As　products　evolve　towards　greater　precision　and　intelligence,　their　components　also　develop　towards　miniaturisation　and　increasing　complexity.　In　the　era　of　intelligence,　the　demand　for　complex　small　components　continues　to　grow.　The　point-autofocus　microscopy　(PAM),　with　its　attributes　such　as　small　measurement　spots　and　high　vertical　resolution,　holds　a　comprehensive　advantage　in　instruments　for　measuring　the　geometry　of　complex　small　components.　The　performance　of　the　spot　positioning　sensor　directly　determines　the　capability　of　the　PAM　to　measure　complex　small　components.　This　study　introduces　the　basic　measurement　principles　of　the　PAM　and　commonly　used　spot　positioning　sensors.　The　analysis　explored　the　feasibility　of　applying　different　sensors　to　the　PAM.　An　automatic　segmentation　and　weighted　localisation　algorithm　of　the　spot　based　on　the　centroid　method　was　proposed.　Using　this　algorithm,　the　spot　positioning　error　of　the　complementary　metal–oxide–semiconductor　(CMOS)　sensor　can　be　controlled　within　0.48　μm,　with　a　measurement　uncertainty　of　no　more　than　±0.19　μm.　This　study　focuses　on　comparing　the　performance　of　CMOS　and　position-sensitive　detector　sensors　with　the　performance　of　seven　indicators.　In　addition,　a　measurement　system　of　the　PAM　was　constructed,　and　measurements　of　the　test　object　were　conducted　using　both　types　of　sensors.　The　experimental　results　show　that　when　the　measurement　system　employs　the　CMOS　sensor,　it　achieves　higher　measurement　accuracy.　The　maximum　measurement　error　was　approximately　0.22　μm,　with　a　measurement　uncertainty　of　no　more　than　±0.10　μm.　©　2024　Elsevier　Ltd