Adaptive brightness dynamic regulation and control method for ambient light of projection table lamp

Abstract

The invention discloses a projection table lamp ambient light adaptive brightness dynamic regulation and control method, and relates to the technical field of projection illumination control, and the method comprises the steps: sequentially executing multi-source illumination and image collection, and carrying out the modeling of a reading region, a projection region, a background region and a sight line path region; eye use risk indexes accumulated along with time are calculated according to indexes such as read-write illumination and myopia prevention and control standard contrast, contrast and the like, and then safety constraints and light environment targets of all areas are set in combination with task scenes such as paper reading, mixed learning, projection interaction, video watching, desktop office and the like. Unified luminous flux budgeting and regional light distribution are performed on an illumination light source and a projection light source under eye use risk constraint, brightness is adjusted according to risk gears in a grading manner, ambient light and user manual adjustment behaviors are recorded to update parameters, and dynamic light environment control considering eye use safety, paper reading definition and projection visibility in different scenes is realized. And the long-term use comfort is improved.

Description

Technical Field

[0001] This invention relates to the field of projection lighting control technology, specifically a method for dynamic brightness adjustment of a projection desk lamp based on ambient light adaptation. Background Technology

[0002] With the popularization of online and interactive learning, projection lamps are widely used in children's desks and classroom desktops. When children complete paper-based homework on their desks, they often use desktop projectors to view questions or courseware. The reading and writing area requires illuminance and uniformity, while the projection area requires a certain level of brightness and contrast. During study, changes in natural light, indoor ceiling lights, curtain opening and closing, and posture constantly alter the lighting conditions of the reading / writing area, projection area, and background area. Existing smart desk lamps mostly automatically adjust their brightness based on the ambient illuminance at a single point, while existing projection devices mostly adjust the light source and image based on the overall room brightness. Some projection lamps integrate lighting and projection, but the lighting and projection components are still controlled separately, lacking a solution for adjusting the lighting environment specifically for this type of desktop scenario.

[0003] In this integrated usage environment, existing lighting environment control technologies have several limitations.

[0004] First, automatic dimming often corresponds to single-point ambient light or single-area illuminance, failing to differentiate between the different lighting conditions of the reading / writing area, the projection area, and the background area. Lowering the overall illuminance to increase projection contrast often results in the paper being too dark, while increasing lamp output to increase desktop illuminance can lead to an overly bright projection background and a shallow image. Second, the control focus is on illuminance or image contrast at a specific moment, failing to quantify the accumulated eye strain on children under prolonged exposure to high brightness, high contrast, or uneven illuminance. Dimming prioritizes immediate comfort or energy saving, failing to reflect the long-term requirements of myopia prevention standards regarding illuminance range, uniformity, and light quality. Third, in situations with rapid changes in ambient light or user posture, existing automatic dimming typically adjusts lamp or projection brightness based on ambient illuminance, lacking tiered responses and transitions to address differences between reading / writing tasks and projected content. This can cause frequent shifts in desktop and projection brightness within a short period, repeatedly interrupting children's visual adaptation. Currently, the use of projector lamps for reading, writing, and interactive teaching in homes and schools is increasing. If the above problems are not effectively solved, it will be difficult to balance the illumination of paper reading and writing with the visibility of projected images. The eye risks of children in dynamic lighting environments are difficult to assess and effectively control, which is detrimental to vision protection and learning outcomes in the long run.

[0005] Therefore, the technical problem to be solved is:

[0006] When using a projector lamp in a child's reading, writing, and interactive learning scenario, how can the lighting distribution of two reading / writing areas and two projection viewing areas be coordinated on the same device to maintain reasonable illuminance for reading / writing in both areas and sufficient brightness and contrast in both projection viewing areas, thereby limiting the eye load on children within a certain time period and preventing brightness changes and adverse light environments caused by automatic dimming? Summary of the Invention

[0007] (a) Technical problems to be solved

[0008] To address the shortcomings of existing technologies, this invention provides a dynamic brightness control method for adaptive ambient light of a projection desk lamp. It calculates an eye-use risk index accumulated over time based on indicators such as contrast ratio and contrast ratio according to reading and writing lighting and myopia prevention standards. Then, it sets safety constraints and light environment targets for each area in conjunction with task scenarios such as paper reading, blended learning, projection interaction, video viewing, and desktop office work. Under the eye-use risk constraints, it performs unified luminous flux budgeting and regional light distribution for both the lighting source and the projection source, and adjusts brightness according to risk levels. It also records ambient light and user manual adjustment behavior to update parameters, achieving dynamic light environment control that balances eye safety, paper reading clarity, and projection visibility in different scenarios, while improving long-term user comfort; thus solving the technical problems described in the background art.

[0009] (II) Technical Solution

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] The method for adaptive brightness control of a projection desk lamp includes: in each control cycle, collecting illumination and images through an ambient light sensor and a camera, identifying the reading area, projection viewing area, background area and viewing path area, and obtaining the illuminance or brightness and contrast of each area.

[0012] Based on reading and writing lighting and myopia prevention standards, the illuminance or brightness and contrast of the area are converted into multiple risk factors. The risk factors are weighted over time within a preset time window to obtain the eye use risk index.

[0013] The current task scenario is determined based on the camera footage and application operation status, and safety constraints and light environment targets related to the illuminance or contrast of each area are set based on the task scenario and eye risk index.

[0014] The maximum total luminous flux is determined based on the eye risk index and its allowable upper limit. Under the constraint of the maximum total luminous flux, the target luminous flux of the lighting source and the target luminous flux of the projection source are calculated in combination with the light environment target and the regional model.

[0015] Based on the eye risk index, a dynamic adjustment strategy is selected. The output brightness of the lighting channel and the projection channel is adjusted according to the target luminous flux of the lighting source and the target luminous flux of the projection source. The ambient light, task scene and luminous flux allocation results are recorded to update the control parameters for subsequent control cycles.

[0016] Furthermore, based on the image, the reading plane and the projection view plane are fitted by detecting the book edge and the projection view contour. The desktop area other than the reading area and the projection view area is divided into the background area, and the area containing the user's eye projection onto the desktop is divided into the gaze path area. These are used for subsequent illumination estimation and to form region labels in the controller. The background area and the gaze path area are stored in a region mapping table with corresponding pixel positions.

[0017] Furthermore, an ambient light sensor is arranged around the lamp head of the projection table to obtain the intensity of incident light from different directions. The camera is installed close to the projection light path. The output of the ambient light sensor is synchronously acquired with the image from the camera and stored in the control chip in association with the area division results within the same control cycle. The sampling time of the ambient light sensor and the camera is aligned with the start and end of the control cycle.

[0018] Furthermore, the risk factors include at least a first risk factor based on the deviation of the illuminance in the reading area from the reading and writing lighting standard, a second risk factor based on the uniformity of illuminance, a third risk factor based on the proportion of blue light components, and a fourth risk factor based on the flicker amplitude and the brightness of the viewing path area. The eye use risk index is a weighted combination of the risk factors and is recalculated in each control period.

[0019] Furthermore, the preset time window covers multiple consecutive control periods, and the weighted accumulation adopts a decreasing weight sequence that gives greater weight to the most recent control period, so that newer risk factors contribute more to the eye use risk index, and the eye use risk index value remains stable under the limitation of the total weight. The length of the time window can be configured according to age group.

[0020] Furthermore, the task scenarios include at least paper reading scenarios, mixed learning scenarios combining paper and projection, interactive scenarios primarily using projection, and desktop office scenarios primarily using keyboard input.

[0021] The determination of the task scenario is based on a comprehensive assessment of the paper outline in the camera image, the proportion of the projected view, and the foreground state of the application, and the lighting environment constraints are reset when the scenario is switched.

[0022] Furthermore, for paper-based reading scenarios, the upper limit of the allowable risk to eyes is lower than in other scenarios, and the illuminance target for the reading area is higher than the illuminance target for the projection viewing area;

[0023] For interactive scenarios where projection is the primary mode of viewing, the contrast target of the projection viewing area is higher than the illuminance target of the reading area, and the brightness constraints of the background area and the viewing path area are adjusted accordingly. The constraints and targets are stored in the form of a parameter table.

[0024] Furthermore, the maximum total luminous flux decreases monotonically as the eye risk index increases. When the eye risk index is below a preset threshold, the maximum total luminous flux is allowed to approach the rated luminous flux of the device. When the eye risk index approaches the upper limit of the eye risk, the maximum total luminous flux is compressed to a preset safe range. The preset threshold is related to the length of the time window.

[0025] Furthermore, the lighting source includes a first light subarray covering the reading area and a second light subarray covering the background area. The target luminous flux of the lighting source is first allocated to the first light subarray to meet the illuminance constraints of the reading area, and the remaining part is then allocated to the second light subarray and the ambient lighting area. The allocation ratio is preset in the factory calibration.

[0026] Furthermore, when the eye risk index is significantly lower than the upper limit of the eye risk tolerance, the luminous flux of each channel slowly approaches the corresponding target luminous flux in small steps. When the eye risk index approaches the upper limit of the eye risk tolerance, the luminous flux of the lighting source and the projection source is adjusted in a decreasing direction in larger steps, with the step size determined by a pre-set level factor.

[0027] Furthermore, when the eye risk index exceeds the upper limit of the allowable eye risk, the luminous flux of the projection light source is immediately reduced and the luminous flux of the lamp subarray corresponding to the line of sight path area is reduced at the same time. While the luminous flux is reduced, a posture adjustment or short rest prompt is output to the user, and the upper limit of the allowable eye risk is reduced in the subsequent time window, so that the maximum total luminous flux in the subsequent control cycle remains at a low level.

[0028] Furthermore, the recorded eye risk index, task scenario sequence, and light flux allocation results are used to update the weight parameters of risk factors and the target parameters of the light environment offline or online. When the same user uses the device for a long period of time, the weight parameters and target parameters are slightly adjusted based on the user's multiple manual adjustments of the direction, and the adjustment results are stored in local non-volatile memory.

[0029] Furthermore, the duration of the control cycle is no greater than a preset multiple of the projection screen refresh cycle. The ambient light sensor and the camera each complete at least one sampling and image acquisition within each control cycle, so that all calculations are completed based on the data acquired within the same control cycle, and the control parameters are continuously transmitted between control cycles. The duration of the control cycle is configured by software parameters during the manufacturing stage and can be selected according to different user profiles.

[0030] (III) Beneficial Effects

[0031] This invention provides a method for dynamically adjusting the ambient light adaptive brightness of a projection lamp, which has the following beneficial effects:

[0032] This system employs an ambient light sensor paired with a camera to simultaneously collect illumination and image data, segmenting the reading area, projection area, background area, and line-of-sight path area. A lighting environment model is then established to enable overall lamp control and illumination adjustment around these areas. It simultaneously considers the needs of paper reading, projection display, and the surrounding environment on the same desktop, resolving issues such as excessively dark reading / writing areas due to single-point metering or interference from desktop reflections in the projection area. Based on reading and writing lighting standards and myopia prevention requirements, reading illuminance, illuminance uniformity, projection visual contrast, blue light component, flicker, and line-of-sight path glare are uniformly converted into an eye risk index, incorporating the exposure time dimension. This allows for a shift from static threshold comparisons to risk constraints throughout the entire process, limiting subsequent luminous flux budgeting and brightness adjustment. Under prolonged use, this effectively addresses the technical problem of traditional lamps that only consider instantaneous illuminance and cannot reflect the burden on eyes during extended periods of use.

[0033] Based on camera footage and application operation status, the system identifies various learning scenarios, including paper reading, paper-projection hybrid learning, projection viewing, video viewing, and desktop office tasks. By acquiring the eye risk index and regional optical indicators, it sets the upper limit of eye risk tolerance, the minimum illuminance in the reading area, the minimum visible contrast in the projection viewing area, and the corresponding light environment targets. The system also aligns the task scenario identification results with safety constraints and target parameters, collaboratively addressing the problem that simply setting "reading mode" and "projection mode" in existing devices makes it difficult to accommodate different learning modes.

[0034] Based on the eye risk index and task scenario, the maximum total luminous flux is calculated. Under this constraint, a unified luminous flux budget is performed on the lighting source and the projection source. The target luminous flux of the lighting source is first allocated to the light subarray covering the reading area, and then allocated to the background and ambient lighting. The target luminous flux of the projection source is allocated to the projection viewing area, thereby realizing integrated light distribution for lighting and projection. This avoids the problem of lighting and projection being adjusted independently and competing for brightness space in traditional systems, and improves the coordinated matching ability of paper reading illuminance and projection contrast.

[0035] Different dynamic adjustment methods are selected based on the eye risk index and its changing trend. By setting multiple brightness change step sizes and shrinkage rules, the brightness can quickly approach the target brightness when the eye risk is low, and quickly shrink the brightness of the projection light source and the light along the line of sight when the eye risk approaches or exceeds the allowable value. During the control cycle, changes in ambient light, task scene sequence and manual adjustment behavior are recorded to correct the risk weight and target parameters. The linkage from single-time to cross-cycle overcomes the buffering effect of traditional automatic dimming when there are sudden changes in risk or brightness. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the dynamic brightness adjustment method for adaptive ambient light of the projection lamp according to the present invention. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Please see Figure 1 This invention provides a method for dynamically adjusting the ambient light adaptive brightness of a projection lamp, including:

[0039] Step 1: In each control cycle, transform the multi-source information related to the light environment in the desktop space where the projector lamp is located into a light environment area model with a clear structure and complete parameters, so that the reading plane, projection viewing plane, background area and viewing path area have quantifiable illuminance and brightness descriptions in the same coordinate system.

[0040] When a projection lamp is used in a children's desk setting, the reading area, projection viewing area, and background area are affected by the combined effects of natural light, indoor ceiling light, and the lamp's own light source. It is difficult for any single sensor output to fully reflect the lighting conditions of each area.

[0041] By synchronously acquiring signals from multiple sources, the ambient light sensor current value, the camera image grayscale distribution, and the projector lamp's own operating status are combined into a set of time-aligned observations, providing a unified input for subsequent geometric mapping and regional physical quantity calculations. Only by summarizing the above information at the same sampling moment can the misalignment of the current image with past illuminance be avoided when subsequently calculating the illuminance of the reading area and the brightness of the projection viewing area based on geometric relationships. This prevents calculation errors that cannot be eliminated when children move or when external light changes abruptly.

[0042] Using the control cycle as the time unit, a unified time stamp is established for all hardware involved in the observation at the beginning of each control cycle. Then, ambient light sensor sampling and camera image acquisition are completed sequentially within a fixed sampling window.

[0043] At the end of the sampling window, the controller correlates the current values ​​of the multi-channel ambient light sensor acquired within the sampling window with the current image frame to form a sampling vector representing the optical state of this control cycle. Each component in this sampling vector maintains a correspondence with the same image frame, ensuring strict temporal consistency between the reading area and projection viewing area subsequently identified on the image plane and the actual illuminance and brightness measurements.

[0044] The controller samples multiple ambient light sensors sequentially, setting monotonically increasing sampling times within a control cycle, and incorporating each sampling result into the observation set for that control cycle. Simultaneously, the camera captures a single image frame at the middle of the ambient light sensor's sampling window. The average illumination field during the image exposure period is the same as the illumination state within the sampling window. The controller then constructs a sampling vector from the multi-source observations at the end of the control cycle, as shown in the following equation:

[0045]

[0046] Wherein, sampling vector : During the control cycle sampling time The resulting multi-source observation column vector;

[0047] Current component : For the first ambient light sensor at time The current value, current components For the second ambient light sensor at time The current value, current components For the third ambient light sensor at time The current value, and the current component is a non-negative current within the allowable output range of the ambient light sensor;

[0048] Luminance component : The average grayscale value of the candidate reading region in the camera image, and the brightness component. The average grayscale value of the candidate region of the projection view area in the camera image is given, and the brightness component is a non-negative number within the grayscale range of the camera.

[0049] Time parameters : for the first The end time of each control cycle is a non-decreasing time sequence based on the controller time base.

[0050] In one specific implementation, the children's desk is approximately one meter wide. A projection lamp is installed on the right rear side of the desk. Three ambient light sensors are arranged along the front edge of the lamp base, facing the reading area, the projection viewing area, and the overall room direction, respectively. A camera is fixed above the projection lamp, facing the desktop. When the child sits down at the desk to start doing homework, the controller operates with a control cycle of approximately one-hundredth of a second. At the end of each control cycle, the current values ​​of the three ambient light sensors and the grayscale statistics of a single frame of desktop image are combined into a sampling vector. It is recorded in memory.

[0051] Without adding extra complex hardware structures, the multi-source data collected by the ambient light sensor and camera is organized into a unified sampling vector, enabling the controller to recover the optical state of each area from the data at the same time section. This avoids relying solely on the ambient light sensor or solely on image grayscale to infer illuminance from a single data source, allowing the projector lamp to still obtain basic observation results consistent with the scene even when facing rapid changes in natural light or slight movements of a child's body.

[0052] After the sampling vector is constructed, if the image coordinate system and the location of the ambient light sensor are not unified to the same desktop coordinate system, the recognition result of the reading plane cannot establish a definite relationship with the physical location corresponding to the ambient light sensor.

[0053] A desktop coordinate system is introduced to establish a one-valued mapping relationship between the pixel coordinates on the camera image plane and their actual positions on the desktop. Based on this mapping, the positions of the reading plane, the projection viewing plane, and the background area are fitted. This mapping relationship allows the sampling vector to be... The grayscale information and ambient light sensor current information are uniformly interpreted as illuminance or brightness at each location in the desktop coordinate system, providing a geometric basis for subsequent area division and physical quantity calculation.

[0054] During the initial calibration upon installation, the controller drives the projection light source to sequentially project regular calibration patterns, such as regular grids or polygons, onto the desktop. The camera acquires images of the calibration patterns, and by analyzing the relationship between the actual size of the calibration patterns and the pixel positions in the images, a mapping matrix from the image coordinate system to the desktop coordinate system is obtained.

[0055] After calibration, within each control cycle, the controller converts the pixel positions in the camera image into desktop coordinates using this mapping matrix, so that the reading plane and projection viewing plane can be subsequently divided in the desktop coordinate system. A homography matrix is ​​used to linearly map the image coordinates to the desktop coordinates. The controller represents the homogeneous coordinates of a pixel in the image as a column vector, and the homogeneous coordinates of the corresponding position on the desktop as another column vector, with the two linked by a mapping matrix:

[0056]

[0057] In the formula, the desktop coordinate vector : A homogeneous coordinate column vector of a point in the desktop coordinate system, with components being the desktop planar coordinates and scale components, and its value range limited by the physical dimensions of the desktop; Image coordinate vector : A homogeneous column vector of coordinates corresponding to pixels in the camera image plane, with components being pixel coordinates and scale components, and its value range limited by the image resolution; mapping matrix. : is a 3x3 homography matrix, consisting of a real matrix obtained during the calibration process, and the elements of the matrix remain fixed in the calibration scenario.

[0058] During the calibration phase, several calibration points with known planar coordinates are projected onto the desktop using a projection lamp. The camera captures their pixel coordinates, a system of linear equations is constructed, and the homography matrix is ​​calculated using the least squares method. Thus, during the runtime phase, desktop images can be utilized. Map any image pixel coordinates to desktop coordinates.

[0059] In one specific implementation, when the projection lamp is first installed, the parent places a calibration book flat on the table. The projection lamp projects bright marks onto the four corners of the book in a preset order. The camera exposes at each mark position, and the controller records the pixel position of the mark in the image and its actual coordinates printed on the book. The mapping matrix is ​​obtained by solving a system of linear equations. The matrix is ​​stored in non-volatile memory and reused in all subsequent control cycles. When the child uses workbooks of different thicknesses, the camera still operates based on the matrix. By mapping image coordinates to desktop coordinates, the controller constructs position descriptions of the reading plane and the projection viewing plane by finding connected regions at the edges of the paper in the desktop coordinate system.

[0060] When using it, make the sampling vector The grayscale components and the spatial layout of the ambient light sensor are expressed in the same desktop coordinate system. The controller can accurately calibrate the reading area in the desktop coordinate system, and the boundaries between the projection viewing area and the background area are clearly defined in the desktop coordinate system, which is beneficial for calculating the brightness and contrast of the projection viewing area separately in subsequent steps.

[0061] After establishing the desktop coordinate system, simply identifying the outline of the area where the paper is located is not enough to directly assess eye risk. The illuminance distribution inside the reading plane must be compressed into several regional indicators with clear physical meaning.

[0062] Therefore, the reading area boundary is defined using the paper outline in the desktop coordinate system, based on the sampling vector. The relationship between grayscale information and the spatial response of the ambient light sensor is used to estimate the local illuminance function at various locations within the reading area, and an average illuminance index for the reading area is constructed based on this. By expressing the highly non-uniform local illuminance field as a scalar of average illuminance in the reading area, the illuminance range specified in the reading and writing lighting standard can be directly compared in subsequent eye risk calculations, and this scalar can be used as a constraint in luminance budgeting.

[0063] The controller first constructs an integral domain of the reading area in the desktop coordinate system based on the outline of the paper, and then combines it with a mapping matrix. The grayscale distribution of the camera image is used to convert the image grayscale field into an illuminance distribution on the reading plane. Because there is a non-linear response between the camera grayscale value and the actual illuminance, the controller is calibrated for each grayscale level and illuminance measurement during installation. During operation, the calibration curve is used to convert the grayscale field into an illuminance field. The average illuminance of the reading area can be integrated as follows:

[0064]

[0065] Where: Illuminance of the reading area : Average illuminance scalar of the reading area, representing the overall illuminance level of the paper reading surface, a real number above 0; reading area : The area scalar of the reading region in the desktop coordinate system, used to normalize the integral result, is a positive real number; the integration domain The set of two-dimensional regions of the reading area in the desktop coordinate system, limiting the integration range;

[0066] Illuminance function Reading coordinates on the plane The local illuminance value at a given location is a real number greater than 0, calculated from the grayscale of the camera and the observations of the ambient light sensor through a calibration relationship.

[0067] One method is to use a univariate polynomial to fit the relationship between the camera's grayscale and local illumination. If the image is on a desktop... The gray level at that location is Then the local illuminance function for:

[0068]

[0069] Where the coefficient The coefficients are dimensionless gray values ​​obtained by least-squares fitting of gray values ​​collected under different known illuminance during factory calibration. , That is, the corresponding illuminance value is obtained by the control chip converting the gray level of each grid center point according to a polynomial during operation to obtain the local illuminance.

[0070] Calibration Phase: Multiple illuminance meters are arranged on the reading plane. The output of the luminaires is varied, and the corresponding grayscale and illuminance values ​​are collected. Those skilled in the art can obtain the grayscale-to-illuminance mapping curve through univariate or bivariate polynomial fitting or table lookup. Operation Phase: The reading area is divided into a regular grid. The grayscale of the center pixel of each grid is mapped to the local illuminance using the mapping curve, and then substituted into the trapezoidal integral for calculation. .

[0071] In use, the information originally scattered in image pixels and ambient light sensor current is converted into reading area illuminance with clear physical meaning. In subsequent steps, the illuminance is directly compared with the illuminance range specified in the reading and writing lighting standard to determine whether the reading area is in an illuminance state suitable for eye use; so that the subsequent calculation of the eye risk index is not affected by occasional small dark areas or bright spots.

[0072] Illuminance in the reading area Once obtained, without performing targeted optical index calculations on the projection viewing area and the viewing path area, it's impossible to simultaneously ensure both the clarity of printed reading and the visibility of the projected image in subsequent steps. Therefore, the projection viewing area is segmented based on a desktop coordinate system, and combined with image grayscale distribution and ambient light sensor observations, brightness contrast indices for the projection viewing area and illuminance indices for the viewing path area are calculated to describe the image depth and glare perceived by children when viewing projected content.

[0073] By compressing the brightness distribution of the projection viewing area into a contrast ratio and simultaneously obtaining the illuminance of the viewing path area, the need for clear image visibility and the limitation of not being too bright a direct light source can be comprehensively considered in the eye risk index and brightness budget. Therefore, the controller first utilizes a mapping matrix Transform the boundaries of the projected viewing area in the image to the desktop coordinate system to determine the extent of the projected viewing plane.

[0074] Within this range, a representative area is selected, and the maximum and minimum grayscale values ​​of the image are statistically analyzed. The maximum and minimum luminance values ​​within the projection viewing area are obtained through illuminance calibration relationships, and these values ​​are used to construct a contrast index. Furthermore, the controller calculates the average local illuminance function within the geometric range of the viewing path area, which represents the light intensity received near the child's eyes. The projection viewing area contrast can be expressed by the following formula:

[0075]

[0076] In the formula, the contrast ratio of the projection viewing area is... : This is a dimensionless contrast ratio indicator used to characterize the difference in brightness between projected content and actual brightness; its value ranges from 0 to 1; maximum brightness. : The maximum brightness value obtained through grayscale calibration within the projection area, taking a real number greater than or equal to 0; minimum brightness value. : The minimum brightness value obtained through grayscale calibration within the projection viewing area, taking a real number greater than 0 and not exceeding the maximum brightness value. .

[0077] When in use, the contrast of the projection viewing area In subsequent steps, the image can be compared with a preset minimum visible contrast to determine whether the current projected content has sufficient clarity, thus avoiding excessive grayscale in the image caused by simply increasing the illuminance of the reading area. In the subsequent eye risk calculation, it can identify scenarios where the reading area has moderate lighting but the eye is looking directly at the projection light path, which is too bright, thereby limiting the output of the projection light source when budgeting brightness.

[0078] Step 2: Based on the light environment area model constructed in Step 1, estimate the illuminance of the reading area. The relationship between brightness and contrast in the projection viewing area, and the estimated illuminance of the background area. The estimated illuminance along the line of sight path corresponds to the illuminance range, illuminance uniformity, blue light hazard, and flicker requirements in national and industry standards, forming multiple dimensionless risk factors. These factors are accumulated over a time window to obtain a single eye risk index. This will provide a reference for further determining safety limits and lighting environment targets.

[0079] In a child's desk scenario, the estimated illuminance of the reading area at the same moment. Projection viewing area contrast, background area illuminance, and estimated illuminance along the viewing path. It is necessary to compare the current lighting environment with the limits set by the state or industry for reading and writing lighting and myopia prevention in order to determine whether the current lighting environment deviates from the safe range.

[0080] If we rely solely on absolute illuminance or luminance values ​​for manual judgment, it is not only difficult to standardize the lighting parameters of different homes and classrooms, but also difficult to provide simple and feasible decision-making logic within the control chip. Therefore, it is necessary to convert these physical quantities into dimensionless risk factors ranging from 0 to 1. The closer the risk factor is to one, the more serious the deviation from the standard. This facilitates the superposition of these factors in the control logic and also facilitates the accumulation over time.

[0081] First, read the preset standard limit information in the memory, and load the standard parameters such as the lower limit of reading illuminance, the upper limit of reading illuminance, the lower limit of illuminance uniformity, the upper limit of permissible blue light hazard index, and the upper limit of permissible flicker index into the running variables.

[0082] These parameters are configured according to specific standard clauses, for example, mapping the lower limit of reading illuminance to a variable used to correlate with the estimated illuminance value of the reading area. In comparison, the suggested upper limit for line-of-sight illuminance is mapped to another variable and used to compare it with the estimated line-of-sight illuminance. Comparison. In each control cycle, the control chip compares the current regional physical quantities one by one with the corresponding limits, and constructs risk factors based on the degree of deviation.

[0083] As an example, the estimated illuminance in the reading area Slightly below the preset lower limit of reading illuminance, while the estimated illuminance along the line of sight path... The illuminance level is significantly higher than the recommended upper limit for line-of-sight illumination. At this point, the control chip calculates the reading illuminance risk factor. and glare risk factors :for The study focuses on the impact of a darker reading area on reading and writing tasks; for This primarily reflects the degree of glare that may occur when the eyes are directly facing a bright source. The control chip also constructs a contrast risk factor based on the brightness distribution and contrast of the projection area. And based on the lighting fixture driving method and dimming duty cycle, a flicker risk factor is constructed. Thus, at the end of the control period, a set of immediate risk factors will be formed within the system. , , , Each of them has a clear physical meaning.

[0084] Reading illumination risk factor For example, the following piecewise linear normalization function can be performed.

[0085]

[0086] in, The illuminance of the reading area during the current control cycle. and These are the lower and upper limits of reading illuminance set according to standards. When the illuminance is within the specified range... When the illuminance is too dim or too bright, it is mapped to the scale of the relative deviation. The interval is defined and truncated at point 1.

[0087] Furthermore, standard limits are read from memory, along with illuminance estimates for the reading area. Construct a reading illuminance risk factor based on the degree of deviation from the lower and upper limits of reading illuminance. A contrast risk factor is constructed based on the degree to which the contrast of the projection viewing area deviates from the preset lower limit of contrast. A flicker risk factor is constructed based on the dimming duty cycle and frequency of the lamp drive waveform. For the estimated illuminance value along the line of sight Deviation from the recommended upper limit of line-of-sight illuminance constitutes a glare risk factor. and will to Keep it between 0 and 1.

[0088] When in use, the structure ensures the feasibility and maintainability of eye risk assessment; at the same time, by constructing risk factors item by item, certain risk items can be added or removed without changing the framework, which has good scalability.

[0089] Relying solely on immediate risk factors within a single control period to It is difficult to accurately reflect the cumulative eye strain a child experiences when continuously exposed to a certain light environment for several minutes or even half an hour. The human eye's adaptation to and fatigue process in response to the light environment has obvious time characteristics. Short periods of brightness or darkness may not necessarily cause obvious discomfort, but prolonged deviations can pose risks.

[0090] Therefore, risk factors should be accumulated smoothly over time. In addition to considering the current moment, the historical state over a period of time should also be taken into account when using eye risk assessment.

[0091] Therefore, each risk factor should be... ( (This refers to the risk factor number) Define a time window length and decay parameter, and perform a weighted average of the instantaneous risk factors within each control period. High-risk states that appear earlier within the same time window will gradually weaken over time, while newly emerging high-risk states have a greater impact on the current assessment. In other words, the overall assessment retains both historical information and sensitivity to new changes. In terms of control implementation, the control chip only needs to perform a linear combination of the cumulative risk factors from the previous period and the instantaneous risk factors of the current period each cycle, without needing to store excessively long historical sequences, which can be implemented on some resource-constrained hardware platforms.

[0092] No. The cumulative time-based relationships of individual risk factors can be used as follows:

[0093]

[0094] Among them, the time-cumulative risk factor : in the The result obtained at the end of the control cycle is the first The time-weighted result of each risk factor, with values ​​between 0 and 1; the cumulative risk factor from the previous period. : for the first The cumulative time value of the same risk factor at the end of each control period, with a value between 0 and 1;

[0095] Smoothing parameters : No. The time decay coefficient of each risk factor, taking a value between 0 and 1, when... When the value is relatively large, the historical state has a stronger influence. When the risk factor is relatively small, the current real-time risk factor is relatively small. Strong impact; immediate risk factors : in the The first control cycle is calculated based on regional physical quantities and standard limits. One risk factor, with a value between 0 and 1; time parameter : No. The end time of each control cycle is a time series with values ​​that are monotonically increasing.

[0096] In one implementation, when a child continuously does homework as the light gradually dims in the evening, the estimated illuminance value of the reading area is... The reading illuminance was slightly below the lower limit for multiple cycles, and the control chip obtained a reading illuminance risk factor slightly above zero in each cycle. The cumulative risk factor of reading illuminance time is continuously updated using the above formula. As time goes by, The gradual increase reflects the cumulative risk caused by prolonged periods of darkness. Meanwhile, if the flicker risk factor... The cumulative risk factor has remained consistently low. It then remains close to zero.

[0097] Among them, each risk factor is given Set smoothing parameters Each control cycle is based on real-time risk factors. and the cumulative risk factor of the previous week Calculate the current cycle cumulative risk factor using the linear combination formula. , Stored in memory;

[0098] When using it, historical risk information within a time window can be compressed to avoid storing large amounts of historical data, and different smoothing parameters can be set according to different risk factors. If the blue light risk setting is too high Emphasizing long-term exposure and setting a moderate glare risk level. Using eye risk assessment is more consistent with actual eye use behavior characteristics in the time dimension.

[0099] The cumulative results of each risk factor over time are obtained. Afterwards, it is still necessary to combine these risk metrics reflecting different dimensions into a comprehensive eye use risk index. The index must include multiple factors such as reading illuminance, projection contrast, blue light content, flicker characteristics, and glare, and it must also be easy to compare with the safety upper limit in subsequent steps.

[0100] If the control chip directly imposes restrictions on multiple risk factors separately, the control logic becomes complex, difficult to maintain with limited resources, and also unhelpful in explaining the current eye usage status to the user. Therefore, an eye usage risk index is introduced. This single scalar, through weighted aggregation, reflects the relative importance of different risk factors.

[0101] Therefore, weighting coefficients are pre-set for each risk factor. These weights refer to the standard terms' emphasis on various risks, and can also be adjusted according to the child's age and user preferences. For example, for lower elementary school users, the weights of reading illumination-related risks and glare-related risks along the viewing path can be increased; for older elementary school users who use computers for extended periods, the weights of flicker-related risks and projection contrast-related risks can be appropriately increased. At the end of each control cycle, the control chip reads the cumulative risk factors for that cycle. And the corresponding weighting coefficients, combined to form an eye use risk index. .

[0102] The eye use risk index can be weighted and aggregated as follows:

[0103]

[0104] Among them, the eye use risk index : No. A comprehensive eye use risk index calculated after the weekend, ranging from 0 to 1; weighting coefficient. : Cumulative risk factor of reading illumination time The aggregate weights are between 0 and 1; the weight coefficients are... Projection contrast ratio cumulative risk factor over time The weight of the cumulative risk factor of flicker time is between 0 and 1; the weight coefficient is also between 0 and 1. Glare duration cumulative risk factor The weights are between 0 and 1; all weight coefficients satisfy... That is, maintaining the eye risk index It is between 0 and 1 and has physical meaning.

[0105] Preset or change the weight coefficients of each factor to to The cumulative risk factor is invoked in each control cycle. to The eye use risk index is calculated using the weighted formula above. And put it into the register or memory of the control chip for use in step three or step four.

[0106] The proportion is adjusted according to different risk dimensions within the user group or usage scenario, for the same eye use risk index. It meets both standard-level safety requirements and individual needs, and the above methods are easier to understand in real home and school environments.

[0107] Eye use risk index If the calculations are only used internally for comparison without explanation, parents and teachers will find it difficult to understand the current risk level of the light environment, which will also hinder subsequent steps. The value should be subject to clear safety constraints. An interpretation mechanism needs to be reserved to account for the eye-use risk index. Corresponding to a simple and clear risk level, and providing an interface in the control logic for subsequent brightness budgeting and dynamic adjustment, Changes can be naturally passed on to subsequent decision-making steps.

[0108] Therefore, for the eye use risk index Define low-risk, medium-risk, and high-risk zones, and associate them with corresponding control strategy indicators or warning levels. (Regarding the eye use risk index...) If the risk level is low, subsequent steps will retain a more lenient upper limit on luminous flux. If the risk level is in the medium-risk range, subsequent steps should slightly tighten the upper limit of luminous flux when budgeting for brightness, while reducing the brightness of non-critical areas; when If the area is in a high-risk zone or exceeds the safety limit, the next steps should promptly select a more conservative brightness allocation strategy and trigger a rapid brightness reduction strategy during dynamic adjustment.

[0109] At the same time, the system can also display the current eye risk index value. The information on the risk zone is converted into simple risk level information and displayed to parents or teachers via a screen or mobile application to remind them of their eye use status.

[0110] Therefore, for the eye use risk index Multiple risk level thresholds are pre-set, each range is linked to a subsequent control strategy identifier, and at the end of each control cycle, the risk level is adjusted based on the current risk level. The system updates the risk level and policy identifier, stores this information in a predefined register, and provides an interface to the outside world.

[0111] When used, it not only numerically completes the eye risk index The calculation also prepares directly referable safety state information for subsequent steps in terms of control semantics, enabling the entire method to naturally import the risk assessment results into the brightness budget and dynamic adjustment process during engineering implementation.

[0112] Step 3: In the eye use risk index Given the known optical parameters of each region, the current usage is divided into several predefined tasks through task scenario identification. For each task, a safety constraint boundary and a light environment target vector are set in combination with the risk level, so that the above parameters can be introduced in step four when performing brightness budget and region allocation.

[0113] Children's specific behaviors at their desks are not constant; they may frequently switch between multiple tasks such as reading paper books, writing paper books, explaining things on a desktop projector, watching short animations, and typing on a keyboard within the same time period.

[0114] Different tasks affect the illuminance of the reading area. Contrast with projection viewing area Different requirements apply to the background area illumination. and line-of-sight illuminance Their tolerance levels also differ. If we don't differentiate between task scenarios and only rely on the eye-use risk index... Setting uniform constraints can easily lead to situations where the lighting is too high when reading while watching videos, or the projected viewing area is too conspicuous when doing homework.

[0115] Therefore, after each control cycle, the current task scenario can be determined by the camera image and application running status, providing a basis for subsequent differentiated settings of safety constraints and lighting environment targets. The spatial positions of the reading plane and projection plane in the lighting environment area model established in step one are read, and their textures are extracted from the camera image. For example, whether there are text lines and paper boundaries in the reading plane, and whether there are high-contrast patterns or subtitles in the projection plane, are determined in conjunction with the application running status to determine whether the current interface is for functions such as projection content, homework grading, or exercise push.

[0116] When the text texture is clear on the reading surface, the child's head is facing the reading surface, and the brightness on the projection viewing surface is low, the current scene is identified as a paper-based reading scene; when there is writing action on the reading surface, and static questions or solution steps appear on the projection viewing surface, it is identified as a mixed paper-based and projection viewing learning scene; when the child's head is facing the projection viewing surface for a long time, the brightness and image of the projection viewing area change frequently, and there is almost no writing action on the reading surface, it is identified as a short-term projection interaction or video viewing scene; when the camera detects keyboard and mouse activity and there is no paper on the reading surface, it is identified as a desktop office scene.

[0117] A two-layer structure is used for scene classification: the first layer is rule-based judgment, which quickly eliminates impossible scenarios by directly using explicit conditions such as whether the reading area has paper outlines, whether the projection viewing area is open, and whether the application is in a playback interface; the second layer uses a combination of features of paper texture in the image, projection content type, and child's head posture, and performs detailed differentiation through an offline-trained classification model, ultimately outputting task scene labels. The features are mapped to a finite number of scene identifiers through offline training;

[0118] In one embodiment, the child first opens the workbook at the table, the projector lamp projects static questions, and the control program then changes the scene accordingly. Set up as a mixed learning scenario combining paper and projection; when the child temporarily stops writing and looks up to watch the animated explanation, the projection area shows continuous image changes and the head orientation changes, and the control program gradually adjusts the orientation over several control cycles. Switch to a short-term projection interactive scene.

[0119] When in use, complex usage behaviors are abstracted into a finite number of task scenario identifiers. This allows for differentiated configuration of subsequent safety constraints and lighting environment targets for specific task types, rather than using a one-size-fits-all approach to lighting and projection parameters. Scene classification relies on the region model and camera images established in step one, eliminating the need for additional dedicated sensors to distinguish the main task types. This helps reduce hardware costs and improve the feasibility of the method.

[0120] Even within the same task scenario, the eye risk index during a continuous control period... Changes in the format will also lead to different requirements for security constraints. In the context of reading the same sheet of paper, if... A smaller illuminance can reduce the reading area's illumination. Maintain at a certain height, and when Once the safe limit is reached, the available luminous flux should be gradually increased to reduce the burden on the eyes from prolonged use.

[0121] Therefore, task scenario identification is required. Once determined, based on the current eye use risk index Determine the safety level within the scenario to differentiate between different control strategies, such as lenient safety level, intermediate safety level, and strict safety level.

[0122] For each task scenario, two threshold values ​​for the eye use risk index are pre-defined, such as a low-risk threshold and a high-risk threshold for a certain scenario. The eye use risk index is then read within the current control period. Then, it is compared with the boundary value in the corresponding scenario. If If the risk level is below the low-risk threshold, it is classified as a lenient safety level; if it is between the low-risk and high-risk thresholds, it is classified as a medium safety level; if it is above the high-risk threshold, it is classified as a strict safety level.

[0123] The obtained safety gear indicator With the task scenario This information serves as an index for subsequent safety constraints and target parameter settings. (Task scenario identifier) and safety gear indicator This can be represented using enumeration encoding, with the control program maintaining a configuration table. and The combinations list the safety constraint parameters and the target parameters for the lighting environment. In a paper-reading scenario, the lenient safety setting indicates a high target reading illuminance value and a wider upper limit for the eye risk index, while the strict safety setting indicates a lower upper limit for the eye risk index and a smaller upper limit for the illuminance along the line of sight.

[0124] Identify the task scenario and eye use risk index Combined into a safety gear indicator Subsequent safety constraints and lighting environment targets no longer depend on scene category and can be changed at any time according to the risk level; the setting of preset boundary values ​​and configuration tables can be achieved simply by looking up the table to obtain the corresponding parameters, without the need for a solver.

[0125] Step four requires adhering to a set of explicit constraints when performing brightness budgeting and zone allocation. These constraints must reflect the eye use risk index. The upper limit that cannot be exceeded must also reflect the illuminance of the reading area. Projection viewing area contrast and background area illuminance and line-of-sight illuminance The upper and lower bound requirements.

[0126] If security constraints exist only in scattered numerical form, subsequent brightness budgeting is difficult to execute in a uniform manner. Therefore, in task scene identification... and safety gear indicator Once determined, the upper or lower limits of safety-related physical quantities are organized into a safety constraint vector. This allows step four to directly use this vector for constraint judgment.

[0127] Therefore, through and Find the corresponding security parameters in the configuration table, such as the upper limit of the eye risk index. Lower limit of illuminance in reading area Lower limit of contrast in projection viewing area Background area illuminance limit Upper limit of illuminance along the line of sight The above parameters can be pre-set during the product design phase based on standard requirements and trial survey results, or they can be implemented through software upgrades during the product usage phase. After retrieving the above parameters, the control program assembles them into a safety constraint vector in a prescribed order. , can be represented as:

[0128]

[0129] Where: safety constraint vector This is a five-dimensional column vector used to centrally represent the allowable range of each major physical quantity within the current control cycle; the upper limit of the eye risk index. This represents the maximum permissible eye risk index under the current task scenario and safety level, ranging from 0 to 1.

[0130] Lower limit of illuminance in reading area : Illuminance of the reading area The minimum allowable value in this scenario, a positive real number; lower limit of projection view area contrast. : for the contrast of the projection viewing area The minimum allowed value in this scenario is between 0 and 1; the upper limit of background area illuminance. : Background area illuminance The maximum allowed value in this scenario is a non-negative real number; the upper limit of illuminance along the line of sight. Illuminance along the line of sight The maximum value allowed in this scenario is a non-negative real number.

[0131] When using this method, the dispersed set of safety parameters is transformed into a vector form, enabling unified constraints and judgments for subsequent brightness budgeting and region allocation; task scene identifiers are used. Safety gear indicator Dual indexing allows for the matching of safety constraint parameters under different task scenarios and risk levels, facilitating product adaptation between the product and the user. In addition to the safety constraints that cannot be exceeded, brightness budgets and area allocations must also meet lighting environment targets to ensure that the output of both the lighting and projection light sources is suitable for the current task.

[0132] For example, in a paper-based reading scenario, the desired illuminance in the reading area While maintaining a suitable brightness in the projection viewing area close to a certain target value, a higher contrast ratio in the projection viewing area is desirable in short-duration interactive projection scenarios. Higher illuminance in the reading area Slightly reduced. Without pre-setting the light environment target in step three, it's difficult to construct the cost function in step four to incorporate the deviations of different physical quantities into a unified evaluation. Therefore, in the safety constraint vector... Once determined, a target vector for the lighting environment is set for each task scenario and safety setting combination. and target weight vector This provides a parameter basis for the subsequent construction of the cost function.

[0133] according to and Find the set of target parameters for the lighting environment, including the target illuminance value for the reading area. Target value of contrast in the projection viewing area Background area illuminance target value and line-of-sight path illuminance target value Simultaneously, find the target weight coefficients used to measure the importance of deviations from each target. , , and .

[0134] These target values ​​are typically located within the upper and lower bounds of the corresponding safety constraints, while the weighting coefficients are set according to the importance of different regions in the task scenario. The target vector for the lighting environment and the target weight vector are represented as follows:

[0135]

[0136] Where: Light environment target vector This is a four-dimensional column vector used to centrally represent the physical quantities of the ideal state of each region in the current control cycle; the target illuminance value of the reading region. The desired illuminance level for the reading area, a positive real number; the target contrast value for the projection viewing area. : This represents the desired projection view area contrast ratio for the current task scenario, ranging from 0 to 1;

[0137] Background area illuminance target value is the desired illuminance for the background area, a non-negative real number; is the target illuminance value for the line-of-sight path. Let be the expected illuminance along the line of sight, a non-negative real number.

[0138]

[0139] Where: target weight vector It is a four-dimensional column vector used to represent the weights of the impact of each target physical quantity deviating from the target on the overall cost function;

[0140] Reading target weight : The weight of the illuminance deviation in the reading area in the cost function, a non-negative real number; the weight of the projected target. : Weight of contrast deviation in the projected viewing area in the cost function; background target weight : The weight of background area illumination deviation in the cost function; the target weight of the line-of-sight path. : represents the weight of the line-of-sight path illumination deviation in the cost function.

[0141] In one embodiment, when For paper reading scenarios and When the strict safety setting is enabled, the control program will set the target illuminance value for the reading area. Set within a relatively conservative range and assign weights to the reading target. Assign a larger value to the target contrast value of the projection viewing area. Set at a lower level and assign a smaller projected target weight. At the same time, the target value of background illuminance and line-of-sight path illuminance target value Set values ​​and corresponding weights that help reduce glare.

[0142] Similarly, when As a short-term projection interactive scenario and When the safety setting is relaxed, the target contrast value of the projection viewing area of ​​the control program is... and their weights It will increase the target illuminance value in the reading area. and their weights It will decrease accordingly.

[0143] Using light environment target vector and target weight vector At the same time, it provides specific numerical descriptions of the ideal light environment under different task scenarios and safety levels, thereby ensuring that the light approaches in one direction within the constraints, rather than merely meeting the most basic safety range.

[0144] Step 4: Based on the safety constraint vector and light environment target output in Step 3, distribute the limited luminous flux between the lighting channel and the projection channel and among the various areas within the lighting channel, so that the predicted illuminance of the reading area and the contrast of the projection viewing area are as close as possible to the target value, while limiting the risk of eye strain to no more than the allowable upper limit, and controlling the change in luminous flux and power consumption.

[0145] Eye Risk Index Step two has already taken into account reading illuminance, blue light content, flicker characteristics, and glare, and step three has given the upper limit of permissible eye risk. .

[0146] If the relationship between reading illuminance and projection contrast is not considered during brightness allocation, and the goal of achieving reading illuminance and projection contrast close to the target values ​​is pursued blindly, it is possible to maintain an excessively high level of brightness even under high-risk conditions. To avoid this situation, at the end of each control cycle, the brightness level is adjusted according to the current task scenario. Reference values ​​for baseline luminous flux and eye risk index and the upper limit of allowable eye use risk The relative relationship gives the maximum total luminous flux allowed in the current period. Based on this, the luminous flux budget boundaries of the lighting source and the projection source are determined, which limits the search range for subsequent cost function solutions.

[0147] Read the baseline total luminous flux reference value for the corresponding task scene from the scene parameter table. This reference value can be understood as the total luminous flux required to meet the lighting environment target of a scene when the risk of eye strain is low and the ambient light is average.

[0148] Furthermore, according to the current eye use risk index With the maximum allowed The difference between the two values ​​is used to construct a risk modulation factor, so that the closer the risk is to the upper limit, the lower the allowable total luminous flux; conversely, when the risk is significantly lower than the upper limit, the allowable total luminous flux can be close to the reference value. The specific form of the risk modulation factor can be determined during the design phase based on standards and experience, and different modulation sensitivities can be adopted for different mission scenarios.

[0149] The maximum total luminous flux can be given by the following relationship:

[0150]

[0151] In the formula, the maximum total luminous flux is... During the control cycle The upper limit of luminous flux that can be used for the sum of lighting and projection light sources, and is a non-negative real number; a reference value for total luminous flux. The total luminous flux reference value recommended for use in corresponding task scenarios with low eye risk is a positive real number, which can be obtained through illuminance and contrast calibration.

[0152] Scene risk modulation coefficient A non-negative number less than 1, used to adjust the eye-use risk index in the current task scenario. Different modulation coefficients can be used for different task scenarios to compress the upper limit of total optical flux;

[0153] Eye Risk Index This refers to the comprehensive eye risk index calculated in step two, with a value between 0 and 1. Indicates the first The eye use risk index for each control period; if there is no time index... All are considered The abbreviation; to ensure that the factor inside the parentheses is not negative, it is necessary to select the appropriate factor during the design. The range of scenario risk modulation coefficients.

[0154] To achieve maximum total luminous flux Then, the control chip identifies the task scenario. Obtain the budget ratio range for the lighting source and the projection source. For example, in a paper reading scenario, reserve a higher budget range for the lighting source and a smaller budget range for the projection source. For short-term projection scenarios, reserve a larger upper limit for the luminous flux of the projection source and some leeway for the lighting source. By setting the lower and upper limits of the luminous flux ratio for the lighting channel in the scene parameter table, the budget ranges for the lighting source and the projection source are obtained by multiplying the maximum total luminous flux by the ratio range, which represents the luminous flux search range for the two channels.

[0155] When using it, the overall eye risk index will be considered. With task scene identifier By introducing an upper limit calculation for the luminous flux budget, brightness allocation is constrained from the outset by the overall risk level. This is achieved through the risk modulation coefficient. The settings allow for controllable impact of eye-related risks on total luminous flux in different scenarios, with greater sensitivity for paper reading scenarios and slightly less sensitivity for short-term projection scenarios. The budget interval approach limits the search space for subsequent cost function solutions, which helps to obtain luminous flux combinations using finite-precision numerical methods in the control chip.

[0156] Lighting sources typically illuminate different areas through multiple light subarrays, with the light subarray facing the reading area providing the highest possible illuminance to that area. The impact is greater; the light sub-array facing the background area has a greater impact on background illuminance and glare.

[0157] If the lighting source is considered as a single luminous flux output without considering its internal structure, it is difficult to prioritize the illuminance of the reading area by changing the internal light distribution structure when the total luminous flux is fixed. Therefore, a reading sub-array luminous flux is introduced within the lighting source. Light flux of background subarray The two degrees of freedom allow for a more nuanced trade-off between the illuminance in the reading area and the illuminance in the background area when solving the subsequent cost function.

[0158] In this process, based on the positions of the reading plane and the background area in the desktop coordinate system determined in step one, the LED subarray of the lighting source is divided into a reading subarray and a background subarray. The contribution coefficient of each subarray to the illuminance of the reading area and the background area is recorded. These contribution coefficients are obtained during the factory calibration phase by lighting up each subarray individually and measuring the illuminance of the reading area and the background area. In the current control cycle, when the target luminous flux of the lighting source is not yet determined, the total luminous flux variable of the lighting source is decomposed into the luminous flux variable of the reading subarray. Light flux variable of background subarray The sum of the two constitutes the luminous flux variable of the lighting source. .

[0159] The light flux of the subarray and the light flux of the background subarray satisfy the following relationship:

[0160]

[0161] In the formula, the optical flux of the reading subarray is... Control cycle time The luminous flux variable assigned to the lighting subarray of the reading area is a non-negative real number;

[0162] Background subarray luminous flux Control cycle time The luminous flux variable assigned to the background area lighting subarray is a non-negative real number; the luminous flux of the lighting source... The lighting source during the control cycle The total luminous flux variable is a non-negative real number; here it represents the distribution of luminous flux between the reading subarray and the background subarray given a total illumination luminous flux.

[0163] In use, two adjustable degrees of freedom have been added within the lighting source, allowing the brightness budget to not only allocate the total luminous flux between the lighting channel and the projection channel, but also adjust the light distribution relationship between the reading area and the background area within the lighting channel. (Reading area illuminance) It can be improved without significantly increasing background glare; when the eye risk index is high, the light flux of the background subarray can be reduced first while keeping the illuminance of the reading area close to the minimum requirement, thereby reducing the overall light load and leaving room for subsequent risk control.

[0164] Given a maximum total luminous flux Given the freedom of light distribution within the lighting channel, the luminous flux of the lighting source Reading subarray optical flux Background subarray luminous flux Luminous flux of the projection light source The values ​​of will jointly determine the illuminance of the predicted reading area and the contrast of the predicted projection viewing area.

[0165] To select a suitable combination of luminous fluxes within safety constraints, a unified evaluation metric is needed to express the impact of reading illuminance deviation, projection contrast deviation, luminous flux variation, and total luminous flux magnitude. Based on this, a comprehensive cost function is constructed. By applying different weights and nonlinear exponents to the reading target deviation, projection target deviation, absolute magnitude of luminous flux, and luminous flux variation amplitude, the subsequent solution tends to select a luminous flux combination that satisfies the objective without excessively increasing the light load and brightness fluctuation.

[0166] At the end of the current control cycle, the control chip constructs a predicted reading area illuminance function and a predicted projection viewing area contrast function based on the area model from step one and the calibration results, thereby obtaining the predicted reading area illuminance value for the next control cycle under a given luminous flux combination. and predicted contrast value of the projection viewing area The above prediction function can be obtained by interpolation based on the illuminance and contrast measured during the factory calibration process.

[0167] The control chip will predict the illuminance of the reading area and the target illuminance value of the reading area. Deviation, predicted projection viewing area contrast and contrast ratio and target contrast value The deviation, the total luminous flux, and the change in luminous flux of the lighting source relative to the luminous flux of the previous period are combined with different weights and nonlinear exponents to form a comprehensive cost function.

[0168] The comprehensive cost function can be constructed using the following formula:

[0169]

[0170]

[0171] In the formula, the comprehensive cost function Control cycle time The evaluation value for candidate luminous flux combinations is a non-negative real number. A larger value indicates a less ideal performance in terms of reading illuminance deviation, projection contrast deviation, total luminous flux magnitude, and luminous flux variation. (Reading weight coefficient) : A non-negative real number used to adjust the influence of the reading area illuminance deviation term in the cost function; Predicting reading area illuminance: at time [time] in the control cycle. The predicted value of the illuminance in the reading area for the next control cycle is obtained by mapping the luminous flux combination of the lighting source and the projection source to the area model, and is a real number greater than zero.

[0172] Calibration phase: Conduct multiple sets of experiments on the product in the factory, enumerating several sets. Combine and measure the illuminance of the corresponding reading area. and projection viewing area contrast Store these points in the calibration table;

[0173] The contrast ratio is achieved using a three-dimensional interpolation function. Approximation, using two-dimensional or three-dimensional interpolation functions for contrast. For approximation, commonly used multilinear interpolation or piecewise polynomial interpolation is sufficient.

[0174] Operational phase: Step four generates candidate luminous flux combinations At that time, the control program calls the above interpolation function to obtain:

[0175] ;

[0176]

[0177] By using a calibration table and interpolation function, the prediction function is explicitly defined for a specific engineering operation.

[0178] In one implementation, the illuminance of the reading area is predicted. Contrast with predicted projection viewing area A linear regression approach can be used. Let the current luminous flux of the illumination subarray be denoted as . and The luminous flux of the projection light source is Then we have:

[0179]

[0180]

[0181] Among them, coefficient and During the factory calibration phase, the coefficients were obtained through least squares fitting: multiple known luminous flux combinations were selected in a dark room, and the illuminance of the corresponding reading area and the contrast of the projected viewing area were measured. After establishing a sample dataset, linear regression was performed to solve for the above coefficients. Those skilled in the art can also use higher-order polynomials or interpolation functions to replace this linear relationship.

[0182] Reading area illuminance target value The target illuminance for the current reading area, determined in step three, is a real number greater than zero; the reading deviation index... : A real number greater than 1; Projection weighting coefficient : A non-negative real number used to adjust the influence intensity of the contrast deviation term in the projection viewing area; used to predict the contrast of the projection viewing area. During the control cycle The predicted value for the projection viewing area contrast in the next control cycle is obtained by mapping the luminous flux of the projection light source to the background illuminance, and the value ranges from 0 to 1; the target value for the projection viewing area contrast... The target contrast of the current periodic projection viewing area, determined in step three, has a value between 0 and 1.

[0183] Projection deviation index : A real number greater than 1; luminous flux weighting coefficient : A non-negative real number used to penalize excessive total luminous flux; luminous flux of a lighting source. Luminous flux of the projection light source : The candidate illumination and projection luminous flux for the current control cycle, a non-negative real number; the total luminous flux index. : A real number greater than 1; luminous flux variation weighting coefficient : A non-negative real number used to limit the variation in luminous flux of a lighting source relative to the luminous flux of the previous cycle;

[0184] Luminous flux of the lighting source in the previous cycle : Luminous flux of the lighting source in the previous control cycle; Luminous flux change index It is a real number greater than 1.

[0185] In one implementation, for hybrid learning scenarios, the designers set a larger reading weight coefficient. With moderate projection weighting coefficient At the same time, set an appropriate luminous flux weighting coefficient. Weighting coefficient for changes in luminous flux Furthermore, the reading deviation index, projection visual deviation index, and luminous flux correlation index are all set to be greater than two. This ensures that when the illuminance deviation of the reading area and the contrast deviation of the projection visual deviation are small, the cost function is mainly determined by the magnitude and variation of the total luminous flux. However, when the illuminance deviation of the reading area or the contrast deviation of the projection visual deviation increases, the growth rate of the corresponding terms in the cost function accelerates significantly.

[0186] In practice, four factors—the target illuminance of the reading area, the target contrast of the projected viewing area, the total luminous flux, and the change in luminous flux—are uniformly incorporated into a calculable cost function. This provides a quantitative basis for selecting luminous flux combinations within safety constraints, highlights the impact of reading illuminance and projection contrast deviation on the evaluation results, and prioritizes luminous flux combinations that align with these key objectives. While ensuring the objectives are met, it controls eye load and the rate of brightness change, resulting in a more reasonable trade-off between visual experience and risk control.

[0187] Comprehensive cost function The evaluation method for candidate luminous flux combinations has been given. However, if the luminous flux combination is selected directly based on cost without considering safety constraints, there may be luminous flux schemes where the illuminance in the reading area is lower than the minimum requirement or the contrast in the projection viewing area is lower than the minimum requirement.

[0188] Therefore, based on the constructed cost function, the safety constraint parameters obtained in step three are introduced to limit the solution to satisfying the upper limit of the allowable risk of eye strain. Minimum illuminance requirements for reading area Minimum contrast requirement for the projection viewing area Within the light flux combination space, and within this space, a cost function is selected that... The smaller values ​​of the luminous flux are combined to form the target luminous flux of the lighting source. Reading the target optical flux of the subarray Background subarray target light flux and the luminous flux of the projection light source target This generates a regional light distribution scheme.

[0189] The control chip describes the luminous flux combination problem as follows: Under constraints including budget intervals for the illumination and projection channels, maximum total luminous flux constraints, lower limit constraints for reading area illuminance, lower limit constraints for projection viewing area contrast, and upper limit constraints for allowable eye risk, find a set of luminous flux variables that make the combined cost function... As small as possible. The lower limit constraint on reading area illuminance can be achieved by predicting the reading area illuminance. Minimum illuminance requirements for reading area The comparison is used to represent the lower limit constraint of the projection viewing area contrast, which can be expressed by predicting the projection viewing area contrast. Minimum contrast requirement for the projection viewing area The comparison is used to represent this; the upper limit constraint on eye use risk can be determined by predicting that the eye use risk index in the next period will not exceed the upper limit. Given the conditions, this prediction can be simplified to constraints on the predicted values ​​of total luminous flux and line-of-sight path illuminance.

[0190] Furthermore, the control chip first determines the maximum total luminous flux. Record total luminous flux constraints:

[0191]

[0192] In the formula, the luminous flux of the lighting source is... Luminous flux of the projection light source For the current period, the candidate luminous flux variable is the maximum total luminous flux. This represents the upper limit of the luminous flux calculated above; this inequality gives the condition that the sum of the illumination and projection luminous flux does not exceed the maximum total luminous flux.

[0193] Under this constraint, the control chip incorporates the lighting channel budget interval constraint, the reading area illuminance lower limit constraint, and the projection viewing area contrast lower limit constraint into a finite-dimensional constraint space. Within this space, a pre-selected numerical method is used to find the constraint that minimizes the cost function. A relatively small luminous flux combination. To solve for the luminous flux combination, a sequential quadratic programming method or a simplified interior-point solver can be used. Alternatively, a strategy combining hierarchical grid search and local correction can be employed within the budget interval, allowing the solution process to be completed within the limited computing resources of the embedded control chip. In the obtained luminous flux combination, the luminous flux component of the illumination source is the target luminous flux of the illumination source. The light flux components of the reading subarray and the background subarray are respectively the target light flux of the reading subarray. Target light flux of background subarray The luminous flux component of the projection light source is the target luminous flux of the projection light source. .

[0194] In one implementation, children are solving math problems in a mixed learning environment, with the target illuminance value for the reading area being [not specified]. Too high, target contrast value for the projection viewing area Moderate, eye-use risk index Approaching a moderate level. The control chip calculates the maximum total luminous flux based on the aforementioned relationship. Set the budget range for the lighting channel to be slightly larger than that for the projection channel, and construct the comprehensive cost function. The system searches the candidate luminous flux set that satisfies the constraints of total luminous flux, lower limit of reading area illuminance, and lower limit of projection area contrast using a sequential quadratic programming method. This ensures that the predicted reading area illuminance and predicted projection area contrast are as close as possible to the target values, while suppressing abrupt changes in the luminous flux of the illumination source relative to the previous cycle.

[0195] The solution results show the target luminous flux of the illumination source. The allocation is relatively high, and the target optical flux of the reading subarray is high. Significantly higher than the target light flux of the background subarray Target luminous flux of the projection light source It was suppressed to a position that just barely met the lower limit of contrast.

[0196] During use, the illuminance of the reading area is kept as close as possible to the target value while meeting the minimum requirements, and the contrast of the projection viewing area is controlled to avoid being too high while meeting the sharpness requirements. The illuminance of the background area and the illuminance of the viewing path are suppressed by the allocation of luminous flux between the reading subarray and the background subarray. The amplitude of luminous flux variation is constrained by the variation term in the cost function, making the brightness change between continuous control cycles smoother.

[0197] Step 5: Implement the luminous flux target scheme output in Step 4 into an executable brightness change trajectory for each control cycle, and feed the execution results back to the eye risk control parameters and light environment target parameters to form a closed control relationship of target determination-execution and parameter update, so that the projector lamp continuously approaches the predetermined eye safety target and user experience target in multiple control cycles.

[0198] Step four provides the target luminous flux of the illumination source. Target luminous flux of the projection light source It can only reflect the expected amount in the light environment dimension of the current control cycle, but cannot directly determine the rate at which the actual brightness should change between adjacent control cycles.

[0199] If the brightness changes too quickly, it will affect the eye risk index. A lower level can feel abrupt to children. If the brightness reduction is not rapid enough when approaching the allowable upper limit, it will hinder risk control. Therefore, it is necessary to adjust the brightness based on the safety level indicator obtained in step three. and the eye risk index obtained in step two Multiple brightness adjustment laws are set for the lighting channel and the projection channel respectively. The approach speed of the target luminous flux to the actual luminous flux is controlled by the change coefficient of different levels, so that comfort and safety are coordinated in the time dimension.

[0200] At the end of each control cycle, the current eye use risk index is read. Safety gear indicator This determines whether the current setting is relaxed, intermediate, or tight. In the relaxed setting, the lighting and projection channels are allowed to approach the target luminous flux at a relatively gentle pace to reduce children's perception of brightness changes. In the intermediate setting, the lighting channel should still prioritize comfort, but the projection channel should respond slightly faster to brightness reduction to discourage prolonged viewing of bright images. In the tight setting, when... Approaching or slightly above the allowed limit At this time, both the lighting channel and the projection channel need to converge quickly to a lower luminous flux state, prioritizing the reduction of brightness near the line of sight path.

[0201] Therefore, during the factory configuration stage, lighting channel variation coefficients and projection channel variation coefficients are set separately for different levels, and... The index is selected dynamically.

[0202] The actual luminous flux of the lighting source and the actual luminous flux of the projection source are denoted as follows: and The control program updates the actual luminous flux for the next cycle in each control cycle according to the following recursive form:

[0203]

[0204]

[0205] Among them, the actual luminous flux of the lighting source : To control the timing of the cycle The luminous flux corresponding to the actual output of the lighting source driver circuit is a non-negative real number; the target luminous flux of the lighting source. The target luminous flux of the lighting source obtained in step four is a non-negative real number; the illumination variation coefficient. To match the safety gear indicator The corresponding lighting channel adjustment coefficient is between 0 and 1. When indicating a relaxed setting, this coefficient takes a smaller value to moderate the change in luminous flux. When indicating a compressed setting, this coefficient takes a larger value, causing the luminous flux to approach the target more quickly;

[0206] Actual luminous flux of projection light source : The luminous flux corresponding to the actual output of the projection light source driving circuit at the control cycle time, a non-negative real number; Target luminous flux of the projection light source. The target luminous flux of the projected light source obtained in step four is a non-negative real number; the projection apparent variation coefficient is... To match the safety gear indicator The corresponding projection channel adjustment coefficient takes a value between 0 and 1; time parameter : for the first The end time of each control cycle is a time series with values ​​that are monotonically increasing.

[0207] When in use, the static luminous flux target is linked to the eye risk level, so that the actual output of the lighting and projection channels exhibits a graded adjustment behavior over time, with slow changes during relaxed periods and rapid decreases during stressed periods. Even if the luminous flux target given in step four changes significantly, the lighting and projection channels can distribute the brightness changes across multiple control cycles by adjusting the change coefficient, reducing the flickering sensation perceived by children.

[0208] Only the actual luminous flux of the lighting source Compared with the actual luminous flux of the projection light source Channel-level adjustments alone are insufficient to guarantee that the brightness variations within the reading and background areas conform to the target luminous flux of the reading subarray given in step four. Target light flux of background subarray The intended light distribution.

[0209] In order to retain the decision to prioritize the reading area and compress the background area in step four at the execution level, it is necessary to further refine the brightness control sequence of each light subarray within the illumination channel, so that the current of the reading subarray and the current of the background subarray change synchronously according to the ratio of the luminous flux of the subarray. Within the projection channel, it is also necessary to accurately map the actual luminous flux of the projection light source to the brightness and contrast of the projection viewing plane.

[0210] The control program obtains the actual luminous flux of the lighting source. Meanwhile, based on the ratio of the target luminous flux of the reading subarray to the target luminous flux of the background subarray determined in step four, the actual luminous flux of the illumination channel is divided into the actual luminous flux of the reading subarray and the actual luminous flux of the background subarray.

[0211] Based on the subarray luminous flux-drive current-duty cycle mapping obtained from factory calibration, these two luminous fluxes are quantized into corresponding drive current setpoints and pulse width modulation duty cycle sequences, and then sent to specific drive branches, causing the light subarray above the reading area and the light subarray in the background area to change with different amplitudes. In the projection channel, the control program maps the luminous flux to the average brightness of the projection viewing area based on the actual luminous flux of the projection light source and the area model from step one. Then, it adjusts the output level of the projection chip in conjunction with the grayscale distribution of the projected content, so that the contrast of the projection viewing area follows the result obtained in the previous sub-step. change.

[0212] In use, the lighting channel completes a refined process from channel-level eye risk control to area-level brightness execution. This ensures that the brightness changes of the reading area and the background area are not only determined by changes in channel-level luminous flux, but also that the illuminance of the reading area can maintain priority in multi-cycle adjustments, while the brightness of the background area can be flexibly compressed according to eye risk and scene requirements, thereby improving the clarity of paper reading and the comfort of the surrounding environment.

[0213] Maximum permissible risk for eye use The target lighting environment parameters established in step three are designed based on standards and experience during the design process. However, in actual use, the natural light in a home or classroom, the desktop lighting, and children's subjective sensitivity to light are all different. If these parameters are always fixed... When used with target parameters, some users may find the light too dim even when the safety margin is too large, or they may manually reduce the brightness when they are near the critical risk.

[0214] To ensure the system adapts to different usage environments while complying with regulatory requirements, at the end of each control cycle, the eye risk index is used as a reference. Long-term changes, the direction and frequency of manual adjustment operations, and the upper limit of permissible eye-use risks. It slowly self-adjusts with scenario-level parameters so that subsequent control cycles can use risk thresholds that are more in line with current family or classroom habits under the same task scenario.

[0215] For each task scenario, a reference risk level index and an offset index related to manual intervention are maintained. The reference risk level describes the average eye risk level actually experienced by children in that scenario over a past period, while the offset index describes the user's tendency to actively reduce brightness. At the end of each control cycle, the control program updates the current eye risk index. The reference risk level is written in a time-weighted manner. At the same time, it checks whether the user reduces the brightness by pressing a button or using a mobile device during the current period. If there are multiple consecutive brightness reduction operations, a manual intervention offset indicator is added.

[0216] Furthermore, based on the combination of the reference risk level and the manual intervention deviation indicator, the upper limit of the allowable eye use risk for the next period will be adjusted appropriately. Under the condition of ensuring that the risk limit does not fall below the preset absolute safety lower limit and does not exceed the standard upper limit, the risk limit is gradually brought closer to the actual usage preferences of families or classrooms.

[0217] The following formula can be used to describe the adjustment of the upper limit of allowable eye use risk between consecutive control periods:

[0218]

[0219] In the formula, the upper limit of the allowable risk of eye use is... Control cycle time The upper limit parameter for eye use risk used is between 0 and 1, and is subject to both the absolute safety lower limit and the standard upper limit.

[0220] Adjust step size coefficient : A non-negative real number whose value is much less than 1, used to control the adjustment range of the upper limit of allowable eye use risk in each control period;

[0221] Manual intervention intensity index This is a dimensionless, non-negative real number. Its value is determined based on the number and magnitude of times the user actively reduces the brightness within the current control cycle. When the user frequently and actively reduces the brightness, this indicator will have a larger value. relatively There is a clear downward trend; when there has been no manual dimming for an extended period, this indicator approaches 0, making... Basically unchanged; Calculated based on the number and magnitude of manual dimming by users within the current period, it is a dimensionless indicator. A typical implementation: For example, the sum of the number of times the dimming button is triggered within the current cycle and the decrease in duty cycle each time can be weighted and then compressed using simple normalization. Range; this operation is a simple addition and scaling operation.

[0222] In one implementation, a child manually reduced the brightness of the light multiple times within a month during paper-reading scenarios using buttons on the device. The control program recorded each manual dimming operation, accumulating them over multiple control cycles to form a high level of manual intervention. Therefore, under the aforementioned recursive relationship, the upper limit of the permissible risk to eyesight in paper-based reading scenarios is... As the brightness gradually decreases, the maximum total luminous flux calculated in step four of the subsequent control cycle also decreases, allowing the system to automatically adapt to the family's preference for lower brightness. If no manual brightness reduction is performed for an extended period in another scenario, the corresponding manual intervention intensity index remains close to zero, and the upper limit of eye risk in that scenario remains stable, closer to the standard value given in the design phase.

[0223] During use, without compromising myopia prevention and lighting safety, user-defined risk parameters can be implemented. The projector lamp will gradually establish a corresponding local user eye risk ceiling under different usage scenarios. Technical benefits: On one hand, the system can automatically identify scenarios where users prefer bright light and lower their risk ceiling during extended operation to avoid repeated manual dimming during future control cycles. However, for scenarios where users do not manually dim the light for extended periods, the system maintains the risk ceiling, ensuring relatively sufficient lighting conditions with a adequate safety margin.

[0224] In addition to the maximum allowable risk of eye strain Apart from needing to be slowly modified according to usage behavior, the light environment target vector and target weight vector in step three, as well as the brightness change coefficient in the first half of step five, can be corrected based on long-term risk trends and brightness adjustment results.

[0225] For example, if the illuminance in the reading area of ​​a task scenario is consistently higher than the target value, and the eye risk index... If the illuminance is below the reference risk value, the target illuminance value for the reading area in this scenario can be appropriately increased. If approaching the target illuminance value for the current reading area accelerates the increase in the eye risk index, the target illuminance value for the reading area in that scenario can be reduced. Alternatively, if children experience discomfort due to excessive brightness changes in certain scenarios, the brightness change coefficient can be adjusted to make brightness changes more gradual in later control cycles.

[0226] At the end of each control period, not only is the current eye use risk index recorded. With upper limit of allowable risk of eye use The relationship also records the actual illuminance of the reading area (measured in step one) and the target illuminance value of the current reading area. Deviation, projection viewing area contrast and target contrast value The deviation and the variation range of the actual luminous flux of the lighting source and the actual luminous flux of the projection source in the current cycle.

[0227] The aforementioned deviations are weighted and combined over time to obtain the cumulative target deviation and the brightness change comfort index, which are used to adjust the target parameters of the lighting environment and the brightness change coefficient. For the cumulative reading target deviation, if it manifests as excessive brightness over a long period, the target illuminance value of the reading area can be decreased, and the reading deviation weighting coefficient can be increased, so that step four emphasizes the illuminance deviation of the reading area when constructing the cost function. For the brightness change comfort index, if it manifests as excessively rapid brightness changes over a long period, the upper limits of the illumination change coefficient and the projection view change coefficient can be lowered, making the brightness adjustment trajectory in step five smoother.

[0228] When in use, the comfort information regarding the brightness change trajectory from the results of step five is fed back to the target parameters of the light environment and the brightness change step size parameters, enabling the system to have long-term cross-cycle adaptive capabilities under the same inventive concept. The target values ​​of illuminance in the reading area and contrast ratio in the projection viewing area are no longer fixed, and can slowly move forward along a direction that is neither too dark nor too bright within a safe constraint framework, which is more in line with the real ambient light and the user's preferences.

[0229] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0230] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0231] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0232] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0233] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for dynamically adjusting the ambient light adaptive brightness of a projection desk lamp, characterized in that: include, Within each control cycle, illumination and images are collected by an ambient light sensor and a camera to identify the reading area, projection viewing area, background area and line-of-sight path area, and to obtain the illuminance or brightness and contrast of each area. Based on reading and writing lighting and myopia prevention standards, the illuminance or brightness and contrast of the area are converted into multiple risk factors. The risk factors are weighted over time within a preset time window to obtain the eye use risk index. The current task scenario is determined based on the camera footage and application operation status, and safety constraints and light environment targets related to the illuminance or contrast of each area are set based on the task scenario and eye risk index. The maximum total luminous flux is determined based on the eye risk index and its allowable upper limit. Under the constraint of the maximum total luminous flux, the target luminous flux of the lighting source and the target luminous flux of the projection source are calculated in combination with the light environment target and the regional model. Based on the eye risk index, a dynamic adjustment strategy is selected. The output brightness of the lighting channel and the projection channel is adjusted according to the target luminous flux of the lighting source and the target luminous flux of the projection source. The ambient light, task scene and luminous flux allocation results are recorded to update the control parameters for subsequent control cycles.

2. The method for dynamic brightness adjustment of a projection desk lamp based on ambient light according to claim 1, characterized in that: Based on the image, the reading plane and the projection view plane are fitted by detecting the book edge and the projection view contour. The desktop area other than the reading area and the projection view area is divided into the background area, and the area containing the user's eyes projected onto the desktop is divided into the gaze path area. These are used for subsequent illumination estimation and the area labels are formed in the controller. The background area and the gaze path area are stored in a region mapping table with a one-to-one correspondence between the corresponding pixel positions.

3. The method for dynamic brightness adjustment of a projection desk lamp based on ambient light according to claim 2, characterized in that: An ambient light sensor is arranged around the lamp head of the projector to obtain the intensity of incident light from different directions. The camera is installed close to the projection light path. The output of the ambient light sensor and the image of the camera are acquired synchronously and stored in the control chip in association with the area division results within the same control cycle. The sampling time of the ambient light sensor and the camera is aligned with the start and end of the control cycle.

4. The method for dynamic brightness adjustment of a projection desk lamp based on ambient light according to claim 3, characterized in that: The risk factors include at least a first risk factor based on the deviation of the illuminance in the reading area from the reading and writing lighting standard, a second risk factor based on the uniformity of illuminance, a third risk factor based on the proportion of blue light components, and a fourth risk factor based on the flicker amplitude and the brightness of the viewing path area. The eye use risk index is a weighted combination of the risk factors and is recalculated in each control period.

5. The method for dynamic brightness adjustment of a projection desk lamp based on ambient light according to claim 4, characterized in that: The preset time window covers multiple consecutive control periods. The weighted accumulation adopts a decreasing weight sequence that gives greater weight to the most recent control period, so that newer risk factors contribute more to the eye use risk index and keep the eye use risk index value stable under the limitation of the total weight. The length of the time window can be configured according to age group.

6. The method for dynamic brightness adjustment of a projection desk lamp based on ambient light according to claim 5, characterized in that: The task scenarios include at least paper reading scenarios, mixed learning scenarios combining paper and projection, interactive scenarios primarily using projection, and desktop office scenarios primarily using keyboard input. The determination of the task scenario is based on a comprehensive assessment of the paper outline in the camera image, the proportion of the projected view, and the foreground state of the application, and the lighting environment constraints are reset when the scenario is switched.

7. The method for dynamic brightness adjustment of a projection desk lamp based on ambient light according to claim 6, characterized in that: For paper-based reading scenarios, the upper limit of the allowable risk to eyes is lower than that for other scenarios, and the illuminance target for the reading area is higher than that for the projection viewing area. For interactive scenarios where projection is the primary mode of viewing, the contrast target of the projection viewing area is higher than the illuminance target of the reading area, and the brightness constraints of the background area and the viewing path area are adjusted accordingly. The constraints and targets are stored in the form of a parameter table.

8. The method for dynamic brightness adjustment of a projection desk lamp based on ambient light according to claim 7, characterized in that: The maximum total luminous flux decreases monotonically as the eye risk index increases. When the eye risk index is below the preset threshold, the maximum total luminous flux is allowed to approach the rated luminous flux of the device. When the eye risk index approaches the upper limit of the eye risk, the maximum total luminous flux is compressed to the preset safe range. The preset threshold is related to the length of the time window.

9. The method for dynamic brightness adjustment of a projection desk lamp based on ambient light according to claim 8, characterized in that: The lighting source includes a first light subarray covering the reading area and a second light subarray covering the background area. The target luminous flux of the lighting source is first allocated to the first light subarray to meet the illuminance constraints of the reading area, and the remaining part is then allocated to the second light subarray and the ambient lighting area. The allocation ratio is preset in the factory calibration.

10. The method for dynamic brightness adjustment of a projection desk lamp based on ambient light according to claim 9, characterized in that: When the eye risk index is significantly lower than the upper limit of the eye risk allowance, the luminous flux of each channel slowly approaches the corresponding target luminous flux in small steps. When the eye risk index approaches the upper limit of the eye risk allowance, the luminous flux of the lighting source and the projection source is adjusted in a decreasing direction in larger steps. The step size is determined by the preset level factor.

11. The method for dynamic brightness adjustment of a projection desk lamp based on ambient light according to claim 10, characterized in that: When the eye risk index exceeds the upper limit of the eye risk allowable limit, the luminous flux of the projection light source is immediately reduced and the luminous flux of the lamp sub-array corresponding to the line of sight path area is reduced at the same time. While the luminous flux is reduced, a posture adjustment or short rest prompt is output to the user. The upper limit of the eye risk allowable limit is reduced in the subsequent time window so that the maximum total luminous flux in the subsequent control cycle remains at a low level.

12. The method for dynamic brightness adjustment of a projection desk lamp based on ambient light according to claim 11, characterized in that: The recorded eye risk index, task scenario sequence, and light flux allocation results are used to update the weight parameters of risk factors and the target parameters of the light environment offline or online. When the same user uses the device for a long period of time, the weight parameters and target parameters are slightly adjusted based on the user's multiple manual adjustments of the direction. The adjustment results are stored in local non-volatile memory.

13. The method for dynamic brightness adjustment of a projection desk lamp based on ambient light according to claim 12, characterized in that: The duration of the control cycle is no greater than a preset multiple of the projection screen refresh cycle. The ambient light sensor and the camera each complete at least one sampling and image acquisition in each control cycle, so that all calculations are completed based on the data acquired in the same control cycle, and the control parameters are continuously transmitted between control cycles. The duration of the control cycle is configured by software parameters during the manufacturing stage and can be selected according to different user profiles.

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