Erratum to “Frequency-dependent gradient error suppression method for optically pumped magnetic gradiometers”. [Measurement 256 Part A (2025) 118138] (Measurement (2025) 256(PA), (S0263224125014976), (10.1016/j.measurement.2025.118138))

The publisher regrets to inform readers that Figures 1–8 in the article “Frequency-dependent gradient error suppression method for optically pumped magnetic gradiometers” were incorrectly inserted due to a typesetting error. Revised figures are included in this Errata.[Figure presented] Fig. 1. Phase-frequency response of OPMs with different bandwidths. The two curves do not intersect at B_z=0. The channel with the narrower bandwidth exhibits a greater phase delay. Additionally, when B_z is present in the narrow bandwidth channel, the phase difference between the two channels decreases. The asterisk shows the intersection point.[Figure presented] Fig. 2. The influence of on the response phase and residual gradient response. (a) The effect of on the rate of change of the response phase of the OPM sensitive axis as a function of signal frequency. (b) The residual gradient response as a function of signal frequency for different B_z values applied to a channel with a lower relaxation rate (simulation conditions: Δf_b=15 Hz).[Figure presented] Fig. 3. Schematic of the experimental setup. The two OPMs constitute a first-order synthetic gradiometer with a baseline of 2 cm, and each OPM has a volume of less than 10 cm³. TIA: transimpedance amplifier, LIA: lock-in amplifier, DAQ: data acquisition device, TC: temperature control device, C: collimator, LP: linear polarizer, PD: photodetector.[Figure presented] Fig. 4. The influence of bandwidth difference on the accuracy of gradient measurement. (a) Time-domain signals of single-channel and gradient results under different Δf_b. (b) Variation of the residual gradient response with signal frequency under different Δf_b. As Δf_b decreases, the residual gradient response caused by the response phase difference also diminishes.[Figure presented] Fig. 5. Variation of CMRR with signal frequency at a fixed Δf_b=20 Hz under different B_z.[Figure presented] Fig. 6. Variation of CMRR with signal frequency at a fixed Δf_b=4 Hz under different B_z.[Figure presented] Fig. 7. Average and best CMRR in 1–50 Hz frequency band under different B_z.[Figure presented] Fig. 8. The single-channel and gradient sensitivities. The blue and red lines show the gradient sensitivity differences before and after applying the proposed method. The enlarged inset clearly shows the CMRR and noise spectrum improvements. The publisher would like to apologise for any inconvenience caused.