JP2007047234A - Projection type system by high pressure discharge lamp of dc lighting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection type system designed such that various color tones are freely adjusted according to the taste of a user and high image quality is ensured. <P>SOLUTION: The projection type system includes: a light source E; a rotating type color filer 3; a reflection type optical element 4 for gradation and modulation based on a video signal; a DC lighting means 5; and a projection lens system 6. In the projection type system, a pulse circuit generates a synchronous signal S that includes a plurality of on/off patterns synchronized with the rotating speed of the color filter and the optical element. According to the on/off patterns, a pulse current having one of the current intensities selected from a group consisting of (1) first negative pulse, (2) second negative pulse, and (3) positive pulse is applied so as to overlap a DC current after a specific time (TO) has elapsed from the time of rise of the synchronous signal as a reference. While the first or second negative pulse and the positive pulse correspond to time at least one or more color segments, they are separately applied. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a projection type system (projection type image display system) equipped with an optical element and a color filter.

  The projection type system irradiates light to a color filter that rotates at high speed to extract, for example, three primary colors (that is, R (red), G (green), and B (blue)) in a time-sharing manner. DMD (registered trademark)] is a system that creates an image pattern using a reflective optical element and projects a color image on a screen via a projection lens system, and is used in home theaters and RPTVs (rear projection televisions) Has been.

  Early color filters mainly consisted of three primary colors such as R, G, B, R, G, and B, but in recent years, B, C, G, Y, R, and M In addition, color filters including intermediate color segments such as cyan C (intermediate color between blue and green), yellow Y (intermediate color between green and red), and magenta M (intermediate color between red and blue) have been proposed.

  When an intermediate color is expressed by using a projection system having only three primary colors, the intermediate color tends to be dark overall because it is formed by combining a plurality of primary colors. However, the use of an intermediate color segment has an advantage that a desired vivid color tone can be easily obtained without reducing brightness. Data has also been reported that the use of an intermediate color can make the brightness about 1.5 times brighter than when the primary colors are combined. In this way, efforts are being made to realize various color expressions in accordance with user preferences.

  By the way, in a projection type system using a DC lighting high pressure discharge lamp, as a technique for improving the image quality, a positive rectangular pulse current (hereinafter referred to as “superposition”) is superimposed on the current of the high pressure discharge lamp at a predetermined timing in synchronization with the rotation of the color filter. In this specification, a technique of applying a “positive pulse”) has been proposed (see Patent Document 1).

  For example, FIG. 3 shows a lamp current drive waveform in which the synchronization signal is controlled so as to apply a positive pulse in synchronization with the red segment. When a positive pulse with a certain intensity or more is applied, flicker caused by arc jump of the high-pressure discharge lamp can be suppressed, and the color temperature can be adjusted (in this case, red is emphasized).

  On the other hand, a method has been proposed in which a negative rectangular pulse current (hereinafter referred to as “negative pulse” in this specification) is applied to compensate for the number of gradations (bits) of a specific color.

  Thus, by applying a predetermined pulse, it is possible to express a color tone with higher image quality than before.

JP 2004-212890 A

  In the case of applying both a negative pulse and a positive pulse in one system, the following problems may occur.

(1) Problem of life deterioration of high-pressure discharge lamp When negative pulse and positive pulse are applied continuously, the instantaneous power drop increases. As a result, the electrodes (for example, tungsten electrodes) of the high pressure discharge lamp are easily consumed, and the life of the high pressure discharge lamp is shortened. In particular, the negative pulse is thought to deteriorate the electrode of the high-pressure discharge lamp, but the electrode is more likely to deteriorate when the positive pulse is applied subsequently to the negative pulse than when only the negative pulse is applied. Possible (first problem).

(2) Problem of image quality degradation When both negative and positive pulses are applied, the rising current transient characteristic occurs for two negative and positive pulses. As a result, the time of excessive characteristics becomes long, so that the image quality is likely to be disturbed (second problem).

  As described above, the application of the negative pulse and the positive pulse has their respective merits in improving the image quality. However, when both are applied, the above-described problems may occur. In other words, if the degree of freedom of pulse arrangement is too large, there may be adverse effects. In order to solve this problem, a technique for accurately controlling the timing of applying pulses (arrangement of pulses) is required.

  An object of the present invention is to provide a projection system capable of freely adjusting various color tones according to user's preference and having higher image quality than before, and a synchronization signal applying method for realizing the same. Providing is the main technical issue.

The projection type system according to the present invention includes a light source E, a rotary color filter 3 that is divided into a plurality of color segments that time-divides the light flux Φ1 emitted from the light source into a plurality of colors, and passes through the color filter. A reflection type optical element 4 that performs gradation and modulation with a video signal, a direct current power supply circuit that generates a direct current that drives the light source, and a pulse current that is superimposed on the direct current power supply circuit. A projection type system including a direct current lighting means 5 including a pulse circuit and a projection lens system 6 for projecting a light flux Φ3 reflected by the optical element onto a screen;
The pulse circuit generates a synchronization signal S composed of a plurality of on / off patterns synchronized with the rotation speed of the color filter and the optical element, and according to the on / off pattern,
(1) The first negative pulse (2) The second negative pulse (3) After the pulse current having any one of the positive pulses has passed for a certain time T0 with respect to the rising time of the synchronizing signal, The first and second negative pulses and the positive pulse are separately applied for a time corresponding to at least one color segment while being applied while being superimposed on a direct current. .

  More specifically, the color arrangement order of the color filters is selected so that the color segment to which the negative pulse is applied and the color segment to which the positive pulse is applied are not continuous. When the color arrangement order of the color segments has already been determined, the negative pulse and the positive pulse may not be continuously applied to two consecutive color segments.

  Here, the first and second negative pulses are two types of negative pulses having different sizes. For example, when the first negative pulse is applied in a superimposed manner, the current value is reduced to approximately 50% of the steady value for a certain period of time. When the second negative pulse is applied in a superimposed manner, the current value is preferably reduced to approximately 25% of the steady value for a certain time. Since the light intensity of the high-pressure discharge lamp used for the light source is normally nonlinear with respect to the current value, the magnitude of the negative pulse may be determined in consideration of the light output.

  When two negative pulses are combined in this way, the number of bits of DMD (registered trademark) can be equivalently increased by 1 to 2 bits. Further, when a positive pulse is applied, flicker caused by arc jump of the high-pressure discharge lamp can be suppressed, and color temperature adjustment can be performed by emphasizing a predetermined color segment.

  Furthermore, in the present invention, the “first or second negative pulse” and the “positive pulse” are separately applied for a time corresponding to at least one color segment. The drop in instantaneous power applied locally to the tip is reduced. As a result, the electrodes of the high-pressure discharge lamp are not easily consumed.

  Even if the applied pulses are of different types ((1) to (3)), the pulse application start time is made to coincide after a certain time (T0) has elapsed since the rising edge of the synchronization signal. As a result, the timing fluctuation of the excessive characteristic is suppressed to the minimum, so that the image quality is hardly disturbed.

  By the way, when a plurality of different types of pulses are used in combination as described above, it is necessary to identify in advance the types of pulses ((1) to (3)) to be sent after a predetermined time from the rising edge of the synchronization signal. In order to make this possible, it is preferable to change the ON time of the synchronization signal S within the certain time (T0). In this way, the first negative pulse, the second negative pulse, and the positive pulse can be identified. That is, when the ON time and the type of pulse are associated in advance, for example, when there is an ON time of Ts1 seconds, the first negative pulse is emitted T0 seconds after the rising time of the synchronization signal, and the ON time of Ts2 seconds. It is defined that the second negative pulse is emitted T0 seconds after the rising time of the synchronizing signal when there is, and the positive pulse is emitted T0 seconds after the rising time of the synchronizing signal when the ON time is Ts3 seconds. Just keep it.

  Furthermore, the falling time of the positive pulse is preferably synchronized with the falling time of the color segment. In this way, the rising time and falling time of the positive pulse and the rising time of the negative pulse are arranged within the spoke time. In the present specification, “spoke time” means a blank time at the boundary of a color segment.

  In this way, the excessive current due to the rising and falling of the positive pulse or the rising of the negative pulse is finished within the spoke time. For this reason, the image quality is less likely to be disturbed. The spoke time may be as small as necessary. For this reason, the brightness does not decrease even though the image quality is less disturbed.

  The light source of the projection type system in the present invention is preferably a high pressure discharge lamp driven by a direct current. This is because a high-pressure discharge lamp driven by an alternating current frequently changes polarity, so that it is difficult to control the timing of applying a pulse.

  The projection type system according to the present invention can easily identify the first negative pulse, the second negative pulse, and the positive pulse by changing the on-time within the predetermined time T0.

  According to the present invention, it is possible to arrange a pulse (negative pulse or positive pulse) with an extremely high accuracy for an arbitrary color segment. As a result, while minimizing image quality disturbance, negative pulses can be applied to compensate for the gradation power of colors that are difficult to represent, such as green, to reduce dither noise, or positive pulses can be applied to flicker caused by arc jumps. The color temperature can be adjusted according to the purpose.

(Embodiment)
FIG. 1 shows an example of a block diagram showing a system configuration diagram of a projection type system according to the present invention. This system includes a light source E including a high pressure discharge lamp 1 and a reflector 2, a color filter 3, an optical element 4, and a projection lens system 6. The light flux Φ1 irradiated from the high-pressure discharge lamp 1 is reflected by the reflector 2 and irradiated to the color filter 3, and after being optically modulated by the optical element 4, a predetermined image pattern is projected onto the screen 7 via the projection lens system 6. Is done.

  The color filter is a plurality of color segments formed of a dichroic filter having a property of selectively passing visible light wavelengths. The color filter 3 in FIG. 1 includes six colors of B, C, G, Y, R, and M (blue, cyan, green, yellow, red, and magenta) (3a to 3f).

  The optical element 4 is formed of a reflection type light modulation element such as DMD (registered trademark), reflects the light Φ2 separated through the color segments 3a to 3f, and supplied from the optical element driving device 14. Optical modulation is performed using a video signal (for example, a video signal).

  DMD (registered trademark) is an optical element (light modulation element) for giving gradation to the light of each segment that has passed through the color filter, and for modulating the image signal, for example, on a semiconductor memory cell. A large number of mirror elements are attached. The inclination of each mirror element can be controlled by an optical element driving device, and a predetermined pattern can be created by switching light transmission and blocking or deflection of each mirror.

  The DC lighting means 5 is a device that incorporates a DC power supply circuit and a pulse circuit and supplies a lamp current for lighting the high-pressure discharge lamp 1. This apparatus can superimpose and apply a predetermined pulse to a direct current at a predetermined timing. Details of the drive current pattern to the high pressure discharge lamp will be described later.

  The projection lens system 6 is an optical lens for projecting the light (Φ3) reflected by the surface of the optical element 4 onto the screen 7.

  The color filter driving device 8 is a driving device for rotating the color filter 3 and functions to rotate the color filter 3 at a constant speed. For example, in the case of a video signal with a frequency of 60 Hz (one screen changes at 60 times per second), the color filter 3 rotates at a speed that is an integral multiple of the frequency of the one frame (for example, four times, that is, a frequency of 240 Hz) To do.

  When the light beam Φ1 emitted from the light source E passes through the segments 3a to 3f of the color filter 3 rotating at a constant speed, color separation is performed in a time-sharing manner, and the light Φ2 separated into the respective colors is The light enters the optical element 4 through a light pipe (not shown) or the like.

-Current drive pattern-
FIG. 2 shows an example of the state of the color filter segment, the DC lamp current waveform A, and the waveform of the synchronization signal S in the projection type system according to the present invention. Here, an example is shown in which a color filter including six segments B, C, G, Y, R, and M as shown in FIG. 1 is rotated at a quadruple speed of the frequency of one frame.

  The 100% line in the lamp current waveform A in the figure represents the magnitude of the direct current when no pulse is applied. (This current value is referred to as “steady value” for convenience.) When a positive pulse is applied here, the current value of the lamp current waveform A becomes larger than the steady value, and when a negative pulse is applied, it becomes smaller than the steady value.

  The first negative pulse is arranged in the first rotation green segment (G), and the second negative pulse is arranged in the second rotation green segment (G), so that the number of bits of DMD (registered trademark) is equivalently 2 A bit can be increased. One subframe is formed by two rotations, and one frame is formed by four rotations that is twice as much.

  Timing 1 in FIG. 2 indicates that a negative pulse (first negative pulse) that reduces the current intensity to approximately 50% of the steady value is applied in the middle of the green segment (G) (second half timing). Timing-2 shows that a negative pulse (second negative pulse) for reducing the current intensity to approximately 25% of the steady value is applied in the middle of the green segment (G) (second half timing).

  That is, even with the same green color, the brightness and the like are different between the case where the first negative pulse is applied and the case where the second negative pulse is applied, and this makes it possible to express a color tone that was difficult to express in the past, such as dark green. Become.

  Timing-3 indicates that a positive pulse is applied in synchronization with the red segment (R), and timing-4 indicates that a positive pulse is applied in synchronization with cyan (C). This emphasizes red and cyan. Note that applying a positive pulse of 120% or more of the steady value also has the effect of suppressing arc jump (see the above-mentioned Patent Document 1).

  In the example of FIG. 2, a yellow segment having a steady current value is arranged after the green segment. The steady value of the current intensity means that neither a negative pulse nor a positive pulse is applied. In other words, the negative pulse and the positive pulse are arranged at a time apart from at least one color segment.

  In this way, the drop in the instantaneous power applied locally to the tip of the electrode of the high pressure discharge lamp is reduced. As a result, the electrodes of the high-pressure discharge lamp are not easily consumed. At this time, in the latter half of the green segment, only the rising current excessive characteristic of the negative pulse may be arranged in the spoke time.

-Timing control-
Next, pulse timing control will be described. The first negative pulse, the second negative pulse, and the positive pulse are applied by being superimposed on the direct current after a predetermined time T0 has elapsed with reference to the rising time of the synchronization signal S. As described above, by appropriately setting and adjusting the rising time of the synchronization signal, the current transient characteristics of the rising of the first negative pulse, the second negative pulse, and the positive pulse can be accurately arranged in the spoke time. , Image quality disturbance can be prevented.

Note that the fixed time T0 is set to be a fixed time for the sake of simplicity of explanation. However, like the first negative pulse (T0 _N1 ), the second negative pulse (T0 _N2 ), and the positive pulse (T0 _P ), respectively. Different fixed times may be set. The certain time here means at least “a certain time according to the type of pulse”.

  The reason for setting the fixed time T0 in this way is to make it easy to identify the type of the next pulse (first negative pulse, second negative pulse, and positive pulse). This is achieved by changing the on-time within T0.

For example, the rules are determined as follows.
(I) If the on-time Ts1 (= 100 μs, for example) is detected at timing-1, the first negative pulse is generated after the lapse of Td1.
(Ii) If an on-time Ts2 (= 50 μs, for example) is detected at timing-2, a second negative pulse is generated after Td2 has elapsed.
(Iii) At timing-3 and timing-4, if an on-time Ts3 (= 150 μs, for example) is detected, an immediate positive pulse is generated and the synchronization signal is kept on until the positive pulse is terminated.

  In this way, the type of the next incoming pulse can be identified.

  On the other hand, the end timing of the positive pulse is synchronized with the falling time of the color segment. In the example of FIG. 2, the falling time of the synchronization signal is made to coincide with the end timing of the red segment and the cyan segment, and the positive pulse is ended at a precise timing.

  As described above, by controlling the current drive pattern by controlling the timing of the synchronization signal, a pulse (negative pulse or positive pulse) can be arranged with high accuracy for any color segment. As a result, the rising and falling times of the positive pulse and the rising time of the negative pulse are arranged within the spoke time.

  As described above, according to the present invention, while suppressing image quality disturbance to a minimum, a negative pulse is applied to compensate for the gradation power of a color that is difficult to express such as green to reduce dither noise, or a positive pulse is applied. Thus, flicker caused by arc jump can be suppressed, and color temperature adjustment can be performed according to the purpose.

  Although the frame frequency has been described as 60 Hz, it is not limited to this and may be 50 Hz, for example. In that case, the synchronization signal may be 50 Hz which is the same as the frequency of the frame. Further, the rotation speed of the color filter is not limited to 4 × speed, but can be applied to 2 × speed, 3 × speed, and the like by changing the synchronization signal.

  The operation method of the projection type system according to the present invention expresses a specific color by emphasizing a pulse current application pattern, or reduces the dither noise (vibration noise) by increasing the number of bits of the specific color. When the image quality is high, the industrial applicability is extremely high as a technology that can achieve high image quality without image quality disturbance and can dramatically improve the image quality of projectors and rear projection televisions.

Block diagram of the present invention The figure which shows the relationship between the lamp current waveform of this invention, and a synchronizing signal The figure which shows the relationship between the lamp current waveform of a prior art example, and a synchronizing signal

Explanation of symbols

A DC lamp current E Light source S Sync signal φ Light (beam)
DESCRIPTION OF SYMBOLS 1 High pressure discharge lamp 2 Reflector 3 Color filter 3a-3f Color segment 4 Optical element 5 DC lighting means 6 Projection lens system 7 Screen 8 Color filter drive device 13 Video input part 14 Optical element drive device

Claims (3)

A light source (E), a rotary color filter (3) divided into a plurality of color segments for time-dividing a light beam (Φ1) emitted from the light source into a plurality of colors, and a light beam ( Reflective optical element (4) that performs gradation and modulation by video signals, a DC power supply circuit that generates a DC current for driving the light source, and a pulse current that is superimposed on the DC power supply circuit A projection type system including a direct current lighting means (5) including a pulse circuit and a projection lens system (6) for projecting a light beam (Φ3) reflected by the optical element onto a screen,
The pulse circuit generates a synchronization signal (S) composed of a plurality of on / off patterns synchronized with the rotation speed of the color filter and the optical element, and according to the on / off pattern,
(1) First negative pulse (2) Second negative pulse (3) A pulse current having a current intensity of one of the positive pulses has passed for a fixed time (T0) with respect to the rise time of the synchronization signal. The first or second negative pulse and the positive pulse are separately applied for a time corresponding to at least one color segment, and are applied after being superimposed on the direct current. Projection type system. 2. The projection system according to claim 1, wherein the first negative pulse, the second negative pulse, and the positive pulse are identified based on an ON time of the synchronization signal S within the predetermined time (T0). 2. The projection system according to claim 1, wherein the falling time of the positive pulse is synchronized with the falling time of the color segment.

Images