Patent Description:
Along with the advancement of imaging technology, a large number of televisions are support for hybrid log-gamma high dynamic range imaging (HLG-HDR). Accordingly, more and more media content sources, such as DVD, Blu-ray, cable television, or cloud television, provide image signal with HLG-HDR class. Furthermore, more and more photographers use HLG-HDR-supported camera to take photos with high dynamic range. However, since currently the image processor (e.g., digital display processor (DDP)) of a lot of projectors do not support HLG-HDR class input signal, these projectors cannot project the image in a right way when the input image signal is in HLG-HDR class, and the projected image will be severely color shift. Otherwise, the user merely able to choose the projector supporting the HLG-HDR class image signals with the high price. As such, it is important to those skilled in the art to provide a method that can make an affordable projector able to display HLG-HDR images or non-HLG-HDR images in a proper way.

The information disclosed in this "BACKGROUND" section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Further, the information disclosed in the "BACKGROUND" section does not mean that one or more problems to be resolved by one or more embodiments of the disclosure were acknowledged by a person of ordinary skill in the art. <CIT> relates to a video signal processing method. The method comprises the following steps: after performing color space conversion and conversion from nonlinear space to linear space on a to-be-processed video signal, performing luminance mapping and color gamut conversion, carrying out conversion from the linear space to the nonlinear space and colorspace conversion on the signal subjected to color gamut conversion; then, performing saturated degree mapping on the converted signal; obtaining a video signal matched with the format supported by the display device so that the to-be-processed video signal can be correctly displayed on the display device.

The disclosure provides a projector and a method capable of projecting, according to an image signal, an image light beam with a proper color gamut no matter what class the image signal is.

Other objectives and advantages of the disclosure can be further understood from the technical features disclosed in the disclosure.

To make the aforementioned more comprehensible, several embodiments accompanied with drawings are described in detail as follows.

It is to be understood that other embodiment may be utilized and structural changes may be made without departing from the scope of the present disclosure. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. Unless limited otherwise, the terms "connected," "coupled," and "mounted," and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings.

<FIG> is a block diagram illustrating a projector <NUM> for projecting an image light beam IB according to an image signal IS according to an embodiment of the disclosure. The projector may include a processor <NUM>, a receiver <NUM>, a light source module <NUM>, a color conversion module <NUM>, a light valve <NUM>, and a projection lens <NUM>.

The processor <NUM> is coupled to the receiver <NUM>, the light source module <NUM>, the color conversion module <NUM>, and the light valve <NUM>. The processor <NUM> may be, for example, a DDP, a central processing unit (CPU) or other programmable microprocessor for general or special use, a digital signal processor (DSP), a programmable controller, an application specific integrated circuit (ASIC), a graphics processing unit (GPU), or any other similar device or a combination of the foregoing devices. Nevertheless, the disclosure is not limited thereto.

The processor <NUM> may be configured to perform gamma correction on a converted image CI received from the receiver <NUM> to generate a corrected image signal, and to transfer said corrected image signal into an optical signal OS.

The receiver <NUM> may be, for example, a High Definition Multimedia Interface (HDMI) receiver. Nevertheless, the disclosure is not limited thereto. The receiver <NUM> may be configured to receive the image signal IS and decode the image signal IS to obtain a metadata of the image signal IS. In some embodiments, the metadata may indicate that the image signal IS is corresponded to standard dynamic range (SDR) or high dynamic range (HDR) class. More specifically, the HDR class signal may refer to HRD <NUM>, Dolby vision HDR or HLG-HDR. For example, assuming that the image signal IS is in HDMI <NUM> format, then the metadata may be, for example, a Dynamic Range and Mastering InfoFrame as shown in Table <NUM>, wherein the Dynamic Range and Mastering InfoFrame may include data such as a static metadata and may indicate an Electro-Optical Transfer Function (EOTF), corresponding to the image signal IS. As following shown, the static metadata may is represented by <NUM> bits, and the EOTF may is represented by <NUM> bits.

In some embodiment, the receiver <NUM> decodes the image signal IS and obtains a static metadata, a content-dependent metadata and a EOTF, and the processor <NUM> generates an optical signal without basing the content-dependent metadata. In some embodiment, the image signal IS may be a HLG-HDR class signal, the metadata decoded from the image signal IS may merely include the static metadata. That is, the metadata of the image signal IS with HLG-HDR class does not contain a content-dependent metadata.

Furthermore, the metadata includes the EOTF as shown in Table <NUM>, wherein Table <NUM> explains Data Byte <NUM> of the Dynamic Range and Mastering InfoFrame which identifies the EOTF used in the image signal IS.

Furthermore, the receiver <NUM> may be configured to determine, according to the metadata, whether the image signal IS is a HLG-HDR signal, and to convert, in response to the image signal IS is the HLG-HDR signal, a color space of the image signal IS from a wider color gamut to a narrower color gamut so as to generate the converted image signal CI. In some embodiment, the receiver <NUM> may be configured to convert, according to the EOTF, a color space of the image signal IS from a wider color gamut to a narrower color gamut so as to generate the converted image signal CI. That is, the converted image signal CI related to the image signal SI can be supported by the processor <NUM>. For example, the receiver <NUM> may determine whether the color space of the image signal IS received by the receiver <NUM> corresponding to a wider color gamut (e.g., BT. <NUM>, <NUM>/<NUM> Standard) which is not supported by the processor <NUM>. If the image signal IS is the HLG-HDR signal corresponding to the wider color gamut which is not supported by the processor <NUM>, the receiver <NUM> may convert, according to the metadata, the color space of the image signal IS from the wider color gamut to a narrower color gamut (e.g., BT. <NUM>, Current Full HD Standard), which is supported by the processor <NUM>, so as to generate the converted image signal CI. To be more specific, the receiver <NUM> may converts the color space of the image signal IS from the wider color gamut to a narrower color gamut according to the EOTF which indicates that the image signal IS is the HLG-HDR signal. The detail operation of the processor <NUM> and the receiver <NUM> will be described below.

The light source module <NUM> is coupled to the processor <NUM> and providing a light beam LB. To be more specific, the processor <NUM> may be configured to turn on or turn off the light source module <NUM> so as to enable the light beam LB or disable the light beam LB. In one embodiment, the processor <NUM> may further control the brightness of the light source module <NUM> according to the optical signal OS. The light beam LB may be generated by at least a light lamp, a laser diode (LD), or a light-emitting diode (LED) disposed in the light source module <NUM>. Nevertheless, the disclosure is not limited thereto.

Referring to <FIG>, in the embodiment, the color conversion module <NUM> is coupled to the processor <NUM> and disposed on a transmission path of the light beam LB. The color conversion module <NUM> may be implemented by, for example, a phosphor wheel or a color wheel. The color conversion is configured to modulate, according to the optical signal, the light beam to an illumination beam LB'. Nevertheless, the disclosure is not limited thereto.

The light valve <NUM> is coupled to the processor <NUM> and disposed on the transmission path of an illumination beam LB', wherein the light valve <NUM> is configured to modulate, according to the optical signal OS received from the processor <NUM>, the illumination beam LB' to form the image light beam IB. The light valve <NUM> may be implemented by, for example, a digital micromirror device (DMD), liquid crystal on silicon (LCoS), liquid crystal display (LCD), or an Eidophor's oil-file based system, even maybe a Grating light valve. Nevertheless, the disclosure is not limited thereto.

The projection lens <NUM> is disposed on a transmission path of the image light beam IB formed by the light valve <NUM>. The projection lens <NUM> may project the image light beam IB.

<FIG> is a flow chart illustrating a method for projecting an image light beam IB according to an image signal IS according to an embodiment of the disclosure, wherein said method may be implemented by the projector <NUM> as illustrated in <FIG>.

In step S201, the receiver <NUM> receives an image signal IS and decodes the image signal IS to obtain a metadata of the image signal, wherein the metadata indicates the image signal IS is corresponded to SDR, HDR, or HLG-HDR class. To be more specific, the metadata includes the EOTF corresponding to the image signal IS which indicates the image signal is corresponded to SDR, HDR, or HLG-HDR class.

In step S202, the receiver <NUM> determines whether the image signal IS is a HLG-HDR signal according to the EOTF. If the image signal IS is the HLG-HDR signal, that is, the image signal IS is corresponded to HLG-HDR class, proceed to step S203. Otherwise, proceed to step S204.

In step S203, the receiver <NUM> converts a color space of the image signal IS according to the metadata from a wider color gamut to a narrower color gamut so as to generate a converted image signal CI. For example, said wider color gamut may correspond to a color space related to the HLG-HDR class which is not supported by the processor <NUM>, and said narrower color gamut may correspond to a color space related to the SDR class which is supported by the processor <NUM>. In other words, the receiver <NUM> could convert the image signal IS corresponding to the HLG-HDR class which is not supported by the processor <NUM> to the converted image signal CI corresponding to the SDR class which is supported by the processor <NUM>. In some embodiment, the receiver <NUM> converts a color space of the image signal IS from a wider color gamut to a narrower color gamut so as to generate a converted image signal CI, wherein the narrower color gamut may correspond to a color space related to and wider than the SDR class, and the narrower color gamut is still supported by the processor <NUM>.

Is step S204, the processor <NUM> receives the converted signal CI related to the image signal IS from the receiver <NUM> and determines whether to force a color setting of the converted signal CI. If the processor <NUM> determines to force the color setting of the converted signal CI, proceed to step S207. Otherwise, proceed to step S205.

In the detail of forcing color operations, the processor <NUM> may determine whether to force a color setting of the converted signal CI according to the EOTF, and thus the processor <NUM> may further execute the calibrations on a gamma curve and a Hue-Saturation-Gain (HSG) color setting. For example, if the EOTF indicates that the converted signal CI related to the image signal IS is corresponded to the HLG-HDR class, the processor <NUM> determines to force the color setting of the converted signal CI to a color setting corresponding to a HLG-HDR gamma curve and a HDR HSG color setting, wherein the HSG color setting may be described in the form of Hue-Saturation-Lightness (HSL) color model, Hue-Saturation-value (HSV) model, or Color Coordinate Adjustment (CCA) model. However, if the EOTF indicates that the converted signal CI related to the image signal IS is corresponded to a SDR class or a non-HLG-HDR class, the processor <NUM> determines to configure the color setting of the converted signal CI to a color setting corresponding to a SDR gamma curve and a SDR HSG color setting. In some embodiment, the color model can be Luma plus chroma/chrominance other than Cylindrical transformations, such as YUV.

In some embodiments, the processor <NUM> may determine whether to force a color setting of the converted signal CI according to a default setting or a control command which is generated in response to an input operation performed by a user of the projector <NUM> through an input device. In some embodiment, parameters of the color setting of the converted signal CI are designed to corresponding with the hardware restriction of the projector <NUM>, such as image brightness, contrast ratio, resolution, and/or color saturation e.g.. Furthermore, parameters of the color setting of the converted signal CI is related to the hardware restrictions of the light source module <NUM>, the color conversion module <NUM>, and the light valve <NUM>. Thus, the processor <NUM> may control them based on the parameters, and able to display HLG-HDR images or non-HLG-HDR images in a proper way.

In step S205, the processor <NUM> selects a SDR gamma curve from a plurality of gamma curves, and performs, on the converted image signal CI, a gamma correction according to the SDR gamma curve, so as to generate a corrected image signal. In other words, the processor <NUM> performs a gamma correction on the converted image signal according to the metadata to generate a corrected image signal.

In step S206, the processor <NUM> configures a parameter value corresponding to a color model. In some embodiments, said color model corresponds to the SDR HSG color setting as shown in Table <NUM>. In some embodiment, each gamma curve is corresponding to a color model. Nevertheless, the disclosure is not limited thereto. That is, the color space of the image signal IS will correspond to a color model, and the processor <NUM> configures the parameter value corresponding to the color model according to the electro-optical transfer function.

In step S207, the processor <NUM> selects a HLG-HDR gamma curve from a plurality of gamma curves, and performs, on the converted image signal CI, a gamma correction according to the HLG-HDR gamma curve, so as to generate a corrected image signal.

In step S208, the processor <NUM> configures values of parameters corresponding to a color model. In some embodiments, said color model corresponds to the SDR HSG color setting as shown in Table <NUM>. In some embodiment, each gamma curve is corresponding to a color model. Nevertheless, the disclosure is not limited thereto.

In step S209, the processor <NUM> transfers the corrected image signal into an optical signal OS.

In step S210, the color conversion module <NUM> and the light valve <NUM> respectively modulate the light beam LB emitted by the light source module <NUM> and the illumination beam LB' according to the optical signal OS received from the processor <NUM>, so as to form an image light beam IB.

In step S211, the projection lens <NUM> disposed on a transmission path of the image light beam IB projects the image light beam IB.

In view of the foregoing, the projector provided by the disclosure determines the class of the image signal according to the metadata of the image signal. The projector is capable of converting a color space of the image signal to generate a converted image signal, selecting a gamma curve corresponding to the converted image signal, and performing a gamma correction on the converted image according to the gamma curve so as to project a HLG-HDR-liked image light beam. In this way, without raising the cost of the projector, the image light beam can be projected with a proper color gamut no matter what class the image signal is, and a projector which does not support HLG-HDR class can project a HLG-HDR-liked image light beam when the image signal is in HLG-HDR class, wherein the HLG-HDR-liked image light beam corresponds to a gamma curve similar to HLG-HDR class.

<FIG> is a schematic view illustrating a comparison between an image with HLG-HDR class projecting by a conventional DLP projector (or projector does not support decoding an EOTF in a Dynamic Range and Mastering InfoFrame) and an image with HLG-HDR class projecting by the projector <NUM> as disclosed in the present disclosure. Since the conventional DLP projector cannot convert a color space or perform a gamma correction according to the EOTF, the conventional DLP projector will process the image signal with HLG-HDR class in a similar manner of processing the image signal with SDR class. Improperly processing of the image signal may significantly affect the performances of color and gray channels of the image light beam <NUM>. Thereby, it seems like the image light beam <NUM> is covered by fog. On the contrary, the image light beam <NUM> projecting by the projector <NUM> converts a color space and performs a gamma correction on the image signal with HLG-HDR class according to the EOTF. Thereby, the projector <NUM> can project the HLG-HDR-liked image light beam <NUM> the performances of color and gray channels of which are as good as the image light beam projected by a HLG-HDR-supported projector.

Claim 1:
A projector (<NUM>) for projecting an image light beam (IB) according to an image signal (IS), comprising:
a receiver (<NUM>) configured to:
receive the image signal (IS) and decode the image signal (IS) to obtain a metadata of the image signal (IS), wherein the metadata indicates an electro-optical transfer function corresponding to the image signal (IS);
determine, according to the metadata, whether the image signal (IS) is a HLG-HDR signal; and
convert, if the image signal (IS) is the HLG-HDR signal, a color space of the image signal (IS) from a wider color gamut to a narrower color gamut so as to generate a converted image signal (CI);
a processor (<NUM>) coupled to the receiver (<NUM>) and configured to:
receive the converted signal (CI) related to the image signal (IS) from the receiver (<NUM>) and determine whether to force a color setting of the converted signal (CI);
if the processor (<NUM>) determines to force the color setting of the converted signal (CI), select a HLG-HDR gamma curve from a plurality of gamma curves, and perform, on the converted image signal (CI), a gamma correction according to the HLG-HDR gamma curve, so as to generate a corrected image signal;
otherwise, select a SDR gamma curve from a plurality of gamma curves, and perform, on the converted image signal (CI), a gamma correction according to the SDR gamma curve, so as to generate a corrected image signal; and
transfer the corrected image signal into an optical signal (OS);
a light source module (<NUM>) coupled to the processor (<NUM>) and providing a light beam (LB);
a color conversion module (<NUM>) coupled to the processor (<NUM>) and disposed on a transmission path of the light beam (LB), wherein the color conversion is configured to modulate, according to the optical signal (OS), the light beam to an illumination beam (LB');
a light valve (<NUM>) coupled to the processor (<NUM>) and disposed on a transmission path of the illumination beam (LB'), wherein the light valve (<NUM>) is configured to modulate, according to the optical signal (OS), the illumination beam (LB') to form the image light beam (IB); and
a projection lens (<NUM>), disposed on a transmission path of the image light beam (IB) and projecting the image light beam (IB).