BACKGROUND OF THE INVENTION

Technical Field

This invention relates generally to thermal compensation, and more particularly to thermal compensation in image projectors.

Background

Improved contrast can be achieved in a projection system by modulating the illumination light incident on the spatial light modulators (SLMs) of the projection system. For example, if a pixel of an SLM is to display 5% brightness and is illuminated at full brightness (100%), then the pixel must attenuate 95% of the illumination light. Light leakage inherent in most SLMs makes it difficult to achieve dark levels when significant attenuation is required. On the other hand, if the pixel is illuminated at 10% brightness, then the pixel need only attenuate 50% of the incident light to achieve a 5% brightness level, and light leakage by the pixel is much less significant.

In order for the pixel to achieve accurate display levels, the intensity of the light incident on the pixel must be known with a high degree of precision. If the intensity of the incident light varies from the expected intensity, the output of the pixel will also vary, thereby degrading the quality of the projected image.

SUMMARY

Projectors require a significant amount of energy during operation, especially projectors for venues with large screens. High brightness projectors further increase the light energy requirements. The dissipation of energy in such projectors generates a significant amount of heat, which the inventors have determined causes physical changes in the components of the projector. The inventors have also determined that the physical changes in the components of the projector can affect the intensity of light incident on the pixels of light modulator(s) in the projectors and degrade the quality of the projected image.

The present invention overcomes the problems associated with the prior art by providing a projector capable of compensating for thermal changes in the components of the projector. The invention facilitates more precise lightfield modeling and, therefore, higher quality projected images.

An example image projector includes an image data input, a controller, a light source, illumination optics, an imaging spatial light modulator (SLM), and imaging optics. The image data input receives image data. The controller is coupled to receive the image data and is operative to determine a thermal state of the image projector. The controller also adjusts the image data depending on the thermal state of the image projector to generate thermally adjusted image data. The light source is operative to emit an illumination beam. The illumination optics are disposed in the path of the illumination beam and operative to convert the illumination beam into a lightfield. The imaging spatial light modulator is coupled to receive the thermally adjusted image data from the controller, is disposed to receive the lightfield, and is operative to modulate the lightfield responsive to the thermally adjusted image data to generate an imaging beam. The imaging optics are disposed in the path of the imaging beam and operative to focus the imaging beam on a viewing surface.

The light source includes a plurality of individual emitters. In a particular embodiment, the individual emitters are separately controllable. In an even more particular embodiment, the individual emitters are pixels of an illumination spatial light modulator (SLM) coupled to receive illumination data from the controller and operative to modulate the illumination beam depending on the illumination data. The controller is operative to generate the illumination data from the image data and provide the illumination data to the illumination SLM. In addition, the controller is operative to update the thermal state of the image projector, based at least in part on the illumination data, and adjust the image data depending on the updated thermal state of the image projector to generate the thermally adjusted image data.

In an example embodiment, a set of thermal sensors is coupled to provide temperature data to the controller. The thermal state of the image projector is determined by the controller based at least in part on the temperature data. The projector includes an air intake for drawing air into the image projector to cool the image projector, and at least one of the thermal sensors is disposed to sense the temperature of the air drawn into the image projector. Another of thermal sensors is disposed to sense the temperature within the light source. Yet another of the thermal sensors is coupled to an optics mount of the illumination optics. The thermal state of the image projector is determined by the controller based at least in part on content of the image data and, optionally, on the input from the thermal sensors.

In an example embodiment, the thermal state of the image projector is determined by the controller based at least in part on a prior thermal state of the image projector. The thermal state of the image projector is also determined by the controller based at least in part on content of the image data. For example, the thermal state of the image projector is determined by the controller based at least in part on an average of intensity values of the image data. The controller employs a temporal filter to determine the thermal state of the image projector.

In example embodiments, the light source includes a plurality of emitters. The emitters are divided into groups, and each group is associated with a corresponding portion of the lightfield. The thermal state of the image projector includes a separate thermal state for each group of the emitters. Optionally, the thermal state of the image projector includes a plurality of thermal states for each group of the emitters. The emitters are pixels of a spatial light modulator, and the controller is operative to determine the separate thermal state(s) for each group of emitters based at least in part on the separate thermal states of adjacent groups of the emitters.

In an example embodiment, the controller is configured to adjust the image data depending on the thermal state of the projector by creating a model of the lightfield, based at least in part on the thermal state of the image projector, and adjusting the image data based on the model of the lightfield. The light source includes a plurality of individual emitters, and the controller is configured to select a point spread function associated with each of the individual emitters based on the thermal state of the projector. The controller then convolves the selected point spread functions to create the model of the lightfield. Shapes of the point spread functions vary depending on the thermal state of the image projector. In addition, positions of the point spread functions vary depending on the thermal state of the image projector.

Creating the model of the lightfield based at least in part on the thermal state of the image projector also includes creating a different color specific model of the lightfield for each of a plurality of different colors depending on the thermal state of the projector. The controller is configured to select the point spread functions based at least in part on the different colors.

In an example embodiment wherein the emitters are divided into groups, each group is associated with a corresponding portion of the lightfield. The thermal state of the image projector includes a separate thermal state for each group of the emitters, and the point spread functions are selected based on which particular group a corresponding emitter is a member of and also based on the separate thermal state associated with the particular group. Optionally, the thermal state of the image projector includes at least two separate thermal states for each group of the emitters. The controller selects a point spread function of a particular shape depending on a first of the thermal states associated with an emitter's group, and the controller determines a displacement of the selected point spread function depending on a second of the thermal states associated with the emitter's group. In addition, the plurality of emitters includes pixels of an illumination SLM, and the point spread functions are selected based at least in part on illumination data provided to the illumination SLM by the controller.

Example embodiments of the image projector include a plurality of predefined thermal states spanning the operating temperature range of the projector. The controller is configured to determine thermal states of the image projector by selecting ones of the predefined thermal states.

Optionally, the thermal state of the projector is updated responsive to every frame of the image data.

An example method of driving a spatial light modulator in a projector is also disclosed. The method includes receiving image data to be displayed by the spatial light modulator (SLM) and determining a thermal state of the projector. The method further includes adjusting the image data based on the thermal state of the projector to generate thermally adjusted image data and providing the thermally adjusted image data to the SLM. The method further includes generating illumination data based on the image data, and providing the illumination data to a light source configured to illuminate the SLM based on the illumination data. The method further includes updating the thermal state of the projector based on the illumination data to generate an updated thermal state of the projector and adjusting subsequent image data based on the updated thermal state of the projector.

A particular example method includes receiving temperature data from a thermal sensor set. Then, determining the thermal state of the projector includes determining the thermal state of the projector based at least in part on the temperature data. Receiving the temperature data from the thermal sensor set includes receiving temperature data indicative of the temperature of ambient air flowing into the projector. Receiving the temperature data from the thermal sensor set also includes receiving temperature data indicative of the temperature of a component of a light source configured to illuminate the SLM. Receiving the temperature data from the thermal sensor set also includes receiving temperature data indicative of the temperature of optics disposed between the SLM and a light source configured to illuminate the SLM. In addition, determining the thermal state of the projector includes determining the thermal state of the projector based at least in part on content of the image data.

In an example method, determining the thermal state of the projector includes determining the thermal state of the projector based at least in part on content of the image data and/or determining the thermal state of the projector based at least in part on a prior thermal state of the image projector. In addition, determining the thermal state of the projector further includes receiving temperature data from a thermal sensor set and determining the thermal state of the projector based at least in part on the temperature data. Determining the thermal state of the projector also includes temporal filtering and determining the thermal state of the projector based at least in part on average intensity values of the image data.

In an example method, determining the thermal state of the projector includes defining groups of individual emitters illuminating the SLM and determining a separate thermal state for each of the groups of individual emitters. Determining the thermal state of the projector can also include determining a plurality of separate thermal states for each of the groups of individual emitters. Defining groups of individual emitters illuminating the SLM includes defining blocks of pixels of an illuminating spatial light modulator. Optionally, determining the separate thermal state for each of the groups of individual emitters includes determining the separate thermal state for each of the groups of individual emitters based at least in part on the separate thermal states of adjacent groups of the emitters.

In a particular example method, adjusting the image data based on the thermal state of the projector includes determining characteristics of an illuminating lightfield incident on the SLM based at least in part on the thermal state of the projector and, then, adjusting the image data based on the characteristics of the illuminating lightfield. In addition, determining characteristics of the illuminating lightfield includes selecting a point spread function associated with each of a plurality of emitters illuminating the SLM based on the thermal state of the projector and convolving the selected point spread functions to create a model of the illuminating lightfield. Shapes and positions of the point spread functions vary depending on the thermal state of the projector.

In a more particular example method, determining characteristics of the illuminating lightfield includes creating a different color specific model of the lightfield for each of a plurality of different colors depending on the thermal state of the projector. Selecting the point spread functions includes selecting the point spread functions based at least in part on the different colors.

In an example method, selecting a point spread function associated with each of the plurality of emitters includes defining groups of the emitters, each group being associated with a corresponding portion of the illuminating lightfield. Determining a thermal state of the projector includes determining a separate thermal state for each group of the emitters. In addition, selecting the point spread functions includes selecting the point spread functions depending on which particular group a corresponding emitter is a member of and also depending on a separate thermal state associated with the particular group. Optionally, in the example method, determining the thermal state of the projector includes determining at least two separate thermal states for each group of emitters. Determining characteristics of the illuminating lightfield includes selecting a point spread function of a particular shape depending on a first of the thermal states associated with an emitter's group and determining a displacement of the selected point spread function depending on a second of the thermal states associated with the emitter's group.

In an example method, the plurality of emitters include pixels of an illumination SLM, and selecting the point spread functions includes selecting the point spread functions depending at least in part on illumination data provided to the illumination SLM.

Example methods also include updating the thermal state of the projector each time a frame of the image data is received.

In some example methods, determining the thermal state of the projector includes receiving a plurality of predefined thermal states spanning the operating temperature range of the projector and selecting particular ones of the predefined thermal states.

Another example image projector includes an image data input for receiving image data, a light source operative to emit an illumination beam, and illumination optics disposed in the path of the illumination beam and operative to convert the illumination beam into a lightfield. In addition, the example image projector includes means for adjusting the image data based on a thermal state of the projector to generate thermally adjusted image data and an imaging spatial light modulator coupled to receive the thermally adjusted image data. The imaging spatial light modulator is disposed to receive the lightfield and is operative to modulate the lightfield responsive to the thermally adjusted image data to generate an imaging beam. Imaging optics are disposed in the path of the imaging beam and operative to focus the imaging beam on a viewing surface.

An example non-transitory, electronically-readable medium is also disclosed, The non-transitory electronically readable medium has code embodied therein which, when executed by a processor, will cause an electronic device to receive image data to be displayed by a spatial light modulator (SLM), determine a thermal state of a projector, adjust the image data based on the thermal state of the projector to generate thermally adjusted image data, and provide the thermally adjusted image data to the SLM.

An example system for configuring a projector for thermal compensation is also disclosed. The example system includes memory for storing data and code and an image data source configured to provide thermally stabilizing image data and test image data to the projector. The thermally stabilizing image data defines stabilizing images for stabilizing the projector in particular thermal states. The test image data defines one or more test images. The system additionally includes an image capture device configured to capture the test image(s) projected by the projector and a controller. The controller is operative to cause the projector to display a first one of the stabilizing images for a time sufficient to stabilize the projector in a first one of the thermal states, to cause the projector to display a test image when the projector is in the first one of the thermal states, and to cause the image capture device to capture an image of the test image projected by the projector when the projector is in the first one of the thermal states. The controller is additionally operative to cause the projector to display a second one of the stabilizing images for a time sufficient to stabilize the projector in a second one of the thermal states, cause the projector to display the test image when the projector is in the second one of the thermal states, and cause the image capture device to capture an image of the test image projected by the projector when the projector is in the second one of the thermal states. The controller is also operative to analyze the captured test images to determine changes in an illumination source of the projector associated with the second thermal state relative to the first thermal state and to store a record in the memory associating the changes with the second thermal state.

In the example system, certain ones of the stabilizing images each defines a particular uniform intensity across an entire image. The particular uniform intensity is a percentage of maximum brightness that corresponds to a particular one of the thermal states.

Optionally, at least one of the stabilizing images defines a different uniform intensity for multiple regions across an image. Each the uniform intensity is a percentage of maximum brightness that corresponds to a particular one of the thermal states associated with each of the regions.

In the example system, the record associating the changes with the second thermal state includes data indicative of characteristics of a point spread function associated with a light source of the projector. The data indicative of the point spread function includes data indicative of a shape of the point spread function and/or data indicative of a displacement of the point spread function.

An example method of configuring a projector for thermal compensation is also disclosed. The example method includes placing the projector in a first thermal state, causing the projector to display a test image while in the first thermal state, and capturing the test image displayed while the projector is in the first thermal state. The example method additionally includes placing the projector in a second thermal state, causing the projector to display a test image while in the second thermal state, and capturing the test image displayed while the projector is in the second thermal state. The example method additionally includes analyzing the captured test images to determine changes in an illumination source of the projector associated with the second thermal state relative to the first thermal state and generating configuration data associating the changes with the second thermal state.

A more detailed example method includes placing the projector in additional thermal states, causing the projector to display a test image while in each of the additional thermal states, and capturing the test images while the projector is in each of the additional thermal states. The method additionally includes analyzing the captured test images to determine changes in the illumination source of the projector associated with the additional thermal states relative to the first thermal state and generating configuration data associating the changes with the additional thermal states.

In a particular example method, the step of placing the projector in the first thermal state includes causing the projector to display a first predetermined image for a time sufficient to place the projector in the first thermal state. The first predetermined image includes a first spatially constant intensity level corresponding to the first thermal state. In addition, the step of placing the projector in the second thermal state includes causing the projector to display a second predetermined image for a time sufficient to place the projector in the second thermal state. The first predetermined image includes an average intensity level corresponding to the first thermal state, and the second predetermined image includes an average intensity level corresponding to the second thermal state.

In one example method, the step of analyzing the captured test images includes determining a point spread function for each of a group of emitters of the illumination source.

In a particular example method, the step of analyzing the captured test images includes determining a first point spread function associated with the first thermal state for each of the emitters and determining a second point spread function associated with the second thermal state for each of the emitters. The step of generating configuration data includes storing the first point spread functions in association with the emitters and the first thermal state and storing the second point spread functions in association with the emitters and the second thermal state.

The step of analyzing the captured test images optionally includes determining displacements of the second point spread functions relative to corresponding ones of the first point spread functions.

An example configuration method additionally includes receiving input from thermal sensors associated with the projector and defining the thermal states based at least partially on the input.

The example configuration methods further include providing the configuration data to the projector.

