JPS63239410A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To correct the position shift of a light reception spot due to temperature variation and to perform accurate focusing over the entire temperature range by using a temperature sensing member as part of the holding member for the light reception part of an automatic focusing device, and shifting the position of the optical axis of the light reception part according to the temperature variation. CONSTITUTION:A light emitting element 2 is arranged opposite the projection lens 1 of a home video camera, a light receiving element 4 is arranged opposite a light reception lens 3, and the elements 2 and 4 are connected to an automatic focusing circuit 11. This light receiving element 4 is fitted to a substrate 15 fixed to a substrate holder 13 and the fitting position of the holder 13 is adjusted by an adjusting screw 12. Further, a bimetal 17 is fixed to the holder 13 with a screw 19 and an adjusting screw 14 is rotated to move and align the bimetal 17 coupled with the holder 13 with the optical axis of the lens 3 at room temper ature. Then the bimetal 17 corrects an error in distance measurement caused by the extension or contraction of a subject distance measuring mechanism part due to the temperature variation to stabilize the operation of the circuit 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an eye-based focusing device suitable for use in video cameras, etc.

? [Prior Art] In order to improve the operability of home-use video cameras, many of them are equipped with means for visually focusing on a subject. An example of such means is to measure the distance *1 to the subject, adjust the deviation 't'' of the focusing lens from the in-focus position, and drive the p focusing lens using a motor or the like based on this detection result. and move the focusing lens to the in-focus position.

By the way, as a means of measuring the distance to the subject, there are some methods such as those disclosed in Japanese Patent Publication No. 45-32747 and Japanese Patent Publication No. 46-2.
A method using light is known, as disclosed in Japanese Patent No. 850. In other words, such a means tS is equipped with a light emitting part made up of a projection lens and a light emitting element, and a light receiving part made up of a light receiving lens and a light receiving element, and a subject Kj is emitted from the light emitting part.
The distance to the subject is 5rL, the light receiving state KJ on the light receiving element, and the distance to the subject is 11! It is something that can be measured. In this case, the focusing lens is moved according to the state of reception of the reflected light by the first party element, but the state of reception of the reflected light by the receiving element differs depending on the distance to the subject. Special Publication No. 45-5274 that moves the light emitting part so that the state becomes a specific state
The focusing lens is moved in accordance with the movements of the following: Japanese Patent Publication No. 7 (Japanese Patent Publication No. 46-28500); Therefore, no matter what distance the subject is, when the focusing lens is positioned in the t state to focus on this object, the light receiving state at the light receiving element will be in the same specific state as above. The light-receiving element in is divided into two parts, and in this particular state,
The element of the light receiving spot received by each part of the light receiving element is divided into two parts Vr, and the elements of the light receiving spot are equal.Normally, the light receiving spot is circular.As shown in Fig. 5, the light receiving spot is divided into two parts. The light-receiving spots become even on the light-receiving spots, resulting in a rough state.

[Problem that the invention seeks to solve]

The above conventional technology does not take into account the following points: the environment in which the video camera is used, especially in areas exposed to direct sunlight in summer <aa''c or higher) or outdoor use in winter ( (below 0'C) K, no consideration is given to the occurrence of distance measurement errors in subject distance due to the eye movement focusing device.Distance measurement errors.

When the aperture of the photographic lens is narrowed down, the depth of field of the photographic lens is deep, and even if there is a distance measurement error, the subject remains in focus to some extent, but when the aperture is not apertured, Because the depth of field is shallow, it is difficult to focus on the outside subject, which causes a distance measurement error.

When using the camera at low temperatures, there was a delay in taking pictures with the eye movement focusing device activated.

The above problem is caused by the expansion and contraction of all constituent parts of the autofocus # due to temperature changes.

In particular, plastic parts are used to reduce weight and cost.
The coefficient of linear expansion of the plastic material is
The diameter is about twice as large as that of metal, and it expands and contracts greatly in response to temperature changes, which can cause distance measurement errors.

FIG. 4 schematically shows the inside of the object distance measuring section. 1 is a projection lens, and 2 is a light emitting element.

5 is a light-receiving lens, 4 is a light-receiving surface divided into two parts.
It is a two-part receiving element. Assume that you are currently measuring the distance to a subject and are focusing on the subject. In this state, the amount of reflected light from the object received by the two-split receiving element is uniformly incident on the two-part receiving element, resulting in a T-shape g1, ie, a state as shown in the fifth row. In this state, the holding member that holds the light receiving section and the projection section expands and contracts due to temperature changes. Therefore, the distance between the projection lens and the light-receiving lens @ C base line length, the distance between the light-receiving lens and the light-receiving element, the distance f between the projection lens and the light-emitting element, and the distance m between the light-receiving element and the light-emitting element expand and contract ``V'. For example, suppose that the distance m between the light emitting element and the light receiving element with respect to the original axis of the projection lens increases by 6 m due to temperature change.In this state, although the position of the light receiving spot entering the light receiving element remains constant, Because Δ?Pl− moves.

As shown in Fig. 6, the amount of light does not enter the two-split light-receiving element equally. Finally, there is a difference in the elements that hit the light-receiving element surfaces A and B. Therefore, even though the subject is in focus, the circuit determines that it is out of focus, as shown in Figure 5 above. In step 5, when the distance measurement is performed in the spot state, the focus state with the subject is lost and a distance measurement error occurs.If the base line length expands or contracts due to temperature changes, as in P1, the same as above. The following phenomenon occurs.Next, the distance between the light-receiving lens and the light-receiving element increases by 7t.
Consider the s combination. As shown in FIG. 7, the position of the light receiving element in the reference state is shown as being extended by Δ from the reference state due to temperature change. The direction of the chief ray of the receiving spot remains unchanged, C°′1 and C! The light receiving spot changes in and, and the light receiving spot status at each position is shown in the third column.-f.

At position C'1, it is in focus, but C! At the position , the light receiving element surface A is more than 10,000 (light receiving point j). Therefore, in the state of C1, the circuit determines that it is out of focus, and the direction that causes a distance measurement error even though the subject is in focus is determined by the circuit. As mentioned above, there is a problem in that the position of the members constituting the distance measuring section that measures the distance to the subject changes due to temperature changes, which causes inconvenience in the focusing operation.

[Means for solving problems]

The above purpose is to equalize the light intensity of the light receiving spot received by the two-split light receiving element on each light receiving element surface so that the state of focus judgment does not change even if the distance measuring unit components expand and contract due to temperature changes. In order to achieve this, a temperature-sensitive member such as a bimetal is used as a part of the RFS material of the light receiving part, and the light receiving part 1-
The configuration is such that the entire position of the sensor can be changed.

[Effect]

By configuring the bimetal so that the holding part that holds the receiver moves in a direction perpendicular to the light receiving axis and the projection source axis, the position of the light receiving spot due to temperature changes can be adjusted.
It operates to correct the By that, the entire temperature range of the disaster site? The focus is accurate.

〔Example〕

Below is an example of the present invention! This will be explained based on one factor.

FIG. 1 is a schematic configuration diagram showing an embodiment of an automatic focusing device according to the present invention.

1 is a projection lens, 2 is a light emitting element, 5 is a light receiving lens, and 4 is a light receiving element, and these constitute a subject distance measuring section. 5 is a flat plate, 6 is a lever connected to the flat plate 5, 7 is a lever 61C installed on a constant cam foot lower, 8 is a cam surface installed on the end face of the focus ring, 9 is a cam follower 71 on a cam surface 8. This is the tth elastic member that is brought into contact. The circuit section that constitutes the focusing mechanism from these K determines the focusing state based on the state of the amount of light received by the driving light receiving element 4 of the light emitting element 2, and the AF motor 10t? It is composed of an eye movement focusing circuit 11 that performs drive control. AF motor 10 to 9 focus '1J1
The gear 201i provided in 21 rotates and the focusing lens 2
2) is moved to -Cas Jl121 to arrow A7) times.

Focus on the subject.

FIG. 2 is a detailed diagram of the object distance measuring section and the focusing mechanism. The light receiving element 4 is soldered onto the substrate 15,
The board 15 is fixed to a board holder 16 with board fixing screws 16. Board holder 15! It is designed so that it can be adjusted using a companion adjustment screw 12 that corrects for variations in mounting position during assembly. The detailed structure of the adjustment screw portion will be explained in Section 5-.

The board holder 15 is attached to the case by a rotating screw 18. - The ten thousand adjustment screw 14 is attached to the GMU screw holder 12, and the AMP screw holder 12 is attached to the screw case.

-10,000 bimetal 17 pieces, board holder 15 & C screw 1
It is fixed at 9. Bimetal 17 kZ, 61 which can be functionally fixed even if it is fixed to the board holder by welding 9! By rotating the adjustment screw 14, the bimetal 17 connected to the substrate holder 15 is moved. The center can be adjusted in the direction of arrow C, and the light-receiving element 4 can be placed on the axis of the light-receiving lens 50 at room temperature; death,
Rotate the base and holder 13 in the direction of arrow C and position the light receiving element 4 at t? to be eaten.

(Thus, the expansion and contraction of the object ranging S component in this case is compensated for when the ambient temperature changes.

Next, we will quantitatively explain this movement. When plastic parts are used in the ratio configuration shown in Parts 1 and 2, the amount of thermal deformation is determined by calculations that differ depending on the shape material and molding conditions. It is difficult to do so. According to the experimental results, the shift of the light receiving spot for temperature changes from -10'C to 8506C is 1Q, cua ~
The amount of milk is 100μ, which varies depending on the shape, fixing position, and material of each component.

However, once the configuration is determined, there is almost no variation.

Next, we will consider the movement of bimetals. The deformation of the bimetal having the shape shown in FIG. 5 can be obtained from a linear equation.

ccrz curved thread a (1/ec, ) = 14.5X 1
0ΔS is the temperature difference (Co), L is the operating amount (?FL?FL), and D is the displacement amount (1
m) l is the thickness of the bimetallic plate (ttstn) [Effects of the Invention] According to the present invention, the expansion and contraction of the components of the subject distance measurement unit due to thermal corrosion will not cause distance measurement errors. As a result, it is practically stable over the entire temperature range.

This has the effect of providing a highly accurate automatic focusing device.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the automatic focusing device of the present invention, and FIG. 2 is a detailed diagram of the side lens portion and focusing mechanism according to the present invention.
Fig. 5 is a front view of the adjustment mechanism of the present invention, Fig. 4 is the S factor of the subject distance measuring section, Fig. 5 is a diagram showing the light receiving spot in the focused state, and Fig. 6 is a diagram showing the light receiving spot due to the movement of the light receiving element. FIG. 7 is a diagram showing the state and an explanatory diagram showing the light receiving state of the seventh pot. 1... Projection lens, 2... Light emitting element. 5... Light receiving lens, 4... Light receiving element. 15... Board holder, 14... Adjustment screw. 17...Bimeta A/. Katsunoshi Ogawa to Daiin 1 Figure 2 Figure 3 Figure 4 - En Figure 7 Kuzu 3

Claims (1)

[Scope of Claims] A light-emitting unit consisting of a projection optical system and a light-emitting element and projecting light onto a subject, and a light-receiving optical system and a light-receiving element receiving reflected light from the subject of the projection light projected onto the subject. A light receiving unit is provided, and a driving member that drives a holding member holding a focusing lens is controlled according to a light receiving state of the reflected light on the light receiving element in the light receiving unit, so as to focus on the subject. , a holder for holding the light-receiving element and an adjusting part for adjusting the light-receiving element to be positioned on the optical axis of the light-receiving optical system, and the holder and the adjusting part are joined to the holder and the adjusting part to make the holder and the adjusting part relative to each other when the temperature changes. An automatic focusing device consisting of a moving temperature-sensitive member.