A Portable Spectral Radiation Screen Luminance Meter and Its Optical System

Abstract

The present invention discloses a portable spectro-radiation screen luminance meter and its optical system in the technical field of luminance meters, aiming to solve the problem that the spectral wavelength distribution of the incident light at the slit is inconsistent with the spectral wavelength distribution of the light emitted from the screen due to the imaging of the arranged pixels by the condenser lens. The incident light sequentially passes through a light homogenizer, a condenser lens and a slit and then irradiates on a front spherical mirror, and the front spherical mirror reflects the incident light onto a plane grating, and a rear spherical mirror reflects the light emitted from the plane grating onto a CCD; the condenser lens is fixed between a first screw cap and a base, the base is fixed on the luminance meter housing, and the light homogenizer is fixed between a second screw cap and the first screw cap. Through the spectral method measurement by grating spectroscopy, while realizing the measurement of parameters such as luminance, spectrum, and color coordinates in a small range at a short distance, portability is achieved, and the consistency of the wavelength distribution of the spectrum received by the luminance meter and the spectrum actually emitted by the screen is ensured through the light homogenizing property of the light homogenizer, improving the measurement accuracy of the screen spectrum and luminance.

Description

Technical Field

[0001] The invention belongs to the technical field of brightness meters, and in particular relates to a portable spectroscopic radiation screen brightness meter and an optical system thereof. Background Art

[0002] Common types of existing brightness meters include imaging brightness meters, aiming point brightness meters, and spectroradiometers. There is no portable brightness meter specifically for screen detection. Imaging brightness meters measure brightness by imaging a larger object at a long distance. It is difficult to accurately measure small display screens (such as smart watch screens), and compared with spectroradiometers, they are larger and less portable. Aiming point brightness meters use color filters close to the CIE standard observer color matching function to measure tristimulus values ​​to achieve measurements of parameters such as brightness and color coordinates. Since it is difficult for color filters to completely match the standard curve, the accuracy is usually lower than that of spectroradiometers. Since ordinary spectroradiometers use lenses to directly input light, the wavelength distribution of the spectrum of light entering the brightness meter will be inconsistent with the wavelength distribution of the spectrum of light emitted by the screen due to the arrangement of screen pixels, resulting in low accuracy in measuring the superimposed spectrum and brightness of screen pixels. Summary of the invention

[0003] The purpose of the present invention is to provide an optical system for a portable spectroradiometer screen brightness meter to solve the problem that the brightness meter in the prior art uses a focusing lens to directly input light, and the focusing lens images the arranged pixels, resulting in the inconsistency between the wavelength distribution of the incident light spectrum at the slit and the wavelength distribution of the screen light spectrum.

[0004] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a portable spectroscopic radiation screen brightness meter, including a homogenizer, the incident light passes through the homogenizer, a focusing lens and a slit in sequence and then shines on the front spherical reflector, the front spherical reflector reflects the incident light on a plane grating, and the rear spherical reflector reflects the light emitted by the plane grating onto a CCD; the focusing lens, the slit, the front spherical reflector, the plane grating, the rear spherical reflector and the CCD are encapsulated in a brightness meter housing, the focusing lens is fixed between a first screw cover and a base, the base is fixed on the brightness meter housing, and the homogenizer is fixed between a second screw cover and a first screw cover.

[0005] The base is provided with a first groove, and the focusing lens is arranged in the first groove.

[0006] The first rotating cover is provided with a second groove, and the light diffuser is arranged in the second groove.

[0007] The second rotary cover is made of rubber.

[0008] The distance between the condensing lens and the slit is equal to the focal length of the condensing lens.

[0009] The light homogenizing medium of the light homogenizer is opal glass that can homogenize light and absorb visible light in equal proportion.

[0010] The CCD is connected to a signal receiving circuit, which sends the incident light quantity signal to a high-speed AD conversion circuit for AD conversion and then transmits it to a central processor. The central processor controls the signal receiving circuit and the high-speed AD conversion circuit through an FPGA control circuit to change the integration time of the CCD until the incident light quantity received by the CCD meets the requirements. The central processor calculates the spectrum, brightness, and color coordinates when the incident light quantity meets the requirements and outputs them.

[0011] An optical system of a portable spectro-radiation screen luminance meter, the optical system sequentially includes along the optical axis: a light homogenizer, a condenser lens, a slit, a front spherical mirror, a plane grating, a rear spherical mirror, and a CCD. The light homogenizing medium of the light homogenizer is opal glass that can homogenize light and absorb visible light in equal proportion. The distance between the condenser lens and the slit is equal to the focal length of the condenser lens.

[0012] The thickness of the light homogenizing medium of the light homogenizer is determined by formula (1):

[0013] I = I0e -αl (1)

[0014] Wherein, I is the outgoing light intensity, I0 is the incident light intensity, e is the natural constant, α is the material light absorption coefficient, and l is the material thickness.

[0015] The types of the condenser lens include a doublet lens, a plano-convex lens, and a cylindrical lens.

[0016] Compared with the prior art, the beneficial effects achieved by the present invention: The portable spectro-radiation screen luminance meter and its optical system of the present invention ensure the consistency of the wavelength distribution of the spectrum received by the luminance meter and the spectrum emitted by the actual screen through the light homogenizing property of the light homogenizer, improve the measurement accuracy of the screen spectrum and brightness, and have portability while measuring parameters such as brightness, spectrum, and color coordinates in a small range at a short distance through spectral measurement by grating spectroscopy. Description of the Drawings

[0017] Figure 1 is a schematic cross-sectional structure diagram of a portable spectro-radiation screen luminance meter provided in Embodiment 1 of the present invention;

[0018] Figure 2 is a schematic installation structure diagram of the light homogenizer of a portable spectro-radiation screen luminance meter provided in Embodiment 1 of the present invention;

[0019] Figure 3 is a schematic installation structure diagram of the plane mirror of a portable spectro-radiation screen luminance meter provided in Embodiment 2 of the invention Figure 1 ;

[0020] Figure 4 It is a schematic diagram of the installation structure of the plane mirror of a portable spectro-radiation screen luminance meter provided by the second embodiment of the invention. Figure 2 ;

[0021] Figure 5 It is a schematic diagram of the system structure of the optical system of a portable spectro-radiation screen luminance meter provided by the embodiment of the present invention;

[0022] Figure 6 It is a schematic diagram of the system structure of a portable spectro-radiation screen luminance meter provided by the embodiment of the present invention;

[0023] Figure 7 FPGA control circuit module diagram of a portable spectro-radiation screen luminance meter provided by the embodiment of the present invention;

[0024] Figure 8 It is a schematic diagram of the working process of a portable spectro-radiation screen luminance meter provided by the embodiment of the present invention;

[0025] In the figure: 1. Light homogenizer; 2. Condensing lens; 3. Slit; 31. Base; 32. Notch; 4. Front spherical mirror; 5. Plane grating; 6. Rear spherical mirror; 7. CCD; 8. Housing; 81. Base; 811. First groove; 82. First screw cap; 821. Second groove; 83. Second screw cap; 9. Plane mirror. Specific embodiments

[0026] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the protection scope of the present invention.

[0027] Embodiment 1:

[0028] As Figure 1As shown in the figure, a portable spectro-radiation screen luminance meter includes a light homogenizer 1, a condenser lens 2, a slit 3, a front spherical mirror 4, a plane grating 5, a rear spherical mirror 6, and a CCD 7. The incident light sequentially passes through the light homogenizer 1, the condenser lens 2, and the slit 3 and then irradiates on the front spherical mirror 4. The front spherical mirror 4 reflects the incident light onto the plane grating 5, and the rear spherical mirror 6 reflects the light emitted from the plane grating 5 onto the CCD 7. The condenser lens 2 is used to converge the incident light to the slit 3. The slit 3 is used to provide a line light source required for spectral analysis. The front spherical mirror 4 is used to change the optical path direction, making the structure compact and outputting parallel light to the plane grating 5. The plane grating 5 is used for spectral splitting, so that lights of different wavelengths are emitted at different angles. The rear spherical mirror 6 is used to change the optical path direction, making the structure compact and focusing the light on the CCD 7. The CCD 7 is used to receive spectral signals. The condenser lens 2, the slit 3, the front spherical mirror 4, the plane grating 5, the rear spherical mirror 6, and the CCD 7 are encapsulated in a luminance meter housing 8. The distance between the condenser lens 2 and the slit 3 is equal to the focal length of the condenser lens 2 to ensure the incident light effect at the slit. The portable spectro-radiation screen luminance meter described in this embodiment has a compact structure, and its size can be less than 8 cm × 20 cm, which is convenient for single-handed holding and operation.

[0029] As Figure 2 shown in the figure, a base 81 is fixed on the housing 8. A first groove 811 is provided on the base 81. The condenser lens 2 is installed in the first groove 811. A first cover 82 is connected to the base 81 by a snap or thread to fix the condenser lens 2 between the first cover 82 and the base 81. A second groove 821 is provided on the first cover 82. The light homogenizer 1 is installed in the second groove 821. A second cover 83 is connected to the first cover 82 by a snap or thread to fix the light homogenizer 1 between the first cover 82 and the second cover 83.

[0030] The light homogenizing medium of the light homogenizer 1 is an opal glass that can homogenize light and absorb visible light in equal proportion, which can attenuate the light intensity of incident light of various wavelengths in equal proportion, so that the spectrum received by the CCD 7 only becomes smaller as a whole in terms of light intensity while the wavelength distribution remains unchanged. Therefore, the light homogenizer 1 can ensure that the CCD 7 is saturated only when the luminance of the measured light-emitting panel or display screen is higher on the premise of ensuring the spectral measurement accuracy, thereby improving the maximum measurable luminance of the luminance meter. The light homogenizing effect of the light homogenizer 1 is manifested in that the light is uniformly emitted in a diffuse transmission manner. When measuring a display screen, the light homogenizer 1 mixes the lights of various wavelengths emitted by the red, green, and blue pixels of the screen and uniformly emits them, and there will be no problem that the spectral wavelength distribution of the incident light at the slit 3 is inconsistent with the spectral wavelength distribution of the light emitted by the screen due to the imaging of the arranged pixels by the condenser lens 2. Therefore, the CCD 7 can accurately receive the superimposed spectral information, analyze the proportion of lights of each wavelength, and obtain an accurate luminance value.

[0031] The thickness of the light homogenizing medium of the light homogenizer 1 cannot be too thin. If it is too thin, it will lead to uneven light homogenization, unable to achieve the function of accurately measuring the screen brightness, and it will also cause the light intensity entering the slit 3 to be too large, resulting in easy saturation of the CCD 7. The thickness cannot be too thick either. If it is too thick, it will cause the light intensity entering the slit 3 to be too small, and when measuring low brightness, the exposure time of the CCD 7 will be very long. The thickness of the light homogenizing medium of the light homogenizer 1 depends on the light intensity attenuation multiple, and the light intensity attenuation multiple mainly depends on the design index of the brightness range and the optoelectronic characteristics of the CCD 7. After determining the light intensity attenuation multiple, the thickness of the light homogenizing medium of the light homogenizer 1 is calculated by Lambert-Beer's law:

[0032] I = I0e -αl (1)

[0033] where I is the outgoing light intensity, I0 is the incident light intensity, e is the natural constant, α is the material light absorption coefficient, and l is the material thickness.

[0034] To make the optical system structure compact, the light homogenizer should be as close as possible to the condenser lens, but it cannot press the condenser lens to prevent deformation and wear. By controlling the thickness of the first screw cap 82, the light homogenizer 1 can be close to but not in contact with the condenser lens 2. The second screw cap 83 is made of a soft material such as rubber, which can protect the light homogenizer 1.

[0035] Embodiment 2: The difference between this embodiment and Embodiment 1 is that a plane mirror 9 is provided between the condenser lens 2 and the slit 3. A certain angle is formed between the plane mirror 9 and the condenser lens 2 for changing the light path direction. The purpose of this setting is to adapt to the situation where in some environments, the brightness meter cannot be directly used and the lens direction needs to be changed to facilitate detection. A high-reflection film is plated on the plane mirror 9, which can achieve the effect of only changing the light path direction without affecting the spectral distribution of the incident light. The materials for making the high-reflection film include aluminum, silver, gold, etc. The light passes through the light homogenizer 1, the condenser lens 2, the plane mirror 9 in sequence and then passes through the slit 3.

[0036] As Figure 3 、 Figure 4 shown, the plane mirror 9 and the slit 3 share a base 31. There is a notch 32 at a certain angle with the slit 3 on the base 31, and the plane mirror 9 is fixed in the notch 32. In this embodiment, the angle between the notch 32 and the slit 3 is 45°, that is, the plane mirror 9 forms a 45° angle with the slit. At this time, after the incident light is reflected by the plane mirror 9, the direction changes by 90°, that is, the angle between the lens part (the part where the light homogenizer 1 and the condenser lens 2 are installed) of the brightness meter and the slit 3 is 90°. According to actual needs, by changing the angle between the plane mirror 9 and the slit 3, the incident angle of the incident light can be changed, and then the lens direction can be changed to adapt to different measurement environments.

[0037] As Figure 5As shown in the figure, the present invention also provides an optical system of a portable spectro-radiation screen luminance meter. The optical system sequentially includes, along the optical axis: a light homogenizer 1, a condenser lens 2, a slit 3, a front spherical mirror 4, a plane grating 5, a rear spherical mirror 6, and a CCD 7. The distance between the condenser lens 2 and the slit 3 is equal to the focal length of the condenser lens 2 to ensure the incident light effect at the slit. The light homogenizing medium of the light homogenizer 1 is opal glass that can homogenize light and absorb visible light proportionally. The thickness of the light homogenizing medium is determined by formula (1). The thickness of the light homogenizing medium of the light homogenizer 1 depends on the light intensity attenuation multiple, and the light intensity attenuation multiple mainly depends on the design index of the luminance range and the photoelectric characteristics of the CCD 7. The lens type of the condenser lens 2 can be a doublet lens, a plano-convex lens, a cylindrical lens, etc., according to actual needs. The plano-convex lens can converge light. The doublet lens can improve the beam quality of the incident slit 3 while converging light. The cylindrical lens can further homogenize light while converging light and obtain a line light source at the focal plane, which cooperates well with the slit 3. A plane mirror can be installed between the condenser lens 2 and the slit 3 according to actual needs. The plane mirror can change the optical path direction, so that while the overall direction of the luminance meter remains unchanged, the incident light probe part composed of the light homogenizer 1 and the condenser lens 2 can rotate, which is convenient for measurement in various situations.

[0038] As Figure 6 shown, the optical system acquires the screen spectral signal. The signal receiving circuit receives the signal of the CCD. The high-speed AD conversion circuit converts the signal by AD and sends it to the central processor. The central processor determines whether the current incident light amount is appropriate based on this and controls the signal receiving circuit and the high-speed AD conversion circuit to change the integration time of the CCD 7 through the FPGA control circuit. The central processor calculates information such as spectrum, luminance, and color coordinates based on the signal when the incident light amount is appropriate, and displays it through the display screen. Instructions are sent to the central processor using the keys, and the central processor changes the measurement mode and display content according to the instructions. The battery charging system is automatically controlled by the central processor.

[0039] As Figure 7 and Figure 8As shown in the figure, the FPGA control circuit consists of four parts: the FPGA input port, the FPGA output port, the mode adjustment module, and the timing control module. At the start of measurement, the central processor sets the baud rate of the FPGA input and output ports. The mode adjustment module sends the default setting information to the timing control module. The timing control module includes the CCD driving part and the AD driving part. The CCD driving part sends the default control timing signal and the default clock signal to the CCD signal receiving circuit. The control timing signal controls the working mode and integration time of the CCD, and the clock signal controls the working frequency of the CCD. The AD driving part sends the default configuration timing signal, the default sampling timing signal, and the default data transfer timing signal to the high-speed AD conversion circuit. The configuration timing signal, the default sampling timing signal, and the default data transfer timing signal respectively control the mode configuration, AD sampling, and AD conversion data transfer of the high-speed AD conversion circuit. The CCD signal receiving circuit outputs an analog voltage signal to the high-speed AD conversion circuit under the control of the timing signal. The high-speed AD conversion circuit converts the analog voltage signal into a digital signal under the control of the timing signal and sends it to the FPGA output port. The FPGA output port caches the digital signal and sends it to the central processor. The central processor analyzes the digital signal to determine whether the current working state of the CCD is appropriate. If the CCD is saturated, the integration time should be reduced; if the CCD signal is too small, the integration time should be increased. The central processor sends an interrupt signal to the FPGA input port. After the FPGA input port recognizes the interrupt, it sends the central processor instruction to the mode adjustment module. The mode adjustment module resets the state, and the timing control module changes the timing signal to correspondingly change the working states of the CCD signal receiving circuit and the high-speed AD conversion circuit. The central processor analyzes the new digital signal. If it is still not appropriate, the next round of adjustment is carried out. If it is appropriate, the spectral information is analyzed, and the brightness and color coordinates are calculated based on the spectral information.

[0040] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and deformations can be made, and these improvements and deformations should also be regarded as the protection scope of the present invention.

Claims

1. A portable spectro-radiation screen luminance meter, characterized in that, It includes a light homogenizer. The incident light sequentially passes through the light homogenizer, a condenser lens, and a slit and then irradiates on a front spherical mirror. The front spherical mirror reflects the incident light onto a plane grating, and a rear spherical mirror reflects the light emitted from the plane grating onto a CCD. The condenser lens, the slit, the front spherical mirror, the plane grating, the rear spherical mirror, and the CCD are encapsulated in a luminance meter housing. The condenser lens is fixed between a first screw cap and a base, and the base is fixed on the luminance meter housing. The light homogenizer is fixed between a second screw cap and the first screw cap. The base is provided with a first groove, and the condenser lens is arranged in the first groove. The first screw cap is provided with a second groove, and the light homogenizer is arranged in the second groove. A plane mirror is arranged between the condenser lens and the slit, and the included angle between the plane mirror and the slit is 45°. The distance between the condenser lens and the slit is equal to the focal length of the condenser lens. The light homogenizing medium of the light homogenizer is an opal glass that can homogenize light and absorb visible light in equal proportion. The CCD is connected to a signal receiving circuit. The signal receiving circuit sends the incident light quantity signal to a high-speed AD conversion circuit for AD conversion and then sends it to a central processor. The central processor controls the signal receiving circuit and the high-speed AD conversion circuit through an FPGA control circuit to change the integration time of the CCD until the incident light quantity received by the CCD meets the requirements. The central processor calculates the spectrum, luminance, and chromaticity coordinates when the incident light quantity meets the requirements and outputs them.

2. The portable spectro-radiation screen luminance meter according to claim 1, characterized in that, The material of the second screw cap is rubber.

3. The optical system of a portable spectro-radiation screen luminance meter, characterized in that, The optical system sequentially includes along the optical axis: a light homogenizer, a condenser lens, a slit, a front spherical mirror, a plane grating, a rear spherical mirror, and a CCD. The light homogenizing medium of the light homogenizer is an opal glass that can homogenize light and absorb visible light in equal proportion. The distance between the condenser lens and the slit is equal to the focal length of the condenser lens. A plane mirror is arranged between the condenser lens and the slit, and the included angle between the plane mirror and the slit is 45°. The CCD is connected to a signal receiving circuit. The signal receiving circuit sends the incident light quantity signal to a high-speed AD conversion circuit for AD conversion and then sends it to a central processor. The central processor controls the signal receiving circuit and the high-speed AD conversion circuit through an FPGA control circuit to change the integration time of the CCD until the incident light quantity received by the CCD meets the requirements. The central processor calculates the spectrum, luminance, and chromaticity coordinates when the incident light quantity meets the requirements and outputs them.

4. The optical system of the portable spectro-radiation screen luminance meter according to claim 3, characterized in that, The thickness of the light homogenizing medium of the light homogenizer is determined by formula (1): （1） Wherein, is the intensity of the outgoing light, is the intensity of the incident light, is the natural constant, is the light absorption coefficient of the material, is the thickness of the material.

5. The optical system of the portable spectro-radiation screen luminance meter according to claim 3, characterized in that, The types of the condenser lens include a doublet lens, a plano-convex lens, and a cylindrical lens.

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