In　response　to　the　problems　of　the　existing　partition　toning　technology　based　on　liquid　crystal　backlight　needs　to　add　metal　physical　grilles　with　high　alignment　accuracy　to　prevent　the　crosstalk　of　different　colors　and　brightnesses　of　light　between　the　partitions,　this　paper　proposes　a　structural　design　of　the　optical　cavity　without　grille　and　its　key　parameter　value　intervals,　and　puts　forward　a　low-color　crosstalk　evaluation　method.　Based　on　this　method,　the　light　output　effect　of　the　diffuser　is　evaluated,　and　the　distance　between　the　diffuser　and　the　RGB　mini-LED　light　source　as　well　as　the　structural　parameters　of　the　light-guiding　cavity　between　them　are　reasonably　adjusted.　The　grille-less　optical　cavity　structure　studied　in　this　paper　has　the　advantages　of　simple　structure,　low　cost　and　easy　implementation,　ensuring　regional　dimming　and　regional　color　mixing　while　further　improving　the　color　crosstalk　phenomenon　between　the　backlight　partitions.　©　2024　John　Wiley　and　Sons　Inc.　All　rights　reserved.