Improvement of the optical recording system for detecting membrane potential from multiple site using CCD video camera by installing a liquid crystal panel in the light path.

研制了一种利用CCD摄像机监测膜电位的光学系统。由于膜电位变化的大小与光信号的分数变化（荧光灯变化除以静息荧光灯水平）成正比，因此静息荧光灯水平均匀一定是CCD摄像机进行光记录的理想条件。如果CCD相机每个像素的直流电平相差不大，可以从CCD相机的输出中减去恒定的直流值，然后进行放大，提高光信号中的信噪比。为此，我们尝试在光路中安装液晶面板，并独立控制每个像素的入射光水平。在2000年和2001年，我们购买了高速CCD相机，并将其帧速度匹配到每秒1000帧，更换了相机控制器，并将do电源更换为稳定的低纹波电源。2002年，我们购买了一台带有振荡刀片的切片机，并尝试用光学方法记录活体切片制备过程中的膜电位。最后发现CCD相机的饱和水平太低，无法利用吸收光信号检测膜电位。2004年，我们尝试对大鼠的大脑进行原位记录，但由于呼吸和/或心跳产生的移动伪影非常大。因此，不将光信号求和就不能记录膜电位相关的光信号。我们的CCD相机的饱和水平有时不够大，即使在钨卤灯的照射下也不能看到最亮的点。在光路中安装液晶面板可以增加入射光的强度，然后信号噪声水平似乎得到了很大改善，但噪声水平仍然不够小，无法进行单次扫描光学记录。

We have developed optical system for monitoring the membrane potential using CCD video camera. Since the size of membrane potential change is proportional to the fractional change (change in fluorescent light divided by the resting fluorescent light level) of the optical signal, it must be an ideal condition for optical recording using CCD video camera that the resting fluorescent light level is uniform. If there are not so many differences among the DC level in each CCD camera pixel, it is possible to subtract constant DC value from the output of CCD camera and then amplified for improvement the signal to noise level in optical signals. For this purpose, we have tried to install a liquid crystal panel in the light path and controlled the level of incident light in each pixel independently.In 2000 and 2001, we bought a high speed CCD camera and match its frame speed to 1000 frames per second, changed the camera controller and changed the do power supply to a stable one with very low ripple. In 2002, we bought a microtome with an oscillating blade, and tried to record the membrane potential optically from live slice preparation. Finally it was found that the saturation level of the CCD camera was too low to detect the membrane potential using absorption optical signals. In 2004, we tried in situ recording from the cerebrum of rat, but the moving artifact, which derived from the respiration and/or heartbeat, was very big. So, we cannot record the membrane potential dependent optical signal without summation of the optical signal. The saturation level of our CCD camera is sometimes not large enough for the brightest point even illuminated by a tungsten-halogen lamp. Installing a liquid crystal panel in the light path makes it possible to increase the intensity of the incident light and then the signal to noise level seems much improved, but the noise level is still not small enough for a single sweep optical recording.