to reduce the number of bits whose value changes when the input image data changes from a minimum value to a maximum value or vice versa. The image processing apparatus according to any one of claims 1 to 3,
An image processing apparatus comprising: control means for determining whether or not conversion by the converting means is necessary based on a white ratio in a frame constituting the input image data. The image processing apparatus according to any one of claims 1 to 4,
The image processing apparatus according to claim 1, wherein the conversion means performs conversion to change a value on a lower bit side of the input image data having the predetermined number of bits. An image processing apparatus according to any one of claims 1 to 5,
The converting means performs processing for converting the maximum value of the input image data into a smaller value, and the output means converts the maximum value of the processed image data into a maximum value before being converted by the converting means. An image processing apparatus. The image processing apparatus according to any one of claims 1 to 6,
The image processing means is connected to a memory by a bus having a bus width of the predetermined number of bits, and executes a process of developing the converted image data in the memory,
The image processing apparatus characterized in that the output means performs processing in a direction opposite to the conversion executed by the conversion means on the image data expanded and processed in the memory by the image processing means. An image processing method for converting image data,
A conversion process for changing the values of at least some of the bits of the input image data having a predetermined number of bits is performed.
Process the converted image data,
The image data after processing is converted and output in the reverse direction of the conversion process,
An image processing method characterized by the above. Conversion means for converting input image data of a predetermined number of bits;
Image processing means for processing the converted image data converted by the conversion means;
Output means for inversely converting and outputting the processed image data processed by the image processing means;
Display means for displaying the image data output by the output means;
A display device comprising:

Images