{"id":1931,"date":"2017-10-13T22:44:57","date_gmt":"2017-10-13T20:44:57","guid":{"rendered":"https:\/\/www.adimec.com\/ocr-algorithms-work-better-with-high-quality-images-for-accurate-automated-license-plate-recognition-alpr\/"},"modified":"2018-07-27T17:13:41","modified_gmt":"2018-07-27T15:13:41","slug":"ocr-algorithms-work-better-with-high-quality-images-for-accurate-automated-license-plate-recognition-alpr","status":"publish","type":"post","link":"https:\/\/www.adimec.com\/ja\/ocr-algorithms-work-better-with-high-quality-images-for-accurate-automated-license-plate-recognition-alpr\/","title":{"rendered":"OCR algorithms work better with high quality images for accurate Automated License Plate Recognition ALPR"},"content":{"rendered":"<div class=\"hs-migrated-cms-post\">\n<p>Unlike what is shown on TV, you cannot zoom into a blurry image and expect to get more details.&nbsp; An image with acceptable sharpness and contrast must be acquired with the appropriate system from the start.&nbsp; This means the right image sensor, camera, optics, and lighting all combined in a reliable way.<\/p>\n<p><!--more--><\/p>\n<p>So what defines good image quality for <a href=\"https:\/\/www.adimec.com\/markets-2\/\" title=\"ALPR\" target=\"_blank\">ALPR<\/a>?<\/p>\n<p>The first step is to have reliable triggering in order to have the license plate in the proper location in the image, which can be especially difficult in multi-lane systems.&nbsp; After that, a good\/accurate image can be described by:<\/p>\n<ul>\n<li>Good Sharpness<\/li>\n<li>Sufficient Contrast<\/li>\n<li>Free of artifacts<\/li>\n<li>And sometimes with accurate color<\/li>\n<\/ul>\n<p>These are qualitative explanations so here some images to demonstrate the point.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" id=\"img-1329301416633\" src=\"\/\/cdn2.hubspot.net\/hub\/20421\/file-13402126-png\/images\/bad-light-c-onditions.png\" border=\"0\" alt=\"OCR image for ALPR\" width=\"294\" height=\"147\" \/><\/p>\n<p><strong>Figure 1.&nbsp; Artifacts from insufficient lighting control<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" id=\"img-1329301667429\" src=\"\/\/cdn2.hubspot.net\/hub\/20421\/file-13403231-png\/images\/motion-blur.png\" border=\"0\" alt=\"ITS ALPR Motion Blur\" width=\"294\" height=\"147\" \/><\/p>\n<p><strong>Figure 2.&nbsp; Insufficient Sharpness due to Motion Blur<\/strong><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" id=\"img-1329301772403\" src=\"\/\/cdn2.hubspot.net\/hub\/20421\/file-13403121-png\/images\/low-contrast_copy.png\" border=\"0\" alt=\"Low contrast ITS ALPR\" width=\"294\" height=\"147\" \/><\/p>\n<p><strong>Figure 3.&nbsp; Insufficient Contrast from limited dynamic range<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p>Some good background information on license plate acquisition algorithms and technology is provided on: <a href=\"http:\/\/www.platerecognition.info\/1102.htm\" title=\"http:\/\/www.platerecognition.info\/1102.htm\" target=\"_blank\">http:\/\/www.platerecognition.info\/1102.htm<\/a><\/p>\n<p>The sources of these image quality issues can vary.&nbsp; Some possible reasons are shown in the table below and are further detailed in our next series of blogs.<\/p>\n<table border=\"1\" cellspacing=\"0\" cellpadding=\"0\">\n<tbody>\n<tr>\n<td valign=\"top\" width=\"76\">\n<p><b>Image Quality Parameter<\/b><\/p>\n<\/td>\n<td valign=\"top\" width=\"163\">\n<p><b>Corresponding Source of Limitations<\/b><\/p>\n<\/td>\n<td valign=\"top\" width=\"187\">\n<p><b>Image System Parameters to Control<\/b><\/p>\n<\/td>\n<\/tr>\n<tr>\n<td valign=\"top\" width=\"76\">\n<p><a href=\"http:\/\/info.adimec.com\/blogposts\/bid\/78387\/Best-Image-for-Automatic-License-Plate-Recognition-ALPR-part-1-Sharpness\" title=\"Sharpness\" target=\"_blank\">Sharpness<\/a><\/p>\n<\/td>\n<td valign=\"top\" width=\"163\">\n<p>Limited Depth of Field<\/p>\n<p>Motion Blur<\/p>\n<p>Variable Lighting<\/p>\n<p>&nbsp;<\/p>\n<\/td>\n<td valign=\"top\" width=\"187\">\n<p>F Value of Lens<\/p>\n<p>Sensitivity of Image Sensor<\/p>\n<p>Iris Control<\/p>\n<p>&nbsp;<\/p>\n<\/td>\n<\/tr>\n<tr>\n<td valign=\"top\" width=\"76\">\n<p><a href=\"http:\/\/info.adimec.com\/blogposts\/bid\/79125\/Best-Image-for-Automatic-License-Plate-Recognition-ALPR-part-2-Contrast\" title=\"Contrast\" target=\"_blank\">Contrast<\/a><\/p>\n<\/td>\n<td valign=\"top\" width=\"163\">\n<p>Limited number of images<\/p>\n<p>Reflections of the license plate<\/p>\n<p>Reflections of snow, rain, flog<\/p>\n<\/td>\n<td valign=\"top\" width=\"187\">\n<p>Frame rate of the image sensor\/camera<\/p>\n<p>Dynamic range of the image sensor\/camera<\/p>\n<\/td>\n<\/tr>\n<tr>\n<td valign=\"top\" width=\"76\">\n<p><a href=\"http:\/\/info.adimec.com\/blogposts\/bid\/79131\/Best-Image-for-Automatic-License-Plate-Recognition-ALPR-part-3-Remove-Image-Artifacts\" title=\"Artifacts\" target=\"_blank\">Artifacts<\/a><\/p>\n<\/td>\n<td valign=\"top\" width=\"163\">\n<p>Ghost images<\/p>\n<p>Bright spots and streaks from sun exposure and reflections<\/p>\n<\/td>\n<td valign=\"top\" width=\"187\">\n<p>Alignment of filter, lens, and lighting<\/p>\n<p>Channel Matching in the camera<\/p>\n<p>Blooming and smear control in the camera<\/p>\n<\/td>\n<\/tr>\n<tr>\n<td valign=\"top\" width=\"76\">\n<p>Color<\/p>\n<\/td>\n<td valign=\"top\" width=\"163\">\n<p>Inaccurate Color reproduction<\/p>\n<\/td>\n<td valign=\"top\" width=\"187\">\n<p>Accurate color calculations and automatic white balance in the camera<\/p>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Proper alignment of the entire optical path determines the quality of the image captured, which is especially vital in high-speed situations.&nbsp; With a higher quality of the input image, the better starting point for the license plate recognition algorithm, and therefore the higher license plate recognition accuracy.&nbsp;<\/p>\n<p>For more details on <a href=\"http:\/\/info.adimec.com\/blogposts\/bid\/78387\/Best-Image-for-Automatic-License-Plate-Recognition-ALPR-part-1-Sharpness\" title=\"optimizing sharpness\" target=\"_blank\">optimizing sharpness<\/a> and <a href=\"http:\/\/info.adimec.com\/blogposts\/bid\/79125\/Best-Image-for-Automatic-License-Plate-Recognition-ALPR-part-2-Contrast\" title=\"contrast\" target=\"_blank\">contrast<\/a>, and minimizing artifacts, see our blogs in the coming weeks.<\/p>\n<p>Can&rsquo;t wait?<\/p>\n<p>You can already read the following blogs about this:<\/p>\n<ul>\n<li><a href=\"http:\/\/info.adimec.com\/blogposts\/bid\/77626\/Considerations-when-using-machine-vision-cameras-in-traffic-applications-ITS\" title=\"Opportunities and challenges of taking advantage of advancements in machine vision for ITS applications\" target=\"_blank\">Opportunities and challenges of taking advantage of advancements in machine vision for ITS applications<\/a><\/li>\n<li><a href=\"http:\/\/info.adimec.com\/blogposts\/bid\/77767\/Camera-and-Image-Acquisition-Requirements-for-Different-ALPR-Applications\" title=\"Camera and image system requirements for different automatic license plate recognition or automatic number plate recognition (ALPR or ANPR) applications.\" target=\"_blank\">Camera and image system requirements for different automatic license plate recognition or automatic number plate recognition (ALPR or ANPR) applications.<\/a>&nbsp;<\/li>\n<li><a href=\"http:\/\/info.adimec.com\/blogposts\/bid\/54116\/In-camera-Color-Processing-from-a-Mosaic-Color-Filter-Array-e-g-Bayer\" title=\"To learn more about accurate color reproduction, click here\" target=\"_blank\">To learn more about accurate color reproduction, click here<\/a>.<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>Unlike what is shown on TV, you cannot zoom into a blurry image and expect to get more details.&nbsp; An image&hellip;<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"content-type":"","_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-1931","post","type-post","status-publish","format-standard","hentry","category-uncategorized","category-1","description-off"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.3 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>OCR algorithms work better with high quality images for accurate Automated License Plate Recognition ALPR - Adimec JA<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" 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