JPH0441282Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a lens position detection device applied to detect a lens position in an automatic focusing device of a camera.

[Prior Art] An automatic focus adjustment device for a camera includes a switch means (for example, a sliding switch) whose contacts are opened and closed as the lens moves, and a counter that counts pulse signals formed by the switch means. The amount of movement of the lens from the initial setting point, that is, the movement position, is detected from the count value of this counter. Note that the detected position of the lens is compared with the target position calculated based on the ranging data, and when the two match, the movement of the lens is stopped.

By the way, the above-mentioned switch means is accompanied by so-called chattering when opening and closing, and this chattering causes the above-mentioned counter to miscount. Conventionally, as shown in FIG. 1, one terminal a and the other terminal b of the switching means 1 are connected to a set terminal and a reset terminal of an R-S flip-flop circuit 2, respectively, to eliminate the chattering from the flip-flop circuit. However, in this case, two signal lines are interposed between the flip-flop circuit 2, which is a chattering prevention circuit, and the switch means 1. Therefore, conventionally, two legs 4 and 5 are provided for connecting the switch means 1 to the integrated circuit 3 in which the flip-flop circuit 2 and the like are integrated, which increases the trouble of wiring the integrated circuit 3. This not only increases the cost of the integrated circuit 3, but also increases the cost of the integrated circuit 3.

[Purpose of the invention] In view of these conventional problems, the present invention attempts to provide a lens position detection device that requires only one signal line connected to the switch means.

[Configuration of the invention] The lens position detection device of the invention includes first and second electrodes connected to first and second power terminals supplied with first and second voltages, respectively, and a lens position detecting device that is connected to first and second electrodes that are connected to first and second power supply terminals, respectively, and to which the lens is moved. a switch means comprising a contact which alternately contacts said first and second electrodes and an output electrode which is brought into contact with said contact, each having one end connected to said first and second electrode; First and second switch elements, to which the output electrode of the switch means and the other ends of the first and second switch elements are connected, and the voltage level signal of the output electrode is used as a comparison input. selectively conducts one of the first and second switch elements so that when the contact element is not in contact, the input section retains the voltage before the non-contact time; It comprises circuit means and counting means for counting signals formed by changes in the output voltage of the circuit means.

In a preferred embodiment of the present invention, the first,
The second switch elements are each transistors;
The circuit means forward biases the base-emitter of the first switch element when the switch means outputs the first voltage, and when the switch means outputs the second voltage. The switch element is configured to apply a forward bias between the base and emitter of the second switch element when the contact element is in contact with the second switch element, and to provide a conduction condition to the switch element on the forward biased side when the contact element is not in contact with the second switch element. There is. Further, the first and second electrodes are disposed facing each other in a comb-teeth shape in a non-contact manner.

[Function] According to the above configuration, the contactor alternately contacts the first and second electrodes in the switch means, so that the first or second voltage is output to the output electrode. Then, the circuit means outputs a voltage corresponding to the output voltage of this switch means, and the counting means counts the change in the output voltage of this circuit means. Furthermore, when the contact element switches from the first electrode to the second electrode, when the contact element is in a non-contact state in which it does not touch any electrode, the first switch element is made conductive by the circuit means, and the input of the circuit means The part is held at the state before the non-contact state, that is, at the first voltage.
When the contact then contacts the second electrode, the output electrode is forced to switch to the second voltage. Thereafter, the input section of the circuit means is connected to the second switch element, regardless of whether the contact element is in contact with the second electrode or not, until the second switch element becomes conductive and the contact element contacts the first electrode again. 2 voltage state.

As described above, according to the present invention, once the contact has come into contact with one electrode, even if the contact is in a non-contact state, as long as the contact does not touch the other electrode, the circuit means Since the input section is configured so that the state does not change, it is possible to accurately count the number of times the first electrode and the second electrode are switched, regardless of the chatter of the contact. Moreover, the output electrode of the switch means and the circuit means can be connected with one line.

[Description of Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

The lens position detection device according to the present invention has a sliding switch 10 as shown in an embodiment in FIG.
, a chattering prevention circuit 20, and a counter 30.
It is made up of.

The sliding switch 10 includes first and second electrodes 11 and 12 formed in a comb shape, an output electrode 13 arranged in parallel with these electrodes to function as an output terminal, and a U-shaped contactor. (slider) 14. The electrodes 11 and 12 are arranged in a balanced manner such that their comb teeth engage with each other in a non-contact manner. The electrode 11 is connected via a resistor 15 to one power supply terminal T1 to which voltage Vcc is applied, and the electrode 12 is connected to the other power supply terminal T2 which is grounded. Further, the contactor 14 has one contact piece 1
4a is located on a line connecting the comb-like pieces of the electrodes 11 and 12, and the other contact piece 14b is located on the longitudinal axis of the output electrode 13. This contact 14
is moved in the direction of the arrow as the lens of a camera (not shown) moves, and when the lens is located at the initial setting point, it is placed at the position shown in the figure. Note that the resistor 15 is provided to prevent an excessive short-circuit current from flowing when the electrodes 11 and 12 are short-circuited by the contactor 14, and in this embodiment, its value is set to about 1KΩ. has been done.

Further, each of the electrodes 11, 12 and 13 is formed as a printed pattern on the substrate.

The chattering prevention circuit 20 includes the electrode 1
3, two comparison circuits 21 and 22 consisting of operational amplifiers, a PNP type transistor 23, and an NPN type transistor 24.

The comparison circuits 21 and 22 each have an inverting input terminal connected to the input terminal T3 via a compared voltage input line 25, and each non-inverting input terminal is a constant voltage circuit consisting of a constant current source 26 and a resistor 27. It is connected to the. The output terminal of the comparison circuit 22 is connected to the counter 30. On the other hand, the transistor 23 has its emitter connected to the power supply terminal T1.
, the collector is connected to the line 25 through the resistor 28.
Furthermore, the base is connected to the above comparison circuit 2 via a resistor.
1 output terminal. Further, the transistor 24 has its emitter connected to the power supply terminal T2.
, the collector is connected to the line 25 through the resistor 29.
Furthermore, their bases are each connected to the output terminal of the comparator circuit 22 via a resistor.

The resistors 28 and 29 are each connected to the transistor 2
This is provided to limit the current flowing through the resistors 3 and 24, and in this embodiment, the value is set to about 10KΩ. Also, the reference voltage Vref applied to each non-inverting input terminal of the comparison circuits 21 and 22
is set to about 1/2Vcc. Further, the chattering prevention circuit 20 and the counter 30 are integrated in the same package together with other circuit elements (not shown).

The operation of this embodiment is as follows.

When the contactor 14 is moved in the direction of the arrow as the lens moves and contacts the electrodes 11 and 12 alternately, a signal with chattering as shown in FIG. 3a appears at the output terminal 13. That is, when the contactor 14 is in contact with the electrode 11, the voltage Vcc
is also in contact with electrode 12, a voltage O appears at each of said electrodes 13, while electrodes 11, 12
When the contact 14 passes through the gap between the two, the contact 14 is placed in a non-contact state and an unstable contact state, so that chattering as shown in the figure occurs.

However, according to this embodiment, the above-mentioned chattering can be completely eliminated. That is, when the contactor 14 is now in the position shown in FIG. 2, where it is in contact with the electrode 12, the inverting input terminals of the comparator circuits 21 and 22 are both set to the ground level (<Vref), and the output is output from them. Both voltage levels become "H", and as a result, the base and emitter of transistor 24 are biased in the forward direction, and the base and emitter of transistor 23 is biased at zero. Here, even if the contactor 14 moves from above the electrode 12 to the gap part and becomes in a non-contact state, the transistor 24 remains conductive through the components of the comparison circuits 21 and 22, and the transistor 23 remains conductive. Since the line 25 is in a non-conductive state, the line 25 is set to approximately the ground level, and therefore the output terminals of the comparator circuits 21 and 22 maintain the "H" level. When the contactor 14 passes through the gap and contacts the electrode 11, R ₁ Vcc/(R ₁ + R ₂ )=10K/(10K+1K) ×Vcc>Vref However, R ₁ is the resistance value of the resistor 29, for example, 10KΩ. , R ₂ : Resistance value of resistor 15, for example 1KΩ, Vcc : Power supply voltage, output terminals of comparison circuits 21 and 22 are “L”
As a result, the base and emitter of transistor 23 is biased in the forward direction, and the base and emitter of transistor 24 is biased at zero. Therefore, when the contactor 14 that has once contacted the electrode 11 is brought into a non-contact state due to vibration or the like, the transistor 23 becomes conductive and the line 25 is brought to approximately the Vcc level, thereby causing the above-mentioned The output terminals of comparison circuits 21 and 22 maintain the "L" level.

When the contactor 14 moves from the electrode 11 to the electrode 12, the chattering prevention circuit 2
0 has the opposite effect to that described above, so that the comparator circuits 21 and 22 output a signal without chattering as shown in FIG. 3b. Therefore, the output signal of the comparator circuit 22 is input, and the counter 30 accurately measures the moving position of the lens.

[Effects of the invention] As is clear from the operation of the embodiments described above, according to the invention, only one signal line is required to be connected to the switch means, so that the circuit elements receiving the output signal of the switch means can be integrated. In this case, the number of integrated circuits can be reduced compared to the conventional one, thereby reducing the manufacturing cost of the circuit and facilitating wiring for the circuit.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of a chattering prevention circuit applied to a conventional lens position detection device, and FIG. 2 is a circuit diagram showing an example of a lens position detection device according to the present invention. 3a and 3b are waveform diagrams showing the input waveform and output waveform of the chattering prevention circuit shown in FIG. 2, respectively. 10...Sliding switch, 11,12...Electrode,
13... Output electrode, 14... Contact, 20...
Chattering prevention circuit, 21, 22... Comparison circuit, 23, 24... Switching transistor,
30...Counter.

Claims (1)

[Claims for Utility Model Registration] 1. First and second electrodes connected to first and second power supply terminals supplied with first and second voltages, respectively;
A switch comprising a contact that alternately contacts the first and second electrodes in a non-contact state according to the movement of the lens, and an output electrode that is brought into contact with the contact. means, first and second switch elements each having one end connected to the first and second electrodes; an output electrode of the switch means and an output electrode of the first and second switch elements connected to the input portion thereof; The other end is connected, and the voltage level signal of the output electrode is used as a comparison input to output a corresponding voltage level signal. circuit means for selectively conducting one of the first and second switch elements so that substantially the same voltage as before contact is maintained; and a change in the output voltage of the circuit means. A lens position detection device comprising a counting means for counting signals. 2. The first and second switch elements are each a transistor, and the circuit means forwardly connects the base and emitter of the first switch element when the switch means outputs the first voltage. bias, and said switch means said second
When outputting a voltage of A lens position detecting device according to claim 1, which is configured to provide a lens position detecting device. 3. The lens position detection device according to claim 1 or 2, wherein the first and second electrodes are disposed facing each other in a comb-teeth shape in a non-contact manner.