JPH03160330A - Photon counting type optical waveform observation apparatus - Google Patents

Abstract

PURPOSE:To realize the original time resolving power of a streak tube by counting up the data of the position of the bright point due to a single photoelectron detected from a streak image and the measurement is repeated to integrate the data. CONSTITUTION:The streak image due to a photon conducting type streak camera 30 is taken by a TV camera 32 and the video signal thereof is converted to a digital signal by an A/D converter to be stored in an image memory 36. A CPU 42 detects the position of each bright point due to the single photoelectron of the streak image and said position is integrated by an SPC memory 38 or an SPC waveform memory 39. The detection and the integration are repeatedly performed to obtain a photon counting type streak image. When data is integrated along the direction crossing a time axis (t) at a right angle and the time axis (t) with respect to a part of this image, the waveform related to desired intensity distribution is obtained.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an optical waveform observation device using a photon-counting streak camera, and in particular, a photon-counting optical waveform 1 that can realize the FR resolution inherent to a streak tube! It is related to measuring equipment.

[Prior Art I] A streak camera is known as a device that measures changes in temporal light intensity distribution such as light emission phenomena that change at high speed. As shown in the basic configuration of FIG. 8, this streak camera converts incident light into electrons by applying it to a photocathode 16 of a streak tube 14 through an input optical system consisting of, for example, a slit plate 10 and a lens 12. By sweeping photoelectrons at high speed when they pass between the deflection electrodes 18, the time-varying incident light intensity is measured as a change in brightness at a position on the fluorescent surface 22. In the figure, 20 is
This is a microchannel plate (MCP) for multiplying photoelectrons immediately in front of the fluorescent surface 22. The streak tube 14 used in this streak camera is an electron tube in which a deflection electrode 18 is arranged between a photocathode 16 and a fluorescent surface 22. When light to be measured is made incident on the photocathode 16 of the streak tube 14, The photocathode 16 sequentially emits photoelectrons in response to changes in incident light over time, forming a photoelectron beam that changes over time. When this photoelectron beam moves in the streak tube 14, when an electric field is applied to the deflection N pole 18, the photoelectron beam is directed in one direction on the fluorescent surface 22 (from the top to the bottom in FIG. 8). was dragged by
A change in the intensity of the incident light appears as a change in brightness in the sweep direction of the photoelectron beam on the fluorescent surface 22 (in the time axis direction). The image that appears on the output fluorescent surface 22 in this way is called a streak image, and after capturing it with a television camera, the brightness distribution of this output image along the time axis direction is quantified. , it is possible to know the change over time in the intensity of the light to be measured. Streak cameras are broadly classified into single sweep type and synchro scan type based on their operating principle and sweep method. The single-sweep type performs a straight-line sweep using an ultrahigh-speed sawtooth wave that repeats at a frequency of approximately several kHz or less, and is used to observe a single light emission phenomenon. Furthermore, the synchronous scan type performs high-speed repetitive sweeping using a sine wave, and is used to observe repetitive light emission phenomena superimposed on a fluorescent surface by sweeping in synchronization with the light emission. Furthermore, as shown in FIG. 9, in addition to the deflection electrodes 18, another set of deflection electrodes (referred to as shift electrodes to distinguish them from the deflection electrodes) 24 are arranged in a direction perpendicular to the deflection electrodes 18. Heavy sweep streak cameras are also known. In this double streak camera, the deflection electrode 1
8 is applied with an electric field in the same manner as described above to obtain a streak image of one luminescent phenomenon on the fluorescent surface, but the electric field is applied to the shift electrode 24 more slowly than on the deflection electrode 18. As a result, the light to be measured is made to enter the photocathode of the streak tube one after another, an electric field is applied to the deflection electrode 18 in accordance with the incidence of each light to be measured, and a slow electric field change is applied to the shift electrode 24. As a result, streak images of the respective measured light beams are two-dimensionally obtained on the output fluorescent surface, lining up in a direction perpendicular to the time axis. Furthermore, a photon-counting streak camera is used when the light to be measured is so weak that only a few to several tens of photoelectrons are emitted from the photocathode upon one incident of the light to be measured. The streak tube used in this photon-counting streak camera includes, in front of the fluorescent surface 22 of the streak tube 14,
As shown in FIG. 10, two MCP2OA and 20B are arranged, thereby increasing the gain of the streak tube. As a result, a streak image is obtained in which each photoelectron appears as a bright bright spot on the fluorescent surface. This streak image is read out by a television camera, converted to a digital signal, and then stored in a digital memory.
Also, a plurality of streak images are added together within the digital memory. Therefore, by adding data for a portion of the streak image stored in the digital memory in a direction orthogonal to the time axis, a waveform of temporal light intensity changes can be obtained. (Problem to be achieved by the invention 1 However, the photoelectrons emitted from the photoelectric
As shown in the figure, it is multiplied by the first MCP2OA,
It enters the second MCP 20B in an expanded state. As shown in FIG. 11, the photoelectrons incident on the second MCP2OB are further multiplied by the second MCP2OB, and then further expanded and output. Therefore, a single photoelectron has a non-negligible spread on the fluorescent surface. Therefore,
The waveform of the M-interval light intensity change becomes a waveform that is distorted with respect to the time axis by the amount of expansion, resulting in deterioration of temporal resolution. For example, the time resolution of the streak tube is 2 ps at half width.
, assuming that the time-converted value of the photoelectron spread is also 5 ps in half width, and each spread is a Gaussian distribution, the obtained inter-FR resolution is ( 2 2 + 5
2)! /'2←5. 1S, and the time resolution (2 ps) inherent to the streak tube could not be obtained. The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a photon counting type optical waveform observation device that can realize the time resolution inherent to a streak tube. (Means for Achieving the Object) The present invention provides a photon counting type optical waveform observation device, which includes a photon counting type streak camera, a television camera for capturing a streak image obtained by the streak camera, and an IllI image obtained by the television camera. Detected from the blurred streak image,
A photon counting memory for counting up data on the position of a bright spot caused by a single photoelectron, and means for repeatedly performing these measurements and integrating the data on the photon counting memory to obtain a photon counting streak image. By providing
The above-mentioned problem has been achieved. Further, the position of the bright spot by the single photoelectron is detected by detecting the peak position of a streak image. Further, the position of the bright spot by the single photoelectron is detected by determining the value of the first moment within a predetermined range including the approximate position of the bright spot as the position of the bright spot. Further, in detecting the position of the bright spot using the single photoelectron, the streak image is binarized at a predetermined threshold level, and the value of the first moment of each bright area of the binary image is set as the position of the bright spot. This is done by doing this. In addition, in the photon counting type optical waveform observation device, a photon counting type streak camera, a television camera for capturing a streak image obtained by the streak camera, and a portion of the streak image imaged by the television camera are used. means for obtaining a time-versus-light-intensity waveform by integrating in a direction perpendicular to the time axis, a photon-counting waveform memory for counting up data on the position of a bright spot detected from the light-intensity waveform, and a waveform memory for counting these points. The above-mentioned object is also achieved by providing means for repeatedly performing the above steps and integrating the data on the photon counting waveform memory to obtain the temporal intensity distribution of the optical phenomenon.

[Operation and Effect 1] In the present invention, a streak image obtained by a photon counting streak camera is captured by a television camera, the position of a bright spot caused by a single photoelectron is detected from the captured streak image, and photon counting is performed. By counting up the data at the same location in the memory and repeating these measurements,
Data is accumulated on a photon counting memory to obtain a photon counting streak image. Therefore, since the position of a bright spot caused by a single photoelectron can be accurately detected and integrated, there is no deterioration in resolution caused by the spread of the output image of the MOP, and it is possible to obtain the original temporal resolution of a streak tube. can. Also, since it is essentially a photon counting method,
Compared to the conventional example, deterioration in S/N due to multiplication fluctuations in MCP etc. is also eliminated. Therefore, observation of extremely weak optical phenomena, such as the observation of luminescence from living organisms, can be performed with high temporal resolution and S/N.
can do well. Furthermore, when the position of the bright spot by the single photoelectron is detected by detecting the peak position of a streak image, the position of the bright spot can be easily detected. Further, when detecting the position of the bright spot using the single photoelectron by setting the value of the first moment within a predetermined range including the approximate position of the bright spot as the position of the bright spot, Position can be determined accurately. Further, in detecting the position of the bright spot using the single photoelectron, the streak image is binarized at a predetermined threshold level, and the value of the first moment of each bright area of the binary image is set as the position of the bright spot. In this case, the position of the bright spot can be accurately detected without being affected by noise. In addition, a streak image obtained with a photon-counting streak camera is imaged with a television camera, and a part of the imaged streak image is integrated in a direction perpendicular to the time axis of the streak image to obtain a time versus light intensity waveform. , detecting the position of a bright spot in the light intensity waveform, counting up data at the same position in the photon counting waveform memory, and repeating these measurements to accumulate data on the photon counting waveform memory. hand,
When obtaining the temporal intensity distribution of a light phenomenon, the temporal intensity distribution of a weak light phenomenon can be obtained using high temporal resolution and S
/N. Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, this embodiment includes a photon-counting streak camera 30, a television (TV) camera 32 that images the streak image obtained by the streak camera 30, and
An analog/digital (A/D) converter 34 that converts the video signal obtained by the camera 32 into a digital signal, and an image memory 36 that stores the digitized video signal.
, a photon counting (SPC) memory 38 or SPC waveform memory 40 for counting up data on the position of a bright spot due to a single photoelectron detected from the streak image stored in the image memory 36, and a memory for measuring these. is repeated, and the SPC memory 38 or SPC waveform memory 4 is
It is mainly composed of a microprocessor (CPU) 42 for integrating data on 0 and obtaining a photon counting streak image. The streak camera 30 is swept by a trigger circuit 28 which is activated by an external signal. This streak camera 30 includes the TV camera 32,
They are coupled by a lens 31 or a fiber plate. The effects of the embodiment will be explained below. The streak image obtained by the streak camera 30 is
An image is taken by a camera 32, and the video signal is A/D converted by an A/D converter 34, and then stored in an image memory 36, which is a digital memory. Incidentally, instead of the TV camera 32, a cooled CCD camera can be used to expose the streak image for a certain period of time, and after exposing a plurality of streak images, the signal can be read out from the COD and stored in the image memory 36. An example of the streak image stored in this manner is shown in FIG. In FIG. 2, the black dots are bright spots caused by single photoelectrons. A spectroscope is placed in front of the streak camera 30, and the output image of the spectrometer is transmitted to the streak camera 30.
, the axis perpendicular to the time axis of the obtained streak image becomes the wavelength axis. The CPU 42 performs photon counting integration on the streak image shown in FIG. 2 according to the following procedure. Here, photon counting integration refers to constructing an image or waveform by detecting one single photoelectron (1 MJ) and counting the number of photoelectrons. Step 1: Detect the position of each bright spot caused by a single photoelectron in the streak image, and add 1 to the same position in the SPC memory 38 or SPC waveform memory 40. The position of the bright spot can be detected, for example, by any of the following methods. (1> Detect all local peaks in the streak image, and if the value of the detected peak is larger than a predetermined value, that position is determined as the position of the bright spot. (2) Third As shown in the figure, in the streak image,
First, find the approximate position of the bright spot using the method (1), and then
Let the value C of the next moment be the position of the bright spot. (3> As shown in Figure 4, the streak image (Figure 4 (A)
), extract all the parts with values greater than a certain value (Fig. 4 (B)), and set the value of the first moment obtained for each part of the group as the position of the bright spot (Fig. 4 (B)). Figure 4 (C
〉). 4〉As shown in Figure 5, the streak image (Figure 5 (A)
) is binarized using a certain determined value as a threshold (Fig. 5 (B)), and the value of the first moment of each bright region of the binary image is set as the position of each bright spot (Fig. 5 (B)). (C)). The position of each bright spot determined in step 1, that is, the position of a single photoelectron image, is integrated and held in the SPC memory 38. Step 2: Measure the streak image and repeat step 1 several times to accumulate the data on the SPC memory 38 to obtain the streak image shown in FIG. 6 (A). If we integrate the data in the direction perpendicular to the time axis for a certain part, we can see the temporal change in light intensity (at a specific wavelength if the horizontal axis is the wavelength axis), as shown in Figure 6 (B). On the other hand, if the data is integrated along the time axis, the waveform of the spatial light intensity change at a specific time (if the horizontal axis is the wavelength), as shown in Figure 6(C), As shown in Fig. 7, in step 1, the waveform (temporal light intensity waveform or spectrum) is first extracted using the same method as in step 2 for the streak image shown in Fig. 2. Then, the bright spot position of the waveform is detected using the same method as in steps 1 to 4 of step 1. And SP
By adding 1 to the same position in the C waveform memory 40 and repeatedly measuring the streak image and detecting this position, the sixth
Waveforms equivalent to those shown in FIGS. (B) and (C) can also be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of a photon-counting optical waveform observation device according to the present invention; FIG. 2 is a diagram showing an example of a streak image obtained by the embodiment; The figure is a miniature diagram showing an example of the method of detecting the bright spot position from the streak image shown in Fig. 2, Fig. 4 is a line diagram showing another example, and Fig. 5 is a diagram showing still another example. 6 is a diagram showing an example of a streak image obtained on the SPC memory according to this embodiment and an example of its integral waveform. FIG. 7 is a diagram showing a streak image as shown in FIG. 2 above. A diagram showing an example of a waveform obtained by first integrating 10 and 11 are diagrams for explaining the spread of photoelectrons in a photon counting streak camera. 30... Photon counting streak camera, 32... Television (TV) camera, 36... Image memory, 38... Photon counting (SPC) memory, 40... Photon counting (SPC) waveform Memory, 42... Microprocessor (CPU).

Claims (5)

[Claims] (1) A photon-counting streak camera, a television camera that captures the streak image obtained by the streak camera, and data on the position of a bright spot caused by a single photoelectron detected from the streak image captured by the television camera. A photon counting device comprising: a photon counting memory for counting up; and means for repeatedly performing these measurements and integrating data on the photon counting memory to obtain a photon counting streak image. type optical waveform observation device. (2) The photon counting type optical waveform observation device according to claim 1, wherein the position detection of the bright spot by the single photoelectron is performed by detecting the peak position of a streak image. . (3) In the photon-counting optical waveform observation device according to claim 1, the position detection of the bright spot by the single photoelectron is performed by detecting the value of the first moment within a predetermined range including the approximate position of the bright spot. A photon counting type optical waveform observation device characterized in that it performs observation by determining the position of a point. (4) In the photon-counting optical waveform observation device according to claim 1, the position detection of the bright spot by the single photoelectron is performed by binarizing the streak image at a predetermined threshold level, and converting the streak image into a binary image at a predetermined threshold level. A photon counting type optical waveform observation device characterized in that the measurement is carried out by setting the value of the first moment of each bright region as the position of the bright spot. (5) a photon-counting streak camera; a television camera that captures a streak image obtained by the streak camera; and a portion of the streak image captured by the television camera in a direction perpendicular to the time axis of the streak image. means for integrating to obtain a light intensity waveform versus time; a photon counting waveform memory for counting up data on the position of a bright spot detected from the light intensity waveform; A photon-counting optical waveform observation device comprising: means for integrating data on a waveform memory for obtaining a temporal intensity distribution of an optical phenomenon;