Summary of the invention
In view of foregoing, be necessary to provide a kind of optical filter changeover module control circuit of judging unusually.
A kind of optical filter changeover module control circuit; Comprise a photoresistance, one first resistance, first to the 6th electronic switch, a voltage source, an optical filter changeover module, a comparer and a central processing unit; This first resistance and this photoresistance are connected between this voltage source and the ground; Node between this first resistance and this photoresistance is connected to this second and third electronic switch through this first electronic switch and also is connected to this central processing unit; This second electronic switch is connected to the 4th and the 5th electronic switch; The 3rd and quadrielectron switch between the node of node and the 5th and the 6th electronic switch be connected to two input ends of this optical filter changeover module respectively and be connected to the in-phase input end and the inverting input of this comparer respectively; The output terminal of this comparer is connected to this central processing unit; This first electronic switch is according to the resistance change switched conductive state of this photoresistance; And then switch the conducting state of this second to the 6th electronic switch, so that the corresponding voltage difference of switching between these optical filter changeover module two input ends, this central processing unit judges according to the signal of this first electronic switch input and the signal of this comparer input whether the switching of this optical filter changeover module is correct.
Compare prior art; Optical filter changeover module control circuit of the present invention reads the signal of this first electronic switch input and reads the signal of this comparer input through this central processing unit; Can judge this optical filter changeover module through this two signal relatively and whether make correct switching, very convenient.
Embodiment
Please refer to Fig. 1; Optical filter changeover module control circuit 100 of the present invention is used to eliminate the colour cast that infrared light sources on the video camera produces, and its preferred embodiments comprises a photoresistance RT, six resistance R 1-R6, two NPN transistor Q1 and Q2, two P-channel field-effect transistor (PEFT) transistor Q3 and Q5, two N slot field-effect transistor Q4 and Q6, four diode D1-D4, a voltage source Vcc, an optical filter changeover module U1, a comparer U2, a central processing unit (CPU) U3.Wherein, the resistance value of this photoresistance RT reduces with the rising of light luminance, and increases with the decline of light luminance, and other embodiment also can be opposite.This optical filter changeover module U1 carries out the switching of common optical filter and infrared filter through changing voltage difference between its two input end, and concrete principle of work is a prior art, no longer specify here.This central processing unit U3 is the inner main processing assembly of video camera, and it also is responsible for such as tasks such as photographies, does not also remake to specify here.
This resistance R 1 and this photoresistance RT are connected between this voltage source Vcc and the ground; Node between this resistance R 1 and this photoresistance RT is connected to the base stage of this transistor Q1 through resistance R 2; The grounded emitter of this transistor Q1, the collector of this transistor Q1 through resistance R 3 be connected to this voltage source Vcc, through resistance R 4 be connected to this transistor Q2 base stage, through resistance R 5 be connected to this two field effect transistors Q3 and Q4 grid, be connected to this central processing unit U3.The grounded emitter of this transistor Q2, collector are connected to this voltage source Vcc through resistance R 6 and also are connected to the grid of this two field effect transistors Q5 and Q6.
The drain electrode of this two field effect transistors Q3 and Q5 is connected to this voltage source Vcc, and the source electrode of this two field effect transistors Q3 and Q5 is connected to the drain electrode of this two field effect transistors Q4 and Q6 respectively.The source grounding of this two field effect transistors Q4 and Q6.The anode of this diode D1-D4 and negative electrode are connected to source electrode and the drain electrode of this field effect transistor Q3-Q6 respectively, and this diode D1-D4 is used to protect this field effect transistor Q3-Q6, also can delete as required.Two voltage input ends of this optical filter changeover module U1 are connected to node and the node between this two field effect transistors Q5 and the Q6 between this two field effect transistors Q3 and the Q4 respectively.Two voltage input ends of this optical filter changeover module U1 also are connected to in-phase input end and the inverting input of this comparer U2 respectively.The voltage end of this comparer U2 is connected to this voltage source Vcc, earth terminal ground connection, and output terminal is connected to this central processing unit U3.In other embodiment, this two transistor Q1 and Q2, this field effect transistor Q3-Q6 also can select the electronic switch of other type for use.
During work, this transistor Q1 conducting state is by the resistance value decision of this photoresistance RT, when extraneous light luminance is elevated to a certain setting value; The resistance value correspondence of this photoresistance RT drops to a certain setting value, and this moment, this transistor Q1 ended, and then the collector of this transistor Q1 becomes high level; This central processing unit U3 receives this high level signal; So this transistor Q2 conducting, and then this two field effect transistors Q4 and Q5 conducting, and this two field effect transistors Q3 and Q6 end; This moment, the in-phase input end of this comparer U2 was a low level; And inverting input is a high level, and this optical filter changeover module U1 switches to common optical filter, and the output terminal output low level of this comparer U2 is given this central processing unit U3.
In like manner, when extraneous light luminance dropped to this setting value, the resistance value correspondence of this photoresistance RT rose to this definite value; This transistor Q1 conducting this moment, and then the collector of this transistor Q1 becomes low level, this central processing unit U3 receives this low level signal; So this transistor Q2 ends, and then this two field effect transistors Q4 and Q5 end, and this two field effect transistors Q3 and Q6 conducting; This moment, the in-phase input end of this comparer U2 was a high level; And inverting input is a low level, and this optical filter changeover module U1 switches to infrared filter, and the output terminal output high level of this comparer U2 is given this central processing unit U3.
This central processing unit U3 intersects comparison through the signal to the signal of the collector of this transistor Q1 of reading and the output terminal of this comparer U2 and judges whether this optical filter changeover module U1 has carried out correct switching.See also following table:
The Q1 collector |
The U2 output terminal |
The RT resistance value |
The U1 state |
U3 judges |
0 |
1 |
>Rm |
Just change |
Normally |
1 |
0 |
<Rm |
Counter-rotating |
Normally |
0 |
0 |
-- |
-- |
Unusually |
1 |
1 |
-- |
-- |
Unusually |
Wherein, Last table " 1 " is represented high level, and low level is represented in " 0 ", and " Rm " represents the setting value of this photoresistance RT; " just change " and represent this optical filter changeover module U1 to switch to infrared filter, on behalf of this optical filter changeover module U1, " counter-rotating " switch to common optical filter.This central processing unit U3 can judge this optical filter changeover module U1 after according to the comparison of last table and whether make correct switching, making subsequent operation according to judged result, as occurs unusually, sends prompt tone to inform the user, and is like that.This shows whether correct, improved the shooting quality if using the switching that optical filter changeover module control circuit 100 of the present invention can judge optical filter effectively.