  In the context of safe exploration, Reinforcement Learning (RL) has long
grappled with the challenges of balancing the tradeoff between maximizing
rewards and minimizing safety violations, particularly in complex environments
with contact-rich or non-smooth dynamics, and when dealing with
high-dimensional pixel observations. Furthermore, incorporating state-wise
safety constraints in the exploration and learning process, where the agent
must avoid unsafe regions without prior knowledge, adds another layer of
complexity. In this paper, we propose a novel pixel-observation safe RL
algorithm that efficiently encodes state-wise safety constraints with unknown
hazard regions through a newly introduced latent barrier-like function learning
mechanism. As a joint learning framework, our approach begins by constructing a
latent dynamics model with low-dimensional latent spaces derived from pixel
observations. We then build and learn a latent barrier-like function on top of
the latent dynamics and conduct policy optimization simultaneously, thereby
improving both safety and the total expected return. Experimental evaluations
on the safety-gym benchmark suite demonstrate that our proposed method
significantly reduces safety violations throughout the training process, and
demonstrates faster safety convergence compared to existing methods while
achieving competitive results in reward return.
