JPH11150698A - Image projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To input a monitor signal from a personal computer to an image projector which projects an image of a transmission original and to project and display a static electronic image by fetching image data in an appropriate form in a color signal. SOLUTION: A system controller 25 receives a horizontal/vertical synchronizing signal that is included in a monitor signal from a personal computer and measures a frequency of the horizontal/vertical synchronizing signal. A dot clock pulse of a frequency that corresponds to the measurement is supplied as a sampling pulse to an A/D conversion circuit 23. The circuit 23 performs digital conversion of a color signal under the sampling pulse. The color signals of R, G and B are converted into R and G image data in a conversion table 26 and are written in a multi-port DRAM 28. The controller 25 reads the image data from the DRAM 28 performs image display of it on an R liquid crystal display plate 14 and a G liquid crystal display plate through an LCD driver 29.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image projector having a function of projecting an electronic image displayed on a liquid crystal display panel in addition to projecting an image of a transparent original.

[0002]

2. Description of the Related Art For example, in order to allow a salesperson to easily introduce and explain a product in various situations on the go, a book of a B6 size, which can be stored in a business bag or a briefcase when carried, is provided. An ultra-small image projector in a reduced size is known from Japanese Patent Application Laid-Open No. 8-297328. This image projector is capable of enlarging and projecting an image recorded on a transparent original as a still image on a screen, and the size of the original is about the size of a notebook.

On the other hand, recently, images taken by a digital camera and a personal computer (hereinafter referred to as a personal computer) have been used.
Electronic images created in are used in various forms. Against this background, a portable image projector is also equipped with a liquid crystal display panel at or near a document placement stage, as in a general stationary image projector, thereby providing an electronic image. Being able to display is extremely effective in expanding its functions and applications. In particular, recently, the portability of personal computers has been greatly improved, and it has become possible to carry them together with the image projector. It is very convenient if these can be used in combination.

When an image is to be displayed by a signal from a personal computer, it is most convenient to use a monitor signal output from the personal computer for displaying a monitor image.
This is because all personal computers have monitor signal output terminals regardless of the model, and if you can use this, you do not need to add a dedicated output terminal on the personal computer side,
This is because image data for electronic image display can be obtained from all personal computers regardless of the model. If the monitor signal from a personal computer is a video signal standardized by the NTSC or PAL system, a dedicated IC developed for other uses can be used or a circuit with a relatively simple configuration can be used. And the circuit configuration of the image projector does not need to be complicated.

[0005]

However, especially in a portable personal computer, the frequency and resolution (number of dots) of the horizontal / vertical synchronization signals differ depending on the specifications of the integrated LCD monitor. A dedicated IC or a widespread circuit for capturing required image data necessary for displaying a still image from a monitor signal has not been provided so far because its use is limited. Therefore, versatility is required for a circuit built in the image projector for reading image data, and a simple circuit for capturing a standardized video signal as described above cannot be used. This is a major factor in cost increase.

Further, when extracting image data for displaying a still image from a monitor signal output from a personal computer and loading it into the memory of the image projector, the image data must be captured in pixel units. Although a dot clock is used inside the personal computer to read image data in pixel units, the monitor signal does not require a dot clock and is not output to the outside. Further, even if this is to be used directly on the image projector side, since the dot clock on the personal computer side is high speed, the circuit configuration becomes difficult and the parts become expensive.

[0007] In addition, in the case of a portable image projector, a light source with too high luminance cannot be used because of its size. Therefore, if a full-color liquid crystal display panel is used for displaying an electronic image as in a stationary image projector, even if the liquid crystal display panel is set to a full-color transmission state when projecting an image of a transmissive document, the The transmitted light amount is considerably reduced, and it is not possible to project the image of the transmitted original brightly.
Therefore, it has been studied to use a phase-change type liquid crystal with a small loss of light amount for a liquid crystal display panel and to display only an electronic image in four colors of red, green, white and black. According to this, an image of a transparent original can be projected brightly, and an electronic image can be displayed in four colors, so that an image display that is at least much easier to see than a monochrome image and has an appealing effect is performed. Thus, a very practical portable image projector can be obtained.

[0008] However, the phase transition type liquid crystal is a DSTN liquid crystal or a TST liquid crystal used for a monitor of a personal computer.
The response time is longer than that of the N liquid crystal, and the liquid crystal drive IC conventionally used cannot be used as it is. Therefore, the dedicated liquid crystal drive I
C is also required, which increases the manufacturing cost.

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and efficiently captures image data for displaying a still image from a monitor signal in which the frequency of a horizontal / vertical synchronization signal is not constant to a memory. It is an object of the present invention to provide an image projector which can be displayed on a display panel and used for projecting an image.

[0010]

In order to achieve the above object, the present invention generates a sampling pulse having a frequency corresponding to the frequency of a horizontal synchronizing signal in a monitor signal and the number of pixels of a liquid crystal display panel. A / D pulse
The color signal in the monitor signal which is input to the conversion circuit is digitally converted into image data for each pixel. The image data thus obtained is stored in the memory for one screen,
By supplying this to the liquid crystal display panel, a still electronic image is displayed and projected. Also, 1
The timing for writing the image data for the screen to the memory is preferably determined in synchronization with the vertical synchronization signal in the monitor signal.

As the memory, a serial access memory capable of writing one line of image data at high speed is used.
Using a multi-port DRAM mounted on a chip,
It is effective to transfer the image data that is sequentially sent and received from the 2D conversion circuit to a predetermined address area in units of one line to perform writing. Also, considering the image projection of a transparent original, it is disadvantageous to use a full-color liquid crystal display panel. Therefore, two types of phase transition type liquid crystal display panels are used in combination, and these two colors and white and black are used. It is practical to display an image in a total of four colors.

[0012]

FIG. 1 shows a cross section of a main part of an image projector using the present invention. The upper surface of the substantially rectangular parallelepiped main body 2 serves as a stage 3 on which the transparent original P is placed. An illumination lamp 5 serving as a white light source and a mirror 6 for reflecting light from the illumination lamp 5 toward the back side of the stage 3 are built in the main body 2, and the mirror 6 is rotatable about an axis 7. When not in use, the mirror 6 can be stored in the main body 2.

A column 8 is attached to the main body 2 by a shaft 9. By rotating the column 8 counterclockwise from the illustrated use position, the support column 8 can be folded to the non-use position. A projection head 10 is attached to the tip of the column 8 by a shaft 11, and is rotatable between an illustrated use position and an unused position indicated by a two-dot chain line in FIG. In order to move the projection head 10 from the use position to the non-use position, the projection head 10 may be rotated clockwise in FIG. 1, and the click of the projection head 10 is stopped at each of the use position and the non-use position. Is done. The legs supporting the main body 2 are also foldable when not in use in consideration of portability.

The stage 3 is 120 m in consideration of portability.
It has a size of mx 120 mm. Then, as shown in FIG. 1, the Fresnel lens plate 1
3, a liquid crystal display panel 16 in which an R liquid crystal display panel 14 of red transmission type and a G liquid crystal display panel 15 of green transmission type are stacked, and a Fresnel lens plate 17 are laminated. The lowermost Fresnel lens plate 17 directs the light from the illumination lamp 5 reflected by the mirror 6 upward as a substantially parallel light flux. The upper Fresnel lens plate 13 functions to efficiently direct the transmitted light to the projection head 10 so as not to deviate from the projection optical path.

R liquid crystal display panel 14 and G liquid crystal display panel 15
Are nematic-cholesteric phase transitions (N
(CPT) liquid crystal. The R liquid crystal display panel 14
When the cholesteric phase state is reached, only red light is transmitted as it is and other color lights are scattered, and when the nematic phase state is reached, all color lights are transmitted. G LCD panel 15
In the cholesteric phase state, only the green light is transmitted as it is and other color lights are scattered, and when the nematic phase state is reached, all the color lights are transmitted similarly. The wavelength of the color light scattered when these liquid crystal display panels 14 and 15 enter the cholesteric phase state is determined according to Bragg's reflection conditions, and the helical structure of each liquid crystal, particularly the helical pitch and the anisotropic refractive index. Depends on gender.

The R liquid crystal display panel 14 and the G liquid crystal display panel 15 are used together with a transparent electrode, as is well known, and can be driven pixel by pixel according to the structure of the transparent electrode. Each pixel has 800 × 600 dots, which corresponds to the S-VGA standard. It is also possible to use 640 × 480 dots in accordance with the VGA standard.

As described above, by driving the R liquid crystal display panel 14 dot by dot, all colors (white)
Two types of display, transmissive and red transmissive, can be obtained, and the G liquid crystal display panel 15 can obtain two display modes of all color (white) transmissive and green transmissive. Therefore, by using these layers in combination, it is possible to obtain a display in four forms: transmission of all colors (white), transmission of red, transmission of green, and blocking of all colors (black).

In the all-color transmission state, the white light from the illumination lamp 5 reaches the upper surface of the stage 3 as it is, so that if a transmission original is placed on the uppermost Fresnel lens plate 13, a transmission-type image projection is performed as it is. The image recorded on the transparent original can be projected on the screen in full color via the projection lens 18 and the mirror 19. Further, instead of using the transparent original P, R
By driving the liquid crystal display panel 14 and the G liquid crystal display panel 15 according to desired image data, it is possible to display characters and images in four colors of white, red, green, and black.

Image data for driving the liquid crystal display panels 14 and 15 is input from a personal computer externally connected to the image projector. Therefore, a circuit unit 20 for displaying an electronic image is built in the main body 2 so that a monitor signal from a personal computer can be input. FIG. 2 shows a schematic configuration of the circuit unit 20.

In FIG. 2, among the monitor signals output from the personal computer 22, R, G, and B color signals are input to an A / D conversion circuit 23 of a circuit unit 20, and a horizontal / vertical synchronization signal is output from a timing circuit. 24 and the system controller 25. The A / D conversion circuit 23 responds to the sampling pulse from the timing circuit 24 and converts the R, G, and B color signals output as analog signals into digital signals corresponding to the respective signal levels.

The system controller 25 is a personal computer 22
Monitor the horizontal / vertical synchronization signals of the monitor signals from
Set the frequency of the dot clock oscillator built in the. The oscillation frequency F ₀ of the dot clock oscillator is determined as “F ₀ = F _ref × N” with _respect to the frequency F _ref of the horizontal synchronization signal. The value of N should be at least
The number of pixels in the horizontal direction needs to be larger than the number of pixels in the liquid crystal display panels 14 and 15 as described above. Depending on the model etc., "102
It is preferable to set a value of about “4” or “1056”.

In order to obtain a dot clock having a frequency which is N times the frequency of the horizontal synchronizing signal, it is not always necessary to use a dot clock oscillator whose oscillation frequency is variable. For example, it is possible to adjust the circuit constant of the frequency dividing circuit, and to obtain a dot clock having a desired frequency using an IC chip known as a PLL (Phase Locked Loop). In particular, when a PLL is used, the multiple N
Only needs to be set by the system controller 25.
Thereafter, it becomes possible to multiply the frequency of the horizontal synchronizing signal inputted without passing through the system controller 25 by N times.

The dot clock pulse thus obtained is input to the timing circuit 24, and the timing circuit 24 supplies this to the A / D conversion circuit 23 as a sampling pulse. The A / D conversion circuit 23 converts the color signals into digital signals based on the sampling pulses, and the digitally converted color signals are input to the conversion table 26. The conversion table 26 ignores the B signal and binarizes the R signal and the G signal under a certain threshold. As a result, R image data and G image data represented by "1" and "0" are output from the conversion table 26 for each pixel determined according to the dot clock, and these image data are sent to the multiport DRAM 28. Is entered.

The multi-port DRAM 28 is a normal DR.
A memory that has an AM (Dynamic Random Access Memory) and a SAM (Serial Access Memory) that can be accessed at high speed on one chip, and a storage area for R image data and G image data is predetermined. Then, the conversion table 26
The R image data and the G image data output for each pixel from are stored in the SAM for each line, and then sequentially written to each memory area of the DRAM line by line. Note that a high-speed RISC microcomputer (for example, SH7034: manufactured by Hitachi, Ltd.) is used as the system controller 25 so that the multiport DRAM 28 can be directly accessed without the need for a DRAM dedicated peripheral circuit that is normally required. It has become.

Each of the liquid crystal display panels 14 and 15 is configured by arranging minute liquid crystal segments in pixel units. Each liquid crystal segment has a segment terminal connected independently for each segment, and a line unit. And a common terminal commonly connected between the segments. By controlling these segment terminals and common terminals with signals from the system controller 25 via the LCD driver 29, the liquid crystal display panel 1 is controlled.
4, 15 can be driven.

The operation of the above configuration is as follows. As shown in the main flow of FIG. 3, first, the circuit unit 20 and the liquid crystal display panel 17 are initialized and cleared. When the user performs a page break operation for electronic image projection by a key operation unit provided in the image projector in a state of waiting for a page break input, the system controller 25 monitors the horizontal / vertical synchronization signal of the personal computer 22 and The oscillation frequency of the dot clock oscillator is set according to the frequency.

If the horizontal / vertical synchronization signal from the personal computer 22 is within an appropriate range, the image data for one screen from the monitor signal of the personal computer 22 is transferred to the multiport DR.
After being taken into AM28, it is placed on the R liquid crystal display panel 14, G
The electronic image is transferred to the liquid crystal display panel 15 and projected.
If the horizontal / vertical synchronizing signal from the personal computer 22 does not fall within an appropriate range, a page break input is waited, and the electronic image cannot be projected as it is. In this case, another method such as changing the model of the personal computer is required.

FIG. 4 is a flowchart showing a data reading process for one screen. If the frequency of the horizontal / vertical synchronization signal included in the monitor signal of the personal computer 22 is within an appropriate range, the frequency of the dot clock oscillator in the system controller 25 is set based on the frequency of the horizontal synchronization signal, This is supplied to the timing circuit 24. The timing circuit 24 inputs this dot clock pulse to the A / D conversion circuit 23 as a sampling pulse.

When the vertical synchronizing signal is input to the timing circuit 24 and the system controller 25, the system controller 25 enables the first one line of the multi-port DRAM 28 to be write-enabled (writable state).
The image data converted into binary data for each pixel by the / D conversion circuit 23 and the conversion table 26 is output to the multiport DR.
It is written to AM28. In addition, multiport DRAM
Since the 28 memory areas are partitioned for R image data and G image data and each has a SAM, each image data can be processed at high speed line by line.

In the process of writing image data, the horizontal synchronizing signal is monitored, and every time the horizontal synchronizing signal is input, the horizontal line counter is incremented by "1", and the horizontal line counter reaches a preset maximum value 600. Then, the reading of the image data for one screen is completed. Note that the maximum value of the horizontal line counter is determined by the liquid crystal display panel 14,
The number is set to 600 in accordance with the number of pixels in the 15 vertical directions.

When the R image data and G image data for one screen are read into the multi-port DRAM 28 in this manner,
The system controller 25 clears the liquid crystal display panels 14 and 15 and erases the image displayed so far.
As a result, both the R liquid crystal display panel 14 and the G liquid crystal display panel 15 enter the all-color transmitting state. This process can be dealt with, for example, by making the segment terminals and the common terminals of all the liquid crystal segments have the same potential at the same time.
In the case of a phase change liquid crystal, 30 seconds are required for the screen erasing process.
Since it takes about msec, for example, 50 msec
The following processing is performed after waiting for the delay time.

After the screens of the liquid crystal display panels 14 and 15 are cleared, the common terminals are simultaneously dropped to the ground potential to keep the screen clear state. Then multi-port DR
The image data read into the AM 28 is transferred to the liquid crystal display panel 14,
A process of transferring to each of the 15 liquid crystal segments is performed. At the time of this data transfer, first, the write line counter is set to an initial value "1", a driving voltage is applied to the common terminal of the liquid crystal segment corresponding to the first line, and the line is switched to the active state. The eye image data is called from the multiport DRAM 28 and transferred to the segment terminals of the liquid crystal segments at the corresponding pixel positions.

After a time delay of about 4 msec required for writing one line, image data for 600 lines is transferred to the liquid crystal segment at the corresponding pixel position while incrementing the write line counter by "1". This image data transfer processing is performed for each of the R liquid crystal display panel 14 and the G liquid crystal display panel 15. When one screen of image data has been transferred to each, the common terminals of all the liquid crystal segments are switched to the ground potential, and the screen is switched. Is performed.

As a result, an image for one screen is displayed on the R liquid crystal display panel 14 in R color, and an image for one screen is displayed on the G liquid crystal display panel 15 in G color. These liquid crystal display panels 14 and 15 are used by being superimposed on each pixel, so that in each liquid crystal segment of the R and G liquid crystal display panels 14 and 15, one of the liquid crystal segments at a pixel position where one of them transmits all colors. Dot display is performed using the other color light, and white dot display is performed at a pixel position where both colors are transparent. Further, at the pixel positions where only the respective color lights are transmitted, dots are displayed in black, and as a result, the image is projected in four colors.

The image projected in this way is kept as it is until a page break operation is performed again. In order to switch the screen, the user may operate the personal computer 22 to output a monitor signal of another screen, and then perform a page break operation. Since the projected image can be checked in advance on the monitor screen of the personal computer 22, if a page break operation is performed after the check, erroneous image projection can be avoided. Note that the present invention is not necessarily limited to S-
The present invention can be applied to not only a liquid crystal display panel using a VGA type pixel array but also other types. Further, the number of pixels to be written to the multi-port DRAM does not have to match the number of pixels of the liquid crystal display panel. It is also possible to control the display mode of one pixel of the display panel. In this case, the A / D is controlled by further considering digital image processing.
What is necessary is just to determine the frequency of the sampling pulse input to the conversion circuit.

[0036]

As described above, according to the present invention, the frequency of the dot clock pulse is set in consideration of the number of pixels of the liquid crystal display panel by measuring the horizontal / vertical synchronization signal included in the monitor signal from the personal computer. Since the image signal is obtained by sampling the color signal in the monitor signal based on this, even if the frequency of the horizontal / vertical synchronization signal output from the personal computer is not always constant, the pixel signal is not converted from the monitor signal. The image data of the unit can be easily read, and the electronic image can be projected regardless of the type of the personal computer. Also, when displaying images on a liquid crystal display panel composed of phase transition type liquid crystal segments based on the image data fetched into the memory, a microcomputer that enables direct access to the memory is used to control the data transfer in software. Since it is performed, an electronic image can be displayed without requiring a complicated drive circuit.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an image projector using the present invention.

FIG. 2 is a block diagram schematically showing a circuit configuration for electronic image projection.

FIG. 3 is a flowchart illustrating a main flow of an electronic image projection process.

FIG. 4 is a flowchart illustrating a procedure for reading image data for one screen from a monitor signal into a memory;

FIG. 5 is a flowchart showing a procedure for reading image data from a memory and transferring the image data to a liquid crystal display panel.

[Explanation of symbols]

 3 Stage 10 Projection head 13, 16 Fresnel lens plate 14 R liquid crystal display panel 15 G liquid crystal display panel 18 Projection lens 20 Circuit unit 22 Personal computer 23 A / D conversion circuit 24 Timing circuit 25 System controller 28 Multi-port DRAM

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI G09G 3/36 G09G 3/36

Claims (4)

[Claims] 1. A liquid crystal display panel having a function of projecting an image of a transparent original placed on a stage by a projection lens and displaying a still image of one screen on a liquid crystal display panel based on a monitor signal from a personal computer. In an image projector capable of projecting the electronic image by the projection lens, an A / D conversion circuit for converting a color signal in the monitor signal into image data for each pixel, and a horizontal synchronizing signal in the monitor signal A timing circuit for inputting a sampling pulse having a frequency and a frequency corresponding to the number of pixels of the liquid crystal display panel to the A / D conversion circuit; and sequentially storing image data obtained from the A / D conversion circuit to form one screen. A memory for storing image data for each minute, and a controller for displaying an electronic image on a liquid crystal display panel based on the image data read from the memory. Image projector, characterized in that Ranaru. 2. The image projector according to claim 1, wherein the timing circuit inputs a sampling pulse to an A / D conversion circuit in synchronization with a vertical synchronization signal in a monitor signal. 3. The memory comprises a multi-port DRAM having a serial access memory for storing one line of image data on one chip, and writes image data to a predetermined address area line by line. The image projector according to claim 2, wherein: 4. A liquid crystal display panel comprising two liquid crystal display panels, wherein each liquid crystal display panel is switched between a state of transmitting different color light and a state of transmitting all color light. The image projector according to claim 3, wherein the image projector is a liquid crystal display panel of a type.