JPH049760Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field] This invention relates to a fluoroscopic device for viewing images recorded on a film surface, and more specifically, the invention relates to a fluoroscopic device for viewing images recorded on a film surface. The present invention relates to a fluoroscopic device that is lit by a constant current power source.

[Prior art and problems] Conventional fluoroscopic devices that have been generally known include, for example, placing a fluoroscopic film on a frosted or white glass plate and lighting a discharge lamp such as a fluorescent lamp from the back of the glass plate. Usually, multiple discharge lamps are installed to reduce uneven lighting.

In this case, there is no particular problem if the device is simply used to visually judge the image content of the film, but
For example, in a device used in a so-called digitizer, which combines an electromagnetic induction tablet with a probe that traces the film surface, and extracts position information from an image and inputs it into a computer,
Since the discharge lamp is interposed on the back side of the glass plate, the distance between the film surface and the tablet becomes large, making it difficult to obtain highly accurate position information.

For this reason, the present applicant previously proposed in Utility Application No. 59-084845 the idea of a thin fluoroscopic device with almost no uneven illumination, in which a digitizer can be placed close to the surface of the fluoroscopic film. . The outline can be briefly explained using Figures 5 and 6.
This device main body 1 includes, for example, two upper and lower frames 2,
3 are combined into a box shape, and the upper frame 2
A window 4 is provided in the center of the screen, and a translucent glass plate 5 for viewing is attached to the window 4.

In addition, the lower frame 3 has grooves 6, 6 bent in a U-shape, for example, at both left and right ends,
Reflection plates 7, 7 each having a semicircular cross section are attached to the grooves 6, 6, and discharge lamps 8, 9 are attached to the inner sides of the reflection plates 7, 7 via sockets (not shown) or the like. The light from the discharge lamps 8 and 9 illuminates the glass plate 5.
glass plate 5 to ensure uniform illumination.
For example, a light guide plate 10 and a reflection plate 11 are provided directly below the main body 1, and a drive unit 14 having a power cord 13 is attached to a connection cord 12 drawn out from the main body 1 including these. The drive unit 14 houses components called a ballast, such as a power switch SW, a filament heating transformer for a discharge lamp (not shown), a current limiting resistor, and the like.

Although this fluoroscopic device has a small number of discharge lamps, there is almost no unevenness in illumination, and
Since the back of the central part of this device is configured to be thinner than the conventional device, for example, the grooves 6 provided on both sides,
A digitizer or the like can be accommodated in the recess 15 shown by the imaginary line between 6 and 6. It is also suitable as a general desk-top or standing viewing-only fluoroscopic device because of its small thickness.

Although the fluoroscopic device developed by this earlier application has excellent features as mentioned above, it is lit with AC lighting, so depending on the length of the period of use, so-called flicker may occur, just like other fluoroscopic devices, causing eye strain to the user. Start giving. Furthermore, since images on film do not always have a constant density, there has been a demand for an easy-to-see fluoroscopic device that can increase or decrease the amount of light from a discharge lamp accordingly.

[Purpose of the invention] In view of the above points, this invention was made to improve the fluoroscopy device of the earlier application, and its purpose was to:
The object of the present invention is to provide a fluoroscopic device that inherits the structural features of the device of the prior application and is flicker-free and capable of adjusting the amount of light by lighting a discharge lamp with direct current using an electronic circuit including a semiconductor element. .

[Example] This invention will be explained in detail below with reference to an example shown in the accompanying drawings.

As shown in FIG. 1, this fluoroscopic device includes an apparatus main body 1, a drive section 14, etc., which have almost the same structure as the device of the prior application described above, and as shown in FIGS. 5 and 6.
The same reference numerals are given to parts corresponding to those in the figure, but in this invention, as shown in Fig. 2, for example, a rectifier Rec that converts an AC power supply V to a DC, A DC stabilizing circuit S, a discharge lamp ignition circuit A, its preheating circuit H, and a lighting current shunting circuit B are connected between the output terminals. In this embodiment, the ignition circuit A and the preheating circuit H are provided, for example, on the device main body 1 side, and the rectifier Rec, the DC stabilizing circuit S, and the lighting current shunting circuit B are provided in the drive section 14. Stored.

To explain the configuration of each of these parts, the DC stabilizing circuit S includes, for example, a rectifier output smoothing capacitor C of the rectifier Rec, a reference voltage forming circuit consisting of a resistor R ₁ and a Zener diode ZD ₁ , a transistor Q ₁ and a differential amplifier EA, etc. Constant current circuits, including diodes
It is equipped with a smoothing circuit consisting of _D1 , inductor L, and capacitor _C1 that also serves to remove spike voltage.

That is, a capacitor C is connected between the (+) and (-) terminals of the rectifier Rec, and both ends of a series circuit consisting of a resistor _R1 and a Zener diode _ZD1 are connected in parallel with the capacitor C. . In this case, one end of the resistor R ₁ is connected to the (+) terminal side, and the other end is connected to the Zener diode ZD ₁
This Zener diode is connected to the cathode of
The anode of ZD ₁ is connected to the above (-) terminal side.

Further, between the (+) terminals of the rectifier Rec, for example, the emitter of a transistor _Q1 is connected, and its base is connected to the output terminal of the differential amplifier EA. A load resistor RL is connected between the (-) input terminal and the output terminal of this differential amplifier EA, and
This (-) input terminal is connected to the cathode side of the Zener diode ZD ₁ and the (-) terminal side of the rectifier Rec through a resistor R ₂ and a variable resistor RV, respectively. Further, the (+) input terminal of this differential amplifier EA is connected to the (-) terminal side of the rectifier Rec through a resistor _R0 . Note that the collector of the transistor _Q1 is connected to, for example, one end of the inductor L and the cathode of the diode _D1 ,
The anode of the diode _D1 is connected to the (+) input end of the differential amplifier EA. Furthermore, the other end of the inductor L and the (+) of the differential amplifier EA are connected.
For example, a capacitor _C1 is connected to the input end side.

In this embodiment, two sets of the ignition circuit A and the preheating circuit H are shown having the same configuration for convenience, and one ignition circuit _A1 is connected to the inductor of the DC stabilizing circuit S, for example. An inductor CH whose one end is connected to the other end of L, and the other end of this inductor CH and the (+) of the above differential amplifier EA.
A discharge lamp FL ₁ is provided between the input terminal and the input terminal. One end of one filament f _{1 of this discharge lamp FL 1 is} connected to the other end of the inductor CH, and one end of the other filament f ₂ is connected to the (+) input terminal of the differential amplifier EA through a resistor R ₀ '. A capacitor C ₂ is connected between one end of the inductor CH and one end of the other filament f ₂ . Further, the other ends of the filaments f ₁ and f ₂ are each connected to one preheating circuit H ₁ . Note that both ends of the resistor R ₀ ' are connected to the lighting current shunting circuit B via the respective connection points.

The above preheating circuit H ₁ includes, for example, transistors Q ₂ and Q ₃
and Zener diode ZD ₂ , and capacitor C ₃
It consists of a charging circuit consisting of a resistor _R5 , and a charging circuit. That is, when a DC voltage is applied from the DC stabilizing circuit S, one transistor Q ₂ is turned on, and the filaments f ₁ and f ₂ of the discharge lamp FL ₁ are turned on.
The preheating current flows by closing the gap between the two. In this case, the other transistor _Q3 is turned off. When charging of the charging circuit consisting of capacitor C ₃ and resistor R ₅ progresses and reaches a predetermined voltage, the Zener diode ZD ₂
is activated, turning on the other transistor _Q3 , which turns one transistor off, cutting off the current path between the filaments _f1 and _f2 , and generating a high voltage pulse for ignition. In this case, if the time constant is set so that the Zener diode ZD ₂ is activated, for example, about 1 second after the start of charging, this fluoroscopy device will be released about 1 second after the power switch SW is closed. The light will turn on and be ready for use.

The other set of ignition circuit A ₂ and preheating circuit H ₂ are configured in the same manner as the one set of ignition circuit A ₁ and preheating circuit H ₁ as described above, and the above DC stabilizing circuit S
are connected in parallel to. In this case, a (+) voltage is applied from the DC stabilizing circuit S to the connection point between the capacitor C ₂ and the inductor CH and to the preheating circuit H ₂ .
The connection point between the capacitor C ₂ and the filament f ₂ of the discharge lamp FL ₂ is connected to the lighting current shunt circuit B via a connection point. Furthermore, in the other set of ignition circuits _A2 , a resistor corresponding to the resistor R ₀ ' of the above-mentioned ignition circuit _A1 is not provided because it is unnecessary.

The lighting current shunt circuit B includes the above two sets of ignition circuits.
This is to adjust the lighting current of the discharge lamps FL 1 and FL ₂ of A ₁ and _{A 2 to} a desired level, and detects the difference in the current flowing through the two amplifiers and the two discharge lamps. It consists of a differential amplifier that controls the input of the above amplifier, as well as transistors, diodes, resistors, and the like. That is, the (-) input terminal of the first stage amplifier BA ₁ is connected to the connection point between the capacitor C ₂ and the resistor R ₀ ' of the above-mentioned ignition circuit A ₁ via the resistor R ₈ , for example, and its (+) input The end is connected to the output end of the differential amplifier EA ₁ via a resistor R ₂₆ . Further, the output terminal of the amplifier BA ₁ is connected to the (-) input terminal of the next stage amplifier BA ₂ via a resistor R ₉ , for example. The (+) input terminal of this amplifier BA ₂ is connected to the resistor R ₀ of the DC stabilizing circuit S through the connection point, for example.
and R ₀ ′, and its output terminal is connected to a resistor.
Connected to the base of transistor _Q4 via _R10 . The collector of this transistor Q ₄ is connected, for example, to the connection point, and its emitter is connected to the resistor R ₂₁
It is connected to the above connection point via. Also,
Load resistors R ₁₁ and R ₁₂ are connected between the (-) input terminal and output terminal of these amplifiers BA ₁ and BA ₂ , respectively.

For example, voltage dividing resistors R ₁₇ , R ₁₈ and R ₂₂ , R ₂₃ are connected between the above connection point of the lighting current shunting circuit B and both ends of the resistor R ₂₁ , and a differential amplifier
The (-) input end of EA ₁ is connected to the above resistor via resistor _R27 .
Connected to the connection point of R ₁₇ and R ₁₈ . Also,
Its (+) input terminal is connected to the connection point between the resistors R ₂₂ and R ₂₃ , and a load resistor R ₂₈ is connected between the (-) input terminal and the output terminal.

Next, the basic operation of each circuit in this fluoroscopic apparatus configured as described above will be explained. When the power switch SW is closed and AC power is applied to the rectifier Rec, a DC voltage appears between its (+) and (-) terminals and is smoothed by the capacitor C. This DC voltage is applied across the series-connected resistor R ₁ and Zener diode ZD ₁ , the emitter of the transistor Q ₁ , and each part of the preheating circuits H ₁ and H ₂ .
First, the above Zener diode in the DC stabilizing circuit S.
ZD ₁ turns on.

This causes a resistance to be drawn from the (+) terminal of rectifier Rec.
R ₁ , through the Zener diode ZD ₁ to the rectifier Rec
Zener current flows to the (-) terminal of the
A voltage drop occurs across R ₁ and the Zener diode ZD ₁ . The voltage across this Zener diode ZD ₁ is extracted from its cathode side by being divided by a resistor R ₂ and a variable resistor RV, and is applied as a reference voltage to the (-) input terminal of the differential amplifier EA.

At this point, no current is flowing through the resistor R ₀ yet, so the (+) input terminal of the differential amplifier EA is at the same potential as the anode side of the Zener diode ZD ₁ , and the reference voltage is set at a predetermined resistance ratio ( RL／
_R2 ) and added to the base of transistor _Q1 . Therefore, the transistor _Q1 is turned on, and the voltage on the (+) side of the rectifier Rec is the same as that of the inductor L.
through the inductors of the ignition circuit A ₁ , A ₂ respectively
CH, CH, each filament f ₁ of discharge lamp FL ₁ and FL ₂ ,
f ₂ and the transistor Q ₂ in the preheating circuit H ₁ , H ₂ and
Applied to the collector of Q ₃ , the voltage on the (-) side of the rectifier Rec is applied to the transistor Q ₂ of the preheating circuit H ₁ through the resistor R ₀ and the resistor R ₀ ′ in the ignition circuit A ₁ and the filament f ₂ . Added to Emitsuta. In addition, the above (-) side voltages are branched through resistors R ₀ and R ₀ ', respectively, and the voltage branched through resistors R ₀ ' is sent from the connection point of lighting current shunt circuit B to the amplifier via resistor R ₈ . The voltage that can be applied to the (-) input terminal of BA ₁ and branched off via the resistor R ₀ is applied from the connection point to the (+) input terminals of amplifiers BA ₁ and BA ₂ and the emitter side of transistor Q ₄ .

As a result, in the preheating circuit _H1 , after the current path of the filaments _f1 and _f2 of the discharge lamp _FL1 is closed and the preheating current is passed as described above, the current path is turned off at a predetermined timing. The preheating current is cut off. Therefore, as is well known, a relatively high pulsed voltage is generated across the inductor CH. For example (+) of this pulsed voltage
The side voltage is applied directly to the filament f ₁ , (−)
The voltage on the side is passed through the capacitor C ₂ to the filament f ₂
is added and discharge lamp FL ₁ lights up.

When the discharge lamp FL ₁ is lit in this way, the lighting current flows through the resistors R ₀ ′ and R ₀ , and a voltage is generated between each terminal thereof. The above DC stabilizing circuit S
, the voltage across this resistor R ₀ is compared with the reference voltage provided by the Zener diode ZD ₁ and the difference voltage is applied to the base of the transistor Q ₁ via the differential amplifier EA. For example, if the load current such as the lighting current of the discharge lamp FL ₁ flows too much for some reason and the voltage across the resistor R ₀ becomes larger than the reference voltage, the minute difference between the reference voltage and the voltage across the resistor R ₀ is The dynamic amplifier EA detects this and turns off the transistor _Q1 with its amplified output. on the other hand,
A differential amplifier detects when the load current decreases and the voltage across the resistor becomes lower than the reference voltage.
Contrary to the above, the output of EA turns on transistor _Q1 to perform constant current operation. The spike-like voltage generated during this switching operation is short-circuited by diode _D1 , and the pulsating current is absorbed by inductor L and capacitor _C1 to smooth it out and obtain a stable constant current power supply. As can be understood from the above explanation, the preheating circuit H ₁ starts and a preheating current is supplied to both filaments f ₁ and f ₂ of the discharge lamp FL ₁ , and then the discharge lamp FL ₁ is ignited and the current for lighting is supplied. A substantially constant current is supplied from the rectifier Rec through the DC stabilizing circuit S over the entire period during which the current flows. Therefore, there is no need for circuit elements that cause large power loss, such as current-limiting resistors, which are found in conventional devices, and not only the efficiency of power usage is high, but there is no need to worry about heat generation or the like.

Next, to explain the operation of the lighting current shunting circuit B, in this circuit, the magnitude of the lighting current flowing to the discharge lamps FL ₁ and FL ₂ is equalized by the voltage generated across the resistor R ₀ '. Or control it to a desired different value. That is, let I ₀ be the constant current supplied through the transistor Q ₁ of the DC stabilizing circuit S, I ₁ be the lighting current of the discharge lamp FL ₁ , and let the lighting current I ₁ generate a current across the resistor R ₀ ′. The voltage V _{0 '} is amplified in two stages by amplifiers BA ₁ and BA ₂ and applied to the base of the transistor Q ₄ , turning on the transistor Q ₄ . Here, if the total gain of the amplifiers BA ₁ and BA ₂ is G, and the base voltage of the transistor Q ₄ is V _B , then V _B =G·V ₀ '.

As a result, the low potential side current path of the lighting current shunting circuit B is connected to the low potential side current paths of the ignition circuit A ₂ and preheating circuit H ₂ via the transistor Q ₄ and the connection point, and the ignition circuit A ₁ and preheating circuit H ₁ , the discharge lamp FL ₂ is lit. This discharge lamp
If the lighting current of FL ₂ is I ₂ , this current I ₂ passes through the connection point, transistor Q ₄ , from the connection point, through the resistance R ₀ of the DC stabilization circuit S, and flows into the (-) side terminal of the rectifier Rec. . Therefore, in this current path, the emitter current of the transistor _Q4 can be considered to be substantially equal to the lighting current _I2 of the discharge lamp _FL2 .

Here, as a basic operation, two lighting currents I ₁
To _{explain the} case _{of making} I _{2 equal} to It is possible to set. By the way, to give an example of setting the value of the resistor R ₀ ′, from the above V _B = G・V ₀ ′, V ₀ ′=V _B /G and V ₀ ′=I ₁・R ₀ ′ , R ₀ '=V ₀ '/I ₁ =V _B /(G·I ₁ ), the value of R ₀ ' can be found.

By setting the value of R ₀ ' in this way, the constant current I ₀ supplied from the DC stabilizing circuit S and the lighting current
It is easy to understand that the relationship I ₁ = I ₂ = I ₀ /2 holds between I ₁ and I ₂ .

In this example, the current I ₁ causes the resistance to
The voltage V ₀ ′ developed across R ₀ ′ is resistors R ₁₇ and R ₁₈
The voltage V ₂ that is applied to the (-) input terminal of the differential amplifier EA ₁ and generated across the resistor R ₂₁ by the current I ₂ is divided by the resistors R ₂₂ and R ₂₃ . and is applied to the (+) input terminal of the differential amplifier _EA1 . Also, the output of differential amplifier EA ₁ is applied to the (+) input terminal of amplifier BA ₁ , but if both currents I ₁ and I ₂ are equal, the output of differential amplifier EA ₁ is zero. The value of the voltage dividing resistor is set so that .

Here, if the lighting current I ₁ increases for some reason and becomes I ₁ > I ₂ , the voltage V ₀ ' across the resistor R ₀ ' increases, and the (-) voltage between the amplifier BA ₁ and the differential amplifier EA ₁ increases.
Since it is applied to the input terminal, the increment of the voltage V ₀ ' is magnified and applied between the (+) and (-) input terminals of the amplifier _BA1 . Therefore, the base voltage V _B of transistor Q ₄ also becomes larger. For this reason, the lighting current I ₂ also increases, but I ₁ + I ₂ = I ₀
Because of the constant current condition, I ₂ actually increases slightly and I ₁ decreases by that amount, and I ₁ and I ₂ cannot increase at the same time. Conversely, if I ₁ decreases too much, V ₀ ′ becomes small and the above base voltage V _B
decreases, and the lighting current _I2 decreases. This suppresses the decrease in I ₁ due to the above constant current condition, and ultimately the control is performed so that I ₁ ≈I ₂ . In other words, the differential amplifier EA ₁ detects even a slight difference in the magnitude of the currents I ₁ and I ₂ and uses its detection output to expand or reduce the input level of the amplifier BA ₁ in a positive feedback manner. Therefore, I ₁ = I ₂ with high precision
The base voltage of transistor _Q4 can be controlled so that

Next, a description will be given of the operation when adjusting the light amount of the discharge lamp depending on whether the density of the film used for fluoroscopy is high or low overall.

In this fluoroscopy device, as described above, the reference voltage divider circuit of the DC stabilizing circuit S has a variable resistor RV.
is used. It is easy to understand that adjusting the resistance value of this variable resistor RV changes the voltage division ratio and changes the level of the reference voltage applied to the (-) input terminal of the differential amplifier EA. Here, the divided reference voltage appearing across the resistor RV is Vr, the voltage appearing across the resistor _R0 due to the lighting current of the discharge lamp is _V0 , and for example, at time _t0 , the power switch SW is turned on. Then, as shown in FIG. 3A, the transistor _Q1 is turned on, and as shown in FIG. 3B, the current _I0 is output from the transistor _Q1 , as described in the explanation of the basic operation. In this case, the (-) input terminal of the differential amplifier EA has a constant level reference voltage Vr as shown in C.
is applied, and a voltage V ₀ that increases in proportion to the increase in the current I ₀ is applied to its (+) input terminal.
For example, when this voltage Vr and V ₀ become equal at time t, and V ₀ >V _r after time t, the amplified output of the differential amplifier EA cuts off the transistor Q ₁ , and the transistor Q ₁ is turned off as shown in FIG. 3 above. Perform the switching operation as shown in . For this reason, the output current I ₀ of _{the transistor Q 1 is} cut off as shown in FIG. As shown by the dotted line, the current I ₀ is almost constant.

Next, when the variable resistor RV is adjusted to lower its resistance value and the reference voltage is lowered from, for example, Vr to Vr' as shown in Figure 3C above, at time t'
V ₀ =Vr′. After this time t', V ₀ becomes >Vr', and the switching operation starts as shown by the two-dot chain line in FIG. 3A in the same manner as described above. The lighting current supplied to the discharge lamp decreases to approximately I ₀ ' after time t', as shown by the two-dot chain line in FIG.
Therefore, the voltage applied to the (+) input terminal of the differential amplifier EA also decreases from V ₀ to _{V 0} ″, as shown by the two-dot chain line in FIG.
This makes it possible to adjust the light amount of the discharge lamp.

Note that the load resistor RL of the differential amplifier EA may be removed and its open loop gain may be used to operate as a comparator. In this case, the waveforms of each part are the same as those shown in FIG. 3 above, but the rising and falling times of the switching operation of the transistor Q1 shown in FIG. _3A are faster.

FIG. 4 shows another embodiment in which the amount of light from the discharge lamp is automatically adjusted using a photosensor. This optical sensor is built into the probe 16, for example, and FIG. 1 above shows an example in which the probe 16 is placed on the top surface of the apparatus main body 1. According to this modified embodiment, a light-receiving phototransistor QL is used as the optical sensor, as shown in FIG. 4, for example, and its collector and emitter are respectively connected to both ends of the variable resistor RV. That is, phototransistor
The internal resistance of QL is added to the resistance of variable resistor RV. This phototransistor QL
If the base side, which is the light-receiving surface, is placed near the discharge lamp FL ₁ , for example, the light from the discharge lamp FL ₁ that passes through the film supplied to the fluoroscope will reach the base, and the size will change depending on the strength of the transmitted light. A photoelectric conversion current flows. In other words, the internal resistance of the phototransistor QL changes depending on the intensity of the light. As a result, the internal resistance of the phototransistor QL and the above variable resistance RV
The combined resistance changes, and this combined resistance and the above R ₂
The dividing ratio of the reference voltage changes. Therefore,
The level of the reference voltage applied to the (-) input terminal of the differential amplifier EA changes, and the same effect as when adjusting the light amount of the discharge lamp by manually operating the variable resistor RV can be obtained.

In addition, in the lighting current shunt circuit B of FIG.
Voltage dividing resistor R ₁₇ or R ₁₈ or voltage dividing resistor R ₂₂ or
It is also clear from the above description that when the resistance value of any one of R ₂₃ is made variable, the amount of light from the discharge lamp FL ₁ or FL ₂ increases or decreases, and no particular explanation is required.
Therefore, for example, if there is too much difference in shading between left and right images of one film, the amount of transmitted light can be easily partially adjusted.

Further, although two discharge lamps are used in this embodiment, the invention is not limited to that number. That is, if the light guide plate 10 has four inclined surfaces, four discharge lamps are required, whereas if the inclined surfaces are conical, one annular discharge lamp may be provided.

[Effects of the invention] As explained above in detail, the fluoroscopic device according to the invention includes a rectifier for converting AC power into DC, and a system for dividing the DC output of the rectifier to form a predetermined reference voltage. a first voltage dividing circuit having a voltage dividing ratio variable means; a first resistor for detecting the lighting current of one of the discharge lamps; a first comparator for comparing a reference voltage with a voltage generated at the first resistor; a DC stabilizing circuit including a first semiconductor switching element that controls the magnitude of the current supplied to one discharge lamp based on the output of the first comparator; and a current supplied from the DC stabilizing circuit to the other discharge lamp. a second semiconductor switching element that controls the magnitude of the discharge lamp; a second voltage dividing circuit that divides the voltage generated across the first resistor; a second resistor that detects the lighting current of the other discharge lamp; A lighting current comprising a third voltage divider circuit that divides the generated voltage, and a second comparator that compares the divided voltages from the second and third voltage divider circuits and controls the second semiconductor switching element with its output. The second and third voltage dividing circuits are set so that the voltages between the first and second resistors are equal when the lighting currents of the discharge lamps are equal;
The second comparator increases the lighting current of the other discharge lamp when each voltage ratio between the first and second resistors is smaller than the reference voltage, and lights the other discharge lamp when each voltage ratio is larger than the reference voltage. The second semiconductor switching element is controlled to reduce the current. Therefore, according to this fluoroscopic device, it is possible to supply a lighting current of approximately uniform magnitude to multiple discharge lamps, and to automatically control the lighting current when one lighting current differs from that of the other. It is possible to make the light intensity of all the discharge lamps substantially uniform by adjusting the amount of light. Furthermore, by adjusting the voltage dividing ratio variable means of the first voltage dividing circuit, the amount of light from the discharge lamp can be set to a desired brightness according to the density of the film image.
There is no flicker in the illumination light, and even if the film image has shading, appropriate transmitted light can always be obtained, and eye fatigue for fluoroscopy workers can be significantly reduced.

Furthermore, if one of the second and third voltage dividing circuits of the lighting current shunting circuit is configured with a variable resistor so that the voltage dividing resistance can be adjusted, it is possible to give different magnitudes of lighting current to each discharge lamp. It also allows partial dimming.

[Brief explanation of drawings]

1 to 4 all relate to an embodiment of the fluoroscopic device according to this invention, FIG. 1 is a perspective view of the main part including a partial cross section of the main body of the device, FIG. 2 is a circuit diagram thereof,
FIG. 3 is a timing diagram for explaining the operation, FIG. 4 is a circuit diagram when an optical sensor is applied, and FIGS. 5 and 6 are examples of conventional devices. In the figure, 1 is the main body of the fluoroscope, 5 is the translucent glass plate, 8, FL ₁ , 9, FL ₂ are discharge lamps, V is the AC power supply,
Rec is a rectifier, S is a DC stabilization circuit, R ₂ , R ₀ ,
R ₀ ′, R ₁₇ , R ₁₈ , R ₂₁ , R ₂₂ , R ₂₃ are resistors, RV is a variable resistor, EA, EA ₁ are amplifiers, Q ₁ , Q ₄ , QL are transistors, A ₁ , A ₂ are points The arc circuit, H ₁ and H ₂ are preheating circuits, and B is a lighting current shunting circuit.

Claims (1)

[Claims for Utility Model Registration] (1) In a fluoroscopic device that reads the image by illuminating the illumination light of at least two discharge lamps from the back side of a film placed on a semi-transparent diascopic plate, an AC power supply is provided. a rectifying means for converting the DC output into direct current; and a voltage division ratio variable means for dividing the DC output of the rectifying means to form a predetermined reference voltage.
a voltage dividing circuit, a first resistor that detects the lighting current of one of the discharge lamps, a first comparator that compares the reference voltage and the voltage generated at the first resistor;
a DC stabilizing circuit including a first semiconductor switching element that controls the magnitude of current supplied to the one discharge lamp based on the output of the first comparator; and a DC stabilizing circuit that supplies current to the other discharge lamp from the DC stabilizing circuit. a second semiconductor switching element that controls the magnitude of the current generated in the discharge lamp; a second voltage divider circuit that divides the voltage generated in the first resistor; and a second resistor that detects the lighting current of the other discharge lamp. , a third voltage divider circuit that divides the voltage generated in the second resistor, and the divided voltages from the second and third voltage divider circuits are compared, and the output of the third voltage divider circuit divides the voltage generated in the second resistor.
a lighting current shunting circuit including a second comparator for controlling a semiconductor switching element; The voltages between the resistors are set to be equal, and when the voltage ratio between the first and second resistors is smaller than the reference voltage, the second comparator reduces the lighting current of the other discharge lamp. and controlling the second semiconductor switching element to reduce the lighting current of the other discharge lamp when the respective voltage ratios are larger than the reference voltage. (2) Utility Model Registration The fluoroscopic device according to claim 1, characterized in that one of the second and third voltage dividing circuits is constituted by a variable resistor.