CN114488674B

CN114488674B - Projection optical system and offset adjustment method thereof

Info

Publication number: CN114488674B
Application number: CN202210070646.1A
Authority: CN
Inventors: 王则钦; 杨炳柯; 郭祖强; 李屹
Original assignee: Appotronics Corp Ltd
Current assignee: Shenzhen Appotronics Corp Ltd
Priority date: 2018-09-03
Filing date: 2018-09-03
Publication date: 2023-07-07
Anticipated expiration: 2038-09-03
Also published as: CN110874003B; CN110874003A; CN114488674A; WO2020048099A1

Abstract

The invention provides a projection optical system and a color cast adjusting method thereof, wherein the projection optical system comprises: the light guide device divides emergent light emitted by the light source into multiple paths and guides the multiple paths of emergent light to the light modulator respectively; the first light guiding device divides the emergent light into red primary light emergent along a first light path and second light emergent along a second light path; the second light guiding device divides the second light into green primary light emitted along the third light path and blue primary light emitted along the fourth light path; the first, second and third light modulators are disposed on the first, third and fourth light paths, respectively, and modulate the red, green and blue primary lights. According to the spectral characteristics of the light source of the projection system, the invention enables the red primary color light to be separated from the emergent light first, solves the problem of white field picture color cast, and ensures that the color uniformity of the projection optical system is good.

Description

Projection optical system and offset adjustment method thereof

The application is as follows: the application number is 201811018151.4, the application date is 2018, the application date is 09, and the application date is 03, and the application is a division application of a projection optical system and a color cast adjustment method thereof.

Technical Field

The invention relates to the technical field of optics, in particular to the technical field of projection and illumination, in particular to a projection optical system with good color uniformity and a color cast adjustment method thereof, and especially relates to a projection optical system and a color cast adjustment method thereof.

Background

In the existing projection optical system, a light source emits white illumination light, the white illumination light enters an optical-mechanical system and is divided into R, G, B three-color lights by a dichroic plate, the three-color lights respectively illuminate on a spatial light modulator, and an image is obtained after passing through a light combining device and a lens.

Since the dichroic plate is capable of reflecting light of a certain wavelength, light of another wavelength is transmitted, thereby separating light of a different wavelength. The dichroic sheet is typically provided with a light splitting capability by means of a coating in the prior art. Due to the characteristics of the coating film, when the incidence angles of the light beams are different, the transmission/reflection spectrum characteristics of the dichroic plate for the light beams are also changed, and a general rule is that the incidence angle of the light beams is increased, and the transmission/reflection spectrum line of the dichroic plate is shifted to the short wave direction.

In general, in the optical path, when the main optical axis of the light beam emitted from the object plane is parallel to the image plane, the light path is called a telecentric optical path; and is referred to as a non-telecentric optical path if it is not parallel incident to the image plane. In the projection optical system, when the dichroic plate is placed in the non-telecentric illumination light path, there is a difference in the transmission/reflection spectra of different regions due to the difference in the incidence angle of the light beams of different regions, and when the spectrum of the light source is wide, the spectral components of the light transmitted/reflected by different regions of the dichroic plate are different, thereby causing color inconsistency on both sides of the picture. Such as: if a typical three-LCD projection system is taken as an example, when a white field picture is projected, the picture will have the problems of green shift on the left and red shift on the right.

The existing projection light sources can be mainly divided into bulb light sources such as xenon lamps, UHP lamps (ultra-high pressure mercury lamps) and the like, LED light sources, pure laser light sources and laser fluorescent light sources. Fig. 1 to 4 are emission spectra of a conventional bulb light source 1000, an LED light source, a pure laser light source, and a laser fluorescent light source 9000, respectively, and their respective emission spectra are shown in fig. 1 to 4. As shown in fig. 3, the spectrum of the pure laser light source is narrow, and thus the blue laser light source 6000, the green laser light source 7000, or the red laser light source 8000 is not discussed as the problem to be solved by the present invention. The bulb light source 1000 shown in fig. 1, the blue LED light source 2000, the green LED light source 3000, the red LED light source 4000 and the converted green LED light source 5000 shown in fig. 2, and the laser fluorescent light source 9000 shown in fig. 4, because of their wide emission spectrum, have spectral components at spectral positions where the dichroic plate transmittance/reflectance varies, and thus, when applied to the projection optical system of the present invention, cause an unavoidable problem of screen color shift.

In practical use of the projection system, the problem of color cast is usually not influenced in a perceived way in the process of playing video, but is particularly obvious for use scenes mainly comprising white pictures, such as offices, teaching and the like.

In general, in the design of such an optical system, the problem is corrected by gradient coating the dichroic plate, namely: different areas of the dichroic plate are coated with films of different characteristics, so as to correct the effect caused by different incident angles. In practical production, due to tolerance, it is often difficult to accurately compensate for color shift caused by different incident angles, so that this type of projection system cannot avoid slight color shift. Meanwhile, the dichroic plate coated with the gradient film can bring cost improvement, and the more accurate the gradient is, the higher the cost is.

Disclosure of Invention

The invention aims to solve the technical problems of the prior art and provides a projection optical system and a color cast adjusting method thereof.

The technical problems to be solved by the invention are realized by the following technical scheme:

a projection optical system, comprising: a light source, a light guiding means, and a light modulator,

the light source is used for emitting emergent light at least comprising three primary colors;

the light guiding device divides emergent light into multiple paths and guides the light to the light modulators respectively;

the light guiding device comprises a first light guiding device and a second light guiding device, and the light modulator comprises a first light modulator, a second light modulator and a third light modulator;

the first light guiding device divides the emergent light into red primary light emergent along a first light path and second light emergent along a second light path, wherein the second light is other primary light except the red primary light in the emergent light;

the second light guiding device divides the second light into green primary light emitted along a third light path and blue primary light emitted along a fourth light path;

the first light modulator is arranged on the first light path and modulates the red primary color light;

the second light modulator is arranged on the third light path and modulates the green primary color light;

the third light modulator is arranged on the fourth light path and modulates the blue primary light.

The invention also provides a color cast adjustment method of the projection optical system, which comprises the following steps:

step 100: the emergent light which is emitted by the light source and at least comprises three primary colors is sequentially divided into red primary color light, green primary color light and blue primary color light which are emergent along different light paths under the action of the light guide device;

step 200: and the red, green and blue primary lights are respectively modulated by the first, second and third light modulators and are converged and emitted by the light combining prism, wherein the light path of the blue primary light is longest before entering the light modulators.

In summary, the present invention provides a projection optical system and a color shift adjustment method thereof, according to the spectral characteristics of a light source of the projection optical system, when the emergent light including three primary colors passes through a first light guiding device, the red primary light is first separated from the emergent light, and before the three primary colors enter a light modulator, the light path through which the blue primary light passes is longest, so that the directions of a red primary color picture and a green primary color picture are consistent, the problem of color shift of a white field picture is solved, and the color uniformity of the projection optical system is good; when the blue image frame is modulated, the color of the blue display picture is improved by supplementing the blue primary light with the green primary light, so that a better display effect is obtained.

The technical scheme of the invention is described in detail below with reference to the accompanying drawings and specific embodiments.

Drawings

FIG. 1 is a diagram of the luminescence spectrum of a conventional bulb light source;

FIG. 2 is a diagram of the luminescence spectrum of a conventional LED light source;

FIG. 3 is a diagram showing the luminescence spectrum of a conventional pure laser light source;

FIG. 4 is a graph of the luminescence spectrum of a conventional laser fluorescent light source;

FIG. 5 is a schematic diagram of a projection optical system according to the present invention;

FIG. 6 is a graph of the spectrum and projected spectrum of the illuminant of the system of FIG. 5.

Description of the reference numerals

201 positive lens 202 first dichroic plate 203 second dichroic plate 204 first relay lens 205 mirror 206 second relay lens 207 field 208 spatial light modulator 209 light combining prism

1000 bulb light source 2000 blue LED light source 3000 green LED light source 4000 red LED light source 5000 converted green LED light source 6000 blue laser light source 7000 green laser light source 8000 red laser light source 9000 laser fluorescence light source

Detailed Description

In general, the present invention provides a projection optical system including: the light source is used for emitting emergent light at least comprising three primary colors of red, green and blue; the light guiding device divides the emergent light into multiple paths and guides the emergent light to the light modulators respectively; the light guiding means comprises a first light guiding means and a second light guiding means, the light modulator comprising a first light modulator, a second light modulator and a third light modulator. Specifically, the first light guiding device divides the emergent light into red primary light emergent along a first light path and second light emergent along a second light path, wherein the second light is other primary light except the red primary light in the emergent light; the second light guiding device divides the second light into green primary light emitted along a third light path and blue primary light emitted along a fourth light path; the first light modulator is arranged on the first light path and modulates the red primary color light; the second light modulator is arranged on the third light path and modulates the green primary light; the third light modulator is arranged on the fourth light path and modulates the blue primary light.

In order to ensure that the red, green and blue primary lights respectively enter the corresponding light modulators and the light path of each primary light is better, the projection optical system further comprises at least two reflecting assemblies, namely a first reflecting assembly and a second reflecting assembly, and each reflecting assembly can comprise one, two, three or more reflecting mirrors; the first reflecting component is arranged on the first light path and is used for reflecting the red primary color light to enter the first light modulator; the second reflecting component is arranged on the fourth light path and is used for reflecting the blue primary color light to enter the third light modulator.

More specifically, the first light guiding means comprises a first dichroic plate and the second light guiding means comprises a second dichroic plate.

In order to achieve better display effect, the filter cut-off range of the second dichroic plate is in the range of 465-495nm, that is, the color separation wavelength range of the second dichroic plate is 465-495nm. Referring to fig. 6, T2 is the transmission line of the second dichroic plate, and light in the wavelength range less than 465nm can be transmitted through the second dichroic plate, and light in the wavelength range greater than 495nm can be reflected by the second dichroic plate. Preferably, the second dichroic plate has a color separation wavelength in the range of 475-485nm.

Example 1

Fig. 5 is a schematic view of a projection optical system according to the present invention. As shown in fig. 5, the technical scheme of the present invention will be described in detail with reference to a specific embodiment. In the present embodiment, there is provided a projection optical system including a light source, a dichroic sheet, a reflecting mirror, a light modulator, and a light combining prism 209. The dichroic sheet belongs to one of the light guiding devices described above, and in practical applications, besides using the dichroic sheet as a light guiding device, other optical components including filters, area films, and the like may be used to guide light. In the embodiment shown in fig. 5, the dichroic plates comprise a first dichroic plate 202 and a second dichroic plate 203. In order to ensure that the separated red, green and blue primary lights respectively enter the corresponding light modulators, the projection optical system further comprises a plurality of reflection components, specifically: mirror 205 in fig. 5. Since light modulation is required for the primary colors of different colors, the light modulators also include a first light modulator 208, a second light modulator 208', and a third light modulator 208″ respectively disposed on the light paths of the different Yan Seji color lights. In addition, in order to achieve a better display effect, besides the above main components, the projection optical system further includes a positive lens 201 disposed between the light source and the light guiding device, for converging the outgoing light beam of the light source; a field lens 207 arranged in front of the light modulator is also included for adjusting the light beam, etc.

As shown in fig. 5, in the projection optical system provided by the present invention, the adjustment process of the light path and the color shift of the light is implemented by the following manner and process:

the outgoing light emitted by the light source, which at least comprises three primary colors of red, green and blue, passes through the first dichroic plate 202, and is split into red primary light outgoing along the first light path and second light outgoing along the second light path. The first light path refers to the light path in the vertical direction in fig. 5, which is branched from the first dichroic plate 202, and the second light path refers to the light path in the horizontal direction in fig. 5. At this time, the second light emitted along the second optical path through the first dichroic plate 202 includes other primary color light excluding the red primary color light among the emitted light. The second dichroic plate 203 separates the second light into green primary color light exiting along the third light path and blue primary color light exiting along the fourth light path. The third light path refers to the light path in the vertical direction that is branched from the second dichroic sheet 203 in fig. 5, and the fourth light path refers to the light path in the horizontal direction in fig. 5. The light modulators also include a first light modulator 208, a second light modulator 208', and a third light modulator 208″ respectively disposed on the light paths of the different Yan Seji colored lights. Specifically, the first light modulator 208 is disposed on the first light path and modulates the red primary color light; the second light modulator 208' is disposed on the third optical path and modulates the green primary color light; the third light modulator 208 "is disposed on the fourth optical path and modulates the blue primary light. The light path through which the blue primary light passes is longest before entering the light modulator.

Still further, in order to ensure that the red, green and blue primary light respectively enter the corresponding light modulators, the projection optical system further comprises a plurality of reflection components, namely: mirror 205 is shown in fig. 5. A mirror 205 is disposed on the first optical path for reflecting the red primary light to enter the first light modulator 208 in the entire projection optical system; two other mirrors 205 are respectively disposed at different positions on the fourth optical path, and are configured to reflect the blue primary light so as to enter the third light modulator 208.

That is, after the light emitted from the light source is decomposed into three-color illumination light by the two dichroic plates, the three-color illumination light is respectively passed through the reflecting mirror 205 and the different light modulators, and then combined by the light combining prism 209, the first dichroic plate 202 reflects the blue primary color light and transmits the green primary color light and the red primary color light according to the transmission order of the optical path, and the second dichroic plate 203 reflects the green primary color light and transmits the red primary color light. In order to collect the light beams emitted from the light source, a positive lens 201 is arranged between the light source and the first dichroic plate 202. Further, in order to shorten the optical path by forming an intermediate image, the blue primary color light emitted from the second dichroic plate 203 sequentially passes through the first relay lens 204 and the second relay lens 206, and then the intermediate image is formed once, so that the image formed on the spatial light modulator by the blue primary color light path is inverted to the red and green primary color light. The red primary light and the blue primary light enter the light modulator 208 via the reflector 205, and the light modulator 208 may be an LCD, LCOS, or DMD. Further, in order to adjust the light beam, a field lens 207 is disposed at the light incident front end of the light modulator 208.

As can be seen from the above, in the projection optical system provided by the present invention, the two dichroic plates are generally used to separate the light emitted from the light source into three primary colors of R (red), G (green) and B (blue), however, when the dichroic plates are placed in the non-telecentric optical path, the color shift problem is caused on both sides of the final projection screen, especially in the full white screen, namely: white fields are particularly obvious in color cast.

When the red, green and blue primary lights are imaged in the same direction on the spatial light modulator, even if the dichroic plate does not compensate the color cast problem caused by the angle of the incident light, the color cast of each of the red, green and blue fields is only caused, and when a white field picture is projected, the color cast is not caused due to the superposition of the spectrums of the red, green and blue primary lights. However, since the imaging of the red primary light path is reversed, the color shift problem is amplified in the white field, so that the dichroic plate can cause a perceived color shift problem in the white field if there is a small amount of offset and no compensation.

It should be noted that, as described above, "imaging of the red primary light path is reversed", specifically, it means: in the imaging light path, a point on the left side of the object plane is imaged to the left side of the image plane (which can be understood as an actual projection picture) after passing through the blue primary light path and the green primary light path, and is imaged to the right side of the image plane after passing through the red primary light path, at this time, the imaging of the red primary light is reversed relative to the blue primary light and the green primary light. In the present embodiment, the concepts of the positive image and the negative image are not emphasized, but the difference between the red primary color light and the blue primary color light, the green primary color light is emphasized, because such difference causes a problem of uneven color of the screen. In the prior art, the red primary color light is reversed because the light path that the red primary color light passes through when it is separated only last time is relatively long, and the light path needs to be imaged once more through the first relay lens 204, the second relay lens 206 and the field lens 207, so that the direction of the red primary color light is opposite to that of the blue primary color light and the green primary color light.

In the present invention, when the outgoing light enters the first dichroic plate 202, the red primary light is first separated, so that the optical path of the red primary light can be shortened, and the problem of reverse imaging of the red primary light is avoided without multiple imaging through the relay lens. The invention is adjusted to make the light path of the blue primary light longest, and the imaging direction is opposite to the imaging direction of the red primary light and the green primary light, but the invention does not cause color cast problem. As shown in fig. 6, the specific reason is that the blue laser light source 6000 and the laser fluorescent light source 9000 have a wavelength of 20-30nm in spectrum due to the spectral characteristics of the laser fluorescent light source, and the present invention skillfully sets the color separation wavelength of the second dichroic plate within this interval, even if the spectral transmission line is shifted due to the angle difference of the incident light, the problem of color shift on the projection screen does not occur because the light source has no spectral component within this interval. Specifically, the second dichroic plate color separation wavelength may be set at a value of 465nm to 495nm, preferably 475nm to 485nm.

The projection optical system provided by the invention separates the red primary light from the emergent light first, and the light path of the blue primary light is longest before the three primary lights enter the light modulator, namely the light paths of the red and blue primary lights are exchanged, so that the directions of the red primary color picture and the green primary color picture are consistent, and the color cast problem of the white picture can be restrained in principle. The color cast of the single-color picture still needs to be compensated by the dichroic plate coated by the gradient, but the color cast problem of the white field is eliminated, the experience in the watching process is much better, and meanwhile, the accuracy requirement on the gradient of the coated film is correspondingly relaxed, so that the cost can be reduced.

Example two

In the first embodiment, after the red and blue primary light paths are switched and the color separation wavelength of the dichroic plate is set in the interval between the blue laser light and the fluorescence spectrum, there is a problem that the B (blue) primary light of the projection screen is all blue laser light. Generally, the wavelength of blue laser is between 445nm and 465nm, and the blue laser with short wavelength is more beneficial to the problem to be solved by the invention because the blue laser and fluorescence have wider interval in the spectrum; but it is generally believed that the color of 465nm blue primary light will be better.

In order to improve the display effect of the blue screen, it is necessary to add a small amount of green primary light to the blue primary light when modulating the blue image frame. The addition of a small amount of green primary light can be controlled by a control device. Specifically, when modulating the blue image frame, the control device controls the blue primary light to enter the third light modulator 208 "to be modulated, and controls part of the green primary light to enter the second light modulator to be modulated 208', that is, the picture displayed by the blue image frame is the superposition of the blue primary light modulated by the third light modulator and the small amount of green primary light modulated by the second light modulator. When modulating a blue image, the gray-scale value of the blue primary light is required to be larger than the gray-scale value of a part of the green primary light, and when modulating the light by the second light modulator, the control device controls the amount of the part of the green primary light according to the modulating signal of the blue primary light.

On the basis of selecting the short-wavelength blue laser, the color of the B primary color light can be compensated by a signal processing mode. For example, for a given blue field signal of one RGB (0, 255), the color of the blue field can be improved by processing one signal changed to RGB (0, 1, 255) with the addition of a small amount of green primary light.

Therefore, the present embodiment is different from the first embodiment in that the projection optical system further includes a supplemental light source for emitting green-based light. When modulating the blue image frame, a small amount of added green primary light may be provided by the supplemental light source.

Specifically, the magnitude of the G (green primary light) signal is related to the magnitude of the B (blue primary light) signal, and in principle, the blue primary light+the small amount of the green primary light added is used to obtain B light with a better color (color coordinates), which can refer to the color gamut such as DCI, rec.709, and the like. When the B signal is smaller, the required green primary color light is smaller than 1 gray-scale green primary color light, so that the green primary color light cannot be supplemented, but at the moment, the brightness of B (blue primary color light) is lower, and human eyes are not sensitive to the colors of the B (blue primary color light); when the B (blue primary color light) signal is larger, a certain green can be supplemented in the blue primary color light through the scheme, so that the better color of the whole B primary color light can be achieved.

For embodiments that supplement the green primary light to improve the color of the blue primary light, the ratio of the gray levels of the blue primary light and the green primary light is required to satisfy a range in which the color of blue is considered to be improved; out of this range either greenish or blue; an alternative ratio range is 100-255. Then when the B (blue primary light) signal is small, such as: at 10 gray levels, at least 1 gray level of green primary light needs to be added, and at this time, the ratio of blue to green is small, and the mixed color is greenish.

Due to the addition of the supplementary light source, when the green image frame is modulated, the control device can control the green primary light emitted by the light source and the green primary light emitted by the supplementary light source to enter the second light modulator for modulation. So that the display gamut of the image can be enlarged.

In summary, the present invention provides a projection optical system and a color shift adjustment method thereof, which change the positions of a red light path and a blue light path according to the spectral characteristics of a light source of the projection optical system, so as to solve the problem of color shift of a white field picture, and make the color uniformity of the projection optical system good; and the blue color is improved by supplementing the blue primary color with the green primary color light, so as to obtain better display effect.

Claims

1. A projection optical system, comprising: a light source, a light guiding means, and a light modulator,

the light source is used for emitting emergent light at least comprising three primary colors, and the spectral characteristics of the light source are that the wavelengths of blue primary color light and laser fluorescence are spectrally separated;

the light path of the emergent light of the light source is a non-telecentric light path;

the method is characterized in that:

the light guiding device comprises a first light guiding device and a second light guiding device, wherein the first light guiding device divides the emergent light into red primary light emergent along a first light path and second light emergent along a second light path, the second light is other primary light except the red primary light in the emergent light, the second light guiding device divides the second light into green primary light emergent along a third light path and blue primary light emergent along a fourth light path, and color separation wavelengths of the second light guiding device are arranged in the interval;

the light modulator comprises a first light modulator, a second light modulator and a third light modulator, wherein the first light modulator is arranged on the first light path and modulates the red primary color light, the second light modulator is arranged on the third light path and modulates the green primary color light, and the third light modulator is arranged on the fourth light path and modulates the blue primary color light;

wherein the light path through which the blue primary light passes is longest before the three primary colors enter the light modulator.

2. The projection optical system of claim 1, wherein,

the projection optical system further comprises a first reflection assembly and a second reflection assembly;

the first reflecting component is arranged on the first light path and is used for reflecting the red primary color light to enter the first light modulator;

the second reflecting component is arranged on the fourth light path and is used for reflecting the blue primary color light to enter the third light modulator.

3. The projection optical system of claim 1, wherein,

the first light directing means comprises a first dichroic plate and the second light directing means comprises a second dichroic plate.

4. The projection optical system of claim 3 wherein the second dichroic plate has a color separation wavelength in the range of 465-495nm.

5. The projection optical system according to claim 1, wherein the light source further comprises a control device that controls the blue primary light to enter the third light modulator to be modulated while controlling a part of the green primary light to enter the second light modulator to be modulated when modulating a blue image frame.

6. The projection optical system of claim 5 further comprising a supplemental light source for emitting green primary light, the portion of green primary light being provided by the supplemental light source.

7. The projection optical system according to claim 5, wherein when the blue image frame is modulated, a ratio range of gray-scale values of the blue primary light and the green primary light is: 100 to 255.

8. The projection optical system according to claim 6, wherein the control device controls the green primary light emitted from the light source and the green primary light emitted from the supplemental light source to enter the second light modulator for modulation when modulating a green image frame.

9. The projection optical system of claim 1 wherein the spacing is 20-30nm.

10. A color shift adjustment method of a projection optical system according to any one of claims 1 to 9, wherein an optical path in which outgoing light of a light source is located is a non-telecentric optical path, and spectral characteristics of the light source are that wavelengths of blue primary light and laser fluorescence are spectrally separated, comprising the steps of:

step 200: the red, green and blue primary lights are respectively modulated by the first, second and third light modulators and then are converged and emitted by the light combining prism, wherein the light path of the blue primary light is longest before entering the light modulators;

the step 100 specifically includes:

the light guiding means comprises first and second light guiding means;

the optical modulator comprises a first optical modulator, a second optical modulator and a third optical modulator;

the second light guiding device divides the second light into green primary light emitted along a second light path and blue primary light emitted along a third light path, and color separation wavelengths of the second light guiding device are arranged in the interval;

a first light modulator disposed on the first optical path for modulating the red primary color light;

a second light modulator disposed on the second optical path for modulating the green primary color light;

and a third light modulator disposed on the third light path for modulating the blue primary color light.