Disclosure of Invention
The resolution measuring device mainly comprises a resolution target plate, a monochromatic filter, a pinhole sheet, a pinhole, an image intensifier (an input window and an output window of the image intensifier are both optical fiber panels), a microscope eyepiece, a shell and an eyeshade. The resolution target plate, the monochromatic filter, the pinhole sheet, the pinhole, the image intensifier, the microscope eyepiece and the eye shield are sequentially arranged along the light path direction; wherein, the pinhole piece, the pinhole, the image intensifier and the microscope eyepiece are arranged in the shell.
The light source irradiates the resolution target plate, the resolution target plate is used for providing measurement patterns, the monochromatic filter is used for generating monochromatic light, the pinhole is used for attenuating illumination and imaging, the microscope eyepiece is used for amplifying the observation visual angle of human eyes, and the eyeshade is used for preventing veiling glare.
The resolution target plate adopted by the invention meets the relevant measurement standard. Namely, the standard of the resolution target plate used by the invention is the same as that of the resolution target plate used by the original resolution measuring instrument.
The resolution target plate is provided with target plate patterns, the target plate patterns are composed of N resolution map patterns, and each resolution map pattern is composed of three mutually perpendicular equidistant horizontal dark stripes and vertical dark stripes. The contrast of the dark bars against a white background was 100%. The aspect ratio of the dark stripes was 5: 1. Assuming that the width of the dark stripe is D, the length of the dark stripe is 5D. The spacing between the dark stripes is equal to the width of the dark stripes.
The pinholes are made on 20-50 μm thick pinhole sheet, and the diameter of the pinholes is phi 0.1-1 mm. The ratio of the pinhole diameter phi to the image distance m (the distance of the pinhole from the image intensifier input window) should be greater than 5%.
The pinhole is at the front end of the image intensifier, and the front end of the pinhole is provided with a monochromatic filter with the wavelength of 550 nm. The resolution target plate is imaged on an input window of the image intensifier through the monochromatic filter and the pinhole, is enhanced through the image intensifier and is displayed on an output window of the image intensifier, and finally, human eyes adopt a microscope eyepiece to observe.
The measuring method comprises the following steps:
step 1, fixing a resolution target plate 4 on a flat wall surface of a windowless room;
step 2, completing the assembly of the measuring device; adjusting the image distance m and the object distance L;
step 3, fixing the measuring device on a tripod, adjusting the height of the tripod to enable the measuring device to be opposite to and perpendicular to the resolution target plate, turning off a common illuminating lamp in a room, turning on a light source and irradiating the resolution target plate;
step 4, starting the image intensifier to work, and observing the image of the resolution target plate on the output window of the image intensifier; adjusting the distance between the light source and the resolution target plate or the power of the light source to ensure that human eyes obtain comfortable observation brightness of the resolution target plate;
step 5, observing the pattern of the resolution target plate; when observing, starting from the 1 st block, if the three horizontal and three vertical dark stripes of the 1 st block pattern can be resolved, continuing to observe the 2 nd block pattern; sequentially observing each pattern of the target plate; until observing the Nth pattern, the width d of the minimum dark stripe which can be resolved by human eyes when observing the (N-1) th pattern is recorded until the three horizontal dark stripes and the three vertical dark stripes can not be resolved simultaneously;
step 6, calculating the resolution R of the image intensifier according to the following formula
Compared with the prior art, the invention has the advantages of simple measuring device, low requirement on use conditions and convenient carrying.
Detailed Description
As shown in fig. 2, the resolution measuring apparatus of the present invention is mainly composed of a resolution target plate 4, a monochromatic filter 3, a pinhole sheet 10, a pinhole 11, an image intensifier 6 (an input window 61 and an output window 62 of which are both fiber optic panels), a microscope eyepiece 7, a housing 12, and an eye mask 13. Along the light path direction, the resolution target plate 4, the monochromatic filter 3, the pinhole piece 10, the pinhole 11, the image intensifier 6, the microscope eyepiece 7 and the eye mask 13 are sequentially arranged; wherein the pinhole sheet 10, the pinhole 11, the image intensifier 6 and the microscope eyepiece 7 are arranged in the shell 12.
The light source 1 irradiates the resolution target plate 4, the resolution target plate 4 is used for providing measurement patterns, the monochromatic filter 3 is used for generating monochromatic light, the pinhole 11 is used for attenuating illumination and imaging, the microscope eyepiece 7 is used for amplifying the observation visual angle of human eyes 8, and the eyeshade 13 is used for preventing veiling glare.
The resolution target plate adopted by the invention meets the relevant measurement standard. Namely, the standard of the resolution target plate used by the invention is the same as that of the resolution target plate used by the original resolution measuring instrument.
As shown in fig. 3 to 5, no matter the resolution target plate 4 is a cloth target plate or a transparent film target plate, the target plate pattern 9 is composed of 6 resolution patterns, and each resolution pattern is composed of three equidistant horizontal dark stripes 91 and three perpendicular dark stripes 92 which are perpendicular to each other. The contrast of the dark bars against a white background was 100%. The aspect ratio of the dark stripes was 5: 1. Assuming that the width of the dark stripe is D, the length of the dark stripe is 5D. The spacing between the dark stripes is equal to the width of the dark stripes.
The pinhole 11 is made on a pinhole sheet 10 (such as a nickel sheet) with the thickness of 20-50 μm, and the diameter of the pinhole 11 is phi 0.1-1 mm. The ratio of the diameter phi of the pinhole 11 to the image distance m (the distance of the pinhole 11 from the image intensifier input window 61) should be greater than 5%.
The pinhole 11 is at the front end of the image intensifier 6, and the front end of the pinhole 11 is provided with a monochromatic filter 3 with the wavelength of 550 nm. The resolution target plate 4 is imaged on an input window 61 of an image intensifier 6 through a monochromatic filter 3 and a pinhole 11, is enhanced through the image intensifier 6, is displayed on an output window 62 of the image intensifier 6, and finally, human eyes 8 adopt a microscope eyepiece 7 with 10 times to observe.
In measurement, the width d of the smallest dark stripe that the human eye 8 can resolve is observed by the human eye 8, and then the resolving power R of the image intensifier 6 is calculated by the formula (1):
in the formula, L represents the object distance (i.e., the distance of the pinhole from the resolution target plate).
Example 1
This embodiment uses white cloth as the resolution target plate.
The resolution target plate 4 is first fixed to a flat wall surface of a windowless room.
As shown in fig. 4, the resolution target plate 4 is a cloth target plate with a dark stripe pattern formed on a white cloth 14. The dark stripes are made of black light absorbing material, such as black paint.
The target plate includes 6 resolution patterns numbered 1 to 6, respectively. The width D of each pattern dark bar is marked on the right side of the corresponding pattern.
The image intensifier 6 to be measured (numbered 1999-07-0231) is incorporated into the housing 12 of the measuring device. The input window 61 and the output window 62 of the image intensifier 6 are both fiber optic faceplates.
The pinhole piece 10 is installed, the diameter of the pinhole 10 is phi 0.5mm, and the image distance m is 10 mm.
And adjusting the distance between the measuring device and the cloth mark target plate to ensure that the object distance L is 10 m.
And fixing the measuring device on the tripod, and adjusting the height of the tripod to ensure that the measuring device is opposite to and vertical to the label distribution target plate. The common illuminating lamp of the room is turned off, and the light source 1 adopts a common tungsten lamp (desk lamp) to irradiate the target plate.
The working power of the image intensifier 6 is turned on, so that the image intensifier 6 works normally, and simultaneously, the image of the label plate arranged on the output window 62 of the image intensifier 6 is observed. The distance between the tungsten lamp and the label distribution target plate or the power of the tungsten lamp is adjusted, so that the human eyes 8 obtain comfortable observation brightness of the label distribution target plate.
The pattern of the cloth target plate was carefully observed. The observation starts from block 1. If the 1 st pattern has three horizontal and three vertical dark stripes resolved, then the 2 nd pattern is observed. The observation of each pattern of the target plate was continued in turn. When the 5 th pattern is observed, three horizontal dark stripes and three vertical dark stripes cannot be simultaneously resolved.
The width of the 4 th pattern dark stripe is 8.8mm, i.e. the minimum distinguishable dark stripe width d is 8.8 mm.
The formula (1) was substituted with L10000 mm, m 10mm, and d 8.8mm, and the resolution of the measurement sample by the image intensifier was calculated to be 57lp mm-1。
The working power supply of the image intensifier 6 is turned off, the room lighting lamp is turned on, the common tungsten lamp (desk lamp) of the light source 1 is turned off, and the measurement is finished.
Example 2
This example uses a transparent film as the resolution target plate.
First, the resolution target plate is fixed on the flat white wall surface of the windowless room.
As shown in fig. 5, the resolution target 4 is a transparent film target, and is a dark stripe pattern formed on the transparent film 15. The dark stripes are made of black light absorbing material, such as black paint.
The target plate includes 6 resolution patterns numbered 1 to 6, respectively. The width D of each pattern dark bar is marked on the right side of the corresponding pattern.
An image intensifier to be measured (serial number 1997-06-0211) is enclosed in the housing of the measuring device. The input window and the output window of the image intensifier are both optical fiber panels.
The pinhole piece 10 is installed, the diameter of the pinhole is phi 0.5mm, and the image distance m is 10 mm.
The distance between the measuring device and the transparent film target plate is adjusted so that the object distance L is 10 m.
And fixing the measuring device on the tripod, and adjusting the tripod to enable the measuring device to be opposite to and perpendicular to the transparent thin film target plate. The common illuminating lamp of the room is turned off, and the light source 1 adopts a common tungsten lamp (desk lamp) to irradiate the transparent film target plate.
The working power of the image intensifier 6 is turned on to make the image intensifier 6 work normally, and the image of the transparent film target plate on the output window 62 of the image intensifier is observed at the same time. The distance between the tungsten lamp and the transparent film target plate or the power of the tungsten lamp is adjusted, so that the human eyes 8 obtain comfortable observation brightness of the transparent film target plate.
The pattern of the transparent film target plate was carefully observed. The observation starts from block 1. If the 1 st pattern has three horizontal and three vertical dark stripes resolved, then the 2 nd pattern is observed. The observation of each pattern of the target plate was continued in turn. When the 6 th pattern is observed, three horizontal dark stripes and three vertical dark stripes cannot be simultaneously resolved.
The width of the 5 th pattern dark stripe is 7.8mm, i.e. the minimum distinguishable dark stripe width d is 7.8 mm.
The formula (1) was substituted with L10000 mm, m 10mm and d 7.8mm, and the resolution of the image intensifier measurement sample was calculated to be 64lp mm-1。
The working power supply of the image intensifier 6 is turned off, the room lighting lamp is turned on, the common tungsten lamp (desk lamp) of the light source 1 is turned off, and the measurement is finished.