We present nine color CCD intermediate-band spectrophotometry of a two square degree field centered on the old open cluster M67 , from 3890 \AA to nearly 1 \mu .
These observations are taken as a part of the BATC ( Beijing-Arizona-Taipei-Connecticut ) Color Survey of the Sky , for both scientific and calibration reasons .
The BATC program uses a dedicated 60/90 cm Schmidt telescope with a 2048 \times 2048 CCD and 15 specially-designed intermediate-band filters to be applied to both galactic and extragalactic studies .

With these data we show that the BATC survey can reach its goal of obtaining spectrophotometry to a zero point accuracy of 0.01 mag , and down to V = 21 with 0.3 mag random error .
Nine-band spectrophotometry of 6558 stars is presented .
Systematic issues studied include the effect of image undersampling , astrometric accuracy and transformation from BATC photometric system to broad-band systems .

We fit the color-magnitude diagrams ( CMDs ) with Worthey ’ s theoretical models .
The net result is the excellent fit of the 4.0 Gyr , [ Fe/H ] = -0.10 model to our data , including a good fit to the main sequence ( MS ) turn-off .
This fit predicts ( m - M ) _ { 0 } = 9.47 \pm 0.16 and E ( B–V ) between 0.015 and 0.052 .
We show that 16 % of stars in M67 are binaries with mass-ratio larger than 0.7 .
Our data are consistent with a toy model with 50 % of the stars in M67 being binaries and a random distribution of binary mass-ratios , although other models with different mass-ratio distributions can not be ruled out .

The spatial distribution and mass function ( MF ) of stars in M67 show marked effects of dynamical evolution and evaporation of stars from the cluster .
Blue stragglers and binary stars are the most condensed within the cluster , with degree of condensation depending on mass .
The inner part of M67 is missing most of the lower mass MS stars .
We find M67 to have an elongated shape , oriented at an angle of 15 ^ { \circ } relative to the galactic plane .

Within its tidal radius , the observed MF of M67 between 1.2 M _ { \odot } and 0.8 M _ { \odot } has a Salpeter slope \eta = -1.93 \pm 0.66 .
For stars of mass below 0.8 M _ { \odot } , \eta \sim 0 .
It is plausible that the leveling-off of the MF at lower masses is a result of evaporation of lower mass stars in this mass range at a rate of one every \sim 10 ^ { 7 } years .
If so , it is plausible that the IMF of M67 has the canonical field value of \eta = -2.0 .

Overall , we find the stellar distribution as a function of mass within M67 , and the observed MF , are in good agreement with theoretical predictions of dynamical evolution and evaporation of an old galactic cluster .
Moreover , the fraction of binary stars and inferred IMF for higher mass main sequence stars for this old galactic cluster are consistent with known field star values .
This implies a similarity of IMF that persists for at least 4 Gyr in the disk of our Galaxy .

\keywords clusters : galactic — clusters , individual : M67 — stellar dynamics — initial mass function