CN211378152U

CN211378152U - DLP projector capable of enhancing contrast

Info

Publication number: CN211378152U
Application number: CN202020048697.0U
Authority: CN
Inventors: 饶钦和; 李衡; 岳德举; 白金刚
Original assignee: Guangdong Lianda Photoelectricity Co ltd
Current assignee: Guangdong Lianda Photoelectricity Co ltd
Priority date: 2020-01-09
Filing date: 2020-01-09
Publication date: 2020-08-28
Anticipated expiration: 2030-01-09

Abstract

The utility model provides a DLP projector of contrast can be strengthened, including at least one laser light source and at least one light modulator, laser light source produces the light beam in order to illuminate the light modulator, and every laser light source comprises a plurality of lasers, and the light that every laser light source sent has two at least wavelengths, will provide the laser instrument of the wavelength of higher contrast and place in the position that produces higher F number, will provide the laser instrument of the wavelength of lower contrast and place in the position that produces lower F number. The contrast improves along with the increase of F value, consequently, the utility model discloses show the contrast in the reinforcing projection image.

Description

DLP projector capable of enhancing contrast

Technical Field

The utility model belongs to the technical field of the projection technique and specifically relates to a DLP projecting apparatus that can strengthen contrast.

Background

A projector, also called a projector, is a device that can project images or video onto a screen. With the advancement and breakthrough of technology, the mainstream projectors in the market have been occupied by conventional CRT three-gun type projectors, and gradually by DLP (digital light Processor) projectors. Compared with the traditional CRT projector, the DLP projector has the advantages of bright color, rich levels, high saturation and the like, is widely popular with consumers, and is widely applied to scenes such as life entertainment, academic lectures, business exhibition and the like.

As is well known, the light sources of a projector are typically monochromatic light sources or three primary color light sources, and the light sources of the same primary color can emit light of different wavelengths, such as λ 1, λ 2, λ 3, λ 4 … …. Taking the laser light sources as an example, each laser light source is composed of a plurality of lasers, and the lasers are arranged in an array, and the lasers in the array can be the same wavelength or different wavelengths. For example, an array of 4 wavelengths of light sources for producing a single primary color may be arranged. The aim is that there are the same number of lasers per wavelength and that their energy is evenly distributed in the angular space of the light source. The light sources of the different primary colors are not necessarily regularly distributed. All light sources have the same polarization or a mixture of different polarizations. Therefore, it is a technical difficulty how to set the position of the laser for the laser light source to ensure that the projector has a high contrast.

SUMMERY OF THE UTILITY MODEL

In view of the above, it is desirable to provide a DLP projector with enhanced contrast.

A DLP projector capable of contrast enhancement includes at least one laser light source and at least one light modulator, the laser light source generating a beam of light to illuminate the light modulator, each laser light source being comprised of a plurality of lasers, each laser light source emitting light having at least two wavelengths, the laser providing the wavelength with the higher contrast being positioned to produce a higher F-number and the laser providing the wavelength with the lower contrast being positioned to produce a lower F-number.

Preferably, all the lasers of each laser light source are distributed in an array, and the contrast corresponding to the wavelength of the laser at the periphery of the array is smaller than the contrast corresponding to the wavelength of the laser at the position close to the center of the array.

Preferably, the size of the pixels or pixel pitch of the light modulator is selected to increase the contrast.

Preferably, green is chosen for a single primary color having two wavelengths.

Preferably, the wavelength of green is selected to be 520-570 nm.

Preferably, for the two primary colors having two wavelengths, green and red are selected.

Preferably, the wavelength of green is selected to be 520-570nm, and the wavelength of red is selected to be 570-700 nm.

Preferably, the system further comprises a synchronous control system for adjusting the power of the laser light source, and the intensity of the light emitted by the laser is controlled by a pulse width modulation mode.

Preferably, the synchronization control system includes: an image processing device, a logic control device, a light modulator and a light source drive; the image processing device is used for receiving original image information and outputting a series of image data blocks and frame synchronization signals; the logic control device is used for controlling the DMD device of the optical modulator to be switched between an open state and a closed state between two adjacent frame synchronization signals; the logic control device is also used for controlling the light source drive according to the frequency of the frame synchronization signal so as to adjust the frequency and the phase difference of the output waveform of the laser light source, so that the frequency of the output waveform of the laser light source is consistent with the frequency of the frame synchronization signal, a short-term high pulse signal in the output waveform of the laser light source is in the off-state time period of the DMD device, and the on-state time period of the DMD device is in a long-term constant low signal of the output waveform of the light source; and the DMD device is used for carrying out signal modulation on the image data block when the DMD device is in an open state so as to enable the projector to output a final correct image.

The utility model discloses a to provide the laser instrument of the wavelength of higher contrast and place in the position that produces higher F number, to provide the laser instrument of the wavelength of lower contrast and place in the position that produces lower F number, the contrast improves along with the increase of F value, consequently, the utility model discloses showing the contrast in the reinforcing projection image.

Drawings

Fig. 1 is a schematic diagram of a projection system provided by an embodiment of the present invention;

fig. 2A is a structural diagram of a light source according to an embodiment of the present invention;

fig. 2B is a schematic diagram of the same light source generating different light waves according to the embodiment of the present invention;

FIG. 3 is a schematic diagram of light waves with different wavelength bands according to an embodiment of the present invention;

fig. 4 is a detailed structural diagram of a light source according to an embodiment of the present invention;

fig. 5 is a schematic diagram of a synchronous control system of an embodiment of the present invention;

FIG. 6 is a possible timing control diagram for the embodiment of FIG. 5.

Detailed Description

In order to make the above objects, features and advantages of the present invention more comprehensible, embodiments accompanying the drawings are described in detail below. It should be noted that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and all other embodiments obtained by those skilled in the art without any inventive work are within the scope of the present invention.

Fig. 1 is a projection system 5 according to an embodiment of the present invention, which includes a projector 10 and a projection screen 20. Projector 10 includes at least one light source 12, at least one light modulator 14, and a projection lens assembly 16. The light source 12 generates a light beam 13 to illuminate the light modulator 14. Projector 10 also includes a controller 18 that controls light source 12 and/or light modulator 14. The controller 18 may be provided as a separate component.

The light modulator 14 may be a spatial light modulator or a light valve element. Each spatial light modulator or light valve element may correspond to a pixel of an image to be displayed and may be individually controlled to allow a certain amount of light to pass/not pass. Typically, each light modulator 14 is controlled over a range of intensity values between "on" and "off" to provide a range of gray scale values. This control may be in particular a pulse width modulation. The light modulator 14 may use a transmissive technique such as a liquid crystal panel in which different values may be quantified by turning on/off individual elements or taking values between on and off depending on the amount of light that needs to be emitted at the pixel location. Alternatively, the light modulator 14 may use a reflective technology such as Digital Micromirror Device (DMD) in Digital Light Processing (DLP) or Liquid Crystal On Silicon (LCOS).

The light beam 13 projects a pattern with an intensity distribution on the surface of the light modulator 14. In an embodiment of the invention, coherent light is optionally used, and the light source 12 comprises at least one coherent light source, for example a laser light source capable of emitting a high intensity light beam of one or more primary colors, or a set of laser light sources capable of emitting a high intensity light beam of one or more primary colors. The light source 12 and its array arrangement will be described in detail below.

In all embodiments of the present invention, light modulator 14 comprises at least one light modulator illuminated by light of at least one primary color (preferably green), two primary colors (preferably green and red), or more primary colors (preferably red, green, and blue). The wavelength range of green is 520-570nm, the wavelength range of red is 570-700nm, and the wavelength range of blue is 425-500 nm.

In a preferred embodiment of the present invention, an architecture is provided having three chips, where each chip is a spatial light modulator and is illuminated by a single primary color. The resulting three monochromatic images are then combined into one three-color image projected onto a screen.

Fig. 2A is a block diagram of light source 12 in which one integrator 30 is provided for each color in accordance with an embodiment of the present invention. The light source 12 provides three primary colors, a red light source 21, a green light source 22 and a blue light source 23. The light source 12 further comprises one or more combining optics 26, each primary light source producing a light beam 25.

For each primary color, the wavelength bands of the primary colors are shifted from each other in wavelength. Although each wavelength is shown as a vertical line in fig. 2B, in practice it has a certain spectral distribution around the center wavelength, as shown in fig. 3. Each of the primary colors (red (R), green (G), and blue (B) includes two wavelengths: B1 and B2 represent the primary color of blue, G1 and G2 represent the primary color of green, and R1 and R2 represent the primary color of red.B 1, G1, and R1 are the long wavelengths of blue, green, and red, respectively, and B2, G2, and R2 are the short wavelengths of blue, green, and red, respectively.

As shown in fig. 3, each wavelength has a certain spectral distribution or width around the center wavelength. Each

light source

21, 22, 23 may comprise a plurality of lasers, which may be arranged in an array distribution. The light sources 24 are offset from each other in one direction in a linear array, or in any other form of two orthogonal directions, or distributed in a 2D array, for example pseudo-randomly. The array may have light sources spaced in orthogonal directions (e.g., in columns and rows in a rectangular coordinate system), or may be spaced around circles of different diameters in a polar coordinate system. Each laser may emit light at one of the wavelength values, e.g., λ 1 or λ 2. Each laser may emit multiple beams at the same wavelength to increase the light intensity. To further increase the light intensity, multiple lasers of the same wavelength may be added.

The contrast was measured at 6 different wavebands at B1, B2, G1, G2, R1 and R2, respectively. The following table shows the measurement results.

Wave band	Contrast ratio
		R1	2585
R2	2017
		G1	2209
G2	3071
		B1	—
B2	1763

Since the blue wavelength is short, it is difficult to accurately measure the contrast. However, it has been confirmed that the contrast ratio of the short blue wavelength is lower than that of the long blue wavelength. In this experiment, the blue short wavelength, the green short wavelength, and the red long wavelength are significantly lower in contrast than the blue long wavelength, the green long wavelength, and the red short wavelength.

Referring to fig. 4, light source 24(24A, 24B, 24C … …) directs light beam 25 through combining optics 28 to integrator 30. Once the light enters the integrating element (e.g., rod or tube) of integrator 30, it remains within the range of the integrator due to reflection from the longitudinal walls of the integrator.

Referring to fig. 4, one light source 24 outputs light beams of at least two wavelengths (λ 1 and λ 2). Combining optics 28, such as a lens, group the beams together as closely as possible. The F-number of the beam (i.e. the light with the wavelength of λ 1) emitted by the laser at the periphery of the array will be low; for example, in fig. 4, λ 1 has an effective diameter D1. And the effective diameter will be higher for beams emitted by lasers near the center of the array (lambda 2 in fig. 4). As the predetermined angle of incidence on the integrator 30 increases with increasing distance from the optical axis, the overall F-number of the light source also decreases as the laser source moves further away from the optical axis.

For the light source 24(R or G or B), the contrast is improved if the wavelength λ 1 of the lasers at the periphery of the array corresponds to a contrast that is less than the wavelength λ 2 of the lasers near the center of the array. However, the longer the wavelength, the higher the contrast is not necessarily, depending on the wavelength chosen. Embodiments of the present invention place the lasers that provide the wavelengths of higher contrast at the locations where they produce higher f-numbers and the lasers that provide the wavelengths of lower contrast at the locations where they produce lower f-numbers.

More generally, for each primary color used, the contrast improves if the wavelength λ 1 of the light sources at the periphery of the array is associated with a lower contrast and the wavelength λ 2 of the light sources near the center of the array is associated with a higher contrast.

In fact, the contrast improves with increasing F-value, for wavelength λ 1 the contrast is lower and therefore the aperture D increases (D1), the F-value becomes smaller and therefore the wavelength λ 1 associated with the lower contrast has less effect on the contrast, while the aperture D decreases (D2) and therefore the F-value becomes smaller and is greater by selecting wavelength λ 2 (which is associated with a higher contrast towards or at the centre of the array) and therefore the contrast is improved for wavelength λ 2 while wavelength λ 2 remains unchanged or substantially unchanged. This embodiment improves contrast especially in dark images.

For a single primary color having two wavelengths or two wavelength ranges, green is therefore preferably chosen, for example in the range 520-570 nm. For two primary colors each having two wavelengths or two wavelength ranges, green (e.g., in the range of 520-570 nm) and red (e.g., in the range of 570-700 nm), more preferably 600-670nm, even more preferably 625-650nm are most preferably selected. The blue wavelength may be in the range of 425-500 nm.

The intensity of the light emitted by the laser may be controlled by a Pulse Width Modulation (PWM) scheme, for example, the control may be performed by a controller. Changing the power level will have an impact on the dynamic (frame or scene based) contrast.

When the light modulator (DMD) is biased, a higher contrast can be obtained if the laser light sources are all off. This is best achieved by finding the part of the PWM period where all pixels are off. In this case, no light can be reflected onto the screen. Of course, this can only be achieved if a particular time period on all mirrors of the DMD is black, or a combination PWM of the laser and DMD can be used, providing more bit depth and granularity. The PWM of the DMD can also be adjusted by taking into account the power variation of the laser.

Specifically, referring to the embodiment of fig. 5, the synchronization control system includes: an image processing device, a logic control device, a light modulator and a light source drive;

the image processing device is used for receiving original image information and outputting a series of image data blocks and frame synchronization signals;

the logic control device is used for controlling the DMD device to switch between an open state and a closed state between two adjacent frame synchronization signals;

the logic control device is also used for controlling the light source drive according to the frequency of the frame synchronization signal so as to adjust the frequency and the phase difference of the output waveform of the light source, so that the frequency of the output waveform of the light source is consistent with the frequency of the frame synchronization signal, a short-term high pulse signal in the output waveform of the light source is in the off-state period of the DMD device, and the on-state period of the DMD device is in a long-term constant low signal of the output waveform of the light source;

and the DMD device is used for carrying out signal modulation on the image data block when the DMD device is in an open state so as to enable the projector to output a final correct image.

Further, fig. 6 is a possible specific timing control diagram of the embodiment of fig. 5, and the following describes the embodiment of the present invention in detail based on the timing diagram. The embodiment of the present invention obtains original image information (the format of the original image is not limited) by using an image processing device, and outputs a series of image data blocks and frame synchronization signals. The frame synchronization signal may be the beginning or end of each frame of the image, with the image data block of each frame in between the two frame synchronization signals.

The logic control device can be a CPLD, PLD, FPGA or other device with logic programming, storage, processing and other functions, and is provided with a synchronous generator which can control the working state of the DMD and the phase difference or time difference between the light source output and the frame synchronization signal. In fig. 6, when each frame synchronization signal arrives, the DMD device is in the on state, and the DMD device can perform signal modulation on the image data block, i.e., the phase of the DMD is almost identical to the phase of the frame synchronization signal. Within each "DMD periodic signal", the DMD state switches between an on state, in which an image can be presented on the screen, and an off state, in which the time period is denoted T_DMDAnd in the closed state, the image can not be displayed on the screen and is marked as T_DARK. Obviously, T_DARKShould be as short as possible.

The logic control device also controls the phase difference of the light source output signal and the frame synchronization signal according to the frame synchronization signal, and the phase difference can be stored by utilizing a lookup table. The difference between different phase differences or time differences is determined by the properties of the DMD device, the light source, etc. Regardless of the difference in phase difference, the short-term high pulse signal output by the light source should be at T in the DMD OFF state_DARKWithin a time period. T is_DARKShould also have a minimum value which should at least exceed the pulse time T _PULSE10% of the total.

To achieve dynamic contrast control, diffraction effects associated with at least one modulator may be considered. These diffractive effects depend, for example, on the size of the pixels or pixel pitch of the light modulators, the wavelength of the light source, the orientation of each light modulator, the tilt angle of the different imagers, or the angle of illumination of the modulators by the light.

All degrees of freedom for modifying the contrast of the projected image may be taken into account when dynamically controlling the contrast and dynamically changing the contrast and/or brightness of the projected image based on the frame or scene content.

For example, based on image content, various policies may be followed. Only high contrast wavelengths near the optical axis can be increased from bright images to dark images. The low contrast wavelengths located at the periphery of the 2D light source array may also be reduced simultaneously. From a dark image to a bright image, the low contrast wavelengths near the optical axis can be increased while the high contrast wavelengths at the periphery of the light source 2D array are increased.

Therefore, the method for dynamically adjusting image contrast according to the embodiment of the present invention includes the following steps:

the laser sources are selected such that they provide light of one, two or more primary colors, one or more primary colors, some or each primary color having at least two wavelengths or wavelength ranges, determining the 2D configuration of the various laser sources according to their wavelength and the high or low contrast associated with each wavelength, and further according to whether to add or balance contrast on the projected image, pre-calibrating the various lasers configured as a function of power and measured contrast, the method further comprising the step of measuring the brightness of the projected image for each projected image, where the brightness may be calculated with a brightness detector, or may be used as an input to a laser driver, or for a controller, the method further comprises the step of calculating the power of each laser source as a function of the measured brightness and the pre-calibrated values, each laser source being driven with the calculated optical power.

The steps of measuring the brightness of the projected image and calculating the power of each laser may be performed during the projection process or may be pre-calculated by software based on the image content of the projected image.

When the contrast of the projected image is to be increased or is dependent on the image content, the emitted light power at wavelengths associated with a lower contrast of the projected image is reduced. For a single primary color having two wavelengths or two wavelength ranges, green is therefore preferably chosen, for example in the range 520-570 nm. For two primary colors each having two wavelengths or two wavelength ranges, green (e.g., in the range of 520-570 nm) and red (e.g., in the range of 570-700 nm) are most preferably selected. If blue is selected, the blue wavelength may be in the range of 425-500 nm.

The above-mentioned embodiments only represent some embodiments of the present invention, and the description thereof is specific and detailed, but not to be construed as limiting the scope of the present invention. It should be noted that, for those skilled in the art, without departing from the spirit of the present invention, several variations and modifications can be made, which are within the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims

1. A DLP projector capable of enhancing contrast, characterized in that: comprising at least one laser light source and at least one light modulator, said laser light source generating a light beam to illuminate the light modulator, each laser light source consisting of a plurality of lasers, each laser light source emitting light having at least two wavelengths, the laser providing the wavelength with the higher contrast being placed in a position producing a higher F-number and the laser providing the wavelength with the lower contrast being placed in a position producing a lower F-number.

2. A contrast-enhanced DLP projector as claimed in claim 1, wherein: all lasers of each laser light source are distributed in an array mode, and the contrast corresponding to the wavelength of the lasers at the periphery of the array is smaller than the contrast corresponding to the wavelength of the lasers close to the center of the array.

3. A contrast-enhanced DLP projector as claimed in claim 1, wherein: the size of the pixels or pixel pitch of the light modulator is selected to increase the contrast.

4. A contrast-enhanced DLP projector as claimed in claim 1, wherein: for a single primary color with two wavelengths, green is chosen.

5. A DLP projector as claimed in claim 4 wherein said image sensor is further configured to: the wavelength of green is 520-570 nm.

6. A contrast-enhanced DLP projector as claimed in claim 1, wherein: for two primary colors with two wavelengths, green and red are chosen.

7. A contrast-enhancing DLP projector as claimed in claim 6, wherein: the green wavelength is selected to be 520-570nm, and the red wavelength is selected to be 570-700 nm.

8. A contrast-enhanced DLP projector as claimed in claim 1, wherein: the laser also comprises a synchronous control system for adjusting the power of the laser light source, and the intensity of the light emitted by the laser is controlled in a pulse width modulation mode.

9. A contrast-enhanced DLP projector as claimed in claim 8, wherein: the synchronization control system includes: an image processing device, a logic control device, a light modulator and a light source drive;

the logic control device is used for controlling the DMD device of the optical modulator to be switched between an open state and a closed state between two adjacent frame synchronization signals;

the logic control device is also used for controlling the light source drive according to the frequency of the frame synchronization signal so as to adjust the frequency and the phase difference of the output waveform of the laser light source, so that the frequency of the output waveform of the laser light source is consistent with the frequency of the frame synchronization signal, a short-term high pulse signal in the output waveform of the laser light source is in the off-state time period of the DMD device, and the on-state time period of the DMD device is in a long-term constant low signal of the output waveform of the light source;