This paper is about the development of a PO - a mobile device for direct examination of the eye fundus, in which a shifting mirror, a lens unit, a photo sensor, a microprocessor and an interface part are added to the currently known ophthalmoscope for direct ophthalmoscopy. The device can work in such modes as the mode of ophthalmoscopy, when the optical circuit of the device fully corresponds to the scheme of the traditional ophthalmoscope and in the mode of photo fixation, when the sliding mirror briefly blocks the main optical axis of the device, directing the rays reflected from the investigated eye fundus not to the eye of the researcher, but to the photosensor. This makes possible to make a photograph of the observed picture of the fundus. The device provides for the possibility of adjusting the optical scheme of photographic fixation to the clinical refraction of the researcher so that the routine use of the device as little as possible differs from the use of a traditional manual ophthalmoscope. In addition, in the hardware and software complex of the photo-ophthalmoscope (PO), the functions of storing and transmitting the received information are provided, as well as a software interface for integrating the device into the local network of the medical institution. There provided the detailed information on the development of a general scheme of the device, on the development of a diagram of the optical part of the instrument, and on the development of the structure of the integrated software for the PO.
2]. To use this method, various models of hand-held mobile ophthalmoscopes are
currently being mass-produced [
The known types of handheld mobile photo-ophthalmoscopes (PO) proposed in the
world literature [
So, the overall goal of this work is to realize the possibility of automatic documentary photographic recording of the results of a study performed with the help of a hand-held mobile ophthalmoscope.
This goal is achieved by adding to the ophthalmoscope optical, electromechanical and electronic components, which are the hardware base of the software, which makes it possible to photograph the visible picture of the fundus. 2
At the first stage of the work, a synthesis of the graphical representation of the general
structure of the hardware-software complex of the PO in the form shown in Fig. 1 [
In Fig. 1, the central processor (CPU) is the main component of the device. When user press the button switches on the IO device (IO Dev), the processor performs the actions specified by the firmware of the device. It controls the position of the mirror (EM Mirr) and brightness of fundus illuminator (Illum) in accordance with the userselected operating mode of the device (ophthalmoscopy or fundus photo). In photographic mode CPU receives information from CCD sensor (PM), process it, store it in the EEPROM memory and transfer for further processing on a PC over a wired (USB) or a wireless (BT) interface channels. Also, the processor through the power controller (PCont) monitors the level of the battery's charge and gives a lowcharge warning signal to the indicator on IO device. 3
The structure of the optical scheme of the PO, which combines both the possibility of direct observation and the fixation of the image, can be represented as follows (Fig. 2).
It is proposed to use the Tessar scheme [
The CCD matrix [
The general block diagram of the firmware of the device is shown in Fig. 3.
Based on the created block diagram describing the algorithm of the manual PO, the
main structural elements of this scheme were analyzed [
Functions of the built-in software: initialization at power-on; IO sensors polling;
processing operator actions (drives of electromechanical nodes of the
photoophthalmoscope; Automation of the process of transmission of received images);
Safely turn off the device.
turned on is shown in the graph (Fig. 4):
optimized by the method of block-functional distributions (i-initialization mode) [
The first step is to check the status of the sliding mirror. To continue to work with the device, the software must check the position of the sliding mirror. This mechanism provides 2 states, which corresponds to the on and off states of mirror position sensors. It is supposed to use 2 contact sensors, when triggered, the processor will stop supplying power to the electromagnet in order to stop the movement of the mirror. Proceeding from this, we get two working positions of the mirror: 1) Mirror is down – the starting point; 2) The mirror is raised and is at the end point. 4.3
The keypad polling procedure is the main control procedure of the processor. After the main control program is switched on and loaded, the device goes into the button response mode. The structure of this section of the program is presented on the graph (Fig. 5).
The device constantly polls the buttons, waiting to receive a response at any time. The frequency of polling buttons will be determined by the frequency of the used processor. The graph (Fig. 6) shows the structure of the algorithm describing the process of controlling the survey.
After pressing the "Shot" button, voltage is applied to the electromagnet, which moves the mirror. The time for raising the mirror will vary from 0.2 to 0.6 seconds. Such a time interval may depend on the level of charge of the battery, and hence on the voltage output from it. So, because of the lowering of the voltage level received from the battery in 20% of the rated value, the time of the mirror rise can increase by 0.5 seconds.
After lifting the mirror, the device goes directly to the image capture procedure.
1. The initial adjustment values for a particular CCD sensor are loaded.
2. The processor needs to assess the average light level of the CCD sensor.
3. Next, it`s need to evaluate the exposure values. We expect to set the shutter speed
in the range from 0.15 to 0.35 seconds. This time will be enough for the camera
exposure in the operating conditions of our device.
4. At the next stage, the necessary level of increase in the power of the illuminator is
calculated to balance the lack of illumination level of the room. However, the power
is calculated only if the level of illumination is not sufficient.
5. The received parameters are saved, and the system switches to the mode of reading
the illumination values from the CCD sensor x.
6. And further, proceeding from the illumination of the environment, the program
increases the power of the illuminator to the calculated value, if necessary.
7. The procedure for exhibiting the matrix begins.
8 ... 9. After the shutter is closed, the power of the illuminator is reduced to the initial
value.
10. After the shutter is closed, the information is read from the matrix into the
operative memory of the device.
11. Next, the image is converted to a color image.
12. After converting the original image from the matrix to a color one, the white
balance correction is performed.
13. Ultimately, the image is converted to the format we selected. In our case, the
JPEG format is sufficient and optimal for us [
Thus, a synthesis of the general structure, the optical part and the integrated software of the mobile photo-ophthalmoscope-the original device that combines all the functions of traditional ophthalmoscopes for direct ophthalmoscopy with the functions of photographic fixation of the user's observed eye-fund picture was performed. 5