Contents I. Introduction
In The microinjection process, DNA is injected into cells, and this approach represents a key technique in fields such as biology, medicine, and pharmacy, in the domains of artificial insemination and transgenics [1]. The report of the world's first transgenic mouse appeared in 1980, pertaining to the injection of a foreign gene into a pronuclear stage fertilized egg of a mouse [2]. In 1989, a knockout mouse lacking a specific endogenous gene was reported [3]. Such genetically modified animals are valuable not only to realize the functional analysis of genes but also as disease model animals to realize pathological diffraction and therapeutic drug development [4], [5]. Microinjection is often performed in an environment involving an optical microscope and electric micromanipulators. The typical process is illustrated in Fig. 1. To efficiently inject a large number of cells, the workspace is divided into three regions to avoid any confusion among the cells before and after the injection. The cells before and after the injection are placed in workspaces 1 and 3, respectively, and the injection is performed in workspace 2. Thus, each process involves the movement of the cells from workspace 1 to workspace 2, the injection process, and the movement of the cells from workspace 2 to workspace 3. A wide-area image presentation is required to efficiently move the cells from workspace 1 to 2 and from workspace 2 to 3. Moreover, the injection process in workspace 2 involves high-precision work and the observation of details such as the positions of the polar bodies and nucleus of the cells after adjusting the focal position in the depth direction through high-resolution images. At present, the wide-area image and high-resolution image are converted by manually changing and adjusting the magnification of the objective lens along with the amount of light corresponding to the objective lens. Furthermore, the focal position in the depth direction is also adjusted manually while visually checking an operation target. Consequently, the microinjection implementation requires considerable skill, and it is desirable to automate the operation and enhance the operability. To automate the operations, automatic injection systems are developed for cells such as drosophila embryos [6], mouse embryos [7], [8], zebrafish embryos [9] and adherent cells [10]. However, the cells that these automated systems can inject are limited to specific ones. In addition, it is difficult to automate the process of microinjection into human embryos owing to ethical issues.
