JP2000214398A - Picture output device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an picture output device capable of controlling rotary drive of a micro mirror so as to make the flicker less noticeable. SOLUTION: In an picture output device using a micro mirror array, a first and a second micro mirror are each driven by a first and a second drive signal in which output order is different for the pulse formed by modulating the pulse width in accordance with a picture signal level. As a result, the irradiation time of light is dispersed, making the flicker less noticeable. In addition, the first and the second drive signal are each made to be a signal consisting of one pulse having a width in accordance with the picture signal level, thereby minimizing the number of times in the rotation of the micro mirror and reducing the ratio of false signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image output device using a micromirror array, and more particularly, to an image output device capable of reducing flicker.

[0002]

2. Description of the Related Art FIG. 10 is an explanatory diagram of an image output device using a micro mirror array. The micromirror array is configured by integrating hundreds of thousands of micromirrors. First, the operation of a single micromirror array will be described.

In FIG. 10A, light from a light source 10 passes through an illumination system lens 14 and enters an optical rotary filter 11. The optical rotation filter 11 is, for example, a disk having three filter regions of red (R), green (G), and blue (B), each of which forms a fan shape, and has a cycle three times the cycle of a normal video signal. To rotate in the direction of arrow 15. Therefore, the light that has passed through the optical rotation filter 11 changes to red, green, and blue for each vertical cycle of the video signal, and irradiates the micromirror M1.

The angle of the micromirror M 1 is controlled by the drive unit 12, and reflects the light from the light source 10 in the direction of the projection lens 13 at an angle θ 1 with the optical path L. On the other hand, when the angle is θ2 as shown in FIG.
Light from the light source 10 is not reflected in the direction of the projection lens 13.

In FIG. 10A, a micro mirror M
The light reflected by 1 and passing through the projection lens 13 is projected on a screen or the like (not shown). Micro mirror M1
Corresponds to one pixel of the projected image, and an image of m × n pixels can be projected by a micromirror array in which m × n micromirrors arranged two-dimensionally are integrated.

[0006] The drive unit 12 receives an input video signal S10.
A drive signal S11 corresponding to the signal level of the micromirror M1 is generated, and the micromirror M1 is rotationally driven by electrostatic attraction. For example, when the drive signal S11 is at the H level, the angle of the micromirror M1 is set to the aforementioned θ1, and the drive signal S11 is set to the L level.
In the case of the level, the angle is set to θ2. This allows
The brightness of one pixel of the projected image can be switched according to the signal level of the video signal. The rotation angle, which is the difference between the angles θ1 and θ2, is about 20 degrees.

The gradation of one pixel is controlled by a drive signal S11 obtained by pulse-width-modulating the video signal S10. That is, if the H level time of the drive signal S11 is changed,
Since the amount of light projected on the screen changes, the gradation of the pixel corresponding to the macro mirror M1 according to the level of the video signal S10 can be controlled.

Further, in order to project a color image,
The red, green, and blue video signals S10 are sequentially input to the drive unit 12, and the optical rotation filter 11 is rotated in synchronization with the red, green, and blue video signals S10. That is, a color image is projected by irradiating the micromirror M1 with red, green, and blue light in a time-sharing manner in synchronization with controlling the angle of the micromirror M1 with the red, green, and blue video signals S10. be able to.

FIG. 11 shows a time chart of a drive signal S11 obtained by pulse-width-modulating a 3-bit video signal in order to display a projected image in eight gradations from 0 level to 7 level. In FIG. 11, one display field of the drive signal S11 is equally divided into seven, and the divided periods are numbered from 0 to 6.

[0010] Of the 3-bit digital value of the video signal S10, the lowermost digit (referred to as LSB (Least Significant Bit)) is a value indicating the level for one period, which is the sixth period, and the lower second digit. Is a value indicating the level for two periods of the fourth period and the fifth period, and the third digit (MSB (Most Significan
t Bit)) is a value indicating the level for four periods from the zero period to the third period.

Therefore, in FIG. 11A, when the digital value of the video signal S10 is (000), the drive signal S11 is at the L level during one display field, and the angle of the micromirror array moves in the screen direction. The angle θ2, which is not the projection direction, remains. From FIG. 11 (b) to (g)
During the period when the digital value of the video signal S10 is "1", the drive signal S11 is at the H level, and during that period, the angle of the micromirror array is switched to the angle θ1 in the projection direction on the screen. Then, FIG.
When the digital value of the video signal S10 is (111) as shown in FIG.
Level, and the angle of the micromirror array remains at the angle θ1, which is the projection direction to the screen direction.

As described above, the micromirror array is switched between the angles θ1 and θ2 and projects an image on the screen.
Or the time required to rotate from the angle θ2 to θ1 (hereinafter referred to as optical switching time) may adversely affect the projected image. That is, during this optical switching time, the micro-mirror array will be
The angle is other than 2, and the light reflected by the micromirror array during this period causes light of another display pixel, that is, a false signal, to be superimposed on one display pixel on the screen.

[0013]

In order to reduce such spurious signals, the present applicant has filed a driving method for minimizing the number of rotations of the micromirror in one display field filed on March 18, 1998. "Image output device" (Japanese Patent Application No. Hei 1)
0-67980). According to this, as shown in FIG. 2 of the above-mentioned application, the period of the H level in one display field of the drive signal is continuously supplied to the micromirror. A reduction in the signal ratio can be expected.

However, in such a method, although the ratio of the false signal can be reduced, in each micromirror, the time during which the light is irradiated on the screen during one display field is concentrated, and the period during which the light is irradiated is reduced. Since the non-irradiation time occurs alternately, a problem that flicker occurs occurs. In particular, when the display data is the same for all pixels or when one display field synchronization is long, flicker is easily noticeable.

Accordingly, it is an object of the present invention to provide an image output apparatus capable of controlling the rotation drive of a micro mirror so that flicker is not noticeable.

[0016]

In order to achieve the above object, in the image output apparatus of the present invention, adjacent micromirrors are rotationally driven based on mutually different drive signals.

For example, the configuration of the image output device of the present invention is as follows.
An image which outputs an image by a micro-mirror array having a plurality of micro-mirrors rotating between a first angular position for guiding light from a light source in a projection direction and a second angular position different from the first angular position In the output device, a pulse width modulated first drive signal is generated at predetermined intervals based on the level of the video signal having a predetermined period, and the first micromirror is output during the pulse output period of the first drive signal. A first driving unit for driving to one angle, and a second driving signal pulse-width-modulated based on the level of the video signal, and the output order of the pulses is opposite to the pulse output order of the first driving signal And a second drive unit that drives a second micromirror different from the first micromirror to a first angle during a pulse output period of the second drive signal. When That.

According to this configuration, different micro mirrors can be
Since driving is performed using a drive signal in which the output sequence of pulses generated by pulse width modulation according to the video signal level is different, the light irradiation time is dispersed, and flicker can be made inconspicuous.

Further, in the above configuration, the first drive unit and the second drive unit each include a first drive signal and a second drive signal each including one pulse having a width corresponding to the level of a video signal. Are generated at predetermined intervals.

Thus, the number of rotations of the micromirror is minimized, and the ratio of false signals can be reduced.

[0021]

Embodiments of the present invention will be described below. However, the technical scope of the present invention is not limited to the present embodiment. In the embodiment of the present invention, the drive signal, that is, the H level (pulse) period proposed in the above-mentioned application “Image Output Device” (Japanese Patent Application No. 10-67980) filed on Mar. 18, 1998 is used. From the 0th period, continuous according to each bit number,
In addition to the first drive signal in which the L-level period is continuously generated, first, the L-level period is continuously generated from the 0th period, and thereafter, the H-level period is continuously generated in accordance with the number of bits. A second drive signal is used.

FIG. 1 is a time chart of the first drive signal corresponding to the video signal quantized by 3 bits, and FIG. 2 is a time chart of the second drive signal similarly. . A configuration for generating both drive signals will be described later. Note that the video signal is not limited to a 3-bit digital signal, and may have a larger number of bits.

The switching of the angle of the micromirror during one display field by both drive signals is the minimum number of times 1
And a high-quality image with few false signal components can be projected. However, in the first drive signal and the second drive signal (H and L) which switch between the H level and the L level during one display field period, the 3-bit digital signal of the video signal is used. Even if the values are the same,
The H level (or the L level) in one display field is different. Specifically, the output order of the H level (pulse) is reversed. That is, in one display field, the first drive signal first outputs the H level and then outputs the L level, but the second drive signal outputs the L level first and then outputs the H level later. I do.

For example, as shown in FIGS. 1E and 2E, at time t1 in one display field,
The first drive signal (FIG. 1 (e)) is at the H level,
The second drive signal (FIG. 2E) is at the L level. At time t2, the first drive signal is at the L level, while the second drive signal is at the H level.

As described above, even if the driving signals correspond to the same digital value of the video signal, H
By using the first drive signal and the second drive signal whose levels are output in reverse order, flicker of the micromirror array can be suppressed as described in detail below. Specifically, in the micromirrors arranged in a matrix, adjacent micromirrors are rotationally driven based on different drive signals (that is, one is a first drive signal and the other is a second drive signal). You.

FIG. 3 is a diagram showing a state of each micro mirror in which an adjacent micro mirror is rotationally driven by different driving signals in a 4 × 4 micro mirror array as an example. 3 (a) and 3 (b) each show 1
It is a figure which shows the state of a micro mirror when the digital value of the video signal with respect to all the micro mirrors is (100) at the said time t1 and t2 in a display field, for example. In the figure, micromirrors surrounded by thin lines are driven by a first drive signal, and micromirrors surrounded by thick lines are driven by a second drive signal. The hatched micromirror indicates that the reflected light is not irradiated in the screen direction, that is, the mirror is at the position of the angle θ2, and the unshaded blank micromirror reflects the reflected light. It indicates a state of irradiation in the screen direction, that is, the position of the angle θ1.

In FIG. 3A, at time t1,
For example, the upper left micromirror M11 (thick and diagonal lines)
Are driven based on the second drive signal. Therefore, at time t1, the micromirror M11 is at the angle θ2,
The reflected light from the micromirror M11 is not irradiated on the screen. Then, the micromirror M21 (thin line & blank) on the right of the micromirror M11 is driven based on the first drive signal instead of the second drive signal. Therefore, at time t1, the micromirror M21 is at the angle θ1, and the light reflected from the micromirror M21 irradiates the screen. Then, the micromirror M31 on the further right is driven based on the second drive signal, and the micromirror M41 on the right is driven based on the first drive signal.

Further, the micromirror M12 on the lower side of the micromirror M11 is driven by the first drive signal, and the micromirror M22 on the right side thereof is driven by the second drive signal.

In FIG. 3B, the second drive signal for driving the micromirror M11 is at the H level at the time t2, so that the micromirror M11 is at the position of the angle θ1, and The reflected light is applied to the screen. Also, the micro mirror M
The first drive signal for driving the drive signal 21 at time t2
Since it is at the L level, the micromirror M21 is at the position of the angle θ2, and the light reflected from the micromirror M21 is not irradiated on the screen. Similarly, at time t2, the micromirror M31 is at the position of the angle θ1, and the micromirror M41 is at the position of the angle θ2. further,
Micro mirror M1 driven by first drive signal
2 is at the position of the angle θ2, and the micromirror M22 driven by the second drive signal is at the position of the angle θ1.

As described above, one of two adjacent micromirrors is driven based on the first drive signal, and the other is driven based on the second drive signal, whereby one display field is provided for each micromirror. The time to become the angle θ1 during the period is shifted. Thereby, the time during which light is irradiated on the screen is dispersed in one display field, so that flicker can be reduced.

FIG. 4 is a diagram showing a state of each micro mirror in a 4 × 4 micro mirror array, for example, when all the micro mirrors are driven only by the second drive signal as in FIG. In FIG. 4, the time when the light is irradiated on the screen is the time t1 in one display field.
At the time t2, no light is irradiated on the screen. On the other hand, in FIG. 3, as described above,
Since the time at which the light is applied to the screen is dispersed, the light is applied to the screen even at times t1 and t2, so that flicker is reduced and becomes inconspicuous, as is apparent from comparison with FIG.

FIG. 5 is a block diagram of the image output apparatus according to the embodiment of the present invention. In FIG. 5, as an example, four micromirrors M1 arranged in parallel
A case where a micromirror array MA composed of 1, M21, M31, and M41 is used will be described.

The light from the light source 10 is applied to an illumination system lens 14,
Each of the micromirrors M11, 21, 31, 4 in the micromirror array MA passes through the optical rotation filter 11.
Irradiate 1. Micro mirror M11, 21, 31, 4
1 denotes driving units 12a, 12b, 12c, and 12d, respectively.
, The angle is rotationally driven to either the angle θ1 or θ2. The video signal S1 is input to the distribution circuit 20, and the distribution circuit 20 applies S1a to S1d to the video signals corresponding to each micromirror to the driving units 12a to 12d, respectively.
Output to

When the micromirror is at the angle θ1, the micromirror reflects light from the light source 10 in the direction of the projection lens 13. The light transmitted through the projection lens 13 is applied to the screen 25 and the like. On the other hand, when the micromirror has the angle θ2, the micromirror does not reflect the light from the light source 10 toward the projection lens 13 and does not irradiate the screen with the light.

In the embodiment of the present invention, the drive signal generated by the drive unit 12 for each micro mirror is different for each adjacent micro mirror. For example, the driving unit 12a
And 12c drive micromirrors M11 and M31, respectively, with a first drive signal, and drive units 12b, 12d drive micromirrors M21, M41, respectively, with a second drive signal.

Next, a driving unit 1 for generating a first driving signal
The configurations of 2a and 12c (hereinafter, referred to as a first driving unit 12A) and the driving units 12b and 12d that generate a second driving signal (hereinafter, referred to as a second driving unit 12B) will be described.

FIG. 6 is a block diagram of the first drive section 12A. Here, for simplicity, it is assumed that the video signal is a 3-bit digital signal. In FIG. 6, the first driving unit 12A includes a magnitude comparator 121 and a seven-digit counter 122, and further includes an
A D circuit 123 may be provided. A clock having 1/7 cycle of one display field is input to the counter 122. In general, when the number of bits of a video signal is n bits, the clock cycle is 1 / (2 ⁿ -1) of one display field, and the counter 122 counts in (2 ⁿ -1). It is a counter.

The counter 122 counts with a clock and is reset by a reset signal input for each display field. That is, the counter 12
2 counts from “0” to “6” for each display field. The counter value of the output signal S2 from the counter 122 is input to the B terminal of the magnitude comparator 121. Further, a 3-bit digital value of the video signal S1 is input to the A terminal of the magnitude comparator 121. The magnitude comparator 121 compares the values input to both terminals, and outputs a signal S3 which becomes H level only when B terminal input counter value <A terminal input digital value.

FIG. 8A is a diagram showing the relationship between the output signal S2 of the counter 121 and the output signal S3 of the magnitude comparator 122 in the first drive section 12A. For example, if the digital value of the video signal S1 is (011) =
In the case of 3, the magnitude comparator 121
The H level is output until the counter value input to the B terminal of the magnitude comparator 121 reaches 2, and the L level is output when the digital value becomes 3 or more. Thus, the first drive signal S3 as shown in FIG. 1 is generated.

The first drive signal S3 is input to the AND circuit 123 as needed. A blanking signal is also input to the AND circuit 123. Thus, the output signal from the AND circuit 123 may be supplied to the micro mirror as the first drive signal S3 '.

The AND circuit 123 is provided to prevent the drive signal from going high during the blanking period. That is, during the blanking period, since no image is displayed, the driving signal is at the H level during that period, and the reflected light of the micromirror is prevented from being irradiated on the screen.

FIG. 7 is a block diagram of the second drive unit 12B. As in FIG. 6, the video signal is assumed to be a 3-bit digital signal. In FIG. 7, the second drive unit 12B
Has a magnitude comparator 121 and a seven-digit counter 122, and furthermore, an AND circuit 12
3 are provided. A clock having 1/7 cycle of one display field period is input to the counter 122. Then, the counter 122 counts by a clock and is reset by a reset signal every display field. The counter value of the output signal S2 from the counter 122 is input to the B terminal of the magnitude comparator 121. The 3-bit digital value of the video signal S1 is input to the A terminal of the magnitude comparator 121 and is input to the load terminal of the counter 122. That is, the counter 122 loads the digital value of the video signal into the load terminal, triggered by the reset signal, and starts counting up from the loaded digital value.
Therefore, for example, when a video signal having a digital value (100) = 4 is loaded, the counter 122 counts up from “4”, returns to “0” at the next clock when counts up to “6”, and returns to “3”. To ".

Then, the magnitude comparator 12
As in the case of FIG. 6, 1 compares the values input to both terminals and outputs a signal S4 which becomes H level when the B terminal input counter value <A terminal input digital value.

FIG. 8B is a diagram showing the relationship between the output of the counter 121 and the output of the magnitude comparator 122 in the second drive section 12B. For example, when the 3-bit digital value of the video signal is loaded with (011) = 3, the counter 122 starts counting up from “3”, so the magnitude comparator 121
The counter value input to the B terminal is changed from “3” to “6”.
Until the digital value returns to “0” and counts “2”, and then the H level is output. Thus, the second drive signal S4 as shown in FIG. 2 is generated.

The second drive signal S4 is input to an AND circuit 123 similar to that shown in FIG.
A blanking signal is also input to the ND circuit 123.
Thus, the output signal from the AND circuit 123 may be supplied to the micro mirror as the second drive signal S4 '.

Note that, even if the counter 122 of FIG. 7 loads the maximum count value (111) at the time of reset and counts down in response to the clock instead of loading the video signal S1, the magnitude comparator 121
Can output the same drive signal S4 as in FIG.

FIG. 9 is a diagram showing a time chart of a drive signal in which the output sequence of the pulses generated by the conventional pulse width modulation is the reverse of that in FIG. That is, in FIG. 9, when a 3-bit video signal is subjected to pulse width modulation, the lower first digit (LSB) of the digital value of the video signal corresponds to the level of the 0th period of the drive signal, and the lower two digits. The eyes correspond to the levels of the drive signal in the first period and the second period, and the third digit (MSB) corresponds to the levels of four periods from the third period to the sixth period.

That is, in FIG.
In the case of FIG. 11 described above, the pulse width is modulated in the order of MSB to LSB.
Also in this case, the output order of the pulses of the drive signal is reversed. Accordingly, similarly to the above-described embodiment, the generation of flicker can be suppressed by supplying the driving signal corresponding to FIG. 9 and the driving signal corresponding to FIG. 11 to each adjacent micro mirror.

In the above-described embodiment, the above-mentioned different drive signals are supplied to every other one of the plurality of micromirrors in a matrix. However, the present invention is not limited to this.
A different drive signal may be supplied every other or every other number.

[0050]

As described above, according to the image output apparatus of the present invention,
In a plurality of micromirrors arranged in a matrix, adjacent micromirrors are driven by driving signals in which the output order of pulses generated by pulse width modulation according to the video signal level is different, so that the light irradiation time is It is dispersed and can make flicker less noticeable.

[Brief description of the drawings]

FIG. 1 is a time chart of a first drive signal corresponding to a level of a video signal.

FIG. 2 is a time chart of a second drive signal corresponding to a level of a video signal.

FIG. 3 is a diagram showing an example of a state of each micromirror in which a neighboring micromirror is rotationally driven by a different drive signal in a 4 × 4 micromirror array.

FIG. 4 is a diagram showing a state of each micro mirror when all micro mirrors are driven only by a second drive signal.

FIG. 5 is a block diagram of an image output device according to an embodiment of the present invention.

FIG. 6 is a block diagram of a first driving unit 12A.

FIG. 7 is a block diagram of a second driving unit 12B.

FIG. 8 is a diagram showing a relationship between an output of a counter 121 and an output of a magnitude comparator 122.

FIG. 9 is a diagram showing a time chart of a drive signal in which the order of pulse output generated by pulse width modulation is opposite to that in FIG. 11;

FIG. 10 is an explanatory diagram of an image output device using a micro mirror array.

FIG. 11 is a diagram showing a time chart of a drive signal obtained by pulse-width-modulating a 3-bit video signal in order to display a projection image in eight gradations from 0 level to 7 level.

[Explanation of symbols]

 M11 to M41 Micromirror 10 Light source 11 Optical rotation filter 12 Drive unit 13 Projection lens 14 Illumination lens 121 Counter 122 Magnitude comparator 123 AND circuit

Claims (4)

[Claims] 1. A micromirror array having a plurality of micromirrors rotating between a first angular position for guiding light from a light source in a projection direction and a second angular position different from the first angular position. An image output device for outputting an image, wherein adjacent micro mirrors are rotationally driven based on mutually different drive signals. 2. A micromirror array having a plurality of micromirrors rotating between a first angular position for guiding light from a light source in a projection direction and a second angular position different from the first angular position. In an image output device that outputs an image, a first drive signal that is pulse width modulated based on a level of a video signal having a predetermined period is generated for each of the predetermined periods,
A first driving unit that drives a first micromirror to the first angle during a pulse output period of the first driving signal; and a pulse width modulation based on a level of the video signal, and an output of the pulse. A second drive signal whose order is opposite to the pulse output order of the first drive signal is generated for each of the predetermined periods, and the pulse output period of the second drive signal is different from the first micromirror. And a second drive section for driving the micromirror to the first angle. 3. The method according to claim 2, wherein the first driving unit and the second driving unit each include:
The image output device according to claim 1, wherein the first drive signal and the second drive signal each including one pulse having a width corresponding to a level of a video signal are generated at the predetermined cycle. 4. The apparatus according to claim 3, wherein, when the video signal is an n-bit digital signal, the first driving unit is 1 / (2 ⁿ -1) of the predetermined period.
A first counter that counts the clock of the predetermined period, and compares the count value of the first counter with the digital value of the video signal, and outputs the first drive signal based on the comparison result. A second comparator, wherein the second driving unit is configured to calculate 1 / (2 ⁿ −1) of the predetermined period.
A second counter that counts the number of clocks at each predetermined cycle, and compares the count value of the second counter with the digital value of the video signal, and outputs the second drive signal based on the comparison result. An image output device, comprising: