超高灵敏极弱磁场探测已被广泛应用于生物磁测量，为研究生物体运行机理和病理分析提供了强有力的工具。基于超导量子干涉器件（SQUIDs）的磁强计是目前临床生物磁测量的主流选择，但昂贵的设备和维护成本影响了其大范围应用。随着光泵浦原子极化等技术的发展，基于无自旋交换弛豫（SERF）的光泵原子磁强计，达到与SQUIDs磁强计相当的灵敏度，成为生物弱磁检测技术的研究热点。本文面向低成本生物弱磁测量及成像应用，研究高灵敏度SERF原子磁强计的小型化设计、多通道磁成像系统架构、及其在心磁检测和成像中的应用。论文针对低成本心脑磁成像应用，提出并实现了单光束单通和单光束双通两种构型的小型化光纤式SERF原子磁强计。通过基于Bloch方程的SERF原子磁强计理论建模仿真与实验测试，研究了泵浦光功率等关键因素对零场共振信号线宽与信噪比的影响，实现了磁强计性能的优化。磁强计标定与测试结果表明：实现的小型化光纤式SERF原子磁强计，在单光束单通和双通构型下测磁灵敏度分别达到了85 fT/Hz^{1/2}和84 fT/Hz^{1/2}（10 Hz频率处）。提出并实现的基于光纤环形器的单光束双通构型，与同等条件下的单光束单通构型相比，检测零场共振线宽更窄。磁噪声定量评估结果表明，磁强计灵敏度的主要噪声限制因素为光检测系统噪声。论文进行了小型化光纤式SERF原子磁强计的闭环控制方法研究，基于磁强计探头内部线圈的磁场补偿与基于FPGA的PID控制实现了磁强计的闭环锁定。实现结果表明，小型化光纤式SERF原子磁强计闭环模式下，相对其开环模式，带宽从92 Hz提高到308 Hz，测量范围从±2.5 nT提高到±300 nT，线性度明显提升。论文提出了基于小型化光纤式SERF原子磁强计的多通道磁成像系统架构，设计并实现了四通道原子磁强计系统。梯度差分模式下工作的原子磁强计，与单通道原子磁强计相比，本底噪声幅度显著降低，测磁灵敏度提高近一倍（47 fT/Hz^{1/2}@10 Hz），具有良好的共模噪声抑制能力。基于小型化光纤式SERF原子磁强计，进行了成人心磁信号检测及扫描式磁成像的研究。首先，采用梯度线圈产生的梯度磁场进行了扫描磁成像的标定，梯度磁场常数的测量结果与理论计算结果偏差小于1%；其次，在采用EEMD降噪算法对心磁信号进行处理的基础上，进行了成人心磁信号测量和扫描式成人心磁成像的对比实验，测试结果验证了小型化光纤式SERF原子磁强计在心磁测量和成像上的可用性。

Ultra-high-sensitivity detection of extremely weak magnetic fields has been widely applied in biomagnetic measurement, providing a powerful detection tool for the operational mechanisms and pathological analysis of organisms. As a mainstream choice for current clinical biomagnetic measurement, the magnetometer based on superconducting quantum interference devices (SQUIDs) is difficult to expand its applications due to its expensive equipment and maintenance cost. With the development of techniques such as optically pumped atomic polarization, the spin-exchange relaxation-free (SERF) atomic magnetometer reaches a comparable sensitivity to SQUIDs, and becomes a research focus in the field of biomagnetic detection. This thesis studies on the miniaturized design of a high-sensitivity SERF atomic magnetometer, multi-channel magnetic imaging system architecture, and their applications in magnetocardiographic measurement, for low-cost biomagnetic measurements and imaging applications.For low-cost magnetocardiographic and magnetoencephalographic applications, this thesis proposes and implements two configurations of miniaturized fiber-coupled SERF atomic magnetometers: single-beam single-pass and single-beam double-pass. With theoretical modeling and simulation based on the Bloch equation and experimental test of the SERF atomic magnetometers, we studied effects of different factors including pumping laser power on the zero-field resonance signal linewidth and signal-to-noise ratio, for optimizing the magnetometer performance. Calibration and experimental results of the magnetometers show that the miniaturized fiber-coupled SERF atomic magnetometers achieve sensitivities of approximately 85 fT/Hz^{1/2} and 84 fT/Hz^{1/2} (at 10 Hz) in the single-beam single-pass and single-beam double-pass configurations, respectively. The proposed configuration of single-beam double-pass using optical fiber circulator shows a narrower linewidth of the zero-field resonance, compared with the single-beam single-pass configuration under the same conditions. Quantitative evaluation of magnetic noises shows that the main limiting factor for magnetometer sensitivity is the noise of the optical detection system.The thesis investigates the closed-loop control method for a miniaturized fiber-coupled SERF atomic magnetometer. By utilizing magnetic field compensation by internal coils inside the sensor and FPGA-based PID control, the magnetometer achieves closed-loop locking. The results demonstrate that the SERF atomic magnetometer in closed-loop mode, achieves an increased bandwidth from 92 Hz to 308 Hz, an extended measurement range from ±2.5nT to ±300nT, and significantly improved linearity, compared to its open-loop mode.The thesis proposes a multi-channel imaging system architecture based on the miniaturized fiber-coupled SERF atomic magnetometer and designs a four-channel atomic magnetometer system. The atomic magnetometer operating in gradient difference mode demonstrates excellent common-mode noise suppression capability, with significantly reduced background noise and nearly doubled magnetic field sensitivity (47 fT/Hz^{1/2} at 10 Hz), compared with those of the single-channel atomic magnetometer. Utilizing the miniaturized fiber-coupled SERF atomic magnetometer, adult magnetocardiographic signals are measured and corresponding magnetocardiography is achieved in a scanned mode. Firstly, the scanned imaging method of magnetic fied is calibrated by using a gradient magnetic field with gradient coils. The experimental result shows a measurement deviation of less than 1% in terms of the gradient field constant, compared with the theoretically calculated result. Secondly, on the basis of the EEMD denoising algorithm, comparative experiments are conducted for detecting adult magnetocardiographic signals and scanned magnetocardiography. The results validate the usability of the miniaturized fiber-coupled SERF atomic magnetometer in magnetocardiographic measurement and imaging applications.