CN109729327B

CN109729327B - Image display method, device and system

Info

Publication number: CN109729327B
Application number: CN201711047913.9A
Authority: CN
Inventors: 董玉珍
Original assignee: Hisense Visual Technology Co Ltd
Current assignee: Hisense Visual Technology Co Ltd
Priority date: 2017-10-31
Filing date: 2017-10-31
Publication date: 2022-01-28
Anticipated expiration: 2037-10-31
Also published as: CN109729327A

Abstract

The embodiment of the invention provides an image display method, an image display device and an image display system, which are applied to a projection system, wherein the projection system comprises projection equipment, a display screen and a first optical sensor, the projection equipment is used for projecting a preset image to the display screen, and the method comprises the following steps: acquiring an optical signal received by a first optical sensor, wherein the optical signal is a signal reflected to the first optical sensor when a display screen displays a preset image; the method comprises the steps of obtaining the maximum reflection brightness, the minimum reflection brightness and the white field color coordinate of a display screen under the maximum reflection brightness according to an optical signal received by a first optical sensor, and adjusting image quality parameters of the projection equipment according to the maximum reflection brightness, the minimum reflection brightness and the white field color coordinate of the display screen, wherein the image quality parameters comprise at least one of a white balance coefficient, the purity of a preset color point and the brightness corresponding to each gray scale. The method is used for improving the adjustment efficiency of the image quality parameters.

Description

Image display method, device and system

Technical Field

The embodiment of the invention relates to the technical field of projection, in particular to an image display method, device and system.

Background

Nowadays, projection systems are increasingly used, wherein the projection systems may comprise laser projection systems and the like, for example, the laser projection systems may be laser televisions, laser projectors and the like.

The projection system generally includes a projection device and a display screen, and during operation of the projection system, light emitted from the projection device is projected onto the display screen, and a picture is presented on the display screen. In an actual application process, in order to improve the flexibility of the projection system, one projection apparatus may be generally adapted to multiple types of display screens, but the characteristics of the different types of display screens are different, for example, the different types of display screens have different reflectivities to each primary color, different gains, and different ambient light resistance.

In the prior art, when the projection apparatus is adapted to different types of display screens, image quality parameter adjustment is usually performed manually, since image quality parameter adjustment needs to be performed with a certain amount of professional knowledge, most users do not perform image quality parameter adjustment, and even a technician with professional knowledge needs a long time to complete image quality parameter adjustment, which results in low image quality parameter adjustment efficiency.

Disclosure of Invention

The embodiment of the invention provides an image display method, device and system. The image quality parameter adjusting efficiency is improved.

In a first aspect, an embodiment of the present invention provides an image display method applied to a projection system, where the projection system includes a projection device, a display screen, and a first optical sensor, the projection device is configured to project a preset image onto the display screen, and the method includes:

acquiring an optical signal received by the first optical sensor, wherein the optical signal is a signal reflected to the first optical sensor when the display screen displays the preset image, and the first optical sensor is located outside the display screen and in a viewing area corresponding to the display screen;

acquiring maximum reflection brightness, minimum reflection brightness and a white field color coordinate of the display screen under the maximum reflection brightness according to the optical signal received by the first optical sensor, wherein the maximum reflection brightness is the sum of the maximum display brightness of the display screen and the brightness of the ambient light reflected by the display screen, and the minimum reflection brightness is the sum of the minimum display brightness of the display screen and the brightness of the ambient light reflected by the display screen;

and adjusting image quality parameters of the projection equipment according to the maximum reflection brightness, the minimum reflection brightness and the white field color coordinate of the display screen, wherein the image quality parameters comprise at least one of a white balance coefficient, the purity of a preset color point and the brightness corresponding to each gray scale.

In a possible embodiment, acquiring the optical signal received by the first optical sensor comprises

Controlling the projection equipment to respectively project light rays corresponding to a plurality of preset images to the display screen so that the display screen displays the preset images;

and acquiring an optical signal reflected by the display screen and received by the first optical sensor, wherein the optical signal reflected by the display screen comprises an optical signal reflected by a preset image displayed by the display screen and an ambient optical signal reflected by the display screen.

In another possible embodiment, adjusting the image quality parameter of the projection device according to the maximum reflection brightness, the minimum reflection brightness, and the white field color coordinate of the display screen includes:

acquiring the contrast of the display screen according to the maximum reflection brightness and the minimum reflection brightness;

judging whether the contrast is smaller than a preset contrast or not;

if so, acquiring the ambient light brightness reflected by the display screen according to the optical signal received by the first optical sensor, and adjusting the image quality parameters of the projection equipment according to the white field color coordinate of the display screen, the standard white field color coordinate and the ambient light brightness reflected by the display screen;

and if not, adjusting the image quality parameters of the projection equipment according to the maximum reflection brightness of the display screen, the white field color coordinate of the display screen and the standard white field color coordinate.

In another possible embodiment, adjusting the image quality parameter of the projection device according to the white field color coordinate of the display screen, the standard white field color coordinate, and the ambient light brightness reflected by the display screen includes:

adjusting a white balance coefficient arranged on the projection equipment until the difference value between the white field color coordinate of the display screen and the standard white field color coordinate is within a preset difference value range;

according to the white field color coordinate of the display screen, the purity of a preset color point of the projection equipment is adjusted;

and adjusting the brightness of the preset gray scales according to the brightness of the environment light reflected by the display screen.

In another possible embodiment, adjusting the image quality parameter of the projection device according to the maximum reflection brightness of the display screen, the white field color coordinate of the display screen, and the standard white field color coordinate includes:

when the maximum reflection brightness of the display screen is larger than a preset threshold value, adjusting a white balance coefficient arranged on the projection equipment until the white field color coordinate of the display screen is the same as the standard white field color coordinate;

when the maximum reflection brightness of the display screen is smaller than or equal to the preset threshold value, adjusting a white balance coefficient arranged on the projection equipment until the difference value between the white field color coordinate of the display screen and the standard white field color coordinate is within a preset difference value range; and adjusting the purity of the preset color point of the projection equipment according to the white field color coordinate of the display screen.

In another possible embodiment, the adjusting the purity of the preset color point of the projection device according to the white field color coordinate of the display screen includes:

acquiring the standard purity of each preset color corresponding to the white field color coordinates of the display screen;

and adjusting the purity of each preset color to the corresponding standard purity.

In another possible embodiment, adjusting the brightness of the plurality of preset grays according to the brightness of the ambient light reflected by the display screen includes:

determining standard brightness corresponding to each preset gray level according to the brightness of the environment light reflected by the display screen;

and adjusting the brightness of each preset gray scale to the corresponding standard brightness.

In another possible embodiment, acquiring the maximum reflection brightness of the display screen according to the optical signal received by the first optical sensor includes:

when projection equipment projects a white image to the display screen, acquiring a first optical signal acquired by the first optical sensor;

acquiring a first spectral curve of the first optical signal;

extracting a first luminance in the first spectral curve, the first luminance including a luminance of a reflected white image of the display screen, a luminance of ambient light reflected by the display screen, and a luminance of ambient light directly impinging on the first light sensor;

acquiring a second optical signal acquired by a second optical sensor, wherein the second optical sensor is positioned outside the display screen and outside a viewing area corresponding to the display screen, and the second optical signal is an optical signal directly irradiated to the second optical sensor;

acquiring a second spectral curve of the second optical signal;

extracting a second brightness in the second spectral curve, wherein the second brightness is the brightness of the ambient light directly irradiating the second light sensor;

determining a difference between the first brightness and the second brightness as the maximum reflected brightness.

In another possible embodiment, acquiring white field color coordinates of the display screen at the maximum reflection brightness according to the light signal received by the first light sensor includes:

determining a third optical signal from the first optical signal and the second optical signal, the third optical signal comprising an optical signal of a reflected white image of the display screen and an ambient light signal reflected by the display screen;

acquiring a third spectral curve of the third optical signal;

and extracting white field color coordinates of the display screen at the maximum reflection brightness in the third spectral curve.

In another possible embodiment, acquiring the minimum reflection brightness of the display screen according to the optical signal received by the first optical sensor includes:

when the projection equipment projects a black image to the display screen, acquiring a fourth optical signal acquired by the first optical sensor;

acquiring a fourth spectral curve of the fourth optical signal;

extracting a fourth luminance in the fourth spectral curve, the fourth luminance including a luminance of a reflected black image of the display screen, a luminance of ambient light reflected by the display screen, and a luminance of ambient light directly irradiated on the first light sensor;

acquiring a fifth optical signal acquired by a second optical sensor, wherein the second optical sensor is positioned outside the display screen and outside a viewing area corresponding to the display screen, and the fifth optical signal is an optical signal directly irradiated to the second optical sensor;

acquiring a fifth spectral curve of the fifth optical signal;

extracting a fifth luminance in the fifth spectral curve, the fifth luminance being a luminance of the ambient light directly illuminated at the second light sensor;

determining a difference between the fourth luminance and the fifth luminance as the maximum reflection luminance.

In a second aspect, an embodiment of the present invention provides an image display system, including a projection device, a display screen, and a first light sensor, where the first light sensor is located outside the display screen and in a viewing area corresponding to the display screen, where,

the projection equipment is used for projecting a preset image to the display screen so that the display screen displays the preset image;

the first optical sensor is used for collecting optical signals reflected by the display screen to the preset image;

the projection equipment is further configured to obtain an optical signal received by the first optical sensor, and obtain a maximum reflection brightness, a minimum reflection brightness, and a white field color coordinate of the display screen according to the optical signal, where the maximum reflection brightness is a sum of a maximum display brightness of the display screen and a brightness of ambient light reflected by the display screen, and the minimum reflection brightness is a sum of a minimum display brightness of the display screen and a brightness of ambient light reflected by the display screen;

the projection equipment is further configured to adjust image quality parameters of the projection equipment according to the maximum reflection brightness, the minimum reflection brightness and white field color coordinates of the display screen, where the image quality parameters include at least one of a white balance coefficient, a purity of a preset color point, and a brightness corresponding to each gray scale.

In a third aspect, an embodiment of the present invention provides an image display apparatus applied to a projection system, where the projection system includes a projection device, a display screen, and a first light sensor, the projection device is configured to project a preset image onto the display screen, and the apparatus includes: a first obtaining module, a second obtaining module and an adjusting module, wherein,

the first obtaining module is configured to obtain an optical signal received by the first optical sensor, where the optical signal is a signal reflected to the first optical sensor when the display screen displays the preset image, and the first optical sensor is located outside the display screen and in a viewing area corresponding to the display screen;

the second obtaining module is configured to obtain, according to the optical signal received by the first optical sensor, a maximum reflection brightness, a minimum reflection brightness, and a white field color coordinate of the display screen under the maximum reflection brightness, where the maximum reflection brightness is a sum of a maximum display brightness of the display screen and a brightness of ambient light reflected by the display screen, and the minimum reflection brightness is a sum of a minimum display brightness of the display screen and a brightness of ambient light reflected by the display screen;

the adjusting module is configured to adjust image quality parameters of the projection device according to the maximum reflection brightness, the minimum reflection brightness, and white field color coordinates of the display screen, where the image quality parameters include at least one of a white balance coefficient, a purity of a preset color point, and a brightness corresponding to each gray scale.

In a possible implementation manner, the first obtaining module is specifically configured to:

In another possible embodiment, the adjusting module comprises an obtaining unit, a judging unit, a first adjusting unit and a second adjusting unit, wherein,

the obtaining unit is used for obtaining the contrast of the display screen according to the maximum reflection brightness and the minimum reflection brightness;

the judging unit is used for judging whether the contrast is smaller than a preset contrast or not;

the first adjusting unit is used for acquiring the ambient light brightness reflected by the display screen according to the optical signal received by the first optical sensor when the judging unit judges that the contrast is smaller than the preset contrast, and adjusting the image quality parameters of the projection equipment according to the white field color coordinate of the display screen, the standard white field color coordinate and the ambient light brightness reflected by the display screen;

and the second adjusting unit is used for adjusting the image quality parameters of the projection equipment according to the maximum reflection brightness of the display screen, the white field color coordinates and the standard white field color coordinates of the display screen when the judging unit judges that the contrast is greater than or equal to the preset contrast.

In another possible embodiment, the first adjusting unit is specifically configured to:

In another possible embodiment, the second adjusting unit is specifically configured to:

In another possible embodiment, the adjusting module is specifically configured to:

In another possible implementation manner, the second obtaining module is specifically configured to:

acquiring a first spectral curve of the first optical signal;

acquiring a second spectral curve of the second optical signal;

acquiring a third spectral curve of the third optical signal;

acquiring a fourth spectral curve of the fourth optical signal;

acquiring a fifth spectral curve of the fifth optical signal;

According to the image quality parameter adjusting method, device and system provided by the embodiment of the invention, when the image quality parameters in the projection equipment need to be adjusted, the projection equipment can project the preset image on the display screen, the display screen can reflect light projected on the display screen and ambient light projected on the display screen to the first optical sensor, and the first optical sensor is located outside the display screen and in the viewing area corresponding to the display screen. The projection equipment can adjust the image quality parameters of the projection equipment according to the light acquired by the first optical sensor, and the first optical sensor is positioned outside the display screen and in a viewing area corresponding to the display screen, namely, the position of the first optical sensor is similar to that of a user viewing the display screen, so that the light received by the first optical sensor is similar to that viewed by the user in the display screen, and the projection equipment can automatically adjust the image quality parameters of the projection equipment according to the actual condition of the display screen viewed by human eyes, thereby not only improving the accuracy of image quality parameter adjustment, but also improving the efficiency of image quality parameter adjustment.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a diagram of a projection system according to an embodiment of the present invention;

fig. 2 is a first schematic flow chart illustrating a method for adjusting image quality parameters according to an embodiment of the present invention;

FIG. 3 is a cross-sectional view of a Fresnel lens layer of a display panel with increased ambient light resistance according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a color curve provided by an embodiment of the present invention;

fig. 5 is a second flowchart illustrating a method for adjusting image quality parameters according to an embodiment of the present invention;

fig. 6 is a first schematic structural diagram of an image quality parameter adjusting apparatus according to an embodiment of the present invention;

fig. 7 is a schematic structural diagram of an image quality parameter adjusting apparatus according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Fig. 1 is an architecture diagram of an image display system according to an embodiment of the present invention. Referring to fig. 1, the display device includes a display screen 101, a projection device 102, and a first light sensor 103. The light emitted from the projection device 102 is projected on the display screen 101, and a picture is presented in the display screen 101. The first optical sensor 103 is located outside the display 101 and in a viewing area corresponding to the display 101, for example, the first optical sensor 103 may be disposed on the projection device 102, or may be disposed in another position, as long as the first optical sensor 103 can receive an optical signal reflected by the display 101, so that the optical signal reflected by the display received by the first optical sensor 103 is similar to an optical signal reflected by the display 101 to human eyes. Alternatively, the projection system shown in this application may be a laser projection system, and of course, the projection system may also be other types of projection systems, which is not specifically limited in this application.

In the practical application process, the final display effect of the display screen is determined by the projection device 102 and the display screen 101 together, and therefore, after the display screen 101 is replaced in the projection system, since the characteristics of different display screens are different, in order to ensure the display effect of the display screen, image quality parameters in the projection device 102 need to be adjusted.

In this application, when the image quality parameter in the projection equipment needs to be adjusted, projection equipment can project the preset image in the display screen to make the display screen display and preset the image, when the display screen is showing the preset image, the light that the display screen reflects can reflect to first light sensor, so that first light sensor can gather and obtain the display screen to the light signal of presetting the image reflection. The projection equipment can acquire the maximum reflection brightness, the minimum reflection brightness and the white field color coordinate of the display screen according to the optical signals acquired by the first optical sensor, and adjust the image quality parameters of the projection equipment according to the maximum reflection brightness, the minimum reflection brightness and the white field color coordinate of the display screen.

The technical means shown in the present application will be described in detail below with reference to specific examples. It should be noted that the following specific embodiments may be combined with each other, and description of the same or similar contents is not repeated in different embodiments.

Fig. 2 is a first flowchart of an image display method according to an embodiment of the present invention. Referring to fig. 2, the method may include:

s201, acquiring an optical signal received by a first optical sensor, wherein the optical signal is a signal reflected to the first optical sensor when a display screen displays a preset image, and the sensor is located outside the display screen and in a viewing area corresponding to the display screen.

The execution subject of the embodiment of the invention can be projection equipment and also can be an image quality parameter adjusting device. Alternatively, the image quality parameter adjusting device may be disposed in the projection apparatus. Alternatively, the image quality parameter adjusting device may be implemented by software, or may be implemented by a combination of software and hardware.

In an actual application process, when a user needs to adjust image quality parameters of the projection device, the user may input an adjustment instruction in the projection device, for example, the user may click a preset shortcut key in a control device (e.g., a remote controller) to input the adjustment instruction in the projection device, and of course, the user may also select a preset user menu option in the projection device to input the adjustment instruction in the projection device. Of course, in an actual application process, an adjustment instruction may also be input in the projection device according to other feasible implementation manners, which is not specifically limited in the embodiment of the present invention.

Of course, the method shown in the embodiment of fig. 2 may also be automatically executed when the projection system is first started to adjust the image quality parameters of the projection apparatus. The triggering condition for executing the method shown in the embodiment of fig. 2 is not specifically limited in the embodiment of the present invention.

When the image quality parameters of the projection equipment need to be adjusted, the projection equipment respectively projects a plurality of preset images to the display screen, so that the display screen displays the preset images.

Alternatively, the preset image may be a grayscale image, for example, the preset image includes a white image and a black image.

Optionally, the projection device may project, to the display screen, light corresponding to different preset images according to a preset time interval, for example, the projection device may project, to the display screen, the first preset image first, and project, to the display screen, the second preset image after the preset time interval until all light corresponding to the preset images is projected to the display screen. For example, the preset time interval may be 1 second, 2 seconds, and the like, and in an actual application process, the preset time interval may be set according to actual needs.

After every preset image is projected to the display screen by the projection equipment, the display screen reflects the preset image, and the first optical sensor is positioned outside the display screen and in a viewing area corresponding to the display screen, namely, the position of the first optical sensor is similar to the position of a user when the user views the display screen, so that the optical signal received by the first optical sensor is similar to the optical signal received by human eyes of the user.

S202, acquiring the maximum reflection brightness and the minimum reflection brightness of the display screen and the white field color coordinate of the display screen under the maximum reflection brightness according to the optical signal received by the first optical sensor.

The maximum reflection brightness is the sum of the maximum display brightness of the display screen and the brightness of the ambient light reflected by the display screen, and the minimum reflection brightness is the sum of the minimum display brightness of the display screen and the brightness of the ambient light reflected by the display screen.

Optionally, the different types of display screens have different ambient light resistance, and the ambient light resistance of the display screen is described below with reference to fig. 3.

Fig. 3 is a cross-sectional view of a fresnel lens layer of a display panel with high ambient light resistance according to an embodiment of the present invention.

Referring to fig. 3, the cross-sectional view of the fresnel lens layer of the display screen is provided with a coating layer on each of the saw-tooth-shaped upper surfaces a, the coating layer having a light absorbing function, i.e., light irradiated on the coating layer is not reflected. The lower surface B of each sawtooth is a reflecting surface for reflecting the received light. In the practical application process, the environment light usually irradiates on the upper surface A of the sawtooth, so that the upper surface A absorbs the environment light, the environment light cannot be reflected to human eyes, the light emitted by the projection equipment usually irradiates on the lower surface B of the sawtooth, so that the lower surface B reflects the environment light, and the human eyes can see the picture projected by the projection equipment in the display screen. From the above, the display screen shown in fig. 3 has strong ambient light resistance.

The fabric of the display screen resistant to weak ambient light is generally white plastic screen fabric, and the white plastic screen fabric performs diffuse reflection on all received light, that is, the display screen can reflect light emitted by the projection device and received ambient light to human eyes.

Alternatively, the maximum display brightness of the display screen is the maximum brightness when the image is displayed, for example, the maximum display brightness of the display screen may be the brightness when the display screen displays a white image. The minimum display luminance of the display screen is the minimum luminance of the display screen when displaying an image, and for example, the minimum display luminance of the display screen may be the luminance of the display screen when displaying a black image.

In the chromaticity diagram, one color coordinate (x, y) represents one color. The white field color coordinates refer to color coordinates corresponding to white. In the embodiment of the invention, when the image quality parameter in the projection device and the characteristic of the display screen do not match with each other, the first light sensor determines that the color represented by the white field color coordinate obtained according to the received light signal is not pure white, that is, when the image quality parameter in the projection device and the characteristic of the display screen do not match with each other, the white displayed by the display screen is not pure white. For example, when the white balance coefficient of the projection device and the reflectivity of the display screen for each primary color do not match, the white displayed by the display screen may be red, green, or blue.

Alternatively, the maximum reflection brightness of the display screen may be obtained by the following feasible implementation manners:

mode 1, when the projection device projects a white image to the display screen, acquiring a first optical signal acquired by a first optical sensor, acquiring a first spectral curve of the first optical signal, extracting first brightness from the first spectral curve, and determining the first brightness as the maximum reflection brightness of the display screen.

In this manner, since the first luminance extracted from the first spectral curve includes the maximum display luminance of the display screen, the ambient light intensity reflected by the display screen, and the ambient light intensity directly irradiated to the first light sensor, the accuracy of the maximum reflection luminance determined according to the above manner 1 is not good, but the maximum reflection luminance of the display screen can be obtained quickly according to the above manner 1.

Mode 2, when the projection device projects the white image to the display screen, acquiring a first optical signal acquired by the first optical sensor, acquiring a first spectral curve of the first optical signal, and extracting first brightness in the first spectral curve, where the first brightness includes brightness of the white image reflected by the display screen, brightness of ambient light reflected by the display screen, and brightness of ambient light directly irradiated on the first optical sensor. And acquiring a second optical signal acquired by a second optical sensor, wherein the second optical sensor is positioned outside the display screen and outside a viewing area corresponding to the display screen, the second optical signal is an optical signal directly irradiated to the second optical sensor, acquiring a second spectral curve of the second optical signal, extracting second brightness in the second spectral curve, the second brightness is the brightness of ambient light directly irradiated to the second optical sensor, and determining the difference between the first brightness and the second brightness as the maximum reflection brightness.

In this way, the accuracy of obtaining the maximum reflection brightness of the obtained display screen is high.

Optionally, the white field color coordinates of the display screen at the maximum reflection brightness can be obtained through at least two possible implementations as follows:

mode 1, when the projection device projects a white image to the display screen, acquiring a first optical signal acquired by a first optical sensor, acquiring a first spectral curve of the first optical signal, extracting a white field color coordinate from the first spectral curve, and determining the extracted white field color coordinate as the white field color coordinate of the display screen under the maximum reflection brightness.

In this manner, the accuracy of determining the obtained maximum reflection luminance is not good, but according to the above manner 1, the white field color coordinates of the display screen at the maximum reflection luminance can be obtained quickly.

Mode 2, when the projection device projects the white image to the display screen, acquiring a first optical signal acquired by a first optical sensor, acquiring a second optical signal acquired by a second optical sensor, where the second optical sensor is located outside the display screen and outside a viewing area corresponding to the display screen, the second optical signal is an optical signal directly irradiated to the second optical sensor, determining a third optical signal according to the first optical signal and the second optical signal, where the third optical signal includes an optical signal of the white image reflected by the display screen and an ambient optical signal reflected by the display screen, acquiring a third spectral curve of the third optical signal, and extracting a white field color coordinate of the display screen at maximum reflection brightness in the third spectral curve.

For example, the first optical signal and the second optical signal may be subjected to a difference processing to obtain a third optical signal.

In this way, the accuracy of the acquired white field color coordinates of the display screen at the maximum reflection brightness is high.

Alternatively, the minimum reflection brightness of the display screen may be obtained by the following feasible implementation manners:

mode 1, when the projection device projects the black image to the display screen, acquiring a fourth optical signal acquired by the first optical sensor, acquiring a fourth spectral curve of the fourth optical signal, extracting fourth brightness from the fourth spectral curve, and determining the fourth brightness as the minimum reflection brightness of the display screen.

In this manner, since the fourth luminance extracted from the fourth spectral curve includes the maximum display luminance of the display screen, the ambient light intensity reflected by the display screen, and the ambient light intensity directly irradiated to the first light sensor, the accuracy of the minimum reflection luminance determined according to the above manner 1 is not good, but according to the above manner 1, the minimum reflection luminance of the display screen can be obtained quickly.

Mode 2, when the projection device projects the black image to the display screen, acquiring a fourth optical signal acquired by the first optical sensor, acquiring a fourth spectral curve of the fourth optical signal, and extracting fourth luminance from the fourth spectral curve, where the fourth luminance includes luminance of the black image reflected by the display screen, luminance of ambient light reflected by the display screen, and luminance of ambient light directly irradiated to the first optical sensor. And acquiring a fifth optical signal acquired by the second optical sensor, wherein the second optical sensor is positioned outside the display screen and outside a viewing area corresponding to the display screen, the fifth optical signal is an optical signal directly irradiated to the second optical sensor, acquiring a fifth spectral curve of the fifth optical signal, extracting fifth brightness in the fifth spectral curve, the fifth brightness is the brightness of ambient light directly irradiated to the second optical sensor, and determining the difference between the fourth brightness and the fifth brightness as the maximum reflection brightness.

In this way, the accuracy of obtaining the minimum reflection luminance of the obtained display screen is high.

S203, adjusting image quality parameters of the projection equipment according to the maximum reflection brightness, the minimum reflection brightness and the white field color coordinate of the display screen under the maximum reflection brightness.

The image quality parameter includes at least one of a white balance coefficient, a purity of a preset color point, and a brightness corresponding to each gray scale.

Of course, in the practical application process, the image quality parameters may also include other parameters, such as brightness, contrast, and sharpness, and the content included in the image quality parameters is not specifically limited in the embodiment of the present invention.

Alternatively, the white balance coefficient refers to a scale coefficient when white is synthesized by three primary colors. For example, if white is W and the three primary colors are R, G, B, W is a × R + B × G + c × B, and a, B, and c are the scaling factors for synthesizing white. When the display screen has different reflectivity for each primary color, the white balance coefficient of the display screen is also different.

A white balance coefficient is set in the projection apparatus, and the projection apparatus emits white light in accordance with the white balance coefficient. When the white balance coefficient set in the projection device is consistent with the white balance coefficient of the adapted display screen, it can be ensured that the white color presented in the display screen is relatively pure, otherwise, the white color presented in the display screen is not pure, for example, the white color presented in the display screen may be red, green, etc. Meanwhile, the adjustment of other colors by the projection device depends on the white balance coefficient, so that the white balance coefficient arranged in the projection device needs to be adjusted in order to enable the display screen to display the correct color according to the light emitted by the projection device.

The purity of the predetermined color point shown in the present application will be described in detail with reference to fig. 4. Fig. 4 is a schematic diagram of a color curve according to an embodiment of the present invention.

Referring to fig. 4, in the direction from left to right of the abscissa, the gradual changes from purple to red, to green, and to blue are sequentially performed, the abscissa includes 28 points, each point represents a preset color, optionally, the preset color may be a standard skin color, a standard rape yellow, a standard blue sky blue, and the like, for example, the color corresponding to the 14 th point in fig. 4 is a standard skin color.

Referring to fig. 4, the ordinate represents the purity of the color, and the larger the value corresponding to the ordinate, the higher the purity of the color, and the denser the corresponding color. For example, for the 6 th point in fig. 4, when the value of the 6 th point on the ordinate is 20, the color corresponding to the 6 th point is large red, and the red corresponding to the 6 th point becomes lighter in order as the value on the ordinate decreases.

When the white field coordinates of the display screen are different, the purities corresponding to the preset colors are different, that is, the purities of the preset colors need to be adjusted according to the white field coordinates, so as to adjust the purities of the preset color points. For example, when the white field coordinates of the display screen are (x1, y1), then the purity of the 14 th point (standard skin color) should be-16, i.e., only when the color concentration of the abscissa on which the 14 th point is located is-16, the display screen can be made to display the standard skin color. When the white field coordinates of the display screen are (x2, y2), then the purity of the 14 th point (standard skin color) should be-16.5, i.e., only when the color concentration of the abscissa where the 14 th point is located is-16.5, the display screen can be made to display the standard skin color.

When the display screen has poor light resistance to the environment, the gray scale level of the displayed picture is deteriorated, that is, the difference value of the brightness observed by the user and corresponding to different gray scales is reduced, so that the picture looks whitish. At this time, the brightness values of different gray scales can be adjusted to make the difference between the brightness values of different gray scales larger, thereby avoiding gray scale gradation deterioration, for example, the gamma curve of the image can be adjusted to adjust the brightness values of different gray scales. It should be noted that, in the embodiment shown in fig. 5, a detailed description of adjusting the brightness of the projection apparatus is described, and details are not described here again.

By adjusting the purity of the preset color points, the hue or tone of the image observed by human eyes can be adjusted.

According to the image quality parameter adjusting method provided by the embodiment of the invention, when the image quality parameter set in the projection equipment needs to be adjusted, the projection equipment can project the preset image into the display screen, and the display screen can reflect the image projected on the display screen and the ambient light projected on the display screen to the first light sensor. The projection equipment can adjust the image quality parameters of the projection equipment according to the light acquired by the first optical sensor, and the first optical sensor is positioned outside the display screen and in a viewing area corresponding to the display screen, namely, the position of the first optical sensor is similar to that of a user viewing the display screen, so that the light received by the first optical sensor is similar to that viewed by the user in the display screen, and the projection equipment can automatically adjust the image quality parameters of the projection equipment according to the actual condition of the display screen viewed by human eyes, thereby not only improving the accuracy of image quality parameter adjustment, but also improving the efficiency of image quality parameter adjustment.

On the basis of any of the above embodiments, optionally, the image quality parameter of the projection device may be adjusted through the following feasible implementation manner, specifically, please refer to the embodiment shown in fig. 5.

Fig. 5 is a flowchart illustrating a second method for adjusting image quality parameters according to an embodiment of the present invention. Referring to fig. 5, the method may include:

s501, obtaining the contrast of the display screen according to the maximum reflection brightness and the minimum reflection brightness.

Alternatively, the ratio of the maximum reflected brightness to the minimum reflected brightness may be determined as the contrast of the display screen.

Optionally, assuming that the maximum display brightness of the display screen is Lmax, the minimum display brightness of the display screen is Lmin, and assuming that the reflection brightness of the display screen to the ambient light is La, the maximum reflection brightness of the display screen is Lmax + La, and the minimum reflection brightness of the display screen is Lmin + La, and accordingly, the contrast of the display screen is:

for example, assume that the maximum display luminance Lmax of the display screen is 300 and the minimum display luminance Lmin of the display screen is 0.2. When the reflection brightness of the display screen to the ambient light is 0, the contrast of the display screen is:

when the reflection brightness La of the display screen to the ambient light is 0.5, the contrast of the display screen is:

from the above, as the reflection brightness of the display screen to the ambient light is larger, the contrast of the display screen is smaller. The stronger the ambient light resistance of the display screen, the smaller the reflection brightness of the display screen to ambient light, so that the ambient light resistance of the display screen can be reflected through the contrast of the display screen.

S502, judging whether the contrast is smaller than a preset contrast.

If so, S503-S506 are performed.

If not, S507-S509 is executed.

Optionally, when the contrast is smaller than the preset contrast, it indicates that the ambient light resistance of the display screen is poor, and when the contrast is greater than or equal to the preset contrast, it indicates that the ambient light resistance of the display screen is strong. For example, the preset contrast may be any number between 400 and 600, and of course, in the actual application process, the preset contrast may be set according to actual needs, which is not specifically limited in the embodiment of the present invention.

In the practical application process, the requirement on the brightness is higher for the display screen with poor ambient light resistance, so that when the ambient light resistance of the display screen adaptive to the projection equipment is poor, the brightness of the display screen needs to be reduced as little as possible. The brightness of the display screen is usually reduced in the process of adjusting the color coordinates of the display screen, so that the color coordinates of the display screen need to be adjusted as little as possible for the display screen with poor ambient light resistance.

The requirement on brightness is lower for the display screen with stronger ambient light resistance, so that when the display screen adaptive to the projection equipment has stronger ambient light resistance, the brightness of the display screen can be properly sacrificed to ensure the optimal color expression, that is, the color coordinate of the display screen can be fully adjusted to ensure the optimal color expression of the display screen.

S503, adjusting the white balance coefficient of the projection equipment until the difference value between the white field color coordinate of the display screen and the standard white field color coordinate is within a preset difference value range.

Alternatively, the standard white field color coordinates (x0, y0) are preset in the projection device assuming that the white balance coefficients are (a, b, c), and the white field color coordinates of the display screen are (x, y). When x is greater than x0, the value of a is decreased, when y is greater than y0, the value of b is decreased, and when x is less than x0, or y is less than y0, the value of c is decreased.

Optionally, when the value of a, b, or c is decreased, the value of a, b, or c is decreased by a preset value according to a preset step length.

It should be noted that, after the white balance coefficient is adjusted once, the white balance coefficient of the projection apparatus changes, and therefore, the acquired white field coordinates of the display screen also change. And continuously comparing the changed white field color coordinates with the standard white field color coordinates, adjusting the white balance coefficient according to the comparison result, and so on until the difference value between the white field color coordinates of the display screen and the standard white field color coordinates is within a preset difference value range.

For example, if the horizontal axis corresponds to the preset difference value S1 and the vertical axis corresponds to the preset difference value S2, then | x-x0| < S1, | y-y0| < S2.

In S503, because the display screen has poor ambient light resistance and has a high requirement on brightness, in order to avoid that the brightness of the display screen becomes low due to over-adjustment of the white field color coordinate of the display screen, the white field color coordinate of the display screen is not adjusted too much, but the white field color coordinate of the display screen is adjusted to be within a range of the standard color coordinate, at this time, a certain difference exists between the white field color coordinate of the display screen and the standard color coordinate, so that the white display of the display screen is not pure enough, and correspondingly, the color display of the display screen is not pure enough, and in order to enable the display screen to display better colors as much as possible, S504 needs to be further performed to adjust the purity of the preset color points of the display screen.

S504, according to the white field color coordinates of the display screen, the purity of the preset color points of the projection equipment is adjusted.

The white field color coordinates indicated in S504 refer to the white field color coordinates of the display screen obtained after the adjustment in S503.

The preset color standard purities corresponding to different white field color coordinates are different, and the corresponding relationship between the different white field color coordinates and the preset color standard purities can be preset, so that the purities of the preset color points of the projection equipment can be adjusted according to the corresponding relationship.

For example, the correspondence between the white field color coordinates and the standard purity of the preset color may be as shown in table 2:

TABLE 2

Optionally, when the purity of the preset color point of the projection device is adjusted, the corresponding standard purity of the preset color may be queried in the corresponding relationship shown in table 2 according to the white field color coordinate of the display screen, and the purity of the preset color is adjusted to the standard purity.

And S505, acquiring the brightness of the environment light reflected by the display screen according to the optical signal received by the first optical sensor.

For a display screen which may be poor in ambient light resistance, when ambient light irradiates the display screen, a user sees that a picture displayed by the display screen is entirely floating white, so that gray scale levels displayed by the display screen are not obvious, that is, the contrast of the display screen is reduced.

Optionally, the reflected brightness of the display screen is obtained according to the optical signal received by the sensor, and the difference between the emitted brightness and the display brightness of the display screen is the ambient light brightness.

And S506, adjusting the brightness of the preset gray scales according to the ambient light brightness reflected by the display screen.

Alternatively, the preset gray level may be black field, 10% gray, 20% gray, 30% gray, 40% gray, 50% gray, 60% gray, 70% gray, 80% gray, 90% gray, 100% white.

Alternatively, the brightness of a plurality of preset grays can be adjusted through the following feasible implementation modes: determining standard brightness corresponding to each preset gray level according to the brightness of the environment light reflected by the display screen; and adjusting the brightness of each gray scale to the corresponding standard brightness.

Optionally, the standard brightness corresponding to each preset gray level may be determined according to the ambient light brightness reflected by the display screen and a preset corresponding relationship, where the preset corresponding relationship includes a plurality of preset ambient light brightness and the standard brightness of each preset gray level corresponding to each preset ambient light brightness.

Optionally, the preset corresponding relationship may be as shown in table 3:

TABLE 3

Optionally, when the brightness of the multiple preset grayscales is adjusted, the standard brightness of each preset grayscale can be searched in the corresponding relationship shown in table 3 according to the ambient light brightness reflected by the display screen, and the brightness of each preset grayscale is set as the standard brightness.

Optionally, the brightness of the preset gray scale may be adjusted by adjusting the emission power of the projection device.

It should be noted that when the contrast is determined to be smaller than the preset contrast, only S503 may be executed, or S503 to S504 may be executed, or S503, S505 to S506 may be executed, or S503 to S506 may be executed. That is, when the contrast is determined to be smaller than the preset contrast, only the white balance coefficient of the projection device may be adjusted, the white balance coefficient of the projection device and the purity of the preset color point may also be adjusted, the white balance coefficient of the projection device and the brightness corresponding to each gray scale may also be adjusted, and the white balance coefficient of the projection device, the purity of the preset color point, and the brightness corresponding to each gray scale may also be adjusted.

When S503-S506 are executed, S504 and S505-S506 may be executed simultaneously or sequentially, and the execution order of S504 and S505-S506 is not particularly limited in the embodiment of the present invention.

And S507, judging whether the maximum reflection brightness of the display screen is greater than a preset threshold value.

If yes, go to step S508.

If not, go to S509.

And S508, adjusting the white balance coefficient of the projection equipment until the white field color coordinate of the display screen is the same as the standard white field color coordinate.

In S508, it is determined that the display screen has a strong ambient light resistance, that is, the display screen has a low requirement for brightness, and further, when it is determined that the obtained maximum reflection brightness of the display screen is greater than a preset threshold, it indicates that the current brightness of the display screen is high, so that the brightness of some display screens can be sacrificed to ensure the optimal color display effect of the display screen, that is, the white balance coefficient of the projection apparatus can be directly adjusted until the white field color coordinate of the display screen is the same as the standard white field color coordinate, and at this time, because the white field color coordinate of the display screen is the same as the standard white field color coordinate, the color display effect of the display screen can be optimal.

And S509, adjusting a white balance coefficient of the projection equipment until the difference value between the white field color coordinate of the display screen and the standard white field color coordinate is within a preset difference value range.

It should be noted that the execution process of S509 may refer to S503, and is not described herein again.

And S510, adjusting the purity of the preset color point of the projection equipment according to the white field color coordinate of the display screen.

It should be noted that the execution process of S510 may refer to S504, and is not described herein again.

It should be noted that when it is determined that the contrast is greater than or equal to the preset contrast and the maximum reflection brightness of the display screen is less than or equal to the preset threshold, only S509 may be performed, or S509-S510 may be performed, or S509, S505-S506 may be performed, or S509-S510, S505-S506 may also be performed. That is, when it is determined that the contrast is greater than or equal to the preset contrast and the maximum reflection brightness of the display screen is less than or equal to the preset threshold, only the white balance coefficient of the projection device may be adjusted, the white balance coefficient of the projection device and the purity of the preset color point may also be adjusted, the white balance coefficient of the projection device and the brightness corresponding to each gray scale may also be adjusted, and the white balance coefficient of the projection device, the purity of the preset color point, and the brightness corresponding to each gray scale may also be adjusted.

Fig. 6 is a first schematic structural diagram of an image display device according to an embodiment of the present invention. The image display device is applied to a projection system, the projection system comprises a projection device, a display screen and a first optical sensor, the projection device is used for projecting a preset image to the display screen, and the device comprises: a first acquisition module 11, a second acquisition module 12 and an adjustment module 13, wherein,

the first obtaining module 11 is configured to obtain an optical signal received by the first optical sensor, where the optical signal is a signal reflected to the first optical sensor when the display screen displays the preset image, and the first optical sensor is located outside the display screen and in a viewing area corresponding to the display screen;

the second obtaining module 12 is configured to obtain, according to the optical signal received by the first optical sensor, a maximum reflection brightness, a minimum reflection brightness, and a white field color coordinate of the display screen under the maximum reflection brightness, where the maximum reflection brightness is a sum of a maximum display brightness of the display screen and a brightness of ambient light reflected by the display screen, and the minimum reflection brightness is a sum of a minimum display brightness of the display screen and a brightness of ambient light reflected by the display screen;

the adjusting module 13 is configured to adjust image quality parameters of the projection device according to the maximum reflection brightness, the minimum reflection brightness, and white field color coordinates of the display screen, where the image quality parameters include at least one of a white balance coefficient, a purity of a preset color point, and a brightness corresponding to each gray scale.

It should be noted that the image display device according to the embodiment of the present invention may implement the technical solutions shown in the above method embodiments, and the implementation principle and the beneficial effects thereof are similar, and are not described herein again.

In a possible implementation manner, the first obtaining module 11 is specifically configured to:

Fig. 7 is a schematic structural diagram of an image display device according to an embodiment of the present invention. On the basis of the embodiment shown in fig. 6, please refer to fig. 7, the adjusting module 13 includes an obtaining unit 131, a determining unit 132, a first adjusting unit 133 and a second adjusting unit 134, wherein,

the obtaining unit 131 is configured to obtain a contrast of the display screen according to the maximum reflection brightness and the minimum reflection brightness;

the determining unit 132 is configured to determine whether the contrast is smaller than a preset contrast;

the first adjusting unit 133 is configured to, when the determining unit determines that the contrast is smaller than a preset contrast, obtain the ambient light brightness reflected by the display screen according to the optical signal received by the first optical sensor, and adjust the image quality parameter of the projection apparatus according to the white field color coordinate of the display screen, the standard white field color coordinate, and the ambient light brightness reflected by the display screen;

the second adjusting unit 134 is configured to adjust the image quality parameter of the projection apparatus according to the maximum reflection brightness of the display screen, the white field color coordinate of the display screen, and the standard white field color coordinate when the determining unit determines that the contrast is greater than or equal to the preset contrast.

In another possible implementation, the first adjusting unit 133 is specifically configured to:

In another possible implementation, the second adjusting unit 134 is specifically configured to:

In another possible embodiment, the adjusting module 13 is specifically configured to:

In another possible implementation, the second obtaining module 12 is specifically configured to:

acquiring a first spectral curve of the first optical signal;

acquiring a second spectral curve of the second optical signal;

acquiring a third spectral curve of the third optical signal;

acquiring a fourth spectral curve of the fourth optical signal;

acquiring a fifth spectral curve of the fifth optical signal;

It should be noted that the image quality parameter adjusting apparatus according to the embodiment of the present invention may implement the technical solutions shown in the above method embodiments, and the implementation principles and the beneficial effects thereof are similar and will not be described herein again.

Those of ordinary skill in the art will understand that: all or a portion of the steps of implementing the above-described method embodiments may be performed by hardware associated with program instructions. The program may be stored in a computer-readable storage medium. When executed, the program performs steps comprising the method embodiments described above; and the aforementioned storage medium includes: various media that can store program codes, such as ROM, RAM, magnetic or optical disks.

Finally, it should be noted that: the above embodiments are only used for illustrating the technical solutions of the embodiments of the present invention, and are not limited thereto; although embodiments of the present invention have been described in detail with reference to the foregoing embodiments, those skilled in the art will understand that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the embodiments of the present invention.

Claims

1. An image display method is applied to a projection system, the projection system comprises a projection device, a display screen and a first light sensor, the projection device is used for projecting a preset image to the display screen, and the method comprises the following steps:

adjusting image quality parameters of the projection equipment according to the maximum reflection brightness, the minimum reflection brightness and white field color coordinates of the display screen, wherein the image quality parameters comprise at least one of a white balance coefficient, purity of a preset color point and brightness corresponding to each gray scale;

adjusting image quality parameters of the projection equipment according to the maximum reflection brightness, the minimum reflection brightness and the white field color coordinate of the display screen, wherein the image quality parameters comprise:

judging whether the contrast is smaller than a preset contrast or not;

if so, adjusting a white balance coefficient arranged on the projection equipment until the difference value between the white field color coordinate of the display screen and the standard white field color coordinate is within a preset difference value range;

if not, judging whether the maximum reflection brightness of the display screen is larger than a preset threshold value or not; when the maximum reflection brightness of the display screen is larger than a preset threshold value, adjusting a white balance coefficient arranged on the projection equipment until the white field color coordinate of the display screen is the same as the standard white field color coordinate; and when the maximum reflection brightness of the display screen is smaller than or equal to the preset threshold, adjusting a white balance coefficient arranged on the projection equipment until the difference value between the white field color coordinate of the display screen and the standard white field color coordinate is within a preset difference value range.

2. The method of claim 1, wherein acquiring the light signal received by the first light sensor comprises

3. The method of claim 1, wherein adjusting the image quality parameter of the projection device according to the white field color coordinates of the display screen, the standard white field color coordinates, and the ambient light level reflected by the display screen comprises:

and adjusting the brightness of a plurality of preset gray scales according to the brightness of the environment light reflected by the display screen.

4. The method of claim 3, wherein adjusting the purity of the preset color point of the projection device according to the white field color coordinates of the display screen comprises:

5. The method of claim 3, wherein adjusting the brightness of the plurality of preset gray levels according to the brightness of the ambient light reflected by the display screen comprises:

6. The method of claim 1 or 2, wherein obtaining the maximum reflected brightness of the display screen from the light signal received by the first light sensor comprises:

acquiring a first spectral curve of the first optical signal;

acquiring a second spectral curve of the second optical signal;

7. The method of claim 1 or 2, wherein obtaining white field color coordinates of the display screen at the maximum reflected brightness from the light signal received by the first light sensor comprises:

acquiring a third spectral curve of the third optical signal;

8. The method of claim 1 or 2, wherein obtaining the minimum reflected brightness of the display screen from the light signal received by the first light sensor comprises:

acquiring a fourth spectral curve of the fourth optical signal;

acquiring a fifth spectral curve of the fifth optical signal;

determining a difference between the fourth luminance and the fifth luminance as the minimum reflected luminance.

9. An image display system comprising a projection device, a display screen, and a first light sensor located outside the display screen and in a viewing area corresponding to the display screen, wherein,

the projection equipment is further used for adjusting image quality parameters of the projection equipment according to the maximum reflection brightness, the minimum reflection brightness and white field color coordinates of the display screen, wherein the image quality parameters comprise at least one of a white balance coefficient, purity of a preset color point and brightness corresponding to each gray scale;

the projection device is specifically configured to obtain the contrast of the display screen according to the maximum reflection brightness and the minimum reflection brightness; judging whether the contrast is smaller than a preset contrast or not; if so, adjusting a white balance coefficient arranged on the projection equipment until the difference value between the white field color coordinate of the display screen and the standard white field color coordinate is within a preset difference value range; if not, judging whether the maximum reflection brightness of the display screen is larger than a preset threshold value or not; when the maximum reflection brightness of the display screen is larger than a preset threshold value, adjusting a white balance coefficient arranged on the projection equipment until the white field color coordinate of the display screen is the same as the standard white field color coordinate; and when the maximum reflection brightness of the display screen is smaller than or equal to the preset threshold, adjusting a white balance coefficient arranged on the projection equipment until the difference value between the white field color coordinate of the display screen and the standard white field color coordinate is within a preset difference value range.

10. An image display apparatus, applied to a projection system, the projection system including a projection device, a display screen and a first light sensor, the projection device being configured to project a preset image onto the display screen, the apparatus comprising: a first obtaining module, a second obtaining module and an adjusting module, wherein,

the adjusting module is used for adjusting image quality parameters of the projection equipment according to the maximum reflection brightness, the minimum reflection brightness and white field color coordinates of the display screen, wherein the image quality parameters comprise at least one of a white balance coefficient, purity of a preset color point and brightness corresponding to each gray scale;

the adjusting module is specifically configured to obtain the contrast of the display screen according to the maximum reflection brightness and the minimum reflection brightness; judging whether the contrast is smaller than a preset contrast or not; if so, adjusting a white balance coefficient arranged on the projection equipment until the difference value between the white field color coordinate of the display screen and the standard white field color coordinate is within a preset difference value range; if not, judging whether the maximum reflection brightness of the display screen is larger than a preset threshold value or not; when the maximum reflection brightness of the display screen is larger than a preset threshold value, adjusting a white balance coefficient arranged on the projection equipment until the white field color coordinate of the display screen is the same as the standard white field color coordinate; and when the maximum reflection brightness of the display screen is smaller than or equal to the preset threshold, adjusting a white balance coefficient arranged on the projection equipment until the difference value between the white field color coordinate of the display screen and the standard white field color coordinate is within a preset difference value range.