JP2004212890A - Projection type system and its operating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an operating method for a projection type system that can suppress a flicker and minimize gradation disorder at the same time by superposing a pulse current on a DC lamp current in synchronism with a specified segment while stabilizing an arc by superposing the pulse current on the DC lamp current. <P>SOLUTION: The operating method for the projection type system which projects images on a screen (7) by sequentially passing color segments (3a) ... obtained by dividing into a plurality of pieces the light ψ emitted by a high pressure discharge lamp (1) turned on with a DC current is characterized in that the pulse current (P) is superposed on the DC lamp current (R) of the high pressure discharge lamp (1) in synchronism with at least one specified color segment. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a projection type system equipped with an optical element such as a color filter and a method of operating the same.
[0002]
[Prior art]
As a known projection system such as a projector, there is an invention described in JP-A-2002-49097. This is the invention described in U.S. Pat. No. 5,608,294 (Tokuhyohei 10-501919). That is, the pulse current (a predetermined number of half cycles of the lamp current) is added to the portion after each half cycle of the AC lamp current (C). It is possible to suppress the flicker of the arc by superimposing a current pulse having the same polarity as the lamp current generated in one-half of the lamp current. " It is an object of the present invention to provide an optimum projection system with less gradation disturbance by superimposing a current on a specific color segment of a color filter incorporated in the projection system in synchronization. Note that the gradation is a stage (degree) of digital change of lightness that changes from white to gray to black, and if this is disturbed, the lightness of each color of an image projected on a screen will also be disturbed.
[0003]
FIG. 3 is a diagram for explaining a waveform of the above-described conventional AC lamp current (C) and a waveform of light (Φ) applied to the color filter, and FIG. 5 is a diagram showing the relationship between the electrode and the arc in the AC lamp (C). It is a figure explaining a state. This type of projection system has the following problems caused by using alternating current as the lamp current (C). That is, (i) the direction of electron emission between the electrodes (1a ') and (1b') in the high-pressure discharge lamp is switched between the positive half cycle (c1) and the negative half cycle (c2) of the AC lamp current (C). Therefore, the bright points of the arc (A ') are generated at two places (K1') and (K2 '). That is, the bright spots (K1 ') and (K2') of the arc (A ') are not generated at the middle point of the electrodes (1a') and (1b '), and are not generated at one of the electrodes (1a') or (1b '). Occurs nearby. Therefore, in the case of AC lighting, the bright spots (K1 ') and (K2') are generated alternately each time the direction of the current (C) is switched. That is, a bright spot (K1 ′) is generated when the current (C) is a positive half cycle (C1), and a bright spot (K2 ′) is generated when the current (C) is a negative half cycle (C2).
[0004]
In such a state, since the electrodes (1a ') and (1b') are not completely the same, each time the direction of the current (C) flowing through the electrodes (1a ') and (1b') is switched, the electrode (1a ') is switched. ) The state of the electrons emitted from (1b ') is not the same. This means that the state of the light emitted from the high-pressure discharge lamp changes every half cycle (c1) (c2). In other words, the light (Φ) irradiating the color filter generated due to the electron emission is not exactly the same in the positive half cycle (c1) and the negative half cycle (c2), but is in the positive half cycle (c2). An error of ΔΦ occurs between the light generated in (c1) and the light generated in the negative half cycle (c2). This causes grayscale dropout in a projection system using an optical element (4) such as a DMD (digital mirror device).
[0005]
(Ii) In addition, as described above, in the above-described prior art, since the polarity is switched after the superposition of the current pulse, the waveform of the luminous flux change causes an undershoot (U) in accordance with the change of the current (C), which is complicated. It becomes a waveform. Since such complicatedly changing light (Φ) is applied to a required color segment of a color filter built in the projection type system, a required color balance can be obtained by correcting and controlling the light flux change. The DMD must be controlled as follows.
[0006]
However, the change of the light beam waveform in the pulse current superimposed portion is very complicated, and the reproducibility is difficult. Therefore, even if the above-described correction control is performed, the projection type system using the DMD can completely eliminate the gradation loss. This could not be solved, and this was the cause of the gradation loss characteristic of the AC lamp that appeared when the AC lamp was used. As described above, since the pulse waveform of the positive half cycle (c1) and the pulse waveform of the negative half cycle (c2) are not exactly the same, the AC lighting current (C) is synchronized with, for example, a red color segment other than white. ), The effect becomes particularly large.
[0007]
(Iii) In addition, in the case of the conventional method in which the pulse current (P) is superimposed on the AC lamp current (C), the superposition position of the pulse current (P) for preventing flicker is in each half cycle (c1) (c2). . In other words, the pulse current (P) cannot be superimposed at an arbitrary position, so that it is difficult to superimpose the pulse current (P) in synchronization with a plurality of segments (3a) of the color filter. If this is attempted, the waveforms of the positive half cycle (c1) and the negative half cycle (c2) will not be the same, and a DC component will be generated in the AC lamp current (C). It is not preferable because it may affect the life characteristics of the steel.
[0008]
[Patent Document 1]
JP 2002-49097 A [Patent Document 2]
U.S. Pat. No. 5,608,294 (Japanese Unexamined Patent Publication No. 10-501919)
[0009]
[Problems to be solved by the invention]
The present invention stabilizes an arc by superimposing a pulse current on a DC lamp current, and simultaneously synchronizes a pulse current with a predetermined segment (including a case in which a pulse current is superimposed in synchronization with a plurality of segments) to convert the pulse current into a DC lamp current. It is an object of the present invention to provide a projection system capable of simultaneously suppressing flicker caused by an arc jump and minimizing gradation disturbance, and a method of operating the projection system.
[0010]
[Means for Solving the Problems]
Claim 1 relates to a method of operating the projection type system according to the present invention, wherein the light (Φ) emitted from the DC-lit high-pressure discharge lamp (1) is divided into a plurality of color filters (3). A method of operating a projection type system for projecting an image on a screen (7) sequentially through the segments (3a)... For steady operation of the high-pressure discharge lamp (1) in synchronization with at least one specific color segment. The pulse current (P) is superimposed on the DC lamp current (R). "
[0011]
According to this, since the current (R) for lighting the high-pressure discharge lamp (1) is DC, the pulse current (P) can be superimposed at any time, and therefore, the AC lamp current (C) Although it was very difficult in the above case, the pulse current (P) can be superimposed on one or more specific color segments (3a).
[0012]
In addition, since the lamp lighting current (R) is DC, not only the above-mentioned gradation drop of the AC characteristic, which was not avoided when the AC current was used as the lamp current (C), but also the pulse current Even when (P) is superimposed, the current waveform is very simple, and the luminous flux change waveform is a very simple waveform with no undershoot according to the change in the current waveform. Therefore, the correction control accompanying the change in the light flux is also very simple, and the gradation dropout can be controlled to a minimum.
[0013]
Claim 2 relates to a projection type system for carrying out the method, wherein the light (Φ) emitted from the high pressure discharge lamp (1) is divided into a color segment (3a) obtained by dividing a color filter (3) into a plurality of segments. ) (3b) ... is a projection type system for projecting an image on the screen (7) by sequentially passing it through the high pressure discharge lamp (1) and supplying a DC lamp current (R) to the high pressure discharge lamp (1). A DC lighting means (5) for periodically superimposing a pulse current (P) on the DC lamp current (R) for lighting, and synchronizing the pulse current (P) with at least one specific color segment. The method can be carried out.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 shows an embodiment of the projection type system of the present invention. Here, a projection type system using, for example, a 60 Hz video image is taken as an example. Of course, the present invention is not limited to this. In this system, a high-pressure discharge lamp (1) mounted on a reflector (2) as a light source (E) and lit by a DC lamp current (R) supplied from a DC lighting means (5) is used. The light emitted from 1) is directly or reflected by the reflector (2) and is emitted to the color filter (3) in front.
[0015]
As an example of the color filter (3), three color segments (3a), (3b), and (3c) of red, green, and blue formed by a dichroic filter having a property of selectively transmitting the wavelength of visible light. Alternatively, a rotating disk divided into four colors, in which a white color segment (3d) is added thereto, is configured to be rotatable around its axis, and is rotated at a constant speed by a color filter driving device (8). Is controlled as follows. For example, when the video frequency is 60 Hz per frame (one screen changes at 60 times per second), if the color filter (3) rotates at twice the speed, for example, the video filter rotates at 120 Hz. Become.
[0016]
When the light (φ1) from the light source (E) sequentially irradiates each segment (3a) (3b) (3c)... Of the color filter (3) rotating at a constant speed in a time-division manner, the color filter (3) The light (φ2) passing through each of the segments (3a), (3b), (3c)... Becomes light of a corresponding color, that is, red, green and blue, or white in addition thereto.
[0017]
The light (φ2) passing through each of the segments (3a) (3b) (3c)... Of the color filter (3) is reflected by the surface of the optical element (4) and is projected by a projection lens system (6) on a screen (6). An image is created in 7). At this time, the light (φ3) reflected on the surface of the optical element (4) is an optical element driving device (14) that receives video information from the video input section (13). Is modulated according to the video information supplied to the optical element (4).
[0018]
At this time, there is a change in the light (φ1) emitted from the high-pressure discharge lamp (1) due to the superposition of the pulse current (P) as described above. The change of φ2) is corrected and modulated, and the disturbance of the gradation is suppressed to the minimum. This point will be further described.
[0019]
FIG. 2 shows the waveform of the DC lamp current (R) on which the pulse current (P) is superimposed and the waveform of the light (φ1) applied to the color filter (3). The synchronizing signal (S) from the color filter (3) is input to the DC lighting means (5), and the DC lamp current (R) superimposed with the pulse current (P) in synchronism with the synchronizing signal (S) is discharged at a high voltage. It is supplied to an electric light (1).
[0020]
When the lamp current (R) is DC, there is no polarity switching after the superposition of the pulse current (P), so that the light flux change waveform basically appears as a simple waveform without undershoot (U). Therefore, the pulse current (P) is superimposed on the DC lamp current (R) in synchronization with the required color segments (3a) (3b) (3c)... Of the color filter (3) built in the projection type system. At the same time, the light flux change caused by the superposition of the pulse current (P) is corrected and controlled by the DMD, and the required color balance is obtained by reflecting the light subjected to the correction control. Since the light beam waveform is simple and has periodic reproducibility, the projection type system using the DMD is unlikely to cause gradation dropout. In particular, even when inserting the color segment (3a) other than white into a red color segment (3a), the effect is small.
[0021]
FIG. 4 is a diagram showing the state of electrodes and arcs at a DC lamp current (R). Unlike a conventional AC lamp, a DC lamp (1) is different between electrodes (1a) and (1b) in a lamp. The electron emission direction is always constant, and the bright spot (K) of the arc (A) is basically fixed if the arc (A) is stable. In such a state, the luminous flux (φ1) applied to the color filter (3) in combination with the reflector (2) is always constant. Therefore, in the projection type system using the DMD (4), there is no gradation dropout peculiar to AC lighting.
[0022]
Note that the color segment (3a)... On which the pulse current (P) is superimposed in synchronization is generally put in the white segment (3d) in the case of a business projector. This is advantageous in that it has the least effect on the gradation and that the illuminance of the video can be improved. On the other hand, in the case of a home theater projector, the color tone of an image is regarded as important, so that a color filter (3) using three color segments (3a) of red, green, and blue without a white segment (3d) is used. General. In this case, generally, the pulse current (P) is superposed on the red segment (3a). This is because the spectral characteristics of the high-pressure discharge lamp (1) usually have a shortage of the red component, so that a well-balanced color adjustment can be performed by enhancing the luminous flux passing through the red segment (3a) with the pulse current (P). It is.
[0023]
In some cases, pulse currents (P) having different pulse widths may be synchronously superimposed on two places, for example, white and green segments (3d) and (3b). This is because, unlike the AC lighting, the DC lighting does not need to worry about the switching of the polarity, and therefore the pulse current (P) can be superimposed and arranged at an arbitrary position and with an arbitrary width, since the superposition arrangement of the pulse current (P) is flexible.
[0024]
FIG. 2 shows an example in which the pulse current (P) is superimposed in synchronization with a specific segment. When the segment to be superimposed is the white segment (3d), the occupation rate of the white segment (3d) is typically 11% of one rotation of the color filter (3). About 40 degrees. When the rotation speed of the color filter (3) is 120 Hz, the maximum pulse width (tp) that can be superimposed on the white segment (3d) can be calculated as follows:
(Tp) = (ts) × (40 degrees / 360 degrees)-----(Equation 1)
Here, (ts) is a pulse cycle, and (ts) = 1/120 Hz.
Thus, the maximum pulse width (tp) that can be superimposed on the white segment (3d) is 0.9 msec.
[0025]
Next, regarding the power of the pulse current (P) superimposed on the DC lamp current (R), the pulse superimposed power supplied to the high-pressure discharge lamp (1) is equal to the rated power of the high-pressure discharge lamp (1). It is preferably at least 1%. By superimposing such a relatively small pulse current (P) on the DC lamp current (R), the arc jump can be suppressed remarkably and has an immediate effect. Although the mechanism is not always clear at this time, the temperature of the current arc spot, which is the starting point of the arc, is periodically increased by the superimposed pulse power, and the temperature at the current arc spot before moving to another spot is increased. It is considered that the electron emission was improved, and as a result, the stability of the arc was improved.
[0026]
As a result of the experiment, if the pulse superimposed power supplied to the high-pressure discharge lamp (1) is 1% of the rated power of the high-pressure discharge lamp (1), the above-described flicker suppression effect caused by the arc jump can be sufficiently achieved. I understood. Preferably, it is 2 to 7% (in this case, flicker prevention can be almost surely achieved), and the maximum is 20%. When the pulse superimposed power is set to 20% or more of the rated power of the high-pressure discharge lamp (1), the pulse superimposed power becomes excessive with respect to the rated power, so that the main body is pulsed and DC lighting is no longer performed. As described above, according to the present invention, it is possible to stabilize the arc (A) with a relatively small pulse current (P), and it is possible to construct a projection-type system using the DMD with little effect on gradation. .
[0027]
In Japanese Patent Laid-Open Publication No. 10-501919, the flicker of the discharge arc (A) is superimposed by superimposing the pulse current (P) in the latter half of each half cycle (c1) (c2) of the AC rectangular lamp current (C). Is described. However, the lighting method in this case is an AC method and differs from the DC method as in the present invention in the lighting method, and therefore also in the mechanism for preventing flicker.
[0028]
That is, according to the experiments by the inventors, the superimposition effect of the pulse current (P) according to Japanese Patent Application Laid-Open No. H10-501919 is based on the flat surface (= spherical portion without irregularities) at the tip of the AC electrodes (1a ′) and (1b ′). Alternatively, a prominent projection appears on the flat part), which becomes an arc spot, and the arc generation position is fixed, thereby stabilizing the arc (A). The time until such appropriate protrusions are formed is 20 minutes to 2 hours, depending on the shape of the AC electrodes (1a ') and (1b'). In addition, the lamp voltage once showed a remarkable decreasing tendency (5 to 20 V) from the initial stage due to the projection.
[0029]
On the other hand, in the DC lighting according to the present invention, the pulse current (P) superimposed on the DC lamp current (R) even if the electrode tip is worn and deteriorated and the flat part increases at the electrode tip. As a result, the arc (A) is stably generated from one arc spot after several tens of seconds without a remarkable projection appearing at the electrode tip. Further, the tendency of the voltage drop is basically not observed, and even if the variation occurs, it is within 5 V. Therefore, the method of superimposing the pulse current (P) on the DC lamp current (R) of the present invention is It can be said that the mechanism is completely different from that of Tokuhei 10-501919.
[0030]
Next, the pulse current superposition condition will be discussed. The repetition period (ts) of the pulse current (P) is in the range of 0.2 msec to 20 msec (the reason will be described later), and the pulse peak value is the average pulse height of the pulse current (P) with respect to the average current value (Io) of the lamp current. The ratio (Ip / Io) of (Ip) is in the range of 0.1 to 2 (the reason will be described later), and the execution pulse width (tp) of the pulse current (P) with respect to the repetition period (ts) of the pulse current (P) The ratio (tp / ts) was in the range of 0.005 to 0.5 (the reason will be described later).
[0031]
FIG. 2 shows an example of the pulse current waveform. When the pulse current (P) is superimposed on the white segment (3d), the following values are obtained by applying (Expression 1) obtained under the conditions of the color filter (3). Is derived.
Repetition period (ts) of pulse current (P) = 8.3 msec
Execution pulse width (tp) of pulse current (P) = 0.9 msec
(Tp / ts) = 0.108
Here, (Ip / Io) = 0.2 is selected as the pulse peak value.
According to experiments by the inventors, when (Ip / Io) <0.1, almost no arc jump suppression effect is observed. In the case of 0.1 <(Ip / Io) <0.2, the effect of suppressing the arc jump can be seen but is not sufficient, and the arc jump remains. When (Ip / Io)> 0.2, the arc jump suppression effect was large. Therefore, (Ip / Io) = 0.2 is adopted here as a typical example as the minimum value at which the arc jump suppression effect becomes significant.
Ratio of pulse superimposed power (Wp) to rated power (Wo) (Wp / Wo) = (Ip / Io) × (tp / ts), that is, in this example, the ratio (Wp / Wo) = 0.2 × 0 .108 = 0.0216, which is about 2%. The repetition period (ts) of the pulse current was selected from the range of 0.2 msec to 20 msec.
[0032]
When the repetition period (ts) of the pulse current (P) is equal to or longer than 20 msec, the pulse superimposed component decreases, and the arc jump suppression effect decreases. The range in which the influence of acoustic resonance can be avoided is 5 kHz or less (= 1/5000). If this is set as the repetition period (ts) of the pulse current, it becomes 0.2 msec (= 1/5000) to 20 msec (= 1/50). That is, by setting the repetition period of the pulse current to 0.2 msec to 20 msec, the influence of acoustic resonance can be avoided even when the pulse current is superimposed on the DC current, the arc jump suppression effect can be maintained, and the image is adversely affected. Can not be.
[0033]
Further, the ratio of the average pulse height (Ip / Io) of the pulse current (P) to the average current value (Io) of the DC lamp current (R) is set to 0.1 or more. This is because the arc jump suppression effect is sharply reduced due to being too small. When the average pulse height ratio (Ip / Io) is 2 or more, the operating current of the lighting device becomes too large. Therefore, by setting the average pulse height ratio (Ip / Io) of the pulse current to the average current value (Io) of the lamp current to be 0.1 to 2, steady lighting without arc jump can be achieved.
[0034]
Further, the minimum value (0.005) of the ratio (tp / ts) of the effective pulse width (tp) of the pulse current (P) to the repetition period (ts) of the pulse current (P) is as follows. The minimum value of the pulse width (tp) in the case of the maximum of 20 msec (this pulse width (tp) corresponds to the minimum value achievable from the degree of response of the lighting device) is (tp) = 0.1 msec. Therefore, it is derived from 0.1 msec / 20 msec). Conversely, assuming that the average pulse height ratio (Ip / Io) is the maximum of 2, the pulse superposition power is (Wp / Wo) = 0.01, that is, 1%. Here, (Wp / Wo) = (Ip / Io) × (tp / ts). On the other hand, the maximum value is effective up to a maximum duty 0.5 of the pulse superimposed current.
[0035]
As described above, by setting the pulse current condition to be superimposed so as to satisfy the above three conditions, it is possible to reliably suppress the arc jump without affecting the image of the optical system.
[0036]
【The invention's effect】
As described above, according to the present invention, a lighting method for a high-pressure discharge lamp, in which a pulse current is superimposed on a DC lamp current to stably maintain an arc of the high-pressure discharge lamp and suppress an arc jump, is applied. Then, by superimposing the pulse current in synchronization with at least one specific color segment of the color filter of the projection type system, it is possible to provide an optimal projection type system capable of minimizing gradation disturbance.
[Brief description of the drawings]
FIG. 1 is a block diagram of the present invention; FIG. 2 is a drawing showing a relationship between a current waveform of a pulse current superimposed DC lamp current of the present invention and light emitted from a discharge lamp; FIG. Drawing showing the relationship between the current waveform of the lamp current and the light emitted from the discharge lamp. FIG. 4 is a front view showing the state of the occurrence of arcs and bright spots during DC lighting. Front view showing the situation of occurrence
(E) Light source (R) DC lamp current (P) Pulse current (Φ) Light emitted from light source (1) High-pressure discharge lamp (2) Reflector (3) Color filter (3a) ( 3b) (3c) (3d) ... color segment (4) ... optical element (DMD)
(5) DC lighting means (6) Projection lens system (7) Screen

Claims (7)

A method of operating a projection type system for projecting an image on a screen by sequentially passing light emitted from a DC-lit high-pressure discharge lamp through color segments obtained by dividing a color filter into a plurality of colors, comprising at least one specific color segment. Wherein a pulse current is superimposed on a DC lamp current of the high pressure discharge lamp in synchronization with the operation of the projection type system. A projection system in which light emitted from a high-pressure discharge lamp is sequentially passed through color segments obtained by dividing a color filter into a plurality of parts to project an image on a screen. DC lighting means for supplying and periodically superimposing a pulse current on the DC lamp current for lighting, wherein the pulse current is superimposed in synchronization with at least one specific color filter. And projection type system. 3. The projection type system according to claim 1, wherein the color filters are formed in divided segments formed by color-dividing a rotatable color wheel. The color filter according to any one of claims 1 to 3, wherein the color filter is composed of four color segments of red, green, blue, and white, and the pulse current is superimposed within a white segment. Projection type system and its operation method. The projection according to any one of claims 1 to 3, wherein the color filter is formed of three segments of red, green, and blue, and the pulse current is superimposed within a range of the red segment. The mold system and how it works. The projection type system according to any one of claims 1 to 5, wherein the pulse superimposed power supplied to the high pressure discharge lamp is 1% or more of the rated power of the high pressure discharge lamp. The pulse current superimposed on the high-pressure discharge lamp has a repetition period (ts) of the pulse current in a range of 0.2 msec to 20 msec,
The ratio (Ip / Io) of the average pulse height (Ip) of the pulse current to the average current value (Io) of the lamp current is in the range of 0.1 to 2,
The ratio (tp / ts) of the pulse width (tp) of the pulse current to the repetition period (ts) of the lamp current is in the range of 0.005 to 0.5. The projection-type system as described and the method of operation thereof.

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