JP2016164621A - Projector and method for controlling projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projector capable of suppressing the flickering of a lamp occurring when a light quantity is changed.SOLUTION: The projector includes a discharge lamp, a light modulator which modulates light from the discharge lamp, according to an image signal, a projection optical device which projects the light after modulation, a discharge lamp driving part which supplies drive power to the discharge lamp, and a control part which controls the discharge lamp driving part, so as to change the drive power supplied to the discharge lamp, according to brightness information based on the image signal. When the change amount of the brightness information on the discharge lamp is a predetermined threshold or more, in at least a part of the change period of the drive power, the control part controls the discharge lamp driving part, so as to supply an AC current having a frequency more than or equal to the frame frequency of the light modulator to the discharge lamp.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a projector and a projector control method.

  In recent years, the brightness of projectors has been increasing, and the durability of projectors, particularly the extension of lamp life, is extremely important. For the purpose of extending the life of the lamp, a technique has been proposed in which an alternating current having a fundamental frequency and an alternating current having a frequency lower than the fundamental frequency and having a length of at least a half cycle are alternately supplied to a discharge lamp (see below). Patent Document 1). In addition, for the purpose of improving the black reproducibility and expanding the dynamic range of the video, the brightness characteristics of the projected image are determined, and the lamp light quantity and the contrast of the projected image are adjusted according to the required characteristics. A liquid crystal projector provided with means has been proposed (Patent Document 2 below).

JP 2011-210564 A JP 2002-258401 A

  However, when a driving current including an alternating current having a length of about a half cycle at a low frequency is supplied to the lamp for a projector that changes the light amount of the lamp according to the brightness of the image, the lamp flickers depending on the image. There is a problem.

  One aspect of the present invention is made to solve the above-described problem, and is a projector capable of suppressing the flickering of a lamp that occurs when the amount of light of a discharge lamp is changed according to an image, and a projector One of the purposes is to provide a control method.

  In order to achieve the above object, a projector according to one aspect of the present invention includes a discharge lamp that emits light, a light modulation device that modulates light from the discharge lamp according to an image signal, and the light modulation device. A projection optical device that projects the light modulated by the light source, a discharge lamp driving unit that supplies driving power to the discharge lamp, and the driving power supplied to the discharge lamp according to luminance information based on the image signal. A control unit that controls the discharge lamp driving unit so that the change amount of the luminance information related to the discharge lamp is greater than or equal to a predetermined threshold in at least a part of the period during which the driving power changes. In this case, the discharge lamp driving unit is controlled such that an alternating current having a frequency equal to or higher than a frame frequency of the light modulation device is supplied to the discharge lamp.

As a result of investigating a phenomenon in which the discharge lamp flickers when the light quantity of the discharge lamp is changed according to the brightness of the image, the present inventors have found the following causes.
In the period in which the driving power changes, the pair of electrodes of the discharge lamp receives a larger load than in the period in which the driving power does not change. In addition, when a current having a non-uniform polarity is supplied to the discharge lamp, the load applied to each electrode becomes non-uniform, and as a result, a discharge occurs at a location different from the tip of the electrode where the discharge is originally desired. Therefore, it has been found that if the discharge continues in this state, a phenomenon that the position of the luminescent spot of the discharge lamp shifts with time, that is, a so-called arc jump occurs, causing flicker.

  With respect to this problem, according to the projector of one aspect of the present invention, when the amount of change in luminance information regarding the discharge lamp is equal to or greater than a predetermined threshold in at least a part of the period in which the driving power changes, the light modulation device An alternating current having a frequency equal to or higher than the frame frequency is supplied to the discharge lamp. As a result, the bias of the thermal load with respect to the pair of electrodes is reduced as compared with, for example, a case where a direct current is supplied during a period in which the driving power changes, and the protrusions at the tip of the electrodes are stably formed. As a result, flickering of the discharge lamp can be suppressed. Furthermore, since the alternating current supplied to the discharge lamp has a frequency equal to or higher than the frame frequency of the light modulation device, interference between the modulation of the light modulation device and the driving of the discharge lamp can be suppressed. As a result, image flicker can be suppressed.

In the projector according to one aspect of the present invention, when the change amount of the luminance information regarding the discharge lamp is smaller than the threshold, the control unit is configured such that the first electrode of the discharge lamp is an anode and the second electrode is an anode. The discharge lamp driving unit may be controlled such that a driving current in which the thermal load in one of the periods becomes larger than the thermal load in the other period is supplied to the discharge lamp.
According to this configuration, during a period in which the amount of change in luminance information related to the discharge lamp is smaller than the threshold value, a driving current having a biased polarity is supplied to the discharge lamp, so that the protrusion at the tip of the electrode of the discharge lamp grows and discharge is performed. It can be stabilized.

In the projector according to one aspect of the invention, the driving current may be a driving current including a direct current.
According to this configuration, the protrusion at the tip of the electrode of the discharge lamp can be sufficiently grown to stabilize the discharge.

In the projector according to one aspect of the present invention, the length of the period during which the direct current is supplied may be longer than the half period of the alternating current having a frequency equal to or higher than the frame frequency.
According to this configuration, the protrusion at the electrode tip of the discharge lamp can be grown more sufficiently to stabilize the discharge.

  A projector control method according to one aspect of the present invention includes a discharge lamp that emits light, a light modulation device that modulates light from the discharge lamp according to an image signal, and light modulated by the light modulation device. A projection optical device for projecting, wherein the driving power supplied to the discharge lamp is changed in accordance with luminance information based on the image signal, and at least a period during which the driving power changes In some cases, when the amount of change in luminance information related to the discharge lamp is equal to or greater than a predetermined threshold, an alternating current having a frequency equal to or higher than a frame frequency of the light modulation device is supplied to the discharge lamp.

  According to the projector control method of one aspect of the present invention, the bias of the thermal load with respect to the pair of electrodes of the discharge lamp is reduced, and the protrusions at the tip of the electrode are stably formed. As a result, flickering of the discharge lamp is suppressed. The Furthermore, since the alternating current supplied to the discharge lamp has a frequency equal to or higher than the frame frequency of the light modulation device, interference between modulation of the light modulation device and driving of the discharge lamp is avoided, and flickering of the image is suppressed. Can do.

It is a schematic block diagram of the projector of one Embodiment of this invention. It is sectional drawing of the discharge lamp in this embodiment. It is a block diagram which shows each component of the projector of this embodiment. It is a circuit diagram of the discharge lamp lighting device of this embodiment. It is a block diagram which shows the example of 1 structure of the control part of this embodiment. It is a figure which shows the mode of the protrusion of the electrode tip of a discharge lamp. It is a block diagram of the principal part of the projector of this embodiment. It is a figure which shows an example of the drive current waveform according to the time change of lamp drive electric power. It is a figure which shows the other example of the drive current waveform according to the time change of lamp drive electric power.

Hereinafter, a projector according to an embodiment of the invention will be described with reference to the drawings.
The scope of the present invention is not limited to the following embodiments, and can be arbitrarily changed within the scope of the technical idea of the present invention. In the following drawings, in order to make each configuration easy to understand, the actual structure may be different from the scale, number, or the like in each structure.

  As shown in FIG. 1, the projector 500 of the present embodiment includes a light source device 200, a collimating lens 305, an illumination optical system 310, a color separation optical system 320, a liquid crystal light valve 330R, a liquid crystal light valve 330G, and a liquid crystal. A light valve 330B (light modulation device), a cross dichroic prism 340, and a projection optical device 350 are provided.

  The light emitted from the light source device 200 passes through the collimating lens 305 and enters the illumination optical system 310. The collimating lens 305 collimates the light from the light source device 200.

  The illumination optical system 310 adjusts the illuminance of light emitted from the light source device 200 so as to be uniform on the liquid crystal light valve 330R, the liquid crystal light valve 330G, and the liquid crystal light valve 330B. Further, the illumination optical system 310 aligns the polarization direction of the light emitted from the light source device 200 with, for example, one direction of linearly polarized light. The reason is that the light emitted from the light source device 200 is effectively used by the liquid crystal light valve 330R and the liquid crystal light valves 330G and 330B.

  The light emitted from the illumination optical system 310 enters the color separation optical system 320. The color separation optical system 320 separates incident light into three color lights of red light (R), green light (G), and blue light (B). The three color lights are respectively modulated by the liquid crystal light valve 330R, the liquid crystal light valve 330G, and the liquid crystal light valve 330B corresponding to each color light. The liquid crystal light valve 330R, the liquid crystal light valve 330G, and the liquid crystal light valve 330B include a liquid crystal panel 560R, a liquid crystal panel 560G, and a liquid crystal panel 560B, which will be described later, and a pair of polarizing plates (not shown). The polarizing plates are disposed on the light incident side and the light emission side of each of the liquid crystal panel 560R, the liquid crystal panel 560G, and the liquid crystal panel 560B.

  The red light, the green light, and the blue light modulated by the liquid crystal light valve 330R, the liquid crystal light valve 330G, and the liquid crystal light valve 330B are combined by the cross dichroic prism 340. The combined light is incident on the projection optical device 350. The projection optical device 350 projects incident light onto the screen 700 (see FIG. 3). As a result, an image is displayed on the screen 700. As the configurations of the collimating lens 305, the illumination optical system 310, the color separation optical system 320, the cross dichroic prism 340, and the projection optical device 350, well-known configurations can be adopted.

FIG. 2 is a cross-sectional view showing the configuration of the light source device 200.
The light source device 200 includes a light source unit 210 and a discharge lamp lighting device (discharge lamp driving device) 10. FIG. 2 shows a cross-sectional view of the light source unit 210. The light source unit 210 includes a main reflecting mirror 112, a discharge lamp 90, and a sub reflecting mirror 50.

  The discharge lamp lighting device 10 supplies driving power (drive current) to the discharge lamp 90 to light the discharge lamp 90. The main reflecting mirror 112 reflects the light emitted from the discharge lamp 90 toward the main reflecting mirror 112 in the irradiation direction D. The irradiation direction D is parallel to the optical axis AX of the discharge lamp 90.

  The discharge lamp 90 has a rod-like shape extending along the irradiation direction D. One end of the discharge lamp 90 is a first end 90e1, and the other end of the discharge lamp 90 is a second end 90e2. The discharge lamp 90 is made of a translucent material such as quartz glass. The central portion of the discharge lamp 90 swells in a spherical shape, and the inside of the spherical portion is a discharge space 91. The discharge space 91 is filled with a gas that is a discharge medium containing a rare gas, a metal halide, or the like.

  In the discharge space 91, the tips of the first electrode 92 and the second electrode 93 protrude. The first electrode 92 is disposed on the first end portion 90 e 1 side of the discharge space 91. The second electrode 93 is disposed on the second end 90 e 2 side of the discharge space 91. The first electrode 92 and the second electrode 93 have a rod shape extending along the optical axis AX. In the discharge space 91, the tip of the first electrode 92 and the tip of the second electrode 93 are arranged so as to face each other with a predetermined distance. The first electrode 92 and the second electrode 93 are made of a metal material such as tungsten, for example.

  The first terminal 536 is provided at the first end 90 e 1 of the discharge lamp 90. The first terminal 536 and the first electrode 92 are electrically connected by a conductive member 534 that penetrates the inside of the discharge lamp 90. Similarly, the second terminal 546 is provided at the second end 90e2 of the discharge lamp 90. The second terminal 546 and the second electrode 93 are electrically connected by a conductive member 544 that penetrates the inside of the discharge lamp 90. The first terminal 536 and the second terminal 546 are made of a metal material such as tungsten, for example. As a material for the conductive members 534 and 544, for example, a molybdenum foil is used.

  The first terminal 536 and the second terminal 546 are connected to the discharge lamp lighting device 10. The discharge lamp lighting device 10 supplies driving power for driving the discharge lamp 90 to the first terminal 536 and the second terminal 546. As a result, arc discharge occurs between the first electrode 92 and the second electrode 93. Light (discharge light) generated by the arc discharge is radiated in all directions from the discharge position, as indicated by the dashed arrows.

  The main reflecting mirror 112 is fixed to the first end 90e1 of the discharge lamp 90 by a fixing member 114. The main reflecting mirror 112 reflects the light traveling toward the opposite side of the irradiation direction D in the discharge light toward the irradiation direction D. The shape of the reflecting surface (the surface on the discharge lamp 90 side) of the main reflecting mirror 112 is not particularly limited as long as the discharge light can be reflected in the irradiation direction D, and may be, for example, a spheroid or rotating Parabolic shape may be sufficient. For example, when the shape of the reflecting surface of the main reflecting mirror 112 is a parabolic shape, the main reflecting mirror 112 can convert the discharge light into light substantially parallel to the optical axis AX. Thereby, the collimating lens 305 can be omitted.

  The sub-reflecting mirror 50 is fixed to the second end 90 e 2 side of the discharge lamp 90 by a fixing member 522. The shape of the reflective surface (surface on the discharge lamp 90 side) of the sub-reflecting mirror 50 is a spherical shape that surrounds the portion of the discharge space 91 on the second end 90e2 side. The sub-reflecting mirror 50 reflects the light traveling toward the side opposite to the side on which the main reflecting mirror 112 is disposed in the discharge light toward the main reflecting mirror 112. Thereby, the utilization efficiency of the light radiated | emitted from the discharge space 91 can be improved.

  The material of the fixing member 114 and the fixing member 522 is not particularly limited as long as it is a heat resistant material that can withstand the heat generated from the discharge lamp 90, and is, for example, an inorganic adhesive. The method of fixing the arrangement of the main reflecting mirror 112 and the sub reflecting mirror 50 and the discharge lamp 90 is not limited to the method of fixing the main reflecting mirror 112 and the sub reflecting mirror 50 to the discharge lamp 90, and any method can be adopted. . For example, the discharge lamp 90 and the main reflecting mirror 112 may be independently fixed to an exterior housing (not shown) of the projector 500. The same applies to the sub-reflecting mirror 50.

Hereinafter, the circuit configuration of the projector 500 will be described.
FIG. 3 is a diagram illustrating an example of a circuit configuration of the projector 500 according to the present embodiment.
In addition to the optical system shown in FIG. 1, the projector 500 includes an image signal conversion unit 510, a DC power supply device 80, a liquid crystal panel 560R, a liquid crystal panel 560G and a liquid crystal panel 560B, an image processing device 570, and a CPU (Central Processing). Unit) 580.

  The image signal converter 510 converts an image signal 502 such as a luminance-color difference signal or an analog RGB signal input from the outside into a digital RGB signal having a predetermined word length, and converts the image signal 512R, the image signal 512G, and the image signal 512B. It is generated and supplied to the image processing device 570.

  The image processing device 570 performs image processing on each of the three image signals 512R, the image signal 512G, and the image signal 512B. The image processing device 570 supplies a drive signal 572R, a drive signal 572G, and a drive signal 572B for driving the liquid crystal panel 560R, the liquid crystal panel 560G, and the liquid crystal panel 560B to the liquid crystal panel 560R, the liquid crystal panel 560G, and the liquid crystal panel 560B, respectively.

  The DC power supply device 80 converts an AC voltage supplied from an external AC power supply 600 into a constant DC voltage. The DC power supply device 80 includes an image signal conversion unit 510 on the secondary side of a transformer (not shown, but included in the DC power supply device 80), an image processing device 570, and a discharge lamp lighting device 10 on the primary side of the transformer. Supply DC voltage.

  The discharge lamp lighting device 10 generates a high voltage between the electrodes of the discharge lamp 90 at the time of startup, and causes a dielectric breakdown to form a discharge path. Thereafter, the discharge lamp lighting device 10 supplies the drive current I for the discharge lamp 90 to maintain the discharge.

  The liquid crystal panel 560R, the liquid crystal panel 560G, and the liquid crystal panel 560B are provided in the liquid crystal light valve 330R, the liquid crystal light valve 330G, and the liquid crystal light valve 330B, respectively. Each of the liquid crystal panel 560R, the liquid crystal panel 560G, and the liquid crystal panel 560B, based on the drive signals 572R, 572G, and 572B, receives the color light incident on the liquid crystal panel 560R, the liquid crystal panel 560G, and the liquid crystal panel 560B via the optical system described above. Modulates transmittance (luminance).

  The CPU 580 controls various operations from the start of lighting of the projector 500 to the turning off of the projector 500. For example, in the example of FIG. 3, a lighting command or a lighting command is output to the discharge lamp lighting device 10 via the communication signal 582. The CPU 580 receives lighting information of the discharge lamp 90 from the discharge lamp lighting device 10 via the communication signal 584.

Hereinafter, the configuration of the discharge lamp lighting device 10 will be described.
FIG. 4 is a diagram illustrating an example of a circuit configuration of the discharge lamp lighting device 10.
As shown in FIG. 4, the discharge lamp lighting device 10 includes a power control circuit 20, a polarity inversion circuit 30, a light source control unit 40, an operation detection unit 60, and an igniter circuit 70.

  The power control circuit 20 generates drive power (lamp drive power) to be supplied to the discharge lamp 90. In the present embodiment, the power control circuit 20 includes a down chopper circuit that receives the voltage from the DC power supply device 80 as an input, steps down the input voltage, and outputs a DC current Id.

  The power control circuit 20 includes a switch element 21, a diode 22, a coil 23, and a capacitor 24. The switch element 21 is composed of, for example, a transistor. In the present embodiment, one end of the switch element 21 is connected to the positive voltage side of the DC power supply device 80, and the other end is connected to the cathode terminal of the diode 22 and one end of the coil 23.

  One end of the capacitor 24 is connected to the other end of the coil 23, and the other end of the capacitor 24 is connected to the anode terminal of the diode 22 and the negative voltage side of the DC power supply device 80. A current control signal is input to the control terminal of the switch element 21 from a light source control unit 40 described later, and ON / OFF of the switch element 21 is controlled. For example, a PWM (Pulse Width Modulation) control signal may be used as the current control signal.

  When the switch element 21 is turned on, a current flows through the coil 23 and energy is stored in the coil 23. Thereafter, when the switch element 21 is turned OFF, the energy stored in the coil 23 is released through a path passing through the capacitor 24 and the diode 22. As a result, a direct current Id corresponding to the proportion of time during which the switch element 21 is turned on is generated.

  The polarity inversion circuit 30 inverts the polarity of the direct current Id input from the power control circuit 20 at a predetermined timing. As a result, the polarity inversion circuit 30 generates and outputs a drive current I that is a direct current that lasts for a controlled time or an alternating current that has an arbitrary frequency. In the present embodiment, the polarity inverting circuit 30 is configured by an inverter bridge circuit (full bridge circuit).

  The polarity inversion circuit 30 includes a first switch element 31, a second switch element 32, a third switch element 33, and a fourth switch element 34, which are configured by transistors, for example. In the polarity inversion circuit 30, the first switch element 31 and the second switch element 32 connected in series, and the third switch element 33 and the fourth switch element 34 connected in series are connected in parallel to each other. It has a configuration. The polarity inversion control signal is input from the light source control unit 40 to the control terminals of the first switch element 31, the second switch element 32, the third switch element 33, and the fourth switch element 34, respectively. On / off operations of the first switch element 31, the second switch element 32, the third switch element 33, and the fourth switch element 34 are controlled based on the polarity inversion control signal.

  In the polarity inversion circuit 30, the operation of alternately turning on / off the first switch element 31 and the fourth switch element 34, and the second switch element 32 and the third switch element 33 is repeated. Thereby, the polarity of the direct current Id output from the power control circuit 20 is alternately inverted. From the common connection point of the first switch element 31 and the second switch element 32 and the common connection point of the third switch element 33 and the fourth switch element 34, the same polarity state is continued for a controlled time. A drive current I that is a direct current or a drive current I that is an alternating current having a controlled frequency is generated and output.

  That is, in the polarity inverting circuit 30, when the first switch element 31 and the fourth switch element 34 are ON, the second switch element 32 and the third switch element 33 are OFF, and the first switch element 31 and When the fourth switch element 34 is OFF, the second switch element 32 and the third switch element 33 are controlled to be ON. Thus, when the first switch element 31 and the fourth switch element 34 are ON, the drive current I flowing from the one end of the capacitor 24 in the order of the first switch element 31, the discharge lamp 90, and the fourth switch element 34 is Occur. When the second switch element 32 and the third switch element 33 are ON, a drive current I that flows from one end of the capacitor 24 in the order of the third switch element 33, the discharge lamp 90, and the second switch element 32 is generated.

  In the present embodiment, the combined portion of the power control circuit 20 and the polarity inversion circuit 30 corresponds to the discharge lamp driving unit 230. That is, the discharge lamp driving unit 230 supplies a driving current I (driving power) for driving the discharge lamp 90 to the discharge lamp 90.

The light source control unit 40 controls the discharge lamp driving unit 230. In the example of FIG. 4, the light source control unit 40 controls the power control circuit 20 and the polarity inversion circuit 30 to hold the drive current I with the same polarity, the current value of the drive current I (the power of the drive power). Value), frequency, and other parameters. The light source control unit 40 performs polarity inversion control on the polarity inversion circuit 30 to control the holding time for the drive current I to remain the same polarity, the frequency of the drive current I, and the like, according to the polarity inversion timing of the drive current I. The light source controller 40 performs current control on the power control circuit 20 to control the current value of the output direct current Id.
The light source control unit 40 of the present embodiment corresponds to the control unit in the claims.

  The configuration of the light source control unit 40 is not particularly limited. In the present embodiment, the light source control unit 40 includes a system controller 41, a power control circuit controller 42, and a polarity inversion circuit controller 43. The light source control unit 40 may be partially or entirely configured with a semiconductor integrated circuit.

  The system controller 41 controls the power control circuit 20 and the polarity inversion circuit 30 by controlling the power control circuit controller 42 and the polarity inversion circuit controller 43. The system controller 41 may control the power control circuit controller 42 and the polarity inversion circuit controller 43 based on the lamp voltage Vla and the drive current I detected by the operation detection unit 60.

  In the present embodiment, the system controller 41 includes a storage unit 44. However, the storage unit 44 may be provided independently of the system controller 41.

  The system controller 41 may control the power control circuit 20 and the polarity inversion circuit 30 based on information stored in the storage unit 44. The storage unit 44 may store, for example, information related to drive parameters such as a holding time during which the drive current I continues with the same polarity, a current value of the drive current I, a frequency, a waveform, and a modulation pattern.

  The power control circuit controller 42 controls the power control circuit 20 by outputting a current control signal to the power control circuit 20 based on the control signal from the system controller 41.

  The polarity inversion circuit controller 43 controls the polarity inversion circuit 30 by outputting a polarity inversion control signal to the polarity inversion circuit 30 based on the control signal from the system controller 41.

  The light source control unit 40 is realized by using a dedicated circuit, and performs the above-described control and various controls associated with processing to be described later. Alternatively, the light source control unit 40 may function as a computer by the CPU executing a control program stored in the storage unit 44, for example, and may be configured to perform various controls associated with these processes.

  FIG. 5 is a diagram for explaining another configuration example of the light source control unit 40. As shown in FIG. 5, the light source control unit 40 functions as current control means 40-1 for controlling the power control circuit 20 and polarity reversal control means 40-2 for controlling the polarity reversal circuit 30 according to the control program. It may be configured.

  In the example shown in FIG. 4, the light source control unit 40 is configured as a part of the discharge lamp lighting device 10. On the other hand, the CPU 580 may be configured to perform a part of the function of the light source control unit 40.

  The operation detection unit 60 detects, for example, the lamp voltage of the discharge lamp 90 and outputs lamp voltage information to the light source control unit 40. The operation detection unit 60 detects the drive current I and outputs the drive current information to the light source control unit 40. An electric current detection part etc. may be included. In the present embodiment, the operation detection unit 60 is configured to include a first resistor 61, a second resistor 62, and a third resistor 63. The lamp voltage of the discharge lamp 90 means the voltage between the electrodes of the discharge lamp 90.

  In the operation detection unit 60, the voltage detection unit detects the lamp voltage Vla in parallel with the discharge lamp 90 using a voltage divided by the first resistor 61 and the second resistor 62 connected in series with each other. In the present embodiment, the current detection unit detects the drive current I based on the voltage generated in the third resistor 63 connected in series to the discharge lamp 90.

  The igniter circuit 70 operates only when the discharge lamp 90 starts to be lit. The igniter circuit 70 is a high voltage (discharge) necessary for forming a discharge path by dielectric breakdown between the electrodes of the discharge lamp 90 (between the first electrode 92 and the second electrode 93) at the start of lighting of the discharge lamp 90. (A voltage higher than that during normal lighting of the lamp 90) is supplied between the electrodes of the discharge lamp 90 (between the first electrode 92 and the second electrode 93). In the present embodiment, the igniter circuit 70 is connected in parallel with the discharge lamp 90.

  6A and 6B show the tip portions of the first electrode 92 and the second electrode 93. FIG. Protrusions 552p and 562p are formed at the tips of the first electrode 92 and the second electrode 93, respectively. The discharge generated between the first electrode 92 and the second electrode 93 mainly occurs between the protrusion 552p and the protrusion 562p. When there are the protrusion 552p and the protrusion 562p as in the present embodiment, the movement of the discharge position (arc position) in the first electrode 92 and the second electrode 93 can be suppressed as compared with the case where there is no protrusion.

  FIG. 6A shows a first polarity state in which the first electrode 92 operates as an anode and the second electrode 93 operates as a cathode. In the first polarity state, electrons move from the second electrode 93 (cathode) to the first electrode 92 (anode) by discharge. Electrons are emitted from the cathode (second electrode 93). Electrons emitted from the cathode (second electrode 93) collide with the tip of the anode (first electrode 92). Heat is generated by the collision, and the temperature of the tip (projection 552p) of the anode (first electrode 92) rises.

  FIG. 6B shows a second polarity state in which the first electrode 92 operates as a cathode and the second electrode 93 operates as an anode. In the second polarity state, electrons move from the first electrode 92 to the second electrode 93, contrary to the first polarity state. As a result, the temperature of the tip (projection 562p) of the second electrode 93 rises.

  Thus, the temperature of the anode with which the electrons collide tends to be higher than the temperature of the cathode that emits electrons. Here, if the temperature of one electrode is higher than that of the other electrode, it may cause various problems. For example, when the tip of an electrode that becomes high temperature melts excessively, unintended electrode deformation may occur. As a result, the distance between the electrodes (arc length) may deviate from an appropriate value, and the illuminance may not be stable. On the other hand, if the tip of the electrode that is at a low temperature is not sufficiently melted, there is a possibility that minute irregularities generated at the tip may remain undissolved. As a result, an arc jump may occur.

FIG. 7 is a block diagram of a main part of the projector.
As illustrated in FIG. 7, the image processing device 570 includes an image analysis unit 574 and an image processing unit 576. The image analysis unit 574 analyzes an image signal input from the outside, and extracts luminance information representing the luminance of a video within a certain frame period to be displayed based on the image signal. The length of the frame period for extracting luminance information based on the image signal can be set as appropriate. The luminance information based on the image signal is, for example, information such as an average picture level (APL) based on a histogram indicating the appearance number distribution of the number of gradations or highlight luminance. Since the image analysis unit 574 needs to obtain luminance information of an image to be displayed thereafter, it is desirable to include a buffer for temporarily storing the image signal, a frame memory (not shown), and the like.

  The image analysis unit 574 outputs luminance information based on the image signal obtained by the above method as a control signal to the image processing unit 576 together with the image signal. Based on the input control signal and image signal, the image processing unit 576 performs arbitrary image processing such as expansion processing for expanding the dynamic range of the video. The image signal after the image processing is sent to the light valve driver 335, converted into an actual voltage, and a predetermined voltage is supplied to the liquid crystal light valve 330.

  On the other hand, the image analysis unit 574 outputs luminance information based on the image signal obtained by the above method as a control signal to the light source control unit 40 in parallel with the image processing unit 576. Further, the image analysis unit 574 detects the frame frequency from the image signal, and outputs the detected frame frequency information to the light source control unit 40. Based on the control signal, for example, the light source control unit 40 has a relatively small lamp driving power and a value of APL in a period in which the APL value as luminance information based on the image signal is relatively small (the image is dark). In a relatively large period (the image is bright), a power control signal is generated so that the lamp driving power is relatively large and is supplied to the discharge lamp lighting device 10. The lamp driving power is driving power supplied to the discharge lamp 90.

FIG. 8 is a diagram illustrating an example of a drive current waveform corresponding to a change over time in lamp drive power as luminance information regarding the discharge lamp 90.
The upper part of FIG. 8 shows the time change of the lamp driving power, the horizontal axis shows the time, and the vertical axis shows the lamp driving power. In this example, the lamp driving power is constant at W1 during the period from t0 to t1, the lamp driving power increases from W1 to W3 during the period from t1 to t2, and the lamp driving power is constant at W3 during the period from t2 to t3. In the period from t3 to t4, the lamp driving power decreases from W3 to W2, and in the period after t4, the lamp driving power is constant at W2. The amount of change in lamp driving power from W1 to W3 is ΔWa, and the amount of change in lamp driving power from W3 to W2 is ΔWb.

  The lower part of FIG. 8 shows the drive current waveform, the horizontal axis shows time, and the vertical axis shows the drive current value. In this example, the average current value during the period of the first polarity is + Im, and the average current value during the period of the second polarity is -Im. The first period PH1 during which the drive current including the DC current Idc is supplied to the discharge lamp 90 during the period from t0 to t1, when the lamp driving power is constant, the period from t2 to t3, and the period after t4. It has become. The driving current including the direct current Idc in the first period PH1 is the first electrode in any one of the period in which the first electrode 92 of the discharge lamp 90 is the anode and the period in which the second electrode 93 is the anode. 92 or the second electrode 93 is a drive current that makes the thermal load larger than the thermal load of the first electrode 92 or the second electrode 93 in the other period.

  On the other hand, the frame frequency of the liquid crystal panels 560R, 560G, and 560B (light modulation device) during the period from t1 to t2 when the lamp driving power changes by ΔWa and during the period from t3 to t4 when the lamp driving power changes by ΔWb. The second period PH <b> 2 in which the alternating current Iac having the above frequency, for example, a frequency of about 200 to 400 Hz is supplied to the discharge lamp 90 is set. As will be described later, flickering of the discharge lamp 90 can be suppressed by supplying such an alternating current Iac to the discharge lamp 90 during a period when the lamp driving power changes.

  During the period in which the lamp driving power changes, the degree of flickering of the discharge lamp 90 changes according to the amount of change in the lamp driving power. Specifically, if the driving current including the direct current Idc is supplied to the discharge lamp when the amount of change in the lamp driving power is equal to or greater than a predetermined threshold, the discharge lamp 90 is likely to flicker. On the other hand, if the amount of change in the lamp driving power is smaller than a predetermined threshold, even if a driving current including the direct current Idc is supplied to the discharge lamp 90, there is little possibility that the discharge lamp 90 will flicker. Therefore, the threshold value of the change amount of the lamp driving power, which is a criterion for determining whether or not to supply the driving current including the direct current to the discharge lamp 90 during the period in which the lamp driving power changes, indicates the occurrence of flicker of the discharge lamp 90 What is necessary is just to determine suitably while seeing. Assuming that the lamp driving power change amount threshold value is ΔWs, in the example shown in FIG. 8, the change amount ΔWa is larger than the threshold value ΔWs (ΔWa> ΔWs), and the change amount ΔWb is larger than the threshold value ΔWs (ΔWb> ΔWs). .

  Further, the length of the period during which the direct current Idc included in the drive current in the first period PH1 is supplied is longer than the half period of the alternating current Iac having a frequency equal to or higher than the frame frequency in the second period PH2. As a result, the protrusions at the tips of the first electrode 92 and the second electrode 93 of the discharge lamp 90 are sufficiently melted to form the protrusions, and the discharge can be stabilized.

FIG. 9 is a diagram illustrating another example of a drive current waveform corresponding to a temporal change in lamp drive power.
The upper part of FIG. 9 shows the time change of the lamp driving power. In this example, the lamp driving power is constant at W1 during the period from t0 to t1, the lamp driving power increases from W1 to W3 during the period from t1 to t2, and the lamp driving power is constant at W3 during the period from t2 to t3. In the period from t3 to t4, the lamp driving power decreases from W3 to W2 ′, and in the period after t4, the lamp driving power is constant at W2 ′. The amount of change in lamp driving power from W1 to W3 is ΔWa, and the amount of change in lamp driving power from W3 to W2 ′ is ΔWb ′. In the example shown in FIG. 9, the change amount ΔWa is larger than the threshold value ΔWs (ΔWa> ΔWs), and the change amount ΔWb ′ is smaller than the threshold value ΔWs (ΔWb ′ <ΔWs).

  The lower part of FIG. 9 shows the drive current waveform. In this example, as in FIG. 8, the average current value during the period of the first polarity is + Im, and the average current value during the period of the second polarity is -Im. Further, the period from t0 to t1, when the lamp driving power is constant, the period from t2 to t3, and the period after t4 are the first period PH1 during which the driving current including the DC current Idc is supplied to the discharge lamp. . The drive current including the direct current Id in the first period PH1 is the first electrode in any one of the period in which the first electrode 92 of the discharge lamp 90 is the anode and the period in which the second electrode 93 is the anode. 92 or the second electrode 93 is a drive current that makes the thermal load larger than the thermal load of the first electrode 92 or the second electrode 93 in the other period. These periods are the same as in the example of FIG.

  On the other hand, the period from t1 to t2 when the lamp driving power changes is the second period PH2, and the period from t3 to t4 is the third period PH3. The two periods, the second period PH2 and the third period PH3, Among these, the change amount ΔWa in the second period PH2 is larger than the threshold value. Therefore, an alternating current Iac having a frequency equal to or higher than the frame frequency of the liquid crystal panel, for example, a frequency of about 200 to 400 Hz is supplied to the discharge lamp 90. On the other hand, the change amount ΔWb ′ in the third period PH3 is smaller than the threshold value. Accordingly, the driving current including the direct current Idc is supplied to the discharge lamp 90 as in the first period PH1 in which the lamp driving power is constant.

  As described above, the projector control method according to the present embodiment controls the discharge lamp driving unit 230 to change the lamp driving power supplied to the discharge lamp 90 according to the luminance information based on the image signal, and the lamp In at least a part of the period in which the driving power changes, when the amount of change in luminance information related to the discharge lamp 20 is equal to or greater than a predetermined threshold, an alternating current having a frequency equal to or higher than the frame frequency of the liquid crystal panel is supplied to the discharge lamp 90. Thus, the discharge lamp driving unit 230 is controlled.

  In the projector 500 of the present embodiment, when the amount of change in luminance information related to the discharge lamp 20 is equal to or greater than a predetermined threshold during the period when the lamp driving power changes, the AC current Ia having a frequency equal to or higher than the frame frequency of the liquid crystal panel is released. It is supplied to the electric lamp 90. Thereby, the bias of the thermal load with respect to the 1st electrode 92 and the 2nd electrode 93 of the discharge lamp 90 becomes small, and the protrusion of an electrode tip is formed stably. As a result, flickering of the discharge lamp 90 can be suppressed. Furthermore, since the alternating current Iac supplied to the discharge lamp 90 has a frequency equal to or higher than the frame frequency of the liquid crystal panel, interference between the modulation of the liquid crystal panel and the driving of the discharge lamp 90 can be suppressed. Thereby, the flickering of the image on the screen 700 can be suppressed.

The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above-described embodiment, an example in which alternating current is supplied in the entire period in which the lamp driving power changes when the amount of change in the lamp driving power is greater than the threshold value has been described. Alternatively, an alternating current may be supplied by at least a part of the driving current, and a driving current including a direct current may be supplied by the rest. Further, in the above embodiment, the start time of the lamp drive power change period and the start time of the alternating current supply period coincide, and the end time of the lamp drive power change period and the end time of the alternating current supply period coincide. However, these times may be slightly different. In addition, the specific configuration of each part of the projector is not limited to the above embodiment, and can be changed as appropriate.

  Moreover, in the said embodiment, although the variation | change_quantity of the lamp drive power was mentioned as an example of the variation | change_quantity of the luminance information regarding the discharge lamp 90, it is not restricted to this, For example, the variation | change_quantity of the light quantity of the light inject | emitted from the discharge lamp 90 is used. It may be adopted. In that case, more specifically, the light amount detection unit (not shown) is provided between the discharge lamp 90 and the liquid crystal panels 560R, 560G, and 560B, and detects the light amount at the position where the light amount detection unit is disposed. The light amount detection unit is provided in the exterior casing and detects reflected light of light projected from the projection optical device 350. By these, it is good also as detecting the variation | change_quantity of the luminance information regarding a discharge lamp.

  In the above embodiment, the variation in lamp driving power as the luminance information related to the discharge lamp 90 is based on the variation in luminance information based on the image signal described above. Therefore, the light source control unit 40 supplies the drive current supplied to the discharge lamp 90 from the discharge lamp driving unit 230 by the threshold value of the change amount of the luminance information based on the image signal corresponding to the threshold value ΔWs of the change amount of the lamp drive power described above. You may control.

  In the above embodiment, an example in which the present invention is applied to a transmissive projector has been described. However, the present invention can also be applied to a reflective projector. Here, the “transmission type” means that a liquid crystal light valve including a liquid crystal panel or the like is a type that transmits light. “Reflective type” means that the liquid crystal light valve reflects light. The light modulation device is not limited to a liquid crystal panel or the like, and may be a light modulation device using a micromirror, for example.

  In the above-described embodiment, the example of the projector 500 using the three liquid crystal panels 560R, 560G, and 560B (liquid crystal light valves 330R, 330G, and 330B) has been described. However, the present invention uses only one liquid crystal panel. The present invention can also be applied to a projector using four or more liquid crystal panels.

  DESCRIPTION OF SYMBOLS 10 ... Discharge lamp lighting device, 40 ... Light source control part, 90 ... Discharge lamp, 230 ... Discharge lamp drive part, 330, 330R, 330G, 330B ... Liquid crystal light valve (light modulation apparatus), 350 ... Projection optical apparatus, 500 ... projector.

Claims (5)

A discharge lamp that emits light;
A light modulation device that modulates light from the discharge lamp according to an image signal;
A projection optical device for projecting light modulated by the light modulation device;
A discharge lamp driving unit for supplying driving power to the discharge lamp;
A control unit that controls the discharge lamp driving unit to change the driving power supplied to the discharge lamp according to luminance information based on the image signal,
The control unit has an alternating current having a frequency equal to or higher than the frame frequency of the light modulation device when the amount of change in luminance information regarding the discharge lamp is equal to or greater than a predetermined threshold in at least a part of a period during which the drive power changes. The projector controls the discharge lamp driving unit so that is supplied to the discharge lamp.   When the amount of change in the luminance information related to the discharge lamp is smaller than the threshold, the control unit is one of a period in which the first electrode of the discharge lamp is an anode and a period in which the second electrode is an anode. 2. The projector according to claim 1, wherein the discharge lamp driving unit is controlled such that a driving current in which a thermal load in a period is larger than a thermal load in the other period is supplied to the discharge lamp.   The projector according to claim 2, wherein the drive current is a drive current including a direct current.   4. The projector according to claim 3, wherein a length of a period during which the direct current is supplied is longer than a half period of an alternating current having a frequency equal to or higher than the frame frequency. Control of a projector comprising: a discharge lamp that emits light; a light modulation device that modulates light from the discharge lamp according to an image signal; and a projection optical device that projects light modulated by the light modulation device A method,
Changing the driving power supplied to the discharge lamp according to the luminance information based on the image signal,
When the amount of change in luminance information related to the discharge lamp is greater than or equal to a predetermined threshold during at least part of the period during which the drive power changes, an alternating current having a frequency equal to or higher than the frame frequency of the light modulation device is supplied to the discharge lamp. A projector control method comprising: supplying a projector.

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