CN114488674B - Projection optical system and offset adjustment method thereof - Google Patents

Abstract

The present invention provides a projection optical system and its color cast adjustment method. The projection optical system includes: a light source, a light guiding device and a light modulator. The light guiding device divides the outgoing light from the light source into multiple paths and guides them to the light modulator respectively. ; The first light guiding device divides the outgoing light into the red primary color light emitted along the first optical path and the second light emitted along the second optical path; the second light guiding device divides the second light into green primary color light emitted along the third optical path and The blue primary color light emitted along the fourth optical path; the first, second and third light modulators are placed on the first, third and fourth optical path respectively, and modulate the red, green and blue primary color light. According to the spectral characteristics of the light source of the projection system, the present invention separates the red primary color light from the outgoing light firstly, solves the problem of color cast in the white field picture, and makes the color uniformity of the projection optical system good.

Description

Projection optical system and method for adjusting color cast

This application is a divisional application with application number 201811018151.4, application date September 3, 2018, and titled projection optical system and its color cast adjustment method.

technical field

The present invention relates to the field of optical technology, in particular to the field of projection and lighting technology, and relates to a projection optical system with better color uniformity and a color cast adjustment method thereof, in particular to a projection optical system and a color cast adjustment method thereof.

Background technique

In the existing projection optical system, the light source emits white illumination light, which is divided into R, G, and B three-color light by the dichroic film after entering the optical-mechanical system. An image is obtained after the device and the lens.

Because the dichroic film can reflect light of a certain wavelength and transmit light of another wavelength, it can separate the light of different wavelengths. In the prior art, the dichroic film is generally provided with light-splitting ability by means of coating. Due to the characteristics of the coating, when the incident angle of the beam is different, the transmission/reflection spectral characteristics of the dichroic film for the beam will also change. Will drift to the shortwave direction.

Usually, in the optical path, when the main optical axis of the light beam emitted by the object plane is incident on the image plane in parallel, it is called a telecentric optical path; if it is not incident in parallel to the image surface, it is called a non-telecentric optical path. In the projection optical system, when the dichroic film is placed in the non-telecentric illumination light path, there will be differences in the transmission/reflection spectra of different areas due to the different beam incident angles in different areas. When the light source spectrum is wide, the dichroic The spectral components of the transmitted/reflected light in different areas of the color chip will be different, resulting in inconsistent colors on both sides of the screen. For example, if we take a typical three-chip LCD projection system as an example, when projecting a white field image, the left side of the screen will appear blue, and the right side will appear reddish.

Existing projection light sources can be mainly divided into bulb light sources such as xenon lamps, UHP lamps (ultra-high pressure mercury bulbs), LED light sources, pure laser light sources and laser fluorescent light sources. Fig. 1 to Fig. 4 are the luminescence spectrum diagrams of the existing light bulb light source 1000, LED light source, pure laser light source and laser fluorescent light source 9000 respectively, and their respective luminescence spectra are shown in Fig. 1 to Fig. 4 . It should be noted that, as shown in Figure 3, no matter whether it is a blue laser light source 6000, a green laser light source 7000, or a red laser light source 8000, since the spectrum of a pure laser light source is very narrow, it is not discussed in the problem to be solved by the present invention among. Bulb light source 1000 as shown in Figure 1, blue LED light source 2000, green LED light source 3000, red LED light source 4000 and converted green LED light source 5000 as shown in Figure 2, and laser fluorescent light source as shown in Figure 4 9000, due to their wide luminescence spectrum, there are spectral components in the spectral position where the transmittance/reflectance of the dichroic plate changes, so when it is applied to the projection optical system of the present invention, it will produce the unavoidable problem of color cast in the picture .

In the actual use of the projection system, the problem of color cast is usually not noticeable in the process of playing video, but it is especially obvious for office, teaching and other usage scenarios where white screens are the mainstay.

Usually, in the design of this kind of optical system, this problem will be corrected by gradient coating on the dichroic plate, that is, different regions of the dichroic plate are coated with films with different characteristics, so as to To correct the influence caused by different incident angles. In actual production, due to the influence of tolerances, it is often difficult for this gradient coating to accurately compensate for the color cast caused by different incident angles. Therefore, this type of projection system cannot avoid slight color cast problems. At the same time, this kind of dichroic film with gradient coating will also increase the cost. The more accurate the change gradient is, the higher the cost will be.

Contents of the invention

The technical problem to be solved by the present invention is to provide a projection optical system and its color cast adjustment method in view of the deficiencies of the prior art. According to the spectral characteristics of the light source of the projection system, the present invention separates the red primary color light from the outgoing light first, The problem of color cast in the white field picture is solved, and the color uniformity of the projection optical system is improved.

The technical problem to be solved by the present invention is achieved through the following technical solutions:

A projection optical system, comprising: a light source, a light guiding device, a light modulator,

The light source is used to emit light that includes at least three primary colors;

The light guiding device divides the outgoing light into multiple paths and guides them to the light modulators respectively;

The light guide includes a first light guide and a second light guide, and the light modulator includes a first light modulator, a second light modulator, and a third light modulator;

The first light guiding device divides the emitted light into red primary color light emitted along the first optical path and second light emitted along the second optical path, and the second light is other light except the red primary color light in the emitted light Primary color light;

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

The first light modulator is placed on the first optical path to modulate the red primary color light;

The second light modulator is placed on the third light path to modulate the green primary color light;

The third light modulator is placed on the fourth light path to modulate the blue primary color light.

The present invention also provides a method for adjusting color cast of a projection optical system, comprising the following steps:

Step 100: make the outgoing light from the light source including at least three primary colors be sequentially divided into red primary color light, green primary color light and blue primary color light emitted along different optical paths under the action of the light guiding device;

Step 200: The red, green, and blue primary color lights are respectively modulated by the first, second, and third light modulators, and then converged and emitted by a light-combining prism, wherein, before entering the light modulator, the The light path traveled by the blue primary color light is the longest.

In summary, the present invention provides a projection optical system and its color cast adjustment method. According to the spectral characteristics of the light source of the projection system, when the outgoing light including the three primary colors passes through the first light guiding device, the red primary color light It is separated from the outgoing light first, and before the three primary color lights enter the light modulator, the light path of the blue primary color light is the longest, so that the directions of the red primary color picture and the green primary color picture are consistent, and the white field picture is solved. The color uniformity of the projection optical system is good; when the blue image frame is modulated, the blue primary color light is supplemented by the green primary color light to improve the color of the blue display screen to obtain a better display effect .

The technical solution of the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Description of drawings

Fig. 1 is the luminescence spectrum diagram of existing light bulb light source;

Fig. 2 is the luminescence spectrum diagram of existing LED light source;

Fig. 3 is the luminescence spectrum diagram of existing pure laser light source;

Fig. 4 is the luminescence spectrum diagram of existing laser fluorescent light source;

5 is a schematic diagram of the projection optical system of the present invention;

FIG. 6 is a diagram of the light source spectrum and projected spectrum of the system in FIG. 5 .

Explanation of reference signs

201 Positive lens 202 First dichroic film 203 Second dichroic film 204 First relay lens 205 Mirror 206 Second relay lens 207 Field mirror 208 Spatial light modulator 209 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 Fluorescent Light Source

Detailed ways

In general, the present invention provides a projection optical system, including: a light source, a light guiding device, and a light modulator, wherein the light source is used to emit at least three primary colors of red, green and blue outgoing light; the light guiding device The outgoing light is divided into multiple paths and guided to the light modulator respectively; the light guiding device includes a first light guiding device and a second light guiding device, and the light modulator includes a first light modulator, a second light guiding device light modulator and a third light modulator. Specifically, the first light guiding device divides the emitted light into red primary light emitted along the first optical path and second light emitted along the second optical path, and the second light is the red color removed from the emitted light. the other primary color light of the primary color light; the second light guiding device divides the second light into the green primary color light emitted along the third optical path and the blue primary color light emitted along the fourth optical path; the first light modulator sets On the first light path, the red primary color light is modulated; the second light modulator is placed on the third light path, and the green primary color light is modulated; the third light modulator is placed on the On the fourth optical path, the blue primary color light is modulated.

In order to ensure that the primary color lights of red, green and blue respectively enter the corresponding light modulators, and make the light path passed by each primary color light better, the projection optical system also includes at least two reflective components, which are respectively the first reflective component and a second reflective assembly, each reflective assembly may include one, two, three, or a plurality of reflective mirrors; the first reflective assembly is arranged on the first optical path for performing the red primary color light reflect so that it enters the first light modulator; the second reflective assembly is placed on the fourth optical path for reflecting the blue primary color light so that it enters the third light modulator .

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

In order to achieve a better display effect, the filter cut-off range of the second dichroic film is in the range of 465-495 nm, that is to say, the color separation wavelength range of the second dichroic film is 465-495 nm. Please combine with Figure 6, T2 is the transmission line of the second dichroic film, all light in the wavelength range of less than 465nm can pass through the second dichroic film, and all light in the wavelength range of greater than 495nm is transmitted by the second dichroic film reflection. Preferably, the dichroic wavelength range of the second dichroic plate is 475-485nm.

Embodiment one

FIG. 5 is a schematic diagram of the projection optical system of the present invention. As shown in FIG. 5 , the technical solution of the present invention is described in detail in combination with specific embodiments. In this embodiment, a projection optical system is provided, including a light source, a dichroic plate, a reflector, a light modulator, and a light combining prism 209 . The dichroic film is one of the light guiding devices mentioned above. In practical applications, in addition to using the dichroic film as the light guiding device, you can also use filters, area diaphragms, etc. other optical components inside to guide the light. In the embodiment shown in FIG. 5 , the dichroic film includes a first dichroic film 202 and a second dichroic film 203 . In order to ensure that the separated red, green and blue primary color lights respectively enter the corresponding light modulators, the projection optical system further includes a plurality of reflection components, specifically: the reflection mirror 205 in FIG. 5 . Since it is necessary to modulate primary color lights of different colors, the light modulator also includes a first light modulator 208, a second light modulator 208' and a third light modulator 208", which are respectively arranged in different colors The light path of the primary color light. In addition, in order to achieve better display effect, in addition to the above-mentioned main components and parts, the projection optical system also includes a positive lens 201 arranged between the light source and the light guide device, which is used to align the light source The outgoing beams are converged; a field lens 207 arranged in front of the light modulator is also included for adjusting the beams and the like.

As shown in Figure 5, in the projection optical system provided by the present invention, the optical path of the light and the adjustment process to the color cast are realized through the following methods and processes:

The outgoing light emitted by the light source, including at least the three primary colors of red, green and blue, passes through the first dichroic plate 202, and the outgoing light is divided into red primary color light emitted along the first optical path and primary color light emitted along the second optical path. second light. The first optical path refers to the optical path in the vertical direction branched from the first dichroic film 202 in FIG. 5 , and the second optical path refers to the optical path in the horizontal direction in FIG. 5 . At this time, the second light emitted along the second optical path through the first dichroic film 202 includes other primary color lights except the red primary color light in the outgoing light. The second dichroic film 203 divides the second light into green primary color light emitted along the third optical path and blue primary color light emitted along the fourth optical path. Wherein the third optical path refers to the optical path in the vertical direction branched from the second dichroic film 203 in FIG. 5 , and the fourth optical path refers to the optical path in the horizontal direction in FIG. 5 . The light modulator also includes a first light modulator 208, a second light modulator 208', and a third light modulator 208", which are respectively arranged on the light paths of different primary color lights. Specifically, the first The light modulator 208 is placed on the first optical path to modulate the red primary color light; the second light modulator 208' is placed on the third optical path to modulate the green primary color light; The third light modulator 208" is placed on the fourth light path to modulate the blue primary color light. Before entering the light modulator, the light path traveled by the blue primary color light is the longest.

Furthermore, in order to ensure that the primary color lights of red, green and blue respectively enter the corresponding light modulators, the projection optical system further includes a plurality of reflective components, that is, reflective mirrors 205 shown in FIG. 5 . In the entire projection optical system, a reflector 205 is arranged on the first optical path for reflecting the red primary color light so that it enters the first light modulator 208; the other two reflectors 205 are respectively placed at different positions on the fourth light path, for reflecting the blue primary color light to enter the third light modulator 208".

That is to say, after the outgoing light from the light source is decomposed into three-color illumination light by two dichroic plates, after passing through the reflector 205 and different light modulators respectively, the light is combined in the light combining prism 209, according to the light path In the order of transmission, the first dichroic sheet 202 reflects the blue primary color light and transmits the green primary color light and the red primary color light, and the second dichroic sheet 203 reflects the green primary color light and transmits the red primary color light. In order to converge the light beams emitted by the light source, a positive lens 201 is provided between the light source and the first dichroic film 202 . Further, in order to shorten the optical distance by forming an intermediate image, the blue primary color light transmitted from the second dichroic film 203 passes through the first relay lens 204 and the second relay lens 206 in sequence, and passes through the An intermediate image makes the image formed by the blue primary color light on the spatial light modulator and the red and green primary color light reversed from left to right. The red primary color light and the blue primary color light enter the light modulator 208 through the mirror 205, and the light modulator 208 can be LCD, LCOS or DMD. Furthermore, in order to adjust the light beam, the light incident front end of the light modulator 208 is provided with a field lens 207 .

It can be seen from the above that in the projection optical system provided by the present invention, two dichroic plates are usually used to divide the outgoing light from the light source into three primary colors of R (red), G (green), and B (blue), However, when the dichroic film is placed in the non-telecentric light path, it will cause the problem of color cast on both sides of the final projected picture, especially in the all-white picture, that is: white field, the color cast is particularly obvious.

When the red, green, and blue primary colors are imaged in the same direction on the spatial light modulator, even if the dichroic film does not compensate for the color cast caused by the angle of the incident light, it will only cause red, green, and blue fields. For their own color cast, when projecting a white field picture, there will be no color cast due to the superimposition of the red, green, and blue primary color light spectra. However, since the imaging of the red primary color light path is reversed, the color cast problem is superimposed and magnified in the white scene, so as long as there is a small amount of offset in the dichroic film without compensation, it will also cause a noticeable cast in the white scene. color problem.

It should be noted that the "imaging of the red primary color light path is reversed" as mentioned above specifically refers to: in the imaging light path, a point on the left side of the object plane passes through the blue primary color light optical path, the green primary color light After the optical path, it is imaged to the left side of the image plane (which can be understood as the actual projection screen), and after passing through the red primary color light path, it is imaged to the right side of the image plane. At this time, the imaging of the red primary color light is relative to the blue primary color Light and green primary color light are reversed. In this embodiment, the concept of positive image and reverse image is not emphasized, but the difference between red primary color light, blue primary color light, and green primary color light is emphasized, because this difference leads to the problem of uneven color of the picture. In the prior art, the reason why the red primary color light is reversed is because the light path of the red primary color light is relatively long when it is finally separated, and it needs to pass through the first relay lens 204 and the second relay lens 204 on the optical path. The lens 206 and the field lens 207 form an image one more time, causing it to be opposite to the direction of the blue primary color light and the green primary color light.

In the present invention, when the outgoing light is incident on the first dichroic film 202, the red primary color light is first separated, which can shorten the optical path of the red primary color light, and does not require multiple imaging through the relay lens, and will not cause red The imaging of the primary color light is reversed. The invention is adjusted so that the optical path of the blue primary color light is the longest, and the direction of the formed image is opposite to that of the red primary color light and the green primary color light, but this does not cause the problem of color cast. As shown in Figure 6, the specific reason is that due to the spectral characteristics of the laser fluorescent light source, the wavelengths of the blue laser light source 6000 and the laser fluorescent light source 9000 have an interval of 20-30nm in the spectrum, and the present invention skillfully divides the second two-way The color separation wavelength of the color film is set within this interval, even if the spectral transmission line shifts due to the angle difference of the incident light, since the light source has no spectral components within this interval, there will be no color cast on the projection screen The problem. Specifically, the value of the color separation wavelength of the second dichroic plate can be set at 465nm-495nm, preferably at 475nm-485nm.

The projection optical system provided by the present invention first separates the red primary color light from the outgoing light, and before the three primary color lights enter the light modulator, the blue primary color light has the longest optical path, that is to say, the red and blue The optical path of the color base color light is exchanged, so that the directions of the red base color picture and the green base color picture are consistent, which can suppress the color cast problem of the white field picture in principle. The color cast of the monochrome picture still needs to be compensated by the dichroic film with gradient coating, but the problem of color cast in the white field is eliminated, and the viewing experience will be much better. At the same time, the accuracy requirements for the coating gradient are also required. Corresponding relaxation can reduce costs.

Embodiment two

On the basis of the first embodiment above, after the red and blue primary color optical paths are exchanged, and the color separation wavelength of the dichroic plate is set in the interval between the blue laser and the fluorescent spectrum, a problem that may be caused is that the projection The B (blue) primary color light on the screen is all blue laser light. Generally, the selectable wavelength of blue laser is between 445nm-465nm, selects the blue laser of short wavelength, is more conducive to the problem to be solved by the present invention, because blue laser and fluorescence are wider on the spectrum interval; But it is generally considered that 465nm The blue base color light color will be better.

In order to make the display effect of the blue picture better, it is necessary to add a small amount of green primary color light to the blue primary color light when modulating the blue image frame. The addition of a small amount of green primary color light can be controlled by the control device. Specifically, when modulating a blue image frame, the control device controls the blue primary color light to enter the third light modulator 208" for modulation, and at the same time controls part of the green primary color light to enter the second light modulator for modulation 208 ', that is to say, the picture displayed by the blue image frame is the superposition of the modulation of the blue primary color light by the third light modulator and the modulation of a small amount of green primary color light by the second light modulator. In the blue image During modulation, the gray scale value of the blue primary color light is required to be greater than the gray scale value of part of the green primary color light. When the second light modulator modulates the light, the control device controls the part of the green primary color light according to the modulation signal of the blue primary color light. amount of light.

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

Therefore, the difference between this embodiment and Embodiment 1 is that the projection optical system further includes a supplementary light source for emitting green primary color light. When modulating the blue image frame, the added small amount of green primary color light can be provided by the supplementary light source.

Specifically, the supplementary G (green primary color light) signal is related to the B (blue primary color light) signal. In principle, it is better to obtain a color (color coordinate) with blue primary color light + a small amount of supplementary green primary color light The B light shall prevail, and the color coordinates may refer to DCI, Rec.709 and other color gamuts. When the B signal is relatively small, the required green primary color light will be less than the green primary color light of 1 gray scale, resulting in the inability to supplement the green primary color light. The color is not very sensitive; when the B (blue primary color light) signal is large, this scheme can be used to add a certain amount of green to the blue primary color light to achieve a better color for the overall B primary color light.

For the embodiment in which the green primary color light is supplemented to improve the color of the blue primary color light, the grayscale ratio of the required blue primary color light to the green primary color light needs to satisfy a range. In this range, the blue color is considered to be obtained. Improvement; beyond this range it is either greenish or bluish; an optional ratio range is 100-255. Then when the B (blue primary color light) signal is relatively small, for example: when there are 10 gray levels, it is necessary to add at least 1 gray level green primary color light. At this time, the ratio of blue/green is small, and the mixed color Will be greenish.

Due to the addition of supplementary light sources, when modulating a green image frame, the control device may 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. Thereby, the display color gamut of the image can be expanded.

To sum up, the present invention provides a projection optical system and its color cast adjustment method. According to the spectral characteristics of the light source of the projection system, the positions of the red light path and the blue light path are exchanged, which solves the problem of color cast in the white field picture and makes the projection The color uniformity of the optical system is good; and by supplementing the green primary color light to the blue primary color light, the color of the blue field is improved to obtain a better display effect.

Claims (10)

1. A projection optical system, comprising: a light source, a light guiding device, a light modulator, The light source is used to emit outgoing light including at least three primary colors, and the spectral characteristic of the light source is that there is an interval in the spectrum between the blue primary color light and the wavelength of laser fluorescence; The optical path where the outgoing light of the light source is located is a non-telecentric optical path; It is characterized by: The light guiding device includes a first light guiding device and a second light guiding device, the first light guiding device divides the emitted light into red primary color light emitted along a first optical path and second light emitted along a second optical path , the second light is the other primary color light except the red primary color light in the outgoing light, and the second light guiding device divides the second light into the green primary color light emitted along the third optical path and the green primary color light emitted along the fourth optical path the blue primary color light, the dichroic wavelength of the second light guiding device is set within the interval; The light modulator includes a first light modulator, a second light modulator, and a third light modulator, the first light modulator is placed on the first light path, and modulates the red primary color light, so The second light modulator is placed on the third optical path to modulate the green primary color light, and the third light modulator is placed on the fourth optical path to modulate the blue primary color light; Wherein, before the three primary colors enter the light modulator, the light path of the blue primary color light is the longest. 2. The projection optical system according to claim 1, wherein: The projection optical system also includes a first reflective assembly and a second reflective assembly; The first reflective component is disposed on the first optical path, and is used to reflect the red primary color light so that it enters the first light modulator; The second reflective component is placed on the fourth optical path for reflecting the blue primary color light to enter the third light modulator. 3. The projection optical system according to claim 1, wherein: The first light directing means includes a first dichroic plate and the second light directing means includes a second dichroic plate. 4. The projection optical system according to claim 3, wherein the dichroic wavelength range of the second dichroic plate is 465-495 nm. 5. The projection optical system according to claim 1, wherein the light source further comprises a control device, and when the blue image frame is modulated, the control device controls the blue primary color light to enter the third The light modulator performs modulation, and at the same time controls part of the green primary color light to enter the second light modulator for modulation. 6. The projection optical system according to claim 5, further comprising a supplementary light source for emitting green primary color light, the part of the green primary color light is provided by the supplementary light source. 7 . The projection optical system according to claim 5 , wherein when the blue image frame is modulated, the ratio range of the grayscale values of the blue primary color light and the green primary color light is: 100 to 255. 8. The projection optical system according to claim 6, wherein when the green image frame is modulated, the control device controls the primary green light emitted by the light source and the primary green light emitted by the supplementary light source into the second light modulator for modulation. 9. The projection optical system according to claim 1, wherein the interval is 20-30 nm. 10. A method for adjusting color cast of a projection optical system as claimed in any one of claims 1-9, wherein the light path where the outgoing light of the light source is located is a non-telecentric light path, and the spectral characteristics of the light source are blue primary color light and The wavelength of the laser fluorescence has an interval in the spectrum, and it is characterized in that it includes the following steps: Step 100: make the outgoing light from the light source including at least three primary colors be sequentially divided into red primary color light, green primary color light and blue primary color light emitted along different optical paths under the action of the light guiding device; Step 200: The red, green, and blue primary color lights are respectively modulated by the first, second, and third light modulators, and then converged and emitted by a light-combining prism, wherein, before entering the light modulator, the The light path of the blue primary color light is the longest; Wherein, the step 100 specifically includes: The light guide comprises a first light guide and a second light guide; The light modulators include a first light modulator, a second light modulator, and a third light modulator; The first light guiding device divides the emitted light into red primary color light emitted along the first optical path and second light emitted along the second optical path, and the second light is other light except the red primary color light in the emitted light Primary color light; The second light guide device divides the second light into green primary color light emitted along the second optical path and blue primary color light emitted along the third optical path, and the color separation wavelength of the second light guide device is set at the within the interval; a first light modulator placed on the first optical path to modulate the red primary color light; a second light modulator placed on the second light path to modulate the green primary color light; The third light modulator placed on the third optical path modulates the blue primary color light.

Images