JP2019129464A - Projection apparatus and control method thereof - Google Patents

Abstract

To provide a projection apparatus and a control method thereof which can represent HDR gradations with respect to a change in the luminance on a projection surface while suppressing an increase in a memory.SOLUTION: A projection apparatus includes first acquisition means for acquiring a first gradation conversion characteristic on the basis of information defining a relationship between a gradation value of an image data to be projected and an absolute luminance value, second acquisition means for acquiring the maximum luminance of the projection surface in the projection apparatus, generation means for generating a second gradation conversion characteristic so as to satisfy the relationship between the gradation value and the absolute luminance value in at least some of gradation values on the basis of the first gradation conversion characteristic and the maximum luminance, luminance range conversion means for generating a luminance range converted image obtained by converting the luminance range of the image data on the basis of the first gradation conversion characteristic and the second gradation conversion characteristic, and applying means for applying gradation conversion based on the first gradation conversion characteristic to the luminance range conversion image, and supplying the image to projection means.SELECTED DRAWING: Figure 2

Description

The present invention relates to a projection apparatus and a control method thereof.

  Conventionally, image data has been compressed to a narrow dynamic range defined by a standard (for example, BT.709 (Rec. 709)) based on the assumption that it is displayed on a CRT (Cathode Ray Tube).

  However, at present, a display device having a wider dynamic range than a CRT such as a liquid crystal display device is generally used. On the contrary, there is a situation in which image data compliant with a conventional standard cannot fully utilize the capability of the display device. .

  Therefore, a standard that defines captured image data (hereinafter referred to as “HDR (High Dynamic Range) image data”) having a wider dynamic range than in the past has been proposed. The standard of HDR image data is, for example, ST. Proposed by SMPTE (Society of Motion Picture and Television Engineers). There are 2084. ST. Signal characteristics in the 2084 standard are defined by EOTF (Electro-Optical Transfer Function). And ST. The EOTF of 2084 is expressed by the following Expression 1, and a scene luminance value (video signal level) is assigned to an absolute display luminance range of a maximum of 10000 nit (or cd / m 2) (Patent Document 1).

  Here, L is display luminance (0 ≦ L ≦ 1, L = 1 corresponds to 10000 nit), and E ′ is a video signal level (digital value). M1, m2 and c1 to c3 are constants and ST. Specific values are defined in 2084. ST. The EOTF 2084 is also referred to as a PQ (Perceptual Quantization) curve because it has a non-linear quantization step according to human visual characteristics.

  For example, when such HDR image data is displayed on a general device (having a dynamic range wider than BT.709 but narrower than ST.2084), the display luminance range (input luminance range) of the image data is the display of the device. It may be wider than the luminance range (output luminance range). In this case, if the input luminance range is compressed according to the output luminance range and displayed, the entire display will be dark. When the luminance reduction due to the compression of the dynamic range is corrected, the tonality may be reduced or the original tonality may be broken due to the influence of the gradation lost by the compression. When the input luminance range is narrower than the output luminance range, there is a problem that even if the input luminance range is expanded and displayed in accordance with the output luminance range, it is not displayed with the correct gradation.

  In order to solve the above problems, Patent Document 2 obtains the luminance range of the projection surface, adjusts the light source accordingly so that the projection surface does not look dazzled, and adapts to the input image according to the light amount adjustment amount. Changing the LUT produces an image with improved contrast.

  As the types of luminance on the projection plane that can be displayed increase, the LUT to be possessed increases, and the required memory increases.

  In the projector described in Patent Document 2, the tonality is changed by changing the LUT (Look Up Table) of the projector according to the brightness around the projector and the minimum and maximum luminance on the projection plane, which changes with the projection distance. To be expressed correctly.

  For example, when the surrounding brightness is bright, the minimum brightness increases, and when the projection distance is large and the brightness on the projection plane is small, the influence of the decrease in contrast due to the surrounding brightness increases. In order to suppress this reduction in contrast, first, processing is performed to increase the amount of light of the projection device as the brightness of the surroundings becomes brighter or the projection distance increases, and the brightness of the surroundings gives the contrast of the projection device. Reduce the impact. At this time, not only the maximum luminance but also the intermediate luminance changes by changing the light quantity of the projection device. The LUT of the projection apparatus is changed so that gradation is correctly expressed by matching the overall luminance balance.

  In the case of this method, it is necessary for the projection apparatus to hold a plurality of LUTs in accordance with the types of brightness on the projection plane that can be supported. Since the luminance range that can be expressed by the PQ curve described above is as wide as 10,000 nits, ten types are necessary even if the luminance variation on the projection plane can be dealt with by dividing every 1000 nits steps. There is a problem that the amount of memory to be provided to the projection device is increased accordingly.

JP, 2015-159543, A JP, 2015-145892, A

  An object of the present invention is to provide a projection apparatus capable of representing gradations of HDR with respect to a change in brightness on a projection plane while suppressing an increase in memory, and a control method thereof.

In order to achieve the above object, a projection apparatus and a control method thereof according to the present invention include:
First acquisition means for acquiring a first gradation conversion characteristic based on information defining a relationship between a gradation value of the image data to be projected and an absolute luminance value;
Second acquisition means for acquiring the maximum luminance of the projection surface in the projection apparatus;
A second gradation conversion characteristic is generated based on the first gradation conversion characteristic and the maximum luminance so that the relation between the gradation value and the absolute luminance value is satisfied in at least a part of the gradation values. Generating means;
Luminance range conversion means for generating a luminance range converted image obtained by converting the luminance range of the image data based on the first gradation conversion characteristic and the second gradation conversion characteristic;
Applying means for applying gradation conversion based on a first gradation conversion characteristic to the luminance range conversion image, and supplying the projection means to the projection means;
And the luminance range conversion means approaches a gradation value after the gradation conversion characteristic is applied by the adaptation means to a gradation value after the second gradation conversion characteristic is applied to the image data. As described above, the brightness range conversion image is generated.

  According to the present invention, it is possible to provide a projection apparatus capable of representing gradations of HDR with respect to a change in brightness on a projection plane while suppressing an increase in memory, and a control method thereof.

FIG. 6 is a diagram showing a method of generating gradation conversion characteristics in the embodiment. Block diagram showing an example of the functional configuration of the projection apparatus according to the embodiment The flowchart regarding the basic operation | movement of the projector which concerns on embodiment. Flowchart for projection operation in the first embodiment A figure showing an example of a setting screen of a projection device concerning an embodiment FIG. 6 is a diagram showing a method of calculating a luminance conversion value according to the embodiment. The figure which shows the memory reduction amount which concerns on embodiment Flowchart relating to projection plane luminance acquisition operation of the second and third embodiments The figure regarding calculation operation of the projection distance in a 2nd embodiment The figure regarding projection surface luminosity acquisition operation in a 3rd embodiment

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to the following embodiments. The following embodiments do not limit the invention according to the claims, and all combinations of the features described in the embodiments are not necessarily essential to the solution means of the invention.

  Note that each functional block described in the present embodiment is not necessarily separate hardware. That is, for example, the functions of some functional blocks may be executed by one piece of hardware. Also, the function of one functional block or the function of multiple functional blocks may be performed by the coordinated operation of several hardware. Also, the function of each functional block may be executed by a computer program developed by the CPU on the memory.

First Embodiment
First, according to the brightness of the projection plane in the present case, a method of calculating the gradation conversion characteristic according to the PQ curve will be described.

  FIG. 1 shows a schematic diagram of a gradation expression method according to the PQ curve in Patent Document 2.

  The thin line in FIG. 1 represents the above-described PQ curve, the horizontal axis represents the luminance [nits] on the display surface, and the vertical axis represents the video signal level (digital signal), so-called gradation value. As shown in FIG. 1, it can be seen that in the PQ curve, the gradation values are linked at absolute luminance.

  First, the maximum luminance Lmax on the displayable display surface of the display device is acquired. Thus, the displayable luminance range is determined.

  The thick line shown in FIG. 1 is a display luminance conversion characteristic that converts the input gradation of a certain display device into the corresponding display luminance according to the PQ curve. The input tone value E'max or more is a tone value that can not be expressed due to the restriction of the displayable luminance range Lmax or less on the display surface of the display device. For this reason, even if a gray level equal to or higher than E′max is input, the maximum display luminance on the display surface of the display device is Lmax. Therefore, the luminance on the display surface is always constant at Lmax. That is, as shown in FIG. 2, 0 to E'max is a display gradation range that can be expressed by absolute luminance conversion according to the PQ curve.

  When the display luminance conversion characteristic is generated in this way, the display luminance at the gradation value of the corresponding PQ curve in the display device can be accurately expressed within the display luminance range of the display device.

  Finally, the display luminance range is converted to the corresponding tone value of the display device. For example, when the gamma of the display device is set to 2.2, the gradation value N corresponding to the luminance L can be expressed by the following equation (2).

  Through the above steps, it is possible to generate tone conversion characteristics conforming to the brightness on the display surface and the PQ curve.

  However, in the case of brightness with a configuration in which a plurality of types are provided stepwise and adaptively selected with respect to the continuous change in brightness, the above-mentioned types of brightness that can correspond to the gradation conversion characteristics described above If it is going to hold | maintain only a number, the memory amount which memorize | stores LUT like patent document 2 will increase.

  In this case, after applying the luminance conversion value that absorbs the difference in the LUT due to the brightness of the display surface in the actual environment from the gradation conversion characteristic generated so as to be adapted to the reference brightness, the gradation conversion characteristic is applied. I will explain how to suppress the increase in memory by applying.

FIG. 2 is a block diagram showing the internal configuration of the projection apparatus according to the first embodiment. FIG. 2A shows a block diagram of the projection apparatus 20 according to the first embodiment.
The control unit 210 controls the operation of each unit and includes, for example, a microcomputer such as a CPU and a memory. An instruction to each block constituting the projection device 20 is made from the control unit 210.

  The RAM 211 is a volatile memory that temporarily stores a control program and data as a work memory.

  The ROM 212 is a non-volatile memory that stores programs used by the control unit 210 and data such as setting parameters of each operation block and factory adjustment values. Also included is a conversion matrix for the camera acquired RGB values to the RGB output tone of the projection device, and an inverse conversion matrix.

  The operation unit 213 receives an input signal related to an operation of the projection apparatus 20 from the user. For example, it consists of a switch, a dial, a touch panel, etc., and accepts user's instructions. The operation unit 213 may have, for example, a signal reception unit that receives a signal from an external device that functions as a remote control. The control unit 210 executes an operation according to an operation of the operation unit 213 or an input from the communication unit 293. Here, the external device may be any electronic device that can receive a signal transmitted from the projection device 20 by the signal receiving unit of the external device and transmit a signal that can be recognized by the control unit 210. Examples of such electronic devices include, but are not limited to, personal computers, cameras, mobile phones, smart phones, hard disk recorders, game machines and the like.

  The image input unit 220 reads an image input to the projection device 20 and acquires image information such as resolution and frame rate together.

  The recording medium 221 can record still image data, moving image data, and other control data necessary for the projection apparatus of the present embodiment, and can be of any system such as a magnetic disk, an optical disk, or a semiconductor memory. It may be a recording medium. It may be a removable recording medium or a built-in recording medium.

  The recording / reproducing unit 222 reproduces still image data and moving image data from the recording medium 221. Furthermore, the recording and reproducing unit 222 receives still image and moving image data from the control unit 210 and records the data on the recording medium 221.

  The light source control unit 230 controls the amount of light output from the light source 260.

  The image processing unit 240 performs various image processing on the input image. Details will be described later.

  The light modulation element controller 250 applies voltage to each of the red (R), green (G), and blue (B) light modulation elements 270 to control the light intensity of each light modulation element 270. Modulate. The red (R) light modulation element modulates the red (R) light intensity. Green (G) and blue (B) also modulate the light intensity of each color.

  The light source 260 supplies light to the light modulation element 270.

  The light modulation element 270 modulates the light intensity emitted from the light source 260.

  The color synthesis unit 280 synthesizes red (R), green (G), and blue (B) light that has passed through the light modulation elements 270R, 270G, and 270B, and includes, for example, a dichroic mirror or a prism.

  The projection optical system 281 projects an optical image obtained by modulating the light supplied from the light source 260 by the red (R), green (G) and blue (B) light modulation elements 270 as a projection image. . The projection optical system 281 includes a plurality of lenses and an actuator for driving the lens. By driving the lens with the actuator, the projection image can be enlarged, reduced, or focused, and this drive is controlled by the projection optical system. This is performed by the unit 282.

  The projection optical system control unit 282 includes a control microprocessor and controls the projection optical system 282. Note that the projection optical system control unit 282 does not have to be a dedicated microprocessor. For example, the control unit 210 executes a program stored in the ROM 212 so that at least a part of the functions of the projection optical system control unit 282 is performed. The controller 210 may be realized.

  The imaging unit 291 captures a projection image formed by the projection optical system. Further, according to an instruction from the control unit 210, optical parameters such as a shutter speed and an aperture are changed.

  The captured image processing unit 292 generates a projection area cut out image obtained by cutting out a projection area indicating the projection surface luminance distribution from the captured image acquired by the imaging unit 291. A memory is held so that several past captured images or projection area cut-out images can be stored.

  The communication unit 293 communicates control signals, still image data, moving image data, and the like with an external device according to the control of the control unit 210. There is no limitation on the communication method and standard, and for example, communication conforming to one or more of wireless LAN, wired LAN, USB, Bluetooth (registered trademark) and the like can be performed. When the image input unit 130 conforms to HDMI (registered trademark), the communication unit 293 may perform CEC communication with an external device connected to the image input unit 220. If the terminal of the image input unit 220 is, for example, an HDMI (registered trademark) terminal, CEC (Consumer Electronic Control) communication may be performed via the terminal.

  The projection plane luminance acquisition unit 294 acquires the projection plane luminance. The method of acquiring the projection plane luminance will be described later.

  The input analysis unit 295 determines whether the input image has a format compatible with HDR. For example, when the input is HDMI 2.0a, the InfoFrame attached to the input image is read, and it is determined whether the input image is HDR compatible (PQ curve compatible). InfoFrame is SMPTE ST. Details are presented in the 2086 standard. When an image conforming to the PQ curve is input, the SMPTE ST.B in the area related to EOTF in the Dynamic Range and Mastering, which is one of the InfoFrame types. Information indicating that it is 2084 is stored. By reading this information, it can be determined that the HDR compatible image has been input. Also, the determination method is not limited to this.

  Further, the details of the internal configuration of the image processing unit 240 are shown in FIG.

  The correction target tone conversion characteristic calculation unit 2401 calculates a correction target tone conversion characteristic from the projection surface luminance acquired by the projection surface luminance acquisition unit 294. The correction target tone conversion characteristic is a tone conversion characteristic generated according to the PQ curve so as to be adapted to the acquired projection surface luminance.

  The luminance conversion value calculation unit 2402 uses the calculated correction target gradation conversion characteristics and the gradation conversion characteristics generated according to the PQ curve so as to adapt to a certain projection surface luminance held in advance by the projection device 20, Find the luminance conversion value to be applied to the input image. When this luminance conversion value is applied to the input image, the result obtained by multiplying the output by the gradation conversion characteristic has a smaller relative error with the correction target than the result obtained by simply applying the gradation conversion characteristic to the input image And the output result is close to the correction target. For example, the condition that the input / output characteristics become approximate characteristics is that the Max luminance of a certain gradation is close to the correction target, etc., and the condition is not limited to this.

  The luminance conversion unit 2403 applies the luminance conversion value obtained by the luminance conversion value calculation unit 2402 to the input image.

  The tone conversion characteristic processing unit 2404 performs tone conversion on the image output by the luminance range conversion unit 2403 using the tone conversion characteristic.

  The OSD superimposing unit 2405 superimposes an OSD (On Screen Display) such as an image quality adjustment GUI and a test pattern of the projection device 20 held in advance in the ROM 212 on an input image.

  The detailed processing method of the modules constituting the inside of the image processing unit 240 will be described later.

<Basic operation>
The basic operation of the projection apparatus 20 of the present embodiment will be described using the flowchart shown in FIG.

  The operation of each step shown in the flowchart of FIG. 3 is basically realized by the control unit 210 executing a program stored in the ROM 212 to control the functional blocks shown in FIG.

  FIG. 3 illustrates processing from the time when an instruction to turn on the power of the projection apparatus 20 is input through the operation unit 213 or an external device.

  When an instruction to turn on the power is input, the control unit 210 causes the power supply unit (not shown) to supply power to each unit of the projection apparatus 20.

  Next, the control unit 210 determines the display mode of the projection device 20 (S301). The display mode is specified from, for example, the operation unit 213 or an external device, and the display mode of the projection apparatus 20 of the present embodiment is any one of “input image display mode”, “file playback display mode”, and “file reception display mode”. However, it is not limited to these. In the “input image display mode”, the projection device 20 displays an image based on the video signal input from the image input unit 220. In the “file reproduction display mode”, the projection device 20 displays an image based on the data read from the recording medium 221 by the recording / reproducing unit 222. In the “file reception display mode”, the projection device 20 displays an image based on the data received from the communication unit 293. The display mode at the time of power on may be the display mode at the end of the previous time or a predetermined display mode. In this case, it is not always necessary to specify the display mode by the user.

  Here, it is assumed that the display mode is the “input image display mode” as a result of the determination in S301.

  In the "input image display mode", the control unit 210 determines whether a video signal is input from the image input unit 220 (S302), and if not determined to be input, it waits and is input. If it is determined that there is, the process proceeds to step S303.

  In step S303, the control unit 210 executes projection processing. The control unit 210 transmits the video signal input from the image input unit 220 to the image processing unit 240, and causes the image processing unit 240 to generate an image of one screen. The image processing unit 240 applies a necessary deformation process (for example, the number of pixels, a frame rate, and a shape) to the video signal to generate an image for one screen, and transmits the image to the light modulation element control unit 250. The light modulation element control unit 250 is configured to obtain the transmittance corresponding to the gradation level of each color component of red (R), green (G) and blue (B) of each pixel of the received image for one screen. The transmittance of each pixel of the light modulation elements 270R, 270G, and 270B is controlled.

  In addition, the light source control unit 230 controls the output of the light from the light source 260 based on, for example, the brightness of the surroundings based on the image obtained by the imaging unit 291. The light output from the light source 260 is separated into red (R), green (G), and blue (B) light, and is supplied as a light source of the light modulation elements 270R, 270G, and 270B. The light of each color whose transmittance is controlled for each pixel by the light modulation elements 270R, 270G, and 270B is combined by the color combining unit 280 and projected through the projection optical system 281.

  The control unit 210 controls a series of operations in these units in the projection process. The projection processing is sequentially performed until the input of the video signal is not detected or the end of the display is instructed.

  If, during the processing of S302 to S305, an instruction to change the angle of view (magnification) or focus of the projection optical system 281 is input from the operation unit 213, the control unit 210 instructs the actuator of the projection optical system 281. Drive according to.

  In step S304, the control unit 210 determines whether a display mode switching instruction is input from the operation unit 213. If it is determined that the display mode is input, the control unit 210 returns to step S210. Advance. When returning the process to S301, the control unit 210 transmits a menu screen for selecting a display mode as an OSD image to the image processing unit 240, and performs image processing so as to display the menu screen superimposed on the image being projected. The unit 240 is controlled. The user can operate the menu screen displayed in a superimposed manner using the operation unit 213 to select a desired display mode.

  On the other hand, in step S305, the control unit 210 determines whether or not an instruction to end projection is input from the operation unit 213. If it is not determined that the input is input, the process returns to step S302. The power supply to each block is stopped, and the process is ended. Through the above operation, the projection apparatus 20 in the input image display mode projects an image based on the video signal input from the image input unit 220.

  If it is determined in S301 that the display mode is the "file reproduction display mode", the control unit 210 causes the recording and reproduction unit 222 to read the file list of the recording medium 221 and the thumbnail data of each file, and causes the RAM 211 to Memorize temporarily. Then, the control unit 210 generates file selection screen data based on the character image based on the file list temporarily stored in the RAM 211 and the thumbnail data of each file, and transmits the data to the image processing unit 240. Then, the file selection screen is projected by the same process as the projection process (S303).

  When an instruction to select a specific image file is input from the file selection screen through the operation unit 213 or an external device, the control unit 210 controls the recording / reproducing unit 222 to reproduce the selected image file.

  The image data reproduced from the image file is transmitted from the recording / reproducing unit 222 to the image processing unit 240, and is projected by the image processing unit 240, the light modulation device control unit 250, and the light source control unit 230 through projection processing similar to S303. Ru. If the reproduction target is a moving image, reproduction and projection processing are sequentially performed for each frame. The control unit 210 executes the operation when there is an operation related to the projection optical system 281 and the operations shown in S304 and S305 as well as the input image display mode.

  When the display mode is determined to be the “file reception display mode” in S301, the control unit 210 causes the recording and reproduction unit 222 to reproduce the still image data and the moving image data received from the communication unit 293 in the file reproduction display mode. Project in the same way as image data. The control unit 210 executes the operation when there is an operation related to the projection optical system 281 and the operations shown in S304 and S305 as well as the input image display mode.

  Next, an HDR image display (projection) operation in the projection apparatus 20 of the present embodiment will be described. FIG. 4 shows a flowchart relating to the projection processing of the present embodiment.

  First, in accordance with an instruction from the control unit 210, the input analysis unit 295 determines whether the input image is an HDR image (S401). When the input interface is HDMI 2.0a, as described above, ST. This can be confirmed by looking at the 2084 signal. The above-described method is an example, and the method of determining whether the image is an HDR image is not limited to this.

  If it is determined that the input image is an HDR image as a result of the determination, the process proceeds to step S402 according to the flowchart of FIG. 4 (hereinafter, referred to as an HDR mode). If it is determined that the image is not an HDR image, that is, an SDR image, the process advances to step S408 to treat the input image as an SDR image.

  In step S408, the control unit 210, the image processing unit 240, the light modulation element control unit 250, and the light source control unit 230 execute a projection operation of image data (SDR image data) having a normal dynamic range such as sRGB. In this case, since the same processing as S302 to S305 in FIG. 3 may be executed, the following description is omitted. A series of projection operations targeting SDR image data is called an SDR mode operation.

  When it is determined in S401 that the mode is the HDR mode, the projection surface luminance acquisition unit 294 acquires the luminance of the projection surface according to an instruction of the control unit 210 (S402). Although there are various acquisition methods, in the first embodiment, the projection plane luminance acquisition unit 294 acquires the projection plane luminance by performing an operation that allows the user to select the luminance of the projection plane from a remote controller (not shown) or a touch panel. For example, there is a method in which a GUI for selecting the luminance of the projection plane is superimposed as an OSD on the input image and projected to give the user an option of the projection plane luminance and to make a selection with a remote controller (not shown). FIG. 5A shows an example of a GUI for causing the user to select the projection plane luminance.

  In the GUI shown in FIG. 5A, an “operation mode” can be used to select an operation mode for HDR images (HDR mode) or an operation mode for SDR images (SDR mode). Further, the "projection surface luminance" can directly specify the luminance value on the projection surface. Each item can be set by selecting a previously prepared option displayed according to the operation of selecting the item name. For example, FIG. 5A shows a state in which the item “projection surface luminance” is selected, and 1000 nits is selected out of four options that can be set. When the determination instruction is input in this state, the control unit 210 ends the display of the option, and displays a state in which 1000 nits is set as the projection surface luminance. When there is an instruction to end the display of the OSD, the control unit 210 displays an end confirmation screen, and selects whether to save the setting content or to end without saving. When the HDR mode is set in the GUI illustrated in FIG. 5A, the control unit 210 proceeds to S <b> 408, proceeds to S <b> 402 instead of performing image processing as SDR, and can handle it as an HDR image.

  Next, in accordance with an instruction from the control unit 210, the corrected target tone conversion characteristic calculation unit 2401 calculates a corrected target tone conversion characteristic. The method of calculating the gradation conversion characteristic from the brightness of the projection plane has been described above with reference to FIG.

  Next, in accordance with an instruction from the control unit 210, the luminance conversion value calculation unit 2402 acquires a luminance conversion value to be applied to the input image (S404). The luminance conversion value generally indicates that the gradation of the input image changes when it is applied to the input image, such as gain, LUT, and gamma. By applying the luminance conversion value to the input image, it is possible to absorb the difference of the gradation conversion characteristics according to the PQ curve due to the difference of the projection surface luminance. FIG. 6 is a schematic diagram for explaining a method of calculating a luminance conversion value. A method of calculating the luminance conversion value will be described with reference to FIG.

  The horizontal axis in FIG. 6 is the gradation value N of the input image, and the vertical axis is the output gradation value E 'when gradation conversion is performed according to the PQ curve.

  Also, the thick line in FIG. 6 is a tone conversion characteristic generated according to the PQ curve so as to be adapted to a certain projection surface luminance, which is held in advance by the projection device 20. Further, the thin line is the corrected target gradation conversion characteristic calculated in step S403. For example, when the projection surface luminance to which the gradation conversion characteristics set in the projection device 20 can be applied is larger than the actual projection surface luminance, the shape of the gradation conversion characteristics shown by thick and thin lines as shown in FIG. There will be a difference. By using the luminance conversion value described above, it is possible to fill in the difference in shape of the gradation conversion characteristics.

  The minimum input tone value when the output tone E ′ of the correction target tone conversion characteristic shown by the thin line in FIG. 6 is 1.0 is PA, and the tone conversion characteristic of the projection device 20 shown in bold is held in advance Let PB be the minimum input tone value when the output tone E ′ is 1.0. At this time, the luminance conversion value G is obtained by the equation (3).

  When the gradation conversion characteristic G originally obtained by applying the luminance conversion value G thus obtained to the input image is applied, a result close to the result of applying the corrected target gradation conversion characteristic to the input image can be obtained. .

  In this embodiment, the gain is obtained from the value of the input tone when the output tone E 'is 1.0, but the gain is not limited to this. Further, in the above method, when the input tone N is PA, the output tone 1.0 is the same as the correction target tone conversion characteristic, but there is a possibility that they will not match at a tone lower than PA. In order to improve the conversion accuracy of gradation lower than that of PA, the luminance conversion value G may be provided by a LUT constituted by a plurality of points.

  In the above-described procedures of S403 and S404, the luminance conversion value G is calculated from the projection surface luminance and the gradation conversion characteristic inside the projection device 20. However, since it takes time to calculate each time, a luminance conversion LUT in which the projection plane luminance and the luminance conversion value G are in one-to-one correspondence is held in the ROM 212 in advance, and luminance conversion is performed according to the projection plane luminance by using the LUT. It may be possible to convert it to the value G immediately and save the trouble of calculation.

When the luminance conversion value G and the gradation conversion characteristic are used in the above-described method, the memory can be reduced as compared with the configuration in which the gradation conversion characteristic is rewritten every time according to the projection plane luminance as in Patent Document 2.
FIG. 7 shows a schematic diagram of the memory reduction amount of the present embodiment. In FIG. 7, as an example, it is assumed that there are 10 types of projection plane luminances that can support HDR, and the gradation conversion characteristic is a 12-bit (= 4095 gradation) LUT defined by the PQ curve.

  The upper part of FIG. 7 shows a conventional method that does not use the luminance conversion value, and shows an approximation of the memory usage when updating the gradation conversion characteristic in accordance with the projection surface luminance. The white squares indicate one element of the LUT, and the gradations of the LUT exist. As shown in the upper part of FIG. 7, when ten types of LUTs are held so that the gradation conversion characteristics can be updated without using the luminance conversion value, the number of one element of the LUT, that is, the number of squares is 40950.

  On the other hand, as shown in the lower part of FIG. 7, when using the brightness conversion value as in the present embodiment, the difference in the shape of the gradation conversion characteristics due to the difference in projection plane brightness is compensated by the brightness conversion value, so the brightness conversion value is HDR. Ten types of projection surface brightness types that can be handled are required. In the above-described method, since the luminance conversion value is a certain gain value, it is sufficient to hold 10 gain values. In FIG. 7, for the sake of simplicity, the luminance conversion value and one element of the LUT constituting the gradation conversion characteristic are considered to have the same number of bits and are represented by the same square, but the number of bits may be different. Further, in the case of using the luminance conversion value, it is sufficient to hold one type of LUT as a reference, which can cope with HDR at a certain projection surface luminance in the gradation conversion characteristic. As a result, as shown in the lower part of FIG. 7, the number of squares when using the luminance conversion value is 4105. That is, under the precondition of FIG. 7, the memory reduction amount is about 10% when calculated. That is, when the luminance conversion value is used, it becomes possible to express the gradation of HDR with respect to the change of the brightness on the projection plane while suppressing the memory increase as compared with the conventional example.

  Next, in accordance with an instruction from the control unit 210, the luminance conversion unit 2403 performs gradation conversion by multiplying the input image with the acquired luminance conversion value (S405). Conversion is performed by applying the same luminance conversion value to each RGB color of the input image. As described above, when the projection plane luminance is smaller than the luminance that can be HDR converted by the gradation conversion characteristic held in advance by the projection device 20, the luminance conversion value becomes larger than one. When the gradation value is saturated by applying the luminance conversion value, clipping is performed at the maximum gradation value.

  Next, according to an instruction from the control unit 210, the gradation conversion characteristic processing unit 2404 performs gradation conversion on the output result of S405 according to the gradation conversion characteristic (S406). As described above, when gradation conversion based on the gradation conversion characteristics is performed on the input image multiplied by the luminance conversion value, an output image close to that obtained when the corrected target gradation conversion characteristics are applied to the input image is obtained. That is, a result close to that obtained when an HDR-compatible image with the obtained projection plane luminance is created.

  Finally, in accordance with an instruction from the control unit 210, the light modulation element control unit 250 projects the generated image by setting the light modulation factor matched to the image created in step S406 to the light modulation element 270RGB (S407). .

  Through the above steps, the HDR image can be generated and projected following the change in the projection plane luminance.

  In addition, the projection plane brightness is directly input from the GUI of FIG. 5A and obtained in step S402, but the setting value includes brightness information obtained from the other projection environments and the image quality setting values of the projection apparatus 20. And the brightness of the projection plane may be obtained from the information. FIGS. 5B and 5C show an example of a setting value setting GUI including brightness information of the projection plane. Hereinafter, FIG. 5B is referred to as an input setting screen, and FIG. 5C is referred to as a video setting screen.

The “operation mode” in the input setting screen shown in FIG. 5B has the same function as that shown in FIG.
Designate the size of the image projected by the projection device 20 (at a predetermined distance) by "Projection size" described in the input setting screen, or designate screen gain (reflectance) by "Screen gain". Can be. Each item can be set by selecting a previously prepared option displayed according to the operation of selecting the item name. For example, FIG. 5B shows that the item “projection size” is selected, and 150 inches is selected among the three options that can be set. Similarly, the item "screen gain" indicates a state in which a gain value of 1.5 is selected out of two selectable options. When a determination instruction is input in this state, the control unit 210 ends the display of options, and displays a state in which 150 inches as the projection size and the screen gain 1.5 are set. Note that the input setting screen can be switched to the video setting screen (FIG. 5C or the information display screen) by selecting the tab.

  On the other hand, among the items that can be set on the video setting screen shown in FIG. 5C, the setting values of “projection mode”, “brightness”, “contrast”, “gamma”, and “lamp mode” affect the light emission amount. To do. Therefore, the projection plane brightness acquisition unit 294 determines the value of the video setting parameter according to the current setting value regarding these items. The projector light quantity and the relationship between the setting value and the value coefficient of the video setting parameter are stored in a non-volatile storage device accessible by the projection plane luminance acquisition unit 294 such as the ROM 212 or the projection plane luminance acquisition unit 294, for example. be able to.

  Note that, for example, either “Presentation mode” or “Standard mode” can be set as the “projection mode”. Here, the "presentation mode" corresponds to the video setting parameter 1, and the "standard mode" corresponds to the video setting parameter (for example, 0.9) having a value lower than that of the "presentation mode". The “lamp mode” can be set to either “normal” or “energy saving”. “Normal” is a video setting parameter 1 and “energy saving” is a video setting parameter lower than “normal” (for example, 0. 0). It shall correspond to 9). Similarly, for other items, a relationship between a settable value and a corresponding video setting parameter is determined in advance. Therefore, the projection plane luminance acquisition unit 294 can determine the final image setting parameter value by multiplying the image setting parameter value corresponding to the setting value of each item. The relationship between the types of setting items that affect the light amount and the setting values and the image setting parameters described above is merely an example, and is not limited to these. In addition, the final image setting parameter value may be obtained by another method such as obtaining by referring to the correspondence between the combination of setting values and the image setting parameter value stored in advance.

  Using the setting values shown in FIGS. 5B and 5C, the projection plane luminance acquisition unit 294, based on the predetermined projector light amount, the received projection size, the screen gain, and the determined video setting parameter, For example, the projection plane luminance is calculated according to the following equation (4). In addition, if the unit of the projection size is inch, the projection surface luminance acquisition unit 294 converts it into square meter units and applies it to Equation (4).

  Here, the projector light quantity may be a value on the specification (for example, a measured value according to JIS X 6911: 2015). When the light amount changes depending on the setting, a predetermined reference light amount is set. Equation (4) gives the maximum brightness of the projection plane realized with the current settings.

  Through the above steps, it is possible to acquire the on-plane luminance from the setting value including the brightness information of the projection plane set by the user, and to generate the HDR image according to the projection-plane luminance.

Second Embodiment
Next, a second embodiment of the present invention will be described.

  Since the present embodiment may be the same as the first embodiment except for the projection plane luminance range acquisition process executed in S402 of FIG. 4, the projection plane luminance acquisition process in the present embodiment will be described below with reference to FIG. It demonstrates using the flowchart shown to (a).

  In the present embodiment, projection plane luminance is acquired using the focusing distance of the projection optical system 281.

  According to the instruction of the control unit 210, the projection surface luminance acquisition unit 294 acquires the focus lens position and the zoom lens position of the projection optical system 281 from the optical system control unit 282 (S801). These lens positions may be acquired by the control unit 210 from the optical system control unit 282 and notified to the projection plane luminance acquisition unit 294.

  Next, according to an instruction from the control unit 210, the projection plane luminance acquisition unit 294 calculates a projection distance (S802). For example, the projection surface luminance acquisition unit 294 reads the focal length of the focus lens stored in the ROM 212 in advance and the shortest distance between the light modulation element 270 and the focus lens. As shown in FIG. 9A, let A be the shortest distance between the light modulation element 270 and the focusing lens 283 which is included in the projection optical system 281 and moves in the range a. Also, let F be the focal length of the focus lens.

  Since the focus lens position acquired in S801 indicates a distance with the position shown in FIG. 9A being 0, the focus lens and the light are calculated from the focus lens position and the shortest distance A between the light modulation element 270 and the focus lens. The current distance A ′ to the modulation element 270 can be known. FIG. 9B shows the positional relationship between the light modulation element 270, the focus lens 283 of the projection optical system 281 and the screen 900. The projection plane luminance acquisition unit 294 uses the distance A ′ and the focal length F of the focus lens 283 to calculate the distance between the focus lens 283 and the screen 900, that is, the projection of the projection device 20, from the lens formula, equation (5). The distance B can be calculated.

Next, in accordance with an instruction from the control unit 210, the projection surface luminance acquisition unit 294 converts the current zoom lens position into a zoom magnification, for example, from the relationship between the zoom lens position and the zoom magnification stored in advance in the ROM 212. Then, the projection plane luminance acquisition unit 294 calculates the projection size from the projection distance B, the zoom magnification, and the size of the light modulation element 270 according to the following equation (6) (S803). The size of the light modulation element 270 may be, for example, the area [m ² ], or may be the size in the vertical and horizontal directions, the size of the diagonal, and the aspect ratio.

  Next, in accordance with an instruction from the control unit 210, the projection surface luminance acquisition unit 294 calculates projection surface luminance from the calculated projection size (S804). The calculation formula of the projection plane luminance using the projection size has been described in the formula (4) of the first embodiment, and thus the detailed description will be omitted. The method of acquiring setting values other than the projection size of equation (4) is the same as that of the first embodiment.

  According to this embodiment, the same effect as that of the first embodiment can be obtained. Further, in the present embodiment, since the projection size is obtained based on the actual projection distance, when the distance between the projection device 20 and the projection plane can be changed, the projection size set as in the first embodiment is used. It is possible to obtain projection plane brightness with higher accuracy than in the case of using.

  In the present embodiment, the projection distance is calculated using the position of the focus lens and the focal length. However, the projection apparatus 20 may be configured to directly measure the projection distance, or the projection distance may be determined by any other method. May be obtained.

Third Embodiment
Next, a third embodiment of the present invention will be described.

  Since the present embodiment may be the same as the first embodiment except for the projection plane luminance acquisition process executed in S402 of FIG. 4, hereinafter, the projection plane luminance acquisition process in this embodiment will be described with reference to FIG. It demonstrates using the flowchart shown to b).

  In the present embodiment, projection plane luminance is acquired using the imaging unit 291 disposed so as to be capable of photographing the optical axis direction (projection direction) of the projection optical system 281.

  First, after controlling each unit to project a specific image (in this case, a white image having the maximum gradation value of all pixels in order to obtain the maximum value of the projection plane luminance) according to an instruction from the control unit 210, The imaging unit 294 is instructed to shoot the projection plane (S811). FIG. 10A schematically shows an image 1000 obtained by the imaging unit 294. In the image 1000, reference numeral 1001 denotes a screen, and reference numeral 1002 denotes a white image projection image. The imaging unit 294 writes image data obtained by shooting in the RAM 211, for example.

  Next, in accordance with an instruction from the control unit 210, the captured image processing unit 292 acquires or calculates a pixel value (tone value) of the region of the projection image 1002 in the image 1000 stored in the RAM 211 (S812). Here, from the positional relationship between the optical axis of the imaging unit 291 and the optical axis of the projection optical system 281, it is assumed that the center position of the projected image 1002 in the image 1000 is known. Therefore, the captured image processing unit 292 calculates the tone value of the projected image 1002 based on the values of the pixels at the center position of the projected image or the pixels included in the predetermined range from the center in the image 1000. Alternatively, the captured image processing unit 292 may detect a region of the projection image 1002 by applying binarization or Hough transform, for example, to the image 1000, and calculate a gradation value based on all pixel values in the region. . For example, although the captured image processing unit 292 can calculate the gradation value by averaging pixel values, the gradation value may be calculated using another method.

  Finally, in accordance with an instruction from the control unit 210, the projection surface luminance acquisition unit 294 converts the gradation value calculated in S812 into projection surface luminance (S813). For example, a table or a conversion equation indicating the relationship between the gradation value and the projection surface luminance as shown in FIG. 10B can be stored in advance in the ROM 212, for example. Then, the projection surface luminance acquisition unit 294 can convert the projection surface luminance by referring to the table using the gradation value or substituting the gradation value into a conversion formula. The conversion table is measured, for example, before shipment of the projection apparatus 20 and stored in the ROM 212. In the example of FIG. 10B, the gradation value 255 is converted to the projection plane luminance 2000 [nit], and the gradation value and the projection plane luminance have a linear relationship. The value of the surface brightness and the change characteristics of both are not limited to this.

  As described above, the projection plane luminance acquisition unit 294 determines the projection plane luminance and notifies the control unit 210 of it.

  According to this embodiment, the same effect as that of the first embodiment can be obtained. For example, when a light source is provided for each region, the projection plane luminance can be obtained for each region corresponding to the light source. For example, the area of the projected image may be divided into areas corresponding to the light sources, and gradation values may be obtained for each area based on the pixels in the divided areas and converted to projection plane luminance.

  As mentioned above, although this invention was demonstrated using some exemplary embodiment, this invention is not limited to the specific structure described in embodiment, In the range of the invention prescribed | regulated by a claim Various modifications and variations are possible.

<Fourth Embodiment>
The present invention supplies a program that implements one or more functions of the above-described embodiments to a system or apparatus via a network or storage medium, and one or more processors in a computer of the system or apparatus read and execute the program. Can also be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

20 projector, 210 control unit, 220 image input unit, 240 image processing unit,
250 light modulation element control unit, 260 light source, 270 light modulation element,
281 Projection optical system, 294 Projection plane luminance acquisition unit, 295 Input analysis unit

Claims (9)

A projection device,
First acquisition means for acquiring a first gradation conversion characteristic based on information defining a relationship between a gradation value of the image data to be projected and an absolute luminance value;
Second acquisition means for acquiring the maximum luminance of the projection surface in the projection apparatus;
A second gradation conversion characteristic is generated based on the first gradation conversion characteristic and the maximum luminance so that the relation between the gradation value and the absolute luminance value is satisfied in at least a part of the gradation values. Generating means;
Luminance range conversion means for generating a luminance range converted image obtained by converting the luminance range of the image data based on the first gradation conversion characteristic and the second gradation conversion characteristic;
Applying means for applying gradation conversion based on a first gradation conversion characteristic to the luminance range conversion image, and supplying the projection means to the projection means;
And the luminance range conversion means approaches a gradation value after the gradation conversion characteristic is applied by the adaptation means to a gradation value after the second gradation conversion characteristic is applied to the image data. As described above, a projection apparatus that generates a brightness range converted image. The said 2nd acquisition means acquires the maximum brightness | luminance of the said projection surface based on the predetermined | prescribed reference light quantity of the said projection apparatus, screen gain, and projection size. Projection device. The projection apparatus according to claim 2, wherein the second acquisition unit acquires the maximum luminance of the projection plane using a coefficient determined by a setting value of the projection apparatus. 4. The apparatus according to claim 2, wherein the second acquisition unit calculates the projection size based on a projection distance by the projection unit and a zoom magnification of a projection optical system of the projection unit. The projection device described. 5. The projection apparatus according to claim 4, wherein the second acquisition unit calculates the projection distance based on information on the position and focal length of a focus lens included in a projection optical system included in the projection unit. . The projection apparatus according to claim 1, wherein the second acquisition unit acquires the maximum luminance of the projection plane based on an image obtained by photographing the projection plane. 7. The projection apparatus according to claim 6, further comprising an imaging unit configured to capture an image of the projection plane. A method for controlling a projection device, comprising:
A first acquisition unit acquires a first gradation conversion characteristic based on information defining a relationship between a gradation value of image data to be projected and an absolute luminance value;
A second obtaining unit obtaining a maximum brightness of a projection surface in the projection apparatus;
A generation unit configured to generate a second gradation so that the relationship between the gradation value and the absolute luminance value is satisfied in at least a part of the gradation values based on the first gradation conversion characteristic and the maximum luminance; Generating a conversion characteristic;
Generating a luminance range converted image by converting the luminance range of the image data based on the information and the second gradation conversion characteristic;
Applying means for applying gradation conversion based on a first gradation conversion characteristic to the luminance range conversion image and supplying it to a projection means;
And the luminance range conversion means approaches a gradation value after the gradation conversion characteristic is applied by the adaptation means to a gradation value after the second gradation conversion characteristic is applied to the image data. As described above, a method for controlling a projection apparatus is characterized by generating a luminance range converted image. The program for functioning the control method of Claim 8 by reading and running the computer which a projection apparatus has.