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.

我们研制了利用CCD摄像机对膜电位进行监测的光学系统。由于膜电位变化的大小与光信号的分数变化(荧光光的变化除以静止的荧光光级)成正比，因此使用CCD摄像机进行光学记录的理想条件是静止的荧光光级是均匀的。如果每个CCD摄像机像素的直流电平之间没有太大的差异，就可以从CCD摄像机的输出中减去恒定的DC值，然后进行放大，以提高光信号的信噪比。为此，我们尝试在光路中安装液晶面板，独立控制每个像素的入射光强。2000年和2001年，我们购买了一台高速CCD摄像头，将其帧速度匹配到1000帧/秒，更换了摄像头控制器，并将DO电源改为非常低纹波的稳定电源。2002年，我们购买了一台带摆动刀片的切片机，并试图通过光学记录活体切片制备的膜电位。最后发现，利用吸收光信号检测膜电位时，CCD摄像机的饱和电平太低。2004年，我们尝试了大鼠大脑的原位记录，但呼吸和/或心跳产生的运动伪影非常大。因此，如果没有光信号的求和，我们就不能记录依赖于膜电位的光信号。我们的ccd相机的饱和度有时不够大，即使用卤钨灯照明也不足以照亮最亮的点。在光路中安装液晶面板可以增加入射光的强度，然后信噪比似乎有很大改善，但噪声水平仍然不够小，不足以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.