JP2009210928A - Image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the quality of an image displayed in a low pass filter mode in an image display device capable of displaying a pixel shift. <P>SOLUTION: The image display device includes: a pixel shifting/enlarging display section which includes a display element 12, a pixel displacing element 13, and an enlarging optical system; and a display control section 3 which controls the pixel shifting/enlarging display section in a pixel shifting mode or a low pass filter mode in synchronization with the timing of the shift of pixels by the pixel displacing element 13. In the pixel shifting mode, images displayed on display elements 12 are made different corresponding to different spatial positions, thereby securing high definition display. In the low pass filter mode, images displayed on the display elements 12 during one or more periods in which the pixel shifting element 13 shifts pixels are made to be the same images. In the image display device, the display control section 3 performs control so that a pixel shifting frequency in the low pass filter mode becomes higher than a pixel shifting frequency in the pixel shifting mode. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image display device that enables high-definition display that is greater than the number of pixels included in a display element by shifting pixels.

  In recent years, high-definition (HD) broadcast receivers, that is, so-called high-definition televisions are becoming increasingly popular. In addition, personal computers (PCs) have improved processing performance, and display devices connected to the PCs have been increased in pixel count. As described above, the resolution of various display devices is increasing in the living environment.

  With such high resolution of various display devices, portable information terminals (for example, PDAs (Personal Digital Assistants) and mobile phones) that are miniaturized display devices so as to be portable can also be used. The number of display pixels tends to increase.

  However, since the portable information terminal is configured with a small casing, it is difficult to ensure a large absolute amount of display area. Various means are conceivable to solve such a point. One example is an electronic view finder (hereinafter referred to as EVF (Electronic View Finder) as appropriate. Here, the EVF is displayed on a small display element or the like. This is a type of viewfinder that magnifies and observes an image through an eyepiece or the like as a means for displaying an image on a portable information terminal. This EVF is used by looking into the eyepiece lens. Since the virtual image can be enlarged and observed, it is possible to display a pseudo large screen. Therefore, by combining this EVF with a portable information terminal, there is an advantage that a large screen display can be observed with high pixels even in a portable information terminal which is a small device.

  By the way, since the EVF is generally configured to use a small display element, if an attempt is made to increase the number of pixels of the display element, the area per pixel becomes considerably small. However, if the area per pixel is reduced, manufacturing problems such as a decrease in yield and a limit in the manufacturing process occur.

  As a technique that can cope with such a problem, there is a technique of increasing the pixel and resolution using time-series pixel shifting. This pixel shifting technique is a technique that allows a plurality of pixel positions to be displayed by one pixel by shifting the position of the pixel viewed from the observer (apparent pixel position) in time series.

  By the way, even in a display device capable of increasing the number of pixels by pixel shifting, it is not always desirable to perform pixel shifting to perform high pixel display. For example, when the resolution of the input video signal is lower than the original resolution of the display element, it is not recognized that it is particularly necessary to perform high pixel display. In addition, in the case of a battery-powered device, when the remaining battery level is low, it may be necessary to display for a longer time without performing a high pixel display than for a short time display with a high pixel display. is there. In addition, in an imaging apparatus or the like that can capture still images and moving images, the still image may be displayed with high definition, while the frame rate may be more important than the definition of moving images.

  As a technique for controlling the pixel shift mode in accordance with the format of the input video signal, for example, a technique described in Japanese Patent Laid-Open No. 2001-157229 can be cited. This publication further describes in detail that a pixel shifting element is configured by combining a TN liquid crystal and a birefringent plate.

  Similarly, in paragraphs [0085] to [0093] of Japanese Patent Laid-Open No. 2005-241870, pixel shift is performed when the information amount of the input video signal is larger than the display information amount of the display element. A technique for changing the pixel shift mode is described so that the pixel shift is not performed when the amount of information is less than or equal to the information amount. Further, in this publication, when the information amount of the input video signal is equal to or less than the display information amount, the pixel shifting element is not in the middle state between ON and OFF, instead of simply performing pixel shifting. A technique for reducing the graininess of an image by performing simultaneous display at a plurality of pixel positions achieved by pixel shifting is described.

  By the way, when an image of a liquid crystal display element on which a black matrix with a predetermined pitch is formed is projected on a screen on which a lenticular lens with a predetermined pitch is formed, moire fringes may be generated due to pitch mismatch. Therefore, Japanese Patent Laid-Open No. 4-125536 discloses that a parallel plate glass is disposed in an optical path between a liquid crystal display element and a projection lens so as to be inclined in only one of a horizontal direction and a vertical direction. A technique is described that reduces the moire fringes by reducing the resolution and prevents the resolution from decreasing in the other direction.

In addition, since the pixel shifting technique described above is a technique in which the pixel position is temporally displaced, when the pixel shifting frequency is low, the image feels finely swayed (feels a feeling of vibration and a feeling of rocking). It can happen. In view of this, the present applicant has already investigated and described the relationship between the pixel shift frequency and the ratio of people who feel pixel shaking in Japanese Patent Application Laid-Open No. 2007-192919.
JP 2001-157229 A JP-A-2005-241870 JP-A-4-125536 JP 2007-192919 A

  As described above, for example, when the resolution of the input video signal is low, there is no necessity to perform pixel-shifted display. However, simply fixing the pixel shifting element to either the on state or the off state causes a reduction in the proportion of pixels (aperture ratio) in the display screen, causing a grainy image. On the other hand, it is also conceivable to suppress the decrease in the aperture ratio by making the images displayed on the display element the same during one cycle while performing the pixel shifting at the same cycle as the pixel shifting. However, even in this case, the problem described below remains.

  That is, as a display element, a liquid crystal display element or the like is currently widely used. However, it is difficult to increase the frequency for switching image information displayed by the display element so much, for example, a frame frequency of 30 Hz or Generally, it is about 60 Hz.

  On the other hand, the pixel shifting element generates mechanical vibration using a piezoelectric element or the like in addition to the method of combining a TN liquid crystal and a birefringent plate as described in the above Japanese Patent Application Laid-Open No. 2001-157229. There are various methods such as a method using a digital micromirror device, and a method capable of realizing a high frequency.

  However, in a display device capable of pixel shifting, when driving in the pixel shifting mode, it is necessary to synchronize the frequency of the pixel shifting element with the frequency of the display element, so that pixel shifting can be performed at a very high speed. First, there is a possibility that the observer may feel a sense of pixel swing as described in Japanese Patent Application Laid-Open No. 2007-192919.

  Further, as described in Japanese Patent Application Laid-Open No. 2005-241870, a technique for reducing the graininess of an image by increasing the aperture ratio of the pixel by setting the pixel shift element in an intermediate state between on and off is a swing feeling. However, it is not easy to accurately control the pixel shifting element to the intermediate state so that one pixel on the display element is displayed at the same luminance at a plurality of observation pixel positions. In addition, usable pixel shifting elements are limited to pixel shifting elements of a type that can display at a plurality of observation pixel positions in an intermediate state (that is, a mechanical pixel shifting method or a digital It cannot be applied to a method of shifting pixels using a mirror device).

  The present invention has been made in view of the above circumstances, and in an image display device capable of performing pixel-shifted display, can improve the image quality of an image displayed when high-resolution display by pixel shift is not performed. The purpose is to provide.

  In order to achieve the above object, an image display device according to the present invention performs a pixel shift that periodically changes a spatial position of an image displayed on a display element and the display element at a predetermined pixel shift frequency. In synchronization with a pixel shift enlargement display unit including a shift element, an enlargement optical system that enlarges an image displayed on the display element and that passes through the pixel shift element, and a timing at which the pixel shift element performs pixel shift, A pixel shift mode for performing high-definition display with a number of pixels that is a multiple of the number of pixels included in the display element by making the image displayed on the display element different images corresponding to different spatial positions, and the pixel shift element And a low-pass filter mode in which an image displayed on the display element is the same image during a period of one cycle or more during which pixel shift is performed. Therefore, the display control unit controls the pixel shift enlarged display unit, and the display control unit has a pixel shift frequency in the low-pass filter mode higher than a pixel shift frequency in the pixel shift mode. As described above, the pixel shift enlarged display unit is controlled.

  According to the image display device of the present invention, in an image display device capable of performing pixel-shifted display, it is possible to improve the image quality of an image displayed when high-resolution display by pixel shift is not performed.

  Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1]
FIGS. 1 to 7 show Embodiment 1 of the present invention. FIG. 1 is a block diagram showing the configuration of the image display apparatus, and FIG. 2 is a flowchart showing the operation of the image display apparatus.

  As shown in FIG. 1, the image display device includes a preprocessing circuit 1, a frame memory 2, a display control unit 3, a power supply unit 6, a power supply state determination unit 7, a pixel shift display determination unit 8, A field memory 9, a timing controller 10, a backlight 11, a display element 12, and a pixel shifting element 13 are provided. The image display device is also provided with a magnifying optical system for enlarging an image displayed on the display element 12 and passing through the pixel shifting element 13, but this magnifying optical system has an optical configuration and is electrically Since it is not a structure, illustration is abbreviate | omitted in this FIG. However, this magnifying optical system will be described later with reference to FIG. 7 showing a digital camera as an application example of the image display device.

  The pre-processing circuit 1 receives video signals in various formats such as still images / moving images, video signals from PCs (with different resolutions and refresh frequencies), and television video signals (NTSC, PAL, HD, etc.). It has become so.

  The preprocessing circuit 1 performs frame rate conversion (for example, to match the display rate of the display element 12) or IP (interlaced) in order to display these various types of video signals on this pixel-shifted display device. (Progressive) conversion, resolution conversion so as to match the resolution of the pixel shift display device, or color space conversion. Here, the resolution conversion is performed so that an image corresponding to the apparent resolution after the pixel shift is performed in the case of performing display in the pixel shift mode, and in the case of performing display in the low pass filter (LPF) mode, This is performed so that an image corresponding to the resolution of the display element 12 is obtained. Note that when the image display device is applied to a specific device such as a digital camera, that is, a device in which an obtained video signal is specified, the preprocessing circuit 1 is not always necessary. Here, it is shown as a dotted block.

  The frame memory 2 is a storage unit for storing the video signal processed by the preprocessing circuit 1 in units of frames.

  The display control unit 3 controls the display system including the backlight 11, the display element 12, and the pixel shift element 13, and pixel shift control for controlling various display modes including the pixel shift mode and the LPF mode. Part 4 is provided. The pixel shift control unit 4 includes an LPF mode control unit 5 for controlling the LPF mode among the display modes.

  The power supply unit 6 is for supplying power to each part of the image display device, and a battery or an external power supply can be used as the power supply.

  The power supply state determination unit 7 is for determining the state of the power supply unit 6. That is, the power supply state determination unit 7 determines whether the power supply unit 6 uses an external power supply as a power supply or a battery as a power supply. Furthermore, when the power supply state determination unit 7 determines that the battery is used as the power supply, the power supply state determination unit 7 determines the remaining battery level based on the voltage or the like. The power supply state determination unit 7 shifts the determination result to the display determination unit 8 by shifting the pixel.

  The pixel shift display determination unit 8 acquires at least information about the resolution of the input video signal from the preprocessing circuit 1 and further acquires information about the power source from the power state determination unit. Then, the pixel shift display determining unit 8 determines whether or not to perform the pixel shift mode display as described below (step S1).

  That is, the pixel shift display determination unit 8 provides information indicating that the drive is performed in the LPF mode when the resolution of the input video signal is equal to or lower than the display resolution of the display element 12 and the display control unit 3. Output to. Further, when the resolution of the input video signal is higher than the display resolution of the display element 12, the pixel shift display determination unit 8 uses an external power source as the power source or uses a battery as the power source, and When the remaining amount is equal to or greater than the predetermined amount, information indicating that driving is performed in the pixel shift mode is output to the preprocessing circuit 1 and the display control unit 3. On the other hand, even if the resolution of the input video signal is higher than the display resolution of the display element 12, the pixel shift display determination unit 8 uses a battery as a power source and the remaining amount is less than a predetermined amount. , Information indicating that driving is performed in the LPF mode is output to the preprocessing circuit 1 and the display control unit 3.

  When the preprocessing circuit 1 acquires the information indicating that the driving is performed in the LPF mode from the pixel shift display determination unit 8, the preprocessing circuit 1 converts the video signal into a resolution equal to the display resolution of the display element 12 and transfers it to the frame memory 2. Output. On the other hand, when the preprocessing circuit 1 acquires the information indicating that the driving is performed in the pixel shift mode from the pixel shift display determination unit 8, the preprocessing circuit 1 converts the video signal to the display resolution of the display element 12 × (pixel shift in one period) The resolution is equal to the number of pixel movement positions) and output to the frame memory 2. For example, as shown in FIG. 3 and the like described later, when the four-point pixel shift is performed, the preprocessing circuit 1 displays the video signal with display resolution × 4 ([vertical display resolution × 2] × [horizontal display resolution × 2]. ) And output to the frame memory 2.

  When the display control unit 3 acquires information indicating that driving is performed in the pixel shift mode from the pixel shift display determination unit 8, the display control unit 3 reads the video signal for one frame from the frame memory 2 and corresponds to each pixel shift position. The generated field data is generated and stored in the field memory 9. The display control unit 3 supplies the field data to the display element 12 after turning on the backlight 11, and controls the pixel shift element 13 to shift the pixel to the pixel position where the field data is to be displayed. (Step S2).

  On the other hand, when the display control unit 3 acquires information indicating that driving is performed in the LPF mode from the pixel shift display determination unit 8, the display control unit 3 displays the frame data read from the frame memory 2 during the display period of one frame. 12, the pixel shift element 13 is driven to perform pixel shift at a higher pixel shift frequency than in the pixel shift mode, as will be described later (step S <b> 3). Therefore, when driving in the LPF mode, it is not necessary to generate field data, so that power consumption can be reduced and the amount of heat generated can be suppressed.

  The timing controller 10 generates a timing signal (reference signal) for matching the timings of the frame memory 2, the display control unit 3, and the field memory 9 and outputs them to these. The reference signal output from the timing controller 10 is used by the display control unit 3 when controlling the drive timing of the display system including the display element 12, the pixel shifting element 13, or the backlight 11.

  The backlight 11 is a light source that illuminates the display element 12 from the back side, and includes a drive circuit and the like.

  The display element 12 is a spatial modulation unit that spatially modulates light from the backlight 11 in accordance with an image signal, and is configured by arranging a plurality of pixels in a two-dimensional manner. The display element 12 includes a drive circuit and the like.

  The pixel shifting element 13 moves the pixel position of the display element 12 in time series, and includes a drive circuit and the like. The pixel shifting element 13 may be of a type in which a TN liquid crystal (polarization switching liquid crystal) and a birefringent plate are combined as described in JP 2001-157229 A, or a piezoelectric element or the like is used. It is also possible to use a system that mechanically generates vibrations, a system that uses a digital micromirror device, or other various systems.

  FIG. 3 is a timing chart showing the display state of the display element, the reference signal, and the pixel shift state in the pixel shift mode.

  In the present embodiment, a four-point pixel shift as shown in FIG. 3C is assumed, and the upper left pixel position A, the upper right pixel position C, the lower left pixel position B, the lower right pixel position D, It is assumed that pixel shifting to the four pixel positions is performed. Of course, this four-point pixel shift is merely an example, and may be a two-point pixel shift or other multi-point pixel shift.

  In this case, the display control unit 3 uses frame data of [(vertical display resolution of the display element 12) × 2] × [(horizontal display resolution of the display element 12) × 2] stored in the frame memory 2. The field data of the pixel position A, the field data of the pixel position B, the field data of the pixel position C, and the field data of the pixel position D are respectively created as display resolution data of the display element 12, and the field memory 9 In FIG. 3, the data of the pixel positions A, B, C, and D in the first frame are indicated as A1, B1, C1, D1, and the like (the same applies to the second frame).

  Then, the display control unit 3 supplies the display element 12 with, for example, field data at the pixel position A for display in a certain field period in synchronization with the reference signal output from the timing controller, and causes the pixel shift element 13 to display the field data. The pixel shift element 13 is controlled so as to shift the pixel to the pixel position A (pixel shift).

  Next, in synchronization with the reference signal output from the timing controller 10, the display control unit 3 supplies the display element 12 with field data at the pixel position C for display in the next field period, and displays the pixel shift element. The pixel shift element 13 is controlled so as to cause the pixel shift to the pixel position C (pixel shift).

  Similarly, the pixel position B and the pixel position D are displayed in the next field period and the next field period.

  Here, it is assumed that the reference signal output from the timing controller 10 is a signal having a field period, for example, a frequency of 120 Hz.

  Therefore, in the present embodiment in which four-point pixel shifting is performed, the frequency of one frame composed of four fields is 30 Hz.

  This period (field period, frame period) is determined in consideration of the frame rate (frame frequency) of the video signal input to the preprocessing circuit 1 and the display rate (display frequency) achievable by the display element 12. It has been done. That is, for example, the display element 12 using an LCD, for example, often displays at a display rate of about 30 Hz or 60 Hz at present. In the four-point pixel shift as shown in FIG. 3, since the display must be switched four times for each frame, the timing of driving at a display rate of 60 Hz is further increased to a display rate of 120 Hz by driving at a double speed. Has achieved. The pixel shift rate of the pixel shift element 13 (the pixel shift frequency that makes a round of the pixel positions A to D) matches the display rate for four fields of the display element 12 (that is, the rate for displaying one frame), And since it is necessary to synchronize, it is 30 Hz.

  Next, FIG. 4 shows the display state and reference signal of the display element 12 in the LPF mode achieved by making the field data supplied to the display element 12 the same during one frame period in the pixel shift mode shown in FIG. It is a timing chart which shows a pixel shift state.

  For each of the fields at pixel positions A, C, B, and D in one frame period, the field data supplied to the display element 12 is, for example, field data at the pixel position A (in the LPF mode, as described above. Since the field data is not generated, only the frame data read from the frame memory 2 is actually used), so that the displayed pixel data is the same even if the pixel position (pixel shift position) is different. Accordingly, an image having the same resolution as that of the display element 12 is displayed (that is, although pixel shift itself is performed, high-resolution display by pixel shift is not performed), and LPF mode display is performed. Become.

  When driving as shown in FIG. 4 is performed, the frequency of one frame is 30 Hz, and the frequency of pixel shift is 30 Hz (one pixel position of pixel shift is displayed, as in the pixel shift mode described above. The frequency corresponding to time is 120 Hz).

  By the way, when the pixel shift is performed, the pixel position where the same pixel data is displayed moves according to the pixel shift. Therefore, the pixel shift rate (one cycle in which this pixel shift is performed is as described above. If the period is the same as the period of one frame, the pixel is observed as if it is finely oscillated. FIG. 5 is a chart showing the relationship between the display frame rate and the percentage of people who can tolerate pixel shaking.

  As shown in the figure, when the display frame rate is 30 Hz, the percentage of people who can tolerate pixel shaking is only 20%. However, when the display frame rate is 40 Hz, the display frame rate is 45 Hz. In some cases, it increases to 80%, and to 90% if the display frame rate is 60 Hz. As described above, the applicant has obtained an experimental result that the higher the display frame rate, that is, the higher the pixel shift frequency, the more difficult it is to perceive pixel shaking.

  Therefore, when the LPF mode display as shown in FIG. 4 is performed, the percentage of people who can tolerate pixel shaking is relatively low (for example, 20%). It is desirable to increase the frequency. Accordingly, drive timing for performing higher-quality LPF mode display will be described with reference to FIG.

  FIG. 6 is a timing chart showing the display state of the display element, the reference signal, and the pixel shift state in the high quality LPF mode in which the pixel shift is performed at a higher rate than the pixel shift rate in the pixel shift mode.

  In the LPF mode, the rate at which one frame is displayed by the display element 12 and the pixel shift rate of the pixel shift element 13 do not have to be the same. FIG. 6 shows an example in which the pixel shift rate is made faster than the rate at which one frame is displayed in order to reduce the sense of rocking caused by pixel shift.

  In the example shown in FIG. 6, the pixel shift rate of the pixel shift element 13 is set to twice the rate at which one frame is displayed on the display element 12 (that is, the pixel shift rate in the pixel shift mode), and the drive timing Are trying to synchronize.

  That is, field data supplied to the display element 12 in one frame period (frequency: 30 Hz) is field data at the same pixel position (for example, field data at pixel position A), and pixel shift is performed by two periods in one frame period. (That is, A → C → B → D → A → C → B → D), and the drive timing of the pixel shifting element 13 and the drive timing of the display element 12 are synchronized. As a result, the pixel shift rate (the rate at which the pixel position makes a round) is 60 Hz. As can be seen from FIG. 5, the percentage of people who can tolerate pixel shaking is greatly increased (for example, to 90%). can do. Since the display element 12 has a response time for switching the display, if the pixel shift method as described in the above-mentioned Japanese Patent Application Laid-Open No. 2001-157229 is used at the time of switching the display, the density changes, and the piezoelectric element or the like. If the pixel shift method that mechanically generates vibration using the pixel shifts, the space between the pixels is changed. However, by synchronizing the drive timing of the pixel shift element 13 and the drive timing of the display element 12, It becomes easy to perform control to prevent unevenness such as a decrease in pixel density only at the pixel position. Therefore, in this embodiment, in the LPF mode, the driving as shown in FIG. 6 is performed instead of the driving as shown in FIG.

  Then, referring to the experimental results as shown in FIG. 5, it seems that the pixel shift rate needs to be secured about 40 Hz or more, and it is desirable that it is practically 45 Hz or more. Of course, the present invention is not limited to this, and when the pixel shifting element 13 is of a type that can perform pixel shifting at high speed, a higher pixel shifting rate (for example, three times the pixel shifting rate in the pixel shifting mode, 4 times (In order to synchronize the driving timing of the pixel shifting element 13 and the driving timing of the display element 12, basically, the pixel shifting rate is 1 frame). The display rate (that is, an integer multiple of at least twice the pixel shift rate in the pixel shift mode).

  Next, FIG. 7 is a diagram showing a configuration example of a digital camera to which the image display device as shown in FIG. 1 is applied. In FIG. 7, the components corresponding to those in FIG.

  The image display apparatus as shown in FIG. 1 can be widely applied as long as it is an apparatus that displays an image by shifting pixels. Here, a digital camera (digital still camera: DSC) as an application example thereof will be described. To do.

  In the example shown in FIG. 7, an electronic view finder (EVF) display unit using a pixel shifting technique is provided in the digital camera as a pixel shifting enlarged display unit. High-definition image display can be performed as required.

  This digital camera as an imaging device includes an imaging optical unit 21, an imaging element 22, an imaging circuit 23, an A / D converter 24, a focus motor driving circuit 25, a zoom motor driving circuit 26, and an aperture driving circuit. 27, shutter drive circuit 28, image processing circuit 31, compression / decompression unit 33, timing generator 35, display unit 36, display control unit 3, backlight 11, display element 12, and pixel shifting element. 13, eyepiece optical system 20, removable memory 34, built-in memory 32, nonvolatile memory 37, power supply unit 6, operation unit 38, and system controller 39.

  Here, the EVF display unit includes a display control unit 3, a backlight 11, a display element 12, a pixel shifting element 13, and an eyepiece optical system 20.

  The system controller 39 includes a power supply state determination unit 7 and a pixel shift display determination unit 8.

  The imaging optical unit 21 is for imaging a subject image on the imaging element 22 and is configured as an imaging lens configured as a zoom optical system, a diaphragm for controlling the amount of light flux passing through the imaging lens, and imaging A mechanical shutter for controlling a transit time of a light beam passing through the lens, a zoom motor for driving a zoom lens included in the imaging lens, and a focus motor for driving a focus lens included in the imaging lens. It is prepared for.

  The imaging element 22 photoelectrically converts the optical image of the subject imaged by the imaging optical unit 21 and outputs it as an electrical signal. For example, the imaging element 22 is configured as a CCD or a CMOS.

  The image pickup circuit 23 drives the image pickup device 22 and performs analog signal processing on the electric signal obtained from the image pickup device 22 to output it as an analog image signal.

  The A / D converter 24 converts the analog image signal output from the imaging circuit 23 into a digital image signal (video signal) and outputs it.

  The focus motor driving circuit 25 performs focusing of the imaging lens by controlling and driving a focus motor included in the imaging optical unit 21.

  The zoom motor drive circuit 26 performs zooming of the imaging lens by controlling and driving a zoom motor included in the imaging optical unit 21.

  The aperture driving circuit 27 performs aperture adjustment by controlling and driving the aperture included in the imaging optical unit 21.

  The shutter drive circuit 28 adjusts the exposure time (shutter time) of the image pickup device 22 by controlling and driving a mechanical shutter included in the image pickup optical unit 21.

  The image processing circuit 31 is for performing various types of image processing on the image signal output from the A / D converter 24 and temporarily stored in the built-in memory 32 via the bus. The image processing performed by the image processing circuit 31 includes, for example, pixel defect compensation, three-plate processing when the image pickup device 22 is a single plate, color balance processing, and matrix conversion from RGB signals to luminance-color difference signals. Examples include processing, inverse conversion processing, false color removal (or false color reduction) processing by band limitation, various non-linear processing represented by γ conversion, pixel number conversion processing, and the like. The image signal processed by the image processing circuit 31 is stored again in the built-in memory 32 via the bus. The image processing circuit 31 also functions as the preprocessing circuit 1 shown in FIG.

  The compression / decompression unit 33 performs a process of compressing the image signal processed by the image processing circuit 31 or a process of expanding the compressed image signal already recorded in the removable memory 34 and storing it in the built-in memory 32. It is something to go.

  The display unit 36 is for displaying an image processed by the image processing circuit 31, or for displaying various kinds of information related to the digital camera. For example, the display unit 36 is disposed on the back side of the digital camera. The display unit includes an LCD or the like. Here, the digital camera is provided with both a display unit 36 constituted by the rear LCD and the EVF display unit having a pixel shifting function, and these are controlled by the system controller 39. It is like that. That is, for example, the system controller 39 hides the EVF display unit when displaying on the display unit 36, and hides the display unit 36 when displaying on the EVF display unit. The display device is controlled such that the display unit 36 and the EVF display unit are not displayed at the same time.

  The timing generator 35 corresponds to the timing controller 10 shown in FIG. 1, and generates a reference signal (timing signal) used in this digital camera.

  The display control unit 3 controls each circuit of the EVF display unit based on the control of the system controller 39, and includes a pixel shift control unit 4 including the LPF mode control unit 5 as shown in FIG.

  The backlight 11, the display element 12, and the pixel shifting element 13 are as described with reference to FIG.

  The eyepiece optical system 20 projects an image displayed on the display element 12 and emitted through the pixel shifting element 13 in a magnified manner as a virtual image (that is, configured as an enlargement optical system). ).

  The removable memory 34 is a detachable nonvolatile recording medium such as a memory card (for example, an SD card, xD picture card, smart media, etc.) or a small hard disk, and an image (still image or moving image) captured by the image sensor 22. Image) or sound.

  The built-in memory 32 corresponds to the frame memory 2 and the field memory 9 shown in FIG. 1, and is composed of a volatile memory that operates at high speed, such as SDRAM (Synchronous Dynamic Random Access Memory). As described above, it is also used as a work area for image processing.

  The non-volatile memory 37 is configured as a non-volatile recording medium such as a flash memory, in which a basic control program of the digital camera, various data related to the digital camera, and the like are recorded. The system controller 39 reads the basic control program from the nonvolatile memory 37 and executes it to control the entire digital camera.

  The power supply unit 6 stabilizes and supplies power supplied from a battery or an external power supply to each unit in the digital camera. This digital camera is portable and is driven by a battery when it is normally carried, but it can also be operated by supplying power from an external power source by connecting an AC adapter or the like. It has become.

  The operation unit 38 is a power switch for turning on / off the power of the digital camera, a mode changeover switch for setting the operation mode of the digital camera, and the display is performed by the display unit 36 or by the EVF display unit. A display switch for setting the image, a moving image / still image switching switch for setting whether to record a moving image or a still image, and a two-stage button switch for inputting an instruction for an imaging operation A release button, a cross key for performing various selection operations and movement operations, and the like.

  The system controller 39 is for comprehensively controlling the entire digital camera based on the basic control program described above.

  Next, in this digital camera, the outline of the operation when capturing an image is as follows.

  Prior to the actual photographing, focus detection and photometry are performed, and based on the results, focus adjustment of the imaging optical unit 21 is performed, and the exposure time (shutter speed) and aperture value of the imaging are set. .

  Then, when the second release button is pressed, the optical image of the subject formed through the imaging optical unit 21 is converted into an electrical signal by the imaging device 22 for the exposure time, and then the imaging device 22. Is output from the imaging circuit 23 as an analog image signal.

  The analog image signal is converted into a digital image signal by the A / D converter 24 and temporarily stored in the built-in memory 32.

  The image processing circuit 31 performs the above-described image processing on the image information temporarily stored in the built-in memory 32.

  The image information processed by the image processing circuit 31 is subjected to, for example, JPEG compression (in the case of a still image) or MPEG compression (in the case of a moving image) by the compression / decompression unit 33 and is recorded in the removable memory 34.

  The captured image can be displayed on either the display unit 36 or the EVF display unit. Here, when the image is displayed on the display unit 36, image processing is performed by the image processing circuit 31, and image information that has undergone pixel number conversion for the display unit 36 is displayed on the display unit 36. When the image is displayed on the EVF display unit, an image processed by the image processing circuit 31 and temporarily stored in the built-in memory 32 is converted in the number of pixels by the display control unit 3 to be converted into a frame memory and a field. It is stored in the built-in memory 32 that functions as a memory, and is further displayed on the display element 12. At this time, the backlight 11 is driven, and the pixel shifting element 13 is also driven as necessary, and display by the EVF display unit is performed.

  Note that when the composition is confirmed by the display unit 36 or the EVF display unit before capturing a still image, one or both of these are used as a finder and a frame image is displayed. Such a display is called a live view.

  On the other hand, when an image already recorded in the removable memory 34 is displayed, the compressed image information is read from the removable memory 34 and decompressed by the compression / decompression unit 33, and the decompressed image information is stored in the built-in memory 32. Memorize temporarily. Next, the decompressed image information is subjected to predetermined image processing, for example, by the image processing circuit 31, and then the processed image is displayed on the display unit 36 or the EVF display unit in the same manner as when photographing.

  The system controller 39 reads the basic control program of the digital camera from the non-volatile memory 37, and controls the entire digital camera including the processing described above. In addition, the system controller 39 receives an input from the operation unit 38 and performs control according to the input based on the basic control program. Further, the system controller 39 grasps the state of the power supply unit 6 by the power supply state determination unit 7 based on the basic control program, and controls the power supply unit 6 to perform overall power management. The power management performed by the system controller 39 includes a process of switching the pixel shift mode of the EVF display unit as described above based on the resolution and power state of the input video signal. In addition, the system controller 39 performs focus adjustment via the focus motor drive circuit 25, zoom adjustment via the zoom motor drive circuit 26, aperture adjustment via the aperture drive circuit 27, shutter drive via the shutter drive circuit 28, and the like. Also has to do.

  By the way, in recent years, the number of pixels of the image sensor 22 tends to increase, and an image sensor having more than 10 million pixels has been widely used. On the other hand, the number of pixels of the display element 12 is often smaller than the number of pixels of the imaging element 22.

  Furthermore, if pixel data of all the pixels of the image sensor 22 is used when performing live view, the time required for reading from the image sensor 22 and subsequent image processing becomes longer, and the number of processed pixels is large, so that the amount of power consumption is increased. Will increase. The longer time is disadvantageous for live view that requires real-time performance and time resolution, and the increase in power consumption is necessary for digital cameras that are often driven by batteries. It is disadvantageous.

  Therefore, during live view, an image of the number of pixels thinned out from the image sensor 22 is read, so that the display frame rate is particularly increased and the time resolution is improved. At the time of this thinning readout, thinning is performed according to the frame rate (when the frame rate is high, the number of pixels to be read is reduced), so that the amount of signal handled per unit time is kept within a predetermined range, and the image processing circuit 31 To avoid excessive processing load.

  In addition, when the luminance of the subject is low, pixel addition reading may be performed, but also at this time, addition according to the subject is performed (when the subject is dark, the number of pixels to be added is increased (that is, It is conceivable that the number of pixels to be read decreases)).

  Accordingly, in some cases, the number of pixels of the live view image read out by thinning out (or adding pixels) from the image sensor 22 may be equal to or less than the number of pixels of the display element 12. When such an image having the number of pixels equal to or smaller than the number of pixels of the display element 12 is output from the imaging element 22, the pixel shift display determination unit 8 displays the image to the LPF mode control unit 5 in the pixel shift control unit 4. 6 is output by outputting a signal indicating that the display should be performed in the LPF mode as shown in FIG. 6 (that is, in the case of the digital camera shown in FIG. The determination to be performed is not based on the video signal input from the outside, but based on the signal from the image sensor 22).

  In the above description, whether to drive in the pixel shift mode or the LPF mode is determined in accordance with the resolution of the input video signal, the voltage of the power supply unit 6, and the like. In order to reduce the amount of heat generated by the image processing circuit 31 and the pixel shift control unit 4 when the temperature is higher than a predetermined value, the LPF mode is used regardless of the resolution of the input video signal. You may make it drive. Thus, the factors for determining whether to drive in the pixel shifting mode or the LPF mode are not limited to the above, and can be widely adopted.

  In the above description, only the pixel shift mode and the low-pass filter mode are described as the display modes provided in the image display device. However, the display modes further include other display modes and appropriate display modes are selected from these display modes. May be selected. In addition, the pixel shift mode is not limited to one, and a plurality of pixel shift modes may be selected and selected.

  According to the first embodiment, since the pixel shift rate in the LPF mode is higher than that in the pixel shift mode, it is possible to make it difficult to observe the fluctuation of the pixel due to the pixel shift. High-quality display can be performed.

  Further, when driving in the LPF mode, it is not necessary to generate a field image for pixel shifting (that is, for each pixel position for pixel shifting), so that it is possible to reduce power consumption. It is possible to extend the operation time of the device and suppress the heat generation of the device.

Since the drive timing of the pixel shift element 13 and the drive timing of the display element 12 are synchronized, it is possible to perform control for preventing unevenness in pixel density at a specific pixel shift position [Embodiment 2]. ]
8 and 9 show Embodiment 2 of the present invention. FIG. 8 is a block diagram showing the configuration of the image display device. FIG. 9 shows pixel shifting at a rate higher than the pixel shifting rate in the pixel shifting mode. It is a timing chart which shows the display state of the display element in a high quality LPF mode to perform, a reference signal, and a pixel shift state.

  In the second embodiment, parts that are the same as those in the first embodiment are given the same reference numerals and description thereof is omitted, and only differences are mainly described.

  In the first embodiment described above, the pixel shift rate of the pixel shift element 13 is set to an integer multiple of at least twice the rate at which the display element 12 displays one frame (that is, the pixel shift rate in the pixel shift mode). Depending on the type of device used as the element 13, a drive rate that cannot be doubled or more (the upper limit drive rate of the pixel shifting element 13 is larger than 1 times the rate at which the display element 12 displays one frame is 2 Can be less than double). This embodiment is such a pixel shifting element 13 (however, the present embodiment can be applied even to a pixel shifting element 13 capable of realizing a driving rate of twice or more). This makes it possible to perform higher-quality LPF display.

  The image display apparatus of the present embodiment is obtained by adding an LPF mode driving unit 14 to the configuration shown in FIG. Here, the LPF mode control unit 5 is connected to the pixel shifting element 13 via the LPF mode driving unit 14.

  The LPF mode driving unit 14 is for driving the pixel shifting element 13 at a timing independent of the drive timing of the display element 12 and at a rate independent of the rate of the display element 12. Therefore, the LPF mode driving unit 14 may have a function of generating a clock separately from the timing controller 10, for example.

  Next, drive timing in the present embodiment will be described with reference to FIG.

  In the example shown in FIG. 9, the pixel shift rate is set to 1.5 times the frame display rate (that is, the pixel shift rate in the pixel shift mode), and the timing is asynchronous (that is, the pixel shift rate). At the time of high resolution in the mode, the rate for displaying one frame must match the pixel shift rate, and the timing needs to be synchronized. Is possible).

  That is, the field data supplied to the display element 12 in one frame cycle (frequency: 30 Hz) is set to the field data at the same pixel position (for example, the field data at the pixel position A) as in FIG. 6 of the first embodiment described above. However, in this one frame period, the pixel shift is performed for 1.5 periods (that is, A → C → B → D → A → C), and the drive timing of the pixel shift element 13 and the drive timing of the display element 12 are Is asynchronous. Such control is realized by driving the pixel shifting element 13 by the LPF mode driving unit 14 independently of driving of the display element 12 in the LPF mode (however, in the pixel shifting mode, the above-described implementation is performed). Similarly to the first embodiment, the pixel shifting element 13 is driven without going through the LPF mode driving unit 14, and the driving timing of the pixel shifting element 13 is synchronized with the driving timing of the display element 12).

  Even in the case shown in FIG. 9, since the pixel shift rate (rate at which the pixel position makes a round) is 45 Hz, as can be seen with reference to FIG. Can be increased relatively (for example, to 80%). Here, the pixel shifting rate of the pixel shifting element 13 driven by the LPF mode driving unit 14 is, for example, an upper limit driving rate that can be realized by the pixel shifting element 13 (however, the upper limit driving rate). It is not limited, and it is only necessary to secure a pixel shift rate that does not feel a sense of pixel swing (in other words, a pixel shift element 13 whose upper limit drive rate is a rate that does not feel the sense of pixel swing). Is desirable)).

  According to the second embodiment, the same effects as those of the first embodiment described above are obtained, and in the LPF mode, the pixel shift element 13 is driven independently of the drive frequency of the display element 12 and in the pixel shift mode. Since the pixel shifting element 13 is driven at a driving frequency higher than the frequency, the pixel swinging feeling due to the pixel shifting can be reduced, and a high-quality image can be displayed.

  When the pixel shifting element 13 is driven at the upper limit driving frequency that can be realized by the pixel shifting element 13, the feeling of pixel swing due to pixel shifting is reduced as much as possible to display a higher quality image. It can be carried out.

  Note that the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, you may delete a some component from all the components shown by embodiment. Furthermore, the constituent elements over different embodiments may be appropriately combined. Thus, it goes without saying that various modifications and applications are possible without departing from the spirit of the invention.

1 is a block diagram showing a configuration of an image display device in Embodiment 1 of the present invention. 5 is a flowchart showing the operation of the image display device in the first embodiment. 4 is a timing chart showing a display state of a display element, a reference signal, and a pixel shift state in the pixel shift mode in the first embodiment. In the pixel shift mode shown in FIG. 3 of Embodiment 1 above, the display state, reference signal, and pixel shift state of the display element in the LPF mode achieved by making the field data supplied to the display element 12 the same during one frame period The timing chart which shows. The chart which shows the relationship between a display frame rate and the ratio of the person who can tolerate a pixel shake in the said Embodiment 1. FIG. 4 is a timing chart showing a display state, a reference signal, and a pixel shift state of a display element in a high quality LPF mode in which pixel shift is performed at a rate higher than the pixel shift rate in the pixel shift mode in the first embodiment. FIG. 3 is a diagram illustrating a configuration example of a digital camera to which the image display device as illustrated in FIG. 1 of the first embodiment is applied. The block diagram which shows the structure of the image display apparatus in Embodiment 2 of this invention. In the said Embodiment 2, the timing chart which shows the display state of the display element in a high quality LPF mode which performs pixel shifting at a rate higher than the pixel shifting rate of pixel shifting mode, a reference signal, and a pixel shift state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pre-processing circuit 2 ... Frame memory 3 ... Display control part 4 ... Pixel shift control part 5 ... LPF mode control part 6 ... Power supply part 7 ... Power supply state judgment part 8 ... Pixel shift display judgment part 9 ... Field memory 10 ... Timing Controller 11 ... Backlight 12 ... Display element 13 ... Pixel shifting element 14 ... LPF mode drive unit 20 ... Eyepiece optical system 21 ... Imaging optical unit 22 ... Imaging element 23 ... Imaging circuit 24 ... A / D converter 25 ... Focus motor drive Circuit 26 ... Zoom motor drive circuit 27 ... Aperture drive circuit 28 ... Shutter drive circuit 31 ... Image processing circuit 32 ... Built-in memory 33 ... Compression / decompression unit 34 ... Detachable memory 35 ... Timing generator 36 ... Display unit 37 ... Non-volatile memory 38 ... Operation unit 39 ... System controller

Claims (6)

A display element, a pixel shift element that shifts the spatial position of an image displayed on the display element periodically at a predetermined pixel shift frequency, and a pixel shift element that is displayed on the display element and passes through the pixel shift element An enlarged optical system for enlarging an image, and a pixel-shift enlarged display unit including:
In synchronization with the timing at which the pixel shifting element performs pixel shifting, the image displayed on the display element is set to a different image corresponding to a different spatial position, so that the number of pixels is a multiple of the number of pixels included in the display element. A plurality of display modes including a pixel shift mode for performing high-definition display and a low-pass filter mode in which an image displayed on the display element is the same image in a period of one cycle or more in which the pixel shift element performs pixel shift A display control unit for controlling the pixel-shifted enlarged display unit by any one of
With
The display control unit controls the pixel shift enlargement display unit so that a pixel shift frequency in the low-pass filter mode is higher than a pixel shift frequency in the pixel shift mode. Image display device.   The display control unit is configured so that the pixel shift frequency in the low-pass filter mode is an integer multiple of twice or more the pixel shift frequency in the pixel shift mode, and the timing at which the pixel shift element performs pixel shift is The image display apparatus according to claim 1, wherein the pixel shift and enlargement display unit is controlled so as to synchronize with a timing at which the display element displays an image.   Regardless of whether the timing at which the pixel shifting element performs pixel shifting is synchronized with the timing at which the display element displays an image, the display control unit sets the pixel shifting frequency in the low-pass filter mode to the pixel shifting element. The image display apparatus according to claim 1, wherein the frequency is set to an upper limit frequency achievable by the operation.   The said display control part controls the said pixel shift enlarged display part so that the pixel shift frequency in the said low-pass filter mode may be 40 Hz or more, The any one of Claims 1-3 characterized by the above-mentioned. The image display device according to item. The resolution of the video signal is compared with the resolution of the display element. When the resolution of the video signal is less than or equal to the resolution of the display element, it is determined that the low-pass filter mode should be set. A pixel shift display determination unit for performing determination that the pixel shift mode should be set when the resolution of the display element is higher,
5. The display control unit according to claim 1, wherein the display control unit sets a display mode based on a determination result of the pixel shift display determination unit and controls the pixel shift enlarged display unit. The image display device according to claim 1. A power supply unit capable of using an external power supply and a battery as a power supply;
A power supply state determination unit that determines whether the power supply unit uses an external power supply or a battery, and further determines whether or not the remaining amount of the battery is a predetermined amount or more when it is determined that the battery is the power supply When,
Further comprising
When the determination result by the power supply state determination unit is that the battery is a power source and the remaining amount of the battery is less than a predetermined amount, the pixel shift display determination unit has a video signal resolution of the display element The image display device according to claim 5, wherein the determination is made that the low-pass filter mode should be set even when the resolution is higher than the resolution of the image display device.

Images