JP6693140B2 - Display device and display device control method - Google Patents

Description

  The present invention relates to a display device and a display device control method.

  BACKGROUND ART Conventionally, a display device having a solid-state light source such as a laser diode (LD) or a light emitting diode (LED) is known. This type of display device normally uses PWM (Pulse Width Modulation) control as a method for controlling the brightness of a light source (see, for example, Patent Document 1).

JP, 2005-129783, A

The solid-state light source may deteriorate in emission brightness with respect to electric power supplied to the light source due to deterioration over time. In such a case, in order to prevent the display quality from deteriorating, the state in which the luminance of the light source is lowered is examined in detail, the parameters of the PWM control are changed, and the light source is made to emit light at the original luminance. Therefore, there has been a demand for a method that can more easily suppress the deterioration of display quality.
The present invention has been made in view of the above circumstances, and a display device capable of suppressing the deterioration of display quality by a simple operation in response to a change in the brightness of the light source with respect to the power supplied to the light source, and a display device. It aims at providing the control method of.

In order to achieve the above object, the present invention is a display device for displaying an image by light emitted from a light source, wherein a light source drive unit that outputs a drive current to the light source, and a duty of the drive current that the light source drive unit outputs. Ratio, a storage unit that stores control information that associates the brightness ratio with respect to the maximum brightness of the light source, based on the control information, a control unit that sets the duty ratio of the drive current output by the light source drive unit, A detection unit configured to detect the brightness of the light source, wherein the control unit detects a detection result of the detection unit when the light source drive unit outputs a drive current having a first duty ratio; and the light source drive unit. Corrects the control information based on the detection result of the detection unit when the drive current of the second duty ratio lower than the first duty ratio is output.
With this configuration, the brightness of the light source can be controlled based on the control information that associates the duty ratio of the drive current supplied to the light source with the brightness ratio of the light source, and this control information can be corrected by a simple operation. Accordingly, it is possible to suppress the deterioration of the display quality in response to the change in the brightness of the light source with respect to the power supplied to the light source.

Further, in the display device according to the present invention, the control unit controls the brightness of the light source with respect to the duty ratio of the drive current output by the light source drive unit due to the rounding of the waveform of the drive current output by the light source drive unit. The control information is corrected so as to compensate for the decrease in the ratio.
According to this configuration, the brightness of the light source can be appropriately controlled even in the case where the duty ratio is substantially reduced due to the waveform rounding of the drive current.

Further, in the display device according to the present invention, the control information includes information indicating a correlation curve between a duty ratio of a drive current output by the light source drive unit and a brightness ratio of the light source, and the control unit is The control information is corrected by shifting a correlation curve included in the control information.
With this configuration, the control information can be corrected by a simple operation.

Further, in the display device according to the present invention, the first duty ratio is a value associated with the maximum brightness of the light source by the control information.
According to this configuration, the control information can be appropriately corrected based on the few measurement results.

Further, the present invention is characterized in that, in the display device, the drive current output to the light source by the light source drive section has a frequency equal to or higher than an audible frequency band.
According to this configuration, when the frequency of the drive current supplied to the light source is high and the drive current is easily affected by the waveform rounding, the brightness of the light source can be appropriately controlled by correcting the control information.

The present invention is also characterized in that, in the display device, the light source drive section outputs a drive current including a plurality of types of pulses having different widths.
With this configuration, it is possible to increase the pulse interval without changing the duty ratio of the drive current, and it is possible to suppress the influence of the current waveform rounding.

Further, in order to achieve the above object, the present invention is a method for controlling a display device, comprising a light source, and a light source drive section for outputting a drive current to the light source, wherein an image is displayed by the light emitted from the light source, Based on control information associating the duty ratio of the drive current output by the light source drive unit and the brightness ratio with respect to the maximum brightness of the light source, setting the duty ratio of the drive current output by the light source drive unit, A step of detecting the brightness of the light source; a detection result of the brightness of the light source when the light source drive section outputs a drive current having a first duty ratio; and the light source drive section having the first duty ratio. And a step of correcting the control information based on a detection result of the brightness of the light source when a driving current having a second duty ratio lower than that of the light source is output. And it features.
With this configuration, the brightness of the light source can be controlled based on the control information that associates the duty ratio of the drive current supplied to the light source with the brightness ratio of the light source, and this control information can be corrected by a simple operation. Accordingly, it is possible to suppress the deterioration of the display quality in response to the change in the brightness of the light source with respect to the power supplied to the light source.

  The present invention can be implemented in various forms other than the display device and the display device control method described above. For example, it is also possible to realize the control method described above as a program to be executed by a computer. Further, for example, it can be realized in the form of a recording medium recording the above program, a server device distributing the program, a transmission medium transmitting the program, a data signal embodying the program in a carrier wave, and the like.

The figure which shows the structure of a projector. Explanatory drawing of the drive current waveform of a light source part. Explanatory drawing of light source control information. Explanatory drawing of the drive current waveform of a light source part. The flowchart which shows operation | movement of a control part. Explanatory drawing which shows the example of the drive current waveform of a light source part. Explanatory drawing of light source control information.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of a projector 100 according to an embodiment to which the invention is applied.
The projector 100 (display device) is a device that is connected to an external image supply device 200 such as a personal computer or various video players, and projects an image based on an image signal supplied from the image supply device 200 onto a projection target.
As the image supply device 200, a video reproducing device, a DVD (Digital Versatile Disk) reproducing device, a television tuner device, a CATV (Cable television) set top box, a video output device such as a video game device, a personal computer, or the like can be used. it can.
Further, the projection target may be an object that is not uniformly flat such as a building or an object, or may have a screen SC or a flat projection surface such as a wall surface of the building. FIG. 1 shows a flat screen SC as a projection target.

The projector 100 includes an image input interface unit (hereinafter abbreviated as an image input I / F unit) 151. The image input I / F unit 151 functions as an input unit.
The image input I / F unit 151 includes a connector for connecting a cable and an interface circuit (both not shown), and inputs an image signal supplied from the image supply device 200 connected via the cable. The image input I / F unit 151 converts the input image signal into image data and outputs the image data to the image processing unit 153.
The interface provided in the image input I / F unit 151 may be an interface for data communication such as Ethernet (registered trademark), IEEE 1394, or USB. Further, the interface of the image input I / F unit 151 may be an interface for image data such as MHL (registered trademark), HDMI (registered trademark), and DisplayPort.
Further, the image input I / F unit 151 may be configured to include, as a connector, a VGA terminal to which an analog video signal is input and a DVI (Digital Visual Interface) terminal to which digital video data is input. Furthermore, the image input I / F unit 151 includes an A / D conversion circuit, and when an analog video signal is input through the VGA terminal, the A / D conversion circuit converts the analog video signal into image data, It is output to the processing unit 153.

  The projector 100 includes a display unit 110 that forms an optical image and projects the image on the screen SC (projection surface). The display unit 110 includes a light source unit 111, a color separation unit 112, a light modulator 113, and a projection optical system 114. The light source unit 111 corresponds to the "light source" of the present invention. The projector 100 corresponds to a display device that displays an image by projecting the image on the screen SC. The projection unit 110 can be referred to as a display unit that displays an image.

  The light source unit 111 includes a solid-state light source. As the solid-state light source, a light source using a light emitting element such as an LED (Light Emitting Diode) or a semiconductor laser element can be used. As the semiconductor laser element, an element configured by a single semiconductor laser element or an element including a plurality of semiconductor laser elements arranged in a plane can be used. The light source unit 111 of this embodiment includes a laser diode (LD) as a solid-state light source. The LD of this embodiment emits blue light (emitted light). Hereinafter, the solid-state light source included in the light source unit 111 will be simply referred to as a light source.

  The blue light emitted from the LD of the light source unit 111 is guided to the color separation unit 112. The color separation unit 112 includes a phosphor wheel (not shown) having a phosphor, and blue light emitted from the LD is converted into yellow light (fluorescence) including red light and green light by the phosphor wheel. The color separation unit 112 includes a dichroic mirror (not shown). The yellow light converted by the phosphor wheel is separated into red light and green light by the dichroic mirror. Further, the color separation unit 112 allows blue light emitted from the LD of the light source unit 111 to pass through the phosphor wheel. As a result, the color separation unit 112 outputs three color lights of red (R), green (G), and blue (B) based on the blue light emitted by the LD of the light source unit 111.

  The color separation unit 112 uses a reflection mirror, a relay lens, a condenser lens, a microlens array, and the like to convert the three color lights of red (R), green (G), and blue (B) into parallel light to the light modulator 113. Lead.

Here, the light source unit 111 may include a plurality of LDs, for example, a first LD that emits blue light that passes through the phosphor wheel and a first LD that emits blue light that is converted into yellow light by the phosphor wheel. 2 LDs may be provided.
Further, the light source unit 111 may be configured to include three light sources corresponding to each color of red, green and blue. Specifically, it may be configured to include a light source that emits red light, a light source that emits green light, and a light source that emits blue light. In this case, the color separation unit 112 guides the three color lights emitted from the light source unit 111 to the light modulator 113.
Further, the light source unit 111 may be configured to include an optical scanning element that scans the light emitted from the light source, and a lens group that enhances the optical characteristics of the emitted light.

  The light source unit 111 is driven by the light source driving unit 121. Further, the PWM signal generation unit 122 is connected to the light source drive unit 121. The light source drive unit 121 and the PWM signal generation unit 122 are connected to the internal bus and are controlled by the control unit 170.

Information specifying the duty ratio of the PWM signal, that is, the ratio of the ON time to the sum of the ON time and the OFF time of the pulse is input from the control unit 170 to the PWM signal generating unit 122. The PWM signal generation unit 122 generates a PWM signal having a duty ratio designated by the information input from the setting unit 330, and outputs the PWM signal to the light source drive unit 121.
The light source drive unit 121 generates a drive current to be output to the light source unit 111 according to the PWM signal input from the PWM signal generation unit 122, and supplies the drive current to the light source unit 111. The drive current output from the light source drive unit 121 is a pulse current synchronized with the rising and falling edges of the PWM signal input from the PWM signal generation unit 122. Therefore, the pulse width and frequency of the drive current output by the light source drive unit 121 are controlled by the PWM signal. Further, information designating the current value of the drive current is input to the light source drive unit 121 from the control unit 170, and the light source drive unit 121 determines the current value of the drive current according to the input information. As a result, the control unit 170 controls the amount of light output from the light source of the light source unit 111 (hereinafter referred to as the output light amount). In other words, the control unit 170 controls the brightness of the light source of the light source unit 111.

  The light modulator 113 includes a liquid crystal panel 115. The liquid crystal panel 115 is composed of, for example, three transmissive liquid crystal panels corresponding to the three primary colors of R, G, and B, or three reflective liquid crystal panels. The R, G, and B color lights separated by the color separation unit 112 enter the liquid crystal panel corresponding to the respective color lights and are modulated. Accordingly, the light modulator 113 modulates the color light separated by the color separation unit 112 to generate image light. The image lights modulated by the light modulator 113 are combined by a cross dichroic prism (not shown) and emitted to the projection optical system 114.

  The light modulator drive unit 123 is connected to the light modulator 113. The optical modulator driving unit 123 is connected to the internal bus 180 and controlled by the control unit 170. Under the control of the control unit 170, the light modulation device driving unit 123 generates an image signal for each of R, G, and B colors based on the display image signal output by the image processing unit 153. The light modulation device drive unit 123 draws an image on the three liquid crystal panels forming the liquid crystal panel 115 based on the generated R, G, and B image signals.

  The projection optical system 114 includes a lens group that projects the image light modulated by the light modulator 113 onto the screen SC and forms an image on the screen SC. Further, the projection optical system 114 may include a zoom mechanism for enlarging / reducing the projected image on the screen SC and adjusting the focus, and a focus adjusting mechanism for adjusting the focus.

The projector 100 includes an optical sensor 117. The optical sensor 117 is a feature that corresponds to the "detection unit" according to this invention. The optical sensor 117 detects the brightness or the amount of light emitted by the light source unit 111. The light sensor 117 may have a configuration capable of indirectly or directly detecting the light emitted by the light source unit 111. In the present embodiment, as an example, each color light incident on the liquid crystal panel 115 from the color separation unit 112 is detected. Detect the amount of light. In this example, the optical sensor 117 can be configured to include a red light sensor that detects red light, a blue light sensor that detects blue light, and a green light sensor that detects green light. As will be described later, the optical sensor 117 obtains a detection value as an index for determining the degree of decrease in the light amount when the light amount of the light emitted from the light source of the light source unit 111 decreases due to deterioration over time or the influence of the environment. I wish I could. Therefore, it is not necessary to detect the light amounts of all the color lights, and for example, only the blue light sensor that detects blue light may be provided. The green light sensor may be omitted because the amount of green light has little effect on the brightness of the projected image on the screen SC. Further, the optical sensor 117 may be provided in the optical path between the light source unit 111 and the color separation unit 112, or may be provided in the light source unit 111. Further, when the light source unit 111 includes a plurality of LDs, an optical sensor 117 may be provided corresponding to each LD, or an optical sensor 117 that detects the light amount of any one of the LDs may be provided.
As the optical sensor 117, various types of sensors, which are so-called optical sensors, such as a photodiode, an illuminance sensor, a color sensor for each color of R, G, and B can be used.

The projector 100 includes an operation panel 141 and an input processing unit 143. The input processing unit 143 is connected to the internal bus 180.
On the operation panel 141 functioning as a user interface, various operation keys and a display screen composed of a liquid crystal panel are displayed. When the operation key displayed on the operation panel 141 is operated, the input processing unit 143 outputs the data corresponding to the operated key to the control unit 170. Further, the input processing unit 143 causes the operation panel 141 to display various screens under the control of the control unit 170.
In addition, a touch sensor that detects a contact with the operation panel 141 is integrally formed on the operation panel 141 by overlapping. The input processing unit 143 detects, as an input position, the position of the operation panel 141 with which the user's finger or the like comes into contact, and outputs data corresponding to the detected input position to the control unit 170.

The projector 100 also includes a remote control light receiving unit 142 that receives an infrared signal transmitted from the remote control 5 used by the user. The remote controller light receiving unit 142 is connected to the input processing unit 143. The remote controller 5, the remote controller light receiving unit 142, and the operation panel 141 can each be referred to as a receiving unit that receives a user operation.
The remote control light receiving section 142 receives the infrared signal transmitted from the remote control 5. The input processing unit 143 decodes the infrared signal received by the remote control light receiving unit 142, generates data indicating the operation content of the remote control 5, and outputs the data to the control unit 170.

  The projector 100 includes a wireless communication unit 145. The wireless communication unit 145 is connected to the internal bus 180. The wireless communication unit 145 includes an antenna, an RF (Radio Frequency) circuit, and the like (not shown), and executes wireless communication with an external device under the control of the control unit 170. The wireless communication system of the wireless communication unit 145 is, for example, a short-range wireless communication system such as a wireless LAN (Local Area Network), Bluetooth (registered trademark), UWB (Ultra Wide Band), infrared communication, or wireless using a mobile phone line. A communication method can be adopted.

  The projector 100 includes an image processing system. The image processing system is mainly configured by a control unit 170 that integrally controls the entire projector 100, and further includes an image processing unit 153, a frame memory 155, and a storage unit 160. The control unit 170, the image processing unit 153, and the storage unit 160 are connected to the internal bus 180.

  The image processing unit 153 expands the image data input from the image input I / F unit 151 in the frame memory 155 according to the control of the control unit 170, and executes the image processing on the expanded image data. The image processing executed by the image processing unit 153 includes, for example, resolution conversion (scaling) processing, frame rate conversion processing, shape correction processing, zoom processing, color tone correction processing, brightness correction processing, and the like. Of course, it is also possible to combine and execute a plurality of processes.

The resolution conversion process is a process in which the image processing unit 153 converts the resolution of the image data according to the resolution designated by the control unit 170, for example, the display resolution of the liquid crystal panel of the light modulator 113.
The frame rate conversion process is a process in which the image processing unit 153 converts the frame rate of image data into a frame rate designated by the control unit 170.
The shape correction processing is processing in which the image processing unit 153 converts the image data according to the correction parameter input from the control unit 170 and corrects the shape of the image projected on the screen SC.
The zoom process is a process in which the image processing unit 153 enlarges / reduces an image when zooming is instructed by an operation of the remote controller 5 or the operation panel 141.
The color tone correction process is a process of converting the color tone of the image data, and the image processing unit 153 changes the data of each pixel included in the image data according to the color tone designated by the control unit 170. In this process, the projector 100 can realize a color tone suitable for watching a movie, a color tone suitable when the screen SC is installed in a bright environment, a color tone suitable for projecting on a non-white screen SC such as a blackboard. .. In addition to the color tone correction processing, contrast adjustment or the like may be performed.
The brightness correction process is a process in which the image processing unit 153 corrects the brightness of the image data. By the brightness correction processing, the brightness of the image data is corrected to the brightness corresponding to the light emitting state of the light source unit 111, the brightness of the environment in which the projector 100 is installed, and the like.
The control unit 170 controls the content of the above-described processing executed by the image processing unit 153, parameters, and the start and end timings of the processing.
The image processing unit 153 reads the processed image data from the frame memory 155 and outputs it as a display image signal to the light modulator driving unit 123.

  The storage unit 160 is composed of a non-volatile memory such as a flash memory or an EEPROM. The storage unit 160 stores data processed by the control unit 170 and a control program executed by the control unit 170 in a non-volatile manner. The storage unit 160 also stores set values of various processes executed by the image processing unit 153, various data referenced by the control unit 170, and sensor values measured by the optical sensor 117.

  The control unit 170 includes hardware such as a CPU, a ROM, and a RAM (all not shown). The ROM is a non-volatile storage device such as a flash ROM and stores a control program and data. The RAM constitutes the work area of the CPU. The CPU expands the control program read from the ROM or the storage unit 160 into the RAM and executes the control program expanded into the RAM to control each unit of the projector 100.

  The control unit 170 also includes a projection control unit 171, a light source control unit 172, and a correction control unit 173 as functional blocks. These functional blocks are realized by the CPU executing a control program stored in the ROM or the storage unit 160.

The projection control unit 171 adjusts the display mode of the image on the display unit 110 and executes the projection of the image on the screen SC.
Specifically, the projection control unit 171 controls the image processing unit 153 to perform image processing on the image data input from the image input I / F unit 151. At this time, the projection control unit 171 may read the parameters required for the processing by the image processing unit 153 from the storage unit 160 and output them to the image processing unit 153.

  The light source control unit 172 controls the light source driving unit 121 and the PWM signal generating unit 122 to turn on the light source of the light source unit 111 and adjust the light amount of the light source.

  The image processing unit 153 calculates the average luminance of one frame of the image data based on the image data input to the image input I / F unit 151. The image processing unit 153 outputs the calculated average luminance of one frame to the control unit 170 as brightness information. The light source control unit 172 generates a drive parameter, which is information that specifies the output light amount set for the light source, based on the brightness information input from the image processing unit 153. This drive parameter is information indicating the amount of output light set for the light source, and is, for example, data indicating the brightness ratio of the light source. Here, the brightness ratio of the light source is a value indicated by a ratio (for example, 70%) to the maximum light amount when the maximum light amount that the light source can output is 100%. For example, when the output light amount set for the light source is set to 70% of the maximum light amount that the light source can output, the brightness ratio of the light source is “70%”.

  The light source control unit 172 refers to the light source control information 161 (control information stored in the storage unit 160. The light source control information 161 indicates the brightness ratio of the light source and the drive current output from the light source drive unit 121 to the light source unit 111. The light source control information 161 may include information associating the duty ratio with the light source control information 161. For example, the light source control information 161 may include an arithmetic expression or a function that calculates the duty ratio corresponding to the brightness ratio of the light source. It may include a table that associates the brightness ratio of the light source with the duty ratio, or the data of the correlation curve between the brightness ratio of the light source and the duty ratio.

  Further, the light source control unit 172 generates information that specifies the current value of the drive current output by the light source driving unit 121, based on the light source control information 161. The light source control information 161 includes information that associates the brightness ratio of the light source with the current value of the drive current output from the light source driving unit 121 to the light source unit 111. For example, it may include an arithmetic expression or a function that calculates a current value corresponding to the brightness ratio of the light source based on the brightness ratio. Further, the light source control information 161 may include a table in which the brightness ratio of the light source and the current value are associated with each other, and the data of the correlation curve between the brightness ratio of the light source and the current value.

  The light source control unit 172 generates, calculates, or acquires the duty ratio of the PWM signal corresponding to the drive parameter based on the light source control information 161. The light source controller 172 outputs information indicating the duty ratio to the PWM signal generator 122. Further, the light source control unit 172 outputs information indicating the current value of the drive current to the light source driving unit 121 based on the light source control information 161.

  The PWM signal generator 122 generates a PWM signal based on the information input from the light source controller 172, and outputs the PWM signal to the light source driver 121. Then, the light source driving unit 121 supplies the light source unit 111 with a drive current having a current value specified by the information input from the light source control unit 172, according to the PWM signal input from the PWM signal generation unit 122.

  The correction control unit 173 corrects the light source control information 161 stored in the storage unit 160 based on the detection value of the optical sensor 117. The solid-state light source included in the light source unit 111 changes over time due to the characteristics of the solid-state light source and the influence of the environment, and the maximum brightness of the solid-state light source gradually decreases from the maximum brightness at the start of use. This change with time is clear both when the solid-state light source is an LD and when the solid-state light source is an LED. The change with time of the solid-state light source changes the correspondence between the duty ratio of the drive current of the light source unit 111 and the brightness ratio of the light source. In the projector 100, the correction control unit 173 can correct the light source control information 161 in accordance with the state of the solid-state light source after the time-dependent change when the solid-state light source changes with time.

The corresponding change between the duty ratio of the drive current and the brightness ratio of the light source is affected by the change in the light emission threshold current of the solid-state light source.
FIG. 2 is an explanatory diagram of a drive current waveform of the light source unit 111. The vertical axis represents current and the horizontal axis represents the passage of time. Note that the waveform of the drive current shown in FIG. 2 is deformed so that the blunt portion is emphasized so that the influence of the bluntness of the waveform can be clearly understood, and the waveform of the drive current actually output from the light source drive unit 121 is shown. Does not necessarily match.

  The PWM signal output from the PWM signal generation unit 122 to the light source drive unit 121 is a rectangular wave, and the light source drive unit 121 generates a rectangular wave drive current and outputs the drive current to the light source unit 111. However, in reality, a so-called dullness occurs in the drive current waveform output by the light source drive unit 121 due to the characteristics of the circuit elements that configure the light source drive unit 121.

In the current waveform shown in FIG. 2, dullness occurs at the rising and falling timings of the current.
The emission threshold current of the solid-state light source increases due to the above-described change with time. Here, the light emission threshold current when the usage time of the projector 100 (total usage time from factory shipment) is short (at time A) is indicated by Th1 in the figure, and when the usage time is longer than time A ( The emission threshold current at time B) is indicated by Th2. The light emission threshold current Th2 has a value higher than the light emission threshold current Th1.

If the drive current is an ideal rectangular wave, the time during which the drive current exceeds the light emission threshold current is equal to the ON time of the pulse of the drive current. However, in reality, due to the dull rising of the drive current waveform, the time during which the drive current exceeds the light emission threshold current is shorter than the pulse width of the PWM signal. At time A, the drive current becomes equal to or higher than the light emission threshold current Th1 in the section PW1 shown in the figure. On the other hand, at time B when the change over time has progressed, since the light emission threshold current Th2 is high, the drive current is equal to or higher than the light emission threshold current Th2 in the section PW2, and the section PW2 is shorter than the section PW1. That is, if the drive current output by the light source drive unit 121 does not change, the time at which the solid-state light source emits light at time B is shorter than that at time A.
The magnitude of the dullness and the length of the delay time in which the rise of the drive current is delayed due to the dullness are affected by the circuit characteristics of the PWM signal generation unit 122. Further, the delay time until the drive current rises to the peak tends to be longer as the current value of the drive current is larger.

  Furthermore, the influence of the dullness of the waveform of the drive current becomes more remarkable as the frequency of the drive current increases. The higher the frequency of the drive current, the smaller the pulse width, but the dull rise of the drive current is not so affected by the frequency. For this reason, the delay time in which the rising timing of the drive current is delayed due to the dullness becomes relatively large with respect to the pulse width.

  When the frequency of the PWM signal output from the PWM signal generation unit 122 to the light source drive unit 121 is a frequency included in the human audible frequency band, noise may be pointed out. This is because, at the frequency of the PWM signal, circuit elements or the like generate vibrations around the circuits forming the light source unit 111, the light source driving unit 121, and the PWM signal generating unit 122, and around the signal lines connecting these. .. These vibrations may be heard by the human ear as noise. As a measure against this, in the projector 100, the frequency of the drive current may be set to a frequency higher than the human audible frequency band. Since the human audible frequency band is set to 20 Hz to 20 kHz, for example, the frequency of the PWM signal may exceed 20 kHz, for example, 25 kHz or more, or 30 kHz or more.

As described above, if the frequency of the PWM signal is set to a high frequency for noise suppression, the frequency of the drive current output by the light source drive unit 121 becomes high, and as a result, the waveform of the drive current is easily affected by the dullness.
In the projector 100, the correction control unit 173 uses the optical sensor 117 to find the correspondence between the duty ratio of the drive current and the brightness ratio of the light source unit 111, and corrects the light source control information 161 to make the light source unit 111. The brightness ratio of the light emission of can be controlled appropriately. As a result, even if the solid-state light source of the light source unit 111 changes over time, the brightness ratio of the light source of the light source unit 111 is appropriately adjusted according to the image data input to the image input I / F unit 151, and High quality images can be projected even if changes occur.

  FIG. 3 is an explanatory diagram of the light source control information 161. FIG. 3 shows the correlation between the duty ratio of the drive current and the brightness ratio of the light source, which is included in the light source control information 161. Specifically, the light source control information 161 includes data indicating the correlation shown in FIG. 3, an arithmetic expression or a function for obtaining the duty ratio from the brightness ratio according to the correlation shown in FIG. 3, or a table.

  The horizontal axis of FIG. 3 represents the brightness ratio of the light source. The brightness ratio is a value indicating the brightness ratio in percentage when the maximum brightness of the light source is 100% as described above. The vertical axis represents the duty ratio (duty value) of the drive current. The duty ratio of the drive current is set in the PWM signal generation unit 122 by the correction control unit 173, and the duty ratio of the PWM signal output by the PWM signal generation unit 122 is reflected in the drive current. Therefore, the vertical axis in FIG. 3 can be said to be the duty ratio of the PWM signal output by the PWM signal generation unit 122.

In FIG. 3, (a) shows the correlation of the drive current-brightness ratio contained in the light source control information 161 before correction, and (b) shows the correlation contained in the light source control information 161 after correction.
As shown in (a), the drive current-brightness ratio correlation indicated by the light source control information 161 is substantially linear in the section S1 in the low brightness ratio region (less than 80% in the example of FIG. 3). The drive current-brightness ratio correlation in the section S1 can be expressed by a polynomial (for example, ax + b, where a and b are constants), or can be approximated. The drive current-brightness ratio correlation in the section S1 is calculated, for example, at the time of inspection and setting of the projector 100 at the time of factory shipment, and is stored in the storage unit 160 as the light source control information 161.

  In the section S11 of the region where the duty ratio is close to 100% (in the example of FIG. 3, the duty ratio is 90% or more), the brightness ratio is a value that can be regarded as 100% or almost 100%. This is due to the dullness of the drive current waveform.

FIG. 4 is an explanatory diagram of a drive current waveform of the light source unit 111. The vertical axis represents current and the horizontal axis represents the passage of time. In the figure, (a) shows the waveform of the PWM signal as an ideal rectangular wave, and (b) shows the waveform of the drive current output by the light source drive section 121.
When the duty ratio is high, the ON time P01 of the pulse shown by the rectangular wave in (a) is long and the OFF time PF1 is short. Here, when the off time PF1 is short, it takes time for the drive current to fall due to the blunting of the waveform, and a phenomenon occurs in which it overlaps with the next rise. That is, as shown in (b), the driving current is not sufficiently reduced in the off time PF1 due to the occurrence of the dullness D1. As a result, even when the duty ratio is not 100% and the off time PF1 is present, the same state as when the duty ratio is 100% is obtained. In this case, the light source of the light source unit 111 emits light in the same manner as when a drive current having a duty ratio of 100% is input.
Further, a section S21 between the section S1 and the section S11 is determined so as to connect the section S1 and the section S11. For example, it can be determined as a straight line connecting the upper end Q1 of the section S1 and the lower end Q2 of the section S11.

  The correction control unit 173 causes the light source drive unit 121 to output a plurality of drive currents having different duty ratios, and corrects the light source control information 161 based on the detection value of the optical sensor 117 in that case.

  The correction control unit 173 outputs at least two drive currents from the light source drive unit 121 to acquire the detection value of the optical sensor 117. Specifically, (I) an operation of causing the light source drive unit 121 to output a drive current having a duty ratio that can be regarded as 100% or equivalent, and (II) a drive current having a duty ratio exhibiting a correlation represented by a polynomial expression. Perform output operation. In the operation (I), the brightness of the light source of the light source unit 111 may be the maximum brightness. Therefore, the duty ratio may be 100%. Further, the duty ratio does not have to be 100% as long as it belongs to the section S11. In the operation of (II), it suffices to set the duty ratio included in the section S1 represented by a polynomial in the correlation of the drive current before correction and the brightness ratio. In the example of FIG. 3 shown in the present embodiment, the duty ratio is set to 100% by the operation (I), and the duty ratio is set to 50% by the operation (II). The duty ratio set by the operation (I) corresponds to the first duty ratio, and the duty ratio set by the operation (II) corresponds to the second duty ratio.

FIG. 5 is a flowchart showing the operation of the control unit 170, and particularly shows the operation related to the correction of the light source control information 161 by the correction control unit 173.
The correction control unit 173 starts the operation (I) and sets the duty ratio to 100% or the same (step S11). The correction control unit 173 causes the light source driving unit 121 to output the drive current having the set duty ratio to cause the light source of the light source unit 111 to emit light (step ST12), and acquires the detection value of the optical sensor 117 (step ST13). In step ST13, the detection value detected by the optical sensor 117 is set as the detection value Bmax of the maximum brightness of the light source of the light source unit 111.

  The correction control unit 173 executes the operation (II) and sets the duty ratio included in the polynomial section (polynomial region) (step ST14). The correction control unit 173 causes the light source drive unit 121 to output the drive current having the set duty ratio to cause the light source of the light source unit 111 to emit light (step ST15), and acquires the detection value of the optical sensor 117 (step ST16). In step ST15, the detection value detected by the optical sensor 117 is set as the detection value Bmid.

  The correction control unit 173 calculates the brightness ratio of the light source of the light source unit 111 corresponding to the duty ratio set in step ST14 (step ST17). In step ST17, the detected value Bmax of the maximum brightness of the light source and the detected value Bmid corresponding to the duty ratio of the polynomial section are used to calculate Bmid / Bmax (%) to calculate the brightness ratio. In the example of FIG. 3, Bmid / Bmax (%) = 30 (%).

  The correction control unit 173 performs a process of shifting the polynomial section S1 of the drive current-brightness ratio correlation (a) before correction (step ST18). Specifically, the correction control unit 173 plots the calculated brightness ratio at the position corresponding to the duty ratio set in step ST14. In the example of FIG. 3, it corresponds to a point Q5 corresponding to a duty ratio of 50% and a brightness ratio of 30%. The correction control unit 173 translates the polynomial section S1 of the pre-correction drive current-brightness ratio correlation (a) so as to pass through the point Q5. In the figure, the point Q4 in the drive current-brightness ratio correlation (a) before correction appears to have moved in parallel to the point Q5 corresponding to the same duty ratio as the point Q4, but the direction of parallel movement is the vertical axis direction. Or in the horizontal axis direction. Thereby, the polynomial section S2 of the correlation (b) of the drive current-brightness ratio is obtained. The upper end Q3 of the corrected polynomial section S2 is a point having the same duty ratio as the upper end Q1 of the uncorrected polynomial section S1. Further, the section S11 in which the light source of the light source unit 111 has the maximum brightness can be regarded as not changing even after the correction. The reason why the light source has the maximum luminance in the section S11 is that the waveform of the drive current is blunted as described above, and this phenomenon also occurs after the light source changes with time.

The correction control unit 173 determines the correlation of the section S22 so as to connect the upper end Q3 of the polynomial section S2 and the lower end Q2 of the section S11 (step ST19).
As a result, the corrected drive current-brightness ratio correlation is obtained, so the correction control unit 173 updates the light source control information 161 based on the corrected correlation (step ST20), and ends this processing.

  Note that FIG. 3 illustrates the drive current-brightness ratio correlations (a) and (b), and is not a diagram illustrating the detection value detected by the optical sensor 117 and the brightness itself of the light source of the light source unit 111. .. When the light source of the light source unit 111 changes with time, the brightness itself of the light source decreases, so that the brightness does not match before and after the correction, but the horizontal axis in FIG. 3 indicates the brightness when the maximum brightness is 100%. Since they are ratios, the correlations (a) and (b) partially overlap as shown in FIG.

  As described above, the projector 100 according to the embodiment to which the display device of the present invention and the method of controlling the display device are applied includes the light source unit 111, the light source drive unit 121, the storage unit 160, the control unit 170, and the optical sensor. 117 is provided. The light source driving unit 121 outputs a driving current to the light source unit 111. The storage unit 160 stores light source control information 161 that associates the duty ratio of the drive current output by the light source driving unit 121 with the brightness ratio of the light source unit 111 with respect to the maximum brightness. The control unit 170 sets the duty ratio of the drive current output by the light source drive unit 121 based on the light source control information 161. The optical sensor 117 detects the brightness of the light source unit 111. The control unit 170 detects the detection result of the optical sensor 117 when the light source driving unit 121 outputs the driving current having the first duty ratio, and the light source driving unit 121 detects the second duty ratio lower than the first duty ratio. The light source control information 161 is corrected based on the detection result of the optical sensor 117 when the drive current is output. Thereby, the brightness of the light source unit 111 is controlled based on the light source control information 161, and the light source control information 161 can be corrected by a simple operation. Therefore, it is possible to suppress the deterioration of the display quality in response to the change in the brightness of the light source unit 111 with respect to the power supplied to the light source unit 111.

  The control unit 170 controls the light source so as to compensate for the decrease in the brightness ratio of the light source unit 111 with respect to the duty ratio of the drive current output by the light source drive unit 121, which is caused by the rounding of the waveform of the drive current output by the light source drive unit 121. The information 161 is corrected. As a result, even if the duty ratio is substantially reduced due to the rounding of the waveform of the drive current, the brightness of the light source unit 111 can be appropriately controlled.

  The light source control information 161 includes information indicating a correlation curve between the duty ratio of the drive current output by the light source driving unit 121 and the brightness ratio of the light source unit 111. The control unit 170 corrects the light source control information 161 by shifting the correlation curve included in the light source control information 161. Thereby, the light source control information 161 can be corrected by a simple operation.

  The first duty ratio is a value associated with the maximum brightness of the light source unit 111 by the light source control information 161. Thereby, the light source control information 161 can be appropriately corrected based on a small number of measurement results. Further, for example, the second duty ratio is lower than the first duty ratio and is a duty ratio included in the polynomial section of the drive current-brightness ratio correlation included in the light source control information 161.

  The drive current output from the light source drive unit 121 to the light source unit 111 may have a frequency equal to or higher than a frequency band known as a human audible frequency band (for example, 20 Hz to 20 kHz). Specifically, the frequency of the PWM signal may be higher than 20 kHz, for example, 25 kHz or higher, or 30 kHz or higher. In this case, when the frequency of the drive current supplied to the light source unit 111 is high and is easily affected by the waveform rounding of the drive current, by correcting the light source control information 161, the brightness of the light source unit 111 can be appropriately controlled. ..

[Modification]
As illustrated in FIG. 3, the brightness of the light source becomes the maximum brightness in the section S11 corresponding to the region where the duty ratio is high. Due to this effect, in the sections S21 and S22 between the polynomial sections S1 and S2 and the section S11, the change in the brightness ratio of the light source with respect to the change in the duty ratio is steep, and the duty ratio is appropriately set according to the brightness ratio. The process of controlling to become complicated easily.

  The projector 100 may be configured to change the pulse width of the drive current output from the light source drive unit 121 to suppress the influence of the dullness in the region where the duty ratio is close to 100%. This case will be described as a modified example.

  FIG. 6 is an explanatory diagram showing an example of the drive current waveform of the light source unit 111, and corresponds to FIG. 3. The horizontal axis of FIG. 6 represents the brightness ratio of the light source, and the vertical axis represents the duty ratio of the drive current.

FIG. 6 shows the correlation between the duty ratio of the drive current and the brightness ratio of the light source in the modified example. The information regarding the correlation of the drive current-brightness ratio is included in the light source control information 161 in the form of an arithmetic expression, a function, a table, or the like.
6, (a) shows the correlation of the drive current-brightness ratio included in the light source control information 161 before correction, and (b) shows the correlation included in the light source control information 161 after correction in the above embodiment. .. (C) shows the correlation included in the light source control information 161 after correction in the modified example.

  Further, FIG. 7 is an explanatory diagram of the drive current waveform of the light source unit 111, and corresponds to FIG. 4. The vertical axis represents current and the horizontal axis represents the passage of time. In the figure, (a) shows the waveform of the PWM signal as an ideal rectangular wave, and (b) shows the waveform of the drive current output by the light source drive section 121.

In the modification, the PWM signal generation unit 122 outputs a PWM signal including a pulse ON time, that is, a pulse having a pulse width P02 and a pulse having an ON time P03. In this PWM signal, there are two types of off time of the pulse, PF2 and PF3. This PWM signal includes a pulse having a pulse width of P02, a pulse having an on time of P03, and off times PF2 and PF3 in one cycle T. The duty ratio of the PWM signal is the ratio of the sum of the ON times P02 and P03 for one cycle T.
The duty ratio of the PWM signal shown in FIG. 7 can be the same as that of the PWM signal shown in FIG. 3, for example. In other words, the long off-time PF2 can be set by changing the type of the on-time of the pulse and setting the pulse having the long on-time without changing the duty ratio with the PWM signal composed of the constant-width pulse.

Also in the modified example, the waveform of the drive current of the light source drive unit 121 becomes dull as shown in (b). In the modified example, since the PWM signal includes a long off time, in the region corresponding to this long off time, the current value is sufficiently reduced even when the dullness occurs, as indicated by the symbol D2.
Further, by combining a plurality of pulses having different pulse widths and including a plurality of pulses having different pulse widths in one cycle, it is possible to suppress the length of one off time even in a region where the duty ratio is low. Therefore, there is an advantage that the flicker of the light source of the light source unit 111 is unlikely to occur even when the duty ratio is low.

  In this modified example, as shown in FIG. 7, a plurality of pulses having different pulse widths are included in one cycle over the entire duty ratio. In this case, as shown in FIG. 6, in the drive current-brightness ratio correlation, the section S13 in which the light source has the maximum brightness (brightness ratio is 100%) is obtained from Q2 (corresponding to a duty ratio of 90%) in FIG. Is also a region with a high duty ratio.

  In the uncorrected drive current-brightness ratio correlation (a), when the section S11 is replaced by the section S13, the section S31 connecting the lower end Q12 of the section S13 in which the light source has the maximum brightness and the upper end Q11 of the polynomial section S3. Pay attention to the inclination. The slope of the section S31 is different from the section S21 described in the above embodiment, and specifically, the change of the brightness ratio with respect to the change of the duty ratio is gentle. Therefore, even in a region where the duty ratio is high, the brightness ratio of the light source can be controlled more finely and appropriately.

  In the corrected drive current-brightness ratio correlation shown in (c), the effect of including a plurality of pulses having different pulse widths in one cycle is more remarkable. When the correction is performed according to the change with time of the light source, the polynomial section shifts. Therefore, in the corrected drive current-brightness ratio correlation (c), the upper end of the polynomial section S4 is at the position of the point Q13. In a section S32 connecting the points Q13 and Q12, the change in the brightness ratio of the light source with respect to the change in the duty ratio is gentler than that in the section S22 of the drive current-brightness ratio correlation (b) described in the above embodiment. Is. Therefore, even in a region where the duty ratio is high, the brightness ratio of the light source can be controlled more finely and appropriately.

As described above, in the projector 100, the PWM signal generation unit 122 outputs the PWM signal including a plurality of types of pulses having different widths, and the light source drive unit 121 outputs the drive current including a plurality of types of pulses having different widths. It may be configured. In this case, the pulse interval can be expanded without changing the duty ratio of the drive current, and the influence of the current waveform rounding can be suppressed.
The waveforms of the PWM signal and the driving current shown in FIG. 7 are examples, and for example, three or more types of pulses having different pulse widths may be included in one cycle.

  The above-described embodiments and modified examples are preferred embodiments of the present invention. However, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. For example, in the above-described embodiment and modification, the control unit 170 sets the duty ratio of the PWM signal generation unit 122, the PWM signal of the set duty ratio is input to the light source drive unit 121, and the drive current is output. And The present invention is not limited to this, and the controller 170 may directly control the light source driver 121 to set the duty ratio of the drive current. Moreover, the specific numerical values such as the duty ratio and the brightness ratio shown in the above-described embodiment and modification are merely examples for description, and do not limit the application range of the present invention.

  Further, in the above-described embodiments and modified examples, as the light modulator 113 that modulates the light emitted from the light source, a configuration using three liquid crystal panels corresponding to RGB colors has been described as an example. The invention is not limited to this. For example, a system in which one liquid crystal panel and a color wheel are combined may be used. Alternatively, a system using three digital mirror devices (DMD), a DMD system combining one digital mirror device and a color wheel, or the like may be used. In addition to the liquid crystal panel and the DMD, an optical modulator that can modulate the light emitted from the light source can be used without any problem.

  Further, in the above-described embodiments and modified examples, the front projection type projector 100 that projects from the front of the screen SC is shown, but the present invention is not limited to this, and a rear projection type projector may be used. Further, the display device of the present invention is not limited to a projector that projects an image on the screen SC. For example, a liquid crystal display panel, a display panel such as a PDP (plasma display panel), and various display devices such as a monitor device having a self-luminous display panel and a television receiver are also included in the image display device of the present invention. The display panel may include an organic EL display panel called OLED (Organic light-emitting diode), OEL (Organic Electro-Luminescence), or the like.

  Moreover, each functional unit shown in FIG. 1 shows a functional configuration, and a specific mounting form is not particularly limited. In other words, it is not always necessary to individually implement hardware corresponding to each functional unit, and it is of course possible to implement a function of a plurality of functional units by executing a program by one processor. Further, in the above embodiment, some of the functions realized by software may be realized by hardware, or some of the functions realized by hardware may be realized by software. In addition, the specific detailed configurations of the other parts of the projector 100 can be arbitrarily changed without departing from the spirit of the present invention.

5 ... Remote control, 100 ... Projector (display device), 111 ... Light source part (light source), 112 ... Color separation part, 113 ... Light modulation device, 114 ... Projection optical system, 115 ... Liquid crystal panel, 117 ... Photosensor (detection part) ), 121 ... Light source drive section, 122 ... PWM signal generation section, 123 ... Optical modulation device drive section, 141 ... Operation panel, 142 ... Remote control light receiving section, 143 ... Input processing section, 145 ... Wireless communication section, 151 ... Image input I / F section, 153 ... Image processing section, 155 ... Frame memory, 160 ... Storage section, 161 ... Light source control information (control information), 170 ... Control section, 171 ... Projection control section, 172 ... Light source control section, 173 ... Correction control unit, 180 ... Internal bus, 200 ... Image supply device, SC ... Screen.

Claims (5)

A display device for displaying an image by light emitted from a light source,
A light source drive unit that outputs a drive current to the light source,
A storage unit that stores control information that associates a duty ratio of a drive current output by the light source drive unit and a brightness ratio with respect to the maximum brightness of the light source,
A control unit that sets the duty ratio of the drive current output by the light source drive unit based on the control information;
A detection unit that detects the brightness of the light source,
The control unit includes a detection result of the detection unit when the light source drive unit outputs a drive current having a first duty ratio associated with the maximum brightness of the light source by the control information, and the light source drive unit. Correcting the control information based on a detection result of the detection unit when a drive current having a second duty ratio lower than the first duty ratio is output,
A display device characterized by. The control information includes information indicating a correlation curve between the duty ratio of the drive current output by the light source drive unit and the brightness ratio of the light source,
The control unit corrects the control information by shifting a correlation curve included in the control information.
Claim 1 Symbol placement of the display device and said. The drive current output to the light source by the light source drive unit has a frequency equal to or higher than an audible frequency band,
Display device according to claim 1 or 2, characterized in. The light source drive section outputs a drive current including a plurality of types of pulses having different widths,
Display device according to any one of claims 1 to 3, wherein. A control method for a display device, comprising: a light source; and a light source drive section that outputs a drive current to the light source, wherein the display device displays an image by light emitted from the light source.
Based on control information associating the duty ratio of the drive current output by the light source drive unit and the brightness ratio with respect to the maximum brightness of the light source, setting the duty ratio of the drive current output by the light source drive unit,
Detecting the brightness of the light source,
The detection result of the brightness of the light source when the light source drive unit outputs a drive current having a first duty ratio associated with the maximum brightness of the light source by the control information, and the light source drive unit outputs the first result. Correcting the control information based on the detection result of the brightness of the light source when outputting the drive current having the second duty ratio lower than the duty ratio of
A method for controlling a display device, comprising:

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