{"id":188,"date":"2026-04-01T14:49:27","date_gmt":"2026-04-01T05:49:27","guid":{"rendered":"https:\/\/www.san-eielectric.co.jp\/am\/?page_id=188"},"modified":"2026-04-28T12:12:37","modified_gmt":"2026-04-28T03:12:37","slug":"irradiance-non-uniformity-measurement-setup-tips","status":"publish","type":"page","link":"https:\/\/www.san-eielectric.co.jp\/am\/en\/technical-note\/irradiance-non-uniformity-measurement-setup-tips\/","title":{"rendered":"Irradiance Non-Uniformity: Measurement Setup Tips"},"content":{"rendered":"\n<ul class=\"wp-block-list\">\n<li class=\"has-medium-font-size\">Technical Note \/ Measurement Methods<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Title: Irradiance Non-Uniformity: Measurement Setup Tips<\/li>\n\n\n\n<li class=\"has-medium-font-size\">1-line summary: Common pitfalls and a simple checklist for spatial uniformity measurements.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Date: 2026-02-22<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Spectrum: General<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Level: Standard<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Category: Measurement Methods<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Related: Temporal Instability: What to Log and Why \/ (Example) Non-Uniformity Report Template<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading has-base-color has-contrast-background-color has-text-color has-background has-link-color has-large-font-size wp-elements-4540ef43c93b5f0a00661a71ae0e51b7\" style=\"padding-top:var(--wp--preset--spacing--20);padding-right:var(--wp--preset--spacing--20);padding-bottom:var(--wp--preset--spacing--20);padding-left:var(--wp--preset--spacing--20)\">1. Purpose<\/h2>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\">Irradiance non-uniformity is easy to \u201cmeasure,\u201d but also easy to measure <strong>incorrectly<\/strong> due to setup errors.<br>This note lists practical setup tips so your map reflects the <strong>simulator field<\/strong>, not artifacts from:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li class=\"has-medium-font-size\">sensor geometry,<\/li>\n\n\n\n<li class=\"has-medium-font-size\">positioning errors,<\/li>\n\n\n\n<li class=\"has-medium-font-size\">wrong working distance,<\/li>\n\n\n\n<li class=\"has-medium-font-size\">warm-up\/temporal instability during scanning.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading has-base-color has-contrast-background-color has-text-color has-background has-link-color has-large-font-size wp-elements-670cbe065435ab735bbd768849cf8133\" style=\"padding-top:var(--wp--preset--spacing--20);padding-right:var(--wp--preset--spacing--20);padding-bottom:var(--wp--preset--spacing--20);padding-left:var(--wp--preset--spacing--20)\">2. Definitions (quick)<\/h2>\n\n\n\n<h3 class=\"wp-block-heading has-contrast-color has-text-color has-link-color has-large-font-size wp-elements-8e0738e82a1dab15b1ab74d33d6c21a6\" style=\"border-width:1px;padding-top:5px;padding-right:var(--wp--preset--spacing--20);padding-bottom:5px;padding-left:var(--wp--preset--spacing--20)\">2.1 Irradiance non-uniformity<\/h3>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\">Spatial variation of irradiance across the specified test plane \/ target area.<\/p>\n\n\n\n<h3 class=\"wp-block-heading has-contrast-color has-text-color has-link-color has-large-font-size wp-elements-e3a02dd8d8c2e8d09b0665cc949ad23e\" style=\"border-width:1px;padding-top:5px;padding-right:var(--wp--preset--spacing--20);padding-bottom:5px;padding-left:var(--wp--preset--spacing--20)\">2.2 \u201cMap\u201d vs \u201csingle-point\u201d<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li class=\"has-medium-font-size\"><strong>Single-point<\/strong> reading is not enough; non-uniformity needs a defined <strong>grid<\/strong> (or scan path).<\/li>\n\n\n\n<li class=\"has-medium-font-size\">A map is only valid if the <strong>plane<\/strong>, <strong>distance<\/strong>, and <strong>aperture\/sensor condition<\/strong> are controlled.<\/li>\n<\/ul>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\">Key point: Non-uniformity depends on <strong>(a) target area<\/strong>, <strong>(b) working distance<\/strong>, <strong>(c) sensor aperture and cosine response<\/strong>, <strong>(d) stabilization condition<\/strong>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading has-base-color has-contrast-background-color has-text-color has-background has-link-color has-large-font-size wp-elements-072c72e1c4463027f1dbd97ae6c58ccd\" style=\"padding-top:var(--wp--preset--spacing--20);padding-right:var(--wp--preset--spacing--20);padding-bottom:var(--wp--preset--spacing--20);padding-left:var(--wp--preset--spacing--20)\">3. Common pitfalls (and the fix)<\/h2>\n\n\n\n<h3 class=\"wp-block-heading has-contrast-color has-text-color has-link-color has-large-font-size wp-elements-a15bad7a1569ed89c60991ce2f15c18d\" style=\"border-width:1px;padding-top:5px;padding-right:var(--wp--preset--spacing--20);padding-bottom:5px;padding-left:var(--wp--preset--spacing--20)\">3.1 Typical pitfalls<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li class=\"has-medium-font-size\">Measuring at an undefined distance (or mixing distances across runs).<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Sensor not normal to the plane \u2192 cosine error across positions.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Using a sensor head that is too large relative to the spatial gradient \u2192 \u201csmoothed\u201d map.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Scanning too slowly while the source is drifting \u2192 spatial map becomes a time-history artifact.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Not controlling cable tension \/ operator hand pressure \u2192 sensor height changes point-to-point.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">Not specifying whether the map is for <strong>irradiance<\/strong> or <strong>effective irradiance<\/strong> (band-limited).<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading has-text-align-left has-contrast-color has-text-color has-link-color has-large-font-size wp-elements-e52a4feda7f8a6558274765d7bf360e6\" style=\"border-width:1px;padding-top:5px;padding-right:var(--wp--preset--spacing--20);padding-bottom:5px;padding-left:var(--wp--preset--spacing--20)\">3.2 Fix: state these 5 setup items<\/h3>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\">Whenever you report temporal instability\/drift, state:<\/p>\n\n\n\n<ol start=\"1\" class=\"wp-block-list\">\n<li class=\"has-medium-font-size\"><strong>Target area \/ aperture:<\/strong> ______ (e.g., 150\u00d7150 mm, 200 mm dia)<\/li>\n\n\n\n<li class=\"has-medium-font-size\"><strong>Working distance (reference plane):<\/strong> ______ mm<\/li>\n\n\n\n<li class=\"has-medium-font-size\"><strong>Grid definition:<\/strong> ______ (e.g., 3\u00d73 \/ 5\u00d75 \/ step size)<\/li>\n\n\n\n<li class=\"has-medium-font-size\"><strong>Sensor condition:<\/strong> model, active area, cosine diffuser (yes\/no): ______<\/li>\n\n\n\n<li class=\"has-medium-font-size\"><strong>Temporal control:<\/strong> warm-up and drift handling (time per point \/ total scan time): ______<\/li>\n<\/ol>\n\n\n\n<h2 class=\"wp-block-heading has-base-color has-contrast-background-color has-text-color has-background has-link-color has-large-font-size wp-elements-bbfdf18e3cbce80b50757e1de3f4a0f7\" style=\"padding-top:var(--wp--preset--spacing--20);padding-right:var(--wp--preset--spacing--20);padding-bottom:var(--wp--preset--spacing--20);padding-left:var(--wp--preset--spacing--20)\">4. What to say (recommended wording examples)<\/h2>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\">A) If you report a standard non-uniformity map:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li class=\"has-medium-font-size\">\u201cIrradiance non-uniformity was evaluated on a <strong><em>\u00d7<\/em><\/strong> mm plane at ___ mm working distance using a <strong><em>\u00d7<\/em><\/strong> grid (step ___ mm). The sensor active area was ___ mm\u00b2 with cosine diffuser ___. Total scan time was ___ min after warm-up of ___ min.\u201d<\/li>\n<\/ul>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\">B) If you used a fast method (to avoid drift):<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li class=\"has-medium-font-size\">\u201cA fast grid measurement (total ___ min) was used to minimize temporal drift influence; drift during scan was monitored separately.\u201d<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading has-base-color has-contrast-background-color has-text-color has-background has-link-color has-large-font-size wp-elements-85916d525709069f20421619beae0d2e\" style=\"padding-top:var(--wp--preset--spacing--20);padding-right:var(--wp--preset--spacing--20);padding-bottom:var(--wp--preset--spacing--20);padding-left:var(--wp--preset--spacing--20)\">5. Quick checklist table<\/h2>\n\n\n\n<figure class=\"wp-block-table has-medium-font-size\"><table class=\"has-fixed-layout\"><tbody><tr><td><strong>Check<\/strong><\/td><td><strong>Why<\/strong><\/td><td><strong>Pass condition (example)<\/strong><\/td><\/tr><tr><td>Fix working distance and reference plane<\/td><td>Non-uniformity changes with distance<\/td><td>Distance recorded and repeatable<\/td><\/tr><tr><td>Keep sensor normal to plane<\/td><td>Avoid cosine error<\/td><td>Tilt &lt; ___\u00b0 (or use jig)<\/td><\/tr><tr><td>Define grid and step size<\/td><td>Makes results comparable<\/td><td>Grid stated; symmetric around center<\/td><\/tr><tr><td>Control scan time vs drift<\/td><td>Spatial map should not become time trend<\/td><td>Total scan time &lt;&lt; drift time scale<\/td><\/tr><tr><td>Confirm sensor aperture suitability<\/td><td>Avoid smoothing or aliasing<\/td><td>Active area appropriate for gradient<\/td><\/tr><tr><td>Mark center and orientation<\/td><td>Prevent map rotation errors<\/td><td>Center defined; X\/Y axes defined<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h2 class=\"wp-block-heading has-base-color has-contrast-background-color has-text-color has-background has-link-color has-large-font-size wp-elements-5be270a1627320e6c924c1e7455eff35\" style=\"padding-top:var(--wp--preset--spacing--20);padding-right:var(--wp--preset--spacing--20);padding-bottom:var(--wp--preset--spacing--20);padding-left:var(--wp--preset--spacing--20)\">6. Notes (SAN-EI recommendation)<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li class=\"has-medium-font-size\">If temporal instability is non-negligible, treat non-uniformity measurement as a <strong>two-problem system<\/strong>:<br>(1) spatial map, (2) time drift during scan.<br>Log drift at center (or a fixed point) while scanning.<\/li>\n\n\n\n<li class=\"has-medium-font-size\">If the reader may compare across systems, always include the <strong>target area and working distance<\/strong> in the summary line<\/li>\n<\/ul>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><a href=\"https:\/\/www.san-eielectric.co.jp\/am\/en\/technical-note\/\" data-type=\"page\" data-id=\"181\"><\/a><a href=\"https:\/\/www.san-eielectric.co.jp\/am\/en\/technical-note\/\" data-type=\"page\" data-id=\"181\">Return to INDEX<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>1. Purpose Irradiance non-uniformity is easy to \u201cmeasure,\u201d but also easy to measure incorrectly due to setup e [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":181,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-188","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.san-eielectric.co.jp\/am\/wp-json\/wp\/v2\/pages\/188","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.san-eielectric.co.jp\/am\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.san-eielectric.co.jp\/am\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.san-eielectric.co.jp\/am\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.san-eielectric.co.jp\/am\/wp-json\/wp\/v2\/comments?post=188"}],"version-history":[{"count":7,"href":"https:\/\/www.san-eielectric.co.jp\/am\/wp-json\/wp\/v2\/pages\/188\/revisions"}],"predecessor-version":[{"id":1038,"href":"https:\/\/www.san-eielectric.co.jp\/am\/wp-json\/wp\/v2\/pages\/188\/revisions\/1038"}],"up":[{"embeddable":true,"href":"https:\/\/www.san-eielectric.co.jp\/am\/wp-json\/wp\/v2\/pages\/181"}],"wp:attachment":[{"href":"https:\/\/www.san-eielectric.co.jp\/am\/wp-json\/wp\/v2\/media?parent=188"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}