JP2002365607A - Projection type liquid crystal projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection type liquid crystal projector which can have high contrast. SOLUTION: The projection type liquid crystal projector is provided with a first means for detecting the luminance level of a video signal in the one entire screen for every one screen, a second means for spatially cutting the light from a light source corresponding to the luminance level of the video signal in the one entire screen and a third means for adjusting the level of the video signal to be sent to a liquid crystal panel corresponding to the luminance level of the video signal in the one entire screen.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a projection type liquid crystal projector.

[0002]

2. Description of the Related Art In a conventional projection type liquid crystal projector, a system in which a light source is powered up or two or four light sources are used has been put to practical use in order to increase luminance. However, in such a method, there is a problem that the high luminance portion can be made bright, but the low luminance portion cannot be made black, so that a high contrast cannot be obtained.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a projection type liquid crystal projector capable of obtaining a large contrast.

[0004]

A first projection type liquid crystal projector according to the present invention is a first means for detecting a brightness level of a video signal for one entire screen for each screen, and a brightness level of a video signal for one whole screen. And a third means for adjusting the level of the video signal to be sent to the liquid crystal panel according to the brightness level of the video signal for one entire screen. It is characterized by the following.

As the second means, a means for spatially blocking light from the light source so that the lower the luminance level of the video signal with respect to one entire screen, the greater the amount of spatial light blocking from the light source. The third means adjusts the level of the video signal to be sent to the liquid crystal panel so that the lower the brightness level of the video signal with respect to one entire screen, the higher the level of the video signal to be sent to the liquid crystal panel. .

A second projection type liquid crystal projector according to the present invention is a first means for detecting a brightness level of a video signal for one entire screen for each screen, and a light source according to a brightness level of a video signal for the whole screen. And a third means for adjusting the level of the video signal sent to the liquid crystal panel in accordance with the brightness level of the video signal with respect to one entire screen.

As the second means, a means for temporally blocking light from the light source so that the lower the luminance level of the video signal with respect to one entire screen, the greater the amount of temporal blocking of the light from the light source is used. The third means adjusts the level of the video signal to be sent to the liquid crystal panel so that the lower the brightness level of the video signal with respect to one entire screen, the higher the level of the video signal to be sent to the liquid crystal panel. .

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

[1] Description of First Embodiment

FIG. 1 shows the configuration of a projection type liquid crystal projector.

A projection lens 2 is provided on the front side of the liquid crystal panel 1.
Is arranged. On the back side of the liquid crystal panel 1, a condenser lens 3, a PSC 4, an integrator lens pair 5,
A lens 6 is arranged. The PSC is called a PS converter or a polarization conversion prism array, and is used to convert P waves and S waves. PSC
Converts, for example, a P wave as it is, converts an S wave into a P wave, and converts all input light into a P wave to output.

A combining prism 7 is arranged behind the lens 6. Around the combining prism 7, a first light source 11 and a second light source 12 are arranged to face each other with the combining prism 7 as a center. Condensing lenses 13 and 14 are provided on the front side of the first light source 11 and the second light source 12, respectively.
Are arranged respectively.

A first light source 1 is provided between a condenser lens 13 provided on the front side of the first light source 11 and the combining prism 7.
A blocking mechanism 15 having a shutter for blocking or transmitting light incident on the combining prism 7 from 1 is provided.

When the shutter of the blocking mechanism 15 is open, light emitted from the first light source 11 and the second light source 12 is incident on the combining prism 7 via the condenser lenses 13 and 14, respectively. You. The light incident on the combining prism 7 is
Since the light is emitted from the combining prism 7 toward the lens 6 and enters the liquid crystal panel 1 via the lens 6, the integrator lens pair 5, the PSC 4 and the condenser lens 3,
An image written on the liquid crystal panel 1 is projected via a projection lens 2 onto a screen (not shown) arranged in front of the projection lens 2.

When the shutter of the blocking mechanism 15 is closed, only the light emitted from the second light source 12 is incident on the combining prism 7 via the condenser lens 14. Therefore, in this case, the amount of light incident on the liquid crystal panel 1 is approximately の of that when the shutter of the blocking mechanism 15 is open.

An input video is written to the liquid crystal panel 1 via a video circuit unit 30. The video circuit unit 30 is an NTS
An input unit 31 to which a TV signal such as C or a PC signal such as VGA is input; a video processing unit 32 that performs video processing according to various input video signals; a signal adjustment unit that adjusts a signal level according to the level of the video signal A liquid crystal panel driving section 34 and a control section (microcomputer) 35 for driving the liquid crystal panel 1 in accordance with the video signal from the signal adjusting section 33 and 33 are provided. The control unit 35 controls each unit in the video circuit unit 30 and controls the cutoff mechanism unit 15.

FIG. 2 shows the configuration of the signal adjustment unit 33.

The video signal obtained by the video processing section 32 is sent to the field memory 41 and also sent to the video signal level detection section 45. Field memory 41
Is controlled by the field memory control unit 42.

The video signal stored in the field memory 41 is sent to a signal correction processing section 43 and also sent to a selector 44. The signal correction processing unit 43 performs a process of substantially doubling the video signal level. Signal correction processing unit 4
The output of 3 is sent to the selector 44. Selector 44
Selects and outputs one of two input signals based on a control signal from the control unit 35. The video signal output from the selector 44 is sent to the liquid crystal panel drive section 34 and written into the liquid crystal panel 1.

The video signal level detection section 45 calculates the maximum value and the average value of the video signal level for each field, and sends them to the control section 35. The control unit 35 performs the following processing based on the maximum value and the average value of the video signal levels sent from the video signal level detection unit 45.

That is, it is determined whether or not the maximum value of the video signal level is equal to or less than the threshold value for maximum value THA.
It is determined whether or not the average value of the video signal level is equal to or less than the threshold value for average value THB.

The maximum value of the video signal level is below THA, and the average value of the video signal levels in one field is THB.
In the following cases, the control unit 35 sends a shut-off ON signal to the shut-off mechanism unit 15 and sends a control signal for causing the selector 44 to select the output of the signal correction processing unit 43.
The cutoff mechanism 15 closes the shutter based on the cutoff ON signal. However, the timing to close the shutter is
Control is performed so as to be within the blanking period of the video signal.

When the maximum value of the video signal level is larger than THA or the average value of the video signal level is larger than THB, a cutoff signal is sent to the cutoff mechanism 15 and the output of the field memory 41 is sent to the selector 44. Send a control signal to make selection. The breaking mechanism 15 is
The shutter is opened based on the cutoff signal. However, the timing for opening the shutter is controlled so as to be within the blanking period of the video signal.

In the above embodiment, when the video signal level (maximum value, average value) is higher than a predetermined level, a normal video signal is sent to the liquid crystal panel 1 and
Light from the two light sources 11 and 12 is applied to the liquid crystal panel 1.

When the video signal level (maximum value, average value) is equal to or lower than a predetermined level, the video signal whose signal level has been doubled by the signal correction processing section 43 is sent to the liquid crystal panel 1 and the two Only the light from one of the light sources 11 and 12 is applied to the liquid crystal panel 1.

Therefore, when the luminance level of one screen is low, the black level is made darker, and when the luminance level of one screen is high, the conventional luminance can be maintained. For this reason,
The contrast is improved.

FIG. 12 shows the relationship between an input video signal and display luminance in the first embodiment, and FIG. 13 shows the relationship between an input video signal and display luminance in a conventional two-lamp system. .

In this example, in the first embodiment, when the video signal is in the range from the intermediate value (A + B) / 2 to the maximum value B, the video signal is transmitted to the liquid crystal panel 1 as usual. At the same time, the light from the two light sources 11 and 12 is applied to the liquid crystal panel 1. However, when the video signal is in the range from the minimum value A to the intermediate value (A + B) / 2, the video signal whose signal level has been doubled is sent to the liquid crystal panel 1 and the two light sources 11 and 12 Only the light from one of the light sources is applied to the liquid crystal panel 1.

On the other hand, in the conventional example, in the entire range of the video signal, a normal video signal is sent to the liquid crystal panel 1 and the light from the two light sources 11 and 12 is irradiated on the liquid crystal panel 1.

Therefore, comparing FIG. 12 and FIG. 13, the maximum value b of the display luminance is the same in both cases, but the minimum value of the display luminance in the first embodiment is の of the conventional example. ing. For this reason, the contrast is improved in the first embodiment as compared with the conventional example.

[1-1] Description of First Modification

FIG. 3 shows a modification of the signal adjusting unit 33. 3, the same components as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted.

In the signal adjusting section 33, a scene change detecting section 46 for detecting a scene change is added to the signal adjusting section in FIG.

FIG. 4 shows an example of the structure of the scene change detecting section 46.

The scene change detecting section 46 calculates the average luminance level of the current field based on the video signal obtained by the video processing section 32.
1. An average memory 52 for holding the average luminance level of the previous field calculated by the average luminance level calculation section 51, and an average luminance level of the current field calculated by the average luminance level calculation section 51 and held in the average memory 52. And a correlation value calculation unit 53 for calculating a correlation value (difference value) with the average luminance level of the previous field.
The correlation value calculated by the correlation value calculation unit 53 is sent to the control unit 35.

The control unit 35 stores the history of the correlation values sent from the correlation value calculation unit 53, and determines that a scene change has occurred when the correlation values change rapidly. The control unit 35 controls the cutoff mechanism unit 15 only immediately after detecting a scene change. That is, immediately after detecting a scene change, the control unit 35
The maximum value of the video signal level is equal to or less than the threshold THA for the maximum value, and the average value of the video signal level is the threshold TH for the average value.
When it is determined that the difference is equal to or less than B, a cutoff ON signal is sent to the cutoff mechanism unit 15 and a control signal for causing the selector 44 to select the output of the signal correction processing unit 43 is sent.

Further, immediately after detecting the scene change, the control unit 35 sets the maximum value of the video signal level to THA.
If it is determined that the value is greater than the threshold value or the average value of the video signal level is greater than THB,
Along with transmitting the FF signal, the control signal for causing the selector 44 to select the output of the field memory 41 is transmitted.

In the above embodiment, a two-lamp projection type liquid crystal projector having two light sources has been described. However, the present invention is also applicable to a four-lamp projection liquid crystal projector having four light sources. Can be applied.

In this case, a blocking mechanism is provided for each of the three light sources among the four light sources, and the light amount is set to １ ／, ／, ／, and の of the total light amount of the four lamps. / 4
And so on. Further, the signal adjusting unit 33 has a function of generating a signal in which the signal level of the output signal of the video processing unit 32 is quadrupled, quadrupled, quadrupled, and 倍, and a control signal from the control unit 35. Of 4
It has a function of selecting and outputting one of the types of signals.

The control unit 35 selects the light amount according to the level (maximum value, average value) of the video signal from the video processing unit 43 in one of four predetermined levels, A signal is selected from four video signals having different levels. At this time, as the level of the video signal from the video processing unit 43 is lower, a smaller amount of light is selected and a higher level video signal is selected.

[1-2] Description of Second Modification

FIG. 5 shows a modification of the projection type liquid crystal projector. 5, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

A projection lens 2 is provided on the front side of the liquid crystal panel 1.
Is arranged. On the back side of the liquid crystal panel 1, a condenser lens 3, a PSC 4, and an integrator lens pair 5 are arranged. The light source 11 is arranged behind the integrator lens pair 5.

A blocking mechanism 16 is arranged between the integrator lens pair 5. FIG.
As shown in the figure, four light shielding plates 61 to 64 held inside and outside the integrator lens pair 5 so as to be able to advance and retreat.
And a driving device (not shown) for independently driving each of the light shielding plates 61 to 64 forward and backward. Each light shielding plate 61-
The driving device 64 controls the light from the light source 11 in four stages of 1/4, 2/4, 3/4, and 4/4, which is controlled by the control unit 35.

The signal adjusting section 33 has a function of calculating an average value (or maximum value) of the video signal level for each field and sending it to the control section 35. Also, the signal adjusting unit 3
Reference numeral 3 denotes a function of generating a signal obtained by quadrupling the signal level of the output signal level of the video processing unit 32, 2/3, 1/3, and 1 and a control signal from the control unit 35 to control the four types. It has a function of selecting and outputting one of the signals.

The control unit 35 determines that the average (or maximum) of the video signal levels sent from the signal adjustment unit 33 is the first
If the threshold value TH1 or less, the light from the light source 11 is 1
While controlling the shutoff mechanism 16 so as to be / 4,
The signal adjustment unit 33 is controlled so that a signal whose signal level is four times the output signal of the video processing unit 32 is sent to the liquid crystal panel 1.

The control unit 35 determines that the average (or maximum) of the video signal levels sent from the signal
The second threshold value TH2 which is larger than the threshold value TH1 (TH1 <TH
2) In the case of being less than or equal to, the cut-off mechanism 16 is controlled so that the light from the light source 11 becomes 2/4, and the signal whose signal level is twice as high as the output signal of the video The signal controller 33 is controlled so as to be sent to the panel 1.

The control unit 35 determines that the average (or maximum) of the video signal levels sent from the signal
The third threshold value TH3 (TH2 <TH) that is larger than the threshold value TH2.
3) In the case where it is equal to or less than the above, the splitting / blocking mechanism 16 is controlled so that the light from the light source 11 becomes 3/4, and the signal level of the output signal of the video processing unit 32 is 4/3 times the signal level Is transmitted to the liquid crystal panel 1 to control the signal adjusting unit 33.

The control unit 35 determines that the average (or maximum) of the video signal levels sent from the signal
If the threshold value TH3 is larger than the threshold value TH3,
While controlling the shutoff mechanism 16 so as to be / 4,
The signal controller 33 is controlled so that the output signal of the video processor 32 is sent to the liquid crystal panel 1.

[1-3] Description of Third Modification

FIG. 7 shows a configuration of a modification of the projection type liquid crystal projector. 7, the same components as those in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted. The third modification is different from the second modification in the cutoff mechanism.

A projection lens 2 is provided on the front side of the liquid crystal panel 1.
Is arranged. On the back side of the liquid crystal panel 1, a condenser lens 3, a PSC 4, an integrator lens pair 5,
A pair of condenser lenses 6, 8 are arranged. A light source 11 is arranged behind the pair of condenser lenses 6 and 8.

A blocking mechanism 17 is disposed between the pair of condenser lenses 6 and 8. As shown in FIG. 8, the blocking mechanism 17 includes a disk 71 and a driving device 72 for sliding the disk 71. The amount of advance and retreat of the disc 71 is adjusted by controlling the drive unit 72 by the control unit 35. The disc 71 is formed such that the light transmittance changes radially from the center in the radial direction. Second
In the modified example, the light amount is adjusted in four stages by adjusting the amount of advance and retreat of the disk 71.

[2] Description of Second Embodiment

The conventional projection type liquid crystal projector has a problem that a moving image is blurred (so-called moving blur) since the liquid crystal device is a hold type display. In view of this, intermittent display with a shutter has been proposed. However, this method has a problem in that the display luminance is reduced by an amount that is blocked by the shutter.

In the second embodiment, a projection type liquid crystal projector which can prevent a motion blur and a decrease in display luminance level is realized.

FIG. 9 shows the configuration of a projection type liquid crystal projector.

On the front side of the liquid crystal panel 1, a projection lens 2 is provided.
Is arranged. On the back side of the liquid crystal panel 1, a condenser lens 3, a PSC 4, an integrator lens pair 5,
A pair of condenser lenses 6, 8 are arranged. A light source 11 is disposed behind the pair of condenser lenses 6 and 8.

An interception mechanism 18 is arranged between the pair of condenser lenses 6 and 8. The shut-off mechanism 18 is configured as shown in FIG.
As shown in FIG. 8, a disk 81, a motor (not shown) for rotating and driving the disk 81, the disk 81 is advanced from the light path non-blocking position to the light path blocking position, and the disk 81 is moved to the light path blocking position. And a drive unit 82 for retreating the optical path to the optical path non-blocking position. Half of the disk 81 is formed on a transparent light transmitting portion 81a that transmits light, and the other half is formed on a light shielding portion 81b that blocks light.

The disk 81 is driven so as to rotate once in one field period in synchronization with one field of the video signal. When the vertical synchronizing signal of the video and the start position of the transmissive portion 81a or the light shielding portion 81b coincide with each other, and the disc 81 is advanced to the optical path blocking position, in this example, the video period within one field The light from the light source 11 is cut off by the light-shielding portion 81b during half the period.

The configuration of the video circuit unit 30 is the same as that shown in FIG. The configuration of the signal adjustment unit 33 is the same as that shown in FIG.

The control unit 35 includes a video signal level detection unit 45
(See FIG. 2), the maximum value of the video signal level in one field is equal to or less than the threshold value for maximum value THA and 1 based on the maximum value and the average value of the video signal level in one field transmitted from FIG. When the average value of the video signal levels in the field is equal to or less than the threshold value for average value THB, a shut-off ON signal is sent to the shut-off mechanism unit 18 and the selector 44
A control signal for selecting the output of the signal correction processing unit 43 (see FIG. 2) is sent to (see FIG. 2). Cutoff mechanism 18
Causes the disk 81 to advance to the optical path blocking position based on the blocking ON signal.

When the maximum value of the video signal level is greater than THA or the average value of the video signal level is greater than THB, a shutoff OFF signal is sent to the shutoff mechanism 18 and a field is sent to the selector 44 (see FIG. 2). A control signal for selecting the output of the memory 41 (see FIG. 2) is sent. The shutoff mechanism 18 is configured to output
The disk 81 is retracted to the optical path non-blocking position.

In this embodiment, when the video signal level (maximum value, average value) is higher than a predetermined level, a normal video signal is sent to the liquid crystal panel 1 and the light from the light source 11 is 1 is constantly irradiated.

When the video signal level (maximum value, average value) is lower than a predetermined level, the video signal whose signal level has been doubled by the signal correction processing section 43 (see FIG. 2) is transmitted to the liquid crystal panel 1. And the shut-off mechanism 1
8, the light from the light source 11 is blocked by the light blocking portion 81b in a half of the video period in one field. That is, when the video signal level is low, intermittent display becomes possible while maintaining the luminance level of the high luminance portion, and the motion blur is reduced. Further, since the luminance level of the low luminance portion is halved, the contrast is improved.

[2-1] Description of First Modification

As the signal adjusting unit 33, FIGS.
As shown in FIG. 7, a camera provided with a scene change detection unit 46 may be used.

When such a signal adjustment unit 33 is used, the control unit 35 stores the history of the correlation values calculated by the correlation value calculation unit 53 (see FIG. 4) in the scene change detection unit 46. In addition, when the correlation value changes suddenly,
It is determined that a scene change has occurred.

The control section 35 controls the cutoff mechanism section 18 only immediately after detecting a scene change. That is, immediately after detecting the scene change, the control unit 35 sets the maximum value of the video signal level in one field to T.
When it is determined that the signal level is equal to or less than HA and the average value of the video signal levels in one field is equal to or less than THB, a cut-off ON signal is sent to the cut-off mechanism unit 18 and the output of the signal correction processing unit 43 is selected by the selector 44 Send a control signal to make

Further, immediately after detecting the scene change, the control unit 35 determines that the maximum value of the video signal level in one field is larger than THA or that the average value of the video signal level in one field is larger than THB. At the same time, the controller 44 sends a shutoff OFF signal to the shutoff mechanism 18 and sends a control signal for causing the selector 44 to select an output of the field memory 41.

[2-2] Description of Second Modification

FIG. 11 shows a modification of the shut-off mechanism.

The blocking mechanism 19 includes a disc 91 and a disc 91.
And a drive device 92 for sliding the disk 91. In the disk 91, the rotation angle region occupied by the light shielding portion is different between the first annular portion as the outer peripheral portion, the third annular portion as the inner peripheral portion, and the second annular portion as an intermediate portion between them. .

In the first annular portion, which is the outer peripheral portion, １ ／ of one rotation angle is formed in the light shielding portion, and the remaining ／ is formed in the light transmitting portion. In the second annular portion, half of one rotation angle is formed in the light shielding portion, and the other half is formed in the light transmitting portion. In the first annular portion, which is the inner peripheral portion, 3/4 of one rotation angle
Are formed in the light shielding portion, and the remaining 残 り is formed in the light transmitting portion.

The advance / retreat amount of the disk 91 is adjusted by controlling the drive unit 92 by the control unit 35. Drive unit 9
Reference numeral 2 denotes a position where the disk 91 deviates from the optical path (optical path non-blocking position), a position where the first annular portion, which is the outer peripheral portion of the disk 91, comes on the optical path based on a command from the control unit 35, The position of the disc 91 is switched in four stages: a position where the second annular portion 91 is on the optical path and a position where the third annular portion which is the inner peripheral portion of the disk 91 is on the optical path.

The signal adjusting section 33 (see FIG. 9) has a function of calculating an average value (or maximum value) of the video signal level for each field and sending it to the control section 35. Also,
The signal adjustment unit 33 has a function of generating a signal obtained by quadrupling the signal level of the output signal level of the video processing unit 32, 2/3, 1/3 and 1 times, and the control signal from the control unit 35. It has a function to select and output one of the four types of signals.

The control unit 35 determines that the average value (or maximum value) of the video signal levels sent from the signal
When the threshold value is equal to or less than the threshold value TH1, the cut-off mechanism unit 19 is controlled so that the third annular portion, which is the inner peripheral portion of the disk 91, is located on the optical path. The signal adjustment unit 33 is controlled so that a signal whose signal level is four times higher is sent to the liquid crystal panel 1.

The control unit 35 determines that the average (or maximum) of the video signal levels sent from the signal adjustment unit 33 is the first
The second threshold value TH2 which is larger than the threshold value TH1 (TH1 <TH
2) In the following cases, the cut-off mechanism 19 is controlled so that the second annular portion of the disk 91 is positioned on the optical path, and the signal level of the output signal of the video processing unit 32 is 2 The signal adjusting unit 33 is controlled so that the doubled signal is sent to the liquid crystal panel 1.

The control unit 35 determines that the average (or maximum) of the video signal level sent from the signal adjustment unit 33 is the second
The third threshold value TH3 (TH2 <TH) that is larger than the threshold value TH2.
3) In the case of the following, the first outer peripheral portion of the disk 91
The shut-off mechanism 19 is positioned so that the annular portion is positioned on the optical path.
And the signal adjustment unit 33 is controlled so that a signal whose signal level is 4/3 times the output signal of the video processing unit 32 is sent to the liquid crystal panel 1.

The control unit 35 determines that the average (or maximum) of the video signal levels sent from the signal adjustment unit 33 is the third
If the threshold value TH3 is larger than the threshold value TH3, the cut-off mechanism unit 19 is controlled so that the disc 91 is located at a position deviated from the optical path, and the signal adjustment unit 33 is set so that the output signal of the video processing unit 32 is sent to the liquid crystal panel 1. Control.

[0081]

According to the present invention, a projection type liquid crystal projector capable of obtaining a large contrast can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a projection type liquid crystal projector according to a first embodiment.

FIG. 2 is a block diagram illustrating a configuration of a signal adjustment unit 33.

FIG. 3 is a block diagram showing a modification of the signal adjustment unit 33.

FIG. 4 is a block diagram illustrating a configuration of a scene change detection unit 46.

FIG. 5 is a block diagram showing a modification of the projection type liquid crystal projector.

FIG. 6 is a configuration diagram showing a configuration of a blocking mechanism unit 16;

FIG. 7 is a block diagram showing a modification of the projection type liquid crystal projector.

FIG. 8 is a configuration diagram illustrating a configuration of a blocking mechanism unit 17;

FIG. 9 shows a configuration of a projection type liquid crystal projector according to a second embodiment.

FIG. 10 is a configuration diagram showing a configuration of a blocking mechanism unit 18.

FIG. 11 is a configuration diagram illustrating a configuration of a blocking mechanism unit 19;

FIG. 12 is a graph showing a relationship between an input video signal and display luminance in the first embodiment.

FIG. 13 is a graph showing a relationship between an input video signal and display luminance in a conventional two-lamp system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal panel 11, 12 Light source 15, 16, 17, 18, 19 Shut-off mechanism part 30 Video circuit part 33 Signal adjustment part 35 Control part

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H088 EA13 HA17 HA20 HA23 HA24 MA02 2H091 FA11Z FA21Z FA26X FA34Z FA41Z GA12 LA17 MA07 2H093 NC42 NC50 NC54 ND03 ND04 NG02

Claims (4)

[Claims] 1. A first means for detecting a brightness level of a video signal for an entire screen for each screen, a second means for spatially blocking light from a light source according to the brightness level of a video signal for the entire screen. And a third means for adjusting the level of the video signal sent to the liquid crystal panel according to the luminance level of the video signal for one entire screen. The second means spatially blocks light from the light source such that the lower the luminance level of the video signal with respect to one entire screen, the larger the amount of spatial blocking of light from the light source. The third means adjusts the level of the video signal sent to the liquid crystal panel so that the lower the brightness level of the video signal with respect to one entire screen, the higher the level of the video signal sent to the liquid crystal panel. 2. The projection type liquid crystal projector according to 1. 3. A first means for detecting a luminance level of a video signal for an entire screen for each screen, a second means for temporally blocking light from a light source in accordance with the luminance level of a video signal for the entire screen. And a third means for adjusting the level of the video signal sent to the liquid crystal panel according to the luminance level of the video signal for one entire screen. 4. A second means for temporally blocking light from a light source such that the lower the luminance level of a video signal with respect to one entire screen, the greater the amount of temporal blocking of light from the light source. The third means adjusts the level of the video signal sent to the liquid crystal panel so that the lower the brightness level of the video signal with respect to one entire screen, the higher the level of the video signal sent to the liquid crystal panel. 4. The projection type liquid crystal projector according to 3.