Brightness detection method

Abstract

The present invention provides a brightness detection method that can use an industrial camera to analyze the number of light spots in a light-emitting diode (LED), thereby accurately detecting the luminance of the LED. The method includes the following steps: obtaining multiple reference images of multiple light-emitting devices; obtaining the number of reference light spots in each of the multiple reference images; measuring the brightness of each of the multiple light-emitting devices; obtaining a relationship curve between the number of reference light spots and the brightness of the multiple light-emitting devices based on the obtained number of reference light spots and the measured brightness of the multiple light-emitting devices; obtaining a reference image of the light-emitting device to be measured; obtaining the number of reference light spots in the reference image; and obtaining the brightness of the light-emitting device to be measured based on the relationship curve and the number of reference light spots.

Description

Technical Field

[0001] The present invention relates to a brightness detection technology, and in particular to a brightness detection method for a light-emitting diode (LED). Background Art

[0002] Light-emitting diodes (LEDs) have become widely used as an environmentally friendly light source that can improve energy conservation. In manufacturing plants, current methods for measuring the brightness of LEDs and the surfaces on which they are mounted include human visual recognition, specialized automated LED testers, and industrial cameras.

[0003] Human visual recognition relies on human operators to visually determine the correct color and brightness of the LEDs. This approach offers the advantage of simple setup, but it also relies entirely on human judgment, which can lead to poor quality control due to poor personnel discipline and prevents automation. Professional automated testers, on the other hand, transmit light from the LEDs to the automated tester via optical fiber. The automated tester analyzes the light and typically generates color and brightness values in various formats, such as primary colors, hue, saturation, and xy values. This approach offers the advantage of high accuracy and automation, but it also increases manufacturing costs.

[0004] The method using an industrial camera involves photographing LEDs and then analyzing the image to determine their color and brightness. Compared to the two aforementioned methods, the industrial camera approach offers a better balance of inspection quality, automation, and manufacturing costs, offering significant advantages when inspecting large numbers of LEDs simultaneously. However, the brightness of LEDs easily reaches the saturation level of the industrial camera itself, making accurate brightness determination possible only at the edges of the pattern, resulting in poor accuracy. Furthermore, adjusting saturation to detect brightness can distort the actual pattern, making it impossible to detect defects such as LED smudges or obstructions. Summary of the Invention

[0005] The present invention provides a brightness detection method, which can use an industrial camera to analyze the number of light spots (light spot area) of a light-emitting diode, thereby accurately detecting the light-emitting brightness of the light-emitting diode.

[0006] According to an embodiment of the present invention, the brightness detection method of the present invention can be used to detect the brightness of a light-emitting device to be tested, and includes the following steps: obtaining multiple reference images of multiple light-emitting devices; obtaining the number of reference light spots in each reference image in the multiple reference images; measuring the brightness of multiple light-emitting devices respectively; obtaining a relationship curve between the number of reference light spots and the brightness based on the obtained number of reference light spots and the measured brightness of the multiple light-emitting devices; obtaining a reference image of the light-emitting device to be tested; obtaining the number of reference light spots in the reference image; and obtaining the brightness of the light-emitting device to be tested based on the relationship curve and the number of reference light spots.

[0007] Based on the above, the brightness detection method of the present invention can obtain a curve showing the relationship between the number of reference light spots and brightness. Thus, even when using an industrial camera for detection, high accuracy can be achieved, balancing accuracy and manufacturing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a block diagram of a brightness detection system according to an embodiment of the present invention;

[0009] Figure 2 is a flow chart of a brightness detection method according to an embodiment of the present invention;

[0010] Figure 3 is a schematic diagram showing an image of a light emitting device according to an embodiment of the present invention;

[0011] Figure 4 is an example of a color model according to an embodiment of the present invention;

[0012] Figure 5A and Figure 5B is a schematic diagram of a white light spot according to an embodiment of the present invention;

[0013] Figure 6A is a graph showing the relationship between the number of reference light spots and the pulse width modulation signal according to an embodiment of the present invention;

[0014] Figure 6B is a diagram showing the relationship between brightness and pulse width modulation signal according to an embodiment of the present invention;

[0015] Figure 6C FIG. 4 is a diagram showing the relationship between the number of reference light spots and brightness according to an embodiment of the present invention. DETAILED DESCRIPTION

[0016] Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals are used in the drawings and the description to refer to the same or like parts.

[0017] Figure 1 FIG is a block diagram of a brightness detection system according to an embodiment of the present invention. Figure 1 The brightness detection system 100 is used to detect the brightness of a light-emitting device. The brightness detection system 100 includes a first light-emitting device 110 , a second light-emitting device 120 , an image acquisition device 130 , a brightness meter 140 , and an electronic device 150 .

[0018] The first light-emitting device 110 and the second light-emitting device 120 are, for example, light-emitting diodes (LEDs) or organic light-emitting diodes (OLEDs) or other light-emitting components. The first light-emitting device 110 and the second light-emitting device 120 are respectively products to be tested with different brightness. In this embodiment, the first light-emitting device 110 is, for example, the light-emitting device with the highest brightness among all the products to be tested, and the second light-emitting device 120 is, for example, the light-emitting device with the lowest brightness among all the products to be tested, but the present invention is not limited to this. In addition, two light-emitting devices are used for illustration in this embodiment, but the present invention is not limited to this. Those skilled in the art can determine the number of light-emitting devices to be used according to their actual needs.

[0019] The image acquisition device 130 is, for example, a digital camera, a digital video camera, a webcam, or a surveillance camera equipped with an industrial camera. The image acquisition device 130 is used to acquire reference images of the first light emitting device 110 and the second light emitting device 120 respectively through the industrial camera.

[0020] The luminance meter 140 is, for example, a spectroradiometer manufactured by Konica Minolta, Inc. The luminance meter 140 is used to measure the luminance of the first light emitting device 110 and the second light emitting device 120 respectively.

[0021] The electronic device 150 can be connected to the image acquisition device 130 and the luminance meter 140 via a wired or wireless connection. The electronic device 150 is, for example, a personal computer, a smartphone, a personal digital assistant (PDA), a PDA phone, a notebook computer, a tablet computer, or a smart TV, and includes a storage device 152 and a processor 154.

[0022] The storage device 152 is used to store data such as images and computer programs, and can be, for example, any type of fixed or removable random access memory (RAM), read-only memory (ROM), flash memory, hard disk or other similar devices, integrated circuits and combinations thereof.

[0023] The processor 154 is electrically coupled to the storage device 152 and can be, for example, a central processing unit (CPU), or other programmable general-purpose or special-purpose microprocessor, digital signal processor (DSP), programmable logic controller, application-specific integrated circuit (ASIC), or other similar components or combinations thereof. In this embodiment, the processor 154 can load a computer program from the storage device 152 to execute the power control method of the present invention.

[0024] The dimming device 160 is electrically coupled to the first light-emitting device 110 and the second light-emitting device 120. The dimming device 160 can be a known hardware component or circuit capable of generating a pulse-width modulation signal PWM. The dimming device 160 is configured to adjust the duty cycle of the pulse-width modulation signal PWM within a predetermined range, thereby controlling the brightness of the first light-emitting device 110 and the second light-emitting device 120. In this embodiment, the dimming device 160 is configured independently of the electronic device 150. In another embodiment, the dimming device 160 can also be integrated into the electronic device 150, but the present invention is not limited thereto.

[0025] Figure 2 This is a flow chart of a brightness detection method according to an embodiment of the present invention. Figure 1 and Figure 2 The method of this embodiment is applicable to Figure 1 When executing the brightness detection method of this embodiment, the operator needs to properly set up the shooting environment of the image acquisition device 130 and adjust the fixed position of the industrial camera of the image acquisition device 130 to fix its shooting distance, focal length, brightness and contrast when the image acquisition device 130 acquires the reference images of the first light-emitting device 110 and the second light-emitting device 120. In addition, Figure 3 FIG is a schematic diagram showing an image of a light emitting device according to an embodiment of the present invention. Figure 3 As shown, while making the acquired light-emitting device image IMG0 fill the entire acquisition screen as much as possible, some space should be left at the edge (the image ratio is preferably 80%) to prevent the problem of incomplete acquisition screen due to errors in each product placement and differences in the fixation of multiple cameras.

[0026] The following describes various steps of the brightness detection method for detecting the brightness of the light-emitting device to be detected in accordance with the present invention with reference to various components in the brightness detection system 100 .

[0027] In step S202, the electronic device 150 may capture a plurality of first reference images IMG1 of the first light-emitting device 110 and a plurality of second reference images IMG2 of the second light-emitting device 120 via the image capture device 130. Specifically, the dimming device 160 may adjust the duty cycle of the pulse-width modulation signal PWM within a predetermined range (e.g., 53%-84%). Thus, the image capture device 130 may capture a plurality of first reference images IMG1 corresponding to different duty cycles of the first light-emitting device 110, and a plurality of second reference images IMG2 corresponding to different duty cycles of the second light-emitting device 120. For example, the image capture device 130 may capture a plurality of first reference images IMG1 and a plurality of second reference images IMG2 corresponding to different duty cycles of 53%, 57%, 61%, 65%, 69%, 73%, 76%, 80%, and 84%, which are reference values.

[0028] Next, the processor 154 may analyze the plurality of first reference images IMG1 and the plurality of second reference images IMG2, and in step S204, obtain the number of reference light dots in each of the plurality of first reference images IMG1 and the plurality of second reference images IMG2. In this embodiment, the processor 154 analyzes the number of white light dots. The processor 154 may analyze the plurality of first reference images IMG1 and the plurality of second reference images IMG2 based on a color model to obtain the number of white light dots in the plurality of first reference images IMG1 and the plurality of second reference images IMG2 when the duty cycle of the pulse width modulation signal PWM is a plurality of reference values of 53%, 57%, 61%, 65%, 69%, 73%, 76%, 80%, and 84%. Figure 4 is an example of a color model according to an embodiment of the present invention. Figure 4 The minimum (min) and maximum (max) values of hue H, saturation S, and brightness V of various colors (black, gray, white, red, orange, yellow, green, cyan, and blue-violet) are listed. In this embodiment, the processor 154 can use Figure 4 The number of white light dots in each reference image under different duty cycles of the pulse width modulation signal PWM is obtained based on the white specifications (hue: 0-180, saturation: 0-30 and brightness: 221-225).

[0029] For example, Figure 5A and Figure 5B FIG. 4 is a schematic diagram of a white light spot according to an embodiment of the present invention. Figure 5AThe white light dots WLS in the reference image IMG0 of the light emitting device identified according to the color model are represented by the white light dots WLS. The white light dots WLS represent the light shape presented by a plurality of light dots gathered together. In one embodiment, the processor 154 can also determine the light shape, for example, whether the white light dots WLS are all in Figure 5A The range surrounded by the dotted line DL in the figure is used to screen out defective light-emitting devices.

[0030] Figure 5B express Figure 5A The enlarged image of the edge of the circled range CS. Since the white light point WLS represents the luminous shape presented by multiple light points gathered together, Figure 5B In one embodiment, the processor 154 can also determine whether the housing of the light emitting device is damaged or has burrs based on the shape of the white light spot WLS, so as to screen out defective light emitting devices.

[0031] Although the number of white light spots in the reference image is analyzed in this embodiment, the present invention is not limited thereto. In other embodiments, the number of white light spots in the reference image may be analyzed. Figure 4 The color model of other colors is used to analyze the number of reference light points.

[0032] Please return Figure 2 In step S206, the electronic device 150 may measure the brightness of the first light-emitting device 110 and the second light-emitting device 120 using the brightness meter 140. Specifically, the brightness meter 140 may measure the brightness of the first light-emitting device 110 and the second light-emitting device 120 when the duty cycle of the pulse width modulation signal PWM is a plurality of reference values: 53%, 57%, 61%, 65%, 69%, 73%, 76%, 80%, and 84%.

[0033] It should be noted that the present invention does not limit the order of the steps for acquiring multiple first reference images IMG1 of the first light-emitting device 110 and multiple second reference images IMG2 of the second light-emitting device 120 using the image acquisition device 130, and measuring the brightness of the first light-emitting device 110 and the second light-emitting device 120 using the luminance meter 140. Typically, in a factory, an operator first places the first light-emitting device 110 on a fixture, and then uses the image acquisition device 130 and the luminance meter 140 to acquire multiple first reference images IMG1 of the first light-emitting device 110 and measure their brightness. The operator then replaces the first light-emitting device 110 with the second light-emitting device 120 and places it on the fixture, and then uses the image acquisition device 130 and the luminance meter 140 to acquire multiple second reference images IMG2 of the second light-emitting device 120 and measure their brightness. However, the present invention is not limited to this.

[0034] Furthermore, in this embodiment, the number and brightness of reference light spots are analyzed when the duty cycle of the pulse width modulation signal PWM is at multiple reference values of 53%, 57%, 61%, 65%, 69%, 73%, 76%, 80%, and 84%. However, the present invention is not limited thereto. Those skilled in the art may determine the reference value to be used based on the characteristics of the actual product to be tested.

[0035] Please return Figure 2 In step S208 , the processor 154 may obtain a relationship curve between the number of reference light spots and the brightness based on the obtained number of reference light spots and the measured brightness of the first light emitting device 110 and the second light emitting device 120 .

[0036] After obtaining the relationship curve, in step S210, the electronic device 150 may obtain a reference image of the light-emitting device under test via the image acquisition device 130. Next, in step S212, the processor 154 may obtain the number of reference light spots in the reference image. Finally, in step S214, the processor 154 may obtain the brightness of the light-emitting device under test based on the obtained relationship curve and the number of reference light spots.

[0037] The following examples illustrate the derivation and verification of the relationship curve.

[0038] Figure 6A FIG. 1 is a diagram showing the relationship between the number of reference light spots and the pulse width modulation signal according to an embodiment of the present invention. Figure 6A The vertical axis is the number of reference light spots, and the horizontal axis is the duty cycle of the pulse width modulation signal PWM. Figure 6A In FIG, curve S1 represents the relationship between the number of reference light spots of the first light emitting device 110 and the duty cycle of the pulse width modulation signal PWM obtained by the processor 154 based on the plurality of first reference images IMG1, and curve S2 represents the relationship between the number of reference light spots of the second light emitting device 120 and the duty cycle of the pulse width modulation signal PWM obtained by the processor 154 based on the plurality of second reference images IMG2. Figure 6A Curves S1 and S2 in the figure analyze the linearity of the reference number of light spots and the duty cycle of the pulse-width modulation signal PWM. Curve S1 achieves a linearity of 99.57%, while curve S2 achieves a linearity of 99.86%. Both curves achieve linearity levels exceeding 99.5%. Furthermore, the predetermined range of the pulse-width modulation signal PWM in this embodiment is centered around 69%, for example. Typically, only the desired brightness range needs to be calibrated; a smaller range provides higher accuracy.

[0039] Figure 6B FIG. 1 is a diagram showing the relationship between brightness and pulse width modulation signal according to an embodiment of the present invention. Figure 6BThe vertical axis is brightness, and the horizontal axis is the duty cycle of the pulse width modulation signal PWM. Figure 6B In the embodiment, the curve S3 represents the relationship between the brightness of the first light emitting device 110 and the duty cycle of the pulse width modulation signal PWM measured by the brightness meter 140, and the curve S4 represents the relationship between the brightness of the second light emitting device 120 and the duty cycle of the pulse width modulation signal PWM measured by the brightness meter 140. Figure 6B Curves S3 and S4 in the figure perform linearity analysis on the brightness and duty cycle of the pulse width modulation signal PWM. The linearity of curve S3 is 99.89%, and the linearity of curve S4 is 99.95%. The linearity of both curves can reach above 99.8%.

[0040] Figure 6C FIG. 4 is a diagram showing the relationship between the number of reference light spots and brightness according to an embodiment of the present invention. Figure 6C The vertical axis is the number of reference light points, and the horizontal axis is the brightness. Figure 6C In the figure, curve S5 represents the processor 154 according to Figure 6A and Figure 6B The numerical relationship on the curves S1-S4 is presented to obtain the relationship curve between the number of reference light spots and the brightness. In this embodiment, the quadratic curve fitting formula of the curve S5 is y=-0.016x 2 +83.074x+57965, where x is the brightness and y is the number of reference light points, and the fitting degree is above 99.85%. In this way, under a fixed shooting environment, an industrial camera can be used to accurately measure the brightness of the light-emitting device under test based on the fitting formula of curve S5.

[0041] It should be noted that if the required brightness range is larger, the pulse width modulation signal (PWM) range can be expanded to 0% to 100%, and a corresponding curve showing the relationship between the number of light points and brightness can be obtained. While the resulting linear relationship may not be a straight line, a corresponding relationship can be found through quadratic curve fitting, generally achieving a test accuracy of over 99%.

[0042] In summary, the brightness measurement method of the present invention can generate a curve showing the relationship between the number of reference light points and brightness based on the number of reference light points obtained by analyzing a reference image captured by an image acquisition device and the brightness measured by a luminance meter. This curve can then be used to measure the brightness of the light-emitting device under test. This method can achieve high accuracy even when using an industrial camera, balancing accuracy and manufacturing cost.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A brightness detection method for detecting the brightness of a light-emitting device to be tested, characterized in that: The following steps are involved: acquiring a plurality of reference images of a plurality of light emitting devices; Obtaining the number of reference light spots in each reference image of the plurality of reference images; measuring the brightness of the plurality of light-emitting devices respectively; Obtaining a relationship curve between the number of reference light spots and the brightness according to the obtained number of reference light spots and the measured brightness of the plurality of light-emitting devices; Acquiring a reference image of the light-emitting device to be tested; Obtaining the number of reference light spots in the reference image; as well as The brightness of the light-emitting device to be tested is obtained according to the relationship curve and the number of reference light spots.

2. The brightness detection method according to claim 1, wherein: When acquiring the plurality of reference images of the plurality of light emitting devices, a shooting distance, a focal length, brightness, and a contrast are fixed.

3. The brightness detection method according to claim 1, wherein: The plurality of light-emitting devices include a first light-emitting device and a second light-emitting device, and the step of acquiring the plurality of reference images of the plurality of light-emitting devices includes: adjusting the duty cycle of the pulse width modulation signal within a predetermined range; acquiring a plurality of first reference images corresponding to different duty cycles of the first light emitting device; and A plurality of second reference images corresponding to different duty cycles of the second light emitting device are acquired.

4. The brightness detection method according to claim 3, wherein: The step of obtaining the number of reference light spots in each of the plurality of reference images comprises: The first reference images and the second reference images are analyzed according to a color model to respectively obtain the number of reference light spots in the first reference images and the second reference images when the duty cycle of the pulse width modulation signal is a plurality of reference values.

5. The brightness detection method according to claim 3, characterized in that: The step of measuring the brightness of the plurality of light emitting devices respectively comprises: The brightness of the first light emitting device and the second light emitting device is measured by a brightness meter when the duty cycle of the pulse width modulation signal is a plurality of reference values. The brightness detection method according to claim 1 , wherein: The reference light point quantity is the quantity of white light points.

7. The brightness detection method according to claim 1, wherein: The following steps are also included: The light-emitting shape corresponding to the number of reference light spots is determined, and defective light-emitting devices are screened out according to the light-emitting shape.

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